Lycopodina brochidodroma, Ekins & Erpenbeck & Hooper, 2020

Ekins, Merrick, Erpenbeck, Dirk & Hooper, John N. A., 2020, Carnivorous sponges from the Australian Bathyal and Abyssal zones collected during the RV Investigator 2017 Expedition, Zootaxa 4774 (1), pp. 1-159 : 149

Lycopodina brochidodroma sp. nov.

Fig. 31 , Table 14

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Material Examined: Holotype QM G337540 , off Moreton Island , Station 103, Queensland, Australia, 27° 0’ 1.1”– 27° 3’ 39.6” S, 154° 13’ 22.8”– 154° 13’ 22.8” E, 4260–4280 m, Brenke Epibenthic Sledge, Coll. Merrick Ekins on RV Investigator, Cruise IN2017_ V03 , Sample 103-122, 10/vi/2017.

Etymology: brochis, Gr. inkhorn, apodrome, Gr. f. running from, divergence. Named after the species’ body shape that is reminiscent of a particular vein-like pattern found in some leaves, i.e. brochidodromous, of a leaf nerve: forming loops.

Distribution: This species is presently known only from type locality off Moreton Island, Queensland, at abyssal depth.

Description:

Growth form: The sponge consists of an erect central axis with long lateral filaments on opposite sides, alternating every second row, so that the sponge has four columns of filaments ( Figure 31 A ). The filaments (presumably due to the epibenthic dredge) emerge at almost right angles from the axis ( Figure 31 G–H), but then curve through 90 degrees, and are then arranged in an almost parallel arrangement to the axis. This gives rise to the appearance of the veins in a leaf. The sponge is only 20 mm in length, and 1 mm in width including the folded filaments. The central axis is only 0.25 mm in width and the filaments, excluding the buttressed attachments, narrow from 90 µm down to a blunt point of about 20 µm. The specimen has been broken so it is not possible to determine the original length, nor the attachment structures. The entire sample is now embedded on SEM stubs.

Colour: White in ethanol.

Ectosomal skeleton: The ectosomal skeleton is thin and membranous and contains the palmate anisochelae ( Figure 31 H–I).

Endosomal skeleton: The axis consists of mycalostyles and secondary subtylostyles in longitudinal bundles ( Figure 31 H ). Subtylostyles occur as supporting structures where the filaments attach to the main axis.

Megascleres: Oxeote mycalostyles with long tapering points, slightly sinuous shaft with largest diameter at the centre of the spicule, and with evenly rounded bases (621-(1364)- 1816 x 7.4-(19.4)-32.7 μm, n=17) ( Figure 31 C–D). Subtylostyles straight or slightly curved, with tyle slightly subterminal from the base (202-(285)-328 x 3.6- (5.4)- 7.8 µm, n=26) ( Figure 31 E–F).

Microscleres: Palmate anisochelae of a single size class, with the three upper alae smooth, palmate, with the frontal alae partly fused to the lateral alae for about 50% of its length, lateral alae completely fused to the fimbria, and the three lower alae fused, arcuate, with the frontal one with three spines and the two lateral alae each with two spines (10.7-(12.9)-15.2 x 2.4-(3.3)-4.9 μm (upper alae width) x 2.8-(3.4)-4.2 μm (lower alae width), n=107) (Fig- ure 31 B).

Molecular data: Nil

Remarks: Although the growth form of this sponge appears to be quite similar to Asbestopluma biseralis ( Ridley & Dendy, 1886) , depicted in Ridley & Dendy (1887, Pl. XIV) and Lévi (1964, Pl. III H), it differs in having the double lower teeth of the anisochelae, placing it in Lycopodina , lacking the small contort sigmas, and having smooth, not spined subtylostyles found in A. biserialis .

Figures

FIGURE 31. Lycopodina brochidodroma sp. nov. Holotype QM G337540. A. Holotype under SEM. B. Palmate anisochelae. C. Large mycalostyle. D. Magnified ends of the mycalostyle illustrated in C. E. Subtylostyle. F. Magnified ends of the subtylostyle illustrated in E. G. Body showing filament attachments. H. Close-up of the body, showing both types of styles in the axis and the anisochelae on the thin ectosome. I. Filament showing the anisochelae encrusting the mycalostyles. J. Amphipod captured by the sponge.