Cheiriphotis mediterranea (Myers, 1983)

Lo Brutto, Sabrina, Schimmenti, Eugenia, Iaciofano, Davide, Lubinevsky, Hadas, Cesari, Michele & Guidetti, Roberto, 2022, The morphological diversity within a species can obscure the correct identification, Zoologischer Anzeiger 299, pp. 106-114 : 112-113

4.1. How to differentiate C. mediterranea from similar congeneric species

C. mediterranea is a species that has been defined as being similar to two other congeneric species: Cheiriphotis neotropicalis Val´erio-Berardo et al., 2007, present in the Atlantic Ocean, and Cheiriphotis williamsoni Salman & Jabbar, 1990 , present in the Indo-Pacific area. Both these two species, biogeographically distant, display the shape of gnathopod 2 overlapping with the shape of gnathopod 2 of C. mediterranea . This appendage is characterized by the peculiar processes/lobes/teeth, and the U-shaped excavation close to the posterodistal corner of the propodus palm ( Fig. 7 ). Our observations have highlighted a diagnostic character that can help in species delimitation, that is the shape of the telson: C. mediterranea displays a telson with an incision and strong distolateral crests; the telson of C. williamsoni is uncleft with two groups of 3 subapical setae and 2 lateral setae on each side; and the telson of C. neotropicalis is uncleft with a naked, lateral margin ( Fig. 7 ; Table 2). Though the neotropicalis - mediterranea - williamsoni triad shares marked similarities, it shows such diagnostic character and maybe dissimilarities that are not easy to detect ( Table 2). Comparative, morphological and molecular studies among the three species are required.

The status of endemicity of C. mediterranea within the Mediterranean Sea can’ t be proven in the present study as our sampling was only carried out along the Israeli coast. Further records should assume relevance in the light of the current northern forward expansion range towards Turkish coast (Bakir & Katagan ˘2014), and monitoring is advisable.

According to literature, C. mediterranea and C. williamsoni are two of the three species, including Cheiriphotis erythraeus Ruffo, 1969 present along the coast of the Mediterranean-Arabian province, from the Eastern Mediterranean Sea to Iran and the Arabian Peninsula ( Fig. 8 ). C. mediterranea is morphologically easily distinguishable from its neighbour C. erythraeus by specific features: the shape of the C. erythraeus propodus palm is markedly different, with a produced forward and deep incision, followed by a bifurcate lobe with a dovetail-shape located in the corner ( Fig. 8 ).

Regarding mediterranea vs williamsoni , taking into consideration the revised description of C. mediterranea here reported, the diagnostic characters of these two species have been compared and re-assessed. According to Salman & Jabbar (1990), C. mediterranea is close to, but distinct from C. williamsoni , on account of the subtriangular shape (not subquadrate as in C. williamsoni ) of the male gnathopod 2 propodus of C. mediterranea . Such a consideration arises from the original drawing of C. mediterranea ( Myers, 1983) , which shows the gnathopod 2 propodus as being subtriangular in shape, although there is no reference to this in the text of the description. On the contrary, the present revised description shows the propodus as being clearly subquadrate or quadrate in adult males (see Fig. 7D ), casting doubt on Myers’ (1983) drawing ( Fig. 7 ). The description of C. williamsoni by Salman & Jabbar (1990) is close enough to the present re-description, excluding various male characteristics: the carpus of the adult male gnathopod 1 is slightly shorter than its propodus, and the carpus of the young male gnathopod 2 is still incompletely separated from the propodus (in adults the carpus is completely fused with propodus).

C. mediterranea and C. williamsoni are separated by the break-area of the Red Sea, where C. erythreaus occurs, and thereby providing further support for its status as bona species. The occurrence of a single

Protection and Energy through the national monitoring program in Israel’ s Mediterranean Waters. The authors are grateful to Bella Galil for having coordinated the sampling effort that was led during the years 2005–2012. The work was also partially funded by the University of Palermo and by the E. Schimmenti PhD grant.

The authors are grateful to the anonymous reviewers for their helpful comments and suggestions on the earlier draft of this paper.

Figures

Fig. 7. Iconography of adult male gnathopod 2 and telson in: (A) Cheiriphotis mediterranea from Myers 1983; (B) Cheiriphotis neotropicalis from Val´erio-Berardo et al., 2007; (C) Cheiriphotis williamsoni from Salman & Jabbar 1990; (D) photo of adult male gnathopod 2 in Cheiriphotis mediterranea scored in the samples (see text for details). The original drawing in (A) of C. mediterranea (Myers 1983) shows the gnathopod 2 propodus as being subtriangular in shape; on the contrary, the present re-description shows the propodus as being clearly subquadrate or quadrate in adult males (D).

Fig. 8. Cheiriphotis erythraeus male gnathopod 2 (on the left), and the map of distribution range of C. erythraeus (triangle), Cheiriphotis mediterranea (circle), and Cheiriphotis williamsoni (square).