Early development of the digestive tract of cod larvae, Gadus morhua L., during start‐feeding and starvation

Abstract

Cod larvae, Gadus morhua L., were reared in the laboratory and released to a large marine enclosure4 to Sdaysafter hatching(6-8" C). Thedevelopment ofthedigestive system was studied until day 24 after hatching. Morphological investigations of the jaw apparatus and the digestive tract showed that the larvae are able to absorb ingested food well before exhaustion of the yolk sac. The foregut, and especially the midgut, were particularly active in lipid absorption, and the hindgut was characterized by pinocytotic activity. During the first days of feeding, no distinct prey organisms were observed in the gut. and signs of food absorption in the epithelial cells of the gut were sparse. A distinct red fluorescence, restricted to the hindgut, was observed from day I 1 to day 19. On the basis of changes in absorptive pattern in the gut we suggest that changes in digestive and absorptive abilities, as well as in nutritional needs, take place around days 15-17 after hatching.In starved larvae, signs of degeneration of the gut tissue were first visible in the foregut. By day 9 after hatching, microvilli was degenerated to such an extent that the ability to absorb food must have been severely restricted. Iflarvae are starved longer than this, they will probably not survive.

Pools and rapids as spawning and nursery areas for fish in a river stretch without floodplains

“…Because most of the larvae found in this environment had some vestige of yolk, it can be inferred that the low degree of stomach repletion of larvae in the rapids is because the larvae they are still feeding endogenously. During the first days after eclosion, larvae feed through the endogenous yolk sac and the gradual depletion of this reserve or full nutrition causes the larva to seek an exogenous food source (Kjorsvik et al, 2006). Consequently, it is possible to infer that the local growth of larval fish should be environments where biological and physicochemical conditions are appropriate for the growth of their larvae, with food availability both for their development and their feeding (Reynalte-Tataje et al, 2008b).…”

Yolk utilization and growth during the early larval life of the Silver Perch, Bidyanus bidyanus (Mitchell, 1838)

“…Fish larvae are also highly vulnerable during the period of transition from consuming endogenous reserves of food to exogenous nutrient consumption. Failure to perform first feeding response immediately when the mouth has opened often causes morphological deformities, abnormal moving behaviour, and an inability to swim and feed (Gwak and Tanaka 2001;Kjørsvik et al 1991), leading to high mortality (Dou et al 2002;Houde 1974).…”

On the edge of death: Rates of decline and lower thresholds of biochemical condition in food-deprived fish larvae and juveniles

“…Still, RD is not usually considered an indicator of starvation because some life stages and species can compensate for extended periods of food deprivation, either by catabolizing energy reserves within muscle and liver tissue or by utilizing embryonic yolk reserves, sometime leading to ambiguous patterns in changes in RD. Direct methods to describe and quantify the phenomenon of starvation have included observations on feeding success (gut content) (Bochdansky et al, 2008), measurements of otolith microstructure (Johnson et al, 2002), and histological examination of digestive tissues (Kjørsvik et al, 1991;Theilacker and Watanabe, 1989). However, the potential influences of life stage and/or species relationships on nutritional deficiency, RD, and starvation in marine fish early life stages are not yet clarified.…”