SPC Beche-de-mer Information Bulletin #23 – February 2006 35

Asexual reproduction by induced transverse fission in the sea cucumbers marmorata and atra A. Laxminarayana1

Introduction weights of the anterior parts of H. atra were 86.7 g and 39.5 g in the first and second experiments. The Although holothurians are known for their ability mean weights of posterior parts of H. atra in the to reproduce asexually by fission, specific data on first and second experiments were 120.2 g and this subject is scarce. Approximately 10 of 52.5 g. The mean weights of anterior parts of sea cucumbers have been reported from field and B. marmorata were 42.8 g and 50.5 g in the first and laboratory observations to reproduce asexually second experiments, respectively. The mean (Emson and Wilckie 1980; Conand 1989, 2004; weights of posterior parts of B. marmorata in the Uthicke 2001a,b). Some of the species that repro- first and second experiments were 61.7 g and duce asexually in the field are: Holothuria atra, 72.8 g. All anterior and posterior halves were intro- H. parvula, H. edulis, H. leucospilota, mau- duced into one-tonne fiberglass tanks provided ritiana and Stichopus chloronotus. Other studies pre- with about 15 cm of sand. The sea cucumbers were sent experimental induction by constriction (Re- fed daily with seaweed paste/powder. ichenbach and Hollway 1995). In the present study, the sea cucumbers Bohadschia marmorata and H. atra Figure 1 shows the area of constriction before cut- were induced to reproduce by transverse fission by ting H. atra into two, slightly anteriorly (45%) to the cutting them slightly anteriorly to the middle por- middle portion of the body. Figure 2 shows the pro- tion (45%) of the body. cess of cutting H. atra into two halves; Figure 3 shows the two cut portions after they regenerated. Materials and methods The survival and weight of the sea cucumbers were This study was carried out at the Albion Fisheries monitored up to 373 days in the first experiment, Research Centre in Mauritius. The sea cucumbers and up to 288 days in the second experiment. The B. marmorata and H. atra were collected from the mean weights of sea cucumbers were calculated wild during low tide or by free diving from August from the total final weights of the sea cucumbers at to December 2004. The sea cucumbers were main- the end of the experiments. The results of the tained in one-tonne tanks containing about 15 cm growth of asexually reproduced sea cucumbers are of sand. The tanks were aerated with an air-blower. summarised in Tables 1 and 2. Water in the tanks was changed every day and the sand was changed once every two weeks. The sea The experiments were conducted from October cucumbers were fed with seaweed powder. 2004 to October, 2005. The water temperature vari- ation during the period of study was 24.5–28 °C. Two experiments were conducted. In the first exper- Salinity varied from 34–36 ppt and pH varied from iment, 6 H. atra and 4 B. marmorata were studied, 8.1–8.4. and in the second experiment, 10 H. atra and 20 B. marmorata were examined. The total initial Results weights of H. atra were 1387.0 g in the first experi- ment, and and 961.0 g in the second experiment. The In the first experiment, all the posterior and anterior total initial weights of B. marmorata used for the first halves survived in both species. The mean weights and second experiments were 440.0 g and 2609.9 g, for H. atra were 447.6 g and 280.4 g in the first and respectively. The mean weight of H. atra for the first second experiments, respectively. The mean weights and second experiments were 216.7 g and 96.1 g, of B. marmorata were 304.0 g and 286.0 g in the first and the mean weights of B. marmorata were 110.0 g and second experiments. The growth per day was and 130.5 g in the first and second experiments. 0.62–0.64 g for H. atra in the first and second experi- ments, and growth per day for B. marmorata was The sea cucumbers were cut into two after making 0.52 g–0.54 g in the first and second experiments. In a constriction slightly anterior (45%) to the middle the second experiment, survival rates after 288 days portion of the body. The total weights of the ante- were 95% and 92.5% for H. atra and B. marmorata. In rior and posterior parts were recorded immedi- the second experiment, initial mortality was noted ately after induced transverse fission. The mean during the first two days after duplication of the sea

1. Ministry of Fisheries, Albion Fisheries Research Centre, Petite Rivière, Albion, Mauritius. Email: [email protected] 36 SPC Beche-de-mer Information Bulletin #23 – February 2006

cucumbers. All of the four pieces that died were the anterior portions of the cut ends of the body. After two days of duplication, the body wall had its nor- mal consistency and wounds at both the ends were healed and entirely closed.

Discussion Asexual reproduction in sea cucumbers by fission has been studied by several researchers (Emson and Wilckie 1980; Emson and Maldenov 1987; Conand Figure 1. Area of constriction before cutting 1989, 1993, 1996; Conand and Ridder 1990; Chao et Holothuria atra al. 1993; Reichenbach and Hollway 1995; Boyer et al. 1995; Reichenbach et al. 1996; Uthicke 1997, 1998, 2001a, b; Conand and Uthicke 2001; Howaida et al. 2004). Asexual reproduction in nature is a seasonal event mainly occurring in winter in natural popula- tions. Most holothurian species with asexual repro- duction follow the ”twisting and stretching” mode (Emson and Wickie 1980; Uthicke 2001a, b); the an- terior and posterior sections rotate in opposite di- rections, resulting in a constriction in the holo- thurian. In the second step, the two halves slowly move in opposite directions until the body wall tears at the constriction and the two halves become Figure 2. Process of cutting H. atra into two halves completely separated. This process of asexual re- production by transverse fission was noted in natu- ral populations of H. atra by Chao et al. (1993), Co- nand and Ridder (1990), Boyer et al (1995), Conand (1996) and Uthicke (1997, 1998, 2001a, b). Reichen- bach and Hollway (1995) described the asexual propagation potential of several commercially im- portant species of sea cucumbers. Asexual repro- duction was observed in H. edulis and Stichopus chloronotus (Uthicke, 1997, 1998, 2001a, b). Howaida et al. (2004) conducted experiments on the asexual reproduction of Actinophyga mauritiana by placing rubber bands in the midbody of A. mauritiana. Im- The two cut portions. Figure 3. mediately after this, the started to constrict slightly in the middle and showed some swelling in

Table 1. Asexual reproduction in H. atra

Expt. No. Initial total Initial mean Mean wt. (g) Mean wt. (g) Final total Final mean Growth / Survival no. used wt. (g) wt. (g) anterior part posterior part wt. (g) wt. (g) day (g) (%)

1 6 1387.0 216.7 86.7 120.2 2687.8 447.6 0.62 100.0

2 10 961.0 96.1 39.5 52.5 2701.8 280.4 0.64 95.5

Table 2. Asexual reproduction in B. marmorata

Expt. No. Initial total Initial mean Mean wt. (g) Mean wt. (g) Final total Final mean Growth / Survival no. used wt. (g) wt. (g) anterior part posterior part wt. (g) wt. (g) day (g) (%)

1 4 440.0 110.0 42.8 61.7 1215.8 304.0 0.52 100.0

2 20 2609.9 130.5 50.5 72.8 5291.0 286.0 0.54 92.5 SPC Beche-de-mer Information Bulletin #23 – February 2006 37 the posterior section. After one hour, the constric- faux. p. 71–76. In: research. Rid- tion became slightly more distinct, giving a heart der C., Dubois P., Jangoux M., and Lehaye shape to the posterior half. The anterior and poste- M.C. (eds). Balkema, Rotterdam. rior ends slowly rotated in opposite directions re- Conand C. and Uthicke S. 2001. Asexual reproduc- sulting in a more distinct constriction. The entire tion in Holothuria (Holothuroidea): A compari- process of fission lasted for an entire day. After two son between Pacific (GBR, Australia) and In- days, the body wall had its normal consistency and dian Ocean (La Reunion) populations of Sti- wounds at both ends were healed and nearly chopus chloronotus (poster). Ninth International closed. Howaida et al. (2004) also observed a sur- Coral Reef Symposium, Bali 10/00. Abstracts, vival rate of 65% for anterior parts and 85% for p. 300. posterior parts. Emson R.H. and Wilkie I.C. 1980. Fission and auto- tomy in . Oceanography Marine In the present work, all the cut pieces survived in Biology, A. Review, 18:155–250. the first experiment whereas in the second experi- Emson R.H. and Maldenov P.V. 1987. Studies of the ment, survival was 92.5–95%. The mortality that oc- fissiparous holothurian Holothuria parvula curred was for the anterior parts during the first two (Salenka) (Echinodermata: Holothuroidea). Jour- days after duplication. There was initial weight loss nal of Experimental Marine Ecology immediately after the induction of transverse fission 111:195–211. in the sea cucumbers, but thereafter, there was a Hawaida R.G., Ahmed I.A., Hanafy H.M., gradual increase in weight once the sea cucumbers Lawrence J.A., Ahmed I.M. and Salah G. EL- fully regenerated. The growth rate was slightly bet- Etreby. 2004. Sea cucumbers of the Red Sea: ter for H. atra (0.62–0.64 g day-1) compared with The Egyptian experience. p. 373–384. In: Lo- B. marmorata (0.52–0.54g day-1). So far, there are no vatelli A., Conand C. Purcell S. Uthicke, S. experimental studies on the growth rates of sea cu- Hamel J.-F. and Mercier A. (eds). Advances in cumbers after asexual reproduction. Therefore, the aquaculture and management. present study provides some useful information on FAO, Rome. this, although more studies are needed in this im- Reichenbach Y. and Hollway S. 1995. Potential of portant area of sea cucumber research. asexual propagation of several commercially important species of tropical sea cucumbers References (Echinodermata). Journal of World Aquaculture Society 26:272–278. Boyer C., Cailasson S, and Mairesse K. 1995. Asex- Reichenbach Y.N., Nishar, Y. and Saeed A. 1996. ual reproduction in Holothuria atra on a reef of Species and size related in asexual propaga- Reunion Island in the Indian Ocean. SPC tion of commercially important species of Beche-de-Mer Information Bulletin 7:7–9. tropical sea cucumbers. Journal of the World Chao S.M., Chen C.P. and Alexander P.S. 1993. Fis- Aquaculture Society 27:475–482. sion and its effect on population structure of Uthicke S. 1997. Seasonality of asexual repordcu- Holothuria atra (Echinodermota: Holothuroidea) tion in Holothuria atra, Holothuria edulis and Sti- in Taiwan. Marine Biology 116:109–115. chopus chloronotus. (Holothuroidea – Aspi- Conand C. 1989. Les Holothuries Asprochirotes du dochirotida) on the Great Barrier Reef. Marine lagon Nouvelle-Caledonie: biologie , écologie Biology 129:435–441. et exploitation. Etudes et Thèses, ORSTOM, Uthicke S. 1998. Regeneration of Holothuria atra, Paris. 393 p. Holothuria edulis and Stichopus choronotus. In- Conand C. 1993. Reproductive biology of the tact individuals and products of asexual re- holothurians from the major communities for production. p. 531–536. In: Moori R. and the New Caledonia lagoon. Marine Biology Telford M. (eds). Echinoderms. Proceedings of 116:439–450. the Ninth International Echinoderm Confer- Conand C. 1996. Asexual reproduction by fission in ence, Balkema, Rotterdam. Holothuria atra. Variability of some parameters Uthicke S. 2001a. The process of asexual reproduc- in populations from the tropical Indo-Pacific. tion by transverse fission in Stichopus chlorono- Oceanolology Acta 19:209–216. tus (greenfish). SPC Beche-de-Mer Information Conand C. 2004. Monitoring a fissiparous popula- Bulletin 14:23–25. tion of Holothuria atra on a fringing reef on Re- Uthicke S. 2001b. Influence of asexual reproduction union Island (Indian Ocean). SPC Beche-de- on the structure and dynamics of Holothuria Mer Information Bulletin 20:22–25. (Holodeima) atra and Stichopus chloronotus Conand C. and Ridder C. 1990. Reproduction asex- populations of the Great Barrier Reef. Marine uée par scission chez Holothuira atra (Holothu- and Freshwater Research 52:205–215. roidea) dans des populations de platiers réci-