Quadrimaera rocasensis, Senna, André R. & Serejo, Cristiana S., 2007

Senna, André R. & Serejo, Cristiana S., 2007, Two new species of Quadrimaera (Crustacea: Amphipoda: Melitidae) from Atol das Rocas, Brazil, Zootaxa 1593, pp. 55-67 : 61-64

Quadrimaera rocasensis sp. nov.

( Figures 5–7 )

Type material. Holotype: MNRJ 19590, male, 6.3 mm, Atol das Rocas, intertidal puddle in front of Farol Velho, from washed algae, F. B. Pitombo & R. Barroso coll., December 21, 2000.

Paratypes: MNRJ 19591, 10 specimens, Atol das Rocas, intertidal puddle in front of Farol Velho, F. B. Pitombo & R. Barroso coll., December 21, 2000; MNRJ 19592, 1 specimen, off Cemitẻrio Island, P. S. Young, P. C. Paiva & A. A. Aguiar coll., October 23, 2000; MNRJ 19593, 5 specimens, Atol das Rocas, Cemitẻrio Island, F. B. Pitombo & R. Barroso coll., December 30, 2000; MNRJ 19594, 3 specimens, Atol das Rocas, intertidal puddle near Barretão, P. S. Young, P. C. Paiva & A. A. Aguiar coll., October 27, 2000; MNRJ 19595, 1 specimen, Atol das Rocas, Fendas, P. S. Young, P. C. Paiva & A. A. Aguiar coll., October 11, 2000; MNRJ 19596, 2 specimens, Atol das Rocas, bay west of Barretão, P. S. Young, P. C. Paiva & A. A. Aguiar coll., October 16, 2000; MNRJ 19597, 7 specimens, Atol das Rocas, Barretão, P. S. Young, P. C. Paiva & A. A. Aguiar coll., October 19, 2000; MNRJ 19598, 2 specimens, Atol das Rocas, Salão, P. S. Young, P. C. Paiva & A. A. Aguiar coll., October 13, 2000.

Diagnosis. Gnathopod 2, palm transverse with two proximal U-shaped concavities and another elliptical concavity before palmar corner, proximal U-shaped concavity deeper than next one; dactylus, inner margin with a robust spine opposite the proximal palmar concavity; pereopods 5–7, basis with posterodistal lobe not much produced; epimeral plate 3 with two small spines postero-distally; telson cleft 80 percent of its length, lobes distally notched with three long bifid setae, a small bifid seta and a nail with a small apical seta; outer margin with three slender setae.

Description. Holotype, male, 6.3 mm. Head without rostrum, eyes small. Antenna 1, ratio of articles of peduncle = 1.0:1.08:0.27, article 1 with one long distal seta and a tuft of minute setae; accessory flagellum 8- articulate. Antenna 2, first article of peduncle fused to head. Lateral cephalic lobe truncate. Left mandible, incisor with five robust spines; setal row with seven acute curved stout setae; molar cylindrical, triturative and minutely setose; palp 3-articulate, ratio of articles = 1.0:0.95:1.43, article 2 with six slender setae on inner margin, article 3 with seven slender setae on inner margin and a long slender seta on apical margin. Right mandible, incisor with four robust spines, lacinia mobilis with a row of minute spines on apical margin, setal row with six acute and curved stout setae, molar short, cylindrical, triturative and minutely setose; palp 3- articulate, ratio of the articles = 1.0:0.76:1.12, article 2 with five slender setae on inner margin, article 3 with five slender setae on inner margin and two long slender setae on apical margin. Maxilla 1, distal inner plate with two minute setae and two slender setae, inner margin with three minute setae and outer margin with four minute setae; outer plate with seven bifid stout setae; palp 2-articulate with a slender seta on article 1 outer margin and ten distal slender setae. Maxilla 2, inner plate with inner and distal margins setose; outer plate distally setose. Maxilliped, inner plate quadrate with seven plumose slender setae distally, inner margin with a plumose slender seta distally; outer plate semi-oval, inner margin with nine stout setae, apical margin with three stout setae and two long slender setae; palp 4-articulate, article 3 with 11 slender setae, article 4 with three slender setae and an apical nail. Lower lip, inner margin of lateral lobes and distal margin of lateral and medial lobes minutely setose.

Coxa 1 subquadrate with ten slender setae, anterodistally produced. Gnathopod 1, basis naked, longer than ischium and merus combined; ischium, posterior margin with four slender setae; merus, posterior margin distally setose; carpus, posterior margin densely setose and lateral surface with tufts of setae; propodus oval, slightly longer than carpus, palm oblique and setose, slightly longer than posterior margin, defined by a small spine which separates it from the margin; dactylus with six small slender setae on posterior margin. Coxa 2 subquadrate with five slender setae anteriorly. Gnathopod 2 much longer and more robust than gnathopod 1, basis longer than ischium and merus combined, anterior margin setose, posterior margin with two long slender setae; carpus reduced, triangular; propodus robust, subrectangular, longer than broad, distally broadened, posterior margin setose; palm transverse, setose, with two U-shaped concavities, more proximal one larger than the other, and with one distal U-shaped concavity before palmar corner; palmar corner produced into a large acute spine; dactylus robust, anterior margin with a single slender seta, posterior margin with eight small slen- der setae and a robust spine opposite the proximal concavity of the palm of propodus. Pereopod 3 basis thin, slightly shorter than ischium, merus and carpus combined; carpus and propodus with posterior margin setose; dactylus bearing two slender setae and a bifid nail. Pereopod 4 subequal to pereopod 3, with dactylus bearing three slender setae and a bifid nail. Pereopod 5, basis narrow ovato-rectangular, posterior margin with small slender setae; merus, anterior margin with setal tufts, posterior margin with a distal setal tuft; carpus with a posterodistal setal tuft; propodus, anterior margin setose, posterior margin with a distal setal tuft; dactylus with a small anterior hump and an apical bifid nail. Pereopods 6–7 more robust than pereopod 5, merus with setal tufts on anterior and posterior margins; carpus with setal tufts anterodistally and posterodistally; propodus with a posterodistal setal tuft; dactylus bearing an apical bifid nail.

Epimeral plate 3 with seven slender setae on ventral margin and two small spines posteriorly. Uropod 1, peduncle lengthened, with four dorsal setae, five setae on lateral surface, ventral margin with a proximal seta and two distal setae; rami distally truncate and setose. Uropod 2, peduncle shorter than rami; inner ramus longer than outer ramus; rami dorsally and distally setose, distally oblique. Uropod 3, peduncle slightly shorter than rami; inner ramus slightly shorter than outer ramus; outer ramus with bifid stout setae on ventral and distal margins; rami distally truncate. Telson nearly as long as wide, cleft at 80 percent of its length, lobes distally notched with three long bifid setae, a small bifid seta and a nail with a small apical seta, outer margin with three slender setae.

Remarks. Quadrimaera rocasensis sp. nov. is close to Q. cristianae and Q. pacifica in having the palm of gnathopod 2 delimited by a strong acute spine, preceded by a deep excavation. Maxilla 1 of Q. rocasensis sp. nov. is also similar to maxilla 1 of these species. However, Q. rocasensis sp. nov. can be distinguished from them by the pattern of the U-shaped concavities on the palm of gnathopod 2, by the presence of a robust spine on the dactylus of gnathopod 2 opposite the proximal concavity on the palm, by the bifid posterodistal corner of epimeral plate 3, and by the nail with a small apical seta on each lobe of the telson.

Figures

FIGURE 5. Quadrimaera rocasensis sp. nov., holotype, male, MNRJ 19590. Scale for Ll represents 0.1 mm, remainder represent 0.05 mm.

FIGURE 6. Quadrimaera rocasensis sp. nov., holotype, male, MNRJ 19590. Scales represent 0.1 mm.

FIGURE 7. Quadrimaera rocasensis sp. nov., holotype, male, MNRJ 19590. Scales for P 3 – 7 represent 0.1 mm, remain- der represent 0.05 mm.