PRODUCTION OF MALE GAMETES AND AUXOSPORES IN THE CENTRIC DIATOMS CYCLOTELLA MENEGHINIANA AND C. CRYPTICA¹²

Abstract

Vegetative cells of Cyclotella meneghiniana Kützing form male gametes and anxospores following transfer from a synthetic freshwater medium to a modified artificial seawater. Both spermatogenesis and auxospore formation are correlated with an increase in the Na(+) concentration in the medium. Spermatogenesis can also be induced in C. cryptica Reimann, Lewin, and Guillard in artificial seawater with an adjusted sodium level.

Sex allocation pattern of the diatomCyclotella meneghiniana

“…The size of the cell that differentiates into an egg has a positive correlation with the size of the fully expanded auxospore (and hence with the initial vegetative cell size) in several centric diatoms [27]. By contrast, the number of sperm produced by one cell is not affected by cell size in C. meneghiniana [12]. These observations suggest that allocation of larger cells to females more effectively restores cell size in the next vegetative cycle.…”

An assessment of cryptic genetic diversity within theCyclotella meneghinianaspecies complex (Bacillariophyta) based on nuclear and plastid genes, and amplified fragment length polymorphisms

“…Based on her observation of large genetic variation and paraphyly of plastid RFLPs, Bourne (1992) considered that it might be a complex of several species. On the other hand, Drebes (1977) suggested that C. meneghiniana had abandoned allogamy: although sexual reproduction had been studied intensively in this species (Iyengar & Subrahmanyan, 1944;Schultz & Trainor, 1968;Rao, 1970Rao, , 1971Rao, , 1996Ha˚kansson & Chepurnov, 1999), no observations of allogamous fertilization have ever been published.…”

Gametogenesis, gametes and zygotes: An ecological perspective on sexual reproduction in the algae

“…Rapid changes in environmental factors such as salinity (diatoms: Schultz & Trainor, 1968) and pH (e.g. Pediastrum duplex Meyer: Wilcox & Floyd, 1988) can induce gametogenesis.…”