Hyalinella punctata (Hancock, 1850)

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

Hyalinella punctata (Hancock, 1850) Fig. 8

Material examined.

A few statoblasts from Veršvio stream were found in August 2015 Unfortunately, these were later lost before critical dimensions could be taken.

Description.

Colonies were not observed, and species was identified according floatoblasts. The statoblasts are larger than any other plumatellid species and show crowded tubercles on the fenestrae of both valves. Pajiedaitė (1933) described floatoblasts by oval shape, with length 440 µm and width 230 µm. These dimensions were slightly smaller than 500 µm and 350 µm suggested by Wood and Okamura (2005). Length and width of measured statoblasts during current study was 425-459 (444 ± 7) and 280-299 (290 ± 4) µm, respectively (n=5).

Distribution in Europe.

Hyalinella punctata has been widely reported worldwide, including neighbouring Poland ( Kaminski 1984), but verified specimens are known only from Britain, Ireland, Europe, North America and northern Asia ( Wood and Okamura 2005).

Remarks on habitat and ecology in Lithuania.

Few small colonies of H. punctata were described on Nymphaea lutea leaves in small lakes in the Zarasai district (55°44'50"N, 25°50'4"E) and Dubysa river ( Šiauliai district; 55°51'29"N, 23°08'31"E) by Pajiedaitė (1933). During the present survey, floatoblasts of H. punctata were recorded only in the Veršvio stream (Table 1). The available data are not sufficient to estimate the prevalence and frequency of this species in Lithuania.

Remarks.

Hancock (1850) described colonies of H. punctata as "thick and transparent with less profuse branching than in Plumatella and produce only floatoblasts, while individual zooids are indistinct, usually arranged linearly and lack interzooidal septa". In fact, features distinguishing Hyalinella from Plumatella are not clear-cut ( Hirose and Mawatari 2011), because the diagnosis of Hyalinella is based on the transparency and thickness of the colony wall (ectocyst), but the condition of the ectocyst depends to some extent on environmental factors ( Wood and Okamura 2005, Hirose and Mawatari 2011). Generic placement of some species between Plumatella and Hyalinella has remained unstable ( Hirose and Mawatari 2011).