Feeding and osmoregulation in the euryhaline crab Neohelice granulata: Digestive parameter responses

Abstract

When a species often experiences variation in its environmental conditions, metabolic flexibility is required. We studied the duration of the digestive cycle and the activity of key digestive enzymes (proteolytic, amylase, lipase) at short and long times after feeding in the hepatopancreas of the osmoregulator crab Neohelice granulata from the Mar Chiquita coastal lagoon (Buenos Aires Province, Argentina). We compared these responses upon hyper-regulation and under osmoconformation conditions (10 and 35 psu). The results show the ability of this crab to hyper-regulate in different feeding states. No significant differences were observed in the duration pattern of the digestive cycle between hyper-regulation and osmoconformity. However, distinct responses after feeding were observed in the activities of the digestive enzymes studied in relation to the osmoregulatory state. In individuals exposed to 35 psu, proteolytic activity was higher at 8 h and remained constant until 72 h after feeding. At 10 psu, this activity was higher at 48 h after feeding than before feeding. At 35 psu, the amylase activity after feeding was greater than the prefeeding activity. No differences were observed in the activity of lipase at 35 psu, but at 10 psu this activity was lower 1 h after feeding than before feeding. This work constitutes a contribution to our knowledge of the physiology of crustaceans and attempts to clarify the possible mechanisms of digestive settings associated with hyper-regulation.