Pseudopleonexes evensis, Peart, Rachael A. & Loerz, Anne-Nina, 2018

Peart, Rachael A. & Loerz, Anne-Nina, 2018, Ampithoidae (Crustacea, Amphipoda) from New Zealand, ZooKeys 733, pp. 25-48 : 31-36

Pseudopleonexes evensis sp. n. Figs 5, 6, 7

Ampithoe (Pleonexes) lessoniae .- Barnard 1972: 44, figs 13-14.

Type material.

Holotype, 9 mm, male, NIWA 121291, from algal washings, 0. 5 m, Eve Bay, Wellington, New Zealand, 41°19'58"S, 174°49'39"E, coll. R. Peart and J. Peart, 29 Nov 2016.

Paratype, female, 7 mm, NIWA 121292. Paratypes, female and male, ZMH K-46614, Same collection data as the holotype.

Other material examined.

6 specimens, male, female and juveniles, NIWA 121894, same collection data as the holotype. Male, 1 specimen, NIWA 7024, E797, from intertidal algal washings, 0.5 m, Huaroa Pt, Whangaparaoa, New Zealand, 36°35.7'S 175°50.14'E, coll J. L. Barnard, 16 Feb 1968.

Diagnosis.

Male: eye prominent. Antennae damaged in type material (Barnard, 1972 material antenna 1 longer than antenna 2). Epistome and upper lip, in situ, directed posteriorly at an angle of around 45°. Lower lip outer plate weakly notched, lobes of even size. Mandibular molar reduced and triturating, palp reduced, 2 articles, article 2 distally rounded. Maxilla 1 palp 2-articulate, reduced and slender. Gnathopods densely setose, pereopods weakly setose. Gnathopod 1 slender, sexually dimorphic; coxa slightly produced anteroventrally, basis anterodistal lobe medium and slightly upturned, bearing three slender setae; propodus subrectangular and narrow, with a strongly setose anterodistal lobe, palm acute, short, entire, without posterodistal tooth defining palm, without defining robust seta; dactylus greatly overreaching palm. Gnathopod 2 robust and longer than gnathopod 1, with long, dense simple setae on margins; basis anterodistal lobe medium and rounded, with four slender to robust setae on lobe margin, five robust setae on anterior margin of basis; carpus subtriangular; propodus longer than carpus; propodus broad, ovoid, produced into an anterodistally setose lobe; palm acute, excavate, with small subacute posterodistal tooth defining palm, with one defining robust seta; dactylus subequal in length to palm. Pereopods 3 -4 similar in size and shape; basis expanded and glandular; merus expanded to form an acute lobe. Pereopod 5 basis circular, distal articles broad, propodus prehensile. Pereopod 6 shorter than pereopod 7, merus and carpus similar width to propodus, propodus prehensile. Epimeron 3 posteroventral corner rounded, no tooth. Uropod 1, in situ, reaching to end of uropod 2 peduncle; peduncle distoventral spur absent. Uropod 2 peduncle with rounded lateral distoventral process. Uropod 3 broad, peduncle with distal robust setae absent, rami short; outer ramus with two recurved robust setae; patch of denticles; inner ramus with just slender distal setae. Telson subtriangular, with two large recurved cusps and with 4 slender setae per lobe.

Female. Similar to the male except for gnathopod 1 basis anteroventral lobe reduced, merus is weakly setose; carpus shorter than propodus, carpal lobe slightly truncated; propodus weakly setose, anterodistal lobe reduced. Gnathopod 2 weakly setose, carpus shorter than propodus, carpal lobe rounded; propodus anterodistal lobe reduced, palm weakly excavate, posterodistal tooth reduced. Uropod 2 peduncle laterodistal projection absent.

Remarks.

This relatively rare species can be aligned to J.L. Barnard’s (1972) material and can be identified by the shape of the gnathopods 1 and 2 propodi and palms. The other interesting feature which when first observed in Barnard’s description is the reduced mandibular palp. When the Eve Bay material was collected and dissected it was found to have a very similar mandibular form. If this is a valid character, along with the distinct presence of a setose anterodistal lobe on each of the gnathopod 1 and 2 propodi and the reduced, angled palm of gnathopod 1, validates this material as a new species.

Barnard (1972) described two males one 6.2 mm (E975), one 4.8 mm (E979), and mentioned in the description he only had two specimens and thought they maybe different species based on the presence/absence of the lobe on the uropod 2 peduncle (present on 6.2 mm male/absent on 4.8 mm male), the broadened articles of pereopod 5 (slightly broader than P. lessoniae ) and the excavation of gnathopod 2 palm (more strongly excavated than P. lessoniae ). He then mentions three stations where it was collected. The only material that has been able to be found is the 4.8 mm male and this material (when examined) matches to P. evensis sp. n. and differs from P. lessoniae by the shape and structure of gnathopod 1 (consistent across sizes - 9 mm length described here and the 4.8 mm male he described). The description notes that the uropod 2 peduncular process is absent, however when examined this character is obvioiusly there. The 6.2 mm material was not able to be located and so cannot be verified.

Etymology.

The specific name is taken from the name of the type locality, Eve Bay.

Distribution.

North Island, New Zealand.