Upaya peningkatan kelangsungan hidup larva ikan betok, anabas testudineus bloch melalui studi ontogeni saluran pencernaan, kemampuan biosintesis HUFA dan pengkayaan asam lemak esensial

Abstract

Climbing perch Anabas testudineus (Bloch) is commercially valuable fish species and representing a great of interest for aquaculture in Kalimantan, Indonesia. However, limited success on larval rearing of the fish has been obtained. Thus, the aim of the study was to increase survival rate of the larvae through evaluations on: ontogeny of digestive system, ability of HUFA biosynthesis, and enrichment of essential fatty acid. Development of digestive system was evaluated in larvae reared from hatching to 30 days after hatching using histological and morphological methods, and biochemical techniques. PUFA to HUFA biosynthesis ability was evaluated in fish using analysis of gene expression encoding enzymes involved in HUFA biosynthesis, and fatty acid profile. Development of the digestive tract in climbing perch followed the general pattern described for other species. At hatching (D0), it consisted of an undifferentiated straight tube laying dorsally to the yolk sac. At first feeding (D2), the digestive tract was fully differentiated into buccopharynx, esophagus, intestine and rectum with opened mouth and anus, and almost digestive enzymes were detected. The activities of all the enzymes remained stable from D25 onwards, coinciding with the formation of pyloric caecum. The enzymatic equipment of the larvae was completely efficient up to D25 and since then formulated feed could be offered. Moreover, the results showed that the fatty acid elongase and desaturase genes expression level was increased in the 12-day larvae fed on corn and the candle nut oil-enriched rotifers. This suggested that the elongase and desaturase enzymes were involved in HUFA biosynthesis. Results also indicated that the larvae fed by enriched rotifer with vegetable oil emulsions had higher survival rate than that of fed by non-enriched in control treatment. The highest survival rate of larvae was obtained in treatment D with ratio 1:1 of the corn and candle nut oils. In this treatment, concentration of docosahexaenoic acid (DHA; 10.33%) and arachidonic acid (ARA; 6.20%) was higher compared to the other treatments. It is most likely that DHA and ARA play important role on survival of the larvae. Therefore, the corn oil and the candle nut oil with a ratio 1:1 could be used to provide high performance of climbing perch larvae.