Transorchestia marlo, 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 : 200-205

Transorchestia marlo n.sp.

Figs 30–33

Type material. HOLOTYPE: 1 male, 18.6 mm, AM P69136 (slide, stubs J071–J074, J075 [part, G1], J077–J079, SEM micrographs), near mouth of Separation Creek , Victoria (38°37.96'S 143°53.78'E), freshwater creek with stony bottom, under stones (freshwater), C. Serejo & J.K. Lowry, 12 Oct. 2003, VIC 131 . PARATYPES: 1 male, 15.5 mm (habitus), AM P69137 (stub J081) ; 1 juvenile male, 13.1 mm, AM P69138 (stub J075 [part, G2]) ; 1 female 13.6 mm, AM P69139 (slide, stub J076, J080, SEM micrographs) ; 73 specimens, AM P69140 , mouth of Erskine River just beside the swinging bridge, Lorne , Victoria (38°32.1'S 143°58.59'E), limestone rocks in small pools (freshwater), C. Serejo & J.K. Lowry, 12 Oct. 2003, VIC 129 ; 1 male AM P69143, VIC 131 .

Type locality. Near mouth of Separation Creek , Victoria (38°37.96'S 143°53.78'E), freshwater creek with stony bottom, under stones (freshwater) .

Additional material examined. Victoria: 10 males and 22 females, AM P69141, large marsh near Snowy River Boat Club, Marlo (37°47.88'S 148°31.6'E), beach-hoppers sheltering in dead logs in marsh on the margin of the Snowy River (freshwater), C. Serejo & J.K. Lowry, 9 Oct. 2003, VIC 121 .

Western Australia: 3 males and 10 females, AM P69142, Wilson Inlet , Denmark River mouth (34°58.28'S 117°22.04'E), soil bank on edge of river just where it opens into the inlet, C. Serejo & J.K. Lowry, 22 Oct. 2003, WA 757 .

Etymology. This species is named for the town of Marlo, near the site of the first collections of the species.

Diagnosis. Gnathopod 2, basis anteriorly serrate, palm very concave posterior to a strong distal hinge tooth; dactylus sinuous, subequal in length to palm, not attenuated distally. Male pereopods 6–7 article 5 about 2.3× longer than wide. Basis of female gnathopod 2 about 1.7× as long as wide. Oostegites 2–5 with curl-tipped setae. Oostegite 2 with 37 setae distributed unevenly.

Description

Male, 18.6 mm.Antenna 1 short, rarely longer than peduncle article 4 of antenna 2, flagellum with 7 articles. Antenna 2 shorter than head and first 3 pereonites, peduncular articles expanded, with sparse, small robust setae; article 5 subequal than article 4; flagellum with 20 articles. Epistome of upper lip without robust setae. Lower lip distolateral setal tuft absent. Mandible left lacinia mobilis 4-dentate. Maxilliped palp article 2 without mediodistal lobe, article 4 present, reduced.

Gnathopod 1 sexually dimorphic; subchelate; posterior margin of merus, carpus and propodus with rugose lobe; propodus subtriangular; palm transverse; dactylus shorter than palm, simplidactylate. Gnathopod 2 sexually dimorphic; subchelate; basis anteriorly serrate; merus without medial lobe; carpus posterior margin not distally concave; palm concave posterior to a strong distal hinge tooth, posterodistal corner without protuberance; dactylus subequal in length to palm, not 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 thickened and pinched posteriorly, different to pereopod 3 dactylus. Pereopod 5 propodus subequal to or shorter than carpus. Pereopod 6 sexually dimorphic; shorter than pereopod 7; coxa posterior lobe anterodistal corner subquadrate, with 12 marginal setae, posterior margin perpendicular to ventral margin, outer surface with ridge; carpus expanded, about 2.3× longer than wide. Pereopod 7 sexually dimorphic; basis without lateral sulcus, posterodistal lobe present; distal articles expanded; carpus subrectangular, about 2.3× longer than wide. Coxal gills convoluted or simple. Pereopods 3–5 gills smaller than gills 2 and 6.

Pleopods 1–3 well developed, biramous. Pleopod 1 peduncle without marginal setae. Pleopod 2–3 peduncle with few marginal robust setae. Epimeron 2 subequal in length to epimeron 3. Epimera 1–3 posterior margin minutely serrate, posteroventral corner acutely produced, ventral margin without robust setae. Uropod 1 peduncle with more than 6 robust setae; distolateral robust seta absent; inner ramus subequal in length to outer ramus, with 3 marginal robust setae; outer ramus with 5 marginal robust setae. Uropod 204 Records of the Australian Museum (2008) Vol. 60 2 peduncle with 10 robust setae in two rows; inner ramus subequal in length to outer ramus, with 2 marginal robust setae; outer ramus with 3 marginal robust setae. Uropod 3 peduncle with 6 robust setae; ramus shorter than peduncle; oval to spatula-shape, broad distally; ramus with 5 marginal setae and 3 apical setae. Telson longer than broad; apically incised; dorsal midline halfway; with marginal and apical robust setae; more than 10 robust setae per lobe.

Female (sexually dimorphic characters), 13.6 mm. Antenna 2 peduncular articles narrow. Gnathopod 1 subchelate, posterior margin of merus, carpus and propodus without rugose lobe; propodus subrectangular; dactylus subequal in length to palm. Gnathopod 2 mitten-shaped; basis expanded proximally, about 1.7× longer than wide; posterior margin of merus, carpus and propodus with rugose lobe; dactylus shorter than palm. Pereopod 6 carpus slender. Pereopod 7 distal articles slender. Oostegites longer than wide; setae with curl-tips. Oostegites 2–4 moderately setose (between 37 to 15 setae respectively).

Habitat. Found on mouth or on margin of rivers hidden under logs, roots and other organic matter.

Remarks. Transorchestia marlo n.sp. is part of the T. chiliensis (Milne-Edwards, 1840) complex because the palm of gnathopod 2 is concave posterior to a strong distal hinge tooth and pereopod 7 carpus is incrassate ( Bousfield, 1982). Transorchestia marlo n.sp. differs from T. chiliensis from Puerto Robalo, Chile ( Bousfield, 1982) as follows: the basis of male gnathopod 2 is distinctly serrate (versus not serrate); the palm and dactylus of gnathopod 2 are more strongly sinuous; the carpus of pereopod 7 is not so enlarged, and the basis of female gnathopod 2 is about 1.5× as long as wide (not 2× as long as wide). The Australian species is closer to Hurley’s (1957) material from New Zealand (considered here as T. serrulata Dana, 1852 ) in having a similar shape of gnathopod 2 (serrate basis and strongly sinuous palm and dactylus), but some differences were observed between these two taxa as follows: male pereopods 6–7 article 5 longer and less enlarged, about 2.3× longer than wide (versus 1.5× longer than wide); oostegites 2–5 are curl-tipped (illustrated as not curl-tipped, but could have been overlooked by the author); oostegite 2 with 37 setae distributed unevenly, with about 12–13 setae on one side and 24–25 setae on other side (versus about 33 setae distributed evenly [16–17 setae for each side]). The males figured here ( Fig. 30 , habitus = 15.5 mm; Fig. 31 , P 6–7 = 18.6 mm) are similar in size or larger from the male figured by Hurley (1957) (15.75 mm), which eliminates the age dependent factor that influences characters such as shape of gnathopod 2 and stoutness of pereopod 6–7. The juvenile form of gnathopod 2 was observed in a 13.1 mm male ( Fig. 32 ).

Distribution. Victoria: Marlo; Erskine River; Separation Creek. Western Australia: Wilson Inlet, Denmark River mouth.

Figures

Fig. 30. Transorchestia marlo n.sp., paratype male, 15.5 mm, habitus and head, AM P69137, mouth of the Erskine River, Victoria; holotype male, 18.6 mm, other parts, AM P69136, near mouth of Separation Creek, Victoria. Scales for habitus and H: 1 mm; remainder: 0.1 mm.

Fig. 31. Transorchestia marlo n.sp., holotype male, 18.6 mm, AM P69136, near mouth of Separation Creek,Victoria. Scales represent 0.5 mm.

Fig. 32. Transorchestia marlo n.sp., holotype male, 18.6 mm, U1–3, T,AM P69136, near mouth of Separation Creek,Victoria.; paratype female, 13.6 mm, G1–2, AM P69139; paratype juvenile male, 13.1 mm, G2, AM P69138, mouth of the Erskine River, Victoria. Scale for EP3: 1 mm; remainder: 0.2 mm.

Fig.33. Transorchestia marlon.sp., paratype female, 13.6 mm,O2–5,AM P69139, mouthof the Erskine River,Victoria;holotype male, 18.6 mm, PL1–3 and BR2–6, AM P69136, near mouth of Separation Creek, Victoria. Scales represent 0.5 mm.

Fig. 6. Bellorchestia richardsoni n.sp., holotype male, 22.3 mm, AM P60238, Point Ricardo, Victoria. Scales for G1–2: 1 mm; C1: 0.5 mm; remainder: 2 mm.

Fig. 7. Bellorchestia richardsoni n.sp., holotype male, 20.3 mm, T, EP1–3, AM P60238; paratype male, 22.7 mm, U1–3, AM P69239; paratype female, 21.8 mm, G1–2, AM P69240, Point Ricardo, Victoria. Scales for EP1–3, G1–2: 1 mm; remainder: 0.2 mm.