Parthenina cossmanni (Hornung & Mermod, 1924)

Albano, Paolo G., Steger, Jan, Bakker, Piet A. J., Bogi, Cesare, Bosnjak, Marija, Guy-Haim, Tamar, Huseyinoglu, Mehmet Fatih, LaFollette, Patrick I., Lubinevsky, Hadas, Mulas, Martina, Stockinger, Martina, Azzarone, Michele & Sabelli, Bruno, 2021, Numerous new records of tropical non-indigenous species in the Eastern Mediterranean highlight the challenges of their recognition and identification, ZooKeys 1010, pp. 1-95 : 1

Parthenina cossmanni (Hornung & Mermod, 1924) Figure 26A-H

New records.

Israel • 1 sh; north of Atlit; 32.7422°N, 34.9181°E; depth 30 m; 20 Sep. 2016; sand; grab; HELM project (sample NG30_2F); size: H 1.9 mm, W 0.9 mm (illustrated shell, Figure 26A-F ) • 9 spcms, 2 shs; Ashqelon; 31.7002°N, 34.5498°E; depth 21 m; 18 Sep. 2016; sand; grab; HELM project (samples SG20_1F, SG20_2F, SG20_4F, SG20_5F); size: H 2.0 mm, W 0.8 mm (illustrated specimen, Figure 26G, H ) • 1 spcm; Ashqelon; 31.6868°N, 34.5516°E; depth 12 m; 30 Apr. 2018; offshore rocky reef; suction sampler; HELM project (sample S12_1F).

Additional material examined.

Parthenina indistincta (Montagu, 1808): Israel • 2 shs; Ashqelon; 31.7002°N, 34.5498°E; depth 21 m; 18 Sep. 2016; sand; grab; HELM project (sample SG20_2F) • 1 sh; Ashqelon; 31.7101°N, 34.5406°E; depth 31 m; silty sand, 15 cm below sediment surface; gravity corer; HELM project (sample SC30_1_15L); size: H 1.7 mm, W 0.7 mm (illustrated shell).

Remarks.

Parthenina cossmanni has an elongated-conical shell with flat-convex whorls and a protoconch of type C. The whorls of the spire have a subangular profile, whereas the body whorl in adult specimens is more convex and evenly rounded. The axial sculpture is made of strong orthocline ribs that become slightly flexuous on the body whorl in some specimens (Figure 26A-E ). The spiral sculpture on the spire consists of a single, thin, suprasutural cord; a second cord emerges on the penultimate whorl, and three cords are present on the last whorl. The columellar tooth is weak and deeply inset, and in some of the studied specimens hardly visible inside the aperture. The soft body of ethanol-preserved specimens is yellowish, with the eyes visible through the shell (Figure 26G, H ).

The type material of P. cossmanni was collected from the Red Sea of Massawa (Eritrea) at a depth of 30 m ( Hornung and Mermod 1924); the species was recently recorded from Dahab (Gulf of Aqaba, northern Egypt) by Blatterer (2019), and from Jordan by Peñas et al. (2020). Outside the Red Sea, it is known from Vietnam ( Saurin 1959) and Thailand ( Robba et al. 2004).

Among native Mediterranean species, P. cossmanni superficially resembles Parthenina interstincta (J. Adams, 1797). The latter species, however, has only two spiral cords on the last whorl and a more developed columellar tooth. P. cossmanni is further similar to P. indistincta ( Montagu 1808) (Figure 26I-L ) which has a very weak, internal columellar fold ( Warén 1991a: 96, fig. 29f) and three (rarely four) spiral cords on the last whorl. Compared to P. cossmanni , however, the shell of P. indistincta is more elongated and has two spiral cords on the spire whorls.

We suspect the two shells illustrated as P. indistincta in Öztürk et al. (2011: fig. 10A, B) might also be P. cossmanni , considering their broad shape and overall morphology. Öztürk et al.'s material was collected in 2009 from a mud bottom at 9 m depth in Mersin Bay (stn. 46, 36.7167°N, 34.8667°E), south-eastern Turkey; should our hypothesis be confirmed upon re-examination of these shells, this would suggest that P. cossmanni likely has a wider distribution in the southeastern Mediterranean Sea. Our finding of several living specimens on the Israeli shelf, together with the relative rarity of empty shells in the samples, suggests that this species might have established locally only rather recently.

Figures

Figure 26. Comparison between Parthenina cossmanni (Hornung & Mermod, 1924) and Parthenina indistincta (Montagu, 1808) A-F Parthenina cossmanni, north of Atlit, Israel, HELM project (sample NG 30 _ 2 F): front (A, C) and back (B, D) views, detail of the spiral sculpture on the body whorl (E) and apical view of the protoconch (F) G, H Parthenina cossmanni, Ashqelon, Israel, HELM project (sample SG 20 _ 4 F): front (G) and back (H) views I-L Parthenina indistincta, Ashqelon, Israel, HELM project (sample SC 30 _ 1 _ 15 L): front (I, K) and back (J, L) views. Scale bars: 0.5 mm (A-E, G-L); 0.1 mm (F).