Desmacella tylovariabilis Cavalcanti, Santos & Pinheiro, 2015, sp. nov.

Desmacella tylovariabilis sp. nov.

(Figures 1, 3, Table 1)

Type locality: Brazil, Rio de Janeiro State, Campos Basin.

Type specimens: Holotype. MNRJ 7339, Campos Basin (22° 58’ S; 42° 1’W), Rio de Janeiro State, Brazil, 1130 m depth, dragging, coll. CENPES/ UFRJ, (07/II/2003).

Diagnosis. Desmacella tylovariabilis sp. nov. is the only Desmacella in the Tropical Western Atlantic with the combination of large tylostyles (616.0 x 11 µm, length x width) bearing rounded tyles in varied positions, and sigmas with microspined ends (34.2 µm, chord length).

External morphology (Fig. 3 A). Massive sponge, 6 x 4.5 cm (length x width) (Fig. 3 A). Hispid surface, without distinct oscules, fragile consistency and colour beige (fixed in ethanol).

Skeleton (Fig. 3 B). Ectosomal skeleton with plumose bundles of tylostyles. Choanosomal skeleton composed of a vaguely halichondrioid skeleton; poorly developed spongin fibres. Sigmas appear to be distributed randomly.

Spicules (Fig. 3 C–F). Tylostyles (315– 616.0 – 1050 x 6 – 11.0 –16 µm, length x width): long, thin and smooth, straight to slightly curved, rounded tyles situated at varied positions at their bases (Fig. 3 C, D); Sigmas (25– 34.2 – 48 µm, chord length): thin, abundant and microspined ends (Fig. 3 E, F).

Distribution (Fig. 1). Brazil: Southeastern Region: Rio de Janeiro State: Campos Basin.

Etymology. The specific epithet tylovariabilis refers to the variation observed on the tyles of the tylostyles, tylo = from the Greek tyle, meaning knob or lump, and varius = from the Latin, meaning different or various.

Remarks. Desmacella tylovariabilis sp. nov. is assigned to the genus because of its tylostyles and sigma spicules, and vaguely halichondrioid skeleton formed by large tylostyles. There are four species similar to D. tylovariabilis sp. nov.: D. grimaldii, D. informis, D. inornata and D. topsenti. They occur in the North Atlantic Ocean, and have similarities regarding spicule dimensions (see Table 1). However, the above species differ from D. tylovariabilis sp. nov. which has rounded tyles situated at varied positions at their bases. The new species differs from D. annexa, D. digitata, D. polysigmata, D. pumilio and D. vicina, by the presence of only one category of sigmas. Desmacella tylovariabilis sp. nov. is distinguished from D. infundibuliformis, D. jania, D. meliorata, D. vagabunda and D. vestibularis, by the new species’ larger tylostyles and sigmas (see Table 1). Desmacella corrugata differs from the new species by the different morphology of its megascleres. Additionally, the new species differs from D. suberitoides as that species presents two categories of tylostyles. Finally, D. tylovariabilis sp. nov. has massive growth form and larger spicules than those of D. microsigmata sp. nov. (Table 1).