Journal of Survey in Fisheries Sciences 4(2) 5-25 2018 A review on the recent advances in the biology and aquaculture technology of Holothuria scabra Junus S.1*; Kwong P.J.1; Khoo G.2 Received: March 2017 Accepted: December 2017 Abstract The highly valued sea cucumber Holothuria scabra is currently listed as endangered (EN) species in the IUCN Red List due to overfishing in most of its native locations, spurring the development of H. scabra aquaculture to ensure sustainability of the industry and species in the wild. This review presents a summary on the biology of Holothuria scabra and recent advancements of its aquaculture technology. The life cycle, morphology and internal anatomy of H. scabra are discussed. Recent findings on the reproductive behavior and mechanism of the population are reviewed together with the possible factors that influence gamete maturation and spawning events. This review also covers the notable recent advances on H. scabra aquaculture technology such as the studies on broodstock diet which indicated bacteria and carbonate minerals to be the main diets; the favorable polyculture results of H. scabra juveniles with red tilapia and Kappaphycus striatum; and the discovery and subsequent patent of H. scabra oocyte maturation inducing substance prepared from sea urchin spawns. Keywords: Holothuria scabra, sea cucumber, echinoderm, broodstock, reproductive biology, aquaculture technology __________________________________________ 1-Department of Agricultural and Food Science, Faculty of Science, Universiti Tunku Abdul Rahman, 31900 Kampar, Malaysia 2-Department of Biological Science, Faculty of Science, Universiti Tunku Abdul Rahman, 31900 Kampar, Malaysia *Corresponding author’s Email: [email protected] 6 Junus et al., A review on the recent advances in the biology and aquaculture technology … Introduction The biology of H. scabra had been The sea cucumber Holothuria scabra studied extensively for decades; the Jaeger, commonly known as sandfish or earliest mention was in a literature by trepang, has become one of the highly Jaeger (1833, cited in Hamel et al., valued species in the food fish industry 2001). Yet for many years the existing since the 1980’s especially in the Asian information was not readily accessible market. It is currently valued at more to researchers due to the publication than USD1000 per kg dry weight, just a and language barriers. In 2001, Hamel little under the market value of et al. compiled many of the then Apostichopus japonicus, also dubbed existing references into one the Japanese sea cucumber. Therefore, comprehensive review on H. scabra. it is not surprising that H. scabra has The 16-year-old literature was a great become overfished in most of its natural help in the advancement of H. scabra habitats resulting in the species being research, either for fundamental studies listed as endangered (EN) under the or for the aquaculture application and International Union for Conservation of technology. A more recent review was Nature (IUCN) Red List (Purcell et al., compiled and edited by Brown and 2014). In Sri Lanka, the unregulated Eddy (2015) covering the advancement overfishing of sea cucumbers has of echinoderm aquaculture in general. resulted in the collapse of the industry This paper aims to present a current (Kumara et al., 2005), and fishing summary on the biology of H. scabra activities have recently been restricted and the advancement of its aquaculture to the north, east, and north-western technology and management in the past coastal waters (Dissanayake and sixteen years. Stefansson, 2012). Other countries like India (Sakhtivel and Swamy, 1994) and The Biology of Holothuria scabra Papua New Guinea have imposed a ban Taxonomy or moratorium on sandfish trading The holothurians can be grouped and (Purcell et al., 2014; Purdy et al., 2017) differentiated from other echinoderms in an effort to prevent the impending based on the existence of a calcareous collapse. The need to enhance the ring located anterior to the oesophagus natural stocks of H. scabra in its native as well as the buccal tentacles that location has helped to spur the extend out of the pharynx and serve as development of sea cucumber feeding apparatus. Unlike other aquaculture technology. Fortunately, echinoderms, the holothurians also just like the sea cucumber Apostichopus possess an outer skeleton (test) japonicus, its temperate counterpart, H. consisting of microscopic ossicles and a scabra is also one of the more well-developed haemal system. adaptable species for aquaculture Holothurians are further classified into production due to its biology and six orders based on the anatomy of the natural habitat (Hamel et al., 2001). Journal of Survey in Fisheries Sciences 4(2) 2018 7 calcareous ring, the shape and Natural Habitat arrangement of the ossicles, the number In his review, Hamel et al. (2001) and form of the buccal tentacles explained observations from various extending out of the mouth, and the researchers concerning the habitat presence of respiratory trees. Of the six preference of H. scabra. In its natural holothurian orders, only two orders are habitat across the region, adult H. known to be exploited commercially scabra is observed to prefer calm (Hamel et al., 2001; Slater and Chen, coastal areas with sandy muddy 2015). The minority comes from the substrate instead of coral reefs. They order Dendrochirotida, which is are also observed to be able to tolerate associated with 10 buccal tentacles. low salinities, and are sometimes even Only one species, Cucumaria frondosa, found near estuaries. A study by is commercially exploited within this Mercier et al. (1999a, b; 2000a) showed order mainly for the extraction of its the ability of H. scabra to tolerate as bioactive compound, frondoside A low as 20 p.s.u water salinity by (Takashi et al., 2005; Slater, 2015). burrowing into the sediment. The Most of the commercial sea cucumbers juveniles are also observed to prefer belong to the order Aspidochirotida, medium-sized grains (0.4 mm) as which has 18-30 buccal tentacles. substrate and areas where seagrasses Within the Aspidochirotida, the are plentiful, especially of the species commercially exploited sea cucumber Thalassia hemprichii and Enhalus comes only from two families, acoroides. Stichopodidae and Holothuriidae. In The sandfish H. scabra can be found terms of aquaculture production, there across various regions in the Indo- is only one species from each family Pacific which encompasses the latitude currently produced in aquaculture range of 30 N to 30 S (Massin, 1999; hatcheries namely the temperate species, Massin et al., 2009; Hamel et al., 2001). Apostichopus japonicus, and the warm Native populations have been studied in water species, Holothuria (Metriatyla) India, Sri Lanka, New Caledonia, scabra reported by Jaeger (1833). The Solomon Islands, Ecuador, Vietnam, taxonomic classification of H. scabra is Indonesia, the Philippines, Australia, as follows (Massin et al., 2009): Madagascar, and China (Hamel et al., Kingdom : Animalia 2001; Dissanayake and Stefansson, Phylum : Echinodermata 2012). Extensive aquaculture and Class : Holothuroidea farming systems of H. scabra have Order : Aspidochirotida been growing for the past 7 years and Family : Holothuriidae are currently on-going in Madagascar, Genus : Holothuria Philippines, Vietnam and Fiji which Species : scabra mainly supply the commercial demand (Hair et al., 2012; Purdy et al., 2017). 8 Junus et al., A review on the recent advances in the biology and aquaculture technology … Anatomy during handling, the incidence of The morphology and internal anatomy evisceration is more common among H. of Holothuria scabra had been covered scabra compared to other species extensively by various researchers, (Conand, 1989) cited in Hamel et al. most notably Bai (1971, 1978, 1980, 2001). and 1994), Conand (1989 cited in Bai (1980) revealed that the Hamel et al., 2001), James (1989), and digestive tract of H. scabra, comprising Baskar (1994). The species is usually the oesophagus, stomach, small and identified by its smooth, elongated large intestines, is supported by a tubular body along the oral-aboral axis, mesentery. The digestive tract ends into being gray or black at the convex dorsal a wide cloacal chamber that terminates side, and always white and flat at the at the anus (Slater and Chen, 2015). ventral side. The dorsal body is There is currently no detailed study on sometimes peppered with speckles of the physiology of digestion and black, yellow and/or white patterns. nutritional requirements of H. scabra. The white ventral side is usually The respiratory system of H. scabra peppered with black or brown dots is an intricate network of tubules or which are the tube feet. Located vessels formed from the cloacal wall in ventrally at one end of the tubular body one common main stem that branches is the oval mouth encircled by 20 to the left and right into many finer tentacles (Conand, 1989 cited in Hamel branches. Two or three shorter branches et al., 2001). At the opposite end of the may also form out of the base of the body and located somewhat dorsally is common stem. This network of tubules the anus or cloaca which rhythmically is the respiratory tree that terminates pumps water in and out of the body. into the perivisceral coelom and are The creeping movement of H. scabra is always covered in coelomic fluid (Bai, regulated by five pairs of muscular lines 1980; Slater and Chen, 2015). The along the body length (Bai, 1980). cloaca also plays an important role in The internal anatomy or viscera of H. the respiratory system by drawing sea scabra consists of two tubular branches water in and out of the cloacal chamber of gonads with one end connected to and respiratory trees with its rhythmical the gonopore, the digestive organs pumping (Bai, 1980). Gas exchange which end with the anus, and occurs through the thin tubular wall into respiratory trees. H. scabra is able to the coelomic fluid that is circulated eviscerate most to all of its digestive around the body through the water and respiratory organs as a method of vascular and haemal system.