Hololepidella ophiuricola Gibbs 1971

Hololepidella ophiuricola Gibbs, 1969

Hololepidella commensalis.—Gibbs, 1969:451, fig. 132 [not Willey, 1905].

Hololepidella ophiuricola Gibbs, 1971:121, fig. 3A–H.—Hartmann-Schröder, 1984:66 [key].

MATERIAL EXAMINED.—CENTRAL PACIFIC OCEAN: Solomon Islands: Graham Point, Marau Sound, on oral surface of ophiuroid Macrophiothrix koehleri A.M. Clark, Oct 1965, P.E. Gibbs, collector, holotype (BMNH 1970.20) and 3 paratypes (BMNH 1970.21–23). Kalota Island, Auki, Malaita, on oral surface of opiuroid Ophiarthrum pictum Müller and Troschel, 21 Nov 1965, P.E. Gibbs, collector, paratype (BMNH 1970.24).

DESCRIPTION.—Holotype 15 mm long, 3 mm wide including setae, with 53 segments and 25 pairs of elytra; 4 paratypes with 41–50 segments and 19–23 pairs of elytra, with arrangement as in H. nigropunctata. Pigmentation appearing on dorsal cirrophores and styles of dorsal cirri, on dorsum as broken or nearly continuous transverse bands, and as dark spots on ventral bases of parapodia and elytrophores (Figure 4A–C,E,F; Gibbs, 1969, fig. 132). Elytra oval, delicate, transparent, without microtubercles or papillae, with some scattered pigment spots (Gibbs, 1971, fig. 3B,C).

Bilobed prostomium with triangular lobes, pigmented medial part, and 2 pairs of small eyes; median antenna with dark ceratophore in anterior notch and long dark style; lateral antennae with small ceratophores inserted ventrally and short styles; palps long, tapered, pigmented on lateral sides; tentaculophores lateral to prostomium, without setae, each with pair of dorsal and ventral tentacular cirri similar to median antenna, minutely papillate (Figure 4A,B; Gibbs, 1971, fig. 3A). Second or buccal segment without nuchal lobe, with first pair of elytrophores, biramous parapodia, and long ventral buccal cirri similar to tentacular cirri; notosetae similar to those of following segments; neurosetae similar to upper ones of following segments (Figure 4A–D).

Notopodium of parapodium with projecting acicular lobe on lower side; larger neuropodium with tapered subtriangular presetal acicular lobe and shorter rounded postsetal lobe (Figure 4C,E,F; Gibbs, 1971, fig. 3D). Notosetae about same width as neurosetae, minutely serrated along one border (Figure 4G; Gibbs, 1971, fig. 3E). Few supraacicular neurosetae with prominent spinose rows on basal part and minute spinose row on distal part extending to near bare tips (Figure 4H; Gibbs, 1971, fig. 3F); more numerous subacicular neurosetae with faint spinose rows and slightly hooked, bare tips (Figure 4H,I; Gibbs, 1971, fig. 3G,H); all neurosetae with entire tips. Dorsal cirri with long cylindrical cirrophores on posterior sides of notopodia, styles extending close to tips of neurosetae; dorsal tubercles inconspicuous; ventral cirri extending near to tip of neuropodial lobe (Figure 4F).

BIOLOGY.—Hololepidella ophiuricola is commensal with ophiuroids. Individual specimens have been found on the oral surfaces of the discs of two species of ophiuroids: Macrophiothrix koehleri A.M. Clark and Ophiarthrum pictum Müller and Troschel, living under coral boulders and in crevices on the reef platform of the Solomon Islands. The pigment pattern of the polynoids differed somewhat: on M. koehleri the black bands were essentially longitudinal and on O. pictum, transverse, presumably imparting a cryptic coloration (Gibbs, 1969, fig. 132).

DISTRIBUTION.—Central Pacific Ocean, Solomon Islands. Low water.