Calcareous sponges of the Western Indian Ocean and Red Sea Author Van, Rob W. M. Author De, Nicole J. text Zootaxa 2018 2018-06-01 4426 1 1 160 journal article 29979 10.11646/zootaxa.4426.1.1 cdd567ed-ebd8-4801-a6a4-af6c9fb964fd 1175-5326 1271239 18929E20-5296-4458-8A8A-4F5316A290FD Trichogypsia spec. Figs 91a–e Material examined. Microscopic slide ZMA.POR. P1616, Seychelles , NE of Aride Island , 4.2°S 55.6833°E , depth 40 m , coll. R.W.M. van Soest , field nr. NIOP-E stat. 715, 19 December 1992 . Unfortunately, the specimen, from which the slide was made, has not been found again in the collections. The data provided here are meant to draw attention to the existence in the Western Indian Ocean of a species of this rare and peculiar genus. Description. A thin red encrustation, lateral size 6 x 5 mm, thickness 2 mm . Surface microconulose. Aquiferous system . Leuconoid. Skeleton (Figs 100a–e) In cross section (Fig. 100a) there is a cortical region consisting of a palisade of smaller diactines, forming small bouquets of 6–10 spicules (Figs 100b–c), with sharp points directed outward. The cortical palisade is carried by tangential larger diactines. The choanosome has large hollows (Fig. 100a), interpreted as wide canals, but not provided with special atrial skeleton. The main skeleton consists of vague tracts of larger diactines (Fig. 100d–e). Spicules. Asymmetrical diactines, in two distinct forms. The cortical palisade has smaller diactines (Fig. 100d), often wobbly or crooked, with the outward-directed end sharply pointed, and the inward-directed end bluntly rounded with spines and small warts, 121– 147 –192 x 8 – 10.9 –14 µm. The main skeleton consists of larger diactines (Fig. 100e), lightly spined along the entire shaft, more heavily spined at the bluntly rounded ends, 315– 426 –530 x 11 – 15.4 –18 µm. Distribution and ecology. Seychelles , at 40 m depth. Remarks. The genus Trichogypsia is so far confined to the North Atlantic and North Pacific. Following Dendy & Row (1913) , the World Porifera Database (Van Soest et al. 2018 ) recognizes three distinct species. In the North Atlantic there are Southern England’s T. villosa Carter, 1871 and Southern Norwegian T. incrustans ( Haeckel, 1872 ) , originally as Leucyssa . This contrasts with Burton’s (1963) opinion that the two are conspecific. Borojević et al. (2000) have re-examined only Carter’s (1871) slide, remarking that the internal canals are lined by special curved spicules, not noted by Carter. In the absence of a redescription of Haeckel’s material, we remain in doubt over the specific differences. Recently, Lehnert & Stone (2017) described a further species Trichogypsia alaskensis from the S coast of Alaska. In any case, T. villosa and T. incrustans (greyish white or greenish white) and T. alaskensis (golden brown) differ from the Seychelles specimen (red) in life color. Spicule lengths of the present specimen are 120–530 µm, Carter and Haeckel give 200–450 µm for the two European species, so these match closely. T. alaskensis has much larger spicules, up to 1225 x 46 µm.