Sphenopus marsupialis (Gmelin, 1791)

Mondal, Tamal & Raghunathan, C., 2023, First report of free-living, solitary zoanthid from Andaman and Nicobar Islands, Zootaxa 5244 (3), pp. 293-298 : 294

Sphenopus marsupialis (Gmelin, 1791)

Specimens Examined: Four specimens; Location. Point Island (Lat.: 13°24.395ʹN; Long.: 92°49.159ʹE), North & Middle Andaman, Andaman and Nicobar Island ( Fig. 1 ); Depth range. 25 to 38 m.; Date of Collection. 20.VIII.2016; Coll. T . Mondal; Regn. No. ZSI/ ANRC /M/27759, ZSI/ANRC/M/27827, ZSI/ANRC/M/27902 & ZSI/ANRC/ M/27969.

Description: Solitary and free-living polyp. Shape of animal is laterally compressed ( Fig. 2A ). Body covered by coat of sand particles. Sizes of specimens: [Total length (mm): Maximum width (mm): Capitulum height (mm): Capitulum width (mm)] 28.25: 22.50: 8.71: 12.87 ( Fig. 2A ), 32.05: 21.25: 8.53: 16.37 ( Fig. 2B ), 36.57: 24.98: 10.50: 14.54 ( Fig. 2C ), 37.06: 22.56: 12.71: 14.64 ( Fig. 2D ). Size of outer tentacles and diameter of oral disc nearly equal in length when polyp fully extended; tentacles of inner region are nearly half in length in comparison with outer tentacles. A total of 54 tentacles are visible in two rows ( Fig. 2E–F ). Aboral end of polyp mostly rounded, column oval and covered by fine sand particles. Capitular ridge portion not distinctly crowded ( Fig. 2G–H ). Longitudinal section of polyp ( Fig. 2I ) shows mesoglea with well-developed sphincter muscle (reticulate marginal muscle sensu ( Swain 2009)), whereas cross-section of the polyp ( Fig. 2J ) shows dorsal directives, ectoderm, endoderm, complete and incomplete mesentery, siphonoglyph, mesoglea, sand pockets.

Colour: Center of oral disc deep brown ( Fig. 2E–F ). Extreme outer margin white and mid-portion of oral disc light brown. Outer side of polyp, i.e. the polyp column, light brown. Striped tentacles (with colour bands of light brown to dark brown to light brown to translucent) ( Fig. 2E–F ). Overall colour brown to dark or earthy grey.

Habitat: Found on sandy bottom with nearly half of body (aboral end) buried in sand.

Type Locality: Tranquebar (presently known as Tharangambadi, Tamil Nadu , India); described by Steenstrup (1856) from the collections of Johns. Originally, described in genus Sabella Linnaeus, 1767 .

Distribution: India: Madras ( Menon 1931; Gravely 1941), Ennore to Nagapattinam ( Nagabhushanam & Jothinayagam 1982), Andaman and Nicobar Islands (Present study) ( Fig. 1 ). Other countries: China (Pulo Faya), and North America (Massachusetts Bay) ( Gray 1867), Australia (Great Barrier Reef) ( Burnett et al. 1997), Brunei ( Reimer et al. 2012), Taiwan ( Soong et al. 1999), Indonesia ( Reimer et al. 2014), and Japan ( Reimer et al. 2016; Kise et al. 2020).

Figures

FIGURE 1. Collection locations of Sphenopus marsupialis (Gmelin, 1791) and distribution

FIGURE 2. Sphenopus marsupialis (Gmelin, 1791); A–D. Morphology of S. marsupialis, E. In-situ image, tentacles and polyp column, F. In-situ image, oral disc and tentacles, G & H. Aboral end of polyp, coating of fine sand particles, capitular ridge, I. Longitudinal section of polyp, mesoglea (M), sphincter muscles (SM), reticulate marginal muscle (RMM), J. Cross-section of polyp, dorsal directives (DD), ectoderm (EC), endoderm (EN), complete mesentery (CM), incomplete mesentery (IM), siphonoglyph (S), mesoglea (M), sand holes (SH). Scale bar = 5 mm.