Rhynchozoon ferocula Hayward, 1988

Dick, Matthew H., Tilbrook, Kevin J. & Mawatari, Shunsuke F., 2006, Diversity and taxonomy of rocky-intertidal Bryozoa on the Island of Hawaii, USA, Journal of Natural History 40 (38 - 40), pp. 2197-2257 : 2242-2243

Rhynchozoon ferocula Hayward, 1988

( Figure 14D–F )

Rhynchozoon ferocula Hayward 1988, p 332 , Plate 13a–c.

Rhynchozoon ferocula: Tilbrook et al. 2001, p 100 , Figure 22A, B; Tilbrook 2006, p 297, Figure 65E, F.

Measurements

ZL, 0.28–0.36 (0.326¡0.032). ZW, 0.18–0.25 (0.220¡0.022). OrL, 0.08–0.10 (0.086¡0.008). OrW, 0.08–0.10 (0.087¡0.007). OvL, 0.12–0.15 (0.135¡0.010). OvW, 0.16–0.20 (0.183¡0.015).

Description

Colony unilaminar, encrusting, sheet-like, becoming a low mound-like disc with frontal budding in older colonies; white in colour; minute, the largest observed 3 mm × 2 mm; rapidly becoming fertile, with ovicellate zooids beginning as soon as second generation after ancestrula; one colony ( Figure 14D ) 1.5 mm in diameter has 27 zooids, eight of which have ovicells. Colony surrounded by calcified lamina one or two zooid lengths deep, representing basal walls of newly forming zooids. Marginal zooids hexagonal or barrel shaped. Frontal wall moderately convex, smooth at first, but later lumpy with uniform low tuberculation or a few small nodules, or rugose; imperforate except for two to four areolae along each lateral margin. Primary orifice ( Figure 14F ) width approximately equal to length (including sinus); beaded with 11–14 denticles; proximal sinus U-shaped, about one-third the width of the orifice, flanked by distinct condylar shelves, each buttressed with a ridge; condyles small, rounded, not reaching sinus. Marginal zooids with two to five (mode5four) short, tapering, tubular oral spines around distal margin. Peristome developed proximally and laterally as a thickened, raised lip, typically with paired, conical or nodular lateral projections and an additional one to three similar projections between them. A suboral avicularium is entirely lacking in our specimens. Some zooids have a small frontal avicularium ( Figure 14E ) along the lateral or proximal margin, the rostrum raised at an angle to the frontal surface, the acute mandible longer than broad and usually pointing toward the zooidal margin. Ovicell ( Figure 14E ) hemispherical, conspicuous; covered with heavy calcification continuous with frontal wall of succeeding zooid, or sometimes with contributions from two zooids delineated by a suture line; smooth in texture or faintly rugose or granulose, often with a small mammiform projection on top and occasionally with small nodules lateral to tabula; labellum complete along proximal margin, delineating a transversely elliptical tabula.

Remarks

There are some difference between the Hawaiian specimens and material previously described from other localities. The sinus is more open, with the sides forming nearly a right angle with the condylar shelves, and zooids bear no more than a single frontal avicularium. We identify our material as R. ferocula on the basis of the small, discoid colony with a broad marginal lamina; the relatively small, few areolar pores; usually four oral spines; the peristome consisting of a thickened lip with processes; the lack of a suboral avicularium; and the small, transversely elliptical tabula of the ovicell. The condylar shelves, although not constricting the opening to the sinus, are buttressed with a sharp ridge like that in material from other localities.

Distribution

Originally described from Mauritius ( Hayward 1988), this species has also been found at Vanuatu ( Tilbrook et al. 2001). This is the first record for the Hawaiian Islands.

Figures

Figure 14. (A–C) Metacleidochasma verrucosa n. sp., holotype (NHM 2006.7.21.21): (A) autozooids; (B) enlargement of orifice; (C) ancestrula. (D–F) Rhynchozoon ferocula Hayward: (D) view of entire colony; this small colony of 27 zooids has produced eight ovicells; (E) ovicellate zooids; (F) enlargement of primary orifice. All specimens bleached. Scale bars: 400 Mm (A, E); 100 Mm (B, C, F); 1 mm (D).