Halicometes stellata ( Schmidt, 1870 )

Van, Rob W. M., 2017, Sponges of the Guyana Shelf, Zootaxa 1, pp. 1-225 : 178

Halicometes stellata ( Schmidt, 1870)

Figures 111 a–h

Cometella stellata Schmidt, 1870: 49 .

Tethya caudata Deszö, 1879: 648 .

Tethya cometes Schmidt, 1879: 78 .

Tethya stellata ; Sollas 1888: 440.

Halicometes stellata ; Topsent 1898: 112; Topsent 1920: 31; Sarà 2002: 253, fig. 5. (Not: De Laubenfels 1950: 99, fig. 45; Little 1963: 56 = Timea spec.)

? Halicometes minuta Sarà & Rosa de Barboza, 1995: 167 , figs 1–4.

Material examined. RMNH Por. 9858 (including slide), Suriname, ‘ Luymes O.C.P.S. II’ Guyana Shelf Expedition, station K102, 7.1883°N 54.3833°W, depth 81 m, bottom grey-green mud, 18 April 1969 (2 specimens) .

Description. Small oval bodies on a long thin stalk ( Fig. 111 a). Only one small complete specimen, now entirely enclosed in Canada balsam on a microscope slide, with body 8 x 6 mm and stalk of 22.5 x 1 –1.5 mm. A second incomplete specimen (without stalk), slightly larger body (9 x 7 mm), with yellowish color in alcohol. Both have the body covered in hispid tubercles.

Skeleton. The skeleton of the body has an outer layer of micrasters, 0.2–0.5 mm thick, carried by bundles of styles separated by masses of megasters 2 mm in thickness. The bundles of styles number 20 or more spicules, 150–300 µm in thickness, and are separated at 0.5–2 mm distance. The center and lower half of the body contains a thick bundle of styles, a continuation of the stalk, and scattered megasters, oxyasters and micrasters. The stalk has a center column of styles, strengthened by individual megasters, a sheath of exotyles and a thin cover of micrasters.

Spicules. ( Figs 111 b–h) Styles/strongyloxeas, exotyles, megasters, oxyasters, micrasters.

Styles, in the form of strongyloxeas as usual for Tethyidae , fusiform, with narrow blunt heads, widened shafts and bluntly pointed or rounded thin endings, smooth, in two size classes, (1) long and thick ( Figs 111 b,b1), 1026– 1315 – 1596 x 15 – 21.0 –28 µm, and (2) shorter and thinner ( Figs 111 c,c1), 489– 641 –751 x 3 – 6.2 –8 µm.

Exotyles ( Figs 111 d,d1), in the form of tylostyles with quite diverse malformed heads and thin straight shaft, only a few could be measured entirely, 190–360 x 1–3 µm.

Megasters ( Figs 111 e,e1), shaped as smooth oxyspherasters, quite variable in size and number of rays, 36– 106 –195, with ray number 4– 14.6 –21, RC index (ray length divided by center diameter) 1.78.

Oxyasters ( Fig. 111 f), with irregular shape and few conical rays, 24– 49 –66, ray number 3– 4.4 –7.

Micrasters ( Figs 111 g,g1,h), variable in shape and ornamentation, predominantly strongylaster- or tylaster-like ( Fig. 111 g), with smooth center and finely spined blunt rays, younger/smaller forms with more pointed rays and few spines ( Figs 111 g1,h), 5– 10.6 –15 µm, ray number 7– 9.4 –13.

Distribution and ecology. Guyana Shelf, Gulf of Mexico, depth range 81–650 m ( Guyana Shelf 81 m).

Remarks. The specimens described above conform in all aspects to the redescription of the type material in Sarà, 2002 (p. 253), originally reported from the Gulf of Mexico . De Laubenfels’ (1950) record from Bermuda, and Little’s (1963) record from Florida are both obviously erroneous and concern the genus Timea , likely Timea hechteli Lehnert & Heimler, 2001 . The description of Halicometes minuta Sarà & De Rosa Barboza, 1995 from the Brazilian SE coast is also very similar to our material. The differences of that ‘species’ with the type of Halicometes stellata appear to be negligible (it concerns the length of the megascleres and robustness of the megasters). Our material appears to be inbetween the two alleged species.

A slide made of one of the type specimens (USNM 22368) of Halicometes thyris ( De Laubenfels, 1934) (originally Tethycordyla ) from Puerto Rico was examined. The species has similar megasters (size, shape) as H. stellata , the micrasters are similar in shape (tylaster-like) but somewhat larger (12–28 µm), the styles are larger (2500–3000 µm for the large ones, 1000 µm on average for the smaller ones), no irregular oxyasters and exotyles were observed. These observations preclude synonymization of H. thyris with H. stellata .

Halicometes perastra De Laubenfels, 1936 from Florida is not a Halicometes , nor a tethyid, as it possesses tylostyles and tylasters. It has been transferred to Timea by Hechtel (1969), but this is uncertain. Possibly, it belongs to the stelligerid genus Adreus Gray, 1867 .

Figures

FIGURE 111. Halicometes stellata (Schmidt, 1870), a, light microscopic image of habitus of RMNH Por. 9858 (scale bar = 1 cm), b – h, SEM images of the spicules, b, large style / strongyloxea, b 1, details of b, c, small style / strongyloxea, c 1, detail of c, d, exotyle, d 1, detail of d, e, megasters, e 1, megasters with low ray number, f, irregular oxyaster with conical rays, g, micraster / tylaster, g 1, smooth micraster, h, tiny micraster.