Desmid of the month
December 2019

Cosmarium hexalobum

Cosmarium hexalobum somewhat resembles C. caelatum. Like that latter species, cells of C. hexalobum are marked by deeply crenate margins and a supraisthmial inflation ornamented with longitudinal, parallel rows of verrucae. Marginal crenations are bigranulate and linked with paired radiating series of intramarginal granules. Compared with C. caelatum, however, semicells in C. hexalobum are distinctly trapeziform instead of subrectangular. In the Netherlands, C. hexalobum, having a predominantly arctic-alpine distribution, is a rare species that is only known from some sites in the northern part of the country.