Life-history traits in the tardigrade species Paramacrobiotus kenianus and Paramacrobiotus palaui

Although tardigrades have been studied for a long time, little is still known about their life-history traits. In the present study, two populations of the parthenogenetic African tardigrade species Paramacrobiotus kenianus, and the parthenogenetic species Paramacrobiotus palaui from the pacific islands of Palau were examined and analysed related to their life-history traits under laboratory conditions. The longevity in days (mean±SD) do not vary between the P. kenianus population (I) (125±35) and (II) (141±54), but P. palaui showed a significant shorter longevity (97±31). A recorded maximum age of 212 days was reached by P. kenianus population (II). P. kenianus population (I) laid 138±71 eggs (mean±SD) and population (II) 124±78 eggs (mean±SD) during their life, whereas P. palaui laid only 42±54 eggs (mean±SD). While the hatching time was similar in all species, starting after 6 to 9 days, the hatching rate in P. kenianus population (I) was 33%, compared with 51% of population (II) and 54% of P. palaui.