Scrupocellaria hamata, Tilbrook, Kevin J. & Vieira, Leandro M., 2012

Tilbrook, Kevin J. & Vieira, Leandro M., 2012, Scrupocellaria (Bryozoa: Cheilostomata) from the Queensland coast, with the description of three new species, Zootaxa 3528, pp. 29-48 : 42

Scrupocellaria hamata n. sp.

( Figure 9 )

Material examined. Holotype (here selected): MTQ G25166, HI10–055, Channel between Heron Island and Wistari Reef, Great Barrier Reef, 23.44982° S, 151.91255° E, 26 November 2010, 19 m, coll. KJT. Other material examined: MTQ G26000, HI10–060, Harry's Bommie, 23.46049° S, 151.92929° E, 27 November 2010, 16 m, coll. KJT.

Description. Autozooids at very slight angle to each other, partially back to back, alternating and giving the branch profile a jagged appearance, in short internodes of 5–7 autozooids; autozooids gracile, 0.407–0.473 mm (0.439±0.022) long, 0.0.117– 0.147 mm (0.130± 0.010) wide, with smooth, extensive proximal gymnocyst, approximately equal to or 1.5 times area of oval opesia, cryptocyst very narrow and smooth. Scutum originating from proximal third of lateral margin of opesia (along branch midline), most often oval in shape, covering approximately one quarter the area of the opesia, lobes roughly symmetrical, or slightly larger proximally. Two inner (medial) orificial spines, 3–4 outer orificial spines, long, the most proximal of the inner spines and the second most proximal of the outer spines longest (> 0.5 mm), directed disto-frontolaterally, the most proximal outer spine shorter and directed frontally, a sixth or seventh distomedial spine in axial autozooids. Avicularia of two types: lateral avicularium very small, on distolateral corner of all autozooids, distolaterally directed, with triangular rostrum, mandible curved basally with an acuminate, hooked tip; frontal avicularium rarely seen, on inner side of zooids, near scutum of adjacent zooid, directed medially, with small triangular rostrum and mandible. Ovicells not observed in present material. Single axial vibraculum; other vibracula projecting distal to opesia, 0.101–0.119 mm (0.113±0.006) long, visible frontally, teardrop-shaped, setal groove directed proximomedially, setae long, curving across more than twice width of branch. A rhizoid foramen is present in proximal wall of all lateral vibracula, but not on axial vibraculum; rhizoids barbed at the distal end, usually only present at base of branch.

Etymology. Latin, hamus, hook, barb. Named for the harpoon-like basal rhizoids.

Remarks. Scrupocellaria hamata n. sp. is characterised by its alternating autozooids, extensive gymnocyst, oval scutum, small frontal avicularia and its long non-bifurcating spines. The species most resembles S. sinuosa in its overall appearance, both having a similar alternating pattern of autozooids with the scutum originating from the proximal third of the lateral margin of the opesia. However, S. hamata n. sp. differs in several ways—larger autozooidal size, smaller size and shape of the vibracular chambers, and the small size of the lateral avicularia. Canu & Bassler (1927) characterised S. sinuosa as having one inner and three outer spines, although axial autozooids bear six. However, the zooids in the holotype of S. sinuosa (NMNH 8426) have 1–2 inner and 3–4 outer spines as in S. hamata n. sp. Scrupocellaria sinuosa is further distinguished from S. hamata n. sp. by its smooth rhizoids and its thicker, stouter scuta.

Distribution. Scrupocellaria hamata n. sp. is represented by two colonies, both found in the channel between Heron Island lagoon and Wistari Reef.

Figures

FIGURE 9. Scrupocellaria hamata n. sp. A – F, MTQ G 25166. A, frontal surface of branch at bifurcation. B, frontal surface of two autozooids; note the position of the vibracular chamber protruding distal to the rim of the zooid at right. C, close-up of branch bifurcation seen in A. Note the barbed rhizoids. D, basal surface with details of vibracular chambers. E, lateral view of branch showing the length of the spines. F, basal surface at branch bifurcation showing the single axial vibracular chamber. Scale bars: 500 µm (A, F); 100 µm (B – E).