Digestive enzyme activities and their distribution in the alimentary canal of larvae of the three extant lamprey families
Cake, M.H., Potter, I.C., Power, G.W. and Tajbakhsh, M. (1992) Digestive enzyme activities and their distribution in the alimentary canal of larvae of the three extant lamprey families. Fish Physiology and Biochemistry, 10 (1). pp. 1-10.
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The activities of trypsin (EC 188.8.131.52), chymotrypsin (EC 184.108.40.206), lipase (EC 220.127.116.11) and amylase (EC 18.104.22.168) were measured in different regions of the alimentary tract of ammocoetes from each of the three extant lamprey families. In the southern hemisphere species Geotria australis (Geotriidae), and even more particularly Mordacia mordax (Mordaciidae), enzymatic activity was almost entirely confined to prominent diverticular extensions which arise at the oesophageal-intestinal junction. However, in the holarctic Lampetra richardsoni (Petromyzontidae), which does not possess a diverticulum, the enzymatic activity was highest in the upper anterior intestine. It is not clear whether the presence of significantly higher amylolytic and lower lipolytic activities in the diverticulum of G. australis than in the exocrine tissue of the other two species reflects interspecific differences in the composition of their diets. The capacity of exocrine tissue extracts for chymotryptic and tryptic digestion was assayed before and after in vitro exposure to trypsin and enteropeptidase, their respective catalytic activators. Prior to exposure to these exogenous activators, both proteolytic enzymes were fully active in L. richardsoni, partially active in G. australis and totally inactive in M. mordax. Maximal chymotryptic activity was greater in M. mordax than in L. richardsoni and G. australis. In contrast, maximal tryptic activity was greater in L. richardsoni than in G. australis and was very low in M. mordax. Since trypsin is the only known activator of chymotrypsinogen, the negligible activity of trypsin in M. mordax would appear anomalous unless a trypsin inhibitor is present in the protopancreas of this species. Differences in the distribution of enzymatic activity within the alimentary tract of the three species is discussed in relation to proposed phylogenetic relationships amongst the extant lamprey families.
|Publication Type:||Journal Article|
|Murdoch Affiliation:||School of Biological and Environmental Sciences|
|Copyright:||© 1992 Kugler Publications|
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