Histological and histochemical changes in the digestive tract of white sturgeon larvae during ontogeny

Abstract

Ontogenetic changes in digestive tract histology and digestive enzyme histochemistry were investigated 11 to 36 days post-hatch in white sturgeon Acipenser transmontanus larvae. From initiation of exogenous feeding (12 days post-hatch), larvae were fed a commercial salmonid diet for the ensuing 24 days. The digestive system of white sturgeon displayed a high degree of morphologic organization and functionality at the onset of exogenous feeding. An enhancement of digestive capacities occurred with transition to active feeding. On day 2 of feeding, there was a clear increase of alkaline phosphatase, aminopeptidase M, dipeptidyl peptidase IV, and γ-glutamyl transpeptidase activity in the brush border of the spiral intestine. This strong activity is an apparent confirmation of the importance of this segment of the intestine for protein digestion and nutrient absorption. The functional development of the pyloric intestine occurred on day 4 and was concomitant with an increase in the activity of brush border and cytoplasmic enzymes such as acetylcholinesterase, dipeptidyl peptidase II, α- and β-galactosidases. The absence of acetylcholinesterase, lactase, nonspecific esterase, and weak activity of exopeptidases and alkaline phosphatase in the anterior intestine suggests that this segment of the intestine may be less important in nutrient absorption than the pyloric and spiral intestines. The observed quantitative and qualitative differences in enzyme activity along the intestine indicate a high degree of specialization of each segment for specific digestive and absorptive processes.

Ontogenetic development of digestive enzymes and effect of starvation in miiuy croaker Miichthys miiuy larvae

“…These results suggest that the newly hatched miiuy croaker larvae, like other fish species, can synthesize digestive enzymes to digest and absorb nutrients without diet stimulation (Gawlicka et al 2000;Alvarez-González et al 2006;Chen et al 2007). Digestive enzymes in fish commonly undergo major developmental changes during the first weeks of life, which is characterized by a succession of increases and decreases in activity with age (Ferraris et al 1987;Boulhic and Gabaudan 1992;Gawlicka et al 1995Gawlicka et al , 1996Gawlicka et al , 2000Gisbert et al 1998Gisbert et al , 2004Hoehne-Reitan et al 2001). This developmental pattern varies with species and is affected by larval growth or the functioning of digestive organs.…”

“…Alkaline phosphatase is mainly distributed in the striated border of the epithelial cells in the foregut and is associated with nutritional absorption in the intestine (Buddington and Diamond 1989;Suzuki 1996, 1998). Its activity could thus be regarded as an index of the absorptive ability of fish larvae (Cousin et al 1987;Gawlicka et al 1995Gawlicka et al , 2000Baglole et al 1998). The activity of this enzyme in fish larvae is species specific and generally shows a developmental pattern of either continuous increase (Comabella et al 2006) or a succession of increases and decreases (Alvarez-González et al 2006;Chen et al 2006a) with age.…”

Digestive enzyme activity during early larval development of the Cuban gar Atractosteus tristoechus

“…This pattern of early and high acid protease activity is indicative of the presence of a functional stomach and gastric glands early in development. Examples of this pattern have only been observed in few species, such as salmonids and sturgeons (Buddington 1985;Buddington and Dorshov 1986;Gawlicka et al 1995), pintado (Lundstedt et al 2004), and alligator gar (A. spatula), with the latter possessing a well-developed intestinal tract characterized by a functional stomach and the secretion of pepsin-like enzymes from the beginning of exogenous feeding and before complete absorption of the yolk sac (Mendoza et al 2002a). According to some authors, stomach differentiation is a decisive event in larval fish nutritional physiology, leading to precocious behavior and efficient protein digestion (Segner et al 1994;Martínez et al 1999).…”

Osmoregulation in juvenile Chinese sturgeon (Acipenser sinensis Gray) during brackish water adaptation

“…These changes of the spiral valve Na + -K + -ATPase activity indicate that Chinese sturgeon exposed to isoosmotic media may ingest water in order to compensate for the osmotic water losses, as Kirsch et al (1984) reported for euryhaline teleost species. This reduction in the spiral valve Na + ,K + -ATPase activity, however, also compromised intestinal nutrient absorption, since the spiral valve is the main site of intestinal absorption in sturgeons (Gawlicka et al 1995), directly affecting fish nutrition and growth performance (Morgan and Iwana 1991). Rodriguez et al (2002) showed that A. baerii exposed to isosmotic and hyperosmotic media were unable to grow normally and had actually lost weight in hyperosmotic media.…”