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

Abyssocladia gliscofila sp. nov.

Figure 5, Tables 1 & 3

urn:lsid:zoobank.org:act: 7402B815-BAB6-4802-872D-B3F4D165CEED

Material examined: Holotype: QM G337499, off the continental shelf adjacent to the Hunter Valley Region, Station 69, New South Wales, Australia, 32° 28’ 44.4”– 32° 30’ 25.2” S, 152° 59’ 38.4”– 152° 59’ 27.6” E, 1006–1036 m, Beam Trawl, Coll. Merrick Ekins on RV Investigator, Cruise IN2017_ V03, Sample 69–246, 3/vi/2017.

Paratypes: QM G337475, off Hunter Valley Region, Station 69, New South Wales, Australia, 32° 28’ 44.4”– 32° 30’ 25.2”S, 152° 59’ 38.4”– 152° 59’ 27.6” E, 1006–1036 m, Beam Trawl, Coll. Merrick Ekins on RV Investigator, Cruise IN2017_ V03, Sample 69–245.3, 3/vi/2017; QM G337523 off Gold Coast, Station 100, Queensland, Australia, 28° 3’ 15.8”– 28° 5’ 49.2” S, 154° 4’ 58.8”– 154° 4’ 51.6” E, 999–1013 m, Beam Trawl, Coll. Merrick Ekins on RV Investigator, Cruise IN2017_ V03, Sample 100–113, 9/vi/2017; QM G337492 same collection details as QM G337523, Sample 100–113.1.

Etymology: Named for the shape and distribution of the filaments that increase in size as they travel up the stem of this sponge, from glisco (L.) to grow up, increase, swell or spread.

Distribution: This species is only known from the continental slope of two localities adjacent to the east coast of Queensland and New South Wales, Australia, at bathyal depth.

Description:

Growth form: Delicate erect pedunculate sponge anchored in muddy substrate, with a long, very thin stem, inflated filaments that increase in size towards the apex, and basal rhizoid holdfast with fine rootlets anastomosing from the main root branches (Figure 5 A & B). Whilst the whole specimen of the holotype is just less than 120 mm in length, the peduncle is 85 mm long and only 0.15 mm wide. The main body including filaments is 20 mm in length, and 5 mm wide. The filaments themselves are about 2.5 mm in length and 0.3 mm in width. The remainders of the rootlets are 20 mm long and 0.15 mm wide. The main stem of the sponge is protected by spicules projecting at right angles to the surface 120 µm out and approximately the same distance apart. The paratype QM G337475 is almost identical at 130 mm in length. However, the other two paratypes which may represent more mature forms that have a much wider stem of almost 1 mm diameter. Paratype QM G337492 whilst also 120 mm in length, the filaments are 10 mm in length, but it has thick hard basal rhizoid attachment 1.5 mm in diameter. Paratype QM G337523 is very similar to QM G 337492, 124 mm in length and a stem almost 1 mm in diameter, which is entirely covered in filaments, but both ends of the sponge were lost during collection.

Colour: Pale cream on deck and beige in ethanol.

Ectosomal skeleton: The ectosomal skeleton is thin and membranous, and usually contains the isochelae.

Endosomal skeleton: The axis of the stem, filaments and upper part of the basal holdfast rootlets consist of tightly bound mycalostyles longitudinally arranged. The axis of the fine rootlets that branch from the basal holdfast consists of a different kind of style with a rounded non-tylote base and evenly tapering to a sharp point, also forming tightly bound longitudinally arranged tracts.

Megascleres: Mycalostyles in the stem, filaments and basal rootlets are nearly oxeote, long and thin, widest at the centre, and usually straight with sharp tips (319– 1560 x 2.0– 22.7 µm). Styles in the fine basal rootlets are straight or slightly curved with a rounded base and sharply pointed tip (179–470 x 4.0–10.2 μm) (see Table 3).

Microscleres: Arcuate isochelae, with well separated alae, with some smaller spicules almost palmate, with the lateral alae fused to the shaft for a greater part of their lengths (22.4–42.0 x 1.5–7.0 μm) (see Table 3).

* 1 No fine basal root hairs remaining on QM G337523

* 2 No basal roots remaining on QM G337492

Molecular data: The 28S sequence of QM G337499 is provided in the Sponge Barcoding Database under accession number SBD#2301 and the molecular difference to other congenerics displayed in Figure 3.

Remarks: This species is another greatly reduced Abyssocladia in terms of its spicule composition, having only mycalostyles in the stem, filaments and basal rhizoid holdfast, styles in the fine basal rootlets that branch from the rhizoid, arcuate isochelae microscleres, and with a relatively large size ranging from 120 to 130 mm in height. It differs from the other three species known to date from the eastern Australian mesophotic to abyssal zones, all of which are pedunculate in growth form, as follows: A. desmophora (Hooper & Lévi, 1989) from the north Queensland continental slope is 24 mm high and has desmas, subtylostyles, sigmas, and arcuate isochelae that are more than double the size of those of the new species; A. annae sp. nov. is a tiny species only 3 mm high, with undifferentiated subtylostyles as structural megascleres, sigmancistras and abyssochelae as microscleres; conversely, A. escheri sp. nov. is the second largest known species of Abyssocladia, up to 305 mm high, with two size classes of structural styles and abyssochelae in a wide size range (see Table 1).

Abyssocladia gliscofila sp. nov. differs from other Abyssocladia species with pedunculate growth form, reduced spicule diversity and arcuate isochelae, as follows (see Table 1).

Abyssocladia claviformis Koltun, 1970 from the NW Pacific, differs by the possession tylo-to subtylostyles as megascleres, in addition to sigmas as microscleres. Abyssocladia oxeata Koltun, 1970 also from the NW Pacific, has a different pedunculate morphology consisting of a very obvious rounded body on a stem, and in addition to mycalostyles which are nearly twice the size of those in A. gliscofila sp. nov., it also small oxeas as megascleres, and sigmas and microstyles among its spicule complement. Abyssocladia diegoramirezensis Lopes et al., 2011 from the Diego Ramírez Archipelago, differs in having strongyles-substrongyles as additional megascleres, and cleistochelae, abyssochelae, sigmancistras and sigmas as additional microscleres. Abyssocladia dominalba Vacelet, 2006 from the North-Fijian back-arc Basin, differs in having only styles as megascleres, and abyssochelae-cleistochelae, anisochelae, and two categories of sigmancistras. Abyssocladia flagrum (Lehnert et al., 2006) from the Aleutian Islands, differs in growth form, being a whip-like ‘bottlebrush’, with similar isochelae that are predominantly arcuate but with a proportion verging on palmate, but that species also has two categories of sigma microscleres. Abyssocladia leverhulmei Goodwin et al., 2017 from the Drake Passage seamounts, in addition to mycalostyles in the body and stem, it also has strongyles in the basal skeleton, and abyssochelae as additional microscleres. Abyssocladia polycephalus Hestetun et al., 2016b from the Muir Seamount, Bermuda, has strongyles in addition to mycalostyles in the axis of the filaments, and sigmancistras as additional microscleres. Abyssocladia symmetrica (Ridley & Dendy, 1886) from Prince Edward Island, also has a reduced spicule compliment consisting of only mycalostyles as megascleres, arcuate isochelae microscleres, but has a different ‘bottlebrush’ growth form and also has sigmancistras. Lastly, Abyssocladia umbellata Lopes et al., 2011 from the Diego Ramírez Archipelago, differs in having a ‘centi- pedal’ growth form, has strongyles in addition to mycalostyles in the main axial skeleton, styles to sub-strongyles in the basal skeleton, and abyssochelae and sigmas as additional microscleres.