New records of the seacucumbers Holothuria (Semperothuria) imitans Ludwig and Stichopus herrmanni Semper (Echinodermata: Holothuroidea) from the southwestern coast of India
R.P.Deepa 1 & A. Biju Kumar 2
1 Department of Zoology, N.S.S. College, Pandalam, Kerala 689501, India
2 Department of Aquatic Biology and Fisheries, University of Kerala, Thiruvananthapuram, Kerala 695581, India
One of the five extant classes of echinoderms, the Holothuroidea represent a highly diverse group with about 1,400 species of seacucumbersrecorded from oceans around the world, from the intertidal and shallow seas to abyssal depths (Pawson 2007). Of the 763 species of echinoderms recorded from India, 160 species classified under 14 families and 62 genera are represented by holothurians (Venkataraman & Wafar 2005). In many parts of the world several species of holothuroidsare commercially fished and heavily overexploited for food, and many species are ideal sources of bioactive compounds. Detailed studies are warranted on holothurians primarily due to their prominent role in marine ecosystems. Despite their inclusion in Schedule I of the Wildlife (Protection) Act of India, information about their distribution in the southwestern coast of India is scanty (James 2007; Sastry 2007). During a biodiversity survey along the Kerala coast we found two species of holothurians, Holothuria(Semperothuria) imitansLudwig and Stichopus herrmanni Semper. A perusal of the literature found no previous record of these species from the southwestern coast of India.
1. Holothuria (Semperothuria) imitans Ludwig, 1875 (Images 1,2 & Figs. 1 A-I):
Materials examined: Eight specimens, 40-120mm in length from Vizhinjamcoast (8022’N & 76059’E), Lakshadweep Sea; collected by divers from the rocky hard bottom at 2-3m depth. The reference vouchers are deposited at the museum collections of Department of Aquatic Biology and Fisheries, University of Kerala, Reg.nos. AQB ECH HO 01-08.
Description: Colour in life yellow to yellowish-brown and in alcohol light brown. Body elongated and cylindrical with distinct anterior and posterior ends (Image 1). Podia scattered as small black warts on dorsal surface. Ventral surface well demarcated with thick arrangement of pedicels (Image 2) in three rows, clearly visible even in preserved specimen. Mouth ventral, surrounded by 20 grey-colouredtentacles. Anus large, without anal teeth. Body wall thick, leathery and body circular in cross-section. Two respiratory trees and a single tuft of gonadial tubules attached to the left side of dorsal mesentery.
Calcareous ring well developed; radial plates 1.5 times longer and 2 times wider than interradial ones; posterior side of radial plates convex; anterior side with well marked notch; interradialplates with posterior side undulating; anterior side with one anterior tooth (Fig. 1A). Stone canal absent.
Ossicles of dorsal and ventral body wall comprise of tables. Tables of ventral surface slightly shorter (33-40µm long) (Fig. 1D) than dorsal surface (30-44µm long) (Fig. 1B, 1C). Tables supported by four pillars. The disc of the table (24-29µm across) with four lateral holes surrounding a large central hole. Crown with eight short spines, the pairs of spines on each pillar lie closer. Tube feet with elongated rods of length 86-190µm (Fig. 1E), tables (25-38µm long) with the disk width 19-22µm (Fig. 1F, 1G) and large perforated plates of width up to 200µm (Fig. 1I). The rods perforated, resembles large buttons with holes arranged in pairs along central axis. The margin of rods rough, with small knobs. Tentacles with elongatedunbranched and slightly curved rods up to 36-110µm long (Fig. 1H) with spinous ends.
Remarks: First described by Ludwig (1875) from Samoa, H. imitans is also recorded from eastern Indian Ocean (Clark & Rowe 1971; James 1986). From the Indian coast it was collected from the Gulf of Mannar (Venkatraman et al. 2002). This is the first report of this species from the southwestern coast of India (western Indian Ocean) and shows the extended distribution of H. imitans.
2. Stichopus herrmanni Semper, 1868 (Images 3, 4;
Figs. 2 A-Q):
Materials examined: Two specimens of 160 and 185mm length from Vizhinjamcoast (8022’N & 76059’E), collected by divers from the sandy bottom at 4m depth. The voucher specimens are deposited at the Department of Aquatic Biology and fisheries, University of Kerala, Reg.nos. AQB ECH HO 09-10.
Description: Body colour in live yellowish-green, mottled with small dark black spots on the dorsal surface (Image 3); materials in ethanol light brown. Dorsal papillae grey with their tips brown coloured. Ventral side pale yellow with tube feet of same colour. Body firm and rigid. Irregular and conspicuous conical warts in bivium arranged in eight rows; smaller papillae disbursed in between the conical papillae. Trivium flat and with pedicels arranged in three bands along the radii (Image 4). Mouth ventral, surrounded by a circle of conical papillae and twenty peltateyellowish tentacles. Long tentacular ampullaeabout one-sixth of body length. A single contracted polian vesicle and one stone canal ending in madreporic plate. Anus terminal. Cuvierian tubules absent. Calcareous ring with deeply indented radial pieces and small interradials. Radials 1.5 times larger than interadials (Fig. 2A). A deep notch at the rear of the radial plates.
Dorsal body wall with small to large ‘C’ shaped rods with size ranging from 75- 175µm long (Fig. 2B). Rosettes of length ranging from 18-37µm (Fig. 2C) and tables with length up to 40µm (Fig. 2E). Tables supported by four pillars with rounded disc; four central and 12-14 marginal holes. The tower is of moderate length, with a broad crown bearing 8-12 spines. ‘C’ shaped rods occur in cluster. ‘S’ shaped rods (165µm long) (Fig. 2D) and ‘x’ shaped rods (88µm long) (Fig. 2F) random. Ventral body wall consists of tables (38- 44µm long) (Fig. 2G, 2H), rosettes (31-40µm long) (Fig. 2I) and ‘C’ shaped rods (156µm long) (Fig. 2J). Tube feet on ventral side with tables of length between 36-50µm (Fig. 2K, 2L), rods of length 73-98µm (Fig. 2N) and large perforated plates (Fig. 2M). Tables with rounded spiny or wavy disc having four to five central holes and 12-18 marginal holes. Perforation process present on one side or either side of the rod. Dorsal papillae consists of tables (40µm long) (Fig. 2P), rosettes (34µm long) (Fig. 2O) and ‘C’ shaped rods. Tentacle include small to large curved rods (length 137µm) (Fig. 2Q) with spiny undulations on one side.
Remarks: The present specimens bear close resemblance in morphology and nature of spicules with Stichopus herrmanni redescribedin detail by Massin (1999) and Massinet al. (2002). Massin et al. (2002) considered the type locality of the species as Malaysia. This species earlier described in literature as Stichopus variegatus Semper, 1868, has been assigned new status by Rowe (in Rowe & Gates 1995) and is now named Stichopus herrmanni Semper, 1868. Stichopus variegatus Semper, 1868 is considered to be the junior subjective synonym of S. monotuberculatus(Quoy & Gaimard, 1833).
S. herrmanni is recorded from Minicoy Island as S.variegatus by Nagabhusanam& Rao (1972), from Lakshadweep by Mukhopadhyay & Samantha (1983), James (1989), and Mukhopadhyay (1991); and from Gulf of Mannarand Palk Bay along the southeastern coast of India and Maldives by James (2001, 2003). This is the first record of this species from the southwestern coast of India.
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