Microporella mandibulata, Branch & Hayward, 2005

Branch, M. L. & Hayward, P. J., 2005, New species of cheilostomatous Bryozoa from subantarctic Marion and Prince Edward Islands, Journal of Natural History 39 (29), pp. 2671-2704 : 2695

Microporella mandibulata sp. nov.

( Figure 11 D–G)

Material

Holotype: St. 55 Marion Island (46 ° 55 9 S, 37 ° 35 9 E), 42–47 m, SAM A 27554.

Description

Colony a flat unilaminar sheet, encrusting rock. Autozooids oval to hexagonal, convex, separated by distinct grooves; 0.7–0.8X 0.4–0.6 mm; frontal shield with distinctive surface of smooth nodules, and sparse small pores. Primary orifice slightly wider than long, ca 0.10X 0.09 mm; the rim with fine denticulation revealed by SEM, proximal border straight, the proximo-lateral corners slightly convex; a raised peristomial rim surrounds the entire orifice. Six short, cylindrical spines spaced around lateral and distal borders of orifice. Ascopore prominent, separated from proximal border of orifice by a distance equivalent to ca two-thirds orifice length; crescentic, its rim with fine denticulations that do not fuse. The ascopore is enclosed within a cupped depression, raised proximally as a projecting umbo. A single large adventitious avicularium on each autozooid, adjacent or slightly proximal to ascopore, disto-laterally orientated; rostrum acute to frontal plane, short, bluntly triangular and supporting a slender, setiform mandible, 0.2 mm long. Ovicells not present in sample. Large basal pore chambers present. The specimen was smothered with diatoms.

Etymology

Latin, mandibula, mandible, with reference to the avicularian mandible.

Remarks

Species of Microporella have been described from shelf and coastal waters worldwide, and many are confusingly similar. Pending a review of this apparently homogenous, and species-rich genus ( Taylor and Mawatari 2003), taxa are best characterized by the shape and dimensions of the primary orifice, the number of spines, the morphology of the ascopore and its position relative to the primary orifice, and the morphology and position of the avicularium. In all of these characters M. mandibulata is distinct from those southern hemisphere species presently adequately described, and illustrated by SEM (e.g. Gordon 1984, 1989), but distinctions between it and other described species will be best made following systematic revision of the genus on a worldwide basis.

Figures

Figure 11. (A–C) Fenestrulina pumicosa sp. nov., SAM A27362: (A) ovicelled autozooid, X70; (B) autozooids, X45; (C) primary orifice and ascopore, X110. (D–G) Microporella mandibulata sp. nov., SAM A27554: (D) autozooid, X100; (E) ascopore, X180; (F) avicularium, X180; (G) avicularium with long mandible, X150.