Meeting Abstract
Monodelphis domestica is a terrestrial opossum that uses its semiprehensile tail for nest construction. The employment of this behavior is observed by age 5–7 months, when they are considered adults by their sexual maturity. Our previous study of myosin heavy chain (MHC) isoforms in the m. flexor caudae longus of adults uniquely identified pure MHC-2A fibers and more oxidative fibers in the proximal tail compared with a faster distal tail. These findings lead to hypotheses about developmental changes in MHC isoform content with tail use, specifically (i) juveniles should express fast developmental isoforms, in addition to having a large composition of fast MHC-2B throughout the tail, and (ii) at ages 3-5 months the developmental isoforms will transition into adult MHC-1 and 2A fibers, while MHC-2B will shift to the 2X isoform, each corresponding with the onset of nest construction behavior. To test these hypotheses, caudal muscle was harvested post-mortem from individuals ranging in age from 1–7 months, and MHC expression was quantified by RT-PCR, SDS-PAGE, and gel densitometry. To further evaluate how MHC isoform transitions correlate with nest construction, video data of tail use from individuals in different age groups (3 months to adulthood) was also collected and will be analysed for frequencies of tail behaviors. Preliminary data from protein gel analysis indicate that there is a shift from a fast MHC isoform content in the juveniles to a slower composition in the adults. With the complete results of this study we will understand adult MHC expression as it relates to development of tail prehensility in didelphids and more generally, how frequency of use of an appendage influences muscle fiber type properties.
