(Vacelet, Jean & Kelly, Michelle 2014)
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- Abyssocladia Vacelet, Jean, 2014, Zootaxa 3815: 387-392.
Diagnosis.Cladorhizidae most often pedunculate, carrying a disciform or flabelliform body with a radial architecture. Microscleres are a combination of abyssochelae, cleistochelae, arcuate chelae, and/or sigmancistras (Lopes, Bravo & Hajdu 2011). Abyssocladia lakwollii sp. nov. (Figs 1–3, Tab. 1)
Material examined. Holotype— NIWA81633: Z 15666, far eastern Solomon Islands, 12 ° S, 167 ° E, 1090 m, 9 Jan 2012, ROV. Paratypes— NIWA81378, Z 15666, far eastern Solomon Islands, 12 ° S, 167 ° E, 1090 m, 9 Jan 2012, ROV (eight specimens); NIWA81379: Z 15665, far eastern Solomon Islands, 12 ° S, 167 ° E, 1090 m, 10 Jan 2012, ROV (1 specimen). Type locality. Far eastern Solomon Islands.
Distribution. Only known from the Solomon Islands region.
Description. Minute pedunculate sponge consisting of a flattened disc attached at the end of a thin peduncle (Fig. 1), with radiating filaments (Fig. 1 D), absent in the preserved specimens, that form a flat to concave umbrella (Fig. 1, 2 A, B). Total length of the largest collected specimen, the holotype, is 5.7 cm. Stalks are smooth, ranging from 21.8–44.3 mm long and 0.4–0.9 mm in diameter, attached by an expanded base to a small piece of rocky debris, present in only three of the specimens. Body discs are 4–10.8 mm in diameter, approximately 1.2 mm thick, bearing short conical expansions 1.25 mm in maximum length, regularly disposed on the rim, being the remains of radiating filaments more or less well preserved. Color in life, pure white (Fig. 1 D), in ethanol preservative white or cream, appearing translucent with a few small brown dots or blotches. Living tissue appears quite dense. No apertures or canal system visible. In situ photographs taken by ROV at the collection site show an abundant species, pure white in color, of the same shape as the collected specimens, but with a remarkable halo of radiating filaments (Fig. 1 B, D). The approximate size estimated from the ROV laser pointer is in accordance with the collected specimens: stalk 18–39 mm long, disc 8–17 mm in diameter. The filaments, 6.5–19 mm long and 30 to 40 in number, all ending in a small swelling (Fig. 1 D).
Skeleton. Peduncle made up of tightly packed large mycalostyles (Fig. 3 A), longitudinally arranged with points upwardly directed, and very few microscleres. Attachment base with tightly packed shorter mycalostyles I and substrongyles. Mycalostyles I of the peduncle fan out in the disc, diverging into radiating fascicles towards the rim (Fig. 3 B). Numerous small diverging fascicles of mycalostyles II are dispersed in the disc. Microscleres are dispersed throughout the disc; highly abundant sigmancistras create a dense lining around the expansions of the rim of the disc. Spicules. Megascleres (Fig. 2 C–F, Tab. 1), mycalostyles I (Fig. 2 C) of peduncle and disk, straight, feebly fusiform, head sometimes feebly swollen, tip short and acerate; 750– 1800 x 15–31 µm. In the attachment base and the basal part of the stalk, these megascleres are shorter and thicker, often curved in the middle, without swelling at the head, and with a blunt point; 380–980x 18–30 µm, with intermediaries with the mycalostyles of the disk. Substrongyles in the attachment base (Fig. 2 F), overlapping in size with mycalostyle I, slightly curved near the middle; 250– 1150 x 12–30 µm. Mycalostyles II (Fig. 2 D–E) of the disk, overlapping in size with mycalostyles I although generally thinner, straight, not fusiform, head more swollen than in mycalostyles I, tip short and acerate; 330– 1150 x 6–20 µm. Microscleres (Fig. 2 G–L), isochelae I (anchorate) (Fig. 2 G), more or less abundant according to the specimen and location of the sample, always less abundant than cleistochelae. Shaft curved with thin fimbriae of variable development, with five more or less ovoid teeth; 37–52 µm long. Total length 110–150 µm. Isochelae II (a nchorate) (Fig. 2 H), rare, same shape as isochelae I, with five ovoid teeth 35–40 µm long. Total length 58–92 µm. I sochelae III (arcuate) (Fig. 2 I), with ovoid alae and teeth, 27–36 µm. Cleistochelae (Fig. 2 J–K), abundant, with the two central teeth crossing each other at their ends; 48–70 µm. Sigmancistras (Fig. 2 L), very abundant with terminal points short, one slightly curved, with a rather thick shaft; 15–20 µm. Substrate, depth range and ecology. Rocky substrate on chimney vents at 1090 m. The underwater photographs taken by the ROV at the place of collection show a large number of sponges on apparently inactive hydrothermal chimneys, sometimes isolated, but mostly grouped near the tops of the chimneys (Fig. 1). The associated fauna is poor, mostly galatheid crabs a few encrusting sponges, and at least one other carnivorous sponge, possibly Asbestopluma (Asbestopluma) desmophora, also described here. In places, the substrate surface harbors translucent clouds which are probably bacterial mats, possibly indicating that the vents are not yet completely inactive.
Etymology. Named for Mr Moses Lakwolly, a former Minister of Regional Infrastructure in the Temotu Province, Solomon Islands, who is remembered for his contribution to the region and untimely death (Latinised form, genitive case).
Remarks.Abyssocladia lakwollii sp. nov. displays the characteristic shape of many Abyssocladia species, and Lollipocladia tiburoni Vacelet, 2008, with a flat disc surrounded by radiating filaments forming a halo, attached at the end of a long, thin peduncle. The underwater photographs taken by the ROV show that, as in other Abyssocladia species in life, the denticulate margin in collected A. lakwollii sp. nov. represents what were once long radiating filaments. This new species is well characterized amongst pedunculate disc-shaped species by the large size of the isochelae I and by the shape of the cleistochelae with crossed central teeth. The presence of a small swelling at the end of the filaments of A. lakwollii sp. nov., clearly visible on underwater images (see Fig. 1 D), seems to be exceptional amongst known species of Abyssocladia, but it must be emphasised that there are very few good underwater images available of living species. Such swellings have been observed on the ends of filaments in Abyssocladia natushimae Ise & Vacelet, 2010, but the body is not disc-shaped. An unidentified species on a hydrothermal chimney in the Lau Back-Arc Basin, approximately 2700 km southeast of the Solomon Islands (Vacelet & Ségonzac 2006), is extremely similar to A. lakwollii sp. nov. in terms of overall morphology and in the possession of filaments with terminal swellings, but the number of filaments appears to be somewhat greater, up to 60 instead of 30 to 40. Confirmation of identification with A. lakwollii sp. nov. must await examination of the spicule complement of specimens when they can be collected. In all other known species, the filaments of the preserved specimens are broken, or when exceptionally intact, there is no terminal swelling. Abyssocladia lakwollii sp. nov. shows a remarkable diversity of microscleres, which appear to be very specific in this genus. The specimens available show some variation in the size and presence of some spicule categories, and the chelae were not seen in some slide preparations. This is mainly due to the fact that some microscleres, for instance isochelae II, are rare and localized and that the spicule slides were made from a small fragment of each specimen in order to preserve these tiny sponges. The substrongyles were absent from slides which do not include the base of attachment. In some of the paratype specimens a few isochelae were observed with thin, long central teeth and thin alae, 50–60 µm in total length, i.e., in the size range of cleistochelae (Fig. 2 K). They may represent a fourth category of isochelae, but are more likely juvenile stages of cleistochelae.
- Vacelet, Jean; Kelly, Michelle; 2014: A new species of Abyssocladia (Porifera, Demospongiae, Poecilosclerida, Cladorhizidae) and other carnivorous sponges from the far eastern Solomon Islands, Zootaxa 3815: 387-392. doi