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

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 alpha-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 78 h post-hatch. If food became available at any point during this period, however, newly-hatched larvae were capable of rapidly (within 12-24 h) adjusting enzyme activities in response. Furthermore, a short (36 h) 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.