Trematooecia hexagonalis (Canu & Bassler, 1930)

Almeida, Ana C. S., Souza, Facelucia B. C., Menegola, Carla M. S., Sanner, Joann & Vieira, Leandro M., 2014, Taxonomic review of the family Colatooeciidae Winston, 2005 (Bryozoa, Cheilostomata), with description of seven new species, Zootaxa 3868 (1), pp. 1-61 : 44-46

Trematooecia hexagonalis (Canu & Bassler, 1930)

( Fig. 27 , Table 6 )

Holoporella hexagonalis Canu & Bassler, 1930a: 38 , pl. 7, fig. 1. [Galápagos Islands]

Trematooecia hexagonalis: Osburn 1952: 503 (part). [only Galápagos; specimens from Gulf of California and Mexico belong to Cigclisula osburni n. sp.]

Not Trematooecia hexagonalis: Soule 1961: 59 . [California; = Cigclisula osburni n. sp.]

Not Trematooecia hexagonalis: Soule & Soule 1964: 40 . [ Isla Conchas; = Cigclisula osburni n. sp.]

Material examined. Holotype: USNM 8513 , Holoporella hexagonalis, F. Canu & R. Bassler det., Albatross Station D. 2813, Galápagos Islands.

Description. Colony encrusting, uni- to multilaminar. Zooids hexagonal, becoming polygonal with increasing calcification, generally longer than wide, delimited by slightly raised sinuous margins. Frontal shield heavily calcified, uniformly punctured by 36–51 pseudopores, granular. Primary orifice somewhat hoof-shaped, longer than wide, with arcuate anter delimited from broader concave poster by 2 downcurved condyles at about one-third zooid length. Secondary orifice surrounded by 4 solid tubercles. Frontal avicularia small, elliptical, usually 1, rarely 2, per zooid, placed at proximal zooidal margin. Interzooidal avicularia absent. Ooecium subglobose, as long as wide; ectooecium granular with median slit-like membranous area.

Remarks. When Canu & Bassler (1930a) described this species they stated that the specimen lacked ooecia. Examination of the holotype by SEM, however, showed that two zooids have ooecia, each with a proximally facing slit-like ectooecial frontal membranous window (not visible in Figs 27 E–F owing to specimen orientation) that is typical for Trematooecia .

Trematooecia hexagonalis is characterized by a frontal shield with 36–51 more-or-less evenly distributed pseudopores, four solid tubercles around the secondary orifice, no suboral or interzooidal avicularia and a granular ectooecium with a median inverted slit-like membranous window. Trematooecia hexagonalis resembles T. clivulata and Trematooecia ligulata Ayari & Taylor, 2008 in having encrusting colonies, tubercles around the secondary orifice and an ectooecium with a frontal slit, but differs in the uniformly punctured frontal shield, elliptical frontal avicularia and lack of interzooidal avicularia.

Owing to the uniformly punctured frontal shield and the presence of tubercles around the secondary orifice, specimens from Atlantic coast of Panama (= Cigclisula perforata n. sp.; see above) and the Pacific (= Cigclisula osburni n. sp., see above; see also Osburn 1952; Soule 1961; Soule & Soule 1964) are assigned to T. hexagonalis . This species is distinguished by the ectooecium with a median inverted U-shape membranous area, while that in C. perforata n. sp. and C. osburni n. sp. has irregular pseudopores.

Trematooecia hexagonalis is known only from the type locality in the Galápagos Islands . According to Canu and Bassler (1930a), the species encrusts shells .

Distribution. Pacific: Galápagos Islands.

Figures

FIGURE 27. Trematooecia hexagonalis (Canu & Bassler, 1930). A–F, USNM 8513, holotype, Galápagos Islands. A, B, groups of zooids. C, close-up of zooids and opercula. D, primary orifice. E, F, ovicelled zooids and small, elliptical frontal avicularia. Scale bars: A = 500 µm; B = 200 µm; C, E, F = 200 µm; D = 100 µm.