Elasmopus lecroyae, García-Madrigal, María Del Socorro, 2010

García-Madrigal, María Del Socorro, 2010, Littoral Maeridae and Melitidae (Amphipoda: Gammaridea) from the Gulf of Tehuantepec, Mexico, Zootaxa 2623, pp. 1-51 : 22-23

Elasmopus lecroyae n. sp.

( Figs 11 , 12 )

Type material: 58 specimens: UMAR-PERA-270, holotype male (6 mm), paratype female (5.5 mm); paratypes: 2 males, 3 females (one specimen mounted), 9 juv (Estacahuite beach, August 25, 2006, coral rock 4 m, coll. R. Bastida et al.); UMAR-PERA-267, 5 males (one specimen mounted), 2 females, 35 juv (Puerto Angel, May 20, 2007, piles of the dock 0.5 m, coll. F. Cortés).

Additional material: 71 specimens: UMAR-PERA-265, 4 males, 4 females, 11 juv (Carrizalillo Beach, August 12, 2006 in bivalve, coll. I. Gutiérrez); UMAR-PERA-266, 3 males, 1 female (Panteon beach, March 23, 2007, coral rock 3 m, coll. V. Mata); UMAR-PERA-268, 4 males, 5 females, 2 juv (Estacahuite beach, April 9, 2005, coral rocks 2–4m, coll. R. Bastida et al.); UMAR-PERA-269, 4 males (Estacahuite beach, September 10, 2005, coral rock, 2–4 m coll. R. Bastida et al.); UMAR-PERA-271, 1 male, 4 females, 4 juv (Estacahuite beach, July 3, 2007, intertidal coral rock, coll. J. Jarquín et al.); UMAR-PERA-272, 4 males, 2 females, 11 juv (La Tijera beach, September 12, 2006, coral rock 4 m, coll. R. Bastida et al.); UMAR-PERA- 273, 1 male, 1 female, 5 juv (La Entrega Bay, July 4, 2007, intertidal algae, coll. B. Martínez et al.).

Description: based on paratype male, 7.6 mm, UMAR-PERA-267, and holotype male, 6 mm, UMAR- PERA-270.

Head: long, length is less than the two first segments of pereon; anterior head lobe rounded, inferior antennal sinus in a projecting lobe. Eyes: long, subrounded, pigment light brown, width represents more than 1/3 the length of head. Antenna 1 is 3/5 the length of the body, first article of peduncle is the same size as the second article; length of third article is 1/2 the length of second article of peduncle; accessory flagellum with two articles, first article 1/3 longer than the second. Antenna 2 setose, the length is approximately 2/3 the length of the antenna 1, the length of fourth article is subequal to fifth article; first article of flagellum is 1/5 the length of the fourth article of peduncle.

Pereon: medium body, length is 2/5 larger than the length of the antenna 1; dorsally smooth; color offwhite in alcohol. Coxa 1 is shorter than coxae 2–4; ventral margin of coxae 1–4 with long simple setae, formula for coxae 1–4: 10–7–5–9; anterior margin of coxa 1 emarginated and its anterior angle projected; coxa 2 oval, with rounded ventral margin; coxa 3 narrow, subrectangle and lateral margins straight and parallel; coxa 4 the same width as coxa 1; posterior margin of coxa 4 distinctly emarginated; coxa 5–6 with short robust setae, formula for coxae 5–6: 4–3; coxa 7 semicircular shape, with two short simple setae. Gnathopod 1 with suboval propodus; palm margin with numerous short robust setae, one longer robust setae at inner angle than those on the palm margin. Gnathopod 2: length propodus is 2/3 longer than the dactyl; palm slightly oblique, partially concave with scarce medium-sized simple setae; palm with two submarginal hump near dactylar hinge: the first hump is quadrangular to semicircular with five short robust setae on outer face and three short robust setae on inner face, and the second is a subcolumnar tooth, bare, with truncated distal margin, close to first hump; between those teeth on palm margin there is a vestigial tooth; palm defined by a large cuspidate seta; posterior margin of hand with scarce medium-sized simple setae. Posterior margin basis of pereopods 1–5 with long simple setae; basis pereopods 3–4 with posterior margin nearly straight and pereopod 5 with posterior margin rounded; basis of pereopods 3–5 gradually widened and minutely serrated; merus of pereopods 3–5 with a oblique posterior margin and ample on distal margin.

Pleon: epimera continuous with respect to general line of the body; epimeron 3 lightly convex and protrusive on posterior edge, armed with four sharp denticles and two truncate denticles, ventral edge bearing short robust setae, formula for epimera 1–3 is 1:3–2, 2:2–3, 3:1–1–2–2–2, with one long simple seta on each of the last three positions. Uropod 3: peduncle 1/5 shorter than the outer ramous, inner ramous is the same size as the peduncle, inner margin of inner ramous bears two short robust setae near peduncle hinge, external margin of outer ramous with two clusters of medial robust setae and one robust seta proximal to peduncle. Telson deeply cleft, with protrusive apices submarginally placed, laterally defined by sinus and sharp tooth, with two small robust setae submarginal to sinus, inner seta smaller than the outer seta, length of outer robust seta is 2/3 shorter than the length of lobe.

Female: based on paratype females, 4.7 mm, 5.5 mm, UMAR-PERA-270. Inner margin of the palm of gnathopod 2 with small robust setae, length of dactyl less than 1/2 the length of propodus; two robust setae at inner angle longer than of those of palm margin, of these setae, marginal seta is 2/3 longer than the submarginal seta. Basis of pereopods 1–3 with long simple setae and pereopods 4–5 with simple setae of short to medium. Formula for epimera 1–3 is 1:2, 2:1–2–2, 3:1–1–2–2–2 without setae. Uropod 3 with inner ramous 1/5 smaller than the outer ramous, inner margin of inner ramous bare, external margin of outer ramous with only two clusters of medial robust setae. Telson resembles male, but the length of outer robust seta is 1/3 shorter than the length of lobe.

Variations: submargin of the palm of subadult males has subrounded first tooth, with three spines on outer face and three spines on inner face; on the palm margin there is a sharp tooth near setose hump, the second submarginal tooth is subcolumnar. Posterior margin of epimeron 3 with two sharp denticles and two truncated denticles. The formula for epimera has two variations: the first is 1:3–2, 2:1–3–2–3, 3:1–1–1–1–2– 2–2, with one simple seta on epimeron 3 in the antepenultimate three positions, and second is 1: 3–2, 2: 2–3– 1–3, 3:1–1–1–2–2–2–2 with one simple seta on epimeron 3 in the last three positions. Females and subadult male with the second article of accessory flagellum the same length as the first article; accessory flagellum of juveniles only has one article.

Etymology: the specific name is dedicated to the Dr. Sara LeCroy for her remarkable dedication to the amphipods taxonomy.

Taxonomic comments: Elasmopus lecroyae n. sp. is observed as a species in between E.? rapax Barnard, 1962 , E. bampo Barnard, 1979 and E. mayo Barnard, 1979 ; but is most similar to E. mayo ; therefore, it is compared with this, the comparison is made between males. There are three short robust setae on the anterior margin of the second article of antenna 2 in Elasmopus mayo while in E. lecroyae n. sp. it is bare. Elasmopus lecroyae n. sp. has three sets of robust setae on anterior margin of the third article of antenna 1, while E. mayo is bare. Accessory flagellum of E. lecroyae n. sp. has two articles, while E. mayo has three articles. Setose hump near dactylar hinge of gnathopod 2 of Elasmopus lecroyae n. sp. has on outer and inner face with five and three short robust setae respectively, while E. mayo has three and four short robust setae respectively. On the distal margin the third article of mandibular palp of Elasmopus mayo has three long simple setae, while E. lecroyae n. sp. has four long simple setae. The right lacinia mobilis of Elasmopus mayo has five denticles and a smaller thumb, while E. lecroyae n. sp. has four denticles and a large thumb. The ventral margin of coxa 4 of Elasmopus mayo bears two large simple setae, while E. lecroyae n. sp. has nine large simple setae. Telson of E. lecroyae n. sp. has convex apices with complete lobes, laterally defined by a shallow sinus, two robust setae on each lobe, and lateral margin with two short simple seta while E. mayo lobes are nearly incomplete, laterally defined by sinus, one to two robust setae on each lobe and lateral margin with one short simple seta. The formula for epimera 1–3 of E. mayo is 1:1–2, 2:1–4–2–3, 3:1–1–1–2–3–2, with one long simple seta on the last two positions on epimeron 3, while in E. lecroyae n. sp. it is 1:3–2, 2:2–3, 3:1–1–2–2–2, with one long simple seta on the last three positions on epimeron 3. In E. lecroyae n. sp. the epimeron 3 has a convex posterior margin bearing five sharp denticles, becoming blunter, the second sinus has one short simple seta; while E. mayo has a nearly straight posterior margin armed one to two notches bearing short simple setae. Telson of the females of E. mayo has three robust setae on each lobe while E. lecroyae n. sp. has two spines on each lobe. Also, the basis of the pereopods 1–3 of female of E. lecroyae n. sp. has some posterior long setae, while the female of E. mayo has lost the long setae.

Figures

FIGURE 11. Elasmopus lecroyae n. sp., paratype, male, 7.6 mm, UMAR-PERA- 267, Puerto Angel, Oaxaca: A) habitus; B) coxa 1; C) coxa 2; D) coxa 3; E) coxa 4; F) coxa 5; G) coxa 6; H) coxa 7; I) accessory flagellum; J) antenna 1; K) antenna 2; L) gnathopod 2, external side with details of palm margin without setae; M) gnathopod 2, internal side with details of palm margin without setae; N) gnathopod 1, internal side; O) gnathopod 1, external side; P) uropod 1; Q) uropod 2; R) uropod 3.

FIGURE 12. Elasmopus lecroyae n. sp., paratype, male, 7.6 mm, UMAR-PERA- 267, Puerto Angel, Oaxaca: A) epimera; B) telson; C) pereopod 1; D) pereopod 2; E) pereopod 3; F) pereopod 4; G) pereopod 5; H) lower lip; I) upper lip; J) maxilliped; K) right mandible; L) left lacinia mobilis; M) maxilla 2; N) maxilla 1. Paratype, female, 4.7 mm, UMAR-PERA- 270, Estacahuite beach, Oaxaca: O) telson; P) uropod 3; Q) gnathopod 1, external side; R) gnathopod 1, internal side; S) gnathopod 2, external side; T) gnathopod 2, internal side.