Perspectives in Marine Biology

This title is part of UC Press's Voices Revived program, which commemorates University of California Press’s mission to seek out and cultivate the brightest minds and give them voice, reach, and impact. Drawing on a backlist dating to 1893, Voices Revived makes high-quality, peer-reviewed scholarship accessible once again using print-on-demand technology. This title was originally published in 1958.

• Language: English
• Publisher: University of California Press
• Release date: Dec 22, 2023
• ISBN: 9780520350281

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PERSPECTIVES IN MARINE BIOLOGY

A SYMPOSIUM

HELD AT SCRIPPS INSTITUTION OF OCEANOGRAPHY

UNIVERSITY OF CALIFORNIA

MARCH 24-APRIL 2, 1956

PERSPECTIVES

IN MARINE BIOLOGY

EDITED BY

A. A. BUZZ ATI — TR AVERSO

19 5 8 UNIVERSITY OF CALIFORNIA PRESS BERKELEY AND LOS ANGELES

University of California Press

Berkeley and Los Angeles, California

Cambridge University Press

London, England

O 1958 by The Regents of the University of California Library of Congress Catalog Card Number: 58-6521 Manufactured in the United States of America

PREFACE

The present volume consists of the papers presented at the symposium on Perspectives in Marine Biology held at the Scripps Institution of Oceanography of the University of California, March 24-April 2, 1956. The symposium, which was conducted under the auspices of the International Union of Biological Sciences and sponsored jointly by the Office of Naval Research and the Scripps Institution of Oceanography, was prompted by the expansion in biological research at the La Jolla campus of the University of California made possible by a large grant received from the Rockefeller Foundation.

As a result of discussions among members of the staff of the Scripps Institution as well as with other colleagues, the conclusion was reached that at the present stage of development of marine biology it is worthwhile to discuss areas of investigation that could be most profitably attacked at the experimental level. We thought that the sweeping advances that other fields of biology have made, and the ensuing great progress we have witnessed in medicine and agriculture, are primarily a consequence of the experimental approach that has distinguished most branches of terrestrial biology. We felt confident that the time was ripe for a broad, frontal attack on the problems of marine biology thanks to our greater familiarity with the sea, to the development of new tools and theoretical approaches, and to the deeper insight into general biological problems obtained by biochemists, biophysicists, geneticists, and microbiologists. The symposium was held, therefore, in order to permit a discussion focused on possible forthcoming fields of development in marine biology rather than on a survey of past accomplishments. We, accordingly, invited to La Jolla a number of marine and nonmarine biologists to explore problems within the limits of marine life that are ready for experimental attack and to outline definite plans for research.

The discussions following the presentation of the papers are here recorded according to the written contributions of the participants in the symposium. At the end of the volume a summary is presented of the most significant ideas and plans for research that were discussed during the conference.

The Editor

PARTICIPANTS

Ahl Strom, Elbert H.

U.S. Fish and Wildlife Service Scripps Institution of Oceanography La Jolla, California

Allen, Mary Belle

Dept, of Plant Nutrition

University of California

Berkeley 4, California

Angot, Michel

LATTC Fellow

Scripps Institution of Oceanography

La Jolla, California

Anig stein, Ludwig

Medical School

University of Texas

Galveston, Texas

Arnon, D. I.

College of Agriculture

Dept, of Soils and Plant Nutrition

University of California

Berkeley 4, California

Arrhenius, Gustaf O.

Dept, of Chemical Oceanography

Scripps Institution of Oceanography La Jolla, California

Ar-rushdi, Abbas H.

Dept, of Marine Genetics (Fellow) Scripps Institution of Oceanography La Jolla, California

Arthur, David K.

Dept, of Marine Invertebrates

Scripps Institution of Oceanography La Jolla, California

Baldwin, Ernest

University College

Gower St., W.C.I.

London, England

Barigozzi, Claudio

Istituto di Genetica

Via Celoria 10

Milano, Italy

Barnes, Harold

Marine Biological Station

Millport, Isle of Cumbrae

Scotland

Bean, R. C.

University of California

Riverside, California

Belser, William

USPH Fellow

Scripps Institution of Oceanography

La Jolla, California

Bennett, Rawson, II

Chief, Office of Naval Research

Navy Department

Washington 25, D.C.

Berner, Leo D.

Dept, of Marine Invertebrates

Scripps Institution of Oceanography La Jolla, California

Bernhard, Michael

Dept, of Marine Genetics (Fellow) Scripps Institution of Oceanography La Jolla, California

Blinks, Lawrence R.

Hopkins Marine Station

Pacific Grove, California

Boden, Elizabeth M.

Dept, of Marine Invertebrates Scripps Institution of Oceanography La Jolla, California

Boden, Brian P.

Dept, of Marine Invertebrates Scripps Institution of Oceanography La Jolla, California

Bolin, Rolf

Hopkins Marine Station

Pacific Grove, California

Bolton, V.

Office of Naval Research

Navy Department

Washington 25, D.C.

Bookhout, C. G.

Hopkins Marine Station

Pacific Grove, California Bradshaw, John S.

Foraminifera Laboratory

Scripps Institution of Oceanography La Jolla, California

Brinton, Edward

Dept, of Marine Invertebrates

Scripps Institution of Oceanography La Jolla, California

Broch, V.

Territorial Fish and Game Dept.

of Hawaii

Honolulu, T.H.

Brown, Frank A., Jr.

Dept, of Biological Sciences

Northwestern University

Evanston, Illinois

Buchsbaum, Ralph

Dept, of Biological Sciences

University of Pittsburgh

Pittsburgh, Pennsylvania

Buzzati-Traver so, A. A.

Dept, of Marine Genetics

Scripps Institution of Oceanography

La Jolla, California

Bullock, T. H.

Dept, of Zoology

University of California

Los Angeles 24, California

Car ritt, Dayton

Dept, of Oceanography

The Johns Hopkins University

Baltimore 18, Maryland

Caspers, H.

Zoologisches Staatsinstitut

Hamburg 13, Bornplatz 5

Germany

Coker, R. E.

Inst, of Marine Biology and

Zoological Garden

University of Puerto Rico

Mayaguez, Puerto Rico

Collier, Jack

California Institute of Technology

Pasadena, California

Contois, David E.

Dept, of Marine Microbiology

Scripps Institution of Oceanography

La Jolla, California

Corcoran, Eugene F.

Dept, of Marine Biochemistry

Scripps Institution of Oceanography

La Jolla, California

Cromwell, Townsend

Inter-Ame ri can Tropical Tuna

Commis sion

Scripps Institution of Oceanography

La Jolla, California

Cushing, John

Dept, of Biological Sciences

University of California

Santa Barbara College

Goleta, California

Daiber, Franklin C.

Dept, of Biological Sciences

University of Delaware

Newark, Delaware

Davenport, D.

Dept, of Zoology

University of California

Santa Barbara College

Goleta, California

De Buen, Fernando

General de Pescas Industrias

Conexas

Secretaria de Marina

Calle Azveta 9

Mexico, D.F.

Della Croce, Norberto

Dept, of Zoology

University of Wisconsin

Madison 6, Wisconsin

Dietz, Robert S.

Office of Naval Research

Box 39, Navy 100, Fleet P.O.

New York, New York

Dodge, Eleanor

Dept, of Zoology

University of Washington

Seattle 5, Washington

Dohrn, P.

Stazione Zoologica

Napoli, Italy

Drach, Pierre

Laboratoire de Zoologie

Faculte des Sciences

Université de Paris

Paris, France

Dudley, Patricia

Dept, of Zoology

University of Washington

Seattle 5, Washington

Duntley, Seibert Q.

Director, Visibility Laboratory

Scripps Institution of Oceanography

La Jolla, California

Ebling, Alfred W.

Dept, of Marine Vertebrates

Scripps Institution of Oceanography

La Jolla, California

Ewing, Gifford C.

Oceanography, Waves, and

Currents

Scripps Institution of Oceanography

La Jolla, California

Fager, Edward W.

Dept, of Marine Invertebrates

(Fellow)

Scripps Institution of Oceanography La Jolla, California

Fish, Marie P.

Narragansett Marine LaboratoryUniversity of Rhode Island Kingston, Rhode Island

Flechsig, Arthur O.

Dept, of Marine Vertebrates

Scripps Institution of Oceanography La Jolla, California

Foerster, R. E.

Biological Station

Nanaimo, B.C.

Canada

Fox, Denis L.

Dept, of Marine Biochemistry Scripps Institution of Oceanography La Jolla, California

Fox, Sidney W.

Oceanographic Institute

Florida State University Tallahassee, Florida

Fukuda, Y.

Ministry of Agriculture and Fi sheries

Tokyo, Japan

Galler, S. R.

Head, Biology Branch

Office of Naval Research Washington 25, D.C.

Ghelardi, Raymond

Student

Scripps Institution of Oceanography La Jolla, California

Gilmore, Raymond M.

U.S. Fish and Wildlife Service

La Jolla, California

Goldberg, Edward D.

Chemical Oceanography

Scripps Institution of Oceanography La Jolla, California

Gooding, R. U.

Dept, of Zoology

University of Washington

Seattle 5, Washington

Guzman Barron, E. S.

Dept, of Medicine

University of Chicago

Chicago 37, Illinois

Hafiz, H. A.

3107 Third Avenue

San Diego, California

Hand, Cadet

Dept, of Zoology

University of California

Berkeley 4, California

Hardy, A. C.

Dept, of Zoology

Oxford University

Oxford, England

Hartman, Olga

Allan Hancock Foundation

University of Southern California

Los Angeles 7, California

Harvey, George W.

Dept, of Marine Genetics

Scripps Institution of Oceanography

La Jolla, California

Hasler, A. D.

Dept, of Zoology

University of Wisconsin

Madison, Wisconsin

Haxo, Francis T.

Dept, of Marine Botany

Scripps Institution of Oceanography

La Jolla, California

Hayes, Helen

Biology Branch

Office of Naval Research

Washington 25, D.C.

Hedgpeth, Joel W.

Dept, of General Instruction and Research

Scripps Institution of Oceanography

La Jolla, California

Hiatt, Robert

University of Hawaii

Honolulu, T.H.

Hirata, A.

University of California

Los Angeles 24, California

Holmes, Robert W.

Dept, of Marine Botany

Scripps Institution of Oceanography

La Jolla, California

Hommer sand, Max

Dept, of Botany

University of California

Berkeley 4, California

Howard, G.

Inter-American Tropical Tuna Commission

San Diego, California

Horvath, C.

Dept, of Biology

University of Southern California

Los Angeles 7, California

Hubbs, Carl L.

Dept, of Marine Invertebrates

Scripps Institution of Oceanography

La Jolla, California

Huttrer, Charles P.

Dept, of Health, Education, and Welfare

Public Health Service

National Institute of Health

Bethesda 12, Maryland

Inman, Douglas L.

Dept, of Shore Processes

Scripps Institution of Oceanography- La Jolla, California

Isaacs, John D.

Dept, of Physical Oceanography

Scripps Institution of Oceanography La Jolla, California

Jaffe, Lionel F.

Dept, of Marine Genetics (Fellow)

Scripps Institution of Oceanography- La Jolla, California

Johnson, F. H.

Princeton University

Princeton, New Jersey

Johnson, Martin W.

Dept, of Marine Invertebrates Scripps Institution of Oceanography La Jolla, California

Jones, Galen E.

Dept, of Marine Microbiology

Scripps Institution of Oceanography La Jolla, California

Kamemoto, Fred L.

CW Labs. Bio-assay Division

Dugway Proving Ground

Dugway, Utah

Kan wisher, John

Woods Hole Oceanographic Inst.

Woods Hole, Massachusetts

Kelley, Arthur L.

Dept, of Marine Biochemistry Scripps Institution of Oceanography La Jolla, California

Ke steven, G. L.

Food and Agriculture Organization of the U.N.

Viale delle Terme di Caracalla

Rome, Italy

Ketchum, B. H.

Woods Hole Marine Biological

Laboratory

Woods Hole, Massachusetts

Kittredge, James S.

Dept, of Marine Biochemistry Scripps Institution of Oceanography La Jolla, California

Kohn, Alan J.

Hawaiian Marine Laboratory

University of Hawaii

Honolulu 14, Hawaii

Kon, S. K.

National Institute for Research

in Dairying

Shinfield, Reading, England

Kozloff, Eugene

Lewis and Clark College

0615 S. W. Palatine Hill Road

Portland 1, Oregon

Kubitschek, Herbert E.

Division of Biological and Medical Research

Argonne National Laboratory, Box 299

Lamont, Illinois

Lane, C. E.

University of Miami

Coral Gables 34, Florida

Lasker, Reuben

Dept, of Biological Sciences

Stanford University

Stanford, California

Laties, George

Division of Biology

California Institute of Technology

Pasadena, California

Lear, Donald W.

Dept, of Marine Microbiology

Scripps Institution of Oceanography

La Jolla, California

Leipper, Dale

Dept, of Oceanography

Texas A. and M. College

College Station, Texas

Lewin, Joyce

Scripps Institution of Oceanography

La Jolla, California

Lewin, R. A.

Scripps Institution of Oceanography

University of California

La Jolla, California

Limbaugh, Conrad

Marine Diving Specialist

Scripps Institution of Oceanography

La Jolla, California

Livingston, Robert B.

School of Medicine

University of California Medical Center

Los Angeles 24, California

Loefer, John B.

Office of Naval Research Branch

Office

1030 E. Green Street

Pasadena 1, California

Loosanoff, V. L.

U.S. Fish and Wildlife Service Laboratory

Milford, Connecticut

Margalef, R.

Inst, de Investigaciones Pesqueras

Ronde Guinar do 31

Barcelona, Spain

Marr, John C.

U.S. Fish and Wildlife Service

La Jolla, California

Matsui, Y.

Kyoto University

Kitashirakawa, Sako-ku

Kyoto, Japan

Mazia, Daniel

Dept, of Zoology

University of California

Berkeley 4, California

McBlair, W.

Dept, of Zoology

San Diego State College

San Diego 15, California

Mohler, Irvin C.

American Institute of Biological Sciences

2000 P Street, N.W.

Washington 6, D.C.

Montalenti, G.

Istituto di Genetica

Via Mezzocanno 8

Napoli, Italy

Moore, Hilary B.

Marine Laboratory

University of Miami

Coral Gables 34, Florida

Morris, Ailene M.

Visibility Laboratory

Scripps Institution of Oceanography

La Jolla, California

Munk, Walter H.

Division of Marine Geophysics

Scripps Institution of Oceanography

La Jolla, California

Neave, Ferris

Fisheries Research Board of

Canada

Biological Station

Nanaimo, B.C.

Canada

Nigrelli, Ross F.

New York Aquarium

New York Zoological Society

185th Street and Southern

Boulevard

New York 60, New York

Norris, K.

Marineland Oceanarium

Redondo Beach, California

North, Wheeler J.

Dept, of Marine Biochemistry (Fellow)

Scripps Institution of Oceanography

La Jolla, California

Novick, Aaron

Committee on Biophysics

University of Chicago

5040 Ellis Avenue

Chicago 37, Illinois

Odum, E. P.

Dept, of Zoology

University of Georgia

Athens, Georgia

Papenfuss, G.

Dept, of Botany

University of California

Berkeley 4, California

Parker, Robert H.

Dept, of Submarine Geology

Scripps Institution of Oceanography

La Jolla, California

Pequegnat, W. E.

Pomona College

Claremont, California

Phleger, Fred B.

Dept, of Marine Geology and Geochemistry

Scripps Institution of Oceanography

La Jolla, California

Pinchot, G. B.

Dept, of Microbiology

Yale University

New Haven, Connecticut

Pittendrigh, C. S.

Dept, of Biology

Princeton University

Princeton, New Jersey

Provasoli, L.

Haskins Laboratories

305 E. 43rd Street

New York 17, New York

Rae, K. M.

Scottish Marine Biological Association

8 Craighall Road

Edinburgh, Scotland

Ragotzkie, Robert A.

Dept, of Biology

University of Georgia

Sapelo Island, Georgia

Rakestraw, Norris W.

Dept, of Marine Geology and Geochemistry

Scripps Institution of Oceanography

La Jolla, California

Ray, D. L.

Dept, of Zoology

University of Washington

Seattle 5, Washington

Rechnitzer, Andreas B.

Dept, of Marine Vertebrates

Scripps Institution of Oceanography

La Jolla, California

Redfield, A. C.

Marine Biological Laboratory

Woods Hole, Massachusetts

Revelle, Roger R.

Director

Scripps Institution of Oceanography

La Jolla, California

Reynolds, Orr E.

Director, Biological Sciences Division

Office of Naval Research

Washington 25, D.C.

Riedl, R.

Zoologisches Institut der Universität

Wien, Austria

Rivero, Juan

Marine Biological Station University of Puerto Rico Mayaguez, Puerto Rico

Roberts, Eugene

Dept, of Biochemistry

Division of Research

City of Hope Medical Center

Duarte, California

Rodhe, W.

Institute of Limnology

University of Uppsala

Uppsala, Sweden

Russell, Findlay E.

Laboratory of Neurological Research

College of Medical Evangelists

Los Angeles County General

Ho spital

Los Angeles 33, California

Sargent, Marston

Office of Naval Research

Scripps Institution of Oceanography La Jolla, California

Sawaya, Paulo

Dept, of General and Animal Physiology

São Paulo University

São Paulo, Brazil

Scagel, R. F.

Institute of Oceanography University of British Columbia Vancouver 8, B.C.

Canada

Schaefer, Milner B.

Director, Inter-American Tropical Tuna Commission

San Diego, California

Schevill, W.

Woods Hole Oceanographic Institution

Woods Hole, Massachusetts Scotten, Harold L.

Dept, of Marine Microbiology Scripps Institution of Oceanography La Jolla, California

Segerstråle, Sven G.

Zoological Museum of the

University

Helsinki, Finland

Shaver, John

California Institute of Technology

Pasadena, California

Shepard, Francis P.

Dept, of Submarine Geology

Scripps Institution of Oceanography

La Jolla, California

Sisler, F.

U.S. Geological Survey

Washington, D.C.

Skoog, Folke K.

Dept, of Plant Physiology

University of Wisconsin

Madison, Wisconsin

Smith, Ralph

Dept, of Zoology

University of California

Berkeley 4, California

Snodgrass, James M.

Dept, of Special Developments

Scripps Institution of Oceanography

La Jolla, California

Sund, Paul

University of Washington

Seattle 5, Washington

Sweeney, Beatrice M.

Dept, of Marine Botany

Scripps Institution of Oceanography

La Jolla, California

Szent-Györgyi, A.

Marine Biological Laboratory

Woods Hole, Massachusetts

Szilard, Leo

University of Chicago

Chicago 37, Illinois

Taylor, John H.

Visibility Laboratory

Scripps Institution of Oceanography

La Jolla, California

Temin, Howard

California Institute of Technology

Pasadena, California

Thomas, William H.

Dept, of Marine Botany

Scripps Institution of Oceanography

La Jolla, California

Thorpe, W. H.

Dept, of Zoology

Cambridge University

Cambridge, England

Thorson, Gunnar

Zoological Museum

University of Copenhagen

Copenhagen, Denmark

Tokioka, Takasi

Dept, of Marine Invertebrates

(F ellow)

Scripps Institution of Oceanography

La Jolla, California

Tonolli, L.

Istituto d’Idrobiologia

Pallanza (Navara)

Italy

Tonolli, V.

Istituto d’Idrobiologia

Pallanza (Navara)

Italy

Tyler, A.

California Institute of Technology

Pasadena, California

Tyler, John E.

Visibility Laboratory

Scripps Institution of Oceanography

La Jolla, California Volkmann, G.

Dept, of Descriptive Oceanography

Scripps Institution of Oceanography

La Jolla, Calilo rhia

Walker, Theodore J.

Dept, of Marine Vertebrates

Scripps Institution of Oceanography

La Jolla, California

Waterman, T. H.

Dept, of Zoology

Yale University

New Haven, Connecticut

Whittaker, Thomas

Agriculture Experiment Station

University of California

Davis, California

Wick, A. N.

Scripps Clinic and Research Foundation

La Jolla, California

Wieser, Wolfgang

Dept, of Zoology

University of Washington

Seattle 5, Washington Wilimovsky, Norman J.

Natural History Museum

Stanford University

• Stanford, California Wilson, A. C.

Dept, of Zoology

State College of Washington

Pullman, Washington

Wilson, D. P.

Marine Biol. Association of the United Kingdom

The Laboratory, Citadel Hill Plymouth, Devon England

Wolken, J. J.

Eye and Ear Hospital

University of Pittsburgh Medical Center

Pittsburgh 13, Pennsylvania Wooster, Warren

Dept, of Descriptive Oceanography

Scripps Institution of Oceanography La Jolla, California

Worthington, Marjorie

Dept, of Marine Microbiology Scripps Institution of Oceanography La Jolla, California

Yonge, Charles M.

Dept, of Zoology University of Glasgow Glasgow, Scotland ZoBell, Claude E.

Dept, of Marine Microbiology Scripps Institution of Oceanography La Jolla, California

CONTENTS 1

CONTENTS 1

PARAMETERS OF THE MARINE ENVIRONMENT

THE INADEQUACY OF EXPERIMENT IN MARINE BIOLOGY

PERSPECTIVES IN THE STUDY OF BENTHIC FAUNA OF THE CONTINENTAL SHELF

THE PARTICULATE AND THE COMPARATIVE CONCEPT IN MARINE SYNECOLOGY

AN ATTEMPT TO TEST THE EFFICIENCY OF ECOLOGICAL FIELD METHODS AND THE VALIDITY OF THEIR RESULTS

PARALLEL LEVEL-BOTTOM COMMUNITIES, THEIR TEMPERATURE ADAPTATION, AND THEIR BALANCE BETWEEN PREDATORS AND FOOD ANIMALS

SOME PROBLEMS IN LARVAL ECOLOGY RELATED TO THE LOCALIZED DISTRIBUTION OF BOTTOM ANIMALS

THE FUTURE OF UNDERWATER TELEVISION

ECOLOGY AND PHYSIOLOGY OF REEF-BUILDING CORALS

IRREGULARITIES OF DISTRIBUTION OF PLANKTON COMMUNITIES: CONSIDERATIONS AND METHODS

PERSPECTIVES IN THE STUDY OF SEASONAL CHANGES OF PLANKTON AND OF THE NUMBER OF GENERATIONS AT DIFFERENT LATITUDES

TOWARD PREDICTION IN THE SEA

SOME BIOCHEMICAL PROBLEMS IN MARINE BIOLOGY

HOMEOSTATIC MECHANISMS IN MARINE ORGANISMS

THE REGULATORY MECHANISMS OF CELLULAR RESPIRATION‡

MOTION, ENERGY TRANSMISSION, AND THE CELLULAR MATRIX

PERSPECTIVES IN THE STUDY OF BIOLOGICAL CLOCKS

STUDIES OF THE TIMING MECHANISMS OF DAILY, TIDAL, AND LUNAR PERIODICITIES IN ORGANISMS

SOME THOUGHTS ON BIOCHEMICAL PERSPECTIVES IN MARINE BIOLOGY

THE PRIMARY PRODUCTION AND STANDING CROP OF PHYTOPLANKTON

TEMPORAL SUCCESSION AND SPATIAL HETEROGENEITY IN PHYTOPLANKTON

SOME FUNCTIONAL ASPECTS OF INORGANIC MICRONUTRIENTS IN THE METABOLISM OF GREEN PLANTS

GROWTH FACTORS IN UNICELLULAR MARINE ALGAE ‡‡‡‡

MARINE MICROÖRGANISMS: SOME GENERALIZATIONS CONCERNING THEIR IMPORTANCE TO MARINE LIFE

ETHOLOGY AS A NEW BRANCH OF BIOLOGY

POLARIZED LIGHT AND PLANKTON NAVIGATION

PERCEPTION OF PATHWAYS BY FISHES IN MIGRATION*****

PERSPECTIVES OF EXPERIMENTAL RESEARCH ON SOCIAL INTERFERENCE AMONG FISHES

CHALLENGING PROBLEMS IN SHELLFISH BIOLOGY

SOME MARINE INVERTEBRATES USEFUL FOR GENETIC RESEARCH

PROBLEMS OF SPECIES FORMATION IN THE BENTHIC MICROFAUNA OF THE DEEP SEA

ASPECTS OF THE ENVIRONMENT OF PEARL-CULTURE GROUNDS AND THE PROBLEMS OF HYBRIDIZATION IN THE GENUS PINCTADA

SOME CHEMICAL BASES FOR EVOLUTION OF MICROORGANISMS

GENETICS AND MARINE ALGAE

GENETIC SYSTEMS IN SESSILE AND SEMISESSILE ORGANISMS

PROBLEMS OF SPECIATION IN MARINE INVERTEBRATES

PERSPECTIVES OF RESEARCH ON SEX PROBLEMS IN MARINE ANIMALS

A FEW REMARKS ON MARINE BIOLOGY, ANIMAL BIOLOGY, AND GENERAL BIOLOGY

SOME GENETICAL PROBLEMS PRESENTED BY SESSILE COELENTERATES

PERSPECTIVES IN MARINE BIOLOGY

PARAMETERS OF THE MARINE ENVIRONMENT

K. M. RAE Scottish Marine Biological Association Edinburgh, Scotland

We are asked to suggest what might be done to reach a better understanding of the relationships between organisms and between them and their physical environments and how we may bring some of the newer and more exciting experimental techniques to bear on these problems.

It seems to me that the first essential step is largely a technological one and I fear therefore that my suggestion is both mundane and naive. It calls for what we might term a school of plankton husbandry, or for a concerted effort by a team of workers to establish in our laboratories a series of oceanic animals which are amenable to experiment. We require, as it were, the marine equivalents of the guinea pig, the mouse, and the fruit fly, and I believe that without them our progress will remain slow and insecure. Our studies will continue to pose problems rather than provide solutions.

There are two main reasons for this: (1) until we can take a closer look at the animals and learn more of their intimate biology our field work will lack objectivity; (2) unless our laboratory work can become more realistic, it will not necessarily be relevant to the behavior of the animals in their normal habitats.

It is trite to reiterate the inevitable difficulties that face the ecologist who seeks to explain from his field observations alone why the animals in the sea are distributed as they appear to be or behave as they seem to do. He cannot observe the movements and behavior of his animals while they are taking place. He must first catch and kill his subjects and then deduce their activities in retrospect. He has no control over the variables and must extract his data from the normal sequence of events. Indeed, one of the few courses open to him is the arduous one of extending his observations over a long period in the hope that he may see cycles or trends in the quantitative or qualitative distributions. This achieved, he may hope to find also some parallel variation in an environmental factor which can be collated. If he is so fortunate, he can then postulate interrelationship between the two and await another long series of observations to support or contradict his hypothesis. But regardless of the ultimate significance of his correlations he is still far from establishing causal relationship. By the nature of his experiment, his conclusions are not amenable to rigorous proof. Unless he can control the environmental parameters in repeatable experiments, he can but argue the plausibility of the hypothesis by analogy with the accepted tenets of terrestrial ecology. He is further handicapped because many of the physical parameters of the natural environment are themselves interrelated; rarely can they be separated in any given locality or in any time series. If he attempts to overcome this limitation by comparing the behavior of animals in a variety of areas, then he is equally frustrated; he has at present no means of telling whether the animals in the different localities are comparable ecologically.

We are often reminded that, in the more exact sciences, the approach to a problem is in three phases: (1) the observation of the natural phenomena; (2) the formulation of a hypothesis to account for them; and (3) the experiment to test the hypothesis. In such an idealistic process our problem starts in the field with the collector and ends in the laboratory with the experimentalist. But we may well founder early in the sequence. We cannot hope to postulate useful hypotheses about the causes behind the distributions of animals unless we happen to measure also the relevant parameters of the environment. And, as I will try to explain below, there is some evidence that we at present are failing to do this. Or, as an extension of the argument, we may conclude that, until we can learn more about the environmental requirements of the marine fauna, the extensive and costly programs of systematic collection will fail to achieve their potential value.

I would not imply that programs of field sampling should be stopped or reduced in scope. On the contrary, they will ultimately provide the framework on which the mosaic of knowledge can be laid. We should, therefore, ensure that our records of long- and short-term fluctuations in natural populations are as comprehensive as possible. Rather I would suggest something of a reversal of the classic approach. We require, first, more realistic experiments in the laboratory designed to test the relative importance of the various environmental factors in order to ensure that we are measuring those which are significant in the sea.

In the past, there has been the tendency to presume that the gross physical and chemical parameters are the all-important ones. Temperature and the availability of inorganic nutrients have been singled out for particular attention possibly because of following closely the analogy with earlier conclusions in terrestrial ecology, or because of the limited selection of parameters available to the ecologist, who is usually forced to work with observations taken by the oceanographer for his own very different objectives. However, there is now a growing weight of opinion that other less obvious factors play the prime role in determining many of the variations of marine populations both in space and time. It seems that, although there is an over-all pattern to geographical distributions and seasonal productivity which is dictated by these gross physical and chemical conditions, superimposed upon this pattern are highly significant variations stemming from other causes. Whereas in the open ocean temperature may set the limits of distribution of a species and may restrict its breeding season to a certain part of the year at a given place, it does not necessarily influence directly the local success or failure of that species from year to year. This point was nicely made by Loosa- noff and his colleagues (1955) when they showed that there was no consistent agreement during eighteen seasons between the number of larvae of the American oyster and the common starfish which settled on collectors placed in Long Island Sound—despite the fact that the two animals select the same habitat, are similar in spawning habit, and, in the experiment, being in the same water, were subjected to identical environmental conditions. Clearly the more conventional environmental parameters were not here responsible for the relative survival of the larvae. Loosanoff and his colleagues conjectured on alternative explanations such as the possibility that the size or quality of the food particles required by the larvae might be different, or that specific parthenogens or growth factors were involved.

The latter possibility, the idea that the organic content of sea water or the biological factor may be critical, is by no means new. In some form or other it has occupied workers’ minds since Pütter first introduced unorthodoxy into the conventional concept of the food cycle. The earlier evidence for such nonpredator-pre y relationships was reviewed fully by Lucas (1947) when he postulated that organisms might produce external metabolites that could influence other organisms in either a beneficial or detrimental way. After the war, interest in this line of thought was greatly stimulated by Wilson’s demonstration that certain benthic larvae could be cultured more satisfactorily in one type of sea water, the so-called Sagitta elegans water, than in another, S. setosa war- ter. Whereas these two water types, or environments, could be readily recognized by the natural fauna they supported, they could not be differentiated by their physical or chemical properties, at least so far as these could be tested by conventional hydrographic techniques (Wilson, 1951; Wilson and Armstrong, 1952, 1954). Wilson found that small additions of S. elegans water would permit normal culturing in S, setosa water and so deduced that growth factors were involved. Loosanoff, Miller, and Smith (1951) and later Davis (1953) have also obtained compatible results in culture experiments with oysters and clams, while Rees (1954) has implied a similar effect with lamellibranch larvae in the open waters of the North Sea.

Wilson’s laboratory experiments, although not yet forced to a conclusion or explanation, are of enormous significance to the ecologist working on the North Sea. We know from its over-all distribution that S. elegans is to be found in those areas where oceanic water of Atlantic origin mixes with the more coastal waters. In company with a number of other planktonic indicator species,S. elegans prospers in the marginal areas that separate the typical North Sea cr English Channel environment from Atlantic conditions; areas in which the physical and chemical conditions may provide a compromise but in which the plankton does not. S. elegans is rarely to be found in the open ocean, but nevertheless within the North Sea and in the English Channel it can be taken to indicate some admixture of Atlantic water (Russell, 1939; Fraser, 1952), or some integration of a number of factors which is not at present definable.

For want of a more realistic criterion, we can use the admixture of Atlantic water, or the presence of the plankton-indicator species that the "mixed water* supports, as a parameter of environment. We then find that many, if not most, of the fluctuations in the animal populations within the North Sea can be related to it in a plausible way. I will not attempt to substantiate this statement here at any length. Indeed, I must stress that many of the relationships we believe to be emerging from our plankton studies are still speculative in the extreme; they are not easily established by field observations alone, as we have seen. But two examples may warrant brief mention, as they show how the plankton can be used as an indirect parameter of environmental conditions relevant to commercial fisheries and, therefore, how important it is for us to undertake more experiments in the laboratory on the ecology of these planktonic animals in order to understand why this is so.

It is an observable fact that there is general agreement both in space and time between the distribution of the mixed water plankton off the east coast of the British Isles and the spawning aggregations of herring. Each year, these indicator species appear to move southward from off the northeast coast of Scotland in July or August toward the Strait of Dover, reaching the southernmost limits of their drift in or about December. The concentrations of migrating herring, and the fisheries that exploit them, follow much the same sequence. Such a parallel course of events by itself might well be dismissed as being fortuitous; it is at the best a very broad generalization. But recently Glover (1955), in a preliminary account of his work, has implied a somewhat closer relationship by showing how the timing of the arrival of the mixed water indicators on the fishing grounds can be correlated with the distribution of the herring shoals. Over the past few years the progressively earlier appearance of Clione limacina in the plankton samples taken by the fishing boats off the Scottish coast has been accompanied by a southerly shift of the more profitable fishing areas and so presumably of the major spawning concentrations of herring. Whatever the change in the environment, which is reflected by Clione may be—and we have been unable to detect any compatible changes in those gross parameters that have been measured—it is not just local in its effect. Clione and other indicator species have shown a corresponding seasonal advance in our samples taken in the open Atlantic hundreds of miles, or months on the time scale, farther back along the current system (Rae, 1956).

To Glover’s evidence must be added the facts recorded by Russell (1939). From 1931 onward, from just the time when the S, elegans community gave way to S. setosa off Plymouth, the younger age groups of herring became progressively scarcer in the local catches until the fishery collapsed. Earlier, Burton and Meek (1932) had also associated poor catches of herring off the northeast coast of England with unusual numbers of S. setosa there instead of the expected S. elegans.

It is, then, tempting to suggest that the spawning migrations of herring are conditioned by the mixed water environment, and in this respect another interesting point has emerged from Glover’s work which has not yet been published. Hardy, Lucas, Henderson, and Fraser (1936) demonstrated the close relationship between the day-to-day distributions of the herring and of Calamis, their basic diet. Using the same technique in another fishery, Glover and his colleagues have now found that the spatial correlation between the predator and prey is quite as good during those weeks just before spawning when the fish are not feeding as it is at other times when they are. In the northern North Sea, Calanus abound in mixed water and this raises the question of whether the herring aggregate on the concentrations of copepods or some other environmental factor. It may be some property of water rather than the availability of food which attracts the fish (see also Russell, 1952, p. 4), and by analogy we need not necessarily expect it to be any obvious property in view of the startling discovery that migrating salmon will react to an extract of mammalian skin in dilutions of the order of one part in a thousand million (Alder dice, Brett, Idler, and Fagerlund, 1954).

The change in the planktonic fauna, or the environment supporting it, in the English Channel was also reflected in the population of non- clupeoid fish there. Between 1931 and 1939 the total number of young fish caught off Plymouth fell to about one-tenth of their former value (Russell, 1939) and have since shown little sign of recovery. Henderson (1954), however, found a complementary increase in their number in the North Sea—a significant point when one remembers that, in the accepted model, a reduction of Atlantic flow into the Channel is compensated by increased penetration into the North Sea basin from the north (Russell, 1935).

More recently, we have found another and somewhat closer indication of this possible relationship between young demersal fish and the mixed water environment. Metridiß. lucens can also be used in the northern North Sea as a convenient indicator of the presence of water of Atlantic origin; it is more easily recognizable in our collections with the Hardy plankton recorder, than are the species of Sagitta, This copepod prospers in the open ocean, and during the late summer of each year it is carried into the North Sea basin (see Rae and Rees, 1947). Over the past ten years for which we have information, we have found that the distribution of Metridia, during the autumn and winter after it has entered the North Sea, is controlled by the prevailing winds. The correlation is sufficiently good to allow us to deduce from a knowledge of the winds where the Metridia, or the type of environment that supports them, will be at a given date just before the onset of the haddock spawning in the area. Whereas we have suitable plankton data for ten years with which to establish this correlation, information on the residual wind is available over the past fifty years, based on barometric differences at three standard stations (Dietrich et al., 1952). Estimates of the relative success of the haddock spawning, or the survival of the haddock during the first year of their life, have also been made for many years (see Parrish, 1949). We can therefore collate, indirectly through the wind, the orientation of the mixed water environment in respect to the spawning grounds with the success or failure of the annual haddock broods over more than thirty years. Statistically, it is beyond doubt that the two are in some way interrelated. And the assumption that they are has permitted surprisingly good forecasts of relative recruitment to the fishable stock over the past four or five years.

Russell (1952) has already given us a comprehensive review of the many ways in which hydrography, plankton distributions, and the commercial fisheries may be interdependent. It would be profitless for me to conjecture further here on what this cryptic factor carried by the mixed water may be. Suffice it to say that the general form of plankton distributions, with their inherent patchiness and pronounced changes from year to year in any given place, make it most unlikely that those chemical and physical parameters that are conventionally measured are solely involved. These tend, in the area we have studied at least, to be more gradual in gradient and rarely to conform in orientation to the comparatively sharp faunistic boundaries. Their variation between adjacent areas supporting rich or poor populations of a species is small when compared with the wide range of conditions under which that species may prosper at any given time. In the same way, while the plankton communities show pronounced fluctuations between years, the gross physical and chemical properties of the environment show relatively small anomalies. It may be that we are failing to integrate these environmental factors in the right way. For example, it has often been suggested that the cumulative temperature over some period may be more relevant than the contemporary value. Again, it may be that, as Russell (1939) suggested, the quantity of phosphate available sometime previously is the crucial factor, but I feel that Wilson’s results must now direct our search in other directions and toward the micro constituents of the sea water.

That fashionable chemical cobalamin is now receiving due attention and, although we should not be too optimistic, it has a good deal to commend it. It has a fine array of analogues with different and sometimes conflicting properties. It is present in the sea in varying, if small, quantities. The microbiologists have shown that it is a vital growth factor in certain marine diatoms (Hutner and Provasoli, 1953; Lewin, 1954; Droop, 1955) and its importance to the basic metabolism of many animals is undoubted. It is found in extracts from herring (Tarr, 1955). Although neither Wilson and Armstrong (1954) nor Davis (1953) solved their culturing anomalies with animals by the addition of B,2 to the less favorable media, the negative implication is not necessarily secure until the possibility of specific requirements for particular analogues has been investigated. Kon and his colleagues at Reading are now undertaking a study of vitamin cycles in the sea and Johnston (1955) is experimenting with a variety of techniques to analyze any differences there may be in the organic content of the water masses that support the various planktonic indicators in our area. But both these lines of approach, and many others, would be greatly enhanced by laboratory tests if suitable subjects could be provided. The possibility, for example, of presenting a wide range of animals with cobalamin labeled in various ways is attractive. Recently we have learned that certain red algae, although they contain B12, can concentrate radioactive cobalt in some other stable organic compound (Scott and Ericson, 1955), and we know that some marine crustaceans and 1am ellibranchs also have a facility for accumulating cobalt (see Harvey, 1928, p. 51). Marshall and Orr (1955) are engaged in metabolic studies on Calanus using labeled phosphorus, and other workers have adopted similar techniques, but there remain many trace elements and compounds in the sea which await this method of attack. However, to make such experiments comprehensive it will be necessary to have animals available in captivity at all stages of their life histories.

Again, if we are to follow the promising lead set by Buzzati-Tra- verso and Rechnitzer (1953) in the study of specificity of the proteins and other organic constituents of marine animals to the best advantage, we will require a far wider range of subjects of whose genetics we have some knowledge.

It seems to me therefore that there is a pressing need for a broader, and much more systematic, approach in the laboratory. An extension, as it were, of Wilson’s work in which the criterion of the favorable environment is not merely the ability for larvae to develop normally during a few days or weeks but for oceanic animals to grow, mature, breed, and repeat the process—-to maintain their community as they do in nature. If the necessary techniques could be achieved, then by modifying the environment, we could determine which parameters are the more important and which less so; certain factors might be quickly eliminated as being irrelevant to the well-being of the animals and the range of the significant factors correspondingly narrowed. At the same time facilities for a far wider range of experimental studies would be provided than has previously been available.

Now, how difficult would such a project be? I must confess to little personal experience with the problems involved and I have found the literature on the subject by no means explicit. Although many workers have essayed with varying success to cultivate the particular species in which they were interested, no one seems to have made a systematic approach to the problem of keeping zooplankton in the laboratory. We are often told that oceanic animals are capricious in captivity but this after all is no more than a further reflection of our ignorance of their require ments. However, I feel there is little reason to be too pessimistic until a far more determined effort has been made. Instead, we may reflect on the enormous progress that has been made with culturing techniques for the neritic mollusks over the past decade and the wealth of knowledge about the ecology of certain lam e llib ranchs which has been acquired (see Loosanoff, 1954).

Let us take as one example that ubiquitous copepod Calcimi s fin- mar chicus, which has probably received as much attention as any marine animal. In European waters Calanus is found in two forms, fin- mar chi cus and helgolandicus, the relative status of which is still obscure (Rees, 1949). There is also the possibility of a third, or intermediate, form (Marshall, Orr, and Rees, 1953). Yashnov (1955), after comparing specimens from a very wide area, believes that the species is even more heterogeneous; he describes five type specimens that are morphologically distinct. We know that the mean sizes of individuals of both finmarchicus and helgolandicus vary considerably between generations within any community and again markedly between communities or races living comparatively close together (Rees, 1956). Within the North Sea, finmarchicus and helgolandicus have centers of distribution which may be dictated by temperatures, but both show characteristic fluctuations in abundance and distribution from year to year which my colleague Dr. Rees believes can be attributed to the effect of the mixed water factor. Calanus, then, would appear to be a most promising subject for the sort of laboratory experiments we have in mind. A study of its genetics, its reaction to changes in its intimate environment, its metabolic requirements, its biochemistry, and so on, would hold great interest.

It is encouraging, therefore, to realize how hardy Calanus appears to be when brought into the laboratory and how tolerant it is in captivity at least as far as the more conventional parameters of environment are concerned. Marshall and Orr (1955, p. 34) describe how adult females can be kept alive and healthy for over a month in glass dishes containing only 25 ml. of sea water provided the water is changed every other day. Such individuals continue to lay eggs over the period and recover the propensity to do so even after being starved in microfiltered water for fifteen days. Again in the same monograph (p. 78) we find an account of Calanus laying eggs in captivity, the nauplii from which survived through eleven molts to reach the adult stage about five weeks later under the following conditions: . the Calanus were kept singly in 250 ml. beak

ers standing in tanks with circulating water, the temperature being 14—15° C. on the few occasions it was taken. The water was changed daily to provide food and the Calanus were removed almost daily for measurement." Such is not the case history of a delicate or fragile subject. One reads further of experiments in which Calanus have survived fluctuations in temperature, salinity, pH, oxygen tension, and illumination many times greater and far more rapid than would ever be encountered in the open seas.

The only phase in their life cycle which Calanus do not readily undertake in captivity is successful copulation. Females caught after spermatophores have been attached will lay eggs that will develop to appar ently normal adults of both sex. It seems only reasonable to suppose, therefore, that comparatively minor improvements in the method of keeping them would permit successive generations to be reared, and we have no cause to suppose that Calanus is any more amenable to captivity than most other oceanic invertebrates. It may be that we will have to discover, by trial and error, the environmental stimulus that releases the mating impulse. An ability to recognize through some environmental property the onset of conditions conducive to the survival of the progeny would be a highly selective attribute in nature. The general existence of some facility of this sort may, in fact, help to account for the surprising way in which planktonic eggs and larvae so often occur in the midst of diatom concentrations, and even the tentative relationships between fish and mixed water which I have mentioned.

It is of course much easier to declare what one thinks should be done than to explain how to do it. Progress in such a project can only come by profiting from experience gained in the initial stages. But I would suggest that we might first undertake a series of pilot experiments, using simple equipment, to compare the relative survival of a whole series of planktonic forms. We might hope to select the more promising subjects. For instance, we have Isias clavipes in the oyster tanks at Conway; Walne (1956) states that when these tanks of about 400,000 liters capacity are filled with sea water, Isias soon becomes the dominant copepod. Yet, in our area, Isias is nowhere reported as being abundant; we find it in ones and twos in our plankton catches in which the commoner species occur in their thousands.

At the same time various techniques for collecting the plankton and bringing it to the laboratory could be compared. It may prove necessary to collect in the dark and to keep the animals away from direct illumination under controlled temperature; some workers have adopted such techniques (e.g., Hardy and Paton, 1947), but, although the effect of shock due to sudden changes must be mitigated thereby, the value toward the subsequent survival of the animals has not, to my knowledge, been tested systematically.

If under such simple conditions a reasonably consistent index of survival could be established, then we could turn to a series of trials with a selection of species in various culture media ranging from the water out of which the test animals were taken through other natural sea waters to artificial sea waters dispensed from various formulas. Each water might be tried unfiltered, filtered, and enriched with the filtrates from the others or with artificial nutrients. The more easily varied physical parameters, light, temperature, oxygen content, might also be tested against controls to give some indication of the tolerance of the animals and the relative importance of these conditions to their survival. Clearly, all these experiments would have to be repeated over and over again on a grand scale to permit planned statistical analyses of the results, and they would require considerable effort if an adequate series of tests were to be conducted with subsamples from single collections of plankton; that is, on subjects that would start under more or less comparable conditions.

Our primary object, however, is to enable our captives to breed successive generations under our supervision, and while doing these simpler experiments we should not lose sight of what is undoubtedly the only realistic criterion of the adequate ecological environment. It is not one that merely permits the individual animal to survive for a given span or to continue its metabolism at a specified level. It is such that a community of animals can reproduce sufficiently successfully to maintain their population density in the face of their natural predators. I think therefore, pending further experience or knowledge, it might be profitable to approach the problem in a more direct if empirical way. We should design some fairly large containers in which as many factors as possible can be controlled or even monitored automatically so that we can simulate the environment from which the beasts were taken as closely as is practicable. Most of the conventional parameters are fairly easy to handle; temperature, light, salinity, gross chemical composition, oxygen content, pH, etc., present few difficulties. On the other hand, the changes in pressure associated with the vertical migrations of the order usually undertaken in nature do offer formidable technical problems. But it is generally assumed that diurnal vertical migration is primarily conditioned by light intensity, whereas seasonal vertical migrations may be influenced by temperature; possibly, by the necessity for the animals to reduce their rate of metabolism by sinking into the colder layers and so survive the period when food is scarce. We may hope therefore that with suitable control of light, temperature, and food supply, we can moderate the stimuli to dive. On the field evidence, this does not seem too improbable as we find that the vertical extent of diurnal migration and the length of season spent in the depths varies greatly with latitude and local conditions. As an initial step, we might also compare the behavior in captivity of those animals that show marked vertical migration and of those that normally remain near the surface.

We might also consider another approach often mooted but rarely tried, that of confining animals in the sea in anchored cages constructed of gauze screens or of lowering them in compressible but impervious containers. It might help us to assess the adverse effect of restraining vertical migration or even tolerance to a change from one natural environment to another.

As I stated at the outset, these proposals may be all too naive. I have, undoubtedly, glossed over the many practical difficulties entailed. Indeed, I am mindful of the very real problems involved in transporting the animals from their natural habitat in the open sea to the artificial one in the laboratory, of sorting them, and of maintaining the necessary biological balance in the aquaria. But, nevertheless, I do not think that the realization of such potential difficulties should discourage the effort, at least until more systematic and concerted trials have been made. Even if we fail over a period, at least we should learn something in the process which may help us to assess the relative ecological importance of the many parameters of environment and in particular the relative significance of the organic* and inorganic* components.

If we succeed in establishing a reasonable variety of healthy plankton species in captivity, we open up entirely new facilities for a wide range of studies that have not yet been applied to oceanic animals. We may then expect to interest more experimentalists in marine organisms and so bring new techniques and ingenuities to bear on the basic problems. It may well be that once they can be handled, oceanic animals, conditioned to such slow changes in their natural environment, will make excellent material for fundamental studies.

In conclusion, however, I would reëmphasize the point that until we become more adept at bringing marine animals under our control, particularly the oceanic forms, we are not well prepared to take advantage of many of the excellent techniques of the experimentalist, be he a biochemist, a biophysicist, a geneticist, or a microbiologist.

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DISCUSSION

M. W. Johnson

It is fitting that this symposium should be opened with a discussion by Dr. Rae of the plankton, since in the marine this category of organisms is of prime importance to the life of all the other marine creatures and, indeed, has had a great influence on the whole evolutionary picture of structure and habit of the overwhelmingly abundant forms that feed upon the plankton.

With reference to Dr. Rae’s statement that in studying the plankton the animals are not observed in the living condition. This is certainly generally true, but it should be pointed out that something is being done about this, although still in a rather crude manner.

With the discovery of the diurnal movements of the deep scattering layer and its association with plankton stratification in 1945, we have a sonic means of following the diurnal movements of certain planktonic organisms and their predators even at considerable depths. Regarding the problems of rearing marine animals in the laboratory, Dr. Rae’s observation that Isias thrives in larger numbers in oyster tanks than in nature is encouraging to experimentalists and field workers alike. Here at Scripps we find that judging from relative concentrations the copepod Tisbe fur cata and also the small tub e wo rm Spirorbis thrive better in our salt-water system than in nature. This doubtless results in part from lack of competition, predators, and diminution of dispersal of larval stages. These organisms are not haloplanktonic, and the larvae oo cur only briefly, or sometimes not at all, in the plankton from whence they are pumped into the system. Of great importance to rearing is the duration of the larval stages. In Tisbe the minimum time from egg-to- egg production is only fifteen days with no real planktonic larva. This contrasts sharply with the California spiny lobster, which has a floating phyllosoma stage of six or seven months. In the male crab there is evidence that the matter of providing food accessible to the type of foodgathering apparatus of the zoea is critical.

K, M. Rae

When mentioning Isias, I was thinking in terms of simple trials that might show us quickly which species were the more tolerant of the artificial environment and therefore promising subjects for further experiment. But, as Dr. Johnson points out, comparative survival tests might also suggest differences between the ecology of closely allied species that are not to be recognized so easily from field observations.

For example, I do not think there is at present any evidence to suggest that Isias clavipes has a shorter life cycle or is a more voracious predator than the other commoner copepods of comparative size in our waters. It would be interesting therefore to find out what factors in the artificial environment enhance its survival when compared with, say, Pseudocalamis, Tempra, and Acarfia.

F, H. Johnson

Hydrostatic pressure has been briefly alluded to and I should like to emphasize its importance as one of the parameters of the marine environment. Although it may not be significant as a factor in the life of planktonic organisms, there is every reason to believe that it is fundamentally important in the life and activities of deep-sea organisms. There is abundant evidence that pressures, such as those existing at depths of 1,000 meters and more may greatly modify specific enzyme reactions, nerve and muscle activity, cell division, reproductive rate, and numerous other physiological processes of aquatic and terrestrial organisms, as discussed at some length in the recent book The Kinetic Basis of Molecular Biology, by Johnson, Eyring, and Polissar. In many instances the net influence of increased hydrostatic pressure may be modified or even reversed by changes in temperature. Oddly enough, very little research has been carried out with respect to the relationship between hydrostatic pressure and biological reactions in deep-sea organisms, yet it is only in the depths of the sea (and possible in deep oil-well brines) that living materiell exists naturally under hydrostatic pressures sufficiently great to exert significant influence directly on the rates and equilibria of chemical reactions.

Kt M, Rae

I agree that this is a most challenging aspect of marine physiology, but I suspect that it has received less attention than it warrants because of the formidable technical problems involved. The wide variety of marine creatures which tolerate high hydrostatic pressure, or undertake vertical migrations through a wide range of pressures in nature, are not yet available to the experimentalist, and it may prove difficult to get them into suitable pressurized containers.

I think particularly interesting might be those species of copepods which after spending the spring or summer months comparatively near the surface, over-winter in depths exceeding 1,000 meters. With the very stable environmental conditions that prevail at these depths, it is not easy to suggest the stimulus that incites them to return toward the surface in the following spring. Presumably, it must be internal and linked with some cumulative metabolic process, but any such explanation is complicated by 0stevedt’s observation (Hvalradets Skrifter, 40, 1955) that subsequent generations of the same species spend very different lengths of time in the deep water. In the Norwegian Sea, the majority of Calanus finmarchicus born in the upper layers during the spring grow to Stage V and then sink into deep water to hibernate. A minority, however, mature