Cerithidea houbricki, Reid, 2014

Reid, David G., 2014, The genus Cerithidea Swainson, 1840 (Gastropoda: Potamididae) in the Indo-West Pacific region, Zootaxa 3775 (1), pp. 1-65 : 17-18

Cerithidea houbricki new species

( Figures 3 N–R, 4)

Cerithidea rhizophorarum — Cernohorsky, 1972: 61, pl. 13, fig. 3 (as rhizoporarum; not A. Adams, 1855). Poraituk & Ulijaszek, 1981: 13, pl. 2b (as rhizoporarum; not A. Adams, 1855).

Cerithidea n. sp. A Reid et al., 2013: fig. 2 (map).

Types. Holotype AM C.126895 ( Fig. 3 O–Q) and five paratypes AM C.478233 ( Fig. 3 N), Koravake , Gulf Prov., Papua New Guinea.

Etymology: Richard S. Houbrick was the pioneer of the modern anatomical and phylogenetic study of the Cerithioidea, including the genus Cerithidea (e.g. Houbrick 1984, 1986, 1988). He was a mentor for me and other young malacologists until his untimely death in 1993 ( Harasewych & Kabat 1995). He described C. reidi in 1986 and, after 28 years, I am delighted to return his compliment.

Taxonomic history. A shell of this species ( Fig. 3 R) was illustrated by Cernohorsky (1972) as C. rhizophorarum ; this misidentification was repeated by Poraituk & Ulijaszek (1981), whose material was identified by P. Colman of the AM, where it is now deposited and is the type collection of the new species. The existence of this new species was noted by Reid et al. (2013).

Diagnosis. Shell: large, solid, elongated-pupoidal with expanded and thickened aperture, periphery rounded; 19–29 rounded axial ribs (remaining strong and becoming rugose on final whorl); ventrolateral varix weak, at 220– 260°; 4 spiral ridges above periphery on final 1–2 whorls; banded pattern. New Guinea.

Material examined. 2 lots.

Shell ( Fig. 3 N–R): H = 29.9–41.0 mm. Shape elongated-pupoidal (H/B = 2.16–2.40, SH = 2.85–3.04); decollate, 6–7 whorls remaining; spire whorls lightly rounded; spire profile convex; periphery rounded to slightly angled; solid. Adult lip thickened, moderately flared; apertural margin planar in side view; weak anterior projection adjacent to canal. Sculpture on spire of straight to slightly opisthocline or curved (opisthocyrt) axial ribs, occasionally bifurcating posteriorly (adapically), remaining strong and becoming rugose on final whorl, usually continuing as rugose ribs on base, ribs rounded, interspaces 1–1.5 width of ribs, 19–29 ribs on penultimate whorl; spiral sculpture of 4 strong cords above periphery on final 1–2 whorls, producing nodules at intersection with axial ribs; base with 4–7 cords. Ventrolateral varix weakly developed at 220–260°. Surface with faint, fine spiral microstriae on periostracum, satin sheen. Colour: fawn, broad brown band above aperture, spiral ridges brownish, brown band adjacent to columella; occasionally entirely dark brown; aperture brown.

Animal: Unknown.

Range ( Fig. 4 ): New Guinea. Records: Papua New Guinea: Koravake, Gulf Prov. (AM C.126895). Indonesia: Samberbaba, Yapen I., East Papua (USNM 835667).

The specimen from Yapen is doubtfully assigned to this species (see below).

Habitat and ecology. Poraituk & Ulijaszek (1981) reported it to be common in the upper reaches of the Pie River estuary, 20–30 km from the open sea, at the extreme landward fringe of the mangrove forest. It occurred in clusters on the bases of tree trunks and on mud and rotten wood. Other molluscs present were Polymesoda and Neritina , so salinity was evidently low.

Remarks. Only two samples of this species were available, the six type specimens and a single specimen from Yapen, all dry shells. The relatively solid shell, slightly pupoidal outline (in the type collection), weak ventrolateral varix and axial ribs continuing strongly beyond the varix, all indicate that its closest relationship is likely to be with C. weyersi . The new species is distinguished from this likely sister by larger size (to 41 mm, cf. 33 mm) and by the 4 spiral ridges above the periphery on the body whorl, producing a nodulose or rugose sculpture. The island of Yapen is geographically closer to the nearest record of C. weyersi from Halmahera, than it is to the other locality of C. houbricki in the Gulf of Papua ( Fig. 4 ), but the shell from Yapen is not similar to the typical C. weyersi from Halmahera.

Compared with the type collection, the specimen from Yapen is narrower, more cylindrical in shape, smaller (H = 34.7 mm) and the axial ribs do not continue on to the base ( Fig. 3 R; the same specimen was figured by Cernohorsky, 1972), although these differences are no greater than those seen among specimens of C. weyersi (compare Fig. 3A–M ). A recent expedition to Madang, northern New Guinea, failed to find any Cerithidea species in mangrove habitats (P. Bouchet, pers. comm.) and there is little development of mangrove forests along the entire north coast of New Guinea. Mangroves line most of the south coast of New Guinea and collections of Cerithidea species are available from several localities (see C. anticipata and C. balteata ), but the present species has not been recorded there. Phylogeographic studies of marine invertebrates have suggested that Cenderawasih Bay (including the island of Yapen) is isolated by marine currents ( Barber et al. 2006; Carpenter et al. 2011). For these reasons it is unlikely that the collections from Yapen and Koravake are conspecific, but more material is needed to investigate this further. Like its probable sister, C. weyersi , this species may have remained poorly known and rarely collected because of its transitional habitat between marine mangrove forests and freshwater streams. Further study of additional material, and application of molecular techniques, is very desirable.

Poraituk & Ulijaszek (1981) reported that this species was a significant component of the diet of indigenous people of the Purari Delta, Papua New Guinea.

Figures

FIGURE 4. Distribution of Cerithidea weyersi (circles) and C. houbricki new species (triangles). All records based on specimens examined.

FIGURE 3. A – M, Cerithidea weyersi. N – R, C. houbricki. A, C. weyersi Dautzenberg, 1899, syntype, Indrapura, Sumatra, Indonesia (IRSNB MT 2772). B – D, Kantang, Trang Prov., Thailand (NHMUK 20130230). E – G, Sumatra, Indonesia (NHMUK 1899.11.20.4; views of same specimen). H – J, between Pangandaran and Cipatujah, Java, Indonesia (ZMB 106428; H juvenile). K, between Pangandaran and Cipatujah, Java, Indonesia (ZMB 106426). L, M, Char Kukrimukri, Bhola, Bangladesh (NHMUK 20130231). N – Q, C. houbricki n. sp., paratype (N) AM C. 478233 and holotype (O – Q) AM C. 126895, Koravake, Gulf Prov., Papua New Guinea. R, Samberbaba, Yapen I., Papua New Guinea (USNM 835667). Photography credit: A, IRSNB.