Lysianassa danai, Senna, André R. & Serejo, Cristiana S., 2008

Senna, André R. & Serejo, Cristiana S., 2008, Amaryllididae and Lysianassidae (Amphipoda: Lysianassoidea) from off the central coast of Brazil (11 ºS – 22 ºS), with descriptions of three new species, Zootaxa 1718, pp. 45-68 : 56-60

Lysianassa danai sp. nov.

( Figures 7–9 )

Type material. Holotype: REVIZEE Benthos Program, Central SCORE, N/R Astro Garoupa col.: male, 5.8 mm, 16º47'10"S – 37º41'10"W, 50 m, June 30, 2001, MNRJ 18535.

Diagnosis. Antenna 1, article 1 of peduncle without medial tooth. Antenna 2 of male elongate, one third of the body length; peduncle geniculate between articles 4 and 5. Left mandible, lacinia mobilis modified in a small robust seta; palp article 2, length 5X the width, with four distal slender setae, article 3 thin, curved, minutely setose and with three slender setae in the apical margin. Maxilla 1, palp 2-articulate, distal margin strongly serrate, with a robust spine on the inner corner. Gnathopod 1, propodus with a projection and a stout seta proximal to the posterodistal corner; dactylus simple, nail present, weakly defined. Gnathopod 2, palm slightly obtuse, serrate, with a small stout seta proximal to the posteroventral corner; dactylus simple, not reaching the palmar corner. Pereopod 6, basis with posterior margin slightly concave. Uropod 3, peduncle elongate, length 2X the width, rami lanceolate; outer ramus 1-articulate, 1.3X the inner ramus length. Telson entire and distally truncate.

Description. Holotype, male, 5.8 mm, body dorsally flat and without setae. Antenna 1, peduncle article 1 with four small and plumose ventral setae, one ventrodistal plumose seta and one plumose seta on the distal margin; primary flagellum 6-articulate; accessory flagellum 3-articulate. Antenna 2 elongate, one third the body length; peduncle geniculate between articles 4 and 5; flagellum without setae. Epistome and upper lip separate, epistome concave, upper lip more produced than epistome, rounded, anteroventral margin with an acute projection. Left mandible, incisor smooth, distal margin convex; lacinia mobilis modified as a small robust seta; accessory row with 3 setae; molar setose; palp 3-articulate, article 1 small, without setae, article 2 elongate, length 5X the width, with four thin distal setae, article 3 thin, curved, minutely setose, with three thin setae on the distal margin. Maxilla 1, outer plate, ST1 1-cuspidate, ST2–3 2- cuspidate, ST4 3- cuspidate, ST5 5- cuspidate, ST6 10- cuspidate, ST7 7- cuspidate and STA-D apically bifid; palp 2-articulate, distal margin strongly serrate, with one robust spine on the inner corner. Maxilla 2, outer plate narrow; inner plate approximately 2X broader than outer plate. Maxilliped, inner plate subquadrate, inner margin setose, apical margin with three nodular setae; outer plate suboval, inner margin setose, submarginal setae present, apical setae absent; palp 4-articulate, inner margin setose, article 3, inner margin setose, apicolateral margin with a tuft of setae, dactylus well developed, subterminal spine present.

Gnathopod 1 simple; coxa well developed, not hidden by coxa 2, anterior margin straight, anteroventral margin rounded, without lobe, posterior margin slightly convex, with a small posteroventral notch; basis, length 2.5X the width, with two slender setae on the posteroventral corner; ischium, posterior margin with four slender setae; merus subtriangular, posterodistally projected, with a tuft of slender setae on the posterodistal corner; carpus and propodus subequal in length; propodus tapering distally, with a tuft of long slender setae on the anterodistal corner, posterior margin with four small and robust setae, with a projection and a robust seta proximal to the posterodistal corner; dactylus simple, nail present, weakly marked. Gnathopod 2, coxa large, anterior margin slightly convex, posterior margin straight, with a small posteroventral notch; basis elongated, length 6.5X the width, posteriorly curved; ischium elongate, length 2.7X the width; merus with a tuft of setae on the posterodistal margin; carpus posteriorly expanded, length 1.7X of the propodus length; propodus slightly expanded distally, with ten lateral slender setae, three distal slender setae, posterior margin setose, covered by small robust setae proximal to the posteroventral corner, palm slightly obtuse, serrate, with a small spine proximal to the posteroventral corner; dactylus simple, not reaching the palmar corner. Pereopod 3, coxa well developed, as large as the coxa 2, anterior margin convex, posterior margin concave, ventral margin rounded; merus anterodistally produced, posterior margin setose. Pereopod 4, coxa well developed, anterior margin convex, posteroventral lobe present; merus anterodistally produced; carpus and propodus, posterior margin setose; propodus larger than carpus; dactylus simple, elongate. Pereopod 5, coxa slightly posterolobate. Pereopod 6, coxa, anterior margin slightly concave, posterior margin rounded; basis, anterior margin rounded, posterior margin slightly concave, posteroventral lobe well developed; merus posterodistally produced. Pereopod 7, coxa, anteroventral margin concave; basis, posterior margin rounded, slightly serrate, posteroventral lobe present.

Pleonites 1–3 and urosomites 1–3 dorsally flat. Epimeral plate 3 with posteroventral corner rounded. Uropod 1, peduncle elongate, length 5X the width, with seven dorsal setae and nine lateral setae; rami subequal in length. Uropod 2, peduncle subequal in length to the rami; outer ramus with three dorsal setae; inner ramus with a notch and one long and thin dorsal seta, nail present. Uropod 3, peduncle elongate, length 2X the width, rami lanceolate; outer ramus 1-articulate, 1.3X the inner ramus length. Telson entire, lateral margin with a plumose seta, distal margin truncate and with two pairs of small slender setae.

Remarks. Lysianassa danai sp. nov. is very similar to Lysianassa costae Milne Edwards, 1830 , in the geniculated antenna 2, mandible with incisor smooth, molar small and setose, palp article 3 curved and minutely setose, outer plate of maxilla 2 narrow, STA-D of maxilla 1 distally bifid, plumose setae on the ventral margin of the article 1 of antenna 1, dactylus of gnathopod 1 with nail weakly marked, and epimeral plate 3 with posteroventral corner rounded. Lysianassa danai sp. nov. has the uropod 3 without plumose setae. However, L. danai sp. nov. can be distinguished from L. costae by presenting coxa 1 anteriorly produced and smaller than the coxa 2; and the lacinia mobilis present. In L. costae , antenna 2 in males is as long as the body length. Males of L. danai sp. nov. have antenna 2 reaching one third of the body length. Lysianassa brasiliensis , described from Rio de Janeiro by Dana (1853), also presents antenna 2 extremely elongate, with its apex hiding among the epimeral plates. However, L. danai sp. nov. and L. brasiliensis can be differentiated by the relationship between the lengths of antenna 2 and body, besides the shape of the posterior margin of the basis of pereopod 6, which is slightly concave in L. danai sp. nov. and convex in L. brasiliensis .

Lysianassa costae presents a small medial tooth on the article 1 of peduncle of antenna 1, what differentiates it of L. ceratina , that presents the same medial tooth enlarged. Lysianassa danai sp. nov. does not present that tooth on the article 1 of peduncle of antenna 1. The type material of L. brasiliensis is apparently lost and its description and illustrations were not very detailed, what makes the identification difficult.

Distribution. Lysianassa danai sp. nov. was collected in a single station at southern Bahia State, at 50 m depth.

Etymology. The name danai is given in honor of James D. Dana, for his very important contribution to knowledge of amphipods in the 19th Century, including on the Brazilian coast.

Figures

FIGURE 7. Lysianassa danai sp. nov., male 5.8 mm, 16 º 47 ’ 10 ” S – 37 º 41 ’ 10 ” W, 50 m, June 30, 2001, MNRJ 18535. Scale bars: 1.0 mm for habitus; 0.1 mm for the remainder.

FIGURE 8. Lysianassa danai sp. nov., male 5.8 mm, 16 º 47 ’ 10 ” S – 37 º 41 ’ 10 ” W, 50 m, June 30, 2001, MNRJ 18535. Scale bars: 0.1 mm.

FIGURE 9. Lysianassa danai sp. nov., male 5.8 mm, 16 º 47 ’ 10 ” S – 37 º 41 ’ 10 ” W, 50 m, June 30, 2001, MNRJ 18535. Scale bars: 0.1 mm.