Monanchora laminachela, Lehnert, Helmut, Stone, Robert & Heimler, Wolfgang, 2006

Lehnert, Helmut, Stone, Robert & Heimler, Wolfgang, 2006, New species of deep­sea demosponges (Porifera) from the Aleutian Islands (Alaska, USA), Zootaxa 1250, pp. 1-35 : 10-13

Monanchora laminachela sp. nov.

( Fig. 6 a–d, Fig. 7 a–d)

Material

Holotype: USNM 1084240 (51° 31.491' N, 177° 57.506' W, South of Tanaga Island, 485 m depth, 0 2. 0 8. 2004). Paratype: USNM 1084241 (51° 31.491' N, 177° 57.506' W, South of Tanaga Island, 485 m depth, 0 2. 0 8. 2004).

Description

The two specimens collected are stalked sponges with subglobular bodies ( Fig. 6 a), 9–10 cm in height, maximum diameter of the body 6 cm growing on a large boulder. The smooth stalk is about 4 cm long and 2–4 mm in diameter. The body has a corrugate surface in life ( Fig. 6 a) which becomes conulose ( Fig. 6 c) after freezing the specimen. The consistency is elastic but firm. Colour in life yellow, changing to orange brown after freezing ( Figs. 6 a–c).

Skeleton: The ectosomal skeleton consists of a thick membrane of tangential brushes of smaller styles, fairly dense, and many isochelae in between. The choanosomal architecture consists of thick, ascending polyspicular tracts of large, thick styles connected by shorter tracts of large styles. Ascending tracts are 114–387 µm in diameter, support the surface tubercles and are visible to the unaided eye when dissecting the sponge. Individual tracts can be several cm long, occasionally they divide into two tracts and are then connected over a distance of 2–3 mm by single spicules.

Spicules: Megascleres are thin, small, ectosomal (sub)tylostyles ( Fig. 7 a), 350–395 x 9–11 µm and choanosomal thick styles ( Fig. 6 d), 840–1170 x 34 –42 µm. Two categories of microscleres: anchorate isochelae with a peculiar plate in the middle ( Fig. 7 b, c) and with some remarkable variations, 22–25 µm and thin sigmas ( Fig. 7 d), 19–23 µm.

Discussion

Due to its spicule set of ectosomal thinner styles, choanosomal thick styles, anchorate chelas and sigmas, this species fits into the concept of Crambeidae and the genus Monanchora of Van Soest (2002:547,553). Echinostylinos Topsent, 1927 has a similar set of spicules but differs in having arcuate isochelae, therefore assignment of the present species to Echinostylinos is excluded. There are 17 nominal species of Monanchora described worldwide; four species are regarded synonymous with M. arbuscula Duchassaing & Michelotti, 1864 by Van Soest & Hooper (2005) which leaves a total of 12 known species. Ten species occur in warm shallow seas of the Caribbean, Indian Ocean, Indonesia, South Pacific and Australia and are not considered further in this discussion. The new species will be compared to the remaining three species — M. alaskensis ( Lambe, 1894) from Chika Island and other Alaskan localities, M. pulchra ( Lambe, 1894) from the Pacific coast of Canada and Monanchora stocki (Van Soest, 1992) from the Cape Verde Islands, Atlantic Ocean.

M. alaskensis is also a stalked species but, the stalk is very short and relatively thick. The body differs in being lobate and having a smooth surface with many oscules flush with the surface versus a tuberculate surface in the species described here. Its ectosomal styles (144 x 8 µm) and its choanosomal styles (262 x 19 µm) are much smaller, its large isochelae (91 µm) and its small category of anchorate isochelae (32 µm) are both larger and are both lacking the peculiar central plate displayed by M. laminachela . M. alaskensis is lacking sigmas. Koltun (1959) described M. alaskensis as Stelodoryx and gave slightly different measurements of the spicules: ectosomal strongyles to styles, 124–228 x 8–9 µm, choanosomal styles, 156–383 x 16–25 µm, large anchorate isochelae, 65–108µm and small isochelae, 29–44µm. Koltun reported the species from the Bering Sea and the Okhotsk Sea as fairly common from 32–148 m depth. Thus M. laminachela differs in its conulose surface, in its considerably larger ectosomal and choanosomal styles, in having only one category of isochelae which is much smaller and in the occurrence of sigmas. M. pulchra ( Lambe, 1894) also is stalked but again with a short thick stalk and the body irregularly ramose to almost fan­shaped due to anastomosing branches. It has a slightly hispid but not conulose surface. The ectosomal styles (176 x 9 µm) are only half the size of M. laminachela while the choanosomal styles (1100 x 41 µm) are about the same size. The isochelae (19 µm) do not have the central plate and the sigmas (13 µm) are smaller. Koltun (1959) recorded M. pulchra as “…foliate, up to 15 cm in height, is furnished with a thick, rigid stem…”. He gave the spicule dimensions with: ectosomal styles, 280–760 x 8–13 µm, choanosomal styles, 613–1768 µm x 29–44 µm, anchorate isochelae, 18–25 µm, sigmas 13–21 mm. Koltun reported M. pulchra from the southern Kuril Islands near the Aleutian Islands from 87–232 m depth. Similarly, we have observed M. pulchra at depths between 80 and 210 m in the central Aleutian Islands (unpublished observations). Taking both descriptions into consideration M. laminachela differs from M. pulchra in its relatively longer and thinner stalk, in the tuberculate surface and the subglobular body. Its megascleres have a much narrower size range, the central plate of the isochelae is not displayed by M. pulchra but the dimensions are comparable. M. stocki reported from shallow water near the Cape Verde Islands, Atlantic Ocean is an encrusting species. Its ectosomal subtylostyles (175–263 x 1 –3.5 µm) and its choanosomal tylostyles (161–362 x 4–7 µm) are smaller, its isochelae (16–24 µm) of comparable size, but different shape and it is lacking sigmas. M. laminachela differs in growth form, surface structure, dimensions of megascleres, shape of isochelae and the occurrence of sigmas.

Distribution

Known only from the type locality.

Figures

FIGURE 6. Monanchora laminachela sp. nov. a, Type specimens in situ, indicated by white arrows. b, Type specimens shortly after collection. c, Type specimens after being frozen. Note different color and different surface structure. d, Choanosomal thick style among thin styles.

FIGURE 7. Monanchora laminachela sp. nov. a, Ectosomal thin style. b, Anchorate isochela with characteristic central plate. c, Variation of isochela with fused alae. d, Sigma.