Platorchestia oliveirae, 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 : 491

Platorchestia oliveirae sp. nov.

urn:lsid:zoobank.org:act:5D632C18-19DA-428F-A7FB-2DDF08C3CCBB

Figs 5–7

Orchestia platensis Kunkel, 1910: 63 , fig. 24.— Shoemaker, 1921: 101.— Shoemaker, 1933: 17.— Shoemaker, 1935: 241.— Oliveira, 1953: 329, figs. 1012.— Soares, 1979: 97.— Fox & Bynum, 1975: 228.— Heard, 1982: 42, fig. 49.— Ciavatti, 1989: 135, figs. 6–8.

Platorchestia platensis .— LeCroy et al., 2009: 963.— Gable et al., 2010: 140, appendix 1.

Orchestia monodi .— Serejo, 2004: 14, figs 7–9.— Wildish et al., 2016: 1919.

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

Not Orchestia monodi Mateus, Mateus & Afonso, 1986: 100 , figs 1–7.

Holotype: Male 9.0 mm, Caioba, Parana State, Brazil, Fritz Plauman, 06.1958, CNMC-1962-0352 . Paratypes: 65 males and females, same data as holotype, CNMC-1962-0352.1 .

Other material examined. 4 males, 4 females, Patos Island , Venezuela, under stones, HW level, Victor C. Quesnel, 1959, CNMC-1962-0421 ; 4 males, 4 females, Trinidad and Tobago, P. Wagenaar Hummelinck, 11.01.1955, CNMC-1984-0995 ; 3 males, 3 females, Fort de France, Martinique, Arthur H. Clarke, 27.03.1960, CNMC-1962-0424 ; 4 males, 4 females, Great Bay , St Maarten, P. Wagenaar Hummelinck, 24.06.1949, CNMC-1984-0977 ; 4 males, 4 females, Ocean Springs Highway , 90 Bridge, Jackson County, Mississippi, R. Moore, 08.02.1960, CNMC-1963-0076 ; 4 males, 4 females, Cedar Key , Levy County, Florida, sand beach under debris, Robert A. Menzies, 11.1959, CNMC-1963-0141 ; 4 males, 4 females Tuckers Town Cove, Bermuda, sand, plant, HW line, Eric L. Mills, 29.05.1962, CNMC-1962-0405 .

Type locality. Caioba, Parana State, Brazil.

Etymology. Named after Dr L. P. H. de Oliveira who first described material attributable to this taxon from Rio de Janeiro.

Description. Male (based on adult male holotype, 9 mm).

Head. Eyes black, medium size. Antenna 1 short, not longer than article 4 of antenna 2. Antenna 2 peduncle 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 and propodus elongate; carpus 3.5 × longer than its median width, rugose lobe narrow; propodus elongate, parallel sided, not including the palmate lobe; dactylus overlapping palm. Gnathopod 2 sexually dimorphic; subchelate; basis weakly expanded, subovate; merus without medial lobe; carpus reduced, enclosed by merus and propodus; propodus subovate, posterior margin evenly convex, palm acute, with strong V-shaped, midpalmar notch, posterodistal corner with protuberance; dactylus scythiform, overlapping posterior margin. Coxae 2–4 as wide as deep. Pereopods 3–7 cuspidactylate. Pereopod 4 shorter than pereopod 3; dactylus thickened but not pinched posteriorly, different from that of pereopod 3. Pereopod 5 propodus distinctly longer than carpus. Pereopod 6 shorter than pereopod 7, not sexually dimorphic; coxa posterior lobe with strong serrations, anteroproximal corner not produced. Pereopod 7 weakly incrassate; basis almost as broad as long, posterodistal lobe present; carpus broad, rectangular, weakly expanded; carpus:propodus length ratio = 5:6.

Pleon. Epimera 1–3 with posterior margin serrated; posteroventral corner of epimeron 2 produced into strong acute spine. Uropod 1 peduncle elongate, 1.7 × length of rami, with robust setae in two rows, distolateral robust seta absent; endopodite subequal in length to exopodite with 4 marginal inner robust setae and 3 marginal outer robust setae; endopodite without marginal setae. Uropod 2 peduncle inner margin with 7–10 robust setae, outer margin with 3 or 4 robust setae; endopodite subequal in length to exopodite; endopodite with two marginal robust setae; exopodite without marginal robust setae. Uropod 3 peduncle 1.5 × length of ramus, with 1 robust seta; ramus less than 3 × as long as broad, almost parallel-sided, with 2 or 3 marginal setae, and 3 or 4 apical setae. Telson longer than broad, apically incised, with marginal and apical robust setae; each lobe with 5 or 6 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 weakly concave anteriorly, strongly convex proximally. Pereopod 7 not incrassate.

Growth stages. The male gnathopod 2 propodus changes both its general shape and in the palm ornamentation with age. The propodus becomes less elongate and the midpalmar notch develops gradually.

Habitat. In beach debris on protected beaches and mangroves.

Remarks. Adult males of P. oliveirae sp. nov. have a much more robust pereopod 7 than do females, but only minimal incrassation of the carpus of pereopod 7 has been observed even in the largest males. A number of large males from a wide range of locations have been examined, but the possible existence of hyperadult males with a more incrassate P7 cannot be dismissed. P. oliveirae sp. nov. differs from all other Atlantic species in the structure of the male gnathopod 1 in which the carpus length is>3× breadth (length <3× breadth in P. platensis , P. exter sp. nov. and P. griffithsi sp. nov.) and, in addition, the dactylus is long, overlapping the palm whereas it is scarcely equal to or shorter than the palm in all other Atlantic species. The male gnathopod 2 has the basis anterior margin markedly convex, whereas it is nearly straight or at most weakly convex in other Atlantic species and the propodus is very subovoid due to a very convex posterior margin and develops a deep mid-palmar triangular notch in large males. No other Atlantic species has such a notch. Among Asian species. P. munmui Jo, 1988 has a small, non-triangular midpalmar notch, but that species has a weak posterodistal spine on epimeron 2, the carpus of the male gnathopod 1 is not strongly elongate, the rugose lobe broad and the posterior lobe of coxa 6 is weakly serrated (strongly serrated in P. oliveirae sp. nov.). In P. oliveirae sp. nov., coxa 6 does not have a posteroproximal knob (present in P. platensis and P. exter sp. nov.). In P. oliveirae sp. nov. there is a very strong acute spine on the posterodistal corner of epimeron 2 (short and blunt in other species except P. negevensis sp. nov., where it is subacute).

Distribution. From Brazil northwards to Bermuda. Brazil ( Oliveira, 1953; Soares, 1979; Serejo, 2004; present investigation); Venezuela (present investigation); Barbados ( Shoemaker, 1921); Trinidad and Tobago (present investigation); Martinique (present investigation); Guadeloupe ( Ciavatti, 1989; present investigation); Saint Maarten (present investigation); Dominican Republic ( Shoemaker, 1933), Puerto Rico ( Shoemaker, 1935), North Carolina ( Fox & Bynum, 1975); Mississippi (present investigation); Florida (present investigation); northern Gulf of Mexico ( Heard, 1982); Bermuda ( Gable et al., 2010; Wildish et al., 2016; present investigation).

Figures

Figure 5. Above Platorchestia exter sp. nov., male holotype (11 mm), Newfoundland; below, Platorchestia oliveirae sp. nov., male holotype (9 mm), Parana State, Brazil.

Figure 6. Platorchestia oliveirae sp. nov., male holotype (9 mm), Parana State, Brazil.

Figure 7. Platorchestia oliveirae sp. nov., male holotype (9 mm), female paratype (8 mm), Parana State, Brazil.