Chroestia Marsden & Fenwick 1985
Creators: name: Lowry, James K.
name: Fanini, Lucia
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Amphipoda
Talitridae
Chroestia

description: 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).
description: Published as part of Lowry, James K. & Fanini, Lucia, 2023, The Coastal Talitroid Amphipods of New Caledonia (Amphipoda: Talitroidea), pp. 471-484 in Records of the Australian Museum (Rec. Aust. Mus.) (Rec. Aust. Mus.) 75 (4) on pages 475-476, DOI: 10.3853/j.2201-4349.75.2023.1886, http://zenodo.org/record/10413723