Cantellius sumbawae (Hoek, 1913)

CANTELLIUS CF. SUMBAWAE ( HOEK, 1913)

E x a m i n e d m a t e r i a l: H o s t D i s t i c h o p o r a s p., TAU AR29843 View Materials , Bali, Indonesia ( Figs 3A, 4–7), 5 November 2017 .

Description: Barnacles are scattered along the branches of the hydrozoan colony ( Fig.3A),mostly on the lateral side of the branches ( Fig. 3A, inset). Shell conical, four plated (rostrum, carina and paired latera; Fig. 4A, C), externally covered by the hydroid skeleton and tissue ( Fig. 4A, B). Carinorostral diameter, 4.35 ± 1.36 mm (N = 11), sheath forming inner lamina. Basis, shallow cup shape with radiating ridges and furrows ( Fig. 4D, E) reaching the centre of the basis. Orifice central, small. Scutum and tergum ( Fig. 5A) separated, white. Scutum triangular; basal margin sinusoidal; length approximately equal to tergal margin. Both the occludent margin and the tergal margin straight. Externally, growth ridges parallel to basal margin outline, forming teeth on occludent margin. Shallow cavity for lateral depressor. Inner side with prominent adductor ridge; articular ridge on tergal margin occupying nearly the entire length of the margin. Tergum elongated; carinal margin about two-thirds of scutal margin, with blunt rounded spur; scutal margins slightly curved, apical angle ~60°; small beak at the apex; basal margins sinusoidal; external surface with growth ridges parallel to basal margins; shallow median furrow from apex to spur base. Inner side with articular ridge along the scutal margin. Small pits scattered on the inner side. Maxilla rounded ( Fig. 6A), with simple setae along interior margin and distal part. Maxillule ( Fig. 6C) cutting edge straight, without notch, with row of seven large setae. Surface of maxillule close to cutting edge, with short, simple type of setae. Simple setae on upper and lower margins. Mandibule ( Fig. 6E) with five teeth; gap between first tooth and second tooth; second tooth located in middle of cutting edge; gap between second and third tooth. Second to fourth teeth bidentate. Surface of mandible close to cutting edge from upper to third tooth, with short simple setae. Mandibular palp elongated ( Fig. 6D); setae on inferior margin; lower and upper margins with simple setae. Labrum bilobed ( Fig. 4B) with V-shaped notch between lobes; two or three sharp teeth on each lobe ( Fig. 6B). Cirrus I ( Fig. 7A) rami unequal; anterior ramus ten articles longer; posterior ramus five articles; distal article with mixed setae. Cirrus II with equal rami; anterior with seven articles and posterior with five articles. Terminal setae ( Fig. 7G) simple. Cirrus III ( Fig. 7C) anterior ramus with eight to nine articles, with short sharp teeth on front of articles ( Fig. 7F); posterior ramus with six to seven articles. Cirri IV–VI long ( Fig. 7D, E), slender, with both rami of similar length. Penis long, annulated with scattered short simple setae; pedicel ( Fig. 7E) with short basidorsal point.

Remarks: Based on the morphology of the opercular valves, the barnacles found on Distichopora fit into the description of C. sumbawae ( Fig. 5B). Cantellius sumbawae was based on a single specimen attached to the small, solitary, free-living coral, Heteropsammia . The coral and its barnacle were dredged during the Siboga expedition in February 1900 at ~ 36 m depth on a sandy or muddy bottom in Saleh Bay anchorage, east of Dangar Besar on the Indonesian island of Sumbawa. The comprehensive list of barnacles and their host corals ( Ogawa & Matsuzaki, 1992) indicates that since C. sumbawae was described, it has not been recorded from any other coral. The Hoek specimen could not be traced in the collection of the Naturalis Biodiversity Centre, Leiden, The Netherlands, where the Siboga expedition material is stored. There are differences between Hoek’s specimen and those found on Distichopora . The stylasterid skeleton completely encrusts the barnacle shell, whereas this was not reported by Hoek (1913). Brickner et al. (2010) suggested that the overgrowth of the coral skeleton and coverage of the barnacle shell is a result of the coral growth and should be regarded as a coral character rather than a barnacle character. However, without examination and comparison of barnacles on Heteropsammia , it is uncertain whether the barnacles from both hosts belong to the same species. Owing to this uncertainty, we prefer to identify our specimens as Cantellius cf. sumbawae .