Penares sineastra, Van, Rob W. M., 2017

Van, Rob W. M., 2017, Sponges of the Guyana Shelf, Zootaxa 1, pp. 1-225 : 92-93

Penares sineastra sp. nov.

Figures 57 a–e

Material examined. Holotype RMNH Por. 9735, Suriname, ‘Luymes’ Guyana Shelf Expedition, station 38, 7.2833°N 53.95°W, depth 100 m, bottom shell gravel, trawl, 28 August 1970 .

Description. Thin branch fragments ( Fig. 57 a) with smooth but irregular surface, possibly part of a group of branches but this cannot be determined with certainty. Nevertheless it is here proposed to treat the fragments as part of a single holotype. Color in alcohol cream or pale beige. No obvious apertures are visible. Largest fragment is approximately 5 cm long and has a greatest diameter of 8 mm, other fragments are thinner or thicker, up to 1 cm thick. Three of the four branch fragments are encrusted by small hydroids. The interior of the sponge is not entirely hollow but is ‘cavernous’ with elongated open spaces; inside it has the same color as outside. Consistency compressible.

Skeleton. The surface skeleton is a crust, thickness 40–150 µm in cross section, of microrhabds of various sizes forming a dense reticulation around small rounded apertures approximately 50–100 µm in diameter. The crust of microrhabds is carried by the cladomes of individual triaenes and bundles of oxeas. The choanosome has large lacunae of 0.5–1 mm in diameter flanked by axially directed bundles and sheets of oxeas. Diameters of these bundles vary between 200 and 300 µm.

Spicules. ( Figs 57 b–e) Oxeas, dichotriaenes, orthotriaenes, microrhabds. No asters.

Oxeas ( Figs 57 b,b1), fusiform, often curved, with sharp or more often bluntly rounded endings, in a large size range, possibly with two overlapping size categories, larger (700–1263 µm) and smaller (354–700 µm), overall size 354– 801 – 1263 x 8 – 21.5 –34 µm.

Dichotriaenes ( Figs 57 c,c1), with rhabdomes pointed and cladus length approximately the same, with primary cladi longer than secondary cladi; rhabdome sizes 282– 321 –336 x 28 – 31.2 –39 µm, cladomes 426– 527 –612 µm, primary cladi 164– 187 –207 x 22 – 30.4 –37 µm, secondary cladi 37– 98 –184 x 12 – 21.9 –32 µm.

Orthotriaenes ( Figs 57 d,d1), few in number, always smaller than the dichotriaenes, several occur with one of the cladi bifid, from which it is concluded these are in fact juvenile stages of the dichotriaenes, not a separate spicule type.

Microrhabds ( Figs 57 e–e3), oxea-like with pointed ends which are microspined in adult condition, overall 42–246 x 2.5–12 µm, divisible rather arbitrarily in three (or four) overlapping size categories, (1) large ( Figs 57 e,e1,e1a), 141– 182 –246 x 6.5– 9.4 –12 µm, (2) middle-sized ( Figs 57 e2,e2a) 63– 80 –102 x 3.5– 4.8 –5.5 µm, and (3) small ( Fig. 57 e3), 42– 49 – 54 x 2.5– 3.4 –4 µm.

Distribution and ecology. Guyana Shelf, on shell gravel bottom, at 100 m depth.

Etymology. The species name is a composite noun combining the words sine (L. = without) and astrum, plural astra (L.), referring to the absence of aster microscleres in this species.

Remarks. The characteristic features of the new species are the fistule-like shape and the absence of aster microscleres. Among the Western Atlantic Penares species none have been reported to lack aster microscleres. P. hartmeyeri ( Uliczka, 1929) from Barbados is encrusting, has only orthotriaenes, no dichotriaenes, and oxyasters. P. mastoidea ( Schmidt, 1880) (as Stelletta ) from Grenada, re-described by Topsent (1923) (p. 9), and reported from Barbados by Van Soest & Stentoft (1988) (p. 29), is lobate, has very much longer oxeas (up to 3 mm), rare dichotriaene modifications of the orthotriaenes, and large acanthoxyasters. P. chelotropa (cf. above) and P. anisoxia Boury-Esnault, 1973 do not have dichotriaenes and possess oxyasters.

Elsewhere, there are eight Penares species sharing the lack of aster microscleres with the new species: Mediterranean P. candidata ( Schmidt, 1868) (p. 18, pl. IV fig. 19, originally as Papyrula ), Australian P. ochracea ( Carter, 1886) (p. 458, originally as Pachamphilla ), Japanese P. hilgendorfi Thiele, 1898 (p. 18, pl. 5 fig. 1, pl. 7 figs 9–10, originally as Ecionemia ), South East African P. alata ( Von Lendenfeld, 1907) (p. 195, pl. 39 figs 14–25, originally as Pachamphilla ), Californian P. saccharis De Laubenfels, 1930 ( 1932, p. 37, fig. 16, originally as Papyrula , also reported from the Galapagos Islands by Desqueyroux-Faúndez & Van Soest 1997, p. 394) and New Caledonian P. palmatoclada Lévi, 1993 (p. 16, fig. 2C, originally as Papyrula ). South African P. sphaera ( Von Lendenfeld, 1907) (p. 227, pl. XXXVII figs 24–35, pl. XXXVIII fig. 1, originally as Papyrula ) and Indonesian P. dendyi ( Hentschel, 1912) (p. 308, pl. 13 fig. 5, pl. 17 fig. 3, originally as Pachamphilla ) share dichotriaenes and the absence of aster microscleres with these species, but they do have microscleres in the form of small spheres (which may under SEM turn out to be asters after all). For all these aster-lacking Penares species, the genus Papyrula Schmidt, 1868 is available. Most species of this ‘group’ also share the possession of dichotriaenes, but that is where the shared features end: there are large differences among these species in the shape of the body, and the sizes of the megascleres, overlapping with the remaining species of Penares . So far no molecular evidence is available to indicate the lack of asters is a genuine synapomorphy. Thus, the synonymy of Penares and Papyrula appears well supported.

The presence of spines on the microrhabd apices reminds of those of Erylus rhabdocoronatus sp. nov. described above. It strengthens the bond between Erylus and Penares , which is based primarily on molecular studies ( Cárdenas et al. 2010). Tangential surface sections of many Penares species are very difficult to differentiate from such sections from Erylus species, especially in the case of E. deficiens Topsent, 1927 . A rearranged generic composition of the subfamily Erylinae may be necessary in which the distinction between these two genera should be reconsidered.

Figures

FIGURE 57. Penares sineastra sp. nov., a, habitus of fragmented holotype RMNH Por. 9735 (scale bar = 1 cm), b – e, SEM images of spicules, b, oxea, b 1, detail of b, c, dichotriaenes, c 1, anomalous dichotriaene, d, orthotriaene, d 1, anomalous orthotriaene, e, large microrhabd, e 1, smaller version of e, e 1 a, detail of spined apex of e 1, e 2, intermediate microrhabd, e 2 a, detail of spined apex of e 2, e 3, smallest microrhabd.