Elasmopus lejeunei, Souza-Filho, Jesser F. & Senna, André R., 2009

Souza-Filho, Jesser F. & Senna, André R., 2009, Two new species of the genus Elasmopus Costa, 1853 (Amphipoda: Gammaridea: Maeridae) from off the Northeast Brazilian Coast, Zootaxa 2301, pp. 55-68 : 61-66

Elasmopus lejeunei sp. nov.

Figures 4–6

Material examined. Holotype. Male 5.2 mm, Rio Grande do Norte State, #BPot 38, fine sand with organism fragments, 4º47’32”S - 36° 50º13”W, 15 m, N. Oc. Astro Garoupa col., 29/IV/2004, MNRJ 21580.

Paratypes. Rio Grande do Norte State, # BPot 38, fine sand with organism fragments, 4º47’32”S - 36° 50º13”W, 15 m, N. Oc. Astro Garoupa col., 29/IV/2004, MNRJ 21584, 1 female (dissected and drew). Rio Grande do Norte State, # BPot 38, fine sand with organisms fragments, 4º47’32”S - 36° 50º13”W, 15 m, N. Oc. Astro Garoupa col., 29/IV/2004, MNRJ 21584, 1 male and 3 females. Atol das Rocas, Rio Grande do Norte State, intertidal, P.S. Young, P.C. Paiva and A.A. Aguiar col., XI/2000, MNRJ 21583, 1 male and 4 female. REVIZEE Score NE, #223-I, gravel, 02°04’48”S- 39°28’48”W, 22 m, N. Oc. Antares col., 16/V/1998, DOUFPE 14047, 7 males and 16 females. REVIZEE Score NE, # 40-III, gravel, 04°05’24”S- 37°25’48”W, 50 m, N. Oc. Antares col., 15/V/1998, DOUFPE 14048, 1 male.

Etymology. The species is named in honor to Dr. Lejeune de Oliveira for his contribution on the Brazilian amphipod taxonomy during the first part of the 20th century.

Diagnosis. Gnathopod 2 with propodus suboval, setose along posterior and anterior margin; palm extremely acute, reaching along entire posterior margin, convex, with some poorly developed tubercles, without robust setae, inner face with a weakly developed process near hinge of dactylus with 6 robust setae followed by 2 tubercles, each one of them with 2 robust setae, with a ridged line about 1/3 of propodus length with perpendicular lines of setae extending towards insertion of dactylus. Pereopod 5 basis, posterior margin concave and serrate. Pereopod 6 basis, posterior margin nearly straight and serrate. Epimeron 3 produced in a curved sharp spine. Uropod 3 outer ramus about 1.7 X peduncle length, inner ramus subequal to outer ramus length. Telson cleft, each lobe notched with 2–3 apical robust setae.

Description. Based on holotype male, 5.2 mm. Head with large eyes, rounded, with distinct ommatidia; lateral cephalic lobes broad, truncated, with anteroventral notch and slit, anteroventral corner rounded. Antenna 1 longer than antenna 2, about 0.75 X body length; peduncular article 1 1.1 X length of article 2, with 3 robust setae along posterior margin, article 2 2.1 X length of article 3; flagellum longer than peduncle with about 23 articles; accessory flagellum with 3 articles. Antenna 2 extending beyond to end of peduncle of antenna 1; glandular cone extending beyond end of article 3; peduncular article 4 1.1 X length of article 5; flagellum with 9 articles. Mandible palp article 2 with setae along inner margin; article 3 falcate, setose along concave margin, subequal to article 2. Maxilla 1 inner plate with 2 apical plumose setae, outer plate with 7 robust setae, palp with rows of distal and facial setae. Upper and lower lip, maxilla 2 and maxilliped with basic characters for the genus.

Gnathopod 1, subchelate; coxa with anteroventral corner produced, rounded, ventral margin with some long setae; basis, posterior margin with 2 long setae; merus without posterodistal spine, densely setose on posterior margin and distally; carpus about 1.7 X as long as broad, posterior margin densely setose; propodus subequal to carpus, with long facial and marginal setae; palm acute, serrate and convex with 9 robust setae along its margin, defined by a long robust setae and a cluster of 3 robust setae; posterior margin with 2 robust setae; dactylus not reaching the of end palmar serration; posterior margin with 2 robust setae. Gnathopod 2 subchelate; basis with 3 long setae on posterior margin; merus with posteroventral corner produced into a long and acute spine; carpus posteroventral corner produced, acute and setose; propodus suboval, setose along posterior and anterior margin; palm extremely acute, reaching along entire posterior margin, convex, with some poorly developed tubercles, without robust setae, inner face with a weakly developed process near hinge of dactylus with 6 robust setae followed by 2 tubercles, each one of them with 2 robust setae, with a ridged line about 1/3 of propodus length with perpendicular lines of setae extending towards insertion of dactylus; dactylus strongly curved, posterior margin sinuous, apically blunt. Pereopod 3, coxa longer than wide (1.8 X); basis without long setae on posterior margin; merus subequal to propodus length with anterodistal angle slightly produced; carpus with 7 robust setae on posterior margin; propodus with 8 robust setae on posterior margin; dactylus short, about 0.4 X propodus length. Pereopod 4 similar to pereopod 3, but coxa 1.2 X as long as wide with posterior margin excavate; basis with 3 long setae, and propodus with 12 robust setae along posterior margin. Pereopod 5 coxa wider than long, anteroventral lobe produced; basis posterior margin slightly concave, serrate, with short setae, posteroventral corner subquadrate; merus with anteroventral corner produced about 0.21 X carpus length. Pereopod 6 coxa wider than long, anteroventral lobe produced; basis posterior margin nearly straight, serrate, with short setae; posteroventral corner subquadrate; merus with anteroventral corner produced about 0.25 X carpus length. Pereopod 7 coxa with posterior lobe produced ventrally; basis posterior margin convex and serrate with short setae, posteroventral corner rounded; merus with anteroventral corner produced about 0.26 X carpus length; propodus 1.6 X carpus length, posterodistal angle slightly expanded, posterior margin with 3 tufts of long setae.

Epimeron 1 and 2 posteroventral corner produced in a spine. Epimeron 3 posterior and posteroventral margin smooth, posteroventral corner produced in a curved and acute spine. Uropod 1 peduncle with basofacial a robust seta, 7 and 8 robust setae along outer and inner lateral margin, respectively, and two displaced robust setae distally, without distoventral spur; outer ramus shorter than inner ramus, with 6 marginal robust setae and 3 distal robust setae; inner ramus about 0.8 X peduncle length, with 3 marginal robust setae and 4 distal robust setae. Uropod 2 peduncle with 4 robust setae on inner margin and one distal robust setae on outer margin; outer ramus shorter than inner ramus, with 7 robust setae; inner ramus about 1.3 X peduncle length with 5 marginal robust setae, 4 basofacial robust setae and 3 distal robust setae. Uropod 3 peduncle with one basofacial robust setae, 3 distoventral robust setae, outer lateral margin with 2 distal robust setae and inner lateral margin with one medial and 3 distal robust setae; outer ramus about 1.4 X peduncle length with 3 comb of long and robust setae; inner ramus subequal to outer ramus with inner margin naked. Telson cleft (77%), each lobe with distal notch bearing 2 apical robust setae, the longer seta slightly overreaching the tips of each lobe.

Female (sexually dimorphic characters)

Based on paratype, female, 5.3 mm. Gnathopod 1 basis with 9 long setae on posterior margin and 5 facial long setae; carpus not lobate, posterior margin densely setose; propodus longer than carpus (1.25 X), palm acute, convex, serrate, with 9 marginal robust setae, palmar corner defined by one long robust setae and others 3 short robust setae; palmar serration slightly surpass the palmar corner; posterior margin with 3 robust setae; dactylus reaching the end of palm. Gnathopod 2 basis slender, posterior margin with 3 long setae, anterior margin with 7 slender setae; merus posterodistal angle produced in a large spine; carpus 0.6 X propodus length with one robust seta on anterior margin, posterodistal angle slightly produced, posterior margin densely setose; propodus 2.3 X as long as wide, posterior margin subparallel to anterior margin with marginal long setae; palm acute, nearly straight, smooth, with a small serrate hump near hinge of dactylus, with 8 marginal robust setae; palmar corner with 2 robust setae; dactylus reaching end of palm. Telson, each lobe with 2 lateromarginal setae, and 2 distal setae, one of them longest about 0.7 X telson length.

Remarks. Elasmopus lejeunei sp. nov. is similar to E. balkomanus and E. lemaitrei in having the propodus of gnathopod 2 ovate without palmar corner, posterior margin of basis of pereopod 5 concave, rami of uropod 3 longer than peduncle and epimeron 3 produced in a sharp spine. However, E. lejeunei sp. nov. differs from both in having a weakly developed process near hinge of dactylus of gnathopod 2 with some robust setae (well developed in E. lemaitrei and absent in E. balkomanus ) followed by two tubercles and one ridged line about 1/3 of propodus length with perpendicular lines of setae on inner face (absent in E. lemaitrei and about 1/ 2 in E. balkomanus ). Also, E. lejeunei sp. nov. differs from E. lemaitrei in having large and rounded eyes, 3-articulate accessory flagellum of antenna 1, less setose gnathopod 1 and 2 and basis of pereopod 6 with nearly straight posterior margin.

Geographic distribution. Brazil: Atol das Rocas; off Ceará State coast; and Potiguar Basin, off Rio Grande do Norte State coast ( Figure 7 ).

Figures

FIGURE 4. Elasmopus lejeunei sp. nov. Holotype, male, 5.2 mm, Rio Grande do Norte State, # BPot 38, 4 º 47 ’ 32 ” S - 36 ° 50 º 13 ” W, 29 / IV / 2004, MNRJ 21580. Scale bars = 0.2 mm.

FIGURE 5. Elasmopus lejeunei sp. nov. Holotype, male, 5.2 mm, Rio Grande do Norte State, # BPot 38, 4 º 47 ’ 32 ” S - 36 ° 50 º 13 ” W, 29 / IV / 2004, MNRJ 21580. Paratype, female, 5.3 mm, Rio Grande do Norte State, # BPot 38, 4 º 47 ’ 32 ” S - 36 ° 50 º 13 ” W, 29 / IV / 2004, MNRJ 21584. Scale bars = 0.2 mm.

FIGURE 6. Elasmopus lejeunei sp. nov. Holotype, male, 5.2 mm, Rio Grande do Norte State, # BPot 38, 4 º 47 ’ 32 ” S - 36 ° 50 º 13 ” W, 29 / IV / 2004, MNRJ 21580. Paratype, female, 5.3 mm, Rio Grande do Norte State, # BPot 38, 4 º 47 ’ 32 ” S - 36 ° 50 º 13 ” W, 29 / IV / 2004, MNRJ 21584. Scale bars = 0.1 mm for mT and fT; 0.2 mm for the remains.

FIGURE 7. Distribution of Elasmopus karamani sp. nov. and E. lejeunei sp. nov.; circle (●): occurrence of E. karamani sp. nov.; triangle (˔): occurrence of E. lejeunei sp. nov.; square (․): occurrence of both species.