Zygometra cf. comata AH Clark, 1911

Es, Mekhova & Ta, Britayev, 2015, Soft substratecrinoids (Crinoidea: Comatulida) andtheir macrosymbionts in Halong Bay (North Vietnam), Raffles Bulletin of Zoology 63, pp. 438-445 : 442-443

Zygometra cf. comata AH Clark, 1911

( Fig. 3a, b )

Zygometra comata Clark, AH, 1911: 537 ; Clark AH, 1921: 19–20, 70, 83, 88, figs. 27, 28; Clark AM & Rowe 1971: 17, Liao & Clark AM, 1995: 32, fig. 15; Kogo, 1998: 53, fig. 41; Mekhova & Britayev 2012: 466; Messing, 2015.

Material. South China Sea, Halong Bay , Katba Is., St. 2, 10–15 m depth, 30 April 2012 – 1 specimen .

Coloration. Dark brown, becoming red-brown in alcohol.

Measurements. Twenty-nine arms more than 50 mm in length (damaged); 39 cirri 23 mm in length.

Taxonomic remarks. It is also similar to Zygometra elegans ( Bell, 1882) in size, number of arms and segments in cirri. Z. comata and Z. elegans can be distinguished by the number of ossicles in Br III: Z. comata with only external Br III of 2 ossicles, while Z. elegans with both external and internal Br III of 4 ossicles ( Messing, 2015). Our specimen has external and internal Br III with 4 ossicles in several radii, and in several others external Br III absent, while internal has two ossicles. Taking into account the morphology of cirri and radii, this specimen was identified as Z. comata here.

Ecological notes. Very rare. Solitary, 10 m depth, on muddy sand. Diurnal; during the day fully exposed with arms arranged in a parabolic filtration fan. Found both on soft and hard substrates ( Mekhova & Britayev, 2012) while morphological or behavioral differences between specimens from different grounds unknown.

Symbionts. Polychaete Hololepidella cf. laingensis ; ophiuroid Ophiomaza cacaotica ; Amphipoda gen.sp.

Distribution. Vietnam, from Burma to Indonesia and North Australia ( Ho, 1994; Lane et al., 2000; Messing, 2015), Japan ( Kogo, 1998).

RAFFLES BULLETIN OF ZOOLOGY 2015

Figures

Fig. 3. Proximal ray articulations, branching patterns and arrangement of cirri. Scale bar = 1 cm. a, b, Oligometra serripinna; c, d, Zygometra cf. comata.