Pictonorchestia, Lowry & Springthorpe, 2021

Lowry, James K. & Springthorpe, Roger, 2021, Pictonorchestia, a new genus of riparian-hopper from New Zealand (Crustacea Amphipoda, Senticaudata, Talitridae), Zootaxa 4938 (3), pp. 346-350 : 346-347

Pictonorchestia gen. nov.

Type species. Orchestia dentata Filhol, 1885 , monotypy.

Included species. Pictonorchestia dentata ( Filhol, 1885) .

Category. Mascupod.

Ecological type. Riparian-hopper.

Etymology. Named for the town of Picton in combination with the stem Orchestia .

Size. Male, 14 mm, female, 9.5 mm.

Diagnostic description (based on Chilton (1919) and Hurley (1956)).

Eye medium (1/5–1/3 head length). Antenna 1 short, not reaching midpoint of peduncular article 5 of antenna 2. Antenna 2 peduncular articles slightly or strongly incrassate; article 3 without plate or process ventrally. Maxilliped palp article 2 with distomedial lobe; article 4 reduced, button-shaped. Gnathopod 1 sexually dimorphic; parachelate (simple in female); posterior margin of carpus and propodus each with lobe covered in palmate setae (without palmate setae in female); carpus longer than propodus; propodus anterior margin with 5 groups of robust setae or with 6 or 7 groups of robust setae, propodus ‘subtriangular’ with well-developed posterodistal lobe, palm slightly obtuse. Gnathopod 2 subchelate (mitten shaped in female); posterior margin of merus, carpus and propodus each without lobe and without palmate setae (merus and carpus without palmate setae in female); propodus palm slightly acute (obtuse in female), sigmoidal (straight in female), with proximal sinus, with shallow distal sinus, with proximal spine defining palm; dactylus posterior margin with posteroproximal projection, dactylus not modified distally, blunt, shorter than posterior margin of propodus (dactylus short, distally acute in female). Oostegites setae with simple smooth tips. Pereopod 5 merus broad, longer than broad, expanded distally; dactylus long, slender, dactylus not inflated. Pereopod 6 not sexually dimorphic; coxa posterior lobe with anteroventral corner rounded, not produced; basis slightly expanded. Pereopod 7 not incrassate; articles not modified; male basis not expanded into plate-like structure; basis expanded; merus unexpanded; carpus unexpanded. Pleonites 1–3 without dorsal spines. Pleopods 1–3 well-developed. Epimera 1–3 slits absent. Uropods 1–2 rami without apical spearshaped setae. Uropod 1 peduncle distolateral robust seta absent; endopod with marginal robust setae in 2 rows; exopod with marginal robust setae in one row. Uropod 2 exopod with marginal robust setae in 1 row; endopod with marginal robust setae in 2 rows. Uropod 3 ramus linear (narrowing); shorter than peduncle. Telson tapering distally, without groove, with apical and marginal robust setae, with 3–9 robust setae per lobe.

Remarks. Pictonorchestia does not appear to be similar to any other New Zealand genus. No other New Zealand coastal taxon has an interlocking palm/dactylus on gnathopod 2 (projection on the posterior margin of the gnathopod 2 dactylus). Two other New Zealand genera ( Bellorchestia and Transorchestia Bousfield, 1982 ) have an incrassate antenna 2, but unlike Pictonorchestia , both have sexually dimorphic seventh pereopods. Several other New Zealand taxa such as Bellorchestia chathamensis ( Hurley, 1956) , Puhuruhuru aotearoa Duncan, 1994 , Orchestia aucklandiae Spence Bate, 1862 , Orchestia bollonsi Chilton, 1909 , Talorchestia cookii Filhol, 1885 , ‘ Bellorchestia’ kirki ( Hurley, 1956) and ‘ Bellorchestia’ tumida ( Thomson, 1885) have the carpus and propodus of gnathopod 1 with palmate lobes, but these genera do not have an incrassate second antenna.

Only five genera ( Carpentaria Lowry, Springthorpe & Myers 2020 , Transorchestia Bousfield, 1982 , Amphiatlantica Lowry & Myers, 2019 , Pictonorchestia , gen. nov., and Asiaorchestia Lowry & Myers, 2019 ) have an interlocking palm/dactylus on gnathopod 2 (a posterior projection on the gnathopod 2 dactylus). Of these genera Amphiatlantica and Transorchestia , like Pictonorchestia , have an incrassate second antenna. Amphiatlantica , like Pictonorchestia , does not have a sexually dimorphic seventh pereopod, but Amphiatlantica has only the carpus of gnathopod 1 with a palmate lobe and uropod 1 without marginal setae on the exopod.

Pictonorchestia is currently known from both sides of Cook Strait.

Distribution. New Zealand. Picton and Waitohi Stream Estuary ( Chilton 1919, Hurley 1956), South Island; Kapiti Island, North Island ( Filhol 1885).