Rhabderemia besnardi, Oliveira & Hajdu, 2005

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 : 6-7

Rhabderemia besnardi sp. nov. ( Fig. 4 )

Material studied. Holotype: MNRJ 3184 , 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 besnardi sp. nov. is the only species in the genus with rhabdostyles as large as 400µm, two size categories of acanthomicrostyles which can be larger than 150µm long, and small spirosigmata.

Description. The species is represented in the colletion by seven fragments, the largest of which measures 24 x 1 x 1,5 mm (length x width x thickness — Fig. 4. a ). Encrusting. Surface is irregular and hispid. Consistency is slightly flexible. Oscules not apparent. Beige colored in alcohol.

Skeleton. Ectossomal skeleton unspecialized, with large numbers of microscleres intermingled within the brushes of rhabdostyles. Choanosomal skeleton composed of plumose bundles of rhabdostyles which do not ramify or anastomose. Rhabdostyles projecting from these bundles form a confused pseudoreticulation. Bundles terminate in brushes near the surface. Microscleres abound everywhere, with microstyles as the most distinctive feature. In places where contact with the substrate is visible, a hymedesmioid arrangement of rhabdostyles stemming from a basal plate of spongin is visible ( Fig. 4. b ).

Spirosigmata. Megascleres: Rhabdostyles ( Figs. 4. c, 4. d ) — the shaft is lightly spined and the base is smooth, and curved; 107 – 238,2 – 417µm in length, by 5 – 12,0 – 24µm thick. Microscleres: Microstyles I ( Figs. 4. e, 4. f ) ­ larger, entirely and heavily spined (the concentration of thorns is greater at the base), thorns big and very sharp; 137 – 155,5 – 172µm in length, by 2 – 2,5 – 3µm thick. Microstyles II – smaller, entirely and heavily spined (the concentration of thorns is greater at the base); 37 – 45,1 – 51µm in length, by 1 – 1,5 – 2µm thick. Sigmata ( Fig. 4. g ) — very small, and heavily spined (big and sharp thorns); 5 – 7,5 – 10µm in largest diameter.

Ecology. Collected on soft sediment.

Etymology. The species is named after the oceanographic ship on board of which it was collected, viz. N.Oc. "Prof. W.Bernard" of the Oceanographic Institute of Universidade de São Paulo.

Remarks. Rhabderemia besnardi sp. nov. differs from other species of the genus with two categories of microstyles by its larger and considerably stouter rhabdostyles (up to 24µm thick, as opposed to a maximum of 6µm thickness in R. bistylifera Lévi, 1961 and 7µm in R. africana Van Soest and Hooper, 1993 ), and microstyles I which can be larger than 150µm long.

Figures

FIGURE 4. Rhabderemia besnardi sp. nov. (A) Preserved specimen; (B) Skeleton arrangement; (C) Rhabdostyle; (D) Smooth base of rhabdostyle; (E) Microstyle; (F) Spined base of microstyle and a small spirosigma; (G) Small spirosigmata. Scale bars: A, 0,5cm; B, 200µm; C, 50µm; D–F, 10µm; G, 1µm.