Australorchestia, Serejo & Lowry, 2008

Serejo, C. S. & Lowry, J. K., 2008, The Coastal Talitridae (Amphipoda: Talitroidea) of Southern and Western Australia, with Comments on Platorchestia platensis (Krøyer, 1845), Records of the Australian Museum 60 (2), pp. 161-206 : 163-168

Australorchestia n.gen.

Type species. Australorchestia occidentalis n.sp.

Etymology. The name is a combination of Australia and the generic name Orchestia .

Diagnosis. Antenna 2 geniculate, sexually dimorphic, male peduncle slightly enlarged when compared with female. Mandible left lacinia mobilis 4-dentate. Maxillipedal palp dactylus present, reduced. Gnathopod 2 subchelate; basis narrow; propodus palm posterodistal corner without protuberance; dactylus attenuated distally. Pereopods 3–7 cuspidactylate. Pereopod 4 carpus significantly shorter than carpus of pereopod 3. Pereopod 6 not sexually dimorphic. Pereopod 7 sexually dimorphic or not, distal articles (merus and carpus) slightly expanded in terminal males; basis lateral sulcus absent. Gills simple, sac-like and similar in size. Oostegites 2–5 setae with simple straight tips. Pleopods all well developed. Uropod 1 outer ramus with lateral marginal very robust setae. Uropod 2 outer ramus without marginal a robust setae. Telson longer than broad with 3–5 robust or setae per lobe.

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Merritt

absence Species composition. Australorchestia occidentalis

Transorchestia, 1982 Bousfield not geniculate with well- lobe developed attenuated not expanded slightly expanded absent lacking setae with at with least 1 seta curl-tipped 2 6 largest, New Zealand and northeastern Pacific, (Lake California estuarine indicate. pectinispina F n of This which Remarks specimens.sp the. habitat more Australorchestia . Despite were basal suggests also palustral the that found uncommon occidentalis Australorchestia genera inhabiting proposed, mud n.sp. mangrove clayey was could by found Bousfield habitat be, areas some one in.

and (1984). Some similarities with the palustral genera are:

left lacinia mobilis 4-dentate, article 2 of maxilliped palp. 162 Tethorchestia, 1984 Bousfield geniculate or small with lobe without attenuated expanded antero- proximally slender absent, present well developed setae lacking 2 setae with simple largest 6 2, Sea Caribbean and adjacent Western Atlantic seashore and terrestrial. one sp of figures. anomala F not palp distal sac-like distinctly described lobate obscurely setae. However cuspidactylate by, medially characters Bousfield 4–articulate, Australorchestia ; and not, (and gills present 1984, dactyli the 2) –. 6 in telson Australorchestia of similar the has pereopods palustral has the, simple lateral maxilliped 3 genera –7 and and has are on. p 1814 – seta seta spp. although pereopods suggesting Bousfield’s and that (1982 the this, 1984 peduncles genus) 4-dentate is possibly of pleopods cuspidactylate closely poorly related setose beach- to, Abbreviations genera given. Orchestia Floresorchestia, Leach 1984 1813 , not geniculate well- with small or lobe lobe * developed not attenuated expanded expanded expanded absent / weak lacking a setaeat 1 with least with seta at least 1 1 least simple largest 2 6, warm- Atlantic-Medi- and Indo-Pacific Sea terranean Caribbean Sea seashore with terrestrial few terrestrial description the of genus, a on other given genera hopper subequal unexpanded combination the five in, outer Australorchestia genera Table in known size ramus basis 1 of.. Comparisons and, Although characters 4 of - of dentate female sac-like uropod can similar, be cuspidactylate gnathopod and, 2 and between generally. more lack in some specifically of 2 these distinguished, coxal marginal beach-hopper aspects genera gills by to setae 2 the are the – by 6 Bousfield geniculate with without beach-hopper cuspidactylate Mardsen Chroestia 1984 & Fenwick, not geniculate with well-devel- oped lobe atten- strongly attenuated uated distally slightly expanded expanded slender present absent usually well present, developed developed lacking setae lacking 1 with seta at with curl-tipped simple?, largest 2 6 tropical tropical eastern) Australia (QLD temp. and estuarine mostly not state this formal character in the (9 mm 11.3 Type 1 males slide AM mm material, Australorchestia stubs and P (habitus 69130 12 J. 053 Hfemales () 1 OLOTYPE AM – slide J055 Figs P69153,,, stub J AM 057: occidentalis male 1– J – P 4 (056 stub J 69132 059 11.6, SEM) J. 060 P, mm ARATYPES mangroves) n micrographs; AM 1. sp female. P69130: male near 6.3); did) 1984). mouth Carnarvon of, Gascoyne Western Australia River (end (24°54.2 of Harbour 'S 113°38.96 Road 'E)),, 4 - dentate among Australorchestia . gen. n geniculate lobe without medially attenuated strongly distally slender expanded slightly absent well present, developed – 3 with 1 setae lacking setae simple in subequal size tropical western Australia mangroves and mudflats clayey (Bousfield 12, 278. fig * male;. and 9 fig, (C and Type small end. Serejo pneumatophores of locality mangrove Harbour & J..K Mangroves. area Lowry Road and with),, 30 some Carnarvon near dead Oct mouth stones. 2003 seagrasses,. Western of on Gascoyne sand among substrate Australia River roots, differences adult 7 P 2 – 3 EP seta on: 272 1971 (2003 stones seagrasses 24°54.2, WA on 'S sand 768 113 among. ° substrate 38.96 roots 'E),, C and small. Serejo pneumatophores mangrove & J.K. Lowry area and with, 30 some dead Oct. Morphological palp MP of dactylus basis and of carpus male on row of pits setae distolateral robust margins ramus ramus margin setae – 6 2 ” amplexing “, (Bousfield an with respectively in and WA National Additional a 9 sheltered 770 females; Park 14 material males bay,, AM (22, C ° and 08 P. examined 69133 Serejo 'S 27 113 females, ° & Mangrove 59. J. ' Western E K) (., some Lowry low Bay thick Australia ovigerous, 31, Cape mangroves Oct:. 1 Range 2003), male AM,. 1 Table 2 A 2 article 2 G male G female 2 merus submarginal U 1 U 1 outer outer U2 Oostegites gills coxal distribution habitat occasionally a lobe small P Shark moving 69134 Bay, into Disappointment (26 clayey °40.21 mudflats 'S 113 Loop °40.31 with, Henri 'E small), Freycinet low banks rock Harbour platform covered,

in holes interspersed with small smooth clay channels, C. Serejo & J.K. Lowry, 4 Nov. 2003, WA 775.

Etymology. The specific name refers to the endemic locality of this species from western Australia.

Diagnosis. As for the genus.

Description

Male, 11.6 mm. Eye medium, 1⁄5–1/3 head length. Antenna 1 short, rarely longer than peduncle article 4 of antenna 2. Antenna 2 shorter than head and first 3 pereonites; geniculate at flagellum; peduncular articles slightly expanded; with sparse, small robust setae; article 5 subequal to article 4. Epistome of upper lip without robust setae. Lower lip distolateral setal tuft present. Mandible left lacinia mobilis 4-dentate. Maxilliped palp article 2 without distomedial lobe, article 4 present, reduced.

Gnathopod 1 subchelate; posterior margin of carpus and propodus with rugose lobe; propodus sub-triangular; palm strongly excavated, transverse; dactylus subequal in length to palm, without ventral setal row, simplidactylate. Gnathopod 2 subchelate; palm acute, with subquadrate protuberance near dactylar hinge and large midpalmar sinus, posterodistal corner without enlarged protuberance; dactylus longer than palm, attenuated distally. Coxae 2–4 as wide as deep. Pereopods 3–7 cuspidactylate; dactylus without row or patch of dorsal short setae. Pereopod 4 dactylus slightly thickened and pinched posteriorly, different to pereopod 3 dactylus. Pereopod 5 propodus longer than carpus. Pereopod 6 not sexually dimorphic; shorter than pereopod 7; coxa posterior lobe anterodistal corner rounded, with 1 marginal seta, posterior margin perpendicular to ventral margin, outer surface with ridge. Pereopod 7 sexually dimorphic; basis without lateral sulcus, posterodistal lobe present; distal articles (merus and carpus) slightly expanded in terminal males; carpus sub-rectangular. Coxal gills 2–6 simple or slightly lobate and subequal in size.

Pleopods 1–3 well developed, biramous. Pleopods 1–2 peduncle without marginal setae. Pleopod 3 peduncle with one marginal slender seta. Epimeron 2 subequal in length to epimeron 3. Epimeron 2–3 posterior margin smooth, with one tiny seta faraway from the corner, posteroventral corner with small subacute spine, ventral margin without robust setae. Uropod 1 peduncle with 7 robust setae in two rows; distolateral robust seta present, small, less than 1/4 length of outer ramus; inner ramus subequal in length to outer ramus, with 3 marginal robust setae; outer ramus with 2–3 marginal robust setae. Uropod 2 peduncle with 4 robust setae in two rows; inner ramus subequal in length to outer ramus, with 2 marginal robust setae; outer ramus without marginal robust setae. Uropod 3 peduncle with 4 robust setae; ramus slightly shorter than peduncle, oval to spatula-shape, broad distally, without marginal setae and with 4–5 apical setae. Telson longer than broad; entire; dorsal midline entire; with marginal and apical robust setae; about 3 to 5 robust setae per lobe.

Female (sexually dimorphic characters). 6.3 mm. Antenna 2 peduncular articles narrow. Gnathopod 1 parachelate, with very short palm surpassed by dactylus; propodus ovoid; palm very short, acute; dactylus longer than palm. Gnathopod 2 basis narrow; about 3.2× longer than wide, palm obtuse; dactylus shorter than palm. Pereopod 7, merus and carpus slender. Uropod 1 outer ramus with 1 marginal seta.

Oostegites longer than wide; setae with simple straight tips.

Oostegites 2–5 weakly setose (from 6 to 15 setae).

Habitat. Marsh-hoppers living on mud of mangroves and on a clayey mudflat of a salty embayment of Shark Bay, WA.

Remarks. See discussion of Australorchestia and Table 1.