Electroejaculation of chimeric rats

Insights and implications from a comparative analysis of in vitro fertilization success in Cavioidea and Muroidea rodents

In vitro fertilization (IVF) is an assisted reproduction technique widely used due to its capacity to generate more offspring within a brief timeframe while simultaneously providing fundamental physiological data through gamete interactions. However, its suboptimal development in most species is challenging when IVF is applied to rodents. Despite numerous studies focusing on the Cavioidea and Muroidea superfamilies, some species struggle to achieve satisfactory cleavage rates, whereas others obtain over 90% efficiency with live offspring. Efforts to enhance these rates include adopting methodologies commonly used in other mammals or developing entirely new protocols. Nonetheless, the distinct morphophysiological differences among these animals necessitate careful consideration to avoid overgeneralization during optimization. Therefore, we aimed to review what has been established for the two most researched rodent superfamilies, Cavioidea and Muroidea, regarding the steps of IVF, such as gamete manipulation and embryonic development, to understand better the protocol diversification in the rodent order and how it affects IVF efficiency. After an extensive analysis of data accumulated over the years, it becomes evident that the Muroidea superfamily is used more extensively in reproductive studies than the Cavioidea. Furthermore, IVF procedures achieve total efficiency in only one rodent species, the laboratory mouse (Mus musculus). Consequently, developing a successful IVF technique across rodent species requires substantial modifications to optimize species-specific early steps - a challenge complicated by difficulties in obtaining viable gametes during the initial stages and the limited research interest in species without significant commercial value, such as wild rodents.