Reteporella gigantea ( Busk, 1884 )

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 : 2700-2702

Reteporella gigantea ( Busk, 1884)

( Figure 13 A–G) Retepora gigantea Busk 1884, p 114 , Plate 26, Figure 7 .

Material

St. 37 Marion Island (46 ° 41 9 S, 38 ° 01 9 E), 360–376 m, SAM A27526 ; St. 45 Marion Island (47 ° 00 9 S, 37 ° 55 9 E), 420–540 m, SAM A27493 .

Description

Colony forms large, erect, reticulate lacy fans, to 30 mm high, with horizontal spread of at least 30 mm. Branches (trabeculae) 0.8–1.2 mm in diameter, fusing at regular intervals, leaving diamond-shaped to oval spaces (fenestrulae) between them, usually 3–4.5 mm long and 0.9–1.7 mm wide. Autozooids in two to three alternating, longitudinal series (four prior to trabecular division), opening on one surface, elongate, separated by clear, raised sutures, 0.5–0.9X 0.35–0.5 mm. Primary orifice circular, obscured in early ontogeny by a low, thick-rimmed peristome, enclosing a small medio-proximal avicularium with a finely denticulate, semicircular rostrum, adjacent to a small, round pseudospiramen. No oral spines apparent. Frontal shield granular, with a few (less than six) large pores scattered on the surface. One or two small, frontal adventitious avicularia present on each autozooid, with semicircular rostrum. Irregularly shaped kenozooids sporadically present between the autozooids, particularly adjacent to trabecular fusion/anastomosis; each bearing one or two adventitious avicularia. Ovicell hyperstomial, partly obscured by a granular ooecial cover; with a narrow, straight frontal fissure.

Remarks

Reteporella gigantea was described by Busk (1884) from Possession Island (46 ° 47 9 S, 51 ° 37 9 E) and has not been reported again since. It is particularly characterized by its large, broadly open, fan-like colony form, by the small pseudospiramen set close to the proximal rim of the peristome, and by its small adventitious avicularia, occurring singly within the peristome, and elsewhere on the frontal shield. Busk (1884) noted a second type of avicularium, with a slender, acuminate mandible, sparsely present in his material, but none were noted in the Marion Island specimens.

Figures

Figure 7. (A) Taliυittaticella frigida, SAM A27058, autozooid, X110. (B–E) Catenicella glabrosa sp. nov., SAM A27556: (B) autozooid and ovicelled autozooid, X80; (C) autozooid, X100; (D) portion of colony showing internodes, X40; (E) detail of avicularium, X300.

Figure 13. Reteporella gigantea, SAM A27526: (A) part of fan-shaped colony showing regular fenestrulae, X6; (B) autozooids and small adventitious avicularia, X30; (C) ovicelled autozooid, X75; (D) kenozooid with adventitious avicularia, X75; (E) autozooids, X75; (F) adventitious avicularium, X300; (G) aperture with avicularium in the lower lip, X150.