Plumatella casmiana (Oka, 1908)

Satkauskienė, Ingrida, Wood, Timothy, Rutkauskaitė-Sucilienė, Jurgita, Mildazienė, Vida & Tuckutė, Simona, 2018, Freshwater bryozoans of Lithuania (Bryozoa), ZooKeys 774, pp. 53-75 : 53

Plumatella casmiana (Oka, 1908) Fig. 6A, B

Material examined.

Floatoblasts, leptoblasts, and colony from Linksmakalnis pond collected from submerged branches in 20 July 2016.

Description.

Colony was about 5-6 cm long. Branches of colony are short, almost entirely attached to the substrate. The terminal parts of branches are semi-transparent and whitish. The floatoblasts were recognized by the distinctly elongated shape of the fenestra on both valves. Both capsuled floatoblasts and the distinctive leptoblasts were found, along with associated colonies (Fig. 6A, B). The surface fenestra of capsulated floatoblasts was almost smooth. Length of floatoblasts 345-432 (397 ± 15) µm; width 188-260 (214 ± 14) µm), L/W ratio 1.8; DfL 112-198 (154 ± 15) µm; DfW 90-135 (113 ± 7) µm; VfL 174-236 (205 ± 12) µm; VfW 150-195 (167 ± 8) (n=5). Leptoblasts (Fig. 6B, right side) have a uniformly narrow annulus and extensive oval fenestrae; which length was at least 1.5 times its width.

Distribution in Europe.

Plumatella casmiana is currently known throughout most of Europe ( Massard and Geimer 1995b).

Remarks on habitat and ecology in Lithuania.

This is the first reported occurrence of P. casmiana in Lithuania. Floatoblasts of P. casmiana were recorded in almost half of the investigated water bodies (Table 1). However, colonies were found in Linksmakalnis Pond only.

Remarks.

Beyond Europe P. casmiana is widely distributed through Asia, North America, Africa, and very likely other continents as well ( Wood and Okamura 2005). A unique feature is the appearance of floatoblasts lacking the inner capsule (Figure 6B, right side). This so-called leptoblast is capable of hatching immediately after release from the colony, enabling populations to grow very rapidly each season. Colonies also produce conventional capsuled floatoblasts (Figure 6B, left side) which retain the obligatory dormancy period.