Responses of digestive enzyme profiles in newly-hatched (Zoea I) larvae of the mud crab Scylla serrata to intermittent food availability and food deprivation.

Abstract

Activities (mU larva-1) of enzymes critical to digestion were examined to better understand how newly-hatched (Zoea I) larvae of the mud crab Scylla serrata respond to intermittent food availability and food deprivation. Specifically, this study examined the activities of trypsin-like proteases, nonspecific esterases, and α-amylase across three experiments that simulated scenarios in which larvae hatch and experience rearing conditions where food was either: (1) continuously available or unavailable; (2) initially unavailable, but subsequently available; or (3) initially available, but subsequently unavailable. Results showed that food availability exerts a significant influence on enzyme profiles in newly-hatched larvae, with nutritional history influencing their response to food deprivation. When food was unavailable from hatch, there was no significant change in larval enzyme activities between 6 and 78h post-hatch. If food became available at any point during this period, however, newly-hatched larvae were capable of rapidly (within 12-24h) adjusting enzyme activities in response. Furthermore, a short (36h) period of food availability appears sufficient to permit continuous substrate utilization during subsequent food deprivation of equivalent duration. Such flexibility is an important physiological strategy allowing newly-hatched larvae of S. serrata to adapt and thrive in challenging tropical oceanic environments and provides a basis for optimizing protocols for hatchery production of this species.