Effect of environmental salinity and dopamine injections on key digestive enzymes in hepatopancreas of the euryhaline crab Cyrtograpsus angulatus (Decapoda: Brachyura: Varunidae

MICHIELS, M.S.; DEL VALLE, J.C; LÓPEZ MAÑANES, A,A.

SCIENTIA MARINA

INST CIENCIAS MAR BARCELONA

Lugar: Barcelona; Año: 2013 vol. 77 p. 129 - 136

0214-8358

SUMMARY: We studied the occurrence and characteristics of lipase activity and the response of lipase and proteolyticactivity to salinity and dopamine injections in hepatopancreas of the euryhaline crab (Cyrtograpsus angulatus). Lipaseactivity was maximal at pH 8.5; it exhibited Michaelis-Menten kinetics (apparent K=0.019 mM), was higher at 37°C andappeared to be cold tolerant, being also high at 4°C. In 10 psu (hyper-regulation conditions), lipase and proteolytic activitywere about 3 and 5 times higher, respectively, than in 35 psu (osmoconformation). In 40 psu (hypo-regulation), lipase activitywas about three times higher than in 35 psu, while proteolytic activity was similar. Lipase activity was inhibited in vivo by10?4 M dopamine in 35 psu but not in 10 or 40 psu. Proteolytic activity was not affected by 10m M dopamine. The differentialresponses of lipase and proteolytic activity to salinity and dopamine suggest the occurrence of distinct digestive adjustmentsand mechanisms of regulation upon osmoregulatory conditions. This study contributes to a better understanding of thecomplexity of the biochemical adaptations to salinity in euryhaline crabs. The fact that higher digestive enzyme activitiescould be associated with a differential digestive capacity potentially leading to enhanced availability of energy substrates isdiscussed.