Recent developments in male fertility evaluation, sperm cryopreservation and artificial fertilisation, and their potential application to decapod crustacean aquaculture

To maximise productivity, a better understanding of the underlying causes of subfertility that lead to inferior offspring and high mortality is imperative. In decapod crustaceans, most research has focused on female reproductive performance, with little attention given to male fertility. Paternal genetic contribution is critical to both successful embryonic and post-embryonic development. Assessment of sperm quality can be a direct method to determine male subfertility in decapods. Sperm quality parameters such as sperm concentration and morphology have traditionally been used to determine male reproductive performance, but these procedures are time-consuming and can only assess a limited number of sperm cells and males. Alternative diagnostic biomarkers used widely in humans and other mammals could be adapted to decapod crustaceans and may be more indicative of sperm fertilisation competence and male reproductive performance. These predictive biomarkers use fluorescent cellular dyes and high-throughput flow cytometry or computer-assisted sperm microscopic analysis to evaluate sperm viability, mitochondrial function, acrosome reaction and DNA fragmentation. This review examines current and advanced biomarkers to evaluate sperm quality and further explores state-of-the-art procedures of sperm cryopreservation (conventional vs. vitrification techniques) and artificial fertilisation in decapod crustaceans. Sperm freezing coupled with artificial fertilisation in decapods permits the long-term storage, controlled timing and selection of individuals for reproduction. Collectively, these tools can be applied to commercial broodstock management to improve productivity and accelerate selective breeding in the crustacean aquaculture industry

Promoting responsible aquaculture for the sustainable production of soft-shell crabs

Soft-shell crabs command a high price because these could be eaten whole when cooked. Myanmar, Viet Nam, and Thailand are among the Southeast Asian countries that produce considerable quantities of soft-shell crabs mostly sold to local restaurants as well as exported to Australia, Europe, Hong Kong, Japan, Singapore, South Korea, Taiwan, and the USA. Production of soft-shell crabs is an emerging technology in the Philippines, where the demand for this product has been increasing and the technology becoming a growing interest. With prices that could range from US$10 to US$ 15 US$ or higher per kilogram depending on the size, soft-shell crabs are bought in bulk by elite restaurants in the Philippines that usually serve this delicacy with complimentary food or drinks. Although the demand for soft-shell crabs is high, production is still unstable due to lack of seedstocks, which are mainly sourced from the wild. To reduce the pressure on the natural population, SEAFDEC/AQD has initiated the development of soft-shell crab technology using hatchery-produced seedstocks, and is currently promoting the use of hatchery-produced seedstocks for soft-shell crab farming to local and international stakeholders all over the Southeast Asian region through its training courses. With funding support from the Philippine Council for Agriculture, Aquatic, and Natural Resources Research and Development (PCAARRD) of the Department of Science and Technology (DOST) through its National Mud Crab Science and Technology Program (NMCSTP), SEAFDEC/AQD has intensified the development of the soft-shell crab technology. Applicable to all mangrove (mud) crab species, the technology for the production of soft-shell crabs could now be pursued using hatchery-produced seedstocks is described in this article