Experimental evidence of early costs of reproduction in conspecific viviparous and oviparous lizards

Reproduction entails costs, and disentangling the relative importance of each stage of the reproductive cycle may be important to assess the costs and benefits of different reproductive strategies. We studied the early costs of reproduction in oviparous and viviparous lizard females of the bimodal reproductive species Zootoca vivipara. Egg-retention time in oviparous females is approximately one third of the time in viviparous females. We compared the vitellogenesis and egg-retention stages which are common to both reproductive modes. Precisely, we monitored the thermoregulatory behaviour, the weight gain and the immunocompetence of the females. Moreover, we injected an antigen in half of the females (immune challenge) to study the trade-offs between reproductive mode and immune performance, and between different components of the immune system. Finally, we experimentally induced parturition in viviparous females at the time of egg-laying in oviparous females. Oviparous and viviparous f...