Ontogenic change in phototaxis of the clam shrimp Eulimnadia braueriana Ishikawa, 1895 (Branchiopoda: Spinicaudata)

Abstract

Photoresponse in nauplii, juveniles, and adult hermaphrodites of the clam shrimp Eulimnadia braueriana Ishikawa, 1895 was measured under four different artificial illuminances ranging from 19,688 to 48,286 lux. The nauplii displayed consistent positive phototaxis through all illuminances. The juveniles and adults, however, showed no response to the dimmest light and reacted negatively at all the other treatments. The change in phototaxis occurs when nauplii develop into juveniles and may lead to a different vertical distribution. It signifies an adaptive strategy in dispersion, foraging, predator avoidance, and in minimizing intraspecific competition.