Iodictyum magniavicularis Amui & Kaselowsky 2006

Iodictyum magniavicularis Amui & Kaselowsky, 2006 (Fig. 10.1–6) Iodictyum magniavicularis Amui & Kaselowsky, 2006: 18, figs 23, 24. Material examined. SMF 1812 (St. 236 KD; holotype; Fig. 10.6), SMF 1814 (St. 236 KD; paratype; Fig. 10.5), SMF 40786 (2 specimens; St. 283 KU; B = Fig. 10.1–4). Description. Colony erect, reticulate, unilamellar. Branches anastomosing, forming elliptical fenestrulae (Fig. 10.1). Trabeculae consisting of autozooids arranged in two to six alternating series. Zooids opening on one side only, separated by thin furrows. Basal side divided into irregular sectors by reticulate network of calcified ridges (Fig. 10.2). Sectors flat, ornamented with irregularly placed circular tubercles centrally, with irregularly placed circular pores at sector margin. Ancestrula and early astogeny not observed. Autozooids longitudinally rectangular to slightly hexagonal, 324–457 μm (ẋ = 379 ± 33 µm; CV = 9; N = 60 on 4 specimens) long by 153–297 μm (ẋ = 212 ± 32 µm; CV = 15; N = 60 on 4 specimens) wide (Fig. 10.3). Frontal shield slightly depressed centrally, ornamented with 6–10 irregularly placed circular tubercles, pierced by two, rarely one, circular to elliptical areolar pores at the proximolateral margins and by two, rarely three, circular areolar pores at the lateral margins. Primary orifice not readily visible, immersed within columnar peristome; condyles not observed. Peristome salient, cylindrical. Pseudospiramen proximomedially, circular, connected to peristome via slit. Secondary orifice circular, with crenulated distal (and distolateral) margin, 71–121 μm (ẋ = 94 ± 9 µm; CV = 9; N = 60 on 4 specimens) in diameter. Spine bases not observed. Ovicells hyperstomial, globular, 126–183 μm (ẋ = 148 ± 13 µm; CV = 8; N = 17 on 2 specimens) long by 142–184 μm (ẋ = 164 ± 10 µm; CV = 6; N = 17 on 2 specimens) wide; ectooecia smooth, partly covered by frontal wall calcification of adjacent autozooids; aperture forming a semicircular notch proximomedially (Fig. 10.4–5). Avicularia monomorphic, very rare, adventitious, single, oral, lateral to the orifice, laterally directed, bilaterally symmetrical, transversely elliptical, indenting the peristome and overlapping adjacent autozooids, 191–225 μm (ẋ = 208 ± 24 µm; CV = 12; N = 2 on 2 specimens) long by 95–124 μm (ẋ = 110 ± 21 µm; CV = 19; N = 2 on 2 specimens) wide (Fig. 10.6). Avicularian aperture rounded triangular, extending to half the avicularian length. Crossbar complete, arc-shaped, located at about one-fourth the avicularian aperture length. Rostrum truncate, well-rounded, directed laterally. Kenozooids not observed. Remarks. Iodictyum is a diverse genus comprising morphologically variable species, currently known only from the Indian Ocean and the western Pacific Ocean. Iodictyum magniavicularis from the Gulf of Aden was first described by Amui & Kaselowsy (2006) and is reimaged here. Unfortunately, the type colonies of the species are fragmented into several pieces, but their diagnostic features remain recognisable. The large, eponymous avicularia are very rare (Fig. 10.6), with only one or two observed per colony in the examined material. The structure of both the ovicell and the avicularia in Iodictyum magniavicularis closely resembles that of Iodictyum violaceum Hayward, 2004 from New Caledonia. However, Iodictyum violaceum differs in having a frontal shield perforated by large pores and a higher frequency of avicularia.