Ontogeny of the Digestive System of the Red Snapper Lutjanus campechanus

Citation

Bardon-Albaret A, Leclercq E, Brown-Peterson NJ, Apeitos A & Saillant EA (2013) Ontogeny of the Digestive System of the Red Snapper Lutjanus campechanus. World Aquaculture Society Meetings 2013, Nashville, Tennessee, USA, 22.02.2013-25.02.2013. https://www.was.org/meetings/ShowAbstract.aspx?Id=28666

Abstract
The ontogeny of the digestive system of red snapper (Lutjanus campechanus) under intensive aquaculture conditions was histologically described. Larvae were fed a sequence of copepods (Acartia tonsa) from 2 days post hatch (dph) and enriched artemia (Artemia salina) beginning at 15 dph. Complete transition to inert food was achieved at 33 dph. Water temperature was initially 25.5and was progressively increased to 27.5Larvae were sampled from hatching to 31 dph to allow description of the morphological development of the digestive system. At each of the 11 sampling dates (every day from hatching until 5 dph, then 9, 12, 18, 24 and 31 dph), two samples of 30 larvae were collected from at least two different replicate tanks. Starting at 9 dph, larvae were sorted by size in three classes (small, medium and large) to evaluate differential development of larvae having reached different sizes at the same age. Larvae were embedded in paraffin and sectioned longitudinally at 3-5 thick for observation of structural changes during their ontogeny. Results showed that under current culture conditions, red snapper hatch as a rudimentary larva with a single gut and no major digestive organs. The mouth opens at 3 dph, when the incipient gut differentiates into foregut, midgut and hindgut with no trace of any remaining endogenous feeding material. The gill cavity contains four clusters of branchial arches. Liver, pancreatic tissue and swimbladder are small but already present. At 5 dph, the swimbladder starts to inflate with gas gland and rete mirabile visible; swimbladder inflation is completed at 9 dph. The digestive tract forms a loop observed at 9 dph in the larger specimens. The intestinal walls thicken and fold more intensively in all the 12 days old fish. Gastric glands were visible in larger fish at 18 dph. At 24 dph, all size fish showed developing pyloric caeca and gastric glands. Metamorphosis was completed at 31dph. The definition of the major developmental changes during the ontogeny of the red snapper larvae will help developing appropriate feeding protocols during this challenging phase of red snapper aquaculture.