Bellorchestia richardsoni, 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 : 170

Bellorchestia richardsoni n.sp.

Figs 5–8

Type material. HOLOTYPE: male, 22.3 mm, AM P69238 (1 slide, stubs J095–J097, J099, J101–J103) . PARATYPES: male, 20.7 mm (habitus) AM P69239 (stub J104) ; 1 female, 21.8 mm, AM P69240 (1 slide, stubs J6098, J100, SEM micrographs) ; 18 males and 120 females, AM P69241, supralittoral zone on exposed ocean beach, Point Ricardo , Victoria (37°48.39'S 148°38'E), under dead Sargassum on exposed ocean beach, C. Serejo & J.K. Lowry, 8 Oct. 2003, VIC 120 .

Type locality. Supra-littoral zone on exposed ocean beach, Point Ricardo , Victoria (37°48.39'S 148°38'E), under dead Sargassum on exposed ocean beach .

Etymology. The specific name honours Dr Alastair Richardson (University of Tasmania) who has been contributing to the knowledge of Australian talitrids for many years.

Diagnosis. Male gnathopod 2 palm acute, with 3 protuberances, 2 before dactylar enclosure and 1 defining the posterodistal corner; dactylus shorter than palm, strongly concave medially and not attenuated distally. Peduncle of pleopods 1–3 stout, peduncle 1 about 3× longer than wide, peduncle 2 about 2.5× longer than wide; peduncle 3 about 2.1× longer than wide.

Description

Holotype male, 22.3 mm. Eye medium, 1⁄5–1/3 head length. Antenna 1 short, rarely longer than peduncle article 4 of antenna 2. Antenna 2 longer than pereonite 3 and up to half body length; peduncular articles narrow; with sparse, small robust setae; article 5 long, about 2× article 4 length. Epistome with several robust setae. Lower lip distolateral setal tuft absent. Mandible left lacinia mobilis 5-dentate. Maxilliped palp article 2 with distomedial lobe, article 4 present, reduced.

Gnathopod 1 subchelate; posterior margin of propodus with rugose lobe; propodus subrectangular; palm obtuse; dactylus subequal in length to palm, without ventral setal row, simplidactylate. Gnathopod 2 subchelate; basis anteriorly smooth; merus without medial lobe; palm acute, with 3 protuberances, 2 before dactylar enclosure and 1 defining the posterodistal corner; dactylus shorter than palm, strongly concave medially and not attenuated distally. Coxae 2–4 deeper than wide. Pereopods 3–7 cuspidactylate; dactylus without row or patch of dorsal short setae. Pereopod 4 significantly shorter than pereopod 3. Pereopod 4 dactylus thickened and pinched posteriorly, different to pereopod 3 dactylus. Pereopod 5 propodus distinctly longer than carpus. Pereopod 6 sexually dimorphic; shorter than pereopod 7; coxa posterior lobe anterodistal corner rounded, with 5 or more marginal setae, posterior and ventral margins continuously rounded, outer surface with ridge; carpus expanded. Pereopod 7 sexually dimorphic; basis with lateral sulcus slightly pronounced, posterodistal lobe present; distal articles expanded; carpus subrectangular. Coxal gills convoluted, processiferous or lobate. Pereopods 3–5 gills smaller than gills 2 and 6.

Pleopods 1–3 well developed, rami shorter than peduncle; peduncle stout with several marginal robust setae, peduncle 1 about 3× longer than wide, peduncle 2 about 2.5× longer than wide; peduncle 3 about 2.1× longer than wide, both rami shorter than peduncle. Epimeron 2 subequal in length to epimeron 3. Epimeron 3 posterior margin smooth, with setae, posteroventral corner subquadrate, ventral margin without robust setae. Uropod 1 peduncle with 20–23 robust setae in two rows and a row of ventral setae; distolateral robust seta absent; inner ramus subequal in length to outer ramus, with 8–10 robust setae on each margin and 6–8 smaller setae on facial surface; outer ramus with 9 robust setae on outer margin; rami with ventral setae. Uropod 2 peduncle with 24 robust setae in two rows and a row of ventral setae; inner ramus subequal in length to outer ramus, with 7–8 robust setae on each margin and 6–7 smaller setae on facial surface; outer ramus with 5 robust setae on outer margin. Uropod 3 peduncle with 11 robust setae; ramus subequal in length to peduncle; oval to spatula-shape, broad distally; ramus with 24 marginal setae, and 4–5 apical setae. Telson broader than long; apically incised; dorsal midline vestigial or absent; with marginal and apical robust setae; around 19 setae per lobe.

Female (sexually dimorphic characters), 21.8 mm. Gnathopod 1 parachelate; posterior margin of merus, carpus and propodus without rugose lobe; palm minute, transverse and with a tuft of robust setae on the palmar angle; dactylus longer than palm. Gnathopod 2 mitten-shaped; basis narrow and long; about 2.8× longer than wide, posterior margin of propodus with rugose lobe; palm obtuse, smooth. Pereopod 6 carpus slender. Pereopod 7 distal articles slender. Oostegites longer than wide; setae with simple straight tips. Oostegites 2–4 moderately setose (around 24 setae).

Habitat. Exposed ocean beaches.

Remarks. Bellorchestia richardsoni n.sp. is similar to Bellorchestia pravidactyla described from Tasmania by Haswell (1880) in general aspects of the body, such as peduncular article 5 of antenna 2 which is long, about 2× article 4 length, and male gnathopod 1, which is subchelate with a transverse palm. Some differences between these species are the propodus of male gnathopod 1, which has a well-developed rugose lobe (versus small lobe, nearly undistinguished), male gnathopod 2 with 3 protuberances, 2 before dactylar enclosure and 1 defining the posterodistal corner (versus no protuberances) and female gnathopod 1 is parachelate instead of simple. Considering that B. pravidactyla was only briefly described and that the types are lost (Lowry & Stoddart, 2003), we prefer to consider the Victorian species as new. Designation of a neotype based on topotypic material from Tasmania would better elucidate the status of B. pravidactyla .

Figures

Fig.5. Bellorchestia richardsoni n.sp., paratype male, 20.7 mm, habitus,AM P69239; holotype male, 22.3 mm, other parts,AM P69238, Point Ricardo, Victoria. Scale for habitus: 1 mm, remainder: 0.2 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.

Fig. 8. Bellorchestia richardsoni n.sp., paratype female, 21.8 mm, O2–5, AM P69240; paratype male, 22.7 mm, PL1–3 and BR2–6, AM P69239. Scales represent 0.5 mm.