Abyssocladia annae Ekins & Erpenbeck & Hooper 2020, sp. nov.

Abyssocladia annae sp. nov.

Figure 4, Table 1

urn:lsid:zoobank.org:act: E572DF22-EF0F-406D-B053-C20C0A5F84EA

Material Examined: Holotype: QM G337611, off the continental shelf of central New South Wales, Australia, Station 88, 30° 15’ 50.4”– 30° 17’ 12.2” S, 153° 52’ 12”– 153° 49’ 48.7” E, 4481– 4401 m, Beam Trawl, Coll. Merrick Ekins on RV Investigator, Cruise IN2017_ V03, Sample 88–141.1 6/vi/2017.

Etymology: Named after the loving memory of Anne Ekins and Anna Nelson, both of whom instructed the senior author about the beautiful design in nature.

Distribution: This species is currently known only from the central coast of New South Wales, Australia, at abyssal depth.

Description:

Growth form: The holotype consists of the remains of a stem supporting a slightly cupped obovate (leaf-like, flabellate, fan-shaped) apical body (Figure 4 F). The body is hispid, with bundles of spicules radiating out only over a 90° quadrant. The specimen is 3 mm long x 2 mm wide.

Colour: Beige on deck and beige in ethanol.

Ectosomal skeleton: Thin membranous layer encrusted with abyssochelae.

Endosomal skeleton: The axis of the stem consists of longitudinally arranged subtylostyles. The main body consists of radiating bundles of subtylostyles, undifferentiated from those of the stem.

Megascleres: Subtylostyles are long and straight, thickest in the centre with a sharp tip (288-(504)- 1000 x 3.1- (7.4)-15.2 μm, n=49).

Microscleres: Abyssochelae isochelae with obvious ridge and curved triangular shaft. (48.2-(60.6)-72.2 x 5.1- (9.7)-14.9 μm, n=45). Sigmancistras (11.6-(15.6)-18.5 x 0.9-(1.3)-1.8 μm, n=54).

Molecular data: It was not possible to get unambiguous molecular data from the type material.

Remarks: The shape of this species resembles one of the distal ends of the branches of A. koltuni Ereskovsky & Willenz, 2007 from the Sea of Okhotsk. However, A. annae sp. nov. lacks the large filament-forming mycalostyles that radiate from the oval bodies of A. koltuni, and also differs in lacking sigmas and having only a single size class of abyssochelae, which presents a very different shape to the isochelae of A. koltuni (Table 1). The gross morphology of this new species also superficially resembles that of the distal parts of A. hemiradiata Hestetun et al., 2017a from the SW Indian Ocean Ridge, but differs in having the slightly cupped morphology, with mainly bundles of subtylostyles radiating in one quadrant only.

Abyssocladia annae sp. nov. also lacks the larger and thicker styles and the sigmas of A. hemiradiata, and has much larger sigmancistras (Table 1). Most obvious in this new species is the much larger and highly ridged abyssochelae. The only other Abyssocladia with similar chelae is A. brunni Lévi, 1964 from the Kermadec Trench. Abyssocladia annae sp. nov. differs in morphology from A. brunni which has a stem supporting a pedunculate spherical body heavily echinated by large lateral filaments up to 13 mm in length, as described both in Lévi (1964) and Koltun (1970). In addition, the current species also has smaller isochelae of a different shape (which Lévi 1964 terms ‘thaumatochetes’), sigmancistras only half the size, and smaller subtylostyles than those of A. brunni. In addition, A. brunni has styles, with only few showing slight subtylote basal swelling. The two known specimens of A. brunni described by Lévi (1964) and Koltun (1970) are possibly two different species. Abyssocladia annae sp. nov. also differs from A. natushimae Ise & Vacelet, 2010 from the Izu-Ogasawara Arc, in lacking filaments that echinate the main body, and the absence of styles, strongyles, and substrongyles and microstrongyles found in the Japanese species (Table 1).