Chroestia Marsden & Fenwick, 1985

Lowry, James K. & Fanini, Lucia, 2023, The Coastal Talitroid Amphipods of New Caledonia (Amphipoda: Talitroidea), Records of the Australian Museum (Rec. Aust. Mus.) 75 (4), pp. 471-484 : 475-476

Chroestia Marsden & Fenwick, 1985

Chroestia Marsden & Fenwick, 1985: 843 .— Lowry & Stoddart, 2003: 271.

Type species. Chroestia lota Marsden & Fenwick, 1984 , monotypy.

Included species. Chroestia amoa sp. nov., C. lota Marsden & Fenwick, 1985 .

Category. Mascupod.

Ecological type. Beach-hoppers (mainly coastal supralittoral/intertidal leaf-litter/wrack, non-substrate modifying talitrids).

Habitat. Chroestia is common in thick mats of Zostera and mangrove debris on a small sand-gravel beach at the top of an extensive mud flat area.

Diagnostic description. Male (based on Marsden & Fenwick, 1985).

Head. Eye medium (⅕–⅓ head length). Antenna 1 short, rarely longer than peduncular article 4 of antenna 2. Antenna 2 peduncular articles slender or slightly incrassate (expanded); article 3 without plate or process ventrally. Labrum epistome without robust setae. Mandible left lacinia mobilis 4-cuspidate. Maxilliped outer margin of precoxa not stepped; palp article 2 with distomedial lobe; article 4 reduced, button shaped.

Pereon. Gnathopod 1 sexually dimorphic; subchelate; posterior margin of carpus and propodus each with lobe covered in palmate setae; palm transverse. Gnathopod 2 subchelate; propodus palm acute; posterior margin of merus, carpus, and propodus each without lobe covered in palmate setae; dactylus attenuated distally. Pereopods 3–7 bi-cuspidactylate. Pereopod 4 dactylus thickened proximally with notch midway along posterior margin. Pereopod 5 dactylus long, slender, not inflated. Pereopod 6 not sexually dimorphic; shorter than pereopod 7. Pereopods 6–7 without row of short setae along posterior margin of the dactyli. Pereopod 7 not sexually dimorphic. Propodus without large distal tuft of setae.

Pleon. Pleonites 1–3 without dorsal spines. Oostegites setae with curled tips. Pleopods1–3 all well-developed. Epimera 1–3 slits absent. Uropod 1 peduncle distolateral robust seta present (large), with simple tip; rami without apical spear-shaped setae; outer ramus without marginal robust setae; inner ramus with marginal robust setae in 1 row. Uropod 2 rami without apical spear-shaped setae; outer ramus with marginal robust setae in 1 row; inner ramus with marginal robust setae in 1 row. Uropod 3 ramus shorter than peduncle. Telson longer than broad, tapering distally, apically incised, with marginal and apical robust setae, with 7 to 10 or more robust setae per lobe.

Remarks. Chroestia is confined to Australia and New Caledonia which separated from each other about 65 million years ago ( Coleman, 1980) and may indicate a possible minimal age for Chroestia , but also shows the morphological stability of species within the genus.

Distribution. Australia: Lota, Queensland ( Marsden & Fenwick, 1985). New Caledonia: Malabou andAmoa, Grand Terre (this paper).