Melita bousfieldi, 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 : 44-49

Melita bousfieldi n. sp.

( Figs 23 , 24 )

Type material: UMAR-PERA-319, holotype male (6.4 mm), paratype female (4.3 mm), specimens mounted (Estacahuite beach, September 10, 2005, sediments with shells 2–4 m, coll. R. Bastida et al.).

Additional material: 89 specimens: UMAR-PERA-316, 2 females (Panteon beach, March 23, 2007, coral rock 3 m, coll. V. Mata); UMAR-PERA-317, 1 female, 1 male (Estacahuite beach, April 9, 2005 intertidal algae, coll. R. Bastida et al.); UMAR-PERA-318, 1 male (Estacahuite beach, April 9, 2005, coral rocks 2–4 m, coll. R. Bastida et al.); UMAR-PERA-320, 2 males, 7 female, 9 juv (Estacahuite beach, December 1, 2006, sediments of coral rock 4 m, coll. R. Bastida et al.); UMAR-PERA-321, 2 males, 2 females, 1 juv (La Tijera beach, April 30, 2005, sediments from coral rock 4 m, coll. R. Bastida et al.); UMAR-PERA-322, 1 female (La Tijera beach, September 12, 2006, coral rock 4 m, coll. R. Bastida et al.); UMAR-PERA-323, 3 females, 2 juv (Riscalillo Bay, Oaxaca, June 16, 2004, algae on coral 1–2 m, coll. S. García); UMAR-PERA-324, 25 males, 22 females, 9 juv (El Arrocito beach, May 23, 2000, sediments from coral rock, coll. S. Salazar et al.).

Description: based on holotype male, 6.4 mm, UMAR-PERA-319.

Head: medium, length slightly shorter than two pereon segments; rostrum small, anterior head lobe ample, rounded, and strongly projected, partially covering the first segments of antenna 2; the inferior antennal sinus a short incision with straight margin. Eyes subtriangle, pigment light brown; width approximately 1/3 the length of head. Antenna 1: length of antenna 1 less than 2/3 the body length; ventral surface of first article of peduncle with three short robust setae; first article of peduncle 1/4 shorter than second article and considerably thicker; length of third article 1/3 the length of second article of peduncle. Length of article 2 of antenna 1 is 1/7 longer than the article 4 of antenna 2. Accessory flagellum with three articles, third article the smallest. Antenna 2 elongated, approximately 1/10 shorter than antenna 1, length of fifth article 4/5 the length of fourth article; first article of flagellum 1/3 the length of the fifth article of peduncle.

Pereon: body elongate and slender, length 1/3 longer than the length of antenna 1; pereon dorsally smooth; color gray to beige in alcohol. Coxa 1 broadened distally; coxae 1, 3 subtrapezoid, both with margins nearly straight; coxa 2 suboval, posterior margin of coxa 4 slightly emarginated, length emarginated more than 2/3 the total length; coxa 7 subtriangle; ventral margin coxae 1–6 with short setae, and scarce mediumsized setae. Distal margin of propodus of gnathopod 1 sinuous, with three cusps: the first medial, rounded, and smooth cusp, the other two cusps on the same sides as previous; second cusp is the dactyl, semideveloped, sharp and immovable; and the third cusp is a prominent angle of palm with numerous short simple setae and three short robust setae on inner surface; length of propodus 1/4 shorter than carpus, carpus widens gradually toward distal margin. Gnathopod 2: propodus suboval, length of propodus approximately 1/2 longer than width, palm margin of gnathopod 2 undefined; the length of dactyl more than 1/2 longer than the propodus; inner surface of palm deeply setose throughout, with submarginal short pappose setae, long plumose setae and simple setae on palm margin. Pereopod 1 longer than pereopod 2, basis of the pereopods 1–2 with short robust setae and long simple setae, pereopod 2 with merus shorter than propodus; pereopods 3–5 with basis produced posterior-distally, anterior margin of basis with short robust setae and posterior margin with short simple setae; carpus approximately 1/2 shorter than propodus.

Pleon: margin dorsolateral of pleon with small spines on each side with intercalated short simple seta, formula for dorsolateral margin is 1:7, 2:19, 3:15. Urosomal segment 1 with one mediodorsal acute spine, segment 2 with one pair of dorsolateral spines on each side, each pair enclosing one simple seta. Epimera: posterior edges convex, posteroventral corner ends in a acute spine, lower margin broadly convex; characters are stronger in epimeron 3; submarginal surface of epimera bearing short robust setae, formula for epimera is 1:0, 2:1–1–1,1 3:1–1–1–1–1; ventral margin of epimera 2, 3 with two and five smaller spines respectively, each spine with a shorter simple seta attached. Uropod 3: length of peduncle 1/2 shorter than outer ramous; length of outer ramous is 9/10 longer than inner ramous, five clusters of robust setae on both margins of outer ramous; two robust setae on distal margins and one smaller robust seta on subdistal surface of inner ramous; four short robust setae on basal margin of inner ramous. Telson cleft, 2/3 length of the lobes, apices with two plumose setae, two simple setae and four robust setae, two long and two medium size; outer margins of lobe with two short robust setae and inner margin of lobe with one robust seta; longest distal spine of telson 1/4 shorter than the length of lobe.

Female: based on paratype female, 4.3 mm, UMAR-PERA-319. Length of carpus and propodus of gnathopod 1 the same length; propodus suboval, widening gradually toward distal margin; transverse palm margin, slightly convex and with short robust setae. Gnathopod 2 with suboval propodus, the length of propodus 1/3 longer than carpus, palm oblique and slightly convex, palm margin with short robust setae, and on inner angle two submarginal robust setae of different size; dactyl curved, fitting palm; carpus, propodus and dactyl with long setae. Distal margin of anterior lobe of coxa 6 with three slight cusps, and continues below in a peculiar process, partially contorted, having a large medial lobe. Formula for dorsolateral margin of pleonites is 1:0, 2:5, 3:7; submarginal surface of epimera bearing robust setae, formula for epimera 1–3 is 1:0, 2:1–1, 3:1–1; ventral margin of the epimera 1–3 with one, two and four short spines respectively, each spine with a short simple seta attached. Telson cleft, 9/10 the length of the lobes, apices with two plumose setae, one simple seta and three-four robust setae, one long, one medium sized and one small; outer and inner margins of lobe bare; longest distal spine of telson subequal or 1/5 shorter than the length lobe.

Etymology: the specific name is dedicated to a great specialist in the group, PhD. Ed Bousfield (retired from Royal Ontario Museum, Toronto), for his remarkable dedication to the taxonomical and biological knowledge of the Amphipods of Northeastern Pacific region.

Taxonomic comments: Melita bousfieldi n. sp. presents characters similar to other species of genus; the most important characters are compared between males of Melita from the Tropical Eastern Pacific (see Table 7 ). Melita nitida Smith, 1873 was described from the coast of New England; however, the morphotype of M. nitida used for this comparison in the Table 7 was recorded by Shoemaker (1935) from Mazatlan, Sinaloa; it is used here because it is the only record of this species from the Tropical Eastern Pacific. The ventral surface of article 1 of the antenna 1 in Melita nitida from Mazatlan has two short robust setae, in Melita sulca Stout, 1913 five short robust setae, while Melita bousfieldi n. sp. has three short robust setae. The length of article 2 of the antenna 1 in Melita sulca is 1/10 longer than length of article 4 of antenna 2, while Melita bousfieldi n. sp. is 1/7 longer than length of the article 4 of the antenna 2. The angle of palm of the gnathopod 1 in Melita nitida is dissipated, with some simple setae and three short robust setae, in Melita sulca it is truncated, with simple setae, and in Melita bousfieldi n. sp. it is triangular and projected, with abundant simple setae and three short robust setae. The dactyl of gnathopod 1 in Melita nitida is movable and developed to fit the palm, in Melita sulca it is immovable, rudimentary and truncated; in Melita bousfieldi n. sp. it is semideveloped, immovable and sharp. The palm margin of gnathopod 2 in Melita nitida is defined, with a double margin with short robust setae, in Melita sulca it is undefined and in Melita bousfieldi n. sp. it is undefined, without short robust setae. Dorsolateral surface of the pleon of both Melita sulca and Melita nitida is bare, while Melita bousfieldi n. sp. has spines with intercalated simple setae; the formula is 1:7, 2:19, 3:15. Dorsolateral surface of the urosoma of Melita nitida has bare first segment, and second segment has three-four simple setae; in Melita sulca the first segment has one dorsal spine, second segment has two spines of unequal length; in Melita bousfieldi n. sp. the first segment has one dorsal spine; second segment has two spines of the same length. Basal margin of inner ramous of the uropod 3 has two robust setae in Melita sulca while Melita bousfieldi n. sp. has four robust setae. Distal margin of telson in Melita nitida has two to three apical short robust setae, in Melita sulca with three to four apical robust setae and one simple seta; Melita bousfieldi n. sp. has four apical robust setae, two plumose and two simple setae. Length of the longest apical robust seta of telson in Melita bousfieldi n. sp. is longer than total length of lobe with respect to the relation observed between Melita sulca and Melita nitida .

Remarks: Chapman (1988) discusses that the record of Shoemaker for Mazatlan represents an undescribed species of Melita . On the other hand Melita lignophila Barnard, 1961 from Tropical Eastern Pacific is not included, because according to Jarrett & Bousfield (1996) its generic status is uncertain, due to several characters, principally mouthparts, which have not been described nor illustrated. They suggest that it is a probable member of genus Megamoera but the dorsal abdominal dentition is unlike that of others species of this genus.

Figures

FIGURE 23. Melita bousfieldi n. sp., holotype, male, 6.4 mm, UMAR-PERA- 319, Estacahuite beach, 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) upper lip; J) details of the point gnathopod 1, internal side; K) gnathopod 1, internal side; L) gnathopod 2, internal side; M) accessory flagellum; N) antenna 1; O) antenna 2; P) lower lip.

FIGURE 24. Melita bousfieldi n. sp., holotype, male, 6.4 mm, UMAR-PERA- 319, Estacahuite beach, Oaxaca: A) maxilla 1; B) maxilliped; C) telson; D) pereopod 1; E) pereopod 2; F) pereopod 3; G) pereopod 4; H) pereopod 5; I) uropod 1; J) uropod 2; K) uropod 3; L) palp of mandible; M) right mandible; N) maxilla 2; O) epimera. Paratype, female, 4.3 mm, UMAR-PERA- 319, Estacahuite beach, Oaxaca: P) telson; Q) left coxa 6; R) gnathopod 1, external side; S) gnathopod 1, internal side; T) gnathopod 2, external side; U) gnathopod 2, internal side.

Tables

TABLE 7. Comparison between males of Melita from the Tropical Eastern Pacific.

Character/ species	M. sulca	M. nitida Mazatlán	M. bousfieldi n. sp.
Body length	12 mm	6 mm	6.4 mm
Number of short robust setae on ventral surface of article 1 of antenna 1	Five short robust setae	Two short robust setae	Three short robust setae
Relation of the length article 2 of antenna 1 / article 4 of antenna 2	Scarcely 1/10 longer than length of article 4	More than of 1/10 shorter than length of article 4	1/7 longer than length of article 4
Angle of palm of the gnathopod 1	Truncated, with simple setae	Dissipated, with simple setae and three short robust setae	Triangular and projected, with abundant simple setae and three short robust setae
Dactyl of gnathopod 1	Rudimentary, immovable and truncated	Movable and developed to fit the palm	Semideveloped, immovable and sharp
Palm margin of gnathopod 2	Undefined	Defined, with a double margin with short robust setae	Undefined
Number of robust setae on basal margin of inner ramous of the uropod 3	Two robust setae	One robust seta	Four robust setae
Dorsolateral surface of the pleon	Bare	Bare	With spines and simple setae intercalated, 1:7, 2:19, 3:15
Dorsolateral surface of the urosome	First segment with one dorsal spine; second segment with two spines of unequal length	First segment bare; second segment with 3–4 simple setae	First segment with one dorsal spine; second segment with two spines of same length
Telson	3–4 apical robust setae and one simple seta	2–3 apical robust setae	Four apical robust setae, two plumose and two simple setae
Relation of length of longest apical robust setae / lobe of telson	1/2 shorter than lobe	2/3 shorter than lobe	1/4 shorter than lobe