Platorchestia platensis ( Krøyer, 1845 )

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 : 486-490

Platorchestia platensis ( Krøyer, 1845)

Figs 1–4

Orchestia platensis Krøyer, 1845: 304 , pl. 2, fig. 2a–i.— Stebbing, 1888: 210.— Spandl, 1924: 462.— Chevreux & Fage, 1925: 276, fig. 287.—Dahl, 1946: 11.— Karlbrink, 1969: 327.— Karaman, 1971, 12, figs 3-4.— Geldiay et al., 1971: 369.— Lincoln, 1979: 220, fig. 101, a–h.— Teigsmark, 1981: 165.— Bellan-Santini, 1993: 749, fig. 514.— Stefanidou & Voultsiadou-Koukoura, 1995: 603, tab. 1.— Holmes et al., 1997: 186.— Gönlügür-Demirci, 2006: 1133.

Orchestia incisimana Chevreux, 1888: 347 , pl. 6 figs 1, 2.

Orchestia gammarellus .— Della Valle, 1893: 499 (in part).

Platorchestia platensis . — Jo, 1988: 166, fig. 8.— Köhn & Gosselck, 1989: 61, fig. 19, 3.— Krapp-Schickel & Zavodnik, 1996: 461.— Miyamoto & Morino, 2004: 81, fig. 7.— Serejo, 2004: 19, fig. 10.— Ruffo & Krapp-Schickel, 2005: 36.— Sezgin & Katağan, 2007: 5, tab. 1.— Serejo & Lowry, 2008: 194 , figs 25, 26.— Christodoulou et al., 2013: 12, tab. 2.— Zakhama-Sraieb et al., 2017: 498 (checklist).— Zettler & Zettler, 2017: 345, figs 243–244.— Copilaş-Ciocianu et al., 2020: 461, 462, fig. 1, 2.

Not Orchestia platensis .— Spence Bate, 1862: 19, pl. 3, fig. 3 [ =? Orchestia ].— Shoemaker, 1921: 101.— Shoemaker, 1933: 17.— Shoemaker, 1935: 241 (= P. oliveirae sp. nov.).— Iwasa, 1939: 257, figs 1–3, pl. 9 (= P. joi Stock & Biernbaum, 1994 ).— Stephensen, 1945: 57, figs 15–16 (= P. joi Stock & Biernbaum, 1994 ).— Gurjanova, 1951: 807, fig. 562 (= P. joi Stock & Biernbaum, 1994 ).—Oliveira. 1953: 329, figs. 1012 (= P. oliveirae sp. nov.).— Bulycheva, 1957: 159, figs 57a–b (= P. joi Stock & Biernbaum, 1994 ).— Bousfield, 1973, 159, fig. 46.2 (= P. exter sp. nov.).— Morino, 1975: 172, figs 1–3 (= P. joi Stock & Biernbaum, 1994 ).— Griffiths, 1975, 79, fig. 52B (= P. griffithsi sp. nov. — Fox & Bynum, 1975: 228 (= P. oliveirae sp. nov.). — Soares, 1979: 97 (= P. oliveirae sp. nov.).— Heard, 1982: 42, fig. 49 (= P. oliveirae sp. nov.).— Ciavatti, 1989: 135, figs. 6–8 (= P. oliveirae sp. nov.).— Diemer, 2016, 207, figs. 4, 6 (= P. griffithsi sp. nov.).— Herbst & Dimentman, 1983: 20, fig. 3 (= P. negevensis sp. nov.).

Not Platorchestia platensis . — Myers, 1985: 134, figs 108, 109 (= sp. nov.).— Morino & Ortal, 1995: 829, fig. 4 (not identifiable to any known species).

Lectotype: Male, 12.3 mm, ZMUC CRU 8221 (selected by Serejo, 2004) . Paralectotypes: 1 male, 6.8 mm; 1 female, 7.6 mm, 7 damaged specimens, Montevideo, 13/12/40, ZMUC 7803 .

Other material examined. 4 males and 4 females, Bornova , Izmir, Turkey, Aegean Sea, Ahmet Koçatas, 22.05.1976, CNMC 1982-0358 ; 4 males 1 female Warnow Estuary , northern Breiting , Rostock / Hohe Dune, Baltic Sea, 07.05.1998, M. L. Zettler ; 4 males, 4 females, Gulf of Guinea, Port Harcourt, Creek Market , Nigeria, 23.10.1997, S. Reino Freeman, CMNC 1982-0359 ; 4 males, 4 females, Ceuta, Morocco, 36°04'N 05°36'W, 03.08.1960, Richard J. Vockeroth, CMNC1982-0357 .

Type locality. Rio de la Plata, Montevideo, Uruguay.

Description. Male (based on adult male, 14 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 of moderate length, about two-and-a-half × as long as its broadest width and about one and one quarter length of propodus, rugose lobe broad; propodus palm transverse; dactylus weakly overlapping palm, cuspidactylate. Gnathopod 2 sexually dimorphic; subchelate; basis weakly expanded, subrectangular; merus without medial lobe; carpus reduced, enclosed by merus and propodus; propodus posterior margin nearly straight, palm acute, with sinuous margin and 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 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 and posteroproximal corner extended into a distinct lobe. Pereopod 7 sexually dimorphic; basis almost as broad as long, posterodistal lobe present; carpus elongate suboval, length 1.6 × breadth, anterior margin weakly crenulate; carpus: propodus length ratio = 5:6.

Pleon. Epimera 1–3 with posterior margin slightly scalloped; posteroventral corner of epimera 2–3 moderately produced, subacute. Uropod 1 peduncle 1.5 × length of rami, with robust setae in two rows, distolateral robust seta weak; endopod subequal in length to exopod and with 3 marginal inner robust setae and 4 marginal outer robust setae; endopod without marginal robust setae. Uropod 2 peduncle inner margin with about 5 robust setae and outer margin with 3 robust setae; inner ramus subequal in length to exopodite; endopodite with 2 marginal inner robust setae, exopodite with 2 marginal robust setae. Uropod 3 peduncle 1.5 × length of ramus, with 2 or 3 robust setae; ramus stout, less than 3 × longer than broad, with 0-2 marginal setae, and 3 or 4 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 without rugose lobes on carpus and propodus. Gnathopod 2 mitten-shaped; basis anterior margin strongly convex proximally, weakly concave anteriorly. Pereopod 7 carpus slender.

Remarks. Platorchestia platensis shares the presence of a knob-like extension on the posteroproximal margin of coxa 6. with P. exter sp. nov. and probably with P. negevensis sp. nov., (unconfirmed) among Atlantic species and P. pacifica Miyamoto & Morino, 2004 and P. paraplatensis Serejo & Lowry, 2008 elsewhere. The knob is absent in the Atlantic species P. oliveirae sp. nov. and P. griffithsi sp. nov., and is also absent in the non-Atlantic species, P. ano Lowry & Bopiah, 2013 , P. smithi Lowry, 2012 , P. munmui Jo, 1988 and P. pachypus Derzhavin, 1937 . Platorchestia platensis differs from P. exter sp. nov. in the length of the propodus on the male gnathopod 1 that is about two-thirds as long as broad (almost as broad as long in P. exter sp. nov.) and in the ramus of uropod 3 being about 2× as long as broad (about 3× as long as broad in P. exter sp. nov.). It differs from all other Atlantic species by the nearly straight posterior margin of the propodus of the male gnathopod 2 (convex in other species). It differs from P. negevensis sp. nov. in the incrassation of the male pereopod 7 (unexpanded in P. negevensis sp. nov.) and in the dactylus of gnathopod 1 being almost equal in length to the palm (significantly shorter than the palm in P. negevensis sp. nov.). It differs from P. griffithsi sp. nov. in the presence of the aforementioned knob-like process on the posteroproximal margin of coxa 6 (absent in P. griffithsi sp. nov.), in the nearly straight posterior margin of the propodus of the male gnathopod 2 (convex in P. griffithsi sp. nov.) and in the much shorter propodus of the male pereopod 7. For the several differences between P. platensis and P. oliveirae , see under the remarks for P. oliveirae .

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

Distribution. South America: La Plata, Uruguay ( Krøyer, 1845); Mediterranean: Marseille ( Bellan-Santini, 1993), Monaco, Minorca, Naples, Algeria, Egypt, Palestine ( Chevreux & Fage, 1925); Montenegro, Boka Kotorska ( Karaman, 1971); Turkey ( Geldiay et al., 1971; present investigation); Black Sea ( Copilaş-Ciocianu et al., 2020); Africa: Morroco (present investigation); Nigeria (present investigation); England ( Lincoln, 1979); Baltic: Denmark ( Jo, 1988), Germany ( Zettler & Zettler, 2017; present investigation).

Figures

Figure 1. Platorchestia platensis (Krøyer, 1845), male (14 mm), Bornova, Turkey.

Figure 2. Platorchestia platensis(Krøyer, 1845), male paralectotype (12 mm), Montevideo, Uruguay (After Serejo, 2004, except uropods 1–2 from SEM).

Figure 3. Platorchestia platensis (Krøyer, 1845), male (14 mm), Bornova, Turkey.

Figure 4. Platorchestia platensis (Krøyer, 1845), male (14 mm), female (12 mm), Bornova, Turkey.