Ascetoaxinus quatsinoensis Oliver & Frey 2014, sp. nov.
Creators: name: Oliver, P. Graham
name: Frey, Melissa A.
Publisher: name: Zenodo
Year: 2014
Subjects: Biodiversity
Taxonomy
Animalia
Mollusca
Bivalvia
Lucinida
Thyasiridae
Ascetoaxinus
Ascetoaxinus quatsinoensis

description: Ascetoaxinus quatsinoensis sp. nov.
Figs. 2–6
Type material. Holotype, single specimen, off Quatsino Sound, Vancouver Island, British Columbia, Canada, 50°15.482´N, 128°26.400´W to 50°14.519´N, 128°26.567´W, 1086–1318m. Coll. J. Boutillier, Fisheries and Oceans Canada, 02 September 2004. RBCM 010-00221 - 005.
Measurements.
Description. Shell (Fig. 2). 31.3mm in length. Thin, brittle. Equivalve. Moderately tumid. Strongly inequilateral, prosogyrous beaks close to the anterior margin. Outline obliquely oval; anterior margin almost straight bounding a large excavated lunule; ventral margin long, almost straight; posterior margin broad, sulcate with a distinct posterior dorsal sinus. Posterior sulcus sharply defined, relatively narrow; submarginal sulcus sharply defining a flattened escutcheon. Posterior ventral slope anterior of the posterior sulcus a little flattened, creating a weak secondary ridge. Hinge teeth lacking, ligament partially sunken, relatively short being less than half the length of the escutcheon. Sculpture of well-defined growth lines; edge of lunule drawn out into five rounded projections. Muscle scars indistinct; anterior adductor scar elongate and parallel with ventral margin. Shell colour white.
Anatomy (Figs. 3–6). Mantle is thin; unfused except for the formation of a small exhalant aperture (Fig. 3, ex). Anterior adductor scar elongate and approximately 4 times longer than posterior adductor scar; free from mantle edge for about one-fifth of its ventral edge; posterior adductor muscle oval. Foot vermiform (Fig. 3), very long, tip not noticeably expanded, heel obsolete, protractor muscles very slender. Labial palps small, narrow with a distinctly grooved dorsal zone and a long tubular portion leading to the mouth (Fig. 5A, B). Alimentary system (Fig. 4) with short oesophagus leading to a relatively small stomach; large digestive ducts leading to the lateral body pouches open into the ventral anterior face (Fig. 5D, dd, np), smaller ducts open dorsally on the left side and lead to a pair of outgrowths (Fig. 5B, dg); walls of the combined style sac and mid gut thickened (Fig. 5D, ss/mg), remainder of mid gut coiling back over style sac, passing through heart and coiling towards the posterior as the hind gut; anus opening into exhalant aperture (Fig. 4). Lateral body pouches large, arborescent, terminations cloven or single, blunt (Fig. 5C). Kidney large and packed with golden coloured granules. Ctenidium large, both demibranchs with fully reflected filaments; outer demibranch about half the depth of the inner demibranch (Fig. 3, od, id). Filaments laminar (Fig. 6A, C), frontal zone narrow, abfrontal zone extended and fused across the ascending and descending arms, creating junctions between the ascending and descending lamellae (Fig. 6A, abs). Ventrally every filament is fused. The frontal surface (Fig. 6B) is ciliated with distinct lateral cilia (lc) and laterofrontal cirri (lfc); frontal cilia not apparent, instead adjacent frontal zone appears wide and smooth (sfz). Abfrontal surfaces lined with bacteriocytes that are domed and roundly polygonal with a glycocalyx (Fig. 6C, bc). Bacilli bacteria also present in defined bundles, measuring 1.1 um in length (Fig. 6D, bct).
description: Published as part of Oliver, P. Graham & Frey, Melissa A., 2014, Ascetoaxinus quatsinoensis sp. et gen. nov. (Bivalvia: Thyasiroidea) from Vancouver Island, with notes on Conchocele Gabb, 1866, and Channelaxinus Valentich-Scott & Coan, 2012, pp. 452-468 in Zootaxa 3869 (4) on pages 455-456, DOI: 10.11646/zootaxa.3869.4.8, http://zenodo.org/record/4947378