portrait

Description:

Cosmarium (coz-mare-ee-um) tetraophthalmum is a very common and large genus of phytoplankton alga found usually in oligotrophic, acid waters. The cells of this genus are composed of two semi-cells, constricted in the middle. This region in the middle is called the isthmus and is the site of the nucleus. The outer portions of each semi cell contains a single, large chloroplast. The outer cell wall of each semi-cell are covered with pores and can be very ornate and the appearance can be used to define the species. The cells are move slowly as the result of mucilage secretion. Both asexual and sexual reproduction occurs. The asexual activity is cell division and the sexual reproduction involves the formation of zygospores. The gametes migrate from the parental cell walls through pores and fuse in a region midway between the parental walls. The zygote can form a very ornate wall. This specimen was collected in a moor located in the Salzburger Land, Austria.