Discorhabdella atypica n. sp.

urn:lsid:zoobank.org:act: 9C09DEC7-22EE-458A-B2C6-E15BE31B3CD7

Figure 9

Diagnosis. Thin encrusting, skeletal architecture and spicules typical of the genus except the possession of regular acanthostyles rather than pseudastros ones.

Etymology The species name refers to the atypical (for the genus) acanthostyles.

Material Examined Holotype RBCM 024-00008 - 002, Stn NM 405, Defence Isl, Howe Sd, BC, 49° 34.511’ N / 123° 16.425’ W, coll. N. McDaniel, 14 Dec 2019, 15 m depth, 1 specimen . Paratypes RBCM 018-00171 - 001, Stn NM 257, Defence Isl, Howe Sd ., BC, 49° 34.544’ N 123° 16.632’ W, coll. N. McDaniel, D. Swanston, 19 May 2011, 9 m depth, 1 specimen; RBCM 024-00010 - 003, Stn NM 395, Defence Isl (E), Howe Sd ., BC, 49° 34.511’ N / 123° 16.425’ W, coll. N. McDaniel, 24 Sept 2019, 15 m depth, 1 specimen; RBCM 024-00008 - 003, Stn NM 406, Defence Isl, Howe Sd ., BC, 49° 34.511’ N / 123° 16.425’ W, coll. N. McDaniel, 14 Dec 2019, 15 m depth, 1 specimen, RBCM 018-00392 - 001, Stn KML 20/76, Jervis Inlet, 49° 56.6’ N / 123° 58.7’ W, coll. W. Austin, 15 Mar 1976, “shallow”, 1 specimen .

Description

External (Figure 9A) Holotype RBCM 024-00008-002. Sponge encrusting approximately 6 cm diameter x 1.5 mm thick. Subdermal radial canals leading to oscula usually visible in living specimens. Ostia not visible in the in-situ photographs or in preserved specimens. Ostia densely scattered, 0.45–0.9 mm diameter. Surface smooth, microhispid; spicules protrude up to 100 µm. Colour in life bright orange, varying occasionally to scarlet red. Consistency easily torn.

Skeleton (Figure 9B) Skeleton is hymedesmioid with acanthostyles anchored in the spongin base, heads down. Subtylostyles form a dense palisade in the ectosome in places separated from the base with large aquiferous canals or continuing to the base in multispicular tracts as part of the choanosome. Tylostyles are spaced randomly among the subtylostyles. Subtylostyles project beyond the surface 50 µm; tylostyles project 80 to 150 µm. Microscleres are located below the surface scattered throughout the sponge.

Spicules (Figures 9C, D, E, F, G and H) Subtylostyles, tylostyles, acanthostyles, anchorate unguiferous isochelas and sigmas. Subtylostyles (Figures 9C, D) straight, slightly fusiform, oval heads variably thick (may be subterminal), hastate sharp apices, some slightly mucronate, dimension range 137–515 x 7.8–19.5 µm. Tylostyles (Figure 9E): straight or slightly curved tapering uniformly to a rounded apex. Head formed by a crown of rounded protuberances which may be slightly subterminal, dimension range 452– 1620 x 20.8–104 µm. Acanthostyles (Figure 9F) large spined head, spines may be concentrated in two whorls, one sub-apical and one median (not shown); alternately more or less continuous along the shaft (Figure 9F), or unspined for the pointed ¼ of the shaft; heads broad with small spines pointing vertically on top, larger and horizontally on sides and slightly downward toward the apex on the underside of the head, dimension range 65.0–148 x 20.8–72.8 µm. Anchorate unguiferous multidentate isochelas (Figure 9G) shallow curve, short narrow alae (1/4 chord length or less), dimension range 13.0–28.6 µm. Sigmas (Figure 9H) simple or contort, dimension range 10.4–20.8 µm. Trichodragmas of microxeas (not microrhabds) rarely present, may be foreign. There is no evidence of spines on the SEMs of microxeas which are typical for the genus (Van Soest 2002 [2004]c). Table 8 compares spicule dimensions of specimens examined.

Distribution. All specimens obtained were from Howe Sd, BC; 9–15 m depth.

Ecology Forms thin encrustations on bedrock and barnacles, up to 20 cm in diameter.

Remarks The BC species of Discorhabdella lacks pseudastrose acanthostyles with subapical spined whorls characteristic of other Discorhabdella species except D. tuberosocapitata (Topsent, 1890) which has club-shaped acanthostyles based on Topsent’s figure (Topsent, 1892, p. 113, pl. XI, f. 6; Hooper, 1996, p. 36, f. 12E–G; Van Soest, 2002 [2004]c, p. 552, f. 2C) and two species from Japan: D. hispida Ise, Vacelet, Izumi, Woo & Tan, 2021 and D. misakiensis Ise, Vacelet, Izumi, Woo & Tan, 2021 . Discorhabdella tuberosocapitata ’s skeletal architecture differs from D. atypica n. sp. in having the large tuberose tylostyles surrounded at the surface by tuberose acanthostyles rather than the subtylostyles in D. atypica n. sp. (Van Soest, 2002 [2004]c,). Both Japanese species are thin encrusting. D. misakiensis lacks sigmas. Discorhabdella hispida is similar to our specimen but has a more pronounced hispid surface, is greenish in colour and lacks the subdermal radial canals of D. atypica n. sp.; as well D. hispida sigmas are a complex S-shape closer to that of flagellosigmas and unlike the simple C-sigmas of D. atypica n. sp. Topsent’s species and both Japanese species were from deep water (550–736 m and 113–318 m, respectively). Discorhabdella atypica n. sp. is a range extension of the genus from Panama in the Northeast Pacific and a depth extension from 55 m up to 9 m depth.