Stelletta crassispicula ( Sollas, 1886 )

Van, Rob W. M., 2017, Sponges of the Guyana Shelf, Zootaxa 1, pp. 1-225 : 70-75

Stelletta crassispicula ( Sollas, 1886)

Figures 45 a–f, 46a–i, 47a–f

Pilochrota crassispicula Sollas, 1886: 190 ; Sollas 1888: 128, pl. XIV figs 9–15.

Stelletta crassispicula ; Topsent 1922: 1; Muricy et al. 2011: 43.

Myriastra anancora ; Boury-Esnault 1973: 270, pl. I figs 6–7, text-fig. 8 (not Pilochrota anancora Sollas, 1886 )

Stelletta anancora ; Burton 1954: 220; Hajdu et al. 2011: 74; Muricy et al. 2011: 42, fig. 5H. (Not: Stelletta anancora sensu Van Soest & Stentoft 1988: 26 , pl. IV fig. 3, text-fig.10).

Material examined. RMNH Por. 9298, Suriname, ‘ Snellius O.C.P.S. ’ Guyana Shelf Expedition, station F38, 7.23°N 56.4067°W, depth 81 m, 5 May 1966 ; RMNH Por. 9335, French Guyana, ‘Luymes’ Guyana Shelf Expedition, station 14, 6.7333°N 52.75°W, depth 76 m, bottom muddy calcareous sand, 26 August 1970 ; RMNH Por. 9337, Guyana, ‘Luymes’ Guyana Shelf Expedition, station 107, 7.7°N 57.5°W, depth 65 m, muddy sand bottom with shells, 5 September 1970 ; RMNH Por. 9813, Guyana, ‘Luymes’ Guyana Shelf Expedition, station 68, 7.4167°N 57.1333°W, depth 51 m, muddy sand bottom, 31 August 1970 ; RMNH Por. 9831, Guyana, ‘Luymes’ Guyana Shelf Expedition, station 87, 7.5667°N 57.2667°W, depth 59 m, bottom sand and shells, 2 September 1970 ; RMNH Por. 9862, Suriname, ‘ Snellius O.C.P.S. ’ Guyana Shelf Expedition, station F40, 7.0033°N 56.4417°W, depth 59 m, bottom sand, 6 May 1966 ; RMNH Por. 9888, 9889, 9903, Suriname, ‘ Snellius O.C.P.S. ’ Guyana Shelf Expedition, station G7, 7.28°N 56.7933°W, depth 64 m, bottom sand, 7 May 1966 .

Description. Globular to semiglobular sponges ( Figs 45 a, 46a–i), regularly rounded or more bumpy in outline. Color variously white, dirty white, red- or purple-brown in alcohol, but these colors also occur in various on-deck photos of specimens obtained in French Guyanan waters by the CREOCEAN expedition. Surface covered sparingly or more frequently by foreign objects such as shells or pieces of corals and bryozoans. Occasionally entirely smooth. Surface punctate to irregular, not hispid or rough. Size up to 10 cm in diameter. In cross section a clear white-colored cortex of 4–5 mm in thickness is visible; the choanosome is darker colored pale purple or dirty white.

Skeleton. Radiate, with long oxeas and rhabds of triaenes forming a strong palisade in the cortical region. Subcortically, there are regular spaced regions with tissue and microscleres, created by the shorter rhabds of the plagiotriaenes 2, separated by longer rhabds of the plagiotriaenes 1 and oxeas. Further down into the skeleton the radiate bundles become less distinct.

Spicules. ( Figs 45 b–f, 47a–f) Oxeas in two categories, plagiotriaenes in two categories, acanthotylasters.

Oxeas 1 ( Figs 45 b,b1), anisoactine, with one end thinly tapering and the opposing end mucronate, often broken in the slides (n=4), 2700–4200 x 19–25 µm.

Oxeas 2 ( Figs 45 c,c1), symmetrical, fusiform, slightly curved, 1590– 1920 –2120 x 24– 37 –57 µm.

Plagiotriaenes 1 ( Figs 45 d,d1), variably shaped, with rather long, straight or more often somewhat incurved cladi (approaching protriaene condition) or curved outward (approaching orthotriaene condition), and with the rhabd slightly constricted underneath the cladome, then tapering gradually to a sharp end; rhabdome 1820– 2090 –2640 x 70 – 78 –84 µm, cladi 186– 224 –294 x 42 – 49 –61 µm.

Plagiotriaenes 2 ( Figs 45 e,e1), more uniformly short- and straight-claded, rhabd similarly slightly constricted near the cladome, usually sharply pointed; rhabdome 330– 451 –576 x 13– 24 –29 µm, cladi 20– 51 –74 x 12– 19 –23 µm.

Tylasters ( Fig. 45 f), with smooth or sparingly spined rays and heavily spined tyles, variable in ray thickness and ray number; overall sizes 12– 14.4 –18 µm, ray number 5– 7.2 –9.

Distribution and ecology. Guyana Shelf, NE Brazil (see all records in Muricy et al. 2011), possibly Cape Verde Islands, on sandy bottoms, at 23–81 m depth ( Guyana Shelf 51–81 m).

Remarks. The Central West Atlantic region harbors a number of described Stelletta species that appear very closely related, making it difficult to identify a given specimen. Their common characters are the possession of plagiotriaenes in combination with tylasters, accompanied by one or two oxea types and rare or absent anatriaenes. These are in particular Stelletta fibrosa ( Schmidt, 1870) (as Ancorina ), Stelletta anancora , Stelletta crassispicula and Stelletta gigas , all three authored by Sollas, 1886 (as Pilochrota ), Stelletta variabilis and globulariformis , both authored by Wilson, 1902 (as Pilochrota ), Stelletta incrustata Uliczka, 1929 , Stelletta kallitetilla ( De Laubenfels, 1936) (as Myriastra ), Stelletta soteropolitana Cosme & Peixinho, 2007 , and Stelletta spec. sensu Cárdenas et al. 2009. The species descriptions are predominantly single specimen descriptions as is common in sponge taxonomy, and the extent of character variation is usually not known. In the present case, I am fortunate in having before me ten similar specimens, from nine stations spread over the full breadth of the Guyana shelf, presumably of the same species, all recognizable as globular individuals with large central vent, a surface encrusted by one or more shell- and coral-fragments, and having a color in alcohol varying from whitish to purple-brown. It is possible that the purple-brown color is not natural to the sponges, as in one case at least it was collected in combination with a verongid specimen, which is known to cause purple discoloration of objects preserved together with it.

In these ten specimens we note the following variation in characters:

Size of the body: 3–10 cm diameter (see Figs 46 a–i for an overview of the habits of nine of the specimens).

Variation in vents: smaller individuals have a single opening, 5–15 mm in diameter, larger individuals of 8–10 cm may have an additional vent.

Variation in smooth outline or more bumpy.

Variation in color from whitish to purple-brown.

Spicule complement: little variation, always with two categories of oxeas, two categories of plagiotriaenes, no anatriaenes have been observed in any of the specimens, a single but quite variable category of tylasters.

Size of oxeas 1: 2.7–4.5 mm x 20–42 µm.

Size of oxeas 2: 1.5–2.3 mm x 24–84 µm.

Size of plagiotriaenes 1: 1.2–4.0 mm x 42 –85 µm.

Size of plagiotriaenes 2: 330–600 x 12–25 µm.

Shape of cladome of plagiotriaene 1 (see Figs 47 a1–f1): quite variable within and among the specimens: cladi straight, incurved, somewhat recurved, backcurved, or occasionally flaring upwards and outwards. The difference with pro- and orthotriaenes becomes debatable in these spicules.

Shape of cladome of plagiotriaene 2 (see Figs 47 a2–f2): much more uniform, usually straight with conical cladi, frequently also slightly incurved.

Tylasters, quite variable (see Figs 47 a3–f3) diameter: 8–18 µm, sometimes appearing in two overlapping sizes; ray thickness: 0.7–2.5 µm;

Spination of tylasters: usually smooth rays, with heavily spined apices, often with a few spines on the shaft of the rays.

We identify these ten specimens with Sollas’ (1886) Pilochrota crassispicula . This is described as a greyish white globular sponge, with a spicule complement of two categories of oxeas (fusiform and thin-anisoxeote), plagiotriaenes with conical cladi, a thick rhabdome with thinly tapering shaft, a cladome with incurved cladi, and quite variable tylasters, suggested to occur in a smaller and larger form, 12–19 µm in diameter. The oxea- and plagiotriaene sizes cited by Sollas are single measurements, but these are close to the sizes presented here above, especially the thickness of the plagiotriaenes. Other, closely related forms, Stelletta gigas and Stelletta anancora described by Sollas from the same general region differ in that respect from S. crassispicula . Sollas cites for S. anancora oxeas only 23 µm in thickness, for S. crassispicula he gives 51 µm. Likewise, he cites for anancora plagiotriaene rhabdomes a thickness of 27 µm, and for crassispicula 79 µm. The measurements for our specimens are clearly closer to those of S. crassispicula than to S. anancora , although the possibility that these two ‘species’ are merely extremes of a variable single species cannot be excluded.

Topsent (1922) compared specimens from the Cape Verde Islands with Sollas’ description of Stelletta crassispicula . According to him, the only consistent difference between specimens from both sides of the Atlantic is the (rhabdome) size of the plagiotriaenes, the Cape Verde specimens having larger (longer and thicker) plagiotriaenes than the Brazilian specimens, a difference not meriting specific separation in his opinion. For that reason he also synonymized Lendenfeld’s (1907) Cape Verdian species Stelletta crassiclada with S. crassispicula . Topsent’s (1922) choice of Stelletta crassispicula may be interpreted as the action of a First Revisor in the sense of the ICZN. In line with this, Burton (1954) synonymized all Central Atlantic Stelletta species of Sollas under a single species, but unwisely insisted that Stelletta anancora Sollas, 1886 had to be the valid name for the synonymized species, instead of following Topsent, arguing that S. anancora was the first species mentioned by Sollas in the 1886 paper. This is weakened by the fact (1) Topsent chose to use Stelletta crassispicula , and if that would turn out to be synonymous with S. anancora , there would be no reason to choose that name in preference to crassispicula , and (2) that Sollas treated S. anancora later in the 1888 monographic Challenger report with the proper extensive descriptions and illustrations. Burton did not attempt a close comparison of the descriptions of all the species concerned ( S. anancora , S. crassispicula , S. gigas , S. tenuispicula , and S. crassiclada Lendenfeld ), merely stating they are all the same species. This cannot be considered an action of First Revisor in the sense of the ICZN.

Boury-Esnault (1973) regrettably followed Burton’s nomenclature and assigned Brazilian material to S. anancora (as Myriastra ), but judging from the spicule sizes, it is likely that her specimens were conforming to S. crassispicula as understood here. Hajdu et al. (2011) reported the occurrence of S. anancora from NE Brazil, likewise probably conforming to our material, but the drawing of oxyasters provided by these authors casts doubt on this. Muricy et al. (2011) pictured Burton’s S. anancora ( Fig. 5 H), but like Burton did not provide a description of skeleton and spicules. Likewise, Díaz & Zea (2008: fig. 4, right) pictured Stelletta specimens similar to S. crassispicula as Stelletta fibrosa var. globulariformis Wilson, 1902 , but did not provide spicule size data.

Van Soest & Stentoft’s (1988) Barbados record of Stelletta cf. anancora is certainly not conforming to the present material, nor to S. anancora sensu Sollas , as it was reported to have orthotriaenes and the asters are strongylasters, definitely not tylasters.

A slide made from the holotype (MNHN D.NBE 1029) of Penares anisoxea Boury-Esnault, 1973 , from 50 m off NE Brazil, revealed—surprisingly—that the specimen belongs to Stelletta crassispicula . The ‘orthotriaenes’ and oxeas have the same shape as the above described and they occur in the characteristic radiate arrangement of the present species. The ‘microxeas’ cited by Boury-Esnault (1973) are few—not present in high quantities at the surface as is usual for Penares —and do not have the centrotylote shape. The microscleres are named oxyasters but this is difficult to confirm from the slide; the ends of the rays are not really sharply pointed and the sizes quoted conform to those of Stelletta crassispicula . The figured type specimen ( Boury-Esnault 1973: Pl. II fig. 3; see also Muricy et al. 2011: figs 5C–D) resembles the present Stelletta crassispicula material strongly, with its globular shape, single large central vent, and surface encrusted with shell fragments. There is also a striking similarity with Boury-Esnault’s depicted specimens of Myriastra anancora . It is more likely that this concerns a case of mislaid labels, than a genuine misidentification of the genus by Boury-Esnault.

Further Central West Atlantic Stelletta species with plagiotriaenes and tylasters, Stelletta fibrosa , S. variabilis , S. globulariformis , Stelletta incrustata Uliczka (1929) , Stelletta kallitetilla ( De Laubenfels, 1936) , S. soteropolitana and Stelletta spec. sensu Cárdenas et al. 2009, differ from the above described specimens in having clearly smaller (thinner and shorter) plagiotriaenes and oxeas, and lacking a differentiation in long/thin anisoxeas and thick fusiform oxeas. It remains to be decided which of the above-named Stelletta species are valid or are to be regarded as junior synonyms.

Figures

FIGURE 5. Aplysina caissara Pinheiro & Hajdu, 2001, RMNH Por. 9340, a, habitus (scale bar = 1 cm), b, light microscopic image of skeleton of pithed fibers.

FIGURE 45. Stelletta crassispicula (Sollas, 1886), a, habitus of RMNH Por. 9888 (scale bar = 1 cm), b – f, SEM images of spicules, b, oxea 1 (anisoxea), b 1, details of b, c, oxea 2 (fusiform oxea), c 1, details of c, d, plagiotriaene 1, d 1, cladome of plagiotriaene 1, e, plagiotriaene 2, e 1, cladome of plagiotriaene 2, f, acanthotylaster.

FIGURE 46. Stelletta crassispicula (Sollas, 1886), habitus images of various Guyana Shelf specimens, scale bars = 1 cm, a, RMNH Por. 9888, b, RMNH Por. 9813, c, RMNH Por. 9903, d, RMNH Por. 9889, e, RMNH Por. 9298, f, RMNH Por. 9337, g, RMNH Por. 9831, h, RMNH Por. 9335, i, RMNH Por. 9862.

FIGURE 47. Stelletta crassispicula (Sollas, 1886), SEM images showing variability of triaenes and tylasters in the various Guyana Shelf specimens, a 1 – f 1, cladomes of plagiotriaenes 1 of RMNH Por. 9888, 9813, 9903, 9298, 9335, 9862, a 2 – f 2, cladomes of plagiotriaenes 2 of ditto specimens, a 3 – f 3, tylasters of ditto specimens.