Thrinacophora melae sp. nov.

(Figs. 6 and 7, Table 3)

Material examined. Holotype. MZUSP 479 (Schizoholotype 13°57’33”S 38°59’51”W MUCIN 0150). Brazil. Bahia State, Maraú, Camamu Bay, Coroa das Ilhas, 13°57’33”S 38°59’51”W, 23.x.2012, 2–3 m, Coll. C. Menegola, Det. A. Ozga & C. Menegola.

Additional Material. BRAZIL Thrinacophora funiformis Ridley & Dendy, 1886. MUCIN 0143. Bahia State, Salvador, Praia de Piatã, 12°57’27”S 38°22’47”W, 0.5–2.0 m depth, Coll. W. Andrade, 1986, Det. C. Menegola, 13.ix.2019.

Diagnosis. Megascleres are strongyles and three categories of styles. Microscleres raphides are clustered in trichodragmata.

Description. Arborescent with cylindrical branches, irregular sponge with dimensions (6 x 3.7 cm (length x width)). Conulose and hispid, with spicule projections of long styles. Flexible and elastic consistence. Oscules and pores not visible. Yellow color in situ (Fig. 6A). Upon preservation (Fig. 6B), turns light beige.

Skeleton. Subectosomal skeleton consisting of styles I and II, with projections from the center of the choanosome to the subectosome. Styles II form a kind of lattice at the base of styles I. Styles II, styles III and raphides in trichodragmata form several lamellar layers arranged in ascending order from the center of the choanosome to the ectosome (Fig. 6C). Translucent ectosomal skeleton with pigmented pinacoderm, measures 50 to 200 µm wide and consisting of echinate bouquets of styles II (Fig. 6D), also present styles III (Fig. 6E) randomly distributed. Choanosomal skeleton formed by strongyles tracts arranged horizontally or obliquely in a three-dimensional structure.

Spicules. One kind of strongyles, three kinds of styles and one kind of raphides (Fig. 7A–N; Table 3).

Strongyles (Fig. 7A–D)—Long or short, thin or thick, straight or slightly curved at the center, with the ends varying from rounded to telescopic: 175–460.8–1125/ 72.5–9.1–15 µm. Styles I (Fig. 7E–G)—Long and thick with pointed and/or rounded ends: 875–1177.5–1400/ 7.5–11.3–17.5 µm. Styles II (Fig. 7H–J)—Long and thin, smooth and straight, with one end rounded and the other sharp: 250–776–1350/ 2.5–4.3–10 µm. Styles III (Fig. 7K and L)—Short and thick, spined with an accumulation of juxtaposed spines directed towards the center of the spicule and with a crown of spines at the end. Pointed tips, rarely rounded: 92.5–153.4–177.5/ 5–7.8–10 µm. Raphides (Fig. 7M and N)—Short and thin, straight with rounded ends: 250–344.3–450/ 1–1.6–3 µm

Ecology and bathymetry. Sandy bottom with biodetritic debris (shell and carapace fragments, calcareous nodules, etc.) at 2–3 m deep.

Distribution. Southwest Atlantic, Brazil. Only known from the type locality.

Etymology. This species is dedicated to Mel, the cute and unforgettable basset hound who was our inseparable friend during the manuscript writing, with her loud and happy barks, her unconditional love, and who passed away shortly before the submission of this paper.

Remarks. Thrinacophora melae sp. nov. differs from the other species of the genus by having strongyles, not documented in the literature so far, therefore requiring the redefinition of the genus Thrinacophora for its inclusion. Other similarities are the presence of styles I and raphides in both species. However, both species differ mainly in the occurrence of strongyles and styles (three categories) in Thrinacophora melae sp. nov. and of oxeas and styles (two categories) in T. funiformis.

Comparing the species Thrinacophora melae sp. nov. with T. murrayi Arnesen, 1920 and T. spinosa Wilson, 1902, which also occur in the Western Atlantic, the presence of strongyles and styles III exclusive to the new species is a notable difference. Thrinacophora melae sp. nov. and T. dubia Brøndsted, 1924, which occurs in the Western Pacific (Auckland and Campbell Islands, New Zealand) are the only two species to share spined styles III, but differ by the presence of strongyles and styles II in the former.

Studies on the genus are scarce, such as Hooper (1991) who carried out a review of the family Raspailiidae but, with regard to Thrinacophora, considered only the species T. cerviconis Ridley & Dendy, 1886. Hooper (2002) defines Thrinacophorinae, redescribing in his study only T. funiformis, which is also registered by Rützler et al. (2009) and Van Soest (2017) for the Northern Gulf of Mexico) and Guyana / Suriname, respectively.

Thrinacophora melae sp. nov. increased the number of species described for the Atlantic Ocean to four, with T. funiformis and Thrinacophora melae sp. nov. now registered for Brazil, highlighting here an additional specimen of T. funiformis (MUCIN 0143) from the type locality (Salvador, Bahia).