In the fern Ceratopteris richardii, gametophyte sex is strongly influenced by a hormone called antheridiogen. In the absence of antheridiogen, gametophytes tend to develop into hermaphrodites that then secrete their own antheridiogen. In its presence, gametophytes tend to develop into males. Males require the continued presence of antheridiogen to remain male. With antheridiogen removal, males may convert to hermaphrodites. Such a situation would occur following fertilization and the subsequent development of the sporophyte. Here we explore whether hermaphrodite density, male age, and male size affect the length of time it takes males to convert to hermaphrodites. Males were grown in three hermaphrodite densities for three separate lengths of time (14, 20, and 26 days). Males were removed from the presence of hermaphrodites (i.e., antheridiogen) and placed individually into new dishes. Sizes of males were measured at the time of transfer; males were monitored every 12 hours for signs of conversion. Size of male served as a covariate in a two-factor analysis of covariance.
Results/Conclusions
The time to conversion of males to hermaphrodites ranged from 5 to 18 days, and all males converted over the course of the experiment. Overall, larger males converted faster than smaller males. Males growing in the lowest density of hermaphrodites (lowest antheridiogen concentration) converted faster than males growing in either of the two higher hermaphrodite densities. Older males (26 days old) converted faster than 20-day-old or 14-day-old males. Antheridiogen is known to be an important factor influencing the conversion of males to hermaphrodites. Results here suggest that male attributes (size and age) as well as the male’s experience with antheridiogen (concentration) influence conversion. With the removal of antheridiogen, larger, older males are more likely to convert. As these males convert, they begin to produce their own antheridiogen that would, in turn, influence smaller, younger males in the neighborhood to remain male.