Observations on the biology and fine structure of the type species of Chrysochromulina (C. parva Lackey) in the English Lake District

Summary

Chrysochromulina parva Lackey (type, and only known freshwater species, of the genus Chrysochromulina) has been detected in the plankton of Windermere and other lakes in the English Lake District. This is the first time that this species has been recognised outside the type locality (Scioto River, U.S.A., Lackey 1939). Observations on its behaviour in life, including seasonal and depth distributions, are recorded with the light microscope. Electron microscopy, mainly of material in culture, has added details of the fine structure. The combined results show (a) that the organism is abundant in several lakes at certain times of the year, though it had escaped detection earlier because of its extreme fragility, (b) that the cells are biflagellate, with a third filiform appendage which is a haptonema as in marine species and not a third flagellum, (c) that delicate plate-scales are sometimes detectable on the cell surface, (d) that the micro-anatomy of the main cell components is comparable to that of several marine species except for minor differences in the Golgi body and in the presence of a contractile vacuole.

An emended taxonomic description is provided.