Arcitalitrus nana, R Peart, 2006

R Peart, 2006, The Amphipod Genus Arcitalitrus (Crustacea: Amphipoda: Talitridae) of New South Wales Forests, With Descriptions of Six New Species, Records of the Australian Museum 58, pp. 97-118 : 102-103

Arcitalitrus nana n.sp.

Figs. 4, 18–20

Type material. HOLOTYPE, ♀, 15.0 mm, AM P60956, December, 1999, M. Gray, G. Milledge and H. Smith . PARATYPES, male AM P60955; 35 specimens , AM P60964 . Paratypes are all from the type locality.

Type locality. Five km ENE of Lowanna, Nana Creek State Forest (30°11'51"S 152°56'53"E) New South Wales .

Other material examined. New South Wales, Australia: Junction of Urumbilum Creek road and Loudens road, Orara State Forest (30°19'35"S 152°55'00"E), 5 specimens, 9–23 December 1999, collected from pitfall traps, M. Gray, G. Milledge and H. Smith; nearly 2 km east of Mount Kariong , Brisbane Water National Park (33°27'50"S 151°17'04"E), 40 specimens, 1–15 December 1999, collected from pitfall traps, M. Gray, G. Milledge and H. Smith; end of Little North Arm road, west bank of Rosewood River , Dorrigo National Park (30°24'06"S 152°46'18"E), 25 specimens, 10–24 November 1999, collected from pitfall traps, M. Gray, G. Milledge and H. Smith; Reids Creek road, Gladstone State Forest (30°31'01"S 152°48'29"E), 20 specimens, 12– 25 November 1999, collected from pitfall traps, M. Gray, G. Milledge and H. Smith; beside Hacking River , Lady Wakehurst Drive, Royal National Park (34°09'47"S 151°00'55"E), 35 specimens, 6–20 December 1999, collected from pitfall traps, M. Gray, G. Milledge and H. Smith; approximately 0.3 km east of Artillery Hill , Sir Bertram Stevens Drive, Royal National Park (34°04'55"S 151°03'40"E), 28 specimens, 6–20 December 1999, collected from pitfall traps, M. Gray, G. Milledge and H. Smith; 3 km northwest of Caledonia Knob, Bagawa State Forest (30°08'44"S 152°55'47"E), 37 specimens, 10–23 November 1999, collected from pitfall traps, M. Gray, G. Milledge and H. Smith .

Description. Based on holotype female. Body shape normally laterally compressed; cuticle calcification absent. Eye large (greater than 1 ⁄ 3 head length). Antenna 2 longer than head and first 3 pereonites; peduncular articles narrow. Mandible left lacinia mobilis 4 dentate. Maxilliped outer plate distally acute/arcuate; palp dactylus present and distinct. Pereonite 1 sternite without papillose process. Gnathopod 1 not sexually dimorphic; simple; merus and carpus not expanded; propodus subrectangular; palm absent; dactylus longer than palm. Gnathopod 2 not sexually dimorphic; chelate; narrow; merus and carpus expanded posteriorly; propodus “mitten-like”; palm obtuse; smooth; dactylus shorter than palm. Pereopods 3–7 long (½ length of body); simplidactylate. Pereopod 4 carpus similar in length to pereopod 3 carpus, dactylus similar to pereopod 3 dactylus. Pereopod 7 posterodistal lobe present. Gill 2 lobate, not incised. Gills 3–5 lobate, smaller than gills 2 and 6. Gill 6 lobate, anterior margin convoluted, subapically incised along posterior margin. Oostegites long (length greater than 2× width), weakly setose, setae with simple smooth tips. Epimera 1 to 3 not convergent. Epimeron 2 subequal in length to epimeron 3. Epimeron 3 posteroventral margin smooth, posteroventral corner with small subacute tooth. Pleopod 1 well developed, biramous, rami subequal in length to peduncle; inner ramus with 13 articles; outer ramus with 11 articles, outer ramus with more than 10 articles. Pleopod 2 well developed, biramous, rami shorter than peduncle; inner ramus with 8 articles; outer ramus with 6 articles. Pleopod 3 reduced, uniramous, rami shorter than peduncle; inner ramus with 1 articles; outer ramus without articles. Uropod 1 not sexually dimorphic; peduncle with 4 robust setae on peduncle; inner ramus shorter than outer ramus, with 4 robust setae on the margins, with 4 apical robust setae; outer ramus without marginal Etymology. Named for Nana Creek State Forest, the type locality and treated as a noun in apposition.

Habitat. Forest floor leaf-litter.

Remarks. Arcitalitrus nana is a member of the “sylvaticus” species group. It differs from other species in the group in having a uniramous pleopod 3, in having 3–5 marginal robust setae on the inner ramus of uropod 2 and in having the telson incised halfway. Arcitalitrus nana and Ar. orara both have large eyes. Arcitalitrus nana and Ar. belbucca both have more than 10 dorsal robust setae on the telson and both species, plus Ar. orara , have the inner ramus of uropod 1 shorter than the outer. Arcitalitrus nana and Ar. belbucca and Ar. bassianus all have pleopod 2 outer ramus with 6–10 articles.

Distribution. New South Wales: Lowanna, Nana Creek State Forest; Caledonia Knob, Bagawa Creek State Forest; Orara State Forest; Brisbane Water National Park; Dorrigo National Park; Gladstone State Forest; Royal National Park.