In vivo research using early life stage models.

Scientists, for a variety of reasons, need to carry out in vivo research. Since experiments that require the use of adult animals pose various logistical, economical and ethical issues, the use of embryonic and larval forms of some organisms are potentially attractive alternatives. Early life stages are appealing because, in general, large numbers of individuals can be maintained in relatively simple housing, minimising costs, and their use involves fewer legal formalities. With this succinct review, we aim to provide an overview of different biological issues that have been successfully explored with the help of eggs, embryos and larvae from the frog, zebrafish and chicken.