Orchestia Leach, 1814

Lowry, J. K. & Fanini, Lucia, 2013, Substrate dependent talitrid amphipods from fragmented beaches on the north coast of Crete (Crustacea, Amphipoda, Talitridae), including a redefinition of the genus Orchestia and descriptions of Orchestia xylino sp. nov. and Cryptorchestia gen. nov., Zootaxa 3709 (3), pp. 201-229 : 205-207

Orchestia Leach, 1814

Orchestia .— Leach, 1814: 402.— Stebbing, 1888: 602, 1678.— Sars, G.O., 1890: 24.— Della Valle, 1893: 494.— Stebbing, 1906: 530.— Chevreux & Fage, 1925: 272.— Shoemaker, 1942: 17.—Hurley, 1956: 149 (in part).— Bousfield & Holthuis, 1969: 105, 110.— J.L. Barnard, 1969: 470 (in part).— Lincoln, 1979: 212 (in part).— Bousfield, 1982: 22.— Bellan-Santini, 1993: 742. Scamballa (part.) White, 1847: 86.

Type species. Oniscus gammarellus Pallas, 1776 , monotypy.

Diagnostic description (based on male). Eyes present. Antenna 1 short, not longer than article 4 of antenna 2 peduncle. Antenna 2 peduncular articles slender or slightly incrassate; peduncular article 3 without ventral process. Labrum without robust setae. Mandible left lacinia mobilis 4-dentate or 5-dentate. Maxilliped palp article 2 distomedial lobe well developed; article 4 reduced, button-shaped. Gnathopod 1 subchelate; posterior margin of carpus and propodus each with lobe covered in palmate setae. Gnathopod 2 subchelate; merus and carpus free; dactylus slender distally. Pereopods 3–7 cuspidactylate. Pereopods 5–7 without setae along posterior margin of the dactylus. Pereopods 6 sexually dimorphic (merus/carpus slightly incrassate) or not, pereopod 7 sexually dimorphic (merus and carpus slightly to strongly incrassate) or not, both without row of short setae along posterior margin of dactyli. Pleonites 1–3 without dorsal spines. Pleopods 1–3 biramous, well developed. Epimera without vertical slits. Uropod 1 outer ramus slender; with marginal robust setae. Uropod 3 well developed; ramus shorter than or subequal in length to peduncle. Telson incised, with 7+ robust setae per lobe.

Included species (15 species). Orchestia aestuarensis Wildish, 1987 ; O. aucklandiae Bate, 1862 ; O. bollonsi Chilton, 1909 ; O. chathamensis (Hurley, 1956) ; O. bottae Milne Edwards, 1840 (dubious); O. dentata Filhol, 1885 ; O. gammarellus (Pallas, 1776) ; O. grillus ( Bosc, 1802) ; O. magnifica ( Vecchi, 1931) ; O. mediterranea A. Costa, 1853 ; O. microphtalma Amanieu & Salvat, 1963 ; O. montagui Audouin, 1826 ; O. stephenseni Cecchini, 1928 ; O. telluris Bate, 1862 ; O. xylino sp. nov.

Remarks. There are a number of taxa assigned to Orchestia which apparently do not fit comfortably in the genus. In the North Atlantic/Mediterranean area the species known as Orchestia sulensoni Stebbing, 1899 was originally recorded from Madeira with no other reported information on locality or habitat. Based on Stebbing’s illustrations the male has an incrassate second antenna, palmate lobes on the carpus and propodus of gnathopod 1, a non-sexually dimorphic pereopod 7, no robust setae on the outer ramus of uropod 1 and a short ramus on uropod 3, all of which indicate that it belongs in Platorchestia (group 2) of Morino & Miyamoto (1988).

Orchestia magnifica Vecchi, 1931 , the enigmatic terrestrial species from the Jalo oasis in the Libyan desert, was considered to be a junior synonym of O. mediterranea by Bellan-Santini (1993). They look similar but O. magnifica has about five robust setae on the margin of the uropod 3 ramus (naked in O. mediterranea ). Although not completely described, O. magnifica has the diagnostic characters of Orchestia and we reinstate it here. The species has not been reported since its original description.

There is a group of generally inadequately described species from the South Pacific islands that includes Orchestia aucklandiae Bate, 1862 , O. bollonsi Chilton, 1909 , O. chathamensis (Hurley, 1956) , O. dentata Filhol, 1885 and O. telluris Bate, 1862 from supralittoral beaches in New Zealand and four terrestrial species: Orchestia gambierensis Chevreux, 1908 (Society Islands); Orchestia kokuboi Uéno, 1929 ( Japan) ; Orchestia marquesana Stephensen, 1935 (Society Islands); and Orchestia ponapensis J.L. Barnard, 1960 ( Micronesia) .

Orchestia aucklandiae , O. bollonsi , O. chathamensis , O. dentata and O. telluris form a group of New Zealand supralittoral species that do not separate from the Orchestia concept based on the following male characters: antenna 1 shorter than peduncular article 4; antenna 2 slender; maxilliped palp article 4 reduced, gnathopod 1 subchelate, posterior margin of carpus and propodus with palmate lobes; gnathopod 2 subchelate, dactylus not modified distally; pereopod 7 sexually dimorphic; uropod 1 outer ramus with marginal robust seta and telson with at least 10 robust setae.

‘ Orchestia ’ gambierensis appears to fit in the genus Traskorchestia based on the male characters: gnathopod 1 subchelate, posterior margin of merus, carpus and propodus with palmate lobes; gnathopod 2 subchelate, pereopod 7 not sexually dimorphic; uropod 1 outer ramus with marginal robust seta and telson with at least 10 robust setae. It is difficult to know what species ‘ Orchestia ’ kokuboi fits. It is a terrestrial species with well developed pleopods. Uéno (1929) illustrated a male, but it is difficult to know if the fourth article of the maxillipedal palp is present, if the merus of male gnathopod 1 has a palmate lobe, the distal condition of the dactylus and how many robust setae on the telson. Iwasa (1939) illustrated a female. These specimens have palmate lobes on the merus, carpus and propodus of gnathopod 1 and seven robust setae on each lobe of the telson. Based on the combination and assuming that gnathopod one is the same in both sexes, then this taxon might be in the genus Paciforchestia Bousfield, 1982 .

‘ Orchestia ’ marquesana is a terrestrial species only known from an adult female. Based on: maxilliped palp article 4 reduced and button-shaped; gnathopod 1 parachelate without palmate lobes; gnathopod 2 mitten-shaped; pleopods all reduced and all biramous; uropod 1 outer ramus without marginal robust setae; and telson with 3 robust setae per lobe this taxon might be a species of Talitriator Methuen, 1913 . The species described and illustrated by Shoemaker (1942) does not appear to be that species.

It is difficult to conceive the New Zealand outliers as part of the North Atlantic/Mediterranean genus Orchestia . The genus would have to be Pangaean in age. But morphologically the species appear to be inseparable at generic level and so, at least for now, we retain the New Zealand species in Orchestia . It would be interesting to see how a DNA analysis would arrange them.

Without a phylogenetic analysis it is difficult to know what genera Orchestia might be aligned with. Using obvious characters such as uropod 1 outer ramus with marginal robust seta, male gnathopod 1 subchelate with palmate lobes on the merus and carpus, pleopods well developed, and maxilliped palp article 4 reduced, buttonshaped, then it appears to be similar to Americorchestia Bousfield, 1991 , Australorchestia Serejo & Lowry, 2008 and Tongorchestia Lowry & Bopiah, 2013 . If the densely setose telson is considered then Orchestia appears to be most similar to the recently described South Pacific genus Tongorchestia . If true then maybe the Orchestia model was functioning when Pangaea split and it descendants are widespread today thru the South Pacific, the Americas and Europe.