Insularorchestia ashmoleorum ( Stock, 1996 ) Lowry & Myers, 2022

Lowry, J. K. & Myers, A. A., 2022, Platorchestiinae subfam. nov. (Amphipoda, Senticaudata, Talitridae) with the description of three new genera and four new species, Zootaxa 5100 (1), pp. 1-53 : 19

Insularorchestia ashmoleorum ( Stock, 1996) comb. nov.

( Fig. 10 )

Platorchestia ashmoleorum Stock, 1996: 151 , figs 1, 2–4 (in part).— Miyamoto & Morino, 2004: 69, 88.— Serejo, 2004: 20, table 2.— Lowry, 2012: 14, (key).

Non-Taxonomic Citations

Platorchestia ashmoleorum .— Wildish & Radulovici, 2019: 2418, table 2, (zoogeography).

Types. Holotype, male, 9.2 mm, ZMA . Paratypes: female, 8.5 mm, ZMA; 4 males, 5 females ZMA; 10 males, 10 females ZMA; 1 male, 4 females ZMA; 1 males, 1 female ZMA; 1 male, 4 females ZMA .

Type locality. Broad Gut , near junction with Gates of Chaos , St Helena Island, South Atlantic Ocean (50°59’59.84’’S 5°44’00.07’’W) .

Ecological type. Land-hopper, often near freshwater streams.

Habitat. Semi-terrestrial. Freshwater streams. According to Stock, (1996) Insularorchestia ashmoleorum ‘has been encountered only along small guts (=streams) in the dry and hot lowland zone (altitudes 1–40 m) and close to the sea (at 300–750 m in direct line). The gut water in these areas is often slightly salty, not so much through marine influence, as by salts dissolved after rains from the volcanic rocks and sediments. The two talitrid species were never found together’.

Size. Male, 9.2–10 mm, female, 8.5 mm.

Diagnosis (male). Based on Stock (1996).

Gnathopod 1 simplidactylate. Gnathopod 2 propodus palm evenly rounded, without proximal sinus; dactylus short, recurved distally with slight posterior projection near dactylar hinge. Pereopod 7 not incrassate; propodus broad; length 6.6 × width. Uropod 1 endopod with marginal robust setae in 2 rows.

Remarks. Insularorchestia ashmoleorum exhibits a homoplasy with Platorchestia ano in which the distal end of the gnathopod 2 dactylus is distinctively shortened and recurved. The simplidactylate dactylus on male gnathopod 1 distinguishes it from these species.

Like Morinoia , I. ashmoleorum has no sexual dimorphism in P7, but Morinoia does not have an incrassate A2.

Distribution. South Atlantic Ocean. St. Helena ( Stock 1996).

Figures

FIGURE 10. Insularorchestia ashmoleorum (Stock, 1996), after Stock, 1996.