Elasmopus tubar Barnard, 1979

García-Madrigal, María Del Socorro, 2010, Littoral Maeridae and Melitidae (Amphipoda: Gammaridea) from the Gulf of Tehuantepec, Mexico, Zootaxa 2623, pp. 1-51 : 7-16

Elasmopus tubar Barnard, 1979

( Figs 3 , 4 )

Elasmopus tubar Barnard, 1979: 79 , figs. 42–43.

Type locality: 11 km to east of Cabo San Lucas, Gulf of California.

Distribution: Gulf of California: to east of Cabo San Lucas; Galapagos Islands.

Habitat: depth 0–4 m; wash of Padina , intertidal algae, algae from tide pool, coral rock, calcareous algae, sediments from coral rock.

Material examined: 1090 specimens: UMAR-PERA-227, 4 males, 6 females, 4 juv ( Santa Elena, March 11, 2004, intertidal algae, coll. R. Bastida); UMAR-PERA-327, 34 males, 131 females, 207 juv (San Agustinillo beach, July 3, 2007, intertidal algae, coll. J. Jarquín et al.); UMAR-PERA-228, 25 males, 32 females, 164 juv (Playa del Amor, Zipolite, July 3, 2007, algae from tide pool, coll. J. Jarquín et al.); UMAR- PERA-229, 3 males, 4 females, 3 juv (Puerto Angel, May 20, 2007, piles of the dock 0.5 m, coll. F. Cortés); UMAR-PERA-230, 30 males (one male on slide), 58 females (one specimen mounted), 10 juv (Aguete beach, August 25, 2005, intertidal algae, coll. R. Bastida et al.); UMAR-PERA-231, 9 males, 10 females, 10 juv (Estacahuite beach, April 9, 2005 algae on rocks 2–4 m, coll. R. Bastida et al.); UMAR-PERA-233, 1 female (Estacahuite beach, April 9, 2005, coral rock 2–4 m, coll. R. Bastida et al.); UMAR-PERA-232, 24 males, 22 females, 22 juv (Estacahuite beach, April 18, 2005, coral rocks 1–1.5 m, coll. S. García et al.); UMAR-PERA- 234, 1 male, 7 females, 7 juv (Estacahuite beach, September 10, 2005, intertidal calcareous algae, coll. R. Bastida et al.); UMAR-PERA-235, 1 male, 3 juv (Estacahuite beach, September 10, 2005, intertidal filamentous algae, coll. R. Bastida et al.); UMAR-PERA-236, 6 male, 6 females, 6 juv (Estacahuite beach, August 25, 2006, coral rock 2–4 m, coll. R. Bastida et al.); UMAR-PERA-237, 1 male, 3 females, 8 juv (Estacahuite beach, December 1, 2006, sediments of coral rock 4 m, coll. R. Bastida et al.); UMAR-PERA- 238, 3 males, 2 females, 2 juv (Estacahuite beach, July 3, 2007, intertidal coral rock, coll. J. Jarquín et al.); UMAR-PERA-239, 1 male, 1 female, 9 juv (Estacahuite beach, July 3, 2007, intertidal algae, coll. J. Jarquín et al.); UMAR-PERA-240, 23 males, 17 females, 16 juv (La Tijera beach, April 30, 2005, sediments from coral rock 4 m, coll. R. Bastida et al.); UMAR-PERA-241, 5 males, 8 females, 8 juv (La Tijera beach, September 12, 2006, coral rock 4 m, coll. R. Bastida et al.); UMAR-PERA-242, 2 males, 7 females, 17 juv (Maguey Bay, July 4, 2007, coll. B. Martínez et al.); UMAR-PERA-243, 6 males, 30 females, 23 juv (El Arrocito beach, May 23, 2000, sediments from coral rock, coll. S. Salazar et al.); UMAR-PERA-244, 5 males, 9 females, 34 juv (El Arrocito beach, July 4, 2007, intertidal algae, coll. B. Martínez et al.).

Description: based on male, 6.6 mm, UMAR-PERA-230.

Head: short, 1/4 shorter than the two first segments of pereon; anterior head lobe grossly subtruncate, inferior head lobe short and nearly straight. Eyes: grape shape, pigment dark brown, width representing approximately 1/4 the length of head. Antenna 1: 2/5 the length of the body, first article of peduncle approximately 1/5 longer than second article and width subequal, length of third article 2/5 the length of first article; accessory flagellum with one article. Antenna 2: 3/5 shorter than antenna 1, articles 4–5 the same length; first article of flagellum is 1/3 the length of the fifth article of peduncle.

Pereon: body length 3/5 longer than the antenna 1; dorsally smooth; color off-white in alcohol. Ventral margin of the coxae 2–4 with sparse long setae, formula for coxae 2–4: 4–3–1; coxae 5–6 with one and two short robust setae respectively. Gnathopod 1 with long simple setae external view, inner surface of propodus and carpus with numerous plumose setae; propodus 2/3 longer than the dactyl; propodus piriform, palm margin minutely denticulate, outer margin of palm with elongated simple setae and short robust setae, with inferior lateral short robust setae, and one robust seta at angle of the palm stronger and longer than the those of the palm margin. Gnathopod 2: longer piriform propodus, dactyl thin and elongated, propodus of gnathopod 2 approximately 1/3 longer than the dactyl; anterodistal margin of propodus with stridulation hump; oblique palm slightly convex with abundant and long plumose setae; palm margin with triangular setose hump near dactylar hinge, promptly a concave excavation with plumose setae, then mediofacial ridge-hump semi-hidden by setae. Pereopods 1–5: Merus and propodus of pereopod 1 the same length; basis of pereopod 2 1/2 longer than the merus; basis of pereopod 3 subquadrate; basis of pereopod 4 subrectangular; basis and merus of pereopod 4 the same length, posterodistal lobe of merus of pereopod 4 bicuspidate; basis of the pereopod 5 is semicircular, with posterodistal margin serrate; basis of the pereopod 5 1/2 wider than the merus; basis of the pereopods 3–5 without short simple setae.

Pleon: epimera shorter with respect to general line of the body; ventral margin bearing only some short robust setae, formula for epimera 1–3 is 1:0, 2:1–2–2, 3:1–1–2–2–1; epimeron 3 lightly convex on posterior edge, posteroventral angle irregularly denticulated. Uropod 3: peduncle is 1/3 shorter than the outer ramous; outer ramous is 1/5 longer and wider than the inner ramous; inner ramous bearing one proximally short robust seta and two medial short robust setae; outer margin of outer ramous with two cluster of medial robust setae and one proximal robust seta; mediodistal margin of peduncle with four short robust setae, outer angle of peduncle with three short robust setae and inner angle with two short robust setae. Telson deeply cleft, lobes approximately 1/5 longer than the width, lobes slightly excavated or nearly truncate, apices armed with one plumose seta and three robust setae, lateral longest robust seta and decreasing abruptly in length toward the inner short robust setae.

Female: based on female, 3.9 mm, UMAR-PERA-230. Gnathopod 1 like the male; but with shorter and scarce setae; outer angle of carpus without a long robust seta. Gnathopod 2 is like Gnathopod 1 for female; but with two short robust setae at inner angle of the palm. Coxa 1 widening gradually toward distal margin; anterodistal margin rounded and projected forward; coxa 2 suboblong, gradually narrow toward distal margin; coxa 3 subquadrate and anterodistally round; posterolateral margin of coxa 4 is emarginated, the emargination is 2/3 the total length posterolateral margin; ventral margin of the coxae 1–3 with long simple setae, the formula is 6–4–4; coxae 5–6 with short robust setae, the formula is 1–2; coxa 7 widening on posterior margin. Formula for epimera 1–3: 1:0, 2:1, 3:1–1–1. Posterodistal lobe of merus of pereopod 4 not bicuspidate.

Uropod 3 with inner margin of inner ramous bearing one medial short robust seta, outer margin of outer ramous with two cluster medial short robust setae; mediodistal margin of peduncle of uropod 3 with two short robust setae, distal angles of peduncle with two robust setae at each. Telson deeply cleft, apices armed with one plumose seta and two robust setae, longest lateral spine is 3/4 longer than the inner robust setae.

Taxonomic comments: the male from the Gulf of Tehuantepec presents some differences with E. tubar male from Cabo San Lucas, for details see Table 2 . The specimen revised by Barnard (1979) is possibly a preadult male, because of some characters described by Barnard (1979) such as the telson is similar to the female of Elasmopus tubar from the Gulf of Tehuantepec. Elasmopus tubar from the Gulf of Tehuantepec has an accessory flagellum with one article, while that from Cabo San Lucas is described with two articles. The formula of robust setae on ventral margin for the epimera 1–3 in E. tubar from the Gulf of Tehuantepec is 1:0, 2:1–2–2, 3:1–1–2–2–1, while that from Cabo San Lucas is 1:1–1–2, 2:1–1–1–1, 3:1–1–2–2–1–1. The posteroventral angle of epimeron 3 of E. tubar from the Cabo San Lucas has a very small tooth and sinus, while that from Gulf of Tehuantepec is irregularly denticulated. The posterior margin of epimeron 3 in E. tubar from Cabo San Lucas bears weak acclivities, each one with short simple setae, while that from Gulf of Tehuantepec has weak acclivities without simple setae. The distal margin of peduncle of uropod 3 in E. tubar from Cabo San Lucas has three medial short robust setae, while that from Gulf of Tehuantepec has four medial short robust setae. Elasmopus tubar from Cabo San Lucas has four short robust setae on outer angle of peduncle of uropod 3, while that from Gulf of Tehuantepec has only three. Telson of E. tubar from Cabo San Lucas has two robust setae and one simple apical seta, while the form of Gulf of Tehuantepec has three robust setae and one plumose apical seta. The lateral margins of each lobe of telson in E. tubar from the Cabo San Lucas have one plumose seta, while in the form of Gulf of Tehuantepec it is absent.

Remarks: Barnard (1979) described to E. tubar from Cabo San Lucas, and revised material from the Galapagos Islands did not include variations due to insufficient specimens.

Elasmopus zoanthidea Barnard, 1979: 79 , fig. 44.

Type locality: Tower Island, Galapagos Islands.

Distribution: Galapagos Islands.

Habitat: depth 0–4 m; rock wash, coral rock, intertidal algae, sediments from coral rock.

Material examined: 79 specimens: UMAR-PERA-245, 1 male (Estacahuite beach, September 10, 2005, coral rock 3–4 m, coll. R. Bastida et al.); UMAR-PERA-246, 12 males, 10 females, 3 juv (Estacahuite beach, August 25, 2006, coral rock 4 m, coll. R. Bastida et al.); UMAR-PERA-247, 3 females, 3 males (Estacahuite beach, July 3, 2007, intertidal coral rock, coll. J. Jarquín et al.); UMAR-PERA-248, 8 females (one specimen mounted), 8 males (one specimen mounted), 9 juv (La Entrega Bay, July 4, 2007, intertidal algae, coll. B. Martínez et al.); UMAR-PERA-249, 3 males, 9 females, 10 juv (El Arrocito beach, May 23, 2000, sediments from coral rock, coll. S. Salazar et al.).

Description: based on male, 5.2 mm, UMAR-PERA-248.

Head: the same size as the combined length of first two pereon segments; anterior head lobe grossly rounded, and inferior head lobe small and rounded. Eyes: rounded, pigment very dark; eyes represent approximately 1/3 of the length of head. Antenna 1: first article with five small spines on apical margin, 1/2 the length of the body, first article of peduncle is 1/8 longer than the second article and both are thicker, third article is 1/2 shorter than first article; accessory flagellum with two articles, both are the same length. Antenna 2: setose, approximately 1/2 of the length of the antenna 1; fourth article 1/5 longer than fifth article, fifth article approximately 2/3 longer than third article.

Pereon: body length is twice the length of the antenna 1; dorsally smooth; color off-white in alcohol. Coxae: anterior margin of the coxa 1 rounded and slightly produced; coxae 1 and 4 wider; coxa 2 narrows gradually toward distal margin; coxa 3 is the narrowest, with parallel margins; posterior margin of coxa 4 deeply emarginated; ventral margin of the coxae 1–4 with sparse long setae, formula for coxae 1–4 is 6–5–5– 1; coxae 5–6 with short robust setae, formula is 1–2; coxa 7 subovoid, with numerous short setae. Gnathopod 1: propodus subquadrangle; palm margin nearly straight with numerous robust setae; inner angle of the palm with one robust seta longer than those of palm margin, outer angle with simple long setae; inner surface of the palm and carpus with medium-sized plumose setae. Gnathopod 2: dactyl strong, propodus piriform, length of propodus approximately 1/3 longer than the dactyl; palm margin slightly oblique, nearly straight, moderately setose, with medium-sized plumose setae; palm margin with subrectangle setose hump near dactylar hinge, distal margin of this hump sinuous and apparently bilobed, then a subtrapezoid truncated tooth in the middle, this second tooth separated from setose hump by the same distance as the width of setose hump; palm defined by a small conate seta to receive dactyl; inner surface of palm with numerous bundles of plumose setae in rows paralleling palm and posterior margin. Pereopods 1–5: anterodistal angle of merus and carpus of pereopod 1 with a robust seta; basis of pereopod 2 approximately 1/2 longer than the merus; basis of pereopod 3 and pereopod 5 are 1/2 wider than the merus; basis of pereopod 4 nearly subquadrate and posterior margin nearly straight; pereopod 3 and pereopod 5 with wider basis, nearly semicircular, basis of pereopods 3–5 with posterior margin minutely serrate with short simple setae.

Pleon: epimera general line of the body is continuous; ventral margin bearing only a few short robust setae, formula for epimera 1–3 is 1: 0, 2: 0, 3: 1–1–2–2–1–1; epimeron 3 slightly straight on posterior edge, posteroventral corner emarginated bearing two weak denticles. Uropod 3: peduncle 1/5 shorter than outer ramous, inner ramous approximately 1/7 shorter than outer ramous, inner margin of the inner ramous bearing one proximal and two medial short robust setae, outer margin of the outer ramous with two clusters of medial short robust setae. Telson deeply cleft, lobes excavated, apices armed with three robust setae, decreasing in length toward inner robust setae, tip of smaller spines curved inwards.

Female: based on female, 4.7 mm, UMAR-PERA-248. Gnathopod 1 with suboval propodus, palm margin nearly convex, inner palm margin with numerous short robust setae and long plumose setae; inner angle of palm with one robust seta, its length is approximately 2/3 longer than those of palm margin; inner surface of palm with small plumose setae; inner surface of the carpus with long plumose setae, inner angle of carpus with three long robust setae. Propodus of gnathopod 2 nearly suboval with oblique palm margin, minutely denticulated, with short robust setae on inner and outer margin, inner angle with one robust seta more prominent, the length is 1/2 longer than the short robust setae of palm margin; inner surface of palm with two columns with numerous bundles of simple setae in rows paralleling palm; inner angle of carpus with two short robust setae. Formula for epimera 1–3 is 1: 1–1, 2: 2, 3: 1–1–2–1–1; posteroventral corner emarginated bearing one weak denticle. Inner margin of inner ramous of uropod 3 bearing two medial short robust setae, outer margin of outer ramous with three clusters of medial robust setae; mediodistal margin of peduncle with two short robust setae, inner and outer angle of peduncle with one and five robust setae respectively. Telson is similar to male, but with some differences, it is deeply cleft, approximately 3/4 the total length of lobe, apices armed with one simple seta, lateromedial margin of lobe with two simple setae.

Taxonomic comments: the specimens from the Gulf of Tehuantepec present some differences with the male specimen from the Galapagos Islands, for details see Table 3 . The specimen revised by Barnard (1979) is possibly a pre-adult male, due to some characters he described. The telson and epimera are similar with the female from the Gulf of Tehuantepec. Elasmopus zoanthidea from the Gulf of Tehuantepec has accessory flagellum with two articles, while that from Galapagos Islands is described with three articles. The distance between medial tooth and setose hump near dactylar hinge of gnathopod 2 in Elasmopus zoanthidea from the Galapagos Islands is equal to the width of the medial tooth, while that from Gulf of Tehuantepec it is equal to the width of the setose hump near dactylar hinge. The shape of medial tooth of gnathopod 2 in E. zoanthidea from Galapagos Islands is subquadrate, while that from Gulf of Tehuantepec it is subtrapezoid. The long simple setae on coxae 1–4 in E. zoanthidea from the Gulf of Tehuantepec is 6–5–5–1, while that from Galapagos Islands is 5–3–4–1. The formula of short robust setae on ventral margin for the epimera 1–3 in E. zoanthidea from the Gulf of Tehuantepec is 1: 0, 2: 0, 3: 1–1–2–2–1–1, while it is 1: 1, 2: 2–2, 3: 1–1–2–1–1 from Galapagos Islands. The uropod 3 with the outer margin of peduncle in E. zoanthidea from the Galapagos Islands has two setae, while that from Gulf of Tehuantepec without setae; inner angle of peduncle of uropod 3 of E. zoanthidea from the Galapagos Islands has three robust setae, while that from Gulf of Tehuantepec has two robust setae. The distal margin of telson in E. zoanthidea from the Galapagos Islands bears three robust setae and one simple seta, while that from Gulf of Tehuantepec only has three robust setae. The outer margin of each lobe in E. zoanthidea from the Galapagos Islands has two simple setae, while that from Gulf of Tehuantepec is bare.

Type material: 15 specimens: UMAR-PERA-253, holotype male (9.1 mm), paratype female (6.7 mm), paratypes: 1 male, 5 female, 2 males “gynomorphic”, 1 juv (Estacahuite beach, April 9, 2005 intertidal algae, coll. R. Bastida et al.); UMAR-PERA-251, paratypes: male (7.3 mm), female (5.5 mm) specimens mounted; 2 males (San Agustinillo beach, July 3, 2007, intertidal algae, coll. J. Jarquín et al.).

Additional material: 150 specimens: UMAR-PERA-250, 1 juv (entrance of Chacahua Lagoon, April 13, 2007, algae with barnacles, coll. S. García et al.); UMAR-PERA-252, 1 male, 2 females (Panteon beach, March 23, 2007, coral rock 3 m, coll. V. Mata); UMAR-PERA-254, 3 males, 2 females, 2 juv (Estacahuite beach, September 10, 2005, coral rock 2–4 m, coll. R. Bastida et al.); UMAR-PERA-255, 1 male, 2 juv (Estacahuite beach, September 10, 2005, intertidal calcareous algae, coll. R. Bastida et al.); UMAR-PERA- 256, 2 females, 4 juv (Estacahuite beach, September 10, 2005, sediments with shells 2–4 m, coll. R. Bastida et al.); UMAR-PERA-257, 1 male, 8 females, 7 juv (Estacahuite beach, December 1, 2006, coral rock 4 m, coll. R. Bastida et al.); UMAR-PERA-258, 1 male, 6 females (Estacahuite beach, July 3, 2007, intertidal coral rock, coll. J. Jarquín et al.); UMAR-PERA-259, 4 males, 10 females, 36 juv (La Tijera beach, April 30, 2005 sediments from coral rock 4 m, R. Bastida et al.); UMAR-PERA-260, 1 male, 2 females, 16 juv (La Tijera beach, September 12, 2006 coral rock 4 m, coll. R. Bastida et al.); UMAR-PERA-261, 1 male, 1 female, 1 juv (La Entrega Bay, July 4, 2007, intertidal algae, coll. B. Martínez et al.); UMAR-PERA-262, 2 females, 2 juv (El Arrocito beach, May 23, 2000, sediments from coral rock, coll. S. Salazar et al.); UMAR-PERA-263, 9 females, 11 males, 11 juv (El Arrocito, Oaxaca, July 4, 2007, intertidal algae, B. Martínez et al.).

Description: based on paratype male, 7.3 mm, UMAR-PERA-251, and holotype male, 9.1 mm, UMAR- PERA-253.

Head: similar in length to the first pereon segment; anterior head lobe slightly projected, inferior antennal sinus projecting in a lobe. Eyes: pear shape, pigment light brown; width represents approximately 2/5 the length of head. Antenna 1 2/5 the length of the body, first article of peduncle approximately 1/5 longer than the second article and considerably thicker, the length of third article is 2/5 the length of second article of peduncle. Accessory flagellum with two articles; length the same size as the first article of flagellum. Antenna 2 setose, approximately 3/4 the length of the antenna 1, the length of fourth article is slightly longer than the fifth article; first article of flagellum is 1/7 the length of the fifth article of peduncle.

Pereon: elongated body, length more 3/5 longer than the antenna 1, dorsally smooth; color off-white in alcohol. Coxae 1, 2 and 4 have subequal proportions; coxa 3 narrower; ventral margin of coxae 1–3 with sparse long setae, formula for coxae 1–3: 5–1–2. Anterior angle of coxa 1 projected forward; anterior margin of coxa 2 rounded and posterior margin oblique; lateral margins of coxa 3 straight and parallel; coxa 1 the same size as coxa 4, but anterior and posterior margin distinctly emarginated respectively; coxae 5–7 with short robust setae, formula for coxae 5–7: 2–2–1. Gnathopod 1 with subtrapezoid propodus; palm margin minutely denticulated with numerous short robust setae on margin; one robust seta at inner angle of the palm longer than the those on the palm margin, and the longest robust seta on outer angle; length of dactyl 1/2 shorter than the propodus. Gnathopod 2: length of propodus approximately 1/3 longer than the dactyl; palm slightly oblique and evenly convex, heavily setose, with medium size plumose setae; palm margin with two humps near dactylar hinge, the first ample, oval and truncated, and second ample, scalene and triangular; then in the middle a blunt tooth; far from apex of dactyl a mediofacial cuspidate seta is located, often transparent and difficult to see among dense simple setae. Pereopods 1–5 with margin of merus almost straight; pereopods 3–5 with wide basis, semicircular posterior margin and minutely serrate with very small simple setae.

Pleon: epimera wide with respect to general line of the body; epimeron 3 lightly concave on posterior edge, posteroventral corner ends in a prominent tooth, and ventral margin bearing short robust setae, the formula for epimera 1–3 is 1:2, 2:1–2–3–1, 3:1–2–3–3–2–2. Uropod 3 with peduncle approximately 1/3 shorter than the outer ramous, inner ramous approximately 1/8 less than the outer ramous, inner margin of the inner ramous bearing two clusters of short robust setae and one proximal short robust seta, external margin of outer ramous with three clusters of robust setae. Telson deeply cleft, with lobes deeply excavated, apices armed with three short robust setae that decrease in length in the inner robust setae.

Female: based on paratype female, 5.5 mm, UMAR-PERA-251, and paratype female, 6.7 mm, UMAR- PERA-253. Gnathopod 1 subquadrangular propodus, palm margin with robust setae; outer angle of palm with the longest robust seta. Propodus of gnathopod 2 suboval, palm margin not defined, but discernable by presence of two robust setae at angle of the palm, one external and a shorter internal one. Formula for epimera 1–3 is 1:2, 2:2–3–1, 3:1–1–2–2–1–1. Telson deeply cleft, with two long and two short robust setae interspersed, lateral margin of lobes with two plumose setae.

Etymology: this species is dedicated to Dr. Rolando Bastida Zavala for his remarkable commitment to the taxonomical and biological knowledge of marine benthos from Mexico principally on polychaete serpulids.

Taxonomic comments: more than any other species of Elasmopus from Eastern Pacific, Elasmopus bastidai n. sp. has distinctive gnathopod and apical spines of telson, in the terminal male and female.

Remarks: between examined materials, I found two gynomorphic specimens with developed oostegite, telson similar to female and gnathopod 2 similar to male.

Figures

FIGURE 3. Elasmopus tubar Barnard, 1979, male, 6.6 mm, UMAR-PERA- 230, Aguete, Oaxaca: A) habitus; B) accessory flagellum; C) antenna 1; D) antenna 2; E) gnathopod 2, external side; F) gnathopod 2, internal side; G) gnathopod 1, external side; H) gnathopod 1, internal side; I) epimera; J) uropod 1; K) uropod 2; L) uropod 3; M) telson.

FIGURE 4. Elasmopus tubar Barnard, 1979, male, 6.6 mm, UMAR-PERA- 230, Aguete, Oaxaca: A) palp; B) mandible; C) maxilliped; D) pereopod 1; E) pereopod 2; F) pereopod 3; G) pereopod 4; H) pereopod 5; I) upper lip; J) maxilla 1; K) maxilla 2. Female, 3.9 mm, UMAR-PERA- 230, Aguete, Oaxaca: L) lower lip; M) coxa 1; N) coxa 2; O) coxa 3; P) coxa 4; Q) coxa 5; R) coxa 6; S) coxa 7; T) telson; U) uropod 3; V) gnathopod 1, external side; W) gnathopod 1, internal side; X) epimera; Y) gnathopod 2, external side; Z) gnathopod 2, internal side.

Tables

TABLE 2. Comparison between males illustrated of Elasmopus tubar Barnard, 1979 from the Cabo San Lucas and from the Gulf of Tehuantepec.

Character/species	Cabo San Lucas	Gulf of Tehuantepec
Body length	5.1 mm	6.6 mm
Accessory flagellum	Two articles	One article
Spines on ventral margin of epimera 1–3	1:1–1–2, 2:1–1–1–1, 3:1–1–2–2–1–1	1:0, 2:1–2–2, 3:1–1–2–2–1
Posteroventral angle of epimeron 3	Spine and sinus very small	Irregularly denticulated
Posterior margin of epimeron 3	Bearing weak acclivities, each one with short simple seta	Weak acclivities without simple setae
Lateral margins of peduncle of uropod 3	Inner margin with setae, outer margin with two short robust setae	Bare
Number of spines on mediodistal margin of peduncle of uropod 3	Three short robust setae	Four short robust setae
Number of short robust setae on outer angle of peduncle of uropod 3	Four short robust setae	Three short robust setae
Number of apical setae on telson	Two robust setae and one simple seta	Three robust setae and one plumose seta
Outer margin of each lobe of telson	One plumose seta	Without setae
Elasmopus zoanthidea Barnard, 1979 (Figs 5, 6)

TABLE 3. Comparison between males illustrated of Elasmopus zoanthidea from the Galapagos Islands and specimens from the Gulf of Tehuantepec.

Character/ species	Galapagos Islands	Gulf of Tehuantepec
Body length Accessory flagellum	4.3 mm Three articles	5.2 mm Two articles
Distance between middle tooth and hump near dactylar hinge of gnathopod 2	Is e qua l to wid th of the middle tooth	Is equal to width of setose hump
Shape of middle tooth of gnathopod 2 Long simple setae on coxae 1–4	Subquadrate 5–3–4–1	Subtrapezoid 6–5–5–1
Short robust setae on epimera 1–3	1: 1, 2: 2–2, 3: 1–1–2–1–1	1: 0, 2: 0, 3: 1–1–2–2–1–1
Uropod 3: outer margin of peduncle Inner angle of peduncle of uropod 3	With 2 simple setae Three short robust setae	Without simple setae Two short robust setae
Telson: distal margin	One simple seta	Without simple setae
Telson: outer margin of each lobe	Two simple setae	Without simple setae
Elasmopus bastidai n. sp. (Figs 7, 8)