Ontogeny of the gastrointestinal tract of marine fish larvae

Abstract

Marine fish larvae undergo major morphological and cellular changes during the first month of life. The ontogeny of the gastrointestinal tract combines these two aspects of the larval development and is very interesting in that the timing of functional changes appears genetically hard-wired. The goal of this paper is to give an overview of the gastrointestinal development process in marine fish larvae, with particular attention to three species: sea bass; red drum; and sole, since the description of gut maturation in fish larvae was initiated during the last decade with these species. During the early stages, marine fish larvae exhibit particular digestive features. Concerning the exocrine pancreas, amylase expression decreases with age from the third week post-hatching in sea bass and red drum (approximately 400 degree days), whereas expression of other enzymes (trypsin, lipase, phospholipase A2...) increases until the end of the larva period. Moreover, secretory function of the exocrine pancreas progressively develops and becomes efficient after the third week of life. Concerning the intestine, enzymes of the enterocyte cytosol (in particular peptidase) have higher activity in young larvae than in older. Approximately in the fourth week of post-hatching development in sea bass, red drum and sole larvae, the cytosolic activities dramatically decline concurrently with a sharp increase in membranous enzyme activities of the brush border, such as alkaline phosphatase, aminopeptidase N, maltase. This process characterises the normal maturation of enterocytes in developing fish larvae and also in other vertebrates' species. The establishment of an efficient brush border membrane digestion represents the adult mode of digestion of enterocytes. This paper also describes the role of diet on the development of the gastrointestinal tract. Indeed, the maturational process of digestive enzyme can be enhanced, stopped, or delayed depending on the composition of the diet.

Digestive Enzymes in Larvae and Juveniles of Farmed Sharpsnout Seabream (Diplodus puntazzo) (Cetti, 1777)

“…Early detection of digestive enzymes has been reported for several species of fish larvae [5,10,17,[52][53][54]. Enzymes related to metabolism (digestion, absorption and transport) of proteins, lipids and carbohydrates from the egg and yolk reserves have been detected following fertilization and immediately after hatching [55][56][57][58].…”

“…It is pointed out that amylase has been found to be an integral component of the enzymatic equipment in developing larvae of carnivorous fish and also enzymatic expression and initial high levels activity of amylase in marine fish larvae do not seem to be induced by food (enriched rotifers and Artemia nauplii) and could be better explained as a result of programmed gene expression [5,17,87]. However, the inductive property of this hydrolase has been described in early weaned sea bass larvae, D. labrax, fed micro-particulate diets with 12% starch [7].…”

“…These differences happen throughout the larval period with the maturation of some tissues and organs, in particular with the onset, decrease or increase in activity of a wide range of digestive enzymes [15][16][17].…”

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“…The activity of digestive enzymes can be a very effective indicator of fish larvae development, allowing to predict larval mortality and to evaluate the digestive abilities of fish (Zambonino Infante and Cahu, 2001), as well as their overall nutritional condition .…”

The changes in digestive enzymes and hormones of gilthead seabream larvae (Sparus aurata, L 1758) fed on Artemia nauplii enriched with free methionine

“…On the other hand, leu-ala is perhaps not a good indicator of intracellular digestion, while Lap may be a good indicator of the development of the BB membrane (Kvale et al 2007). In other studies, leu-ala levels failed to show the expected decrease in both halibut and cod, while the expected decrease of leu-ala was found in Senegalese sole (Solea senegalensis) and sea bass (Dicentrarchus labrax) between 20 and 30 days (Ribeiro et al 1999;Zambonino Infante and Cahu 2001). Our results are supported by those of Kvale et al (2007).…”