25 August 2008 Appearance of Males in a Thelytokous Strain of Milnesium cf. tardigradum (Tardigrada)
Atsushi C. Suzuki
Author Affiliations +

Tardigrades are generally gonochoristic. Many moss-dwelling species propagate by parthenogenesis, but heterogony has not yet been found. Milnesium tardigradum, a carnivorous tardigrade, also has both sexes, but males are usually rare and many populations appear to have only parthenogenetic reproduction. Since 2000, I have maintained a thelytokous strain of Milnesium cf. tardigradum that originated from one female. Individuals of this strain were thought to be all females, but here I report that males have emerged in this strain at a very low frequency. This is the first report of the appearance of males in parthenogenetic tardigrades. On the first pair of legs of some individuals, I observed the modified claws characteristic of males of this species. It is unknown whether these males can actually function in sexual reproduction; however, they might allow some possibility of genetic exchange among clonal populations. No environmental factors that generate males were determined.

Atsushi C. Suzuki "Appearance of Males in a Thelytokous Strain of Milnesium cf. tardigradum (Tardigrada)," Zoological Science 25(8), 849-853, (25 August 2008). https://doi.org/10.2108/zsj.25.849
Received: 31 December 2007; Accepted: 20 May 2008; Published: 25 August 2008
sex ratio
sexual dimorphism
Get copyright permission
Back to Top