Phenotypic Variations in the Life History of Two Clones of Macrobiotus richtersi (Eutardigrada, Macrobiotidae)

Abstract

A comparative study of life history traits of two clones (CDMr01 and CDMr02) of a triploid thelytokous apomictic population of the eutardigrade Macrobiotus richtersi has been carried out. Both clones were reared under the same lab conditions: temperature of 14°C, photoperiod of 12 h/12 h (L/D), and nematodes ad libitum as food. Statistical analysis of the life history traits considered has indicated interclonal variability. The two clones were significantly different in the number of eggs per clutch (fertility), number of eggs laid per female per life span (fecundity), hatching percentage of eggs and hatching time. Similarities between clones have been observed with regard to life span, total number of ovipositions per life span, and age at first oviposition. In addition, significant differences in hatching time, with eggs hatched over a long period, were found within each clone. Interclonal variability in life history traits indicated the effects of genetic factors, whereas intraclonal variability reflected the effects of environmental factors. The evolutionary and adaptive significance of the life history phenotypic variations is discussed.

Effect of lifespan and age on reproductive performance of the tardigrade Acutuncus antarcticus: minimal reproductive senescence

“…While the hatching time of A. antarcticus was very stable across individuals in the current study, observations of a different population of the same species using a different rearing method indicate the possibility of phenotypic plasticity over generations in some of the reproductive parameters examined here including hatching time and success (Altiero et al, 2015). High variability in hatching time has also been reported within clones of the eutardigrade Macrobiotus richtersi (Altiero et al, 2006(Altiero et al, , 2010. In the population of parthenogenetic tardigrade A. antarcticus studied here, while the duration of the period from last oviposition to death increased slightly with lifespan, the majority of the individuals continued oviposition until shortly before death, with no suggestion of a post-reproductive lifespan which is typical in mammals and also in some invertebrate groups (Cohen, 2004;Jones et al, 2014).…”

“…In addition to the few earlier laboratory studies focused on life history (Baumann, 1964;Dougherty, 1964), traits of several tardigrade species in culture have been described in detail in the last decade (Altiero & Rebecchi, 2001;Suzuki, 2003;Altiero et al, 2006Altiero et al, , 2010Altiero et al, , 2015Hohberg, 2006;Lemloh et al, 2011;Schill, 2013;Tsujimoto et al, 2015). These studies quantified species-specific or population-specific traits including lifespan, age at first oviposition, clutch size, total number of oviposition events, the number of eggs produced per individual and egg development time.…”

Sexual dimorphism, population dynamics and some aspects of life history of Echiniscus mauccii (Tardigrada; Heterotardigrada)

“…In one study, it seems that terrestrial tardigrades need periods of being in the tun to aid in their longevity and survival (Suzuki 2003). A similar laboratory study was done by Altiero et al (2006) on Macrobiotus richtersi Murray, 1911 (a limno-terrestrial eutardigrade) specifically looking for aspects of life history such as life span, clutch sizes, and age at different ovipositions. In this study two clones (due to apomictic parthenogenesis) were taken through a few generations in a laboratory setting.…”

Energy allocation in two species of Eutardigrada

“…It has been proven that under laboratory conditions M. richtersi has a very long active lifespan (more than one year; Altiero et al 2006). The long lifespan of M. richtersi allows a high investment of energy for somatic growth and consequently high amount of energy for reproduction (RRE is higher when the animals are larger).…”

“…Data on tardigrade life histories are still limited (Suzuki 2003;Altiero et al 2006;Hohberg 2006) and energy allocations for reproduction and associated trade-offs have been little investigated.…”