Nudiscintilla cf. glabra Luetzen & Nielsen, 2005 (sensu Mifsud and Ovalis 2012)

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

Nudiscintilla cf. glabra Luetzen & Nielsen, 2005 (sensu Mifsud and Ovalis 2012) Figure 40

New records.

Israel • 1 v; Nahariyya, 200 m north of the entrance to the marina; 33.0149°N, 35.0890°E; depth 3-4 m; 6 Nov. 2018; pools with bioclastic sand in rocky bottom; snorkelled; J. Steger leg.; HELM project (sample D7); size: L 10.0 mm, H 6.4 mm (Figure 40A-E ) • 1 spcm; Palmachim; 31.9285°N, 34.6947°E; depth 3 m; 7 Nov. 2018; attached to the lower valve of a living Lessepsian Spondylus ; scuba diving; hand-picked; J. Steger & A. Ivkić leg.; HELM project (sample H17); size: L 4.2 mm, H 2.8 mm (Figure 40F, G ).

Remarks.

This non-indigenous species has first been recorded in the Mediterranean Sea by Mifsud and Ovalis (2012) as Nudiscintilla cf. glabra Lützen and Nielsen, 2005, based on five living specimens collected at Yumurtalik, Adana (Turkey) in shallow water. Their tentative identification was primarily guided by the external morphology of the living animals, which had a smooth mantle surface. This feature is characteristic for the monotypic genus Nudiscintilla (hence the genus name), but unusual among scintilloid galeommatids in general. Although no observations on living individuals could be made by us, the shell morphology of our material well matches that of the specimen illustrated in Mifsud and Ovalis (2012: fig. 1), suggesting conspecificity. Our findings represent the first records of this species from Israel. However, the dentition of the right valve as seen in SEM images (Figure 40C-E ) clearly differs from that described by Lützen and Nielsen (2005) for Nudiscintilla : the latter has a single cardinal tooth in each valve and no lateral teeth. However, the studied right valve - the hinge of the single live-collected specimen was not examined to avoid damage - bears what appears to be two cardinal teeth (Figure 40C ) that are fused at their base (Figure 40D, E ), as well as a ridge posterior to the internal ligament which most likely is a lateral tooth. This ridge seems to correspond to the left of the two swellings indicated by a pair of arrows on the right hand side of Mifsud and Ovalis (2012: fig. 1e), while the right swelling might correspond to a narrow ridge visible also on the dorsal margin of our valve. Mifsud and Ovalis (2012) interpreted these features as aberrant shell growth, however, the presence of such ridges also in our right valve (Figure 40D ) speaks against this hypothesis. Furthermore, their living individuals had a small tentacle situated above the widely gaping anterior inhalant region (cf. Mifsud and Ovalis (2012: 8, fig. 2a), however, the illustration of N. glabra in Lützen and Nielsen (2005: 292, fig. 38a) shows a small tentacle in the posterior exhalant region of the reflected mantle. In the light of the poorly developed taxonomy and great species diversity of galeommatid bivalves in the Indo-Pacific, further observations on living specimens, thorough comparisons with the type material from Thailand and molecular analyses are required to definitely clarify the relationship of Mediterranean specimens with N. glabra .

Figures

Figure 40. Nudiscintilla cf. glabra Luetzen & Nielsen, 2005 (sensu Mifsud and Ovalis 2012) A-E Nahariyya, Israel, HELM project (sample D 7): outer (A) and inner (B) views, detail of hinge (C) and hinge in dorsal view (D, E) of right valve F, G Palmachim, Israel, HELM project (sample H 17): right (F) and left (G) valve outer views. Scale bars: 3 mm (A, B); 0.5 mm (C, D); 0.2 mm (E); 1 mm (F, G).