Buchneria variabilis (Androsova, 1958) Androsova, 1958

Hirose, Masato, 2012, Revision of the genus Buchneria (Bryozoa, Cheilostomata) from Japan, ZooKeys 241, pp. 1-19 : 10-11

Buchneria variabilis (Androsova, 1958) comb. n. Figures 9, 10

Porella variabilis Androsova, 1958, 165, fig. 96; type locality, Moneron Island, northern Sea of Japan.

Material examined.

Androsova’s type specimen (ZIN-1/3670) in Zoological Institute of the Russian Academy of Sciences (ZIN RAS), colony collected southwestern region of Sakhalin, Moneron Island (Kaibato), Sea of Japan, 36 m depth, (examined by micrographs); large erect colonies and fragments (NSMT Te-724 to Te-734; ZIHU 4130 and 4131), collected SE of Akkeshi Bay (42°48.37'N, 144°56.22'E) by M. Hirose from research boat Misago-maru, 6 July 2010, 116 m depth, by dredge; large erect colony and fragments (NSMT Te-790 to Te-794) collected SE of Akkeshi Bay (42°48.20'N, 144°55.43'E to 42°48.26'N, 144°54.91'E) by M. Hirose from research boat Misago-maru, 8 July 2011, 114−116 m depth, by dredge.

Measurements.

ZL, 0.558−0.921 (0.751 ± 0.101); ZW, 0.408−0.882 (0.611 ± 0.088); n=25. OrL, 0.135−0.223 (0.189 ± 0.019); OrW, 0.130−0.226 (0.192 ± 0.023); n=27. OvL, 0.124−0.444 (0.247 ± 0.072); OvW, 0.104−0.395 (0.214 ± 0.056); n=44.

Description.

Colony erect, rigid, robust, with thick, broad, strap-like branches at least 10 zooid widths across, or foliaceous, fan-shaped lobes; lobes or branches 0.86 to 8.04 cm wide (2.15 ± 1.38 cm, n=25), multifurcate or irregularly lobed on distal margin; zooids open on both sides (Fig. 9). Broad lobes of some colonies are covered with conspicuous, closely spaced circular monticules (Fig. 9B). Autozooids oval, rounded hexagonal, or subrectangular in outline; strongly convex frontally, arranged in quincunx, zooecial borders indistinct; frontal shield tessellated, with four to eight areolar pores of irregular size along margin or offset more centrally (Fig. 10A, B). Orifice (Fig. 10C, D) semicircular, broader than long, slightly concave proximally, lyrula and condyles absent (Fig. 10D); deeply immersed with age. Oral spines lacking. Peristome deep, cormidial, formed by contributions of secondary calcification from distal and lateral zooids, with suture lines often evident between the sectors (Fig. 10E). Suboral avicularia approximately same size as orifice, located at margin of peristome; oval, with complete or incomplete pivot, rostrum slightly elevated distally, with a median tooth; mandible semicircular, directed proximally or proximolaterally (Fig. 10B, C). Rounded conical tooth on oral edge of avicularian rostrum conspicuous, projecting into secondary orifice (Fig. 10E). Hypertrophied suboral avicularia are frequent; often larger in area than orifice; distal end of rostrum elevated, pointed; rounded-triangular mandible directed proximally (Fig. 10B, C). I observed no other types of avicularia. Basal part of colony robust, composed of both interzooidal kenozooids and autozooids, borders indistinct. Ooecium imperforate, smooth, completely immersed by secondary calcification from the neighboring zooids, the proximal margin of the ooecium distinctly indented laterally and centrally, obscuring the distal edge of primary orifice in ovicellate zooids (Fig. 10E). Frontal budding frequent (Fig. 10F).

Distribution.

Moneron Island, SW Sakhalin, 36 m depth ( Androsova 1958); off Akkeshi Bay, Hokkaido, 114-116 m depth (this study).

Remarks.

My material matches Androsova’s (1958) description of Porella variabilis . She mentioned that the tooth on the proximal margin of the peristome is associated with the suboral avicularium, and that the tooth is present when the avicularium abuts the proximal margin of the peristome, but absent when the avicularium is offset proximally from the peristome. This is the case in all known species of Buchneria . Androsova (1958) reported Buchneria variabilis from 36 m depth, shallower than my specimen from 114-116 m near Akkeshi. This apparent difference in the bathymetric distribution between Sakhalin and Akkeshi may be related to water temperature, as Sakhalin is more northern and colder than Akkeshi.

Buchneria variabilis differs from Buchneria teres and Buchneria rhomboidalis in colony form and in having larger suboral avicularia.