Idmidronea erecta, Liu & Liu & Zágoršek, 2019

Liu, H., Liu, X. & Zágoršek, K., 2019, Cyclostome bryozoans from Qingdao, South Yellow Sea, China, Zootaxa 4603 (3), pp. 473-500 : 482-483

Idmidronea erecta n. sp.

( Figs 22–25 )

lsid:zoobank.org:act: 190A0C00-38AB-43B1-B1D8-6060329257E3

Diagnosis. Idmidronea with gonozooid frontally situated between the fascicles, and straight ooeciostome arranged between regular autozooidal apertures.

Holotype. Specimen MBM 284448 from Lingshan Island ( Figs 22, 23 ).

Paratype. Specimen MBM 284471 ( Jiaozhou Bay)

Additional material. Two colonies without gonozooecium from samples MBM 0 92370 (Lingshan Island) and MBM 0 92378 ( Jiaozhou Bay).

Etymology. Referring to the straight direction of the ooeciostome, not curved as commonly in other Idmidronea species.

Description. Colony erect, robust, and dichotomously branched. Branches short and wide (length about 1000–1300 µm, width at the proximal end of the branch about 670–820 µm), with ca. 5–8 zooidal fascicles between successive bifurcations. Fascicles alternating, consist of 3–6 autozooidal apertures. Autozooidal tubes wide (ca. 138–153 µm); length of the frontal wall 380–456 µm, diameter of apertures ca. 100 µm. Gonozooid frontal, elongate (length about 1300 µm), spreading over three or four fascicles, frontal wall porous. Ooeciopore oval, slightly smaller than the autozooidal aperture (diameter approximately 70–80 µm), situated close to the bifurcation, proximally oriented, usually close to a regular autozooid. Dorsal side of the branch porous, almost flat and slightly convex. Kenozooids approximately 40 µm in diameter, developed on the proximal portion of the branch, spreading over the colony in the distal direction.

Remarks. Idmidronea atlantica as described by Hayward & Ryland (1985) is similar to the new species in the position of the gonozooid, but differs in having much longer branches and the swan-neck-shaped ooeciostome. Idmidronea biporata Brood, 1976 also has a straight ooeciostome but differs in having very delicate colonies, much narrower branches, and fascicles consisting of only two autozooidal apertures. Many recent Idmidronea species have a similar arrangement of autozooidal tubes, and similar-sized branches and pseudopores, but lack a gonozooid to compare with the new species. For example, Idmonea contorta Busk, 1875 (p. 12, pl. 8) from South Africa shows similar arrangement of autozooidal tubes as does Idmonea australis MacGillivray, 1885b (p. 470, pl. 68, fig. 2).

In addition to the presence of kenozooids, which may be a variable character that may (or may not) develop in basal branches during late astogeny, this species differs from Exidmonea intercalata n. sp. in having straight oriented ooeciostome, situated more or less in the central part of the gonozooid. Exidmonea intercalata n. sp. has downwardly curved, swan-neck shaped ooeciostome, situated in the margin of the gonozooid.

Occurrence. Lingshan Island and Jiaozhou Bay.

Figures

FIGURES 22–25. Idmidronea erecta n. sp. Lingshan Island. 22–24. Holotype MBM 284448. 22. General view showing the position of the gonozooid. 23. Detail of the ooeciopore with a straight peristome arranged between regular autozooidal apertures. 24. Dorsal side of the colony showing kenozooids on the distal margin and minute pseudopores. 25. Paratype MBM 284471, detail of the gonozooid situated frontally between the fascicles. Scale bars: 22, 24 = 1 mm; 23, 25 = 100 µm.