Leptalpheus mexicanus Ríos & Carvacho, 1983

Salgado-Barragán, José, Ayón-Parente, Manuel & Hendrickx, Michel E., 2014, A new species of Leptalpheus Williams, 1965 and new records of L. mexicanus Ríos & Carvacho, 1983 and L. hendrickxi Anker, 2011 (Crustacea: Decapoda: Alpheidae) from the Pacific coast of Mexico, Zootaxa 3835 (4), pp. 573-582 : 580-581

Leptalpheus mexicanus Ríos & Carvacho, 1983

Figs. 6 A–F

Leptalpheus mexicanus Ríos & Carvacho 1983: 306 , figs. 1–3; Ramos 1995: 131, fig. 1.

Material examined. 2 females (CL 5.1–6.3 mm), Estero de Urías, Mazatlán, Sinaloa, Mexico, 23°12'28.6" N, 106°24’05” W, mudflat, yabby pump, 1 December 2010 (EMU-8784).

Distribution. Estero Mulegé, Baja California Sur (type locality), and Manzanillo, Colima, Mexico, to Bahía Málaga, Colombia ( Ríos & Carvacho 1983; Ramos 1995; Lazarus-Agudelo & Cantera-Kintz 2007). Ecology. The specimens were collected on a mudflat, in burrows of unknown hosts.

Remarks. According to Anker (2011), Leptalpheus mexicanus and L. bicristatus are very similar, the later being distinguished from the former mainly by the presence of a small crest on the carapace above each eye, and the shape of the lateral lobe of the uropodal protopod. Although of small size, these crests are very conspicuous in L. bicristatus , particularly in lateral view (see Anker 2011: Fig. 15A, B). A topotypical specimen of L. mexicanus deposited in the Muséum National d'Histoire Naturelle, Paris, France (MNHN Na13624), examined by Anker (2011: 22) apparently did not have these crests. The holotype (female) and the allotype (male) of L. mexicanus were originally deposited at the Colección Nacional de Crustáceos (CNCR), in Mexico D.F., but are currently on loan to Darryl L. Felder of the University of Louisiana. On our request, D. L. Felder revised the two type specimens and provided illustrations of the lateral view of the frontal area of the carapace ( Fig. 6 E, F). These figures show that both type specimens of L. mexicanus possess a very low crest above each eye, a character which was not mentioned nor illustrated by Ríos & Carvacho (1983) in their original description of the species. Ramos (1995) reported L. mexicanus from Colombia, not illustrating these crests in his material (see Ramos 1995: fig. 1); however, his drawings are rather diagrammatic and may not be accurate. Nevertheless, the presence or absence of the carapacial crests above the eyes can no longer be used as a distinctive character between L. mexicanus and L. bicristatus . Unfortunately, the other two paratypes of L. mexicanus , deposited at the CICESE, Ensenada, Mexico, are no longer available. The other important characters in distinguishing L. mexicanus from L. bicristatus are the size and shape of the marginal tooth of the uropodal protopod. The material of L. mexicanus from Estero de Urías (EMU-8784) features two short teeth separated by a shallow concavity ( Fig. 6 D), much similar to what is illustrated by Anker (2011) for L. bicristatus . Consequently, both characters cited hereabove should no longer be considered valid for separating one species from the other.

Anker (2011) mentioned other morphological differences between L. bicristatus and L. mexicanus based on a comparison between his single specimen, a male of 4.6 mm CL from Chame Bay, Panama, and the illustrations provided by Ríos and Carvacho (1983). He noted that the major cheliped of L. bicristatus is stouter than in L. mexicanus , the anterior margin of the antennal scaphocerite of L. bicristatus is less convex than in L. mexicanus , the first carpal article of the second pereiopod is relatively longer in L. bicristatus , and that the two species also differ in the shape of the lateral tooth of the protopod (cf. Ríos & Carvacho 1983: fig. 1e and Anker 2011: fig. 15I). We consider, however, that these characters are very relative and might reflect an intraspecic variation. We are reluctent to include L. bicristatus in the synonymy of L. mexicanus and, as pointed out by Anker (2011), additional material of both nominal species should be collected from the type localities and within their distribution range, and carefully examined. Additionally, a molecular comparison would be highly desirable.

Figures

FIGURE 6. Leptalpheus mexicanus Ríos & Carvacho, 1983, female (A – D, EMU- 8784). A, anterior part of carapace and appendages, dorsal view; B, anterior part of carapace, lateral view; C, major cheliped, lateral view; D, right uropod and telson. Leptalpheus mexicanus Ríos & Carvacho, 1983 (E – F, CNCR- 2506); E, female holotype, anterior part of carapace, lateral view; F, male allotype, anterior part of carapace, lateral view. Scale bars = 1 mm.