Calyptotheca trimandibulata, Cumming & Sebastian, 2018

Cumming, Robyn L. & Sebastian, Pascal, 2018, New encrusting species of Lanceoporidae (Bryozoa, Cheilostomata) from the southern Great Barrier Reef, Australia, Zootaxa 4500 (1), pp. 104-114 : 105-108

Calyptotheca trimandibulata n. sp.

( Fig. 1 , Table 1)

Material examined. Holotype: MTQ G101182, inter-reefal, central Swains Complex , southern GBR, 21.313681° S, 151.962273° E, 19 November 2005, 66 m, coll. Seabed Biodiversity Project.

Paratypes: MTQ G101183, same data as holotype; MTQ G101184, seabed east of Heron Island , Capricorn Bunker Group, southern GBR, 23.384826° S, 152.102378° E, 4 November 2005, 56 m, coll. Seabed Biodiversity Project.

Etymology. The epithet combines the Latin words tri- (three) and mandibula (jaw), in reference to the three adventitious avicularia typically present on the frontal shield of each zooid.

Description. Colony encrusting, unilaminar. Autozooids rectangular to irregularly polygonal (c. 0.5 x 0.4 mm; Table 1); frontal shield flattened to slightly convex, pseudopores round, irregularly spaced and very numerous (average 85 per zooid), extending to zooid borders, diameter c. 0.016 mm, distance between pseudopores often less than one pseudopore diameter; interzooidal boundaries marked by thin suture lines and areolae of variable size and shape.

SD, standard deviation

Primary orifice as long as wide (c. 0.11 x 0.11 mm), pyriform (pear-shaped), with a low, thickened, nodular rim of calcification proximally, anter wide, poster with deep, rounded V-shaped sinus; condyles rounded, serrate.

Adventitious avicularia usually three per zooid, two lateral oral, one each side of orifice, directed toward each distal corner, and one proximal, usually medial, directed toward the orifice of the proximal zooid, sometimes a fourth proximally, sometimes on ovicells; semi-elliptical proximally, rostrum acutely triangular and basally curved, proximal opesia oval to semicircular, rostral foramen rounded triangular, crossbar central, complete. Vicarious avicularia absent.

Ovicell immersed (i.e. not noticeably raised above surrounding zooids); ooecium slightly wider than long (c. 0.36 x 0.39 mm) with pseudopores of similar size and density to those of frontal shield, secondary calcification cormidial, as indicated by Y-shaped suture lines; pronounced orifice dimorphism, ovicellate orifice wider than autozooid orifice (c. 0.17 vs 0.11 mm), with a shallower sinus; condyles serrate.

Occasional dimorphic zooids ( Fig. 1A , centre; Fig. 1E , centre) with larger orifice, wider than long (c. 0.19 x 0.15 mm), and a shallow sinus ( Fig. 1G ), similar in size to those of ovicellate zooids; condyles serrate.

Remarks. Calyptotheca trimandibulata n. sp. is distinguished by having three adventitious avicularia per zooid on almost all zooids, all directed outwards, i.e. the two lateral oral avicularia are directed disto-laterally and the proximal avicularium is directed proximally (or sometimes proximo-laterally). No other known Calyptotheca species typically has three avicularia on the frontal shield (not including species with strings of marginal avicularia such as Calyptotheca wasinensis ). Specimens of Schizomavella asymetrica ( Calvet, 1927) from Chios, Aegean Sea, sometimes develop lateral suboral avicularia in addition to the typical suboral avicularium, resulting in three small, oval avicularia on the frontal shield ( Hayward & McKinney 2002). This was first recorded by Hayward (1974, p. 381, fig. 5B) in his description of Calyptotheca triarmata , now considered a junior synonym of S. asymetrica ( Hayward & McKinney, 2002) .

Calyptotheca triangulata and Calyptotheca triquetra share acutely triangular and basally curved rostra with Calyptotheca trimandibulata n. sp., but the avicularia of C. triangulata are more strongly triangular and are directed in the opposite direction to those of C. trimandibulata n. sp. (i.e. medially). C. triquetra has only a single, medial, proximally-directed avicularium.

The occasional dimorphic zooids have orifices that resemble those of maternal zooids in shape (wider than long, shallow sinus) and condyles (similar shape and size, serrate), but appear to be slightly larger (width 0.19 vs. 0.17; length 0.15 vs. 0.11 mm), however sample size is very small ( Table 1).

Distribution: Calyptotheca trimandibulata n. sp. is currently known only from two inter-reefal sites of the southern GBR, one in the central Swains Complex, 66 m, and one east of Heron Island, Capricorn Bunker Group, 56 m.

Figures

FIGURE 1. Calyptotheca trimandibulata n. sp. Holotype (MTQ G101182). A. Autozooids, ovicellate zooids and dimorphic zooid (centre). B. Distal avicularium. C. Proximal avicularium. D. Primary orifice. E. Autozooids, ovicellate zooids and dimorphic zooid (centre). F. Ovicellate orifice. G. Orifice of dimorphic zooid shown in E.