Marosatherina ladigesi is an endemic ornamental freshwater fish in South Sulawesi, Indonesia1. This fish is locally known as “beseng-beseng”. M. ladigesi is at verge of extinction; reported by International Union for the Conservation of Nature2. Researchers have investigated almost all aspects regarding this particular fish. However, research on the development of embryonic and larvae of M. ladigesi has not performed yet.
Ontogeny stage of fish is mandatory to understand3 because the embryonic and larval developmental processes vary among different species4. Changes occur intensely in early stages of the life cycle during the hatching process and larval morphogenesis phase5.
A research was conducted to determine the ontology development stages of embryonic and larval M. ladigesi. For this purpose stocks of fish were reared for 5 months and on daily basis they were fed twice with mixture of Daphnia sp., Chironomus sp. and Culex sp. Water was exchange up to 50% each week. Artificial substrate from plastic rope was attached in the tank. The eggs were laid on the substrate after 6 hours. Eggs were collected and the feed including infusoria, Daphnia sp. and Artemiasalina nauplii was given to larvae daily; two times a day. Observations of embryonic development were performed every 6 h until the eggs hatched. At a time 5 eggs were observed. Larvae were observed at the ages of 0.3, 5, 7, 10, 15, 20, 25 and 30 days after hatching (DAH).
The process of embryonic development takes 204 hours after spawning (HAS) or 8.5 DAH. The cleavage stage is composed of 4-8 cell divisions that occur before 12 HAS, 16 cells formed at 12 HAS and 32-64 cells formed at 24-30 HAS, cell multiplication occurs after 36 HAS. The morula stage is 42 HAS, the blastula stage occurs at 54-60 HAS, the gastrula stage occurs at 72 HAS, the neurula stage begins at 84 HAS and the segmentation stage occurs at 96 HAS. The segmentation stage shows already formed eye spots. The yolk stage lasted until 5 DAH, the free flexion stage occurred at 7 DAH, the flexion phase at 10 DAH and the post flexion stage at 15 DAH. The mouth was open65-78 HAS or 3 DAH and the yolk reserves were used for 5 DAH.
This experiment revealed that the flexion stage happened after 10 DAH and the post flexion stage after 15 DAH. The mouth of fish was open after 65-78 h (3 DAH) and the yolk sac reserves were used for 5 DAH. Sufficient knowledge of the embryonic development in this species will help to find and study egg hatching rates. Moreover; better understanding of the stages of larval development can serve as a basis for rearing and feeding larvae for improving growth and survival as well.
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25 August, 2019