Elasmopus yucalpeten, Paz-Rios, Carlos E. & Ardisson, Pedro-Luis, 2014

Paz-Rios, Carlos E. & Ardisson, Pedro-Luis, 2014, Elasmopus yucalpeten sp. n. (Crustacea, Amphipoda, Maeridae) from the northern Yucatan coast, with a key for the genus in the Gulf of Mexico and biogeographic comments, Zoosystematics and Evolution 90 (2), pp. 95-104 : 95-96

Taxon classification Animalia Amphipoda Maeridae

Elasmopus yucalpeten sp. n. Figures 1, 2, 3, 4

Type material.

Holotype male (dissected and drawn), 6.6 mm, Yucalpeten harbor, Yucatan, Mexico, 21°16.667'N, 89°42.001'W, 24 August 2010, on wood dock with algae, coll. C. E. Paz-Ríos, CYMX-1-EY. Paratypes: one female (dissected and drawn), 6.2 mm, data as for holotype, CYMX-2-EY; four males, four females, data as for holotype, ECOSUR0164; six males, Yucalpeten harbor, Yucatan, Mexico, 21°16.667'N, 89°42.001'W, 26 June 2012, on rock with algae, intertidal, coll. C. E. Paz-Ríos, CYMX-3-EY.

Other material.

Twenty-six males, 49 females, seven unsexed, data as for holotype, CYMX-4-EY.

Type locality.

Yucalpeten harbor, Yucatan, Mexico.

Diagnosis.

Body dorsally setose. Antenna 1 long. Accessory flagellum two-articulated. Eyes large, ovate. Group of five long robust setae on basis anterodistal margin of gnathopod 2. Medial concave portion on palm of gnathopod 2 propodus. Long setae on basis posterior margin of pereopods 5-7. One basofacial robust seta on peduncle of uropod 1. Telson entire.

Description.

Based on holotype male, 6.6 mm (CYMX-1-EY). Body with groups of one to three setae on head, pereon and pleon. Eyes large, ovate. Lateral cephalic lobe broad, rounded, anteroventral margin with notch/slit. Antenna 1 reaching beyond half of body, longer than antenna 2 (about 2 times the antenna 2 length); peduncular article 1 subequal in length to article 2, without robust setae on posterior margin; article 2 longer than article 3 (about 1.4 times the article 3 length); flagellum with 27 articles; accessory flagellum short, two-articulated, last article minute. Antenna 2 peduncular article 2 gland cone reaching beyond end of peduncular article 3; article 4 subequal in length to article 5, flagellum with nine articles. Lower lip outer lobes with single pair of ducts, mandibular lobes apically acute. Mandible molar well developed, triturative, with plumose seta; accessory setal row with four slender blades; palp three-articulated; article 1 about as long as broad, shorter than article 2; article 2 slightly longer than article 3, with few long slender setae; article 3 longer than article 1, weakly falcate, long (about 3.2 times as long as broad), with comb of short robust setae along anterodistal margin and three slender apical setae. Maxilla 1 inner fig with two apical plumose setae; outer fig with seven serrate robust setae; palp two-articulated, apical part of palp article 2 with seven robust and two slender setae. Maxilla 2 inner fig with five plumose setae and a few slender seate. Maxilliped inner fig with two slender and six plumose setae on apical part; outer fig bearing ten medial/apical robust setae and six apical plumose setae.

Gnathopod 1 subchelate; coxa anterior margin slightly concave, anteroventral corner produced and rounded, ventral margin with few long setae; basis posterior margin with four long setae; merus with posterodistal tooth; carpus about 1.5 times as long as broad, subequal in length to propodus, heavily setose, with rows of long setae covering the surface and posterior margin; propodus with few rows of long marginal and superficial setae, palm acute, convex, minutely serrate, defined by two posterodistal robust setae; dactylus with one seta on anterior margin. Gnathopod 2 subchelate; coxa subrectangular, longer than broad, ventral margin with some long setae; basis stout, posterior margin with four long setae, anterodistal margin with group of five long robust setae; merus anteroventral corner produced and subquadrate; carpus posteroventral corner produced, rounded and setose; propodus expanded, anterior and posterior margin with rows and clusters respectively of long slender setae; palm about half length of propodus, acute, sculptured, with palm distal shelf subrectangular bearing group of four robust setae, distal subquadrate tooth, medial concave portion for reception of the dactylar tip, defined by proximal tooth; dactylus falcate, with one seta on anterior margin. Pereopod 3 similar to pereopod 4, except by the coxa subrectangular. Pereopod 4 coxa longer than broad, posterior margin concave, posteroventral corner produced and rounded, ventral margin with long setae; basis posterior margin with three long setae; propodus with a row of seven robust setae on posterior margin; dactylus short (about 0.5 times the propodus length), dactylar unguis simple. Pereopod 5-6 coxa broader than long, excavate ventrally, anteroventral lobe produced and rounded, with three posteroventral robust setae; basis posterior margin slightly expanded convex, weakly crenulate, with many long stiff slender setae; ischium, merus, carpus and propodus with many long, slender and robust setae along margins; dactylus short (about 0.3 times the propodus length), dactylar unguis simple. Pereopod 7 similar to pereopod 5-6, except by the coxa with ventral lobe produced and rounded, with one posterior robust seta.

Epimera 1-3 posteroventral corner notched with small subacute tooth; ventral margin with long slender and robust setae. Urosomite 1-3 smooth, without carina. Uropod 1 peduncle with two basofacial robust setae, five robust setae on each of the outer and inner margins, and two long robust setae distally; inner ramus about as long as peduncle. Uropod 2 peduncle with two and three robust setae on outer and inner margin, respectively; inner ramus longer than peduncle (about 1.2 times the peduncle length). Uropod 3 peduncle with two distal robust setae; inner ramus about as long as peduncle; outer ramus slightly longer than inner ramus with three clusters of long setae. Telson entire with posterior margin scalloped, two unequal stout robust setae and two or three plumose setae on each side.

Female (sexually dimorphic characters); based on paratype female, 6.2 mm (CYMX-2-EY). Gnathopod 1 subchelate; coxa ventral margin with short setae; basis medial surface with two long setae, posterior margin with seven long setae; carpus heavily setose, with long setae covering the surface and posterior margin; propodus with marginal and superficial setae, palm acute, convex, minutely serrate, with ten submarginal robust setae, defined by two posterodistal robust setae, followed by two submarginal robust setae; dactylus not reaching the end of palm, with one seta on anterior margin. Gnathopod 2 subchelate; coxa ventral margin with some long setae; basis posterior margin with five long setae, anterodistal margin with one long robust setae; carpus heavily setose, with long setae covering the posterior margin; propodus anterior and posterior margin with rows and clusters respectively of long slender setae, about twice length of carpus, palm acute, nearly straight, smooth, with 15 submarginal robust setae, defined by three posterodistal robust setae; dactylus falcate, not reaching the end of palm, with one seta on anterior margin. Pereopod 5-7 with few long stiff slender setae. Uropod 1 peduncle with one basofacial robust seta.

Variations; based on paratypes (CYMX-2-EY, CYMX-3-EY, ECOSUR0164). A group of six robust setae (instead of five) on the anterodistal margin of the basis of gnathopod 2 was observed in two of the ten male specimens. Male and female specimens were also examined for confirming the presence of two robust setae on peduncle of uropod 1, but there was not consistency; the rule was to present one basofacial robust seta.

Etymology.

The species name is derived from the type locality of the new species. Yucalpeten in the Mayan language means "land of the deer".

Distribution.

So far only known from the type locality, Yucalpeten harbor, Yucatan, Mexico.

Habitat.

Marine epibenthic, in shallow water (≤1 m) on rocks and wood dock with the brown algae Gracilaria sp.

Remarks.

The presence of one or two basofacial robust setae on uropod 1 peduncle as a characteristic for species category identification may have been overlooked by earlier studies ( Hughes and Lowry 2011); these same authors also have pointed out that, the presence of two basofacial robust setae on uropod 1 peduncle may be result of a newly-forming moult stage, such as the present case, where only the holotype male bears those spines. Elasmopus yucalpeten sp. n. is distinguished from the rest of the species in the genus by having the antenna 1 accessory flagellum two-articulated, mandibular palp article 3 weakly falcate, gnathopod 2 basis anterodistal margin with group of long robust setae, gnathopod 2 propodus palm with medial concave portion, uropod 1 peduncle with one or rarely two basofacial robust setae, and telson entire. An entire telson is only known in four other species of the genus, Elasmopus integer Myers, 1989, Elasmopus pseudinteger Appadoo & Myers, 2003, Elasmopus takamotus Myers, 1986, and Elasmopus visakhapatnamensis Kanakadurga, Rao & Shyamasundari, 1981. Of these species, Elasmopus yucalpeten sp. n. is closely related to Elasmopus integer from Bora Bora, South Pacific, Elasmopus pseudinteger from Mauritius, Indian Ocean, and Elasmopus visakhapatnamensis from Visakhapatnam, Indian Ocean. It is distinguished from Elasmopus integer by the eyes ovate; mandibular palp article 3 weakly falcate; gnathopod 2 propodus palm with medial concave portion; pereopod 5-7 basis more setose; and epimera 2-3 posteroventral corner notched with small subacute tooth. It is distinguished from Elasmopus pseudinteger by the two-articulated accessory flagellum; the more setose mandibular palp article 2; the long slender setae along the anterior and posterior margin of the gnathopod 2 propodus; the entire, crenulate and more setose margin of the pereopod 5-6 basis; the margin evenly convex of the epimeron 3 with the posteroventral corner notched and a small subacute tooth; the presence of one basofacial robust setae on the uropod 1 peduncle; and a telson with a scalloped posterior margin. Finally, it is distinguished from Elasmopus visakhapatnamensis by the following characteristics: mandibular palp article 3 weakly falcate; gnathopod 2 propodus palm with medial concave portion and proximal tooth; epimeron 1-3 margin evenly convex with posteroventral corner notched, having a small subacute tooth; and uropod 3 outer ramus longer than inner ramus.