MEPS 155:309-313 (1997)  -  doi:10.3354/meps155309

The timing of larval release has important implications for a larva's potential vulnerability to predators and environmental stresses. For larvae with planktonic periods of only minutes to hours, timing of larval release also determines the light levels that larvae experience, which can strongly influence their settlement behavior. We placed larval traps over colonies of 2 common Caribbean sponges and found that both species released larvae during daylight hours. Niphatesdigitalis generally releases its larvae between 07:00 and 11:00 h, while Callyspongiavaginalis releases its larvae later in the day. Of 17 captured N. digitalis larvae released 0.5 to 1 m above the substrate, 13 remained near the bottom, and 8 of these 13 contacted the substrate within 10 min. For short-lived larvae, daytime release and their photonegative behavior at settlement should drive them to settle in shaded microhabitats that protect juveniles from predators and solar UV radiation. Larvae of N. digitalis and C. vaginalis are distasteful to potential predators; thus they can remain near the bottom with fishes and yet not be consumed. These data support a general co-occurrence of daytime spawning of conspicuous, short-lived larvae and larval distastefulness that previously had been noted only for tropical ascidians.

Sponges · Larvae · Timing of larval release · Larval dispersal · Larval palatability