Amphilectus utriculus Van Soest, Beglinger, Vooged 2012, sp. nov.

Amphilectus utriculus sp. nov.

Figs 2-3

Etymology

utriculus (L.) = small water bag, referring to the hollow, flattened shape.

Material examined

Holotype

ZMA Por. 22592, Mauritania, SW of Cap Timiris, depth 260-280 m, muddy bottom, coll. R. W.M. Van Soest & J.J. Vermeulen, Mauritania II Expedition stat. 39/01, 18.8°N 16.7167°W, 3.5 m Agassiz trawl, 10 Jun.1988.

Paratypes

ZMA Por. 06636, 53 specimens, Mauritania, SW of Cap Timiris, depth 260-280 m, muddy bottom, coll. R.W.M. Van Soest & J.J. Vermeulen, Mauritania II Expedition stat. 39/01, 18.8°N 16.7167°W, 3.5 m Agassiz trawl, 10 Jun. 1988. ZMA Por. 06668, Mauritania, SW of Cap Timiris, depth 500 m, fossil coral debris, coll. R.W.M. Van Soest & J.J. Vermeulen, Mauritania II Expedition stat. 40/20, 18.85°N 16°8833°W, 3.5 m Agassiz trawl, 10 Jun. 1988.

Additional specimen

ZMA Por. 06627, Mauritania, SW of Cap Timiris, depth 200 m, muddy sand, coll. R.W.M. Van Soest & J.J. Vermeulen, Mauritania II Expedition stat. 35/01, 18.75°N 16.7°W, Van Veen grab, 9 Jun. 1988.

Description

The holotype (Fig. 2A) and most other specimens (Fig. 2B) are short-stalked, with main body laterally flattened, isodiametrical or either tapering inward near the upper end or flaring, with smaller or wider opening. Main body hollow, like a purse. Colour reddish or greyish brown, both alive and in alcohol. Surface irregular, shaggy. Consistency very soft, limp, easily damaged. Stalk rounded, but grading into the main body by widening, surface slightly smoother. Size 6 cm high (holotype), up to 8 cm high (paratypes), 0.8 cm (holotype), up to 1 cm (paratypes) in widest expansion, proportion of stalk and main body approximately 1:3.

SKELETON. There is no special ectosomal skeleton, skeletal bundles are simply protruding beyond the surface. Choanosomal skeleton consists of polyspicular bundles (Fig. 2C), with 3-6 spicules in cross section, connected regularly by 1-2 spicules at right angles. Near the surface the bundles fan out to form loose brushes. Microscleres are concentrated lining the bundles and crowding the brushed endings at the surface (Fig. 2D). In the interior, microscleres are scattered and distinctly less numerous than at the surface.

SPICULES. (Figs 2E, 3) Styles, palmate isochelae.

STYLES. (Fig. 3A, A 1) Of the mycalostyle-type, slightly constricted near the rounded end, straight, or more commonly slightly curved, 330- 371.2- 414 x 11- 12.7 - 14 µm.

PALMATE ISOCHELAE. (Fig. 3B) ‘Normal’-shaped, but with the frontal alae appearing somewhat angular in side-view, with the shaft slightly incurved, all closely similar in size, 52 -59.6- 66 µm.

Distribution and ecology

Mauritania, S of Banc d’Arguin (Fig. 1, loc. 3), muddy bottom at 200-500 m depth.

Remarks

Assignment to the genus Amphilectus is based on the possession of a single microsclere type, although technically speaking the size of the styles exceeds the 400 µm upper size given as an additional character of Amphilectus. North Atlantic Amphilectus species with pedunculate shape were reviewed from literature descriptions (see also Table 1). A. columnatus (Topsent, 1890) (as Esperiopsis) from deepsea waters around the Azores has much longer styles (750 µm) and much smaller isochelae (16 µm). A. pedicellatus (Lundbeck, 1905) (as Esperiopsis) from West Greenland likewise has longer styles (up to 940 µm) and very small chelae (13-15 µm). Further species are not only different in shape, but also show spicular differences: A. fucorum (Esper, 1794) (as Spongia) is massively-encrusting to digitateramose and has smaller spicules overall (see also below). A. lobatus (Esper, 1794) (as Spongia) is lobate and likewise has smaller spicules, and the isochelae are verging toward an anisochelate condition. Both A. fucorum and A. lobatus are essentially shallow-water species. A. typichela (Lundbeck, 1905) (as Esperiopsis) is encrusting and has two distinct size classes of isochelae.

Southward along the African coasts, in Namibian and South African waters, three further species have been recorded: A. rugosus sensu Uriz (1988) [as Esperiopsis, probably not conspecific with the Chilean species A. rugosus (Thiele, 1905)] is a whitish massive sponge with much smaller isochelae. A. lesliei (Uriz, 1988) (as Esperiopsis) is ramose and has strongyles as megascleres, distinctly smaller than the styles of the new species. A. informis (Stephens, 1915) is encrusting and has much smaller spicules.

ZMA Por. 06627 from Mauritania (stat. 35/01) is a small whitish crust showing the same skeletal structure and a spicule complement slightly smaller but essentially similar to the above described specimens: styles 302- 329.5 -353 x 6- 9.1 - 12 µm, palmate isochelae: 33- 43.5 - 51 µm. For the time being this is assumed to be an incipient individual of A. utriculus sp. nov., but the colour and the encrusting habit point to a possible separate species.