More than one: A second eastern Pacific species of Cymothoa (Crustacea: Isopoda) in the SE Gulf of California, Mexico.

A second species of "tongue-eaters," the cymothoid isopod Cymothoa facimar sp. nov., is described from the coasts of Sinaloa on the Mexican Pacific coast. Twenty-seven females and five males of the new species were collected from the oral cavity of the snappers Lutjanus peru and L. aratus caught for sale in Mazatlán fish markets. The new species is morphologically similar to C. exigua, the previously known species reported from the Eastern Pacific, in general shape of body, cephalon, the anterior pereonites, pereopods and pleotelson; however, they can be easily differentiated because adult females of the new species are larger and slender than those of C. exigua and because they show differences in the dorsal surface of pereonites, the shape of the seventh pereonite and cephalon and the relative size of exopodite and endopodite of the uropods. The new species is morphologically similar to C. exigua, the only species of Cymothoa described so far from the Eastern Pacific, particularly in the general shape of the body, cephalon, anterior pereonites, pereopods, and pleotelson. Nonetheless, it can be readily distinguished from C. exigua by several diagnostic features: adult females attain larger body sizes and exhibit a slenderer morphology especially in the ovigerous females; additionally, differences are present in the dorsal sculpturing of the pereonites, the shape of the sixth and seventh pereonites, and the relative proportions of the exopodite and endopodite of the uropods. Cymothoa facimar sp. nov. resembles C. excisa, a species reported from the western Atlantic. Still, the two species can be differentiated by the relative length of the fourth pereonite, which is more prominent in the Atlantic species. The new species is described herein, and a discussion on the status of C. exigua is presented in reports from other regions of the Eastern Pacific.Zoobank registration: http://zoobank.org/urn:lsid:zoobank.org:pub:E5B44B8C-DFD2-423A-A554-62A2D4FB464F       http://zoobank.org/urn:lsid:zoobank.org:act:D3FADC01-5267-4DE4-AB15-A98C01F1B876.