Abyssocladia Levi

Genus Abyssocladia Lévi

Abyssocladia Lévi, 1964: 78.

non Phelloderma Ridley & Dendy, 1886.

Type species. Abyssocladia bruuni Lévi, 1964: 78 (by monotypy).

Diagnosis. Cladorhizidae with abyssochelae and sigmancistras, most often pedunculate and disciform with a radial skeleton (from Lévi, 1964, modified by Vacelet, 2006).

Abyssocladia carcharias sp. nov . (Figs 2, 3)

Material examined. Holotype. NIWA 62124, RV Sonne Stn SO192–2/15, Monowai Seamount, Kermadec Volcanic Arc (New Zealand EEZ), 25.804°S, 177.175°W, 1071 m, 2 May 2007, TV grab.

Type locality. Monowai Seamount, Kermadec Volcanic Arc (New Zealand EEZ), north of New Zealand and southwest of Kingdom of Tonga.

Description. A single small pedunculate sponge, consisting of a long thin peduncle, and a flattened circular body, with a radiating skeleton and short, blunt, radiating filaments (Fig. 2 A). Peduncle broken, devoid of the attachment base, 7 mm long and 0.2 mm in diameter. Body disc-shaped, 3.4 mm diameter, bearing on the edge short, blunt, regularly spaced, radiating filaments, 0.3 mm maximum length, most are possibly broken. Surface of body bearing numerous small sand grains. Color, clear brownish orange in alcohol.

Skeleton. Skeleton radiates in the body, with fascicles of mycalostyles extending in the axis of the filaments, with a few microstyles. Axis of the peduncle is made up of closely packed mycalostyles, without microscleres. Isochelae are abundant on the surface of the body, with the teeth outwardly directed. Substrongyles possibly present in the attachment base, as in most sponges displaying this morphology, but likely lost with the attachment base. No aperture or aquiferous system visible.

Spicules. Megascleres (Fig. 2 B–D), mycalostyles (Fig. 2 B, D), straight, the larger barely fusiform, with a slightly ovoid head and a short distal point, of the same size range in the body and in the peduncle; 510– 1070 x 8– 19 µm. Microstyles (Fig. 2 C), straight or slightly flexuous, rare in the body, not seen in the peduncle, possibly immature mycalostyles; 140–240 x 2.5–5 µm. Microscleres (Fig. 2 E–H), isochelae I (Fig. 2 E; Fig. 3 A, B), multidentate, possibly derived from an anchorate chelae. Shaft flattened, strongly curved, bearing on both sides a long, curved central tooth, and five to six alae, or spines, arranged on both side of the shaft, gradually decreasing in size towards the center of the spicule, curving inwards. Larger alae curved, sharply pointed. Incompletely formed spicules are bow–shaped, bearing only small swellings near the ends, then small spines on the shaft (Fig. 3 A, B). A few mature spicules display lanceolate and flexuous teeth, rarely divided at the end; 116–197 µm, larger tooth, 63– 65 x 15 µm, at the base. Isochelae II (Fig. 2 F; Fig. 3 C), same shape as isochelae I, but smaller and with generally only four series of lateral spines instead of five; 60–86 µm. Isochelae III (Fig. 2 G; Fig. 3 C), same shape as I and II, but smaller and with less numerous spines; 35–48 µm. Sigmancistra I (Fig. 2 H, upper), rare, with a flattened shaft; 15–16.2 x 1.9–2 µm. Sigmancistra II (Fig. 2 H, lower), very numerous; 8–12 µm.

Substrate, depth range, and ecology. Attached to hard substrate on Mussel Ridge, on the western side of active volcano Monowai Seamount. Volcanic activity producing gas effervescence and green colouration was visible at the surface at the time of collection. Visibility was poor, with turbulence and detritus in the water column, and there was evidence of explosions and active hydrothermal vents on seafloor. Large flat lava pillows, steep slopes and soft sediment visible, collected between 1071–1431 m.

Etymology. Named for the remarkable shape of the abyssochelae, which resemble the jaws of the great white shark Carcharodon carcharias (charchar, ancient Greek for acerate; referring to the shape of the abyssochelae).

Remarks. This small sponge is a pedunculate disc with lateral filaments typical of most Abyssocladia, Neocladia flabelliformis Koltun, 1970 and Lollipocladia tiburoni Vacelet, 2008. It is well characterized by unusual abyssochelae that have alae, or additional curved spines, arranged along the entire shaft, and not grouped near the end of the shaft, as is typical of most abyssochelae. These chelae, and in particular, those in the smallest category (Fig. 3 C), are somewhat reminiscent of the large anchorate chelae of Lollipocladia tiburoni, but in this species the chelae have modified fimbriae and the alae are grouped at the ends of the shaft. Abyssocladia carcharias sp. nov.

differs from Lollipocladia, however, by the absence of palmate isochelae. This is considered to be a plesiomorphic loss and thus of little consequence above the species level, unless we find other species with these characteristics. Furthermore, in Abyssocladia carcharias sp. nov., there is no equivalent to the fimbriae, and the chelae are regarded as derived of arcuate chelae. The new isochelae of Abyssocladia carcharias sp. nov. may also be compared to some developmental stages of the abyssochelae of Abyssocladia huitzilopochtli Vacelet, 2006, but these have a different ornamentation of the curved ‘backbone’. The sponge is thus allocated to the genus Abyssocladia, for the time being, although its unique chelae are rather different from what has been called abyssochelae in the type species and in other species of the genus.