Regadrella okinoseana Ijima 1896

• Main Authors: Reiswig, Henry M., Stone, Robert P.
• Format: Other/Unknown Material
• Language: unknown
• Published: 2013
• Subjects: Biodiversity; Taxonomy; Animalia; Porifera; Hexactinellida; Lyssacinosida; Euplectellidae; Regadrella; Regadrella okinoseana; Amchitka; Amchitka Pass; Alaska; Aleutian Islands
• Online Access: https://zenodo.org/record/5261624; https://doi.org/10.5281/zenodo.5261624

Regadrella okinoseana Ijima, 1896 (Figs. 12 & 13, Table 6) Synonymy: Regadrella okinoseana Ijima, 1896: 250; 1901: 223; Levi & Levi 1982: 292; Reiswig 1992: 33; Stone et al., 2011: 25. Regadrella cylindrica Ijima, 1927: 335. Regadrella decora Schulze, 1900: 30. Material examined. USNM# 1196553, ROV 'Jason II' from RV 'Roger Revelle', dive J2102, 03 August 2004, S Amchitka Pass, 27.4 km W of Amatignak Island, Delarof Islands, Aleutian Islands, Alaska, 51º17.469'N, 179º32.585'W, 1386 m, partial specimen, dry & ethanol. Description. The single specimen from the Aleutian Islands is a soft flattened sac with a wide but subdivided oscular aperture (Fig. 12A); dimensions of the specimen lacking the attachment base (not collected) are 18.8 cm tall, 12.8 cm wide, 9.1 cm thick. The body wall is 3–4 mm thick. Prostalia are not present. The characteristic Regadrella surface pattern of pits and ridges with small parietal oscula at the center of pits (Table 6) is developed only on the external body edges that remain free of contact with the surrounding substrate (Figs. 12 B, C). The larger frontal surfaces that contact the substratum lack this pattern but still have parietal oscula scattered irregularly across their surface. Parietal oscula are ovoid with mean major diameter of 2.6 mm (Fig. 12D). The main oscular edge is curled outward (Fig. 12A) but a cuff and sieve plate are absent. Within the single oscular margin, the distal atrial cavity is subdivided into four separate passages by tissue bridges joining the atrial wall surfaces. One of these bridges extends longitudinally at least half the length of the body, thereby flattening and subdividing the distal atrial cavity into two main passages. In the lower half of the saccate body, the two longitudinal atrial passages join to form a single open atrial cavity. Before collection, the specimen was attached under the edge of a large mudstone mound with the osculum exposed (Fig. 12E). Color in life was white; dried and ethanol-preserved samples are light beige. The ...