Hydroides longispinosa Imajima, 1976b

Figs 4H, 6

Hydroides longispinosa Imajima, 1976b: 240–246, fig. 5a–q (type locality; Koniya, Amami-Oshima, southern Japan; on the pearl oyster Pteria penguin (Röding, 1798)) .

Hydroides centrospina Wu & Chen, 1981: 354–355 (type locality: South China Sea).

Hydroides longispinosa – Imajima 1977: 95 (Ogasawara Islands, southern Japan; intertidal to sublittoral; on buoy and underside of reef corals). — Imajima 1982: 46 (Palau Islands; intertidal to sublittoral; attached to boat). — Imajima & ten Hove 1984: 48 (Pohnpei Island (formerly known as Ponape), Federated States of Micronesia, and Lizard Island, Australia; outer reef on experimental fouling plates). — Imajima & ten Hove 1986: 3 (Solomon Islands and Gilbert Islands; attached to rope). — Kupriyanova et al. 2015: 286–288, fig. 6 (Lizard Island, Great Barrier Reef, Australia; 2–20 m; on coral rubble and fouling plates). — Sun et al. 2015: 46–50, fig. 14 (New South Wales and Queensland, Australia; 2–20 m; on shells and dead coral substrate).

Hydroides centrospina – Fiege & Sun 1999: 116 (synonymy).

Hydroides longispinosus – Fiege & Sun 1999: 116 –118, figs 6A–D, 7A–B (Hainan Island, South China Sea; 2–14 m; on bivalve shells, seagrass, algae and the barnacle Solidobalanus socialis (Hoek, 1883)) . — Bailey-Brock et al. 2012: 969, 972, fig. 3D (Enewetak, Rongelap, Marshall Islands; 12–18 m; on coral).

Material examined

Two specimens: HI (2) Aug. 2006.

Diagnosis

Tube white, with or without two longitudinal ridges, with or without peristomes; but no alveoli. Opercular peduncle smooth, white. Opercular funnel with 18 radii with blunt tips (Fig. 4H); verticil with 12 spines, straight, with pointed tips (Fig. 4H); all spines with 2–3 internal spinules and 5–6 pairs of lateral spinules, without external spinules or wings (Fig. 4H); with a long, smooth central spine (Fig. 4H). Special collar chaetae with two pointed, elongate teeth and a proximal rasp, distal blade with notch and many denticles.

Taxonomic remarks

The specimens recorded here are slightly different from the original description of Hydroides longispinosa (Imajima 1976b): the number of radii (18) is slightly less, as in the original description there are 20 radii; the verticil spines have fewer internal spinules (2–3), versus 15–18, and few lateral spinules (5–6 pairs), versus 7–9 pairs.

Hydroides longispinosa is widely distributed in the western and central Pacific; however, this report represents the first record in the Hawaiian Islands, where it was found on fouling plates. Given the distance between the Polynesian Islands, it is likely that the species was dispersed as fouling on yachts or ships, rather than by natural dispersion. Several records in the western Pacific were from artificial substrates (Imajima 1982; Imajima & ten Hove 1984, 1986).

Ecology

Intertidal to 20 m. On seagrass, algae, the barnacle Solidobalanus socialis, the pearl oyster Pteria (Magnavicula) penguin and other bivalve shells, underside of reef corals (Imajima 1976b, 1977; Fiege & Sun 1999), and also on artificial substrates such as boats, buoys, ropes and fouling plates (Imajima 1977, 1982; Imajima & ten Hove 1984, 1986).

Distribution

Western and central Pacific: Southern Japan, South China Sea, Australia, Palau, Pohnpei, Solomon and Marshall Islands (Imajima 1976b, 1977; Wu & Chen 1981; Imajima 1982; Imajima & ten Hove 1984, 1986; Fiege & Sun 1999; Bailey-Brock et al. 2012; Sun et al. 2015). In this work, only two specimens of Hydroides longispinosa were found, on a fouling plate from Oahu, Hawaii (Fig. 6). This represents a possible range extension northward from Enewetak, Marshall Islands (Bailey-Brock et al. 2012) to Oahu, Hawaii (4300 km).