Buchneria rhomboidalis (Ortmann, 1890) Ortmann, 1890

Hirose, Masato, 2012, Revision of the genus Buchneria (Bryozoa, Cheilostomata) from Japan, ZooKeys 241, pp. 1-19 : 9-10

Buchneria rhomboidalis (Ortmann, 1890) comb. n. Figures 7, 8

Escharoides rhomboidalis Ortmann, 1890, 44, pl. 3, fig. 22; type locality, eastern Sagami Bay.

Material examined.

Lectotype. MZS 37-2 (NSMT Te-737), branched colony, collected by L. Döderlein, 1882, Sagami Bay. Paralectotype. MZS 37-1, branched colony, collected by L. Döderlein, 1882, Sagami Bay, 370 m depth. Other material examined. NSMT-Bry R256, Emperor Showa Collection, collected 8 February 1967, 5 km SW of Jogashima, Sagami Bay, 250-400 m depth; NSMT-Bry R267, Emperor Showa Collection, collected 18 March 1968, 4 km WSW of Jogashima, Sagami Bay, 200−220 m depth; NSMT TeS-1, coll. 14 May 2004, west of Ōshima, Sagami Sea (34°40.95'N, 139°17.92'E to 34°40.68'N, 139°18.22'E), 220−277 m depth, beam trawl, RV Tansei-maru; colony (NSMT Te-799), collected by H. Kohtsuka from research boat Rinkai-maru, 10 January 2012, SW of Jogashima, Sagami Bay (35°06.101'N, 139°34.284'E to 35°05.684'N, 139°34.061'E), 218-318 m depth; fragments of colonies (NSMT Te-796, Te-797), collected by M. Hirose from research boat Rinkai-maru, 24 February 2012, WSW of Jogashima, Sagami Bay (35°07.301'N, 139°33.365'E to 35°07.327'N, 139°32.978'E), 300-493 m depth.

Measurements.

ZL, 0.767−1.150 (0.948 ± 0.100); ZW, 0.468−1.050 (0.735 ± 0.116); n=32. OrL, 0.152−0.211 (0.177 ± 0.019); OrW, 0.189−0.245 (0.222 ± 0.023); n=14. AvL, 0.106−0.271 (0.171 ± 0.034); AvW, 0.096−0.193 (0.144 ± 0.024); n=28.

Description.

Colony erect, rigid, dichotomously branching, widely spreading (Fig. 7A). Branches flattened, multiserial, with zooids opening all around; 2.33−6.34 mm wide (3.34 ± 0.88 mm, n=25), five to nine zooids across (Fig. 7B). Autozooids rhomboidal, arranged in quincunx (Fig. 7B), zooidal borders indistinct. Frontal shield convex, entirely tessellated with minute depressions, with two to four small areolar pores (Fig. 8A, B) offset from margin. Orifice subcircular, about as wide as long, smooth distally, proximal margin without sinus; lyrula and condyles absent (Fig. 8C). No oral spines. Orifice deeply immersed; aperture at colony surface roughly semicircular in outline, without sinus proximally; cormidial, bounded by contributions of frontal calcification from distal and one or two lateral zooids, with suture lines sometimes evident between the sectors (Fig. 8C, D). Suboral avicularium small, proximal to orifice on the peristome periphery; circular, with complete pivot, rostrum slightly elevated, slightly denticulate, semicircular mandible directed proximolaterally (Fig. 8C, D, E); distal tooth of suboral avicularium small, rounded-conical (Fig. 8D). No other avicularia were observed. On both the edges of branches and in older part of colony, interzooidal kenozooids lacking orifice (Fig. 8F) are interspersed with autozooids; kenozooids especially numerous in the basal part of colony. Ooecium imperforate, smooth, completely immersed, not evident from colony surface; proximal margin almost straight or slightly curved, rarely obscuring the distal edge of primary orifice in oviccelate zooids (Fig. 7C).

Distribution.

Eastern part of Sagami Bay, and the Sagami Sea southwest of Jogashima and west of Ōshima, at depths of 200-493 m.

Remarks.

Examination of Ortmann’s (1890) type specimens revealed this species belongs not in Escharoides but in Buchneria , on the basis of the frontal shield with few pores, absence of oral spines, orifice without lyrula, immersed imperforate ooecium, and the suboral avicularia. Buchneria rhomboidalis is characterized by having rhomboidal zooids and flat branches. This species resembles Buchneria teres , but differs in having flat rather than cylindrical branches, in lacking a peristomial labium and sinus, and in lacking a large avicularium at branch bifurcations. The depth distribution of Buchneria rhomboidalis (200-493 m) is shallower than that of Buchneria teres (432-3660 m).