Parvioris aff. dilecta (E.A. Smith, 1899)

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

Parvioris aff. dilecta (E.A. Smith, 1899) Figure 18E-M

New records.

Israel • 1 sh; north of Atlit; 32.7433°N, 34.9067°E; depth 40 m; 20 Sep. 2016; coarse biogenic sediment in a pool among rocks covered by coralligenous formations; grab; HELM project (sample NG40_2M); size: H 4.9 mm, W 2.2 mm (illustrated shell, Figure 18E-H ) • 3 spcms; west of Rosh HaNikra Islands; 33.0704°N, 35.0926°E; depth 12 m; 29 Oct. 2018; rocky substrate; suction sampler; HELM project (samples S52_1F, S52_1M, S52_2F).

Additional material examined.

Parvioris ibizenca (F. Nordsieck, 1968): Israel • 1 sh; west of Rosh HaNikra Islands; 33.0704°N, 35.0926°E; depth 12 m; 29 Oct. 2018; rocky substrate; suction sampler; HELM project (sample S52_2F).

Remarks.

The genus Parvioris Warén, 1981 was erected for a group of numerous conchologically very similar species of which many are still undescribed ( Warén 1981). The species here reported is very similar in general shape and size to P. dilecta ( Warén 1981: 146), especially the morphs illustrated here in Figure 18I-M . However, it has a multispiral protoconch of ~ 4.5 whorls (Figure 18H ), whereas P. dilecta has a paucispiral protoconch of ~ 1.5 whorls. The type of protoconch is considered to be related to the developmental mode, which was regarded a diagnostic character at the species level for most molluscan lineages ( Hoagland and Robertson 1988; Bouchet 1989). Because Warén (1984) suggested that the number of protoconch whorls is rather constant within species in Eulimidae , we currently do not consider our material conspecific with P. dilecta , but only closely related (thus the “aff.” notation). However, there is increasing evidence that poecilogony, the intraspecific variation in developmental mode, occurs in Caenogastropoda ( McDonald et al. 2014), Neogastropoda ( Russini et al. 2020), and Sacoglossa ( Krug 1998; Ellingson and Krug 2006; Vendetti et al. 2012).

Parvioris aff. dilecta can be easily distinguished from the native P. ibizenca because of a more arched apical part and because of the protoconch morphology: both have multispiral protoconchs, but P. ibizenca has shorter whorls and a distinct profile which inflates at the third whorl, in contrast with the more slender and regular profile of P. aff. dilecta . Our specimens are likely conspecific with those identified as Melanella sp. 1 by Blatterer (2019) from Dahab, Red Sea, suggesting that it is indeed a new Lessepsian species. An additional issue is whether the animal color is diagnostic at the species level like in other groups whose shells offer few diagnostic morphological characters, e.g., Mediterranean Granulina ( Neogastropoda : Granulinidae ) and Gibberula ( Neogastropoda : Cystiscidae ) ( Gofas 1990, 1992). Some of our live collected specimens show a light yellow-white color (e.g., Figure 18I-K ) whereas others have a brownish animal (e.g., Figure 18K-M ). The final attribution of our findings to a species requires a thorough revision of Parvioris , which is beyond the scope of this paper. The specimens reported as Parvioris sp. by Albano et al. (2020) from mesophotic reefs off northern Israel belong to this species.

Figures

Figure 18. Comparison between Parvioris aff. dilecta (E. A. Smith, 1899) and Parvioris ibizenca (F. Nordsieck, 1968) A-D Parvioris ibizenca, west of Rosh HaNikra Islands, Israel, HELM project (sample S 52 _ 2 F): front (A), side (B) and back (C) views, protoconch (D) E-H Parvioris aff. dilecta, north of Atlit, Israel, HELM project (sample NG 40 _ 2 M): front (E), side (F) and back (G) views, protoconch (H) I Parvioris aff. dilecta, west of Rosh HaNikra Islands, Israel, HELM project (sample S 52 _ 1 F): front view J-K Parvioris aff. dilecta, west of Rosh HaNikra Islands, Israel, HELM project (sample S 52 _ 1 M): front (J) and side (K) views L, M Parvioris aff. dilecta, same collecting data as for preceding, HELM project (sample S 52 _ 2 F): front (L) and side (M) views. Scale bars: 0.5 mm (A-C, I-M); 0.2 mm (D, H); 1 mm (E-G).