Plumatella

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).

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.

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.

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.

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

Type species. Tubipora repens Linnaeus, 1758.