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Embryology and Early Ontogenesis of the Threatened Menoda Catfish, Hemibagrus Menoda (hamilton, 1822)

Ibrahim Shehu Jega
Department of Fisheries Management, Bangladesh Agricultural University, Mymensingh, Bangladesh

Abdullah Omar
Department of Fisheries Management, Bangladesh Agricultural University, Mymensingh, Bangladesh

Md. Idris Miah
Department of Fisheries Management, Bangladesh Agricultural University, Mymensingh, Bangladesh

Mohammad Mahfujul Haque
Department of Aquaculture, Bangladesh Agricultural University, Mymensingh, Bangladesh

Md. Shahjahan
Department of Fisheries Management, Bangladesh Agricultural University, Mymensingh, Bangladesh

Abstract/ Executive Summary:

Knowledge of the early life stages of fishes portrays the morphological changes they undergo during embryogenesis and early ontogenesis which aids in their culture and preservation. This study investigated the embryonic and larval development of the menoda catfish, Hemibagrus menoda from fertilization to post-hatching. The ovulated eggs were placed in convex slides and the embryonic and larval developmental stages studied under the microscope. Unfertilized eggs were sticky, mean egg diameter increased from 0.8 ± 0.00 mm to 1.10 ± 0.01 mm after fertilization. The cleavage stage occurred within 2. 50 hr and hatching occurred at 19.30 hr after fertilization at 24.1 0C water temperature. Newly hatched larvae were curved, laterally compressed with the body gradually tapering towards the tail and measured 3.0 ± 0.02 mm. The egg yolk became completely absorbed within 68 hours at mean length of 6.5 ± 0.05 mm. Findings from this study might aid in the development of an appropriate culture program for this species hence preventing its extinction.

Keywords: Hemibagrus menoda; Embryonic development; Early ontogenesis; Conservation

Location: Kangsha River Netrakona, Bangladesh

Start Date:

End Date:

Program Area: Animal Health and Management

Commodity: Cat fish

Objectives:

Some research has been conducted on the early life development of some species in the genus Hemibagrus. Recent studies on H. menoda were confined to sex ratio, length-weight relationships and condition factor and its food and feeding habits. In this study, the embryonic development and early ontogenesis of the threatened H. menoda was investigated.

Methodology:

2.1 Broodstock collection and culture Samples of H. menoda were obtained from Kangsha River Netrakona, Bangladesh and taken to the hatchery unit of the Field Laboratory Complex, Faculty of Fisheries, Bangladesh Agricultural University, Mymensingh where the fish were kept in circular tanks for 7 days with continuous water showering for acclimatization. The broodfish were stocked for nine (9) months in rectangular brood-rearing earthen ponds (10 x 4.6 m²) and fed twice daily with trash fish (protein 20.6±0.6%, lipid 6.3±0.7%, ash 1.3±0.1%, moisture 70.5±2.6% and carbohydrates 1.3±0.2%) at 3% body weight. Ready to spawn gravid females and males were selected and injected intramuscularly with PG extract then released into breeding hapa placed in tanks for synchronized spawning at 1:2 ratio.

2.2 Collection of egg and larval samples About 50 fertilized eggs were randomly collected using an enamel plate from the breeding hapa and placed in a rectangular hatching tray (85 x 40 x 12 cm) with continuous water flow. Using an ocular micrometer attached to the eyepiece of the microscope and a stage micrometer on the slide panel, the development of the embryo was checked at intervals of 0, 5, and 10 minutes from fertilization to last stage of cleavage, 30 minutes from morula to late blastula and after every one hour from early gastrula to hatching. A minimum of 10 eggs undergoing embryonic development process were examined by placing in a convex slide containing distilled water. Larval samples were collected from the hatching tray first at 1 hr interval and subsequently, the time interval increased. Minimum of 6 larvae were occasionally immobilized with 10% formalin before being examined under the microscope.

2.3 Observation of developmental stages The larval development time and total length (TL) from hatching were recorded to the nearest minute and mm, respectively. The TL of the larvae was taken by placing the larvae on a Petri dish with a graph paper attached beneath. The images of morphological changes in the larvae in each day were captured through a camera attached to a compound microscope (Olympus Lab EC 20X ~1500X) and specimens labeled accordingly.

Source of Information: International Journal of Fisheries and Aquatic Studies 2018; 6(5): 225-230

Article Link (Online Journal):

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

Study of embryonic and larval development of H. menoda revealed that hatching occurred within 19.30 hrs af at 24.1 ⁰C, and the yolk sac of the hatched larvae was completely absorbed within 68 hours af at mean length of 6.5 ± 0.05 mm, which is a shorter time than in other catfishes like Mystus montanus and Carassius carassius. Identification of time for first feeding is very critical and prevents loss of fry to the farmer due to cannibalism and death.

Knowledge Management: Journal