Development of the digestive system in larval yellowtail (Pleuronectes ferruginea) and winter flounder (Pleuronectes americanus)

Yellowtail (Pleuronectes ferruginea) and winter (Pleuronectes americanus) flounder are two pleuronectid species that are considered aquaculture candidates in Atlantic Canada. Rearing practices typically use zooplankton that is costly and time consuming to maintain. Weaning to an artificial diet is successful only after several weeks of development. The ability to digest artificial diets and their effect on larval survival, growth and development is not well understood. This study provides information about digestive system ontogeny in both species reared on live food, weaned at day 15 or starved. The objective was to examine the morphological and functional status of the developing digestive tract and determine if different feeding regimes induced diet-related modifications of enzymatic activity.

Digestive tract ontogeny of larval yellowtail flounder fed a live diet was studied using light microscopy and mucous histochemistry.

Digestive enzymes were studied in yellowtail and winter flounder larvae reared on three different diets using enzyme histochemical methods. Analysis was based on semi-quantitative ranking of color intensity. Specimens were freeze-dried and embedded in glycol methacrylate. Results suggest that by the time the larvae begin feeding exogenously (7 days post hatch), the digestive system is able to process live food. (Abstract shortened by UMI.).