Plumatella Lamarck, 1816

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 : 3-4

Genus Plumatella Lamarck, 1816

Type species. Tubipora repens Linnaeus, 1758 .

Diagnosis. Colony composed of branching tubules, well chitinized; ectocyst varies in thickness and form depending on the species, the age of the colony and the environment. Colonies produce both floatoblasts and sessoblasts; a type of floatoblast called a leptoblast that lacks the internal capsule has been reported only from Plumatella casmiana .

Plumatella casmiana Oka, 1907b: 121 , fig. 3; Rogick 1941: 211, pl. 1(1–4), pl. 2(5, 6); 1943: 265, pl. 1(1–8); Toriumi 1955b: 76, text-figs 1–3; Mukai 1999: 56, figs 3D, 4D, 4E, 6E; Wood & Okamura 2005: 46, 78, figs 16–18, 45–46; Wood et al. 2006: 12, figs 11–13.

Plumatella repens var. annulata Hozawa & Toriumi, 1940: 428 , fig. 3; 1941: 236, fig. 3, pl. 14(2); Rogick & Brown 1942: 131, pl. 2(10, 14–16, 26), pl. 3(30).

Plumatella repens var. casmiana: Toriumi 1941a: 203 , fig. 7, pl. 12(4–5), pl. 13(15); 1942: 209, figs 1–3.

Material examined. Several floatoblasts and leptoblasts from a pond in the city of Okinawa; small colonies with sessoblasts from Kanna Dam, village of Ginoza.

Description. Colony variable; tubular, light brown, almost entirely attached to substratum; compact colonies sometimes assuming a honeycomb-like shape; tentacle number about 21–25 ( Hozawa & Toriumi 1940; Bushnell & Wood 1971). Two types of free floatoblasts, the normal plumatellid floatoblast (capsuled floatoblast) and another lacking the internal capsule (leptoblast). In sampled Okinawan population, the capsuled floatoblast is oval, 334– 369 (348±11) μm long by 192–212 (203±7) μm wide (n=10), with length/width ratio of about 1.7, symmetrical in lateral view; surface of fenestra with weak tubercles or sometimes almost smooth ( Fig. 2 A). Leptoblast elliptical, longer than capsuled floatoblast, 369–390 (378±11) μm long by 164–197 (179±17) μm wide (n=3), with length/ width ratio of about 2.1. Sessoblast 285–312 (296±11) μm long by 206–232 (224±12) μm wide (n=4), with length/ width ratio of about 1.3; annulus wide and smooth, the surface of the capsule smooth ( Fig. 2 B).

Distribution. Distributed worldwide ( Bushnell 1973; Wood et al. 2006); recently reported from Thailand ( Wood et al. 2006); widely distributed in Japan, from Okinawa to northern Hokkaido.

Remarks. Rogick (1941, 1943) showed detailed drawings of the colony and statoblasts of P. c a s m i a n a from North America.

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.