The effects of irradiance levels and spectral composition on mating strategies in the snow alga,Chloromonas sp.-D, from the Tughill Plateau, New York State

The importance of light and photoperiod in sexual reproduction and geographical distribution in the green snow alga,Chloromonas sp.-D (Chlorophyceae, Volvocales)

“…Haploid spherical cells were observed in Chlamydomonas eugametos and in Chloromonas sp.-D. In both species, an increase of spherical cells was noted through time when grown on nutrient deprived media, but the mechanism of formation of spherical cells was thought to be through cell packs in Chloromonas sp.-D as it is for oblong cells (Hoham et al, 1997). In addition, Chloromonas sp.-D rarely produces abnormal Vshaped mitotic divisions where haploid biflagellate oblong cells divide longitudinally (Behrstock et al, 1998, personal communication).…”

“…The inter-relationships between snow algal life cycles and their surrounding physical and chemical factors have been reviewed (Hoham and Duval, 2000;Hoham and Ling, 2000) and include discussions on hydrological processes. These green algal flagellates occur in snow at the time when liquid water, nutrients and dissolved gases are available and solar irradiance penetrates through the snowpack (Hoham et al, 1998). These algae require liquid water in order to swim around the more solid snow crystals, they position themselves according to irradiance levels and spectral composition, and eventually cause visible colors in the snowpacks of green, orange or red (Hoham and Duval, 2000).…”

“…Changes in the wavelength and intensity of light often elicit a response in the cell cycle and mating strategy of these organisms. Life histories of Chloromonas pichinchae (Hoham, 1975), c. nivalis Mullet, 1977, 1978), c. brevispina , c. polyptera (Hoham et al, 1983) and c. rubroleosa (Ling and Seppelt, 1993) were examined from snowpacks in the field, while the mating process in Chloromonas sp.-D was investigated in the laboratory (Hoham et al, 1997(Hoham et al, , 1998. Mating studies in the closely related Chlamydomonas (Beck and Treier, 1991;Quarmby and Hartzell, 1994) provide insight into the cell cycle of Chloromonas (Hoham et al, 1997).…”

“…Sexual reproduction in Chlamydomonas is initiated when the flagella of gametes from opposite mating types (mtC and mt ) come into contact through agglutination (Kooijman et al, 1988), which results in their adhesion, entwining and eventual pairing (Lewin, 1956;Van Winkle-Swift, 1977;Tomson et al, 1990). In Chloromonas sp.-D, gametes involved in syngamy are either oblong or spherical, matings can be isogamous or anisogamous, and quadriflagellate zygotes are produced (Hoham et al, 1998). In snow algae, zygotes lose their flagella and develop into thickwalled resting zygospores that withstand desiccation after snowmelt.…”

“…The daughter cells released from the zygospores produce cell packs, and the cells released from the cell packs further divide to increase the algal population in the snowpacks (Hoham, 1980). In its natural habitat, Chloromonas pichinchae is found in the top 10 cm of snowpacks where blue light (440 nm) irradiance levels are higher than those of other parts of the visible spectrum (Hoham, 1975), and blue light also promotes optimal mating in Chloromonas sp.-D (Hoham et al, 1998). Blue light activates a carotenoid trigger in Chlamydomonas reinhardtii that causes the accumulation of glutamate-1-semialdehyde aminotransferase (gsa) mRNA, which results in a sudden increase in chlorophyll production (Matters and Beale, 1995).…”