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Behavior and Locomotion During the Dispersal Phase of Larval Life FAU Institutional Repository http://purl.fcla.edu/fau/fauir This paper was submitted by the faculty of FAU’s Harbor Branch Oceanographic Institute. Notice: © 1995 CRC Press. This manuscript is an author version with the final publication available and may be cited as: Young, C. M. (1995). Behavior and locomotion during the dispersal phase of larval life. In L. R. McEdward (Ed.), Ecology of marine invertebrate larvae (pp. 249-277). Boca Raton, FL: CRC Press. ECOLOGY OF MARINE INVERTEBRATE LARVAE Edited by Larry McEdward Associate Professor of Zoology University of Florida Gainesville, Florida CRC Press Boca Raton New York London Tokyo Library of Congress Cataloging-in-Publication Data Ecology of marine invertebrate larvae I edited by Larry R. MeEd ward. p. em. ·· (Marine science series) Includes bibliographical references and index. ISBN 0-8493-8046-4 (alk. paper) I. Marine invertebrates--Larvae--Ecology. I. McEdward, Larry R. II. Series. QL364.18.E36 1995 592.092--dc20 94-41885 CIP This book contains information obtained from authentic and highly regarded sources. Reprinted material is quoted with permission, and sources are indicated. A wide variety of references are listed. Reasonable efforts have been made to publish reliable data and information, but the author and the publisher cannot assume responsibility for the validity of all materials or for the consequences of their use. Neither this book nor any part may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, microfilming, and recording, or by any information storage or retrieval system, without prior permission in writing from the publisher. All rights reserved. Authorization to photocopy items for internal or personal use, or the personal or internal use of specific clients, may be granted by CRC Press, Inc., provided that $.50 per page photocop­ ied is paid directly to Copyright Clearance Center, 27 Congress Street, Salem, MA 01970 USA. The fee code for users of the Transactional Reporting Service is ISBN 0-8493-8046-4/95/$0.00+$.50. The fee is subject to change without notice. For organizations that have been granted a photocopy license by the CCC, a separate system of payment has been arranged. CRC Press, Inc.'s consent does not extend to copying for general distribution, for promotion, for creating new works, or for resale. Specific permission must be obtained in writing from CRC Press for such copying. Direct all inquiries to CRC Press, Inc., 2000 Corporate Blvd., N.W., Boca Raton, Florida 33431. © 1995 by CRC Press, Inc. No claim to original U.S . Government works International Standard Book Number 0-8493-8046-4 Library of Congress Card Number 94-41885 Printed in the United States of America I 2 3 4 5 6 7 8 9 0 Printed on acid-free paper Behavior and Locomotion 8 During the Dispersal Phase of Larval Life Craig M. Young TABLE OF CONTENTS Introduction .................................. .......... ...................................................... 250 Buoyancy. Drag. and Locomotion ...... ........................................................ 250 Buoyancy and Drag ... .............. .... .. .............................. .. .. ....................... 250 Locornot ion ........................ .. ................................................................... 251 Swimming Speeds and Trajectories ....................................... .. ......... 253 Depth Regulation and Orientation Behavior ............................................... 256 Tenninology ............. .......... .. ... ... ... ..... ............ .... ....... .. ... .... .. .. .. ........ ....... 256 Orientation Mechanisms ........................................................................ 257 Tactic Responses to Vector Cues ...................................................... 258 Kinetic Responses to Scalar Cues ..................................................... 261 Depth Regulation Mechanisms Involving Multiple Cues ................. 262 Behavioral Responses to Other Organisms .. ............................................... 262 Defensive Behaviors .. .......... .. ... .. ... ......................................................... 264 Intraspecific Aggregation ...... ................. ...... .. ... ....................... .............. 264 Responses to Zooplankton .................... ............. ..................................... 265 Larval Behavior in an Oceanographic Context ...... ......................... ........... 265 Field Studies of Behavior .... .............. .. ...... .. .................. .. ....................... 265 Vertical Migration .... .. ....................... ...................................................... 266 Responses to Oceanographic Features ................ .. ................ .. ...... ......... 266 Pycnoclines ............ .... ............................................... .......................... 267 Turbulence ... .. .... .......... ... ............ ... ........ .............. .. ............ ................. 268 Fronts ..................................................... ............................ .............. .. 268 Tides ... .. ... .............. ........................... ........................ ... .. .. ................... 269 Conclusions .. ... ........ .. ............................. ................................ ...................... 269 References ...... ... .. ...... ................................................................................... 270 O-X -PH-X0-4 6--lfJ:'\t$(uiO 1 ~- .:'\0 1 (J) 19 ) :'\ hy n~c Pr\.'SS, In": . 249 250 Ecology of Marine Invertebrate Larvae INTRODUCTION Swimming behaviors of marine invertebrate larvae had already been stud­ ied for more than 30 years when it was discovered in the 1920s that larvae are capable of actively selecting settlement sites and of delaying metamorphosis until a suitable substratum is found (Mortensen, 1921; Wilson, 1932; history reviewed by Young, 1990). These important findings brought larval behavior to the center stage of marine ecology, where it has remained a major subject of investigation ever since (Young, 1990; see recent reviews by Pawlik, 1992; Butman. 1987), but a recent focus on the role of oceanographic processes in recruitment (Roughgarden et al., 1988) has also resurrected interest in the behaviors larvae exhibit during the planktonic dispersal phase. It is clear from a large body of evidence that many larvae control their horizontal distribution and dispersal by nav igating vertically in the water column on both ontogenetic and diet schedules. In this review, I summarize the ways that larvae respond behaviorally to the biotic and abiotic attributes of their environment while swimming. This large body of work has been reviewed so many times (Sulkin, 1984; Forward, 1976; Young and Chia, 1987), that a comprehensive review is unnecessary. I will use examples from the recent literature to illustrate the range of known larval behaviors, while attempting to place the observations in a realistic ecological and oceanographic context. BUOYANCY, DRAG, AND LOCOMOTION BuoYANCY AND DRAG Most larvae are heavier than seawater and sink when swimming ceases. Some slow the ir rate of sinking by increasing drag with large feathery append­ ages (e.g., phyllosoma larvae of spiny lobsters), long setae (e.g., rostraria and mitraria larvae of polychaetes), or neutrally buoyant shells (e.g., echinospira larvae of Lamellarid gastropods). Buoyancy of many lecithotrophic larvae is conferred by lipid stores, though other low density substances (e.g., ammonia in the follicle cells of some ascidian eggs; Lambert and Lambert, 1978) may also be used tor flotation. Larval density is important from a behavioral standpoint because it either reinforces or counteracts the effects of vertical swimming (Sulkin, 1986). It is often assumed that buoyant lipids, particularly in lecithotrophic larvae, come from parental investments in the egg, that lipids are metabolized during larval life, and that the resulting decrease in buoyancy oflate-stage larvae is an important mechanism by which larvae sink to the bottom for settlement (Chia et al.. 1984). These ideas have recently been challenged by R. Olson (personal communication). who has demonstrated that late-stage lecithotrophic sea cu­ cumber larvae as well as newly settled juveniles tloat. Benavior and Locomotion During the Dispers<tl Phase of Larval Life 251 Some planktotrophic larvae accumulate lipids as they feed (Holland, 1978), thereby becoming increasingly buoyant as larval life progresses. Larval sand dollars (Pennington and Emlet, 1986) increase in density from 1.05 g ml- 1 in the prism stage to more than 1.25 g ml- 1 in the 6-arm stage. then decrease in density to 1.17 g ml ·1 as additional lipids are accumulated in the 8-arm stage. Addition of the echinus rudiment just before settlement does not substantially increase density; the young echinoid becomes heavier only after settlement, when juvenile ossicles are added (Pennington and Emlet, 1986). Nauplius larvae of the barnacle Balanus ehurneus feed in the plankton and store lipids in specialized oil cells. which are readily visible in the non-feeding, terminal cyprid stage (West and Costlow, 1987). In both of these examples (sand dollars and barnacles), the adults live in shallow water, making buoyancy a useful attribute for the late-stage larvae, but it is not clear whether lipid accumulates for the purpose of depth regulation or if buoyancy is a fortuitous by-product of lipids stored for another
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