Platorchestia griffithsi, Myers & Lowry, 2023

Myers, Alan A. & Lowry, James K., 2023, The Beach-hopper Genus Platorchestia (Crustacea: Amphipoda: Talitridae) on Atlantic Ocean Coasts and on those of Associated Seas, Records of the Australian Museum (Rec. Aust. Mus.) 75 (4), pp. 485-505 : 500

Platorchestia griffithsi sp. nov.

urn:lsid:zoobank.org:act:83104A65-B8AB-4CB0-BFB1-B76881BC2665

Figs 10 , 12 , 13

Orchestia platensis .— Griffiths, 1975: 79, fig. 52B.

? Orchestia platensis .— Macnae, 1953: 1027.

Platorchestia platensis .— Mead et al., 2011: 1998, tab. 1.— Milne & Griffiths, 2013: 77.— Diemer, 2015: 15, 24, 35.— Diemer et al., 2016: 207, figs 4–6.

Not Orchestia platensis Krøyer, 1845: 304 , pl. 2 figs 2a–i.

Holotype: Male, Knysna lagoon, South Africa, University of Cape Town , 04.15.1949, CMNC-1982-0356 . Paratypes: 4 males, 4 females, same data as holotype, CMNC-1982-0356.1 .

Type locality. Knysna lagoon, South Africa

Etymology. Named after Charles Griffiths in recognition of his important work in documenting the amphipod fauna of South Africa.

Description. Adult male 9 mm.

Head. Eyes black, medium size. Antenna 1 short, not longer than article 4 of antenna 2. Antenna 2 peduncle strongly incrassate; article 5 longer than 4; peduncular articles with sparse, small robust setae.

Pereon. Gnathopod 1 subchelate; posterior margin of carpus and propodus with rugose lobe; carpus moderately elongate, about 2.5 × as long as its broadest width and over one- and one-half length of propodus; propodus palm transverse; dactylus much shorter than palm, cuspidactylate. Gnathopod 2 sexually dimorphic; subchelate; basis weakly expanded, subrectangular; merus without medial lobe; carpus reduced, enclosed by merus and propodus; propodus subovate, posterior margin evenly convex; palm acute, with subdistal notch, posterodistal corner with protuberance; dactylus scythiform, overlapping posterior margin. Coxae 2–4 as wide as deep. Pereopods 3–7 cuspidactylate. Pereopod 4 significantly shorter than pereopod 3; dactylus thickened weakly pinched posteriorly, different from that of pereopod 3. Pereopod 5 propodus distinctly longer than carpus. Pereopod 6 not sexually dimorphic, shorter than pereopod 7; coxa posterior lobe with weak serrations, posteroproximal corner not extended into a distinct lobe. Pereopod 7 sexually dimorphic; basis almost as broad as long, posterodistal lobe present; carpus subovoid, anterior margin crenulate; carpus: propodus length ratio = 5:7.

Pleon. Epimera 1–3 with posterior margin slightly serrated; epimeron 3 posteroventral corner with weak spine. Uropod 1 peduncle 1.3× length of rami, with robust setae in two rows, distolateral robust seta absent; endopodite subequal in length to exopodite and with 4 marginal inner setae and 2 marginal outer setae; endopodite without marginal setae. Uropod 2 peduncle inner margin with 5–7 setae and outer margin with 2 or 3 setae; endopodite subequal in length to exopodite; endopodite with one row of marginal robust setae; exopodite with 1 marginal seta. Uropod 3 peduncle 1.3 × length of ramus, with 3 robust setae; ramus narrowing distally; with 1 marginal seta, and 3 apical setae. Telson longer than broad, apically incised, with marginal and apical robust setae; each lobe with 3–5 robust setae.

Female. (sexually dimorphic characters). Antennae 2 slender, not incrassate. Gnathopod 1 carpus and propodus without rugose lobes. Gnathopod 2 mitten-shaped; basis anterior margin strongly convex proximally, anteriorly nearly straight; carpus and propodus very slender, almost 3× as long as broad. Pereopod 7 not incrassate.

Remarks. Platorchestia griffithsi sp. nov. differs from P. platensis and P. exter sp. nov. in lacking a knob-like projection on coxa 6 and in the shape of the male gnathopod 2 propodus, which has a distinctly convex posterior margin (nearly straight in P. platensis ). It differs from all other described species in the very long propodus on the male pereopod 7. In the female, Platorchestia griffithsi has a very elongate and slender gnathopod 2 carpus and propodus compared with other species. It differs from P. oliveirae sp. nov. and P. negevensis sp. nov. in the crenulate anterior margin of the carpus in the hyperadult male pereopod 7.

Habitat. In beach debris on high shore of protected beaches.

Distribution. South Africa from Langebaan Lagoon in the Western Cape to Swartkops Estuary in the Eastern Cape.

Figures

Figure 10. Above Platorchestia griffithsi sp. nov., male holotype (9 mm), Knysna lagoon, South Africa; below P. negevensis sp. nov., male (9.5 mm), Negev desert (after Morino & Ortal, 1995).

Figure 12. Platorchestia griffithsi sp. nov., male holotype (9 mm), Knysna lagoon, South Africa.

Figure 13. Platorchestia griffithsi sp. nov., male holotype (9 mm), female paratype (8 mm), Knysna lagoon, South Africa.