Embryonic and larval development of an endemic Lake Tana barb, Labeobarbus brevicephalus (Teleostei: Cyprinidae)

Abstract

The present study is a description of the embryonic and post-embryonic development of Lake Tana endemic barb species, Labeobarbus brevicephalus, from fertilization until active feeding. Bouin’s solution immersed and unfertilized egg diameter ranged from 1.63 to 1.93 mm. The first cleavage occurred within 60-minute post-fertilization at a temperature of 23.0–25.8°C. Yolk invasion was completed by gradual spreading over the germ layer at 20 h. At about 43 h, the embryo occupied more than ¾ of the egg peripheral space. The heart was beating actively and the blood circulation was visible. Yolk sac was restricted to the head region, embryos became active and exhibited continuous twitching movement. Hatching was synchronous, started 58 h + 30 min post-fertilization and was completed within 65 h at the same temperature range. Average total length of newly hatched larvae was 5.06 ± 0.16 mm (mean ± SE, n = 5). The overall embryonic and post-embryonic development of Lake Tana L. brevicephalus were completed in eight days time. By this time post-fertilization larva began active feeding and had well developed cartilaginous neurocranium, most of the bony elements in splanchnocranium, pigmentation on the head, eyes and body, cartilaginous pectoral fin and pectoral fin girdle with single bony element cleithrum, reduced fin fold, developed cartilaginous support and several ossified fin rays in unpaired fins. The information obtained from this study will be useful to cover gaps in early life history, first feeding and ontogeny of L. brevicephalus for its conservation and restoration.

Keywords/phrases: Conservation, Labeobarbus brevicephalus, Lake Tana, Ontogeny, Post-fertilization, Yolk invasion