Paludicella articulata (Ehrenberg, 1831)

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

Paludicella articulata (Ehrenberg, 1831) Fig. 10

Material examined.

Two colonies from the outlet of Snaigynas Lake (Lazdijai district) were found in May 2017. Hibernaculae were not found.

Description.

The species was recognized by the slender colony branches forking at wide angles and often growing free from the substratum. Colonies were small, about 2-3 cm. Branches of colony were transparent and shiny. Zooids 1.0-1.5 mm in length with 16 tentacles on a circular lophophore were described by Pajiedaitė (1933).

Distribution in Europe.

Paludicella articulata is known worldwide ( Wood and Okamura 2005). However, the species has not been found in Poland ( Kaminski 1984).

Remarks on habitat and ecology in Lithuania.

Paludicella articulata was recorded by Pajiedaite (1933) in only two localities: Paštys Lake (Utena district) (55°42'36"N, 25°41'48"E) and Satarečius pond (Utena district). Since P. articulata tolerates cold temperatures ( Økland and Økland 2005) and prefers flowing water ( Wood and Okamura 2005) it was surprising finding of this species in stagnant Satarečius pond together with C. mucedo . Coexistence of the two species was also noted by Pajiedaitė (1933), who explained it by different local conditions in the same pond; colonies of P. articulate were observed only near a small stream flowing into the pond. Otherwise, she noted that C. mucedo was mostly observed in the warmer waters of Central and South Lithuania.

Økland and Økland (2005) showed positive co-occurrence of these two species in Norway.

During this survey P. articulata was found in the outlet of Snaigynas lake, which is of glacial origin and characterised by low temperature.

Remarks.

Colonies of P. articulata consist of sometimes creeping but more often elongated, mostly erect, slender zooids. There are normally three adjacent zooids: one distal and two lateral ones ( Davenport 1891) The contiguous arrangement of the zooids and the subterminal 4-sided zooecial orifice readily distinguish the species from its closest relative, Pottsiella erecta ( Ricciardi and Reiswig 1994).