Reproduction, Development and Life Cycles

In tardigrades reproduction occurs only through eggs, fertilized or
unfertilized, and therefore only through gametes. Tardigrades exploit several reproductive
modes, amphimixis, self-fertilization and thelytokous parthenogenesis (both
apomixis and automixis). These modes are often in close relationship with the
colonized environment. As regards sexuality, tardigrades can be gonochoristic
(bisexual or unisexual) or hermaphroditic. The anatomy of the reproductive apparatus
of males, females and hermaphrodites and the maturative patterns of male and
female germinal elements are presented and discussed, as well as the ultrastructure of
spermatozoa and eggs, including their phylogenetic implications. In addition, mating
and fertilization patterns, embryonic and post-embryonic development, sexual
dimorphism and parental care are considered and discussed. Finally, vegetative
reproduction does not occur in tardigrades, and their capability to regenerate is
limited to a physiological tissue restoration of a few cells.