Adequate genetic information is essential for sustainable crustacean fisheries and aquaculture management. The commercially important orange mud crab, Scylla olivacea, is prevalent in Southeast Asia region and is highly sought after. Although it is a suitable aquaculture candidate, full domestication of this species is hampered by the lack of knowledge about the sexual maturation process and the molecular mechanisms behind it, especially in males. To date, data on its whole genome is yet to be reported for S. olivacea. The available transcriptome data published previously on this species focus primarily on females and the role of central nervous system in reproductive development. De novo transcriptome sequencing for the testes of S. olivacea from immature, maturing and mature stages were performed. A total of approximately 144 million high-quality reads were generated and de novo assembled into 160,569 transcripts with a total length of 142.2 Mb. Approximately 15–23% of the total assembled transcripts were annotated when compared to public protein sequence databases (i.e. UniProt database, Interpro database, Pfam database and Drosophila melanogaster protein database), and GO-categorised with GO Ontology terms. A total of 156,181 high-quality Single-Nucleotide Polymorphisms (SNPs) were mined from the transcriptome data of present study. Transcriptome comparison among the testes of different maturation stages revealed one gene (beta crystallin like gene) with the most significant differential expression—up-regulated in immature stage and down-regulated in maturing and mature stages. This was further validated by qRT-PCR. In conclusion, a comprehensive transcriptome of the testis of orange mud crabs from different maturation stages were obtained. This report provides an invaluable resource for enhancing our understanding of this species’ genome structure and biology, as expressed and controlled by their gonads.

This study investigated the use of electric-shock in inducing triploidy in African catfish Clarias gariepinus. To achieve this, three voltages (9, 12, 21 V) were applied for different durations (3, 5, 10 min). the shock was initiated approximately three minutes after fertilization followed by incubation in ambient temperature. After incubation, hatchability and survival rates were determined while ploidy status of the treatment fishes was confirmed in one-month-old fingerlings using the exclusive triploid range of the erythrocyte major axis previously reported for the same species (11.9-14.9 μm) and by cytogenetic analysis of the chromosome. The results showed triploidy were achieved in 10 to 85% of the treatment groups. A consistent trend of decrease in hatchability and an increase in triploidy rate was observed with increased electroporation voltages and shock durations. The mean erythrocyte major axis length of triploid progenies (3n = 84) was observed to be between 11.3-14.6 μm and was higher than the range of 7.0-10.5 μm recorded for diploid progenies (2n = 56). It was concluded that electric shock can be used to induce triploidy in African catfish C. gariepinus.

Several scientific methods have been described in the identification of triploid fish. However, many of these methods are not applicable for routine management purposes due to their complexity and cost. In this study, the possibility of using morphological variation as a least cost and less complex method of distinguishing triploid and diploid African catfish Clarias gariepinus (Burchell, 1822) was examined. Triploid catfish were produced by cold shock of fertilized eggs in 5°C for 20 mins (at approximately 3 mins after fertilization). The fish were incubated, hatched and raised for 3 months. Ploidy levels of the fish were then ascertained by observing the erythrocyte shape. Triploid erythrocyte was ellipsoidal in shape while diploid was round. Morphological characterization was then carried out on 100 samples each of triploid and diploid African catfish. Although significant differences were observed in many parameters, the principal morphometric difference between triploid and diploid African catfish could not be clearly distinguished. It was therefore concluded that morphological characteristics is not ideal for discriminating triploids and diploids of African catfish. The used of erythrocyte characteristics still remains the cheapest and relatively effective method for triploid and diploid determination in African catfish.

Cryopreservation of spermatozoa of grouper species supporting artificial insemination in production of fry has contributed to the grouper aquaculture industry. Grouper is a high‐value species in marine cage finfish culture and a major business for the aquaculture industry in South East Asia. The species contributes a significant value to the income of South East Asian countries such as Indonesia, Malaysia, Philippines and Thailand. Hybrid grouper is a new candidate for marine finfish culture, and cryopreservation of grouper and giant grouper spermatozoa is important to support development of its production. This review article discusses the cryopreservation of the spermatozoa of grouper species specifically. Emphasis is placed on the protocols for implementation and implications of the cryopreservation of grouper spermatozoa in the marine finfish aquaculture industry.

To obtain well spread chromosomes, the cytogenetic protocol for Pangasianodon hypophthalmus and Clarias gariepinus were optimized. This includes, the colchicine concentration (0.01%, 0.025%, 0.05%)/exposure duration (1, 3, and 5 h), hypotonic solution (distilled water or 0.075M KCl solution)/exposure duration (30 min, 1, and 2 h), the time of cell suspension preparation (at hypotonic treatment or before slide preparation) and chromosome aging period (0, 3, and 7 days in Carnoy’s fixative). In addition, the type (i.e., fin, gill or kidney) and the amount of tissue (10, 50, 100 or 150 mg) were also investigated. Regardless of the species, the result obtained showed that well-spread chromosomes could be obtained using the following optimized protocol: Juveniles are injected with 0.05% colchicine (at one ml kg−1) and allowed to swim for 3 h. Then, 50 mg of gill tissue is made into cell suspension in 0.075M KCl for 1 h. The cell suspension is treated in Carnoy’s fixative (changed three times at 20 min interval) and then aged for 3 days. Finally, chromosome slides are made and stained with 10% Giemsa for 1 h.