The Development of Cytoplasmic Bridges in Volvox Aureus

Abstract

The structure and develop~nex$ of cytoplasnlic bridges connecting adjoining cells in T/ohox nureus coenobia IS de~nonstratecl by electron ~nicroscopy. The cytoplas~llic connections originate Iron1 incomplete cell division. I n the early stages, mitochonclria and other smaller organelles may move lreely lrom one cell to the nest. 'The cytoplas~nic bridges then stretch as the cells separate lron~ each other during maturation of the colony. \\Then they are lully stretched, only encloplast~~ic ret-ic~~lurn a n d ribosomes are lot~ncl in thcse cytoplas~i>ic stra~lds. , .I he nature ol these cytoplasmic connectiolls is discussecl and it is concluded that they should be distinguished f;?111 plas~>lodes~llat;lol highcr plants and the structures should be callccl simply cytoplasmic bridges". I t is also reported that the matrix ol the colonial \vall is clerived Irom the dictyosome activity cluring the coenobium clevelopment. 65) is the srun~e as i~sed by Stein (1965) in a light microscope stud>, of cytoplasmic strands. r .

Embryogenesis and cell positioning inPlatydorina caudata(Volvocaceae, Chlorophyta)

“…The cytoplasmic bridges in Volvox are formed by incomplete cytokinesis (Pocock 1933;Bisalputra & Stein 1966;Deason et al 1969;Pickett-Heaps 1970;, and incomplete cytokinesis is considered as one of the steps for evolving multicellularity (Kirk 2005). In this study, the presence of a cytoplasmic bridge system was confirmed in P. caudata.…”

“…The cytoplasmic bridge system is widely recognized in volvocine algae (Bisalputra & Stein 1966;Marchant 1976Marchant , 1977Fulton 1978;Hoops et al 2005) and thought to be one of the most important steps in the evolution of multicellularity in this group (Hoops et al 2005). The cytoplasmic bridges in Volvox are formed by incomplete cytokinesis (Pocock 1933;Bisalputra & Stein 1966;Deason et al 1969;Pickett-Heaps 1970;, and incomplete cytokinesis is considered as one of the steps for evolving multicellularity (Kirk 2005).…”

Mitosis, cytokinesis and colony formation in the colonial green algaAstrephomene gubernaculifera

“…The presence of cytoplasmic bridges between cells of the developing colonies is of considerable interest since similar bridges are found in many of the Volvocaceae (Bisalputra & Stein, 1966;Ikushima & Maruyama, 1968;Deason et al, 1969;Pickett-Heaps, 1970;Deason & Darden, 1971;Gottlieb & Goldstein, 1977;Marchant, 1977;Birchem & Kochert, 1979). In some members of the Volvocaceae these bridges remain in the adult colony, while in others, as in Astrephomene, the bridges disappear during development.…”

Volvocine Algae: From Simple to Complex Multicellularity

“…In all members of the Goniaceae and Volvocaceae, during early embryonic development cells are connected through cytoplasmic bridges resulting from incomplete cytokinesis (Gerisch 1959;Bisalputra and Stein 1966;Gottlieb and Goldstein 1977;Marchant 1977;Fulton 1978;Green et al 1981;Iida et al 2013). These bridges ensure the stability of the early embryo.…”