Musculus coenobitus (Vaillant, 1865)

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

Musculus coenobitus (Vaillant, 1865) Figures 34A-D , 35A-F

New records.

Israel • 2 spcms; west of Rosh HaNikra Islands; 33.0704°N, 35.0926°E; depth 12 m; 1 May 2018; rocky substrate; suction sampler; HELM project (sample S14_4M) • 4 spcms; same collecting data as for preceding; 29 Oct. 2018; HELM project (samples S52_1M, S52_2L, S52_3M, S52_3L) • 1 sh; north of Nahariyya port; 33.0127°N, 35.0896°E; beached; 29 Oct. 2018; HELM project (sample H3); size: L 10.2 mm, H 6.0 mm (illustrated shell, Figure 34A-D ).

Additional material examined.

Musculus subpictus (Cantraine, 1835): Croatia • 14 spcms; Istria, off Rovinj, western shore of Sveta Katarina; 45.0760°N, 13.6276°E; 3 Jul. 2008; dried-out fouling community collected from the surface of buoy-like floating objects dumped on the shore (J. Steger coll.).

Israel • 10 spcms, 3 vv; Ashqelon; 31.6868°N, 34.5516°E; depth 12 m; 30 Apr. 2018; offshore rocky reef; suction sampler; HELM project (samples S12_1F, S12_1M, S12_1L, S12_2F, S12_2M) • 111 spcms, 2 vv; Ashqelon; 31.6891°N, 34.5257°E; depth 25 m; 2 May 2018; offshore rocky reef; suction sampler; HELM project (samples S16_1F, S16_1M, S16_1L, S16_2F, S16_2M, S16_2L) • 13 spcms; west of Rosh HaNikra Islands; 33.0704°N, 35.0926°E; depth 12 m; 1 May 2018; rocky substrate; suction sampler; HELM project (samples S14_2F, S14_2M, S14_3F, S14_4F) • 1 v; west of Rosh HaNikra Islands; 33.0725°N, 35.0923°E; depth 20 m; 1 May 2018; rocky substrate; suction sampler; HELM project (sample S13_3M) • 1 spcm; same collecting data as for preceding; depth 19 m; 29 Oct. 2018; HELM project (sample S53_2L).

Malta • 9 spcms; off Filfla Island; on a rafting fisherman’s net; 1981 (P.G. Albano coll. ID 557).

Remarks.

We found several living individuals of Musculus coenobitus in northern Israel. It is the first record of this Red Sea species for the Mediterranean Sea. Musculus coenobitus is very similar to the native M. subpictus , which can occur sympatrically, but can be distinguished at once because of its reddish rather than greenish hue (Figure 34 ). It is also more elongated with a more pointed posterior margin. Juvenile specimens are bright red (Figure 35C ), have interspaces between the radial riblets in the posterior part of the shell almost as large as the riblets themselves, while in M. subpictus the riblets are closely arranged with very narrow interspaces (Figure 35E, J ). Musculus coenobitus also shows a fine but distinct lamellar concentric sculpture in such interspaces, whereas M. subpictus shows more sparse fine concentric ridges (Figure 35E and J , respectively). The relation of M. coenobitus with other Indo-Pacific species like M. cumingianus (Reeve, 1857) and M. cuneatus (Gould, 1861) deserves a revision ( Oliver 1992).

Figures

Figure 34. Comparison between Musculus coenobitus (Vaillant, 1865) and Musculus subpictus (Cantraine, 1835) A-D Musculus coenobitus, north of Nahariyya port, Israel, HELM project (sample H 3): right valve outer (A) and inner (D) views, left valve inner (B) and outer (C) views E-H Musculus subpictus, off Filfla, Malta: right valve outer (E) and inner (H) views, left valve inner (F) and outer (G) views. Scale bars: 5 mm.

Figure 35. Comparison between Musculus coenobitus (Vaillant, 1865) and Musculus subpictus (Cantraine, 1835) A-F Musculus coenobitus, west of Rosh HaNikra Islands, Israel, HELM project (sample S 52 _ 2 L): right valve outer (A, D) and inner (B) views, living specimen with byssus (C), sculpture of the posterior (E) and anterior (F) area of the right valve G-K Musculus subpictus, Ashqelon, Israel, HELM project (sample S 12 _ 1 L): right valve outer (G, I) and inner (H) views, sculpture of the posterior (J) and anterior (K) area. Scale bars: 1 mm (A, B, D, G-I), 2.5 mm (C); 0.5 mm (E, F, J, K).