Celleporaria firmispinosa ( Silén, 1954 )

Martino, Emanuela Di, 2023, Scanning electron microscopy study of Lars Silén’s cheilostome bryozoan type specimens in the historical collections of natural history museums in Sweden, Zootaxa 5379 (1), pp. 1-106 : 65-67

Celleporaria firmispinosa ( Silén, 1954)

( Fig. 35 ; Table 32)

Holoporella firmispinosa Silén, 1954: 38 , figs 18, 19.

Material examined. Holotype by original designation LUZM 56.2 ( Fig. 35A–E ), south-western region of Western Australia, 7 miles NE of Cape Naturaliste. Leg. Prof. T. Gislén , Australia Expedition 1951–1952, collected 4.1.1952 . Additional material: LUZM 56.1 ( Fig. 35F–I ), Warnbro beach, Perth , Western Australia; depth 18 m. Leg. Prof. T. Gislén, Australia Expedition 1951–1952, collected 30.11.1951. Both specimens encrusting algae .

Description. Colony encrusting, mounded multilayered ( Fig. 35A, F, G ).

Autozooids distinct, with deep interzooidal furrows, erect and chaotically arranged in the central area of the colony, rectangular along the growing edge, longer than wide (mean L/ W 1.38); frontal shield convex, coarsely granular (granules about 20 µm in diameter), imperforate except for a few, circular marginal areolar pores scattered along the zooidal outline, 10–25 µm in diameter ( Fig. 35A ).

Orifice transversely D-shaped with straight proximal margin lacking any structures, surrounded by a band of smooth calcification, more extensive proximally (about 30 µm wide), sloping steeply laterally placing the opening at a lower level than the frontal ( Fig. 35B, D ); two robust distolateral spines 30–60 µm in diameter, 120–250 µm long ( Fig. 35A, B ).

Adventitious avicularium suboral, placed parallel to the proximal margin of the orifice, medially or on one side, oval with raised rostrum directed laterally and outwards at about 45° in respect to the frontal plane ( Fig. 35B–D ); mandible semielliptical ( Fig. 35B, C ); some zooids developing a robust, ridged, conical suboral mucro bearing the avicularium, 110–150 µm long ( Fig. 35G, I ). Interzooidal avicularia absent.

Ovicells hood-shaped, not closed by the operculum ( Fig. 35E, H ); ooecium granular as the frontal shield, imperforate, sometimes with a blunt umbo centrally; no spines visible in ovicellate zooids.

Remarks. As seen in Amphiblestrum crassispinosum , another species growing on algae, this species also shows long oral spines, a stout suboral mucro and sometimes an umbo on the ooecium, which can be interpreted as an adaptation to the flexible substrate (i.e. algae) they encrust (see also Di Martino & Rosso 2021).

More than 30 species of Celleporaria are known from Australian waters ( Cook et al. 2018). Celleporaria bispinata ( Busk, 1854) , recorded from south-western Australia and Tasmania, is the most similar to C. firmispinosa . Both species lack interzooidal avicularia and have a simple orifice devoid of any structures on the proximal margin, two robust and long distolateral spines, and a suboral avicularium that in some zooids is lodged on a well developed mucro (see Cook et al. 2018, fig. 3.130A for C. bispinata ). Also, Celleporaria bispinata has two large, rounded oral condyles and avicularium with denticulate rostrum, features not observed in C. firmispinosa .

Figures

FIGURE 35. Celleporaria firmispinosa Silén, 1954. A–E. Holotype LUZM 56.2, off Rockingham, Western Australia. F–I. Specimen LUZM 56.1, Warnbro beach, Western Australia. A. Group of zooids. B. Close-up of an orifice with elliptical suboral avicularium and two stout spines. C. Close-up of suboral avicularium with open mandible. D. Close-up of an orifice, showing the proximal margin, and a broken suboral avicularium. E. Ovicellate zooids. F, G. General view of two areas of the mounded colony showing zooids with long spines and mucro and the algal substrate. H. Close-up of ovicellate zooids. I. Lateral view of zooids with well-developed suboral mucro. Scale bars: A = 500 µm; B, D = 100 µm; C = 50 µm; E = 250 µm; F, G = 1 mm; H = 300 µm; I = 200 µm.