Scrupocellaria diadema Busk, 1852a

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 : 31-34

Scrupocellaria diadema Busk, 1852a

( Figures 1 , 2 )

Scrupocellaria diadema Busk, 1852a: 370 ; Busk, 1852b: 24, pl. 28, figs 1–3; Harmer, 1926 (part): 375.

Material examined. Holotype: NHMUK 1854.11.15.80, Moreton Bay, Queensland, 27.25° S, 153.25° E. Other material examined: MTQ G25296, Gulf of Carpentaria, 15.9988° S, 139.65332° E, 4 March 2005; MTQ G25337, Site 2319, Sample Id. 0 21793, SBD 0 29103, Great Barrier Reef, 24.465° S, 150.905° E, 18 September 2004, 70 m; MTQ G25343, off Townsville, Stn 1460, Square 5B, 18.8833° S, 146.9667° E, 3 August 1986.

Description. Autozooids at slight angle to each other, partially back to back; gracile, 0.340–400 mm (0.365±0.0.16) long and 0.195–0.240 mm (0.208±0.012) wide, with smooth, proximal gymnocyst, approximately one quarter to one third area of large oval opesia, cryptocyst very narrow and smooth. Scutum originating from midway along inner (branch midline) lateral margin of opesia, very gracile, most often club-shaped, but may be small and rounded with proximal and distal lobes of equal size, or slightly bifurcated. Two inner spines, and two outer orificial spines, short, the two most proximal spines distorting the gymnocystal/cryptocystal rim, directed frontally and bifurcating, a fifth distomedial spine in non-brooding autozooids. Avicularia of two types: lateral avicularia, small, 0.057–0.090 mm (0.069±0.010) long, on distolateral corner of all autozooids (except axial autozooid at branch bifurcation), distolaterally directed, with straight-edged triangular rostrum the tip of which is raised slightly, mandible curved basally with a sharp, hooked tip; frontal avicularia often seen, originating proximal to cryptocystal rim on inner side of zooid, directed distomedially, either small and similar in shape to lateral avicularia, or large, of varying size, aquiline, raised on a tubular base, rostrum serrated laterally, with a hooked tip, mandible elongate-triangular, curved basally with a sharp, hooked tip. Ovicells smooth, 0.149–0.188 mm (0.177±0.013) long and 0.181–0.214 mm (0.199±0.010) wide, with 2–5 circular or elongate oval pores, often with a slightl raised rim. Single axial vibraculum; other vibracula projecting laterally, 0.165–0.201 mm (0.189±0.013) long, visible frontally, drop-shaped, setal groove directed proximomedially, seta long, curving across more than width of branch. A rhizoid foramen is present in proximal wall of all lateral vibracula, but not on axial vibraculum; however, rhizoids usually only present at base of branch. Rhizoids with some retroussé hooks.

Remarks. Scrupocellaria diadema is characterised by its gracile, club-shaped scutum, its small, lateral avicularia and the often-seen aquiline, frontal avicularia with a tubular base.

Although Scrupocellaria diadema was originally described from Queensland, several of the specimens cited by Harmer (1926) from this region, as well as the Indonesian and Malaysian regions, do not belong to S. diadema ( Tilbrook 2006) . Harmer (1926) reported S. diadema as the commonest species of Scrupocellaria found amongst the Siboga specimens, characterised by its robust habit, the presence of short ovicells with tubular pores, variably shaped scuta, and gigantic frontal avicularia on the axillary zooids. At least three species were synonymised within the material he cited: S. cervicornis Busk, 1852 and S. annectens MacGillivray, 1887 from Australia, and S.

gaspari Thornely, 1907 from the Gaspar Straits, Malaysia (see Figure 3 ). In the figures of S. diadema and S. cervicornis given by Busk (1852b) it is possible to distinguish S. diadema and S. cervicornis using the shape of the frontal scuta and frontal avicularia. These characters are easily seen in the type specimens ( S. diadema , NHMUK 1854.11.15.80, Figure 1 ; S. cervicornis , NHMUK 1854.11.15.81). However, Harmer (1926) considered the shape of the frontal scutum and frontal avicularium to be variable within a colony, describing a huge plasticity in their morphology. Comparison of Harmer’s (1926) cited S. diadema specimens from different localities reveals some undescribed species (see Figure 3 ). Recent molecular evidence ( Lee et al. 2011) reiterates that a species complex exists within material attributed to S. diadema ; therefore, S. diadema sensu stricto is not as common or as widely distributed as once thought. In addition, comparisons between the holotype of S. diadema (see Figure 1 ) and the specimens figured by Tilbrook (2006) show the Solomon Islands specimens to be distinct, i.e. characterised by the presence of slenderer branches, smaller lateral avicularia, and frontal avicularia with shorter bases than in S. diadema .

Distribution. Scrupocellaria diadema has been recorded on numerous occasions throughout the Indo-West Pacific; however, as discussed above, some specimens belong to other species. Thus, the known distribution of S. diadema sensu stricto is limited to the Queensland coast, i.e. either side of the Cape York Peninsula – in the Gulf of Carpentaria and on the Great Barrier Reef.

Figures

FIGURE 1. Scrupocellaria diadema Busk, 1852 a. A – E, NHMUK 1854.11. 15.80, Holotype. A, frontal surface of branch at bifurcation; note the large frontal avicularium on the axial zooid. B, frontal surface of two branches at bifurcation; note the brooding autozooids and the bifurcating scutum on the brooding zooid (centre). C, frontal surface of branch bifurcation; note the broken large frontal avicularium shown in profile (centre) and the single vibraculum. D, frontal surface of several zooids; note the variation in size of the frontal avicularia and the ovicell pores. E, close-up of partially cleaned frontal surface. Scale bars: 250 µm (A, C, D), 500 µm (B), 200 µm (E).

FIGURE 2. Scrupocellaria diadema Busk, 1852 a. A, MTQ G 25337; B, D, E, MTQ G 25343; C, MTQ G 25296. A, frontal surface of branches and a bifurcation; note the large frontal avicularia and ovicellate zooids. B, basal surface at branch bifurcation showing the single axial vibracular chamber. C, frontal surface of a branch bifurcation; note the brooding zooids and the large frontal avicularium of the axial autozooid, with a single unattached scutum (centre left). D, note the avicularia raised on tubular bases on the first autozooids distal to the bifurcation (centre). E, profile of branch; note the bifurcating spine on the brooding zooid (top left). Scale bars: 100 µm (A – E).

FIGURE 3. Specimens reported as Scrupocellaria diadema by Harmer (1926). A, Scrupocellaria gaspari Thornely, 1907, NHMUK 1936.12. 3.146, syntype. B, Scrupocellaria sp. 1, NHMUK 1928.3. 6.178, Sulu Archipelago. C, Scrupocellaria sp. 2, NHMUK 1928.9. 13.102, Japan. D, Scrupocellaria sp. 3, NHMUK 1928.3. 6.180, New Guinea. Scale bars: 200 µm (A – D).