Comparative effects of critical point and air-drying on the morphology of the rigid mucilaginous coating (lorica) of Trachelomonas (Euglenophyceae)

Abstract

Abstract In the past, with light microscopy, species of the genus Trachelomonas have been classified according to the shape and ornamentation of the lorica. In the present work a comparison has been made between the morphology of the lorica of various species of Trachelomonas as seen by scanning electron microscopy following the use of air-drying as compared with the critical point method in order to evaluate the use of these two procedures for taxonomic purposes. With critical point drying, but not with air-dying, the lorica in all species was seen to consist basically of cylindrical strands and globules of mucilage about 0·08 μm in diameter; in T. volvocine the lorica consisted of two distinct layers. In air-dried preparations the strands and globules aggregated and became indistinct; individual strands, which in critical point dried preparations were sometimes connected to spines or collars, were destroyed and the punctae were reduced in size. However, since the more general features of the loricas were similar in both air-dried and critically point dried preparations, air-drying is adequate for most taxonomic purposes.