Alexandrella setosa, Serejo, C. S., 2014

Serejo, C. S., 2014, A new species of Stilipedidae (Amphipoda: Senticaudata) from the South Mid- Atlantic Ridge, Zootaxa 3852 (1), pp. 133-140 : 135-137

Alexandrella setosa sp. nov.

( Figs 2–5 )

Material examined. Holotype, male, 17.9 mm, superstation 7, serial number 1030, Walvis Ridge Sector (WRS), 29o29.87’S 0 1o 10.06’E, 4120 m, MNRJ 23520. Allotype, female, 18 mm, same as type locality, MNRJ 23763. Paratypes: 2 females, 19 mm, 19.3 mm, same as type locality, MNRJ 23764.

Etymology. from the Greek Setose that corresponds to the densely setose condition of gnathopods 1 and 2.

Diagnosis. Mandible, incisors fully toothed, molar absent; maxilla 1 outer plate with 36–40 setal-teeth. Gnathopods 1–2 subchelate, carpus and propodus densely setose. Pleonites 1–3 and urosomite 1 strongly toothed.

Description. Based on holotype, male 17.9 mm, MNRJ 23520. Eyes absent. Upper lip strongly asymmetrical. Mandible, incisor fully toothed; molar absent; left lacinia mobilis very large and toothed; right lacinia much smaller than left one, slightly toothed palp 3-articulated. Lower lip without inner lobe. Maxilla 1, palp 2- articulated, second article widening distally, with 28–30 distal robust setae and 9–10 sub distal slender setae; outer plate with 36–40 setal teeth; inner plate setose, with 5–6 basal pappose setae. Maxilla 2 outer plate slightly wider than inner plate; inner plate with several basal pappose setae. Maxilliped outer plate strongly exceeding palp, serrate medially; inner plate extending past distal margin of palp article 1; palp with marginal setae.

Coxa 1 wider than coxae 2–3. Coxa 4 excavated posteriorly, ventral margin rounded. Gnathopods 1–2 subchelate, palm excavate proximally, broadly rounded distally, with 10–11 robust setae at palm corner; propodus and carpus densely setose; dactylus slightly curved, inner margin with sparse setae. Basis of pereopods 5–6 with medial ridge. Basis of pereopod 7 expanded proximally forming a posterior lobe, posterodistal lobe rounded.

Pleonites 1–3 and urosomite 1 strongly toothed. Epimeron 2 with posteroventral tooth. Epimeron 3 subquadrate. Uropod 1, peduncle apparently longer than rami, which are broken at tip. Uropod 2 peduncle subequal to inner ramus; inner ramus 1.6 × outer ramus length; both rami with marginal row of setae on medial side. Uropod 3 peduncle much shorter than rami, which are broken at tip. Telson emarginated, as long as wide.

Female. Gnathopods 1–2 subchelate, palm slightly oblique, with 3 robust setae; propodus and carpus densely setose; dactylus straight and distinctly serrate. Oostegites present on pereopods 2–5.

Distribution. Atlantic Ocean: Walvis Ridge, 29o29.87’S 0 1o 10.06’E, 4120 m.

Remarks. Alexandrella setosa sp. nov is closely related to A. subchelata as both species present gnathopods 1–2 subchelate, which is a unique character within the genus. The new species can be distinguished from A. subchelata by the maxilla 1 outer plate with 36–40 setal teeth (versus 26 setal-teeth); maxilla 1 palp with 28–30 robust setae (versus 16 robust setae); gnathopods 1–2 densely setose on facial margins of carpus and propodus and pleonites 1–3 dorsally with well developed pointed teeth.

Figures

FIGURE 2. Alexandrella setosa sp. nov., allotype, female, 18 mm, MNRJ 23763.

FIGURE 3. Alexandrella setosa sp. nov., allotype, female, 18 mm, MNRJ 23763. Buccal pieces, holotype, male, 17.9 mm, MNRJ 23520. Scale bar, 0.5 cm.

FIGURE 4. Alexandrella setosa sp. nov., holotype, male, 17.9 mm, MNRJ 23520. Allotype, female, 18 mm, G 1 – 2, MNRJ 23763.

FIGURE 5. Alexandrella setosa sp. nov., holotype, male, 17.9 mm, MNRJ 23520.