Marine Biology (2+1)

Reproduction

           Diatoms reproduce mainly by simple fission i.e. each diatom divides into two halves.  Each half will then develop a new inner valve so that the typical box like structure of cell is recreated.  Since this process continues through several generations, the average size of the diatom population gets decreased.  As a result, individuals of diatom species vary in size among the population i.e. some are large and many are small.  The very tiny ones can no longer undergo divisions and at that time they cast-off both upper and lower valves and become a structure called an auxospore.  This spore, develop  new valves of upper and lower with the original size of the parent cell size  of the diatom species. This process is called restoration of cell size.  Though this is the general mechanism of diatom reproduction and reestablishment of size, there are some diatoms which undergo division of cells without reduction of valve size and hence, without auxospore formation.