Exampithoe plumosa, 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 : 28-30

Exampithoe plumosa sp. n. Figs 1, 2, 3, 4

Type material.

Holotype, male, 10 mm, NIWA 121270, KH-NZ1-9, from drifting Durvillaea antarctica raft from near Taiaroa Head, inside Otago Harbour, Dunedin, New Zealand, 45°46'19"S, 170°43'30"E, 0 m depth, 22 January 2010, J. Waters.

Paratypes: Female, 7 mm, NIWA 121269, Male, 9 mm, ZMH K-46915, KH-NZ1-9, from drifting Durvillaea antarctica raft near Taiaroa Head, inside Otago Harbour, Dunedin, New Zealand, 45°46'19"S, 170°43'30"E, 0 m depth, 22 January 2010, J. Waters.

Diagnosis.

Male: Eye prominent. Antennae similar length to each other. Antenna 2 peduncular articles robust but not elongated. Epistome and upper lip, in situ, directed straight down, perpendicular to the head. Lower lip outer plate entire. Mandible molar well developed and triturating; palp slender and three-articulate, article three distally rounded. Maxilla 1 palp moderately developed. Pereopods setose with plumose setae. Gnathopod 1 robust and sexually dimorphic, coxa slightly produced anteriorly, basis anteroventral lobe prominent and setose, propodus subrectangular, anterodistal setose lobe absent, palm acute and concave, defined by a very small rounded posterodistal tooth and a large robust seta; dactylus shorter than palm. Gnathopod 2 slender and slightly longer than gnathopod 1, sexually dimorphic; basis anteroventral lobe medium sized and setose; carpus subovoid; propodus subequal in length to carpus, propodus narrow, anterodistal lobe absent, palm acute, midpalmar tooth/corner present, defining posterodistal tooth absent, robust seta present; dactylus shorter than palm length. Pereopods 3 and 4 similar in size and shape, basis expanded and glandular; merus slightly expanded, lobe present. Pereopod 5 basis ovoid; distal articles slender; propodus weakly prehensile. Pereopods 6-7 similar lengths; merus and carpus broader than propodus; propodus weakly prehensile.

Epimeron 3 posteroventral corner rounded without tooth. Uropod 1, in situ, reaching to the end of uropod 2, peduncle distoventral spur absent. Uropod 2 peduncle rounded lateral distoventral process absent. Uropod 3 broad, peduncle with two distal robust setae; rami very short, outer ramus with two recurved robust setae, patch of denticles; inner ramus with just slender distal setae. Telson subrectangular, cusps absent, light denticles present, with lateral and apical setae.

Female. Similar to male except for gnathopod 1 merus lobe reduced and weakly setose, carpus more slender than male and less setose and subequal in length to the propodus; propodus narrow, weakly setose, palm convex, not sculptured.

Etymology.

Named plumosa , a derivative of the latin plumosus meaning feathered, referring to the feathered nature of majority of the setae present on the type material.

Remarks.

This is an interesting species for a couple of reasons. Firstly, it is the first record of this genus from the South Island of New Zealand. The only other Exampithoe species recorded from New Zealand is Exampithoe taylori Hughes & Peart, 2015. These two species are recorded from almost opposite ends of the country with over 1000 km between them and situated on water bodies influenced by different currents and geophysical history. Though the two species have some similarities, such as the shape of gnathopod 2 propodus (narrow, palm with a subquadrate midmedial tooth), the shape of the lower lip outer plate (entire), similar setation and shape of uropod 3 (broad peduncle, small rami, 2 distal peduncular robust setae, 1 marginal robust seta), there are also a number strong differences that give the necessity of these being separate species. These differences include: the shape and length of the antennae (A1 and A2 similar length in E. plumosa sp. n. A1 shorter than A2 in E. taylori . Antenna 2 peduncular articles are robust but not elongated in E. plumosa sp. n. and are robust but considerably elongated in E. taylori ); the shape and size of gnathopod 1 (robust with shortened articles, propodus ovoid to subrectangular, palm excavate with small posterodistal tooth, subquadrate predactylus tooth and large defining robust seta in E. plumosa n.sp. and narrow with elongated articles, propodus subrectangular, palm convex, no defining tooth or predactylus tooth or robust seta in E. taylori ). The other main difference between the two species is the majority of the setae on every appendage of E. plumosa are feathered (plumose) giving this animal a strongly fuzzy look. Whilst E. taylori has numerous setae on the appendages, very few are plumose.

The second interesting aspect of the discovery of this species is that the specimens were collected from a kelp raft. While many organisms can be found on floating or rafting macroalgae, ampithoids are only occasionally recorded rafting ( Thiel and Gutow 2005) but are not obligate rafters. As there are no other records of this species, it cannot be inferred whether it is an obligate rafter or not. The kelp was determined to have been drifting in the water for around five weeks (determined by the stage of goose barnacle settlement - Waters et al. in press) and probably originating from southern New Zealand. This is the first record of an ampithoid in this area of New Zealand.

Distribution.

Only known from the type locality, Otago Harbour, South Island, New Zealand.