Magnetic resonance imaging of ovaries in the mud crab Scylla paramamosain during vitellogenesis

BACKGROUND: Ovarian assessment and monitoring are crucial for reproductive management and breeding programs in animal production. Currently, there is a lack of quantitative and non-invasive methods for ovarian assessment and monitoring in crab species. In the present study, magnetic resonance imaging (MRI) was utilized to characterize the ovarian morphology of mud crabs during vitellogenesis. RESULTS: The ovaries exhibited low signal intensity in T2-weighted magnetic resonance images and displayed intermediate signal intensity in T1-weighted magnetic resonance images. The ovarian shape varied topologically among different cross-sectional images and changed considerably across different developmental stages. From the early to late stages, the ovaries increased in size, as determined by MRI measurements at the eyes in the sagittal plane and at the commissure of the ovaries, heart, and flank in the transverse plane, which were positively correlated with values of the gonadosomatic index (GSI). The GSI was well-plotted against MRI measurements using two-variable linear regression. Among them, five regression models appeared promising for estimating GSI values in ovarian assessment of live mud crabs. The growth of the ovaries was documented in three mud crabs through repeated MRI scans, suggesting that this non-invasive method could be employed for longitudinal monitoring. CONCLUSIONS: Our findings demonstrate the application of MRI for ovarian assessment and monitoring in mud crabs, providing new insights into assisted reproductive technology in decapods.