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Embryonic and Larval Development of Thai Pangas Pangasianodon Hypopthalmus (sauvage, 1878) Under Hatchery Condition

B. K. Chakraborty
Department of Fisheries, Bangladesh and Culture of Mud Eel, Mud Crab, Aquaculture and Management Centre, Mymensingh, Bangladesh

D. K. Jha
Agriculture and Forest University, Rampal, Nepal

Abstract/ Executive Summary:

The embryonic and larval development of Pangasianodon hypophthalmus was investigated during peak spawning periods (May-July 2019). The fertilized eggs were adhesive and spherical with a greenish-brown egg capsule. The yolk sac was yellowish-brown in color and 1.00–1.70 mm in diameter. The first cleavage stage, embryonic shield, head, tail region, neural grooves, and somites were apparent after fourteen hours postfertilization. The ranges of incubation period were from 18.00- 20.00 hrs at a temperature of 26-30°C. The newly hatched larvae were transparent and light yellowish in color with a body length of 2.98–3.10 mm. Eye pigment appeared and the heart started to work within 12-16 hrs of hatching. The mouth became well developed at the age of 24 hrs; barbules were prominent, elongated, and look like threads. The yolk sac was fully absorbed and the palatine teeth were fully increased during the 3-day prolarval stage. The stomach became functional and aerial respiration started after 3 days of larval development. After 72 hrs, the young fry was well-developed and appeared an adult, and length was measured up to 7.20±0.02 mm. When the daily ration of pangas larvae is insufficient cannibalism was recorded. This study must be supportive for researchers and nursery owners on the biology and ecology of the fish, which might be helpful for the appropriate measure of the sustainable nursery, rearing, and management technology of pangas.

Keywords: Embryonic development, Larval development, Blastula, Gastrula, Organogenesis, Pangas

Location: Satota hatchery, Trisal, Mymensingh.

Start Date: 00-05-2019

End Date: 00-07-2019

Program Area: Variety and Species

Commodity: Pangus

Objectives:

To find out the early life cycle from oocyte activation to the beginning of the adult fry of pangas under hatchery conditions.

Methodology:

The experiment was studied in the Satota hatchery, Trisal, Mymensingh. Embryo inherent and larvae development were observed in two trials using two pairs of male (3.5-4.5kg) and female (3-4kg) broodstocks of P. hypophthalmus fish. The fertilization rate was estimated according to the novel method proposed by Okomoda et al.(2017). An early developmental stage of P. hypophthalmus was observed up to 76.00 hrs starting from egg fertilization. The eggs were collected randomly from the hatching jar. The developing stages of P. hypophthalmus were observed at every 5 to 10 mins interval till completion of the morula stage and then after every one-hour interval up to hatching. The eggs were kept in a 70% ethanol solution for preservation for the next observation. At least 15 eggs undergoing the embryonic development process were studied to get accurate information. The larval samples were also collected from the hatching jar and hapa. Initial samples were collected hourly. At least ten larvae were collected and immediately put into 70% ethanol solution for further study. The collected larvae were examined as soon as possible. Early developmental stages were observed under a Stereomicroscope (Olympus, SZH10 Research Stereo). At each developing stage, ten individuals were tested for confirmation of different stages and the timing of development. All the stages of development were observed at every 5 to 10 mins interval till the completion of morula and then after every one-hour interval till completion of organogenesis. The sketches of every developmental stage were drawn by hand using Camera Lucida (Olympus, Japan 306681) fixed on a Stereomicroscope (Olympus, SZH10 Research Stereo). Every developmental stage of fish larvae was temporarily stained with methylene blue for clear observation. Young fry was fed on freshly hatched nauplii, Artemiasalina during 1-4 days, and Tubifex worms and powdered dry food during 5-14 days.

Source of Information: Bangladesh J. Zool. 49 (1): 147-159, 2021

Article Link (Online Journal): DOI: https://doi.org/10.3329/bjz.v49i1.53690

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

The embryonic and larval developmental stages of the P. hypothalamus show significant and rhythmic development. Cannibalism is a common criterion of catfish, which also exhibits in pangas larvae when food is insufficient. Temperature is inversely related to the incubation and hatching periods of pangas. The notochord is gradually extended up to the caudal region of the hatchlings by the seventh day of successive developmental periods. Considering all the facts and findings of the experiment the present provides information on the early development stages of P.hypophthalmus. The present study has generated some information on the early life history, developmental stages, and commencement of first feeding time for larval rearing. This study will be helpful to the fishery biologists in understanding the biology and ecology of the fish, which might be of great opportunity to take appropriate measures for sustainable culture and management technology of pangas.

Knowledge Management: Journal