Pseudopleonexes lessoniae (Hurley, 1954)

Peart, Rachael A. & Loerz, Anne-Nina, 2018, Ampithoidae (Crustacea, Amphipoda) from New Zealand, ZooKeys 733, pp. 25-48 : 36-41

Pseudopleonexes lessoniae (Hurley, 1954) Figs 9, 10, 11, 12

Pleonexes lessoniae Hurley, 1954: 620-626, figs. 1-2.

Pseudopleonexes lessoniae .- Conlan 1982: 2020.- Just 2002: 31-40.- Peart 2006: 1-22.

not Ampithoe (Pleonexes) lessoniae .- Barnard 1972: 44, figs 13-14.

Material examined.

Holotype: male, 9 mm, NIWA 121308, slide 90 Hurley collection, Island Bay, Wellington, New Zealand, 41°20'39.8"S, 174°46'25.9"E, on Lessonia variegata , coll. J.G. Gibbs, 1 August 1950.

Paratype: female, 5.75 mm, NIWA 12309, slide 91, Hurley collection, Island Bay, Wellington, New Zealand, 41°20'39.8"S, 174°46'25.9"E, on Lessonia variegata , coll. J.G. Gibbs, 1 August 1950.

All material (other than type material) collected by hand by M. Thiel & A.N. Lörz from Macrocystis sp. kelp, Breaker Bay, Wellington, 41.33°S, 174.83°E, 0-1 m between 30th Jan– 1st Feb 2013: NIWA 96675-96677, 17 specimens; NIWA 96679, 5 specimens, NIWA 96683-96686, 9 specimens; NIWA 96688-96698, 27 specimens; NIWA 96700-96701, 3 specimens; NIWA 96792-96795, 10 specimens; NIWA 96797-96804, 42 specimens; NIWA 96810 -96818, 59 specimens; NIWA 96819-96820, 15 specimens; NIWA 96822, 14 specimens; NIWA 96824, 7 specimens; NIWA 96826, 1 specimen. NIWA 120146 on SEM stud

Diagnosis.

Male: Eye absent (holotype), eyes prominent (additional material examined). Epistome and upper lip, in situ, directed posteriorly around 45°. Antenna 1 longer than antenna 2. Lower lip outer plate slightly notched, almost entire, margin sinusoidal to sometimes flat with larger, subacute corners. Mandible molar reduced and triturating, palp three-articulate, article three distally beaked. Maxilla 1 palp poorly developed and slender tipped with slender plumose setae. Gnathopods strongly setose. Pereopods weakly setose. Gnathopod 1 not sexually dimorphic; coxa not anteroventrally produced; basis anterodistal lobe reduced and rounded bearing on slender seta; propodus subrectangular, anterodistal setal lobe absent, palm transverse, entire, without midmedial tooth, with posterodistal tooth defining palm and one small defining robust seta; dactylus overreaching palm. Gnathopod 2 more robust and larger than gnathopod 1, sexually dimorphic, with long plumose setae on margins; basis anterodistal lobe large and rounded, bearing around 10 robust setae on the margin; carpus subtriangular; propodus longer than carpus; propodus broad, anterodistally setose lobe absent; palm acute, entire (sometimes slightly excavate), midpalmar tooth absent, with small suba cute posterodistal tooth defining palm, and one defining robust seta; dactylus subequal to palm. Pereopods 3-4 similar in size and shape, basis expanded and glandular; merus expanded and glandular, forming an acute lobe. Pereopod 5 basis circular, distal articles broad to slender (depending on size), propodus prehensile. Pereopod 6-7 increasing in length, merus and carpus similar widths to propodus (slightly wider), propodi prehensile. Epimeron 3 posteroventral corner rounded without tooth. Uropod 1, in situ, reaching only to the end of uropod 2 peduncle; peduncle distoventral spur absent. Uropod 2 peduncle with large rounded distolateral process. Uropod 3 broad, peduncle without distal robust setae, rami short, outer ramus with two strongly recurved robust setae, patch of denticles; inner ramus with just slender distal setae. Telson subtriangular with strongly recurved cusps, denticles absent, with one slender seta per lobe.

Remarks.

Described by Hurley (1954) from Wellington, New Zealand, this species is a small, robust amphipod dwelling in Lessonia variegata . Hurley (1954) described it as having similarities to members of the Ampithoe group, Pleonexes . When the genus Pseudopleonexes was constructed (Conlan, 1982), this species was placed as the type of the genus. It has strongly plumose, long setae on the gnathopod 2, a character represented in most of the other species in the genus. Hurley’s types have been located, and are in the NIWA Invertebrate Collection (NIC).

Barnard (1972) assigned two specimens from New Zealand as P. lessoniae however, examination of one of the specimens (the other is not locatable) and some confusion in the description indicate that these are not of this species. Comparison with freshly collected material indicates these should be treated as a new species (described above as P. evensis sp. n.). Pseudopleonexes lessoniae sensu stricto differs from P. evensis sp. n. by the absence of an anterodistal setose lobe on the propodi of gnathopods 1 and 2 (strongly present in P. evensis sp. n.) and the strongly transverse gnathopod 1 palm, also half the width of the propodus (acute, greatly reduced palm in P. evensis sp. n.).

The material described here is from Breaker Bay, very close to the type locality of Island Bay (4.5 km ENE) and was very abundant in Macrocystis sp. and until molecular examination is carried out is placed with P. lessoniae (Hurley, 1954). The main differences involve the apparent presence/absence of the eye and presence of butterfly and heart-shaped pits and fine hairs covering the pereon and pereopods of the recently collected material (fig. 12).

Distribution.

Wellington area, New Zealand.