Esperiopsis flagrum, 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 : 20-23

Esperiopsis flagrum sp. nov.

( Fig. 12 a–d, Fig. 13 a–d)

Description

Similar whip­like growth form ( Fig. 12 a, b) as known from the genera Asbestopluma and Euchelipluma elongata sp. nov., described above. The holotype was broken in half during collection but the specimen had a total length of 54 cm. This specimen was encrusted near its base with the demosponge Lissodendoryx oxeata Koltun, 1958 . The specimen is a beige, cylindrical sponge, tapering towards the top end, beset with numerous whitish thin processes, 3–5 mm in length, elastic but somewhat stiff. The diameter, without the whitish filaments, is 4 mm at the base, 2.5 mm at the tip. This axis is compressible, elastic but resilient.

Skeleton: There is no special ectosome developed. The central axis of the longitudinal sponge consists of interwoven polyspicular tracts of styles with many microscleres in between. Single tracts are 150–600 µm in diameter. The lateral processes are supported by single polyspicular tracts running into them. The outermost layer of the processes and the longitudinal axis consists of densely arranged microscleres.

Spicules: Megascleres are fusiform styles ( Fig. 12 c), 980– 1320 x 20–28 µm. Microscleres are large, palmate isochelae ( Figs. 12 d, 13 a), 98–112 µm, small, palmate isochelae ( Figs. 13 b, c), 28–43 µm, small sigmas ( Fig. 13 d), 17–20 µm, large sigmas ( Fig. 13 d), 37–48 µm.

Discussion

E. flagrum fits perfectly in the revived family of Esperiopsidae (Van Soest & Hajdu, 2002:656) of sponges with “mycalostyles and lack of an ectosomal skeleton. … Microscleres if present include palmate isochelae, exceptionally anisochelae and sigmas.” We assigned the present species to the genus Esperiopsis without any doubt as the skeleton consists of irregularly anastomosing spicule tracts which are more dense in the interior, the styles are exceeding 400 µm in length, sigmas are present and palmate chelae occur in two size categories. There are 43 species of Esperiopsis described worldwide; 22 of them from the Arctic, N­Atlantic or N­Pacific which we compare with our species. These species with their growth forms, spicule types and measurements are listed in table 1. According to Van Soest and Hajdu (2002) the distinction between Esperiopsis and Amphilectus is that Esperiopsis usually has styles longer than 400 µm, and several size categories of isochelae and sigmas are present while Amphilectus has styles shorter than 400 µm, and only one category of isochelae and no sigmas. Accordingly, two species, one of which has been categorized into two subspecies, were described as Esperiopsis ( E. digitata digitata , E. digitata infundibula and E. columnata ) but should be placed in the genus Amphilectus (cf table 1) according to the diagnoses above. Seven additional species ( E. laxa , E. pedicellata , E. plumosa , E. praedita , E. profunda , E. stipula , E. uncigera ) are not so easily assigned because they have characteristics intermediate of the two genera (e.g. styles longer than 400 µm, only one category of isochelae and no sigmas). Conspecifity with these ten species is excluded because several spicule types found in E. flagrum are missing from these species. Of the remaining 15 species only E. symmetrica has a similar growth form but it has only one type of isochelae and only one category of sigma and thus differs in two spicule types from E. flagrum . All remaining species of Esperiopsis differ considerably in growth form and also in at least one spicule category (cf table 1)

Distribution

Known only from the type locality.

Etymology

Referring to the growth of the species from latin: flagrum—whip.

Figures

FIGURE 12. Esperiopsis flagrum sp. nov. a, Holotype in situ at 955 m depth in Amchitka Pass. b, holotype after collection. c, Long fusiform styles and microscleres. d, Microscleres overview: large and small categories of isochelae and sigmas.

FIGURE 13. Esperiopsis flagrum sp. nov. a, backside of large isochela. b, Small isochela. c, Side view of small isochela. d, Large and small sigmas.