Conescharellina stellata, Bock & Cook, 2004

Bock, Philip E. & Cook, Patricia L., 2004, A review of Australian Conescharellinidae (Bryozoa: Cheilostomata), Memoirs of Museum Victoria 61 (2), pp. 135-182 : 155

Conescharellina stellata sp. nov.

Figures 9A–I

Holotype. NMV F98993 , stn GAB-019 .

Paratypes. NMV F98994 , stn GAB- 019 (8 colonies).

Other specimens. NMV F98995, stn GAB-128 (1 colony).

Etymology. stellata (L.) – starry, referring to the appearance of the colonies from the adapical side.

Diagnosis. Conescharellina with small, domed colonies. Orifices with rounded sinus and distinct condyles, surrounded by a raised peristome laterally and sometimes antapically. Avicularia lateral, rounded; bar without a ligula, non-palatal area sometimes filled by a lamina. Ovicells fragile, with a depressed, marginally striated entooecium.

Description. Colony small, domed, wider than high; zooid orifices quincuncial. Calcification smooth and slightly tuberculate, adapical region sometimes with small, secondarily thickened mamillae. Peristomes raised laterally, forming a prominent, stellate pattern, especially at the colony margin; sometimes extended adapically and very prominent. Primary orifices rounded with a fairly wide sinus and small to distinct condyles. Adapical pore large, on the edge or outer face of the peristome, surrounded by a rim of calcification, sometimes slightly asymmetrically placed. Avicularia rounded, lateral and paired, widely separated from the peristomes; bar without a ligula, non-palatal side sometimes with a thin lamina, occasionally pierced by a pore. Lunate root pores tending to occur adapically, each with a pair of closely apposed, rounded lateral avicularia. Ovicells present on subperipheral zooids, very fragile, with a raised, smooth, transparent ectooecium and a depressed entooecium, striated marginally, forming pores at the ectooecial junction. Antapical surface with a small central cancellate area.

Colony diameter 1–1.5 mm, height 1 mm, number of alternating whorls 6, number of zooids per whorl 6–8.

Remarks. The colonies have a very regular, stellate appearance from the adapical side. The peristomes are usually well developed laterally but, in one colony (from stn GAB-128), they are also extensive antapically, forming a funnel. The ovicells are extremely fragile and were detached soon after initial scanning electron microscopy. The lower face of the ectooecium shows that it was almost certainly covered by cuticle and apposed but not attached to the surface of the zooid adapically ( Figs 9H, I ). Although closely similar to the smaller colonies of C. obscura in several features, C. stellata differs in the form and distribution of the avicularia, that do not include a solitary one on the antapical side of the peristome. The avicularia also differ in the lack of ligulae and the presence of a lamina filling the non-palatal area. This is not always developed in the specimens from stn GAB-019 but is constantly present in the distinctly larger, more prominent avicularia of the colony from stn GAB-128. The lamina may be pierced by a pore in both populations. C. stellata has been found from the western end of the Great Australian Bight at a depth of 59 m and from the central region at a depth of 304 m. Although these two populations show differences in detail, the number of colonies does not allow any estimate of its significance.

Figures

Figure 9. Conescharellina stellata sp. nov. A–C NMV F98993, holotype. A, adapical view of colony showing prominent bilabiate marginal peristomes and lunate root pores, scale = 500 µm. B, detail of marginal zooid orifice with adapical pore. Avicularium with porous non-palatal lamina (arrow), compare Figure 9E, scale = 200 µm. C, lateral view of colony showing lunate root pore, avicularia, scale = 200 µm. D–E, NMV F98995. D, adapical view of colony with prominent, rounded, funnel-shaped marginal peristomes, scale = 500 µm. E, marginal view showing extended peristomes, orifices and avicularia with non-palatal laminae, one with pore (arrow), compare Figure 9B, scale = 200 µm. F–I, NMV P98994. F, Colony with cuticle in situ and two ovicells near margin, scale = 100 µm, G, detail of ovicells, scale = 100µm. H, I, frontal and basal surfaces of detached ovicell. H, showing ridges in margin of entooecium, forming pores at junction with ectooecium, with basal smooth ectooecium. I, with fracture at original margin of adapical pore, scales = 50 µm.