Salenthydrobia, Wilke, 2003

Wilke, Thomas, 2003, Salenthydrobia gen. nov. (Rissooidea: Hydrobiidae): a potential relict of the Messinian salinity crisis, Zoological Journal of the Linnean Society 137 (2), pp. 319-336 : 331-333

SALENTHYDROBIA GEN. NOV.

Type species. Salenthydrobia ferrerii sp. nov.

Etymology. Named after the Salentina Peninsula in Italy, the region where the genus was first found.

Distribution Salentina Peninsula, Lecce Province, Italy

Description (based on fresh specimens of Salenthydrobia ferrerii n.sp.). Shell and operculum: shells of adult individuals are about 2.8–3.6 mm high and 1.4– 1.7 mm wide with 5.0–6.0 whorls. The shell shape is ovate-conic ( Fig. 6 ). The whorls are relatively flat and smooth with distinct growth lines. The aperture is ovate to ovate-pyriform. The outer lip is straight and thin. The inner lip is only slightly arched. Shells of living individuals are opaque cream-coloured to light brown. The protoconch is often eroded. The sculpture of the protoconch, only seen in juveniles, is granular. The operculum is corneous and paucispiral. The outer parts of the operculum are opaque white; the central part has a characteristic orange-brown colour.

External features: head- foot morphology similar to that described for Ventrosia truncata by Hershler & Davis (1980). The snout is only lightly pigmented centrally and has a clear tip. Concentrations of bright granules posterior to the eyes and, less densely, laterally on snout and neck. The tentacles are free of granules but have a dark pigmented central bar extending from the base of the tentacle almost to the tip ( Fig. 2E ). The distinctly orangebrown coloured buccal mass is visible through the snout. The eyes are in weak bulges at the outer base of the tentacles.

Mantle cavity: general anatomy, including ctenidium and osphradium, is similar to that of V. truncata (see Davis, Forbes & Lopez, 1988). Size varies between 1.88 mm to 2.44 mm and the number of gill filaments between 21 and 30.

Alimentary canal: the radula is typically taenioglossate and very similar to those found in other hydrobiine taxa (e.g. Giusti & Pezzoli, 1984). The general formula for the central tooth is:

(2-4)-1-(2-4)

(1-2)-(1-2).

The moderately large stomach is unpigmented and very similar to that shown in Davis et al. (1988) for Ventrosia truncata , except that Salenthydrobia does not have a caecal appendix.

Female reproductive system: the anterior lobes of the gonad cover the posterior part of the stomach and the gonad extends almost to the posterior tip of the digestive gland. The pallial oviduct is divided into a glandular posterior albumen gland and into a slightly longer anterior capsule gland. The large bursa copulatrix is located dextro-lateral to the style sac and is not or only partially covered by the posterior end of the albumen gland. It is hammer-shaped with the relatively long duct of the bursa extending from the dorsal or anterodorsal end. The single seminal receptacle is elongate, usually with a slight constriction in the middle. The duct of the seminal receptacle is relatively long. It joins the oviduct just before the latter joins the duct of the bursa. A section of the oviduct is black pigmented and coiled with a total number of 2.0–2.5 loops ( Fig. 8 ).

Male reproductive system: the yellow gonad extends from the posterior part of the stomach almost to the tip of the digestive gland. The vas efferens leaves the gonad about 10–20% posterior to its anterior end, loops before reaching the anterior end of the gonad and runs back about 60–80% of the length of the gonad. It then returns as the coiled seminal vesicle. From the seminal vesicle the white vas deferens (beginning before the anterior end of the digestive gland) runs ventrally to the stomach, becomes transparent and enters the large prostate just anterioventral of its posterior tip and leaves the prostate posterio-ventral of the anterior tip. The penis is large and tapering with a wide basis. There are no appendices at the inner or outer edges. The penial duct is weakly undulated in the basal and medium parts and almost straight in the distal part. It emerges as a distinct papilla at the distal end of the penis. Glandular fields are mostly present in the medial part of the penis, close to the outer edge, but also near the inner edge as well as the tip and the base of the penis ( Figs 2E , 7 ).

Nervous system: very similar to that described for V. truncata (see Hershler & Davis, 1980: fig. 5) and other hydrobiids. Detailed measurements are given in Table 5.

Figures

Figure 2. Head-penis complex in the four known genera of the Hydrobiinae (sensu Radoman, 1977): Hydrobia (A), Peringia (B), Ventrosia (C), Adriohydrobia (D), as well as in taxon A (E). Note that the general penis morphology is constant within the putative genera of the Hydrobiinae. All drawings are to scale.

Figure 6. Salenthydrobia ferrerii sp. nov., individuals preserved in ethanol. A, holotype (ANSP, A19754). B-D, paratypes (ANSP, A19755). E, F, paratypes (SMF 323031/2).

Figure 7. Salenthydrobia ferrerii sp. nov., penis morphology.

Figure 8. Salenthydrobia ferrerii sp. nov., bursa copulatrix complex.