Rhabderemia uruguaiensis Van Soest & Hooper, 1993

Oliveira, Maíra V. & Hajdu, Eduardo, 2005, Taxonomy of Rhabderemia Topsent, 1890 collected from the southeastern Brazilian continental shelf and slope by Programme REVIZEE (Rhabderemiidae, Poecilosclerida, Demospongiae), with the description of two new species, Zootaxa 844 (1), pp. 1-12 : 3-5

Rhabderemia uruguaiensis Van Soest & Hooper, 1993 ( Fig. 2 , Tab I)

Synonymy. Rhabderemia coralloides ; sensu Burton, 1940: 116 (not Dendy, 1924). R. uruguaiensis Van Soest & Hooper, 1993: 329 .

Material studied. MNRJ 2849 H, 2857, 2866, 4658, station 6681, 25º11.005´S – 44º56.6´W, off Ilhabela (São Paulo State), 168m depth, collected by N. Oc. Prof. W. Besnard, 12 January 1998 . MNRJ 5061 , station 6686, 25°36.988´S – 45°13.571´W, off Bertioga (São Paulo State), 153m depth, collected by N. Oc. Prof. W. Besnard, 13 January 1998 .

Diagnosis. Rhabderemia uruguaiensis possesses rhabdostyles which are frequently smaller than 150µm as well as frequently larger than 300µm, and microscleres which are a single category of microstyles smaller than 100µm and small spirosigmata always smaller than 15µm.

Description. The species is represented in the collection by a series of very small fragments, the larger of which measures 32 x 4 x 1 mm (length x width x thickness — Fig. 2. a ). The fragments are thin and encrusting. The surface is hispid and irregular. Consistency slightly flexible. Oscules not aparent. Whitish colored in alcohol.

Skeleton. Ectossomal skeleton unspecialized, with large numbers of microscleres intermingled within the brushers of rhabdostyles. Inhalant pores (ca. 45mm in diameter) are visible here and there surrounded by large numbers of spirosigmas, and fewer microstyles, which may also pierce the pores. Choanosomal skeleton dense, confused, short bundles of rhabdostyles barely discernible, with rhabdostyles disposed in a plumose fashion some of them at nearly right angles to the bundle. Rhabdostyles can also be seen strewn randomly. Microscleres abound everywhere ( Fig 2. b ).

Spirosigmas. Megascleres: Rhabdostyles ( Figs. 2. c, 2. d ) — the base is curved and smooth, and the shaft is lightly spined; 98–429 in length, by 5–19µm thick. Microscleres: Microstyles ( Figs. 2. e, 2. f ) — one category, thin, entirely and heavily spined. The thorns are big and very sharp; 25–53 in length, by 0,5–2µm thick. Sigmata ( Fig. 2. g ) — very small, and heavily spined (big and sharp thorns); 5–10µm in length.

Ecology. Collected on soft sediment.

TABLE I: Rhabderemia uruguaiensis Van Soest & Hooper,1993 . Micrometric data for the specimens studied here (in micrometers).

Remarks. The only aspects where our specimens were found to differ from those reported by Van Soest & Hooper’s (1993) original description were on their possession of a single, rather than two categories of rhabdostyles (cf. Fig. 3 ), as well as on their possession of microstyles which can be as small as 25µm, as opposed to microstyles larger than 43µm in Van Soest & Hooper (1993). These differences were considered minor and both populations adjacent distribution was taken as further good grounds on which to postulate their conspecificity.

Figures

FIGURE 2. Rhabderemia uruguaiensis Van Soest & Hooper, 1993. (A) Preserved specimen; (B) Skeleton arrangement; (C) Rhabdostyle; (D) Smooth base of rhabdostyle; (E) Microstyles; (F) Spined base of microstyles; (G) Small spirosigma. Scale bars: A, 1cm; B, 200µm; C, 50µm; D– E,10µm, F–G, 1µm.

FIGURE 3. Distribution frequency of the size­classes of the rhabdostyles of the Brazilian Rhabderemia uruguaiensis (MNRJ 4658).