Volvox is one of the best-known chlorophytes and is the most developed in a series of genera that form spherical colonies. Each Volvox is composed of on the order of 10003000 interconnected flagellated cells that are arranged in a glycoprotein-filled sphere (coenobium). The cells swim in a coordinated fashion, with a distinct anterior and posterior, termed the 'north' and the 'south' pole. The cells have eyespots, more developed near the anterior, which enable the colony to swim towards light. An asexual colony includes both somatic or vegetative cells, which do not reproduce, and gonidia near the posterior, which produce new colonies through repeated divisions. These progeny colonies are initially held within the parent and have their flagella directed inwards. Later, the parent disintegrates and the offspring colonies invert. Volvox species can be monoecious or dioecious. Male colonies release numerous microgametes, while in female colonies, single cells enlarge to become oogametes.

Publication:
Prochnik, S.E. et al. Genomic analysis of organismal complexity in the multicellular green alga Volvox carteri. Science 329, 223-6 (2010).