The diversity and phylogeny of the commercially important algal class Eustigmatophyceae, including the new clade Goniochloridales
A new family Loboceae E. Hegewald, a new genus Pseudotetraëdriella E. Hegewald, and a new species Pseudotetraëdriella kamillae E. Hegewald et J. Padisák are described. The species differs markedly from the described species with tetralobular/quadrangular shape like Tetraëdron (Chlorophyta) or Tetraëdriella (Xanthophyceae); differences to other morphologically similar species (Tetraëdron minimum f. brachiata Printz, T. minimum f. tetralobulatum Reinsch, T. minutissimum Korsh., T. mediocris Hindák, T. quadrilobatum G. M. Smith, T. regulare Kützing, Tetraëdriella jovetii (Bourr.) Bourr. (=Pseudostaurastrum jovetii Bourr., Polyedrium minimum f. tetralobula Reinsch) are discussed. 18S rDNA sequence analyses demonstrated its close relationship with a morphologically different, aerophytic species, Monodopsis subterranea, within the class Eustigmatophyceae (Heterokontophyta). Pseudotetraëdriella kamillae is typically occurring in the cold season (autumn-winter-spring), commonly in small amounts. Quantitative data from the stratifying, oligotrophic Lake Stechlin, N. Germany show that the population growths in the early spring isothermal period with an estimated doubling time of 46 days. Being a non-motile species, its abundance falls below detection level during the stratification period. In the period 1995–2002 with weekly-biweekly sampling its maximum abundance was recorded as 2.24 μg L-1, corresponding to 0.41% of total biomass.