The reproductive biology of Aspidoscelis, particularly the known parthenogenetic species, has fascinated herpetologists for decades. In order to understand parthenogenesis within Aspidoscelis, which has evolved multiple times following hybridization events between distinct sexual species within the genus, it is imperative to comprehend underlying reproductive mechanisms and strategies inherent in the sexual ancestors. Through comprehensive genomic analyses, including RADseq data and synteny mapping, this study investigates sex determination mechanisms and identifies punitive sex-linked loci in two sexual Aspidoscelis species. The analysis reveals markers potentially associated with sex differentiation, offering insights into the chromosomal evolution and genetic basis of reproduction in these lizards. Despite challenges in identifying sex-linked loci using existing methods, the FST-based approach adopted here proved promising, with its ability to highlight genomic regions potentially involved in sex determination. Our findings suggest that chromosome 13 in A. gularis is homologous to the previously identified sex chromosome 3 in A. tigris. This study contributes to understanding the intricate genetic processes underlying parthenogenesis and karyotypic evolution in Aspidoscelis, paving the way for future studies elucidating the complexities of reproduction in vertebrates.

This study examined bite force generation in American monkfish (Lophius americanus) and how it scaled with size, focusing in particular on the roles of the quadratomandibularis (QM) muscle and mechanical advantage in jaw closure in this species. Considering the feeding strategy of other anglerfishes, it was hypothesized that monkfish would trend towards force optimization rather than speed optimization in terms of the jaw closing system. The data revealed that bite force has a slightly positive allometric scaling relationship with size, while mechanical advantage was constant throughout growth. Maximum theoretical bite force ranged from 8 N to 87 N, with total lengths ranging from 17 cm to 51 cm. When comparing the bite force of the American monkfish to that of 10 other fish species, small monkfish exhibit a bite comparable to similarly sized species. However, larger monkfish were estimated to have a stronger bite than organisms of similar size.