Plumatella emarginata Allman, 1844

Hirose, Masato & Mawatari, Shunsuke F., 2011, Freshwater Bryozoa of Okinawa, Japan, with descriptions of Rumarcanella gen. nov. (Phylactolaemata: Plumatellidae) and two new species, Zootaxa 2732, pp. 1-19 : 4-5

Plumatella emarginata Allman, 1844

( Figure 2 C)

Plumatella emarginata Allman, 1844a: 330 ; Allman 1856: 104, pl. 7(5–10); Braem 1890: 9, pl. 1(9, 12, 14); Annandale 1911: 220, pl. 3(2), pl. 4(1, 1a); Toriumi 1954: 287, pl. 8(1–47); 1971: 127, pl. 12(3); Mukai 1999: 51, figs 2A, 3C, 5A, 7A (part); Wood & Okamura 2005: 51, 80, figs 21, 47, 48.

Plumatella repens var. emarginata: Rogick 1935a: 246 , 255, pl. 41(6); 1940, 198, pls. 1(1–3), 3(11, 12). Hozawa & Toriumi 1940: 427, fig. 2, Pl. 1(7); 1941: 234, fig. 2, pl. 14(7). Toriumi 1941a: 198, fig. 3, pl. 12(6, 9); 1941b: 416, fig. 3; 1942: 208, figs. 3–6.

Material examined. Floatoblast from pond in city of Uruma; floatoblasts from Ryutan-ike pond next to the castle, city of Naha; floatoblasts and colony with floatoblasts and sessoblasts from Fukuji Dam, village of Higashi; floatoblasts and colony with floatoblasts and sessoblasts from Benoki Dam, village of Kunigami.

Description. Observed colonies tubular, branching, shiny dark brown or well encrusted. Tentacle number 20 to 50. Floatoblasts in Okinawan populations elliptical, elongate, 329–527 (427±67) μm long by 211–248 (226±11) μm wide (n=10), with length/width ratio of about 1.9 ( Fig. 2 C); fenestra of ventral valve almost circular, more than four times diameter of fenestra of dorsal valve; both ventral and dorsal fenestrae covered with tubercles; annuli textured with coarse pavement; floatoblast valves asymmetrical in lateral view, the ventral valve convex, the dorsal almost flat. Sessoblasts with tuberculate surface and smooth annulus, 437–466 (451±12) μm long by 273–301 (282±13) μm wide (n=4).

Distribution. Broadly distributed worldwide; distributed in Japan from Okinawa to Hokkaido.

Remarks. Floatoblasts of P. emarginata from Okinawa are larger than in other regions (average length 427 μm; SD 67.0) and sometimes have strongly elevated tubercles. Colonies and floatoblasts appear to be variable in form, and the nominal species may include several synonymous species. Although we did not observe sessoblasts of this species from Okinawa, we identified our material as P. emarginata on the basis of the floatoblast and colony morphology.

Figures

FIGURE 2. SEM micrographs of statoblasts from three phylactolaemate species from Okinawa. A, Plumatella casmiana Oka, 1907, floatoblast, dorsal view. B, Plumatella casmiana, sessoblast. C, Plumatella emarginata Allman, 1844, floatoblast, ventral view. D, Plumatella mukaii Wood, 2001, floatoblast, ventral view. E, Plumatella repens (Linnaeus, 1758), floatoblast, dorsal view. Scale bars: 100 μm.