Post-prandial changes in digestive enzymes and chyme characteristics of bigfin reef squid (Sepioteuthis lessoniana)

Abstract

Bigfin reef squid (Sepioteuthis lessoniana) is a candidate squid species that has potential to be utilized in aquaculture on a commercial scale. Although this species has been successfully cultured over multiple generations, appropriate feeding strategies are still limited due to a lack of understanding of its digestive physiology. The present study focused on digestive enzymes and chyme characteristics in terms of time response profiles following feeding. Squids (1.78 ± 0.05 g body weight) were serially collected at different post-prandial times (0, 0.5, 1, 2, 4, 6, 8, 12, 18 and 24 h) and the specimens were used in the analysis of digestive enzymes (n = 10) and chyme characteristics (n = 5). Food provided to the animals substantially transited to the gastrointestinal tract and peaked at 1 h after feeding, and then dramatically decreased with post-prandial time (P < 0.05). The digestion process was initiated shortly after the food arrived and exhibited the same pattern over 24 h of observation. The highest activities of protein-, carbohydrate- and lipid-digesting enzymes were observed within a range of 0.5 to 4 h after feeding and reached basal levels as observed in fasted squids post-prandially within 8 h. Pearson correlation analysis indicated a highly significant relationship between digestive enzyme activity and digestosomatic index across post-prandial times (r = 0.660–1.000, P < 0.01). These responses matched well with chyme characteristics, in terms of thermal properties of nutrients, microstructure, and molecular weight patterns of the relevant proteins. Findings from the current study have thus provided basic information on the digestive physiology of bigfin reef squids that can be applied when designing specimen-harvesting strategies.