Sycettusa hirsutissima

Van, Rob W. M. & De, Nicole J., 2018, Calcareous sponges of the Western Indian Ocean and Red Sea, Zootaxa 4426 (1), pp. 1-160: 117-119

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Sycettusa hirsutissima


Sycettusa hirsutissima  sp.nov.

Figs 71a–d View Figure , 72a– g View Figure

Material examined. Holotype, RMNHAbout RMNH Por. 10004, Saudi Arabia, Jeddah , near Thuwal, Tahlah, 22.25725°N 38.880917°E, scuba, coll. N.J. de Voogd, field nr. THU14/JED211, 13 November 2014.GoogleMaps 

Paratype, RMNHAbout RMNH Por. 9588, Saudi Arabia, Jeddah , near Thuwal, Abu Gishaa, 22.255194°N 39.025639°E, depth 12 m, scuba, coll. N.J. de Voogd, field nr. THU06/JED083, 9 November 2014.GoogleMaps 

Description. Densely hairy tubes ( Figs 71a–b View Figure ), hanging down, from reef walls. Color yellow or orange below a thick pelt of diactines. In preservation they become dark grey. Size up to 8 cm high, 0.5–1.5 cm in diameter. Consistency firm.

Aquiferous system. Syconoid.

Skeleton. ( Figs 71c–d View Figure ) Inarticulate with cortex of triactines, carried by the unpaired and shorter actines of pseudosagittal triactines. Choanosomal skeleton consists of the longer actines of the subcortical pseudosagittal triactines and the unpaired actines of sagittal subatrial triactines. Atrial skeleton consists of smaller sagittal triactines.

Spicules. ( Figs 72a–g View Figure ) Diactines, trichoxeas, cortical triactines, subcortical pseudoaagittal triactines, subatrial triactines, atrial triactines.

Diactines ( Figs 72a–b View Figure ), consisting of two types, long thin with sharp points ( Fig. 72a View Figure ), often fragmented, 1200– 2213 –3200 x 15 – 21.1 –33 µm, and a shorter type with lance head endings of variable length and thickness ( Figs 72b,b View Figure 1 View Figure ), 336– 1179 –2110 x 12– 20.3 –30 µm.

Trichoxeas ( Fig. 72c View Figure ), invariably broken into smaller pieces, 540– 1413 –2940 x 2– 2.9 –3.5 µm.

Cortical triactines ( Fig. 72d View Figure ), almost regular or slightly sagittal, 171– 202 –261 x 10 – 16.0 –18 µm.

Pseudosagittal triactines ( Figs 72e View Figure ), longest actine 420– 582 –738 x 24 –31.3–43 µm, shorter actine 225– 294 –383 x 23 – 29.4 –40 µm, unpaired actine 162– 207 –299 x 21 – 28.8 –42 µm.

Subatrial triactines ( Figs 72f View Figure ), variably with longer and shorter unpaired actines and flat-angled or acuteangled paired actines, unpaired actines 282– 490 –530 x 282– 36.6 –52.5 µm, paired actines 162– 258 –375 x 14 – 31.6 –46 µm.

Atrial triactines ( Fig. 72g View Figure ), slightly sagittal, 81– 158 –231 x 7 – 13.1 –16 µm.

Distribution and ecology. Saudi Arabian Red Sea, on overhangs in shallow water.

Etymology. Hirsutus (L.) means hairy, rough, referring to the ‘pelt’ of long protruding bundles of diactines. We use the superlative of hirsutus to emphasize the exteme hairiness.

Remarks. The new species is close to S. hastifera  in overall appearance and in spicule complement. However, the two specimens are extremely and densely hairy, unlike the dozen S. hastifera  specimens we had at our disposal, which have the protruding diactines much less dense. In the new species, the body wall underneath the pelt of diactines is barely visible and has a yellow color, while it is always clearly visible and greyish or greenish white in S. hastifera  . In contrast to S. hastifera  the sizes (length and thickness) of the longest actine of the pseudodosagittal triactines of our new species is usually larger than that of the subatrial triactines, although this may not be of great importance. At first, we were inclined to consider the new species an extreme form of S. hastifera  . However, we obtained partial 28S sequences of the two specimens (GenBank acc.nrs MF872774, MF872775, and MF872776) and in the phylogeny of Fig. 3 View Figure they did not group into the same clade with Sycettusa hastifera  (GenBank acc.nrs MF872777 of RMNHAbout RMNH Por. 9659, and MF872778 of ZMAAbout ZMA Por. 13443) and S. simplex ( Jenkin, 1908)  (GenBank acc. nrs MF872779 of RMNHAbout RMNH Por. 10154 and MF872781 of ZMAAbout ZMA Por. 12446), supporting a separation at the species level. To investigate the molecular differences between S. hastifera  , S. hirsutissima  sp.nov. and S. simplex  , we separately aligned and trimmed the available Sycettusa  28S sequences of these three species yielding a length of 403 sites. The sequences of S. hirsitussima  sp.nov. were identical. They shared shared three site differences with S.hastifera  and four with S. simplex  . The latter two species differed only in a single site, despite being clearly distinct in habitus as S. simplex  has an almost smooth surface (cf. below).


National Museum of Natural History, Naturalis


Universiteit van Amsterdam, Zoologisch Museum