Digestive enzymes of the anchovy Engraulis capensis in relation to diet

Abstract

Digestive enzymes of the anchovy Engraulis capensis in relation to diet' Department of Microbiology, University of Cape Town, Rondebosch 7700, South Africa Institute for Marine Environmental Research, Prospect Place, Plymouth PL1 3DH, United Kingdom ABSTRACT: The anchovy Engraulis capensis (Glch.) is capable of exploiting both diatoms and Crustacea as a food resource. Much of the crustacean exoskeletal rnatenal passes into the hindgut after initial dsruphon in the stomach. Both laminarinase and cl-amylase activity are relatively low in the oesophagus and stomach, but increase in the caeca and lumen of the intestine. There is no evidence of cellulolytic activity in the gut although numerous gut bacteria occur in the caeca and lumen of the intestine. Distribution of protease activity in the gut follows that of carbohydrases, most proteolytic activity being present in the lumen of the intestine, rather than in the oesophagus or stomach. In contrast, chitinase activity is found early in the digestive pathway and is capable of attacking the chitinous exoskeleton of Crustacea in the stomach, prior to hydrolysis of their contents by carbohydrases and proteases. Bacteria isolated from the intestinal caeca do not hydrolyse chitin, nor do they degrade long-chain polysaccharides or azocasein. Most of the isolates were capable of utilisation of simple sugars cornnlonly found in diatoms and released following hydrolysis of polysaccharides, and also of utilisation of N-acetylglucosamine formed as an endproduct of chitin hydrolysis. Anaerobic strains were, In addition, capable of urea utilisation. Our data thus suggest that digestive enzymes allow E capensjs to exploit a wide range of food items, including diatoms and Crustacea, without bacterial involvement. The gut rnicroflora may be primarily maintained by uptake of the endproducts of carbohydrate, protein and chitin degradation.

Characterization of cellulase-producing bacteria from the digestive tract of tilapia, Oreochromis mossambica (Peters) and grass carp, Ctenopharyngodon idella (Valenciennes)

“…In the present investigation, a considerable population of bacterial symbionts has been isolated from the alimentary tracts of the Chinese grass carp, C. idella and tilapia, O. mossambica and some of the strains exhibit significant cellulolytic activity. The microbial populations within the digestive tract of fish are rather immense (Trust, Bull, Currie & Buckley 1979; Rimmer & Wieb 1987; Seiderer, Davis, Robb & Newell 1987; Sutton & Clements 1988; Clements 1991; Luczkovich & Stellwag 1993; Ringø & Strøm 1994; Kandel, Horn & Van Antwerp 1994; Clements & Choat 1995), with a number of microorganisms much higher than in the surrounding water, indicating that the digestive tract provides favourable ecological niches for these organisms (Trust & Sparrow 1974; Horsley 1977; Austin & Al‐Zahrani 1988; Sakata 1990). While the digestive tract of endotherms is colonized mainly by obligate anaerobes (Finegold, Sutter & Mathisen 1983), the predominant bacterial genera/species isolated from most fish guts have been aerobes or facultative anaerobes (Trust & Sparrow 1974; Horsley 1977; Sakata 1990; Bairagi et al 2002; Ghosh et al 2002).…”

Digestion of natural food by larval and post-larval turbot Scophthalmus maximus

“…Few studies have analysed for chitinolytic enzyme activity in fish larvae, although chitinase has been reported in the eggs and larvae of red sea bream Pagrus major (Kono et al 1987) and from the late yolk sac stage and beyond in trout Salmo gairdnen (Lindsay 1985). Even in adult fish which feed on crustaceans, chitin does not appear to be fully utilized (Seiderer et al 1987). Lindsay (1984) concluded that, in adult fish, the primary function of chitinase may be for the initial chemical disruption of the exoskeleton of prey.…”

Comparison of different stoichiometric methods for the estimation of proximate biochemical composition of crustacean zooplankton and some considerations on energy transfer to planktophagous fish

“…In fact, although chitinolytic activity has been observed in the digestive tract of several fish species (e.g. Yoshida & Sera 1970;Sakata et al 1980;Benmouna et al 1986;Seiderer et al 1987;Danulat 1987), it is not clear how far chitin is effectively assimilated and utilized for metabolic requirements. Indeed, several authors have observed chitinous exoskeletons lingering in the gut of fish (e.g.…”