Abyssocladia polycephalus, Hestetun, Jon T., Pomponi, Shirley A. & Rapp, Hans Tore, 2016

Hestetun, Jon T., Pomponi, Shirley A. & Rapp, Hans Tore, 2016, The cladorhizid fauna (Porifera, Poecilosclerida) of the Caribbean and adjacent waters, Zootaxa 4175 (6), pp. 521-538 : 523-525

Abyssocladia polycephalus sp. nov.

( Figure 2–3 )

Type material. Holotype: YPM IZ 0 53327, R/V “ Atlantis ” cruise AT07-35 (2003–06–05, Muir Seamount, Alvin St. 1, 33°45.42’N, 062°36.06’W, 2829 m) . The holotype was recovered during the 2003 R/V “ Atlantis ” cruise AT07-35 to the Muir , Manning and Gregg seamounts off Bermuda, collected using the Alvin submersible.

Etymology. From Greek poly, meaning many and cephalus, latinized form of the Greek kephalos, meaning head. The name is derived from the multiple disc-shaped bodies of the species.

Diagnosis. Erect, slender Abyssocladia consisting of a central stem with side branches each ending in a disclike body bearing filamentous projections. Megascleres are mycalostyles, subtylostyles and substrongyles; microscleres are arcuate isochelae and sigmancistras.

Description. A single specimen consisting of a 35 mm long smooth, curving and flexible stem, with 3–4 up to 10 mm long slightly thinner side branches broken off during collection and preservation. The basal part of the sponge is missing. The branches and main stem each end with a slightly swollen, elongated, disc-like body with radiating filaments. Color is white in ethanol, with a slight yellow tint. No aquiferous system was observed ( Fig.

2A–B). The specimen was recovered on the surface of an unknown Geodia (aff. megastrella, possibly undescribed) using the Alvin submersible, but it is unknown whether it was originally attached to this sponge.

Skeleton. The central stem and branches consist of densely packed bundles of mycalostyles. Each disc-shaped body is composed of a slightly expanded continuation of the connecting stem or branch with the addition of a network of less well organized subtylostyles as well as radiating bundles of mycalostyles projecting from the body and constituting the skeleton of the filaments. Arcuate isochelae and sigmancistras are found throughout the body tissue, but their exact placement was not determined ( Fig. 2 C–E).

Spicules. Mycalostyles, straight and fusiform, 720–(933)–1070 µm long, 14–(17)–22 µm wide ( Fig. 3 A).

Subtylostyles to mycalostyles, thin, straight and fusiform, with faint, slightly elongated tyle, 430–(686)–960 µm long, 5–(10)–13 µm wide ( Fig. 3 B).

Strongyles, stout and slightly bent, 380–(568)–780 µm long, 15–(18)–22 µm wide ( Fig. 3 C).

Arcuate isochelae, tridentate, with strongly arched shafts, in the body tissue and covering the filaments, 28– (43)–50 µm ( Fig. 3 D–F).

Sigmancistras, thick, straight or contorted, with the concave side clearly flattened into fimbria-like structures towards each end, 9.4–(9.8)–11.0 µm ( Fig. 3 G).

Remarks. The majority of known species within the genus Abyssocladia are small, pedunculate, with a single disc-shaped body and radiating filaments. This body is commonly elongated to a certain degree, and in some species has been modified into a long, flattened central axis with opposite rows of filaments along the sides (e.g. Hestetun et al., 2015; Vacelet, 2006). The habit of A. polycephalus sp. nov., consisting of a branching central stem with several disc-shaped bodies, is highly unusual and has not been recorded in the genus before.

Genus Abyssocladia is mostly known from the Pacific, and only three species have been described from the Atlantic: A. faranauti Hestetun et al., 2015 , A. tecta Hestetun et al., 2015 and A. atlantica Lopes & Hajdu, 2014 . These can be distinguished from A. polycephalus based on their elongated habit as well as differences in spicule complement. The unique habit and lack of cleistochelae or abyssochelae in A. polycephalus make it difficult to distinguish any closely related species. Among other Abyssocladia species, A. claviformis Koltun, 1970 (NW Pacific) lacks cleistochelae and abyssochelae, and has arcuate chelae and sigmancistras of approximately the same size, but can easily be distinguished from A. polycephalus based on morphology and geographical distance.

Figures

FIGURE 2. Habit of Abyssocladia polycephalus sp. nov. holotype YPM IZ 0 53327. A) The whole specimen, stuck to a Geodia directly after retrieval (courtesy of Eric Lazo-Wasem), B) disc-shaped body, C) skeletal structure of body with D) detail and E) filament.

FIGURE 3. Spicules of Abyssocladia polycephalus sp. nov. holotype YPM IZ 0 53327. A) Mycalostyle, B) subtylostyle, C) strongyle, D) arcuate isochelae, E) sigmancistra.