Larval activity levels and delayed metamorphosis affect post-larval performance in the colonial ascidian Diplosoma listerianum

Abstract

It is becoming widely recognized that extending the larval period of marine invertebrates, especially of species with non-feeding larvae, can affect post-larval performance. As these carry-over effects are presumed to be caused by the depletion of larval energy reserves, we predicted that the level of larval activity would also affect post-larval performance. This prediction was tested with the cosmopolitan colonial ascidian Diplosoma listerianum in field experiments in southern Australia. Diplosoma larvae, brooded in the parent colony, are competent to settle immediately after spawning, and they remain competent to metamorphose for >15 h. Some larvae were induced to metamorphose 0 to 6 h after release, whilst others were induced to swim actively by alternating light and dark periods for up to 3 h prior to metamorphosis. Juvenile colonies were then transplanted to a subtidal field site in Port Phillip Bay and left to grow for up to 3 wk. Extending the larval period and increasing the amount of swimming both produced carry-over effects on post-larval performance. Colonies survived at different rates among experiments, but larval experience did not affect survival rates. Delays in metamorphosis and increased swimming activity did, however, reduce colony growth rates dramatically, resulting in 50% fewer zooids per colony. Moreover, such colonies produced initial zooids with smaller feeding structures, with the width of branchial baskets reduced by 10 to 15%. These differences in branchial basket size persisted and were still apparent in newly budded zooids 3 wk after metamorphosis. Our results suggest that, for D. listerianum, larval maintenance, swimming, and metamorphosis all use energy from a common pool, and increases in the allocation to maintenance or swimming come at the expense of post-larval performance.KEY WORDS: Delayed metamorphosis · Ascidian · Carry-over effects · Larvae · Settlement Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 246: [153][154][155][156][157][158][159][160][161][162] 2003 The main larval experience examined to date has been the simple prolongment of the planktonic period, which, in non-feeding larval stages, most likely results in energy reserves being depleted. Exposure to toxicants may also affect post-metamorphic performance (Pechenik et al. 1998), and, at least for species with lecithotrophic larvae, larval size may also influence post-metamorphic events (Moran & Emlet 2001). In this latter case, it is presumed that larger larvae have more energy reserves available at the time of attachment and metamorphosis. If the planktonic phase competes with metamorphosis for energy reserves, then we predict that variation in larval activity patterns will also affect the energy remaining for metamorphosis by changing rates of energy consumption. The most obvious energy demand on larvae is swimming. Ascidians, with their non-feeding, swimming, tadpole larvae, are strong (although previously untested) candidates for carry over effec...

Pelagic conditions affect larval behavior, survival, and settlement patterns in the Caribbean coral Montastraea faveolata

“…We therefore believe that the major patterns in our study result from differences in salinity rather than potential differences in DOM between treatments. The smaller size of settled planulae at lower salinities supports our hypothesis that resources are more rapidly depleted under adverse environmental conditions, yielding inadequate resources to sustain metamorphosis and calcification (Marshall et al 2003). Smaller size upon settlement has been shown to negatively affect future survival in many marine invertebrates: crustaceans (Clarke 1993, Guisande & Harris 1995, polychaetes (Qian 1994) and echinoderms (Hoegh-Guldberg & Emlet 1997).…”

Seasonal and interpopulational variability in fecundity, egg size, and elemental composition (CHN) of eggs and larvae in a grapsoid crab, Chasmagnathus granulatus

“…Besides the number and size, also the chemical composition of the eggs may vary among populations (O'Leary Amsler and George 1984;Wehrtmann and Kattner 1998). Generalizations of causes and consequences of intraspeciWc variation in reproductive traits, however, remain diYcult, mostly due to scarce knowledge of carry-over eVects, which occur between successive ontogenetic phases such as embryonic and larval development (HadWeld and Strathmann 1996;Marshall et al 2003).…”

Variation in the dispersal potential of non-feeding invertebrate larvae: the desperate larva hypothesis and larval size

“…The amount of time that larvae were observed swimming in this study does not represent the maximum larval duration for each of these species. The larvae of each species can successfully complete metamorphosis after at least 15 h (Wendt 1996, Marshall et al 2003, D. J. Marshall pers. obs).…”

“…Wendt 1996, Phillips 2002, Marshall et al 2003. To test this, we artificially delayed the metamorphosis of Watersipora larvae and determined the size of settlers.…”