Sycettusa stauridia (Haeckel, 1872)

Figs 75a–f, 76a–f

Djeddea violacea Miklucho-Maclay in Haeckel, 1872: 245 (nomen nudum).

Sycetta (Sycettusa) stauridia Haeckel, 1872: 236, 245, pl. 42 figs 13–16.

Grantessa stauridia; Lévi 1965: 26.

Material examined. ZMA Por. 0 2460, Eritrea, Dahlak Archipelago, Harmil Island, Red Sea, 16.5167°N 40.15°E, depth 1 m, scuba, coll. J.H. Stock, Israel South Red Sea Exped. 1962, field nr. E62-10418, 28 March 1962 ; ZMA Por. 13664, Israel. Gulf of Aqaba, containerport, on pillar, depth 5 m, scuba, coll. M. Wunsch, field nr. AQ68, 5 July 1998 .

Description. Masses of small hollow lobes and tubes (Figs 75a–c). Surface faintly roughened, not smooth. Color in situ greyish blue to light red-brown, in alcohol both samples are red-brown. Size of whole mass up to 6 x 8 cm, individual tubes and lobes up to 1.5 cm high 1 cm in diameter or smaller. Oscules are frequently absent from the top of the hollow lobes, as they may be at the sides or in the interstices, and are not common. They do not have observable collars or fringe and have a diameter up to 0.5 cm.

Aquiferous system. Syconoid.

Skeleton. (Figs 75d–f) As usual, there is a cortical skeleton of triactines (Fig. 75e), an inarticulated choanosomal skeleton (Fig. 75d) formed by the longer paired actine of subectosomal triactines and the unpaired actines of subatrial triactines, and an atrial skeleton (Fig. 75f) of tangential triactines. Rare diactines and trichoxeas.

Spicules. (Figs 76a–f) Diactines, trichoxeas, cortical triactines, pseudosagittal triactines, large sagittal triactines, atrial triactines.

Diactines (Fig. 76a), fusiform, supporting the inarticulated skeleton in a low frequency, 269– 426 –541 x 15 – 16.6 –19 µm.

Trichoxeas (Fig. 76b), rare, probably associated with the oscules, 200–650 x 2–6 µm.

Cortical triactines (Fig. 83c), almost regular equiangular equiradiate, 177– 213 –255 x 10 – 14.0 –20 µm.

Pseudosagittal triactines (Figs 76d), longest actine 316– 406 –468 x 15 – 18.3 –23 µm, middle sized actine 171– 198 –234 x 15 – 17.3 –21 µm, shortest actine 108– 168 –201 x 15 – 16.9 –20 µm.

Subatrial triactines (Fig. 76e), many are almost T-shaped, unpaired actines 328– 423 –510 x 24 – 28.6 –32 µm, paired actines 241– 272 –336 x 22 – 23.7 –27 µm.

Atrial triactines (Fig. 76f), more ore less regular, actines 135– 159 –174 x 8 – 11.1 –13 µm.

Distribution and ecology. Red Sea, in shallow water.

Remarks. We follow Lévi (1965) in assigning the specimens to Haeckel’s S. stauridia, although his figure and description shows some discrepancies: Haeckel’s specimen apparently was much smaller and he provided a stylized drawing which shows a single central tube with a ring of side tubes. He did not mention the presence of diactines. However, they are not very common in our specimens, so he may have overlooked them. He did not

make a distinction in pseudosagittal subcortical triactines and sagittal subatrial triactines. The sizes he provided of these spicules are similar to those of the present specimens, as are those of the other spicules.

There are competing names, which are potential junior synonyms of this species. Mauritian Sycortis sycilloides Schuffner, 1877 (p. 420, pl. 25 fig. 10) has similar habitus (two coalescent small tubular individuals), but it has the unpaired actines of the subatrial triactines much longer and thicker (600–1000 x 80 µm) against Haeckel’s and ours only 400 x 10–20 µm. Red Sea Grantessa glabra Row, 1909 (p. 203, pl. 19 figs 5–6, text fig. 4a) is a small tube with side oscule and it has cortical and atrial triactines much larger (400–700 µm) and diactines and pseudosagittal triactines much thicker (50–90 µm) than Haeckel’s and the present material. If these measurements would prove to be inaccurate or much more variable than so far determined, these names could be synonyms. Redescription is necessary. Burton (1959) reported Grantessa glabra from the South Arabian region and Grantessa sycilloides from the Gulf of Aden, but he did not provide a description of his material. He commented that the two species, glabra and sycilloides, are probably synonymous.

We obtained a 28S partial sequence of one of our specimens (ZMA Por. 13664). This ended up in the same clade but rather far away from the group comprised by Sycettusa hastifera-S. simplex-S. hirsitussima sp.nov. (cf. Fig.3). As mentioned above in the Remarks of S. simplex, a trimmed alignment with a length of 403 showed 20 sites or more difference with S. hastifera, S. hirsutissima and S. simplex .