Fossarus sp. (aff. aptus sensu Blatterer 2019)

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

Fossarus sp. (aff. aptus sensu Blatterer 2019) Figure 4

New records.

Israel • 1 sh; Ashqelon; 31.6868°N, 34.5516°E; depth 11 m; 31 Oct. 2018; offshore rocky reef; suction sampler; HELM project (sample S58_3M); size: H 3.3 mm, W 2.7 mm.

Remarks.

We found a single empty shell of this Fossarus that can be readily distinguished from the Mediterranean F. ambiguus (Linnaeus, 1758), which bears prominent spiral ridges and has a depressed spire. In contrast, our shell bears numerous spiral cords and has a high spire. This shell is extremely similar to " Fossarus aff. aptus Melvill, 1912" illustrated by Blatterer (2019: plate 87, fig. 7a-f). Especially the largest specimen (plate 87, fig. 7a, b) bears a sculpture of similarly depressed and closely arranged spiral cords, has a very similar profile and a large elongated umbilical area. Blatterer’s specimen shows, however, more regularly alternated thicker and finer cords, whereas in our specimen this feature is not so evident. Our specimen is almost the double in size and rather worn, which may explain the observed differences in sculpture. The extreme similarity with Blatterer’s Red Sea specimens suggests that this is a new non-indigenous species in the Mediterranean Sea.

The name Fossarus aptus is problematic. Originally introduced by Melvill (1912) for a species from the Persian (Arabian) Gulf, it is currently considered a synonym of the Atlanto-Mediterranean F. ambiguus ( MolluscaBase 2020), but no revision of this genus is available. However, this name fits neither Blatterer’s specimens nor ours because F. aptus is characterized by five strong spiral keels (indeed similar to F. ambiguus ).

Figures

Figure 4. Fossarus sp. (Fossarus aff. aptus sensu Blatterer, 2019), Ashqelon, Israel, HELM project (sample S 58 _ 3 M): front (A), side (B) and back (C) views. Scale bar: 1 mm.