Formation and reproductive significance of chest spines in Quasipaa spinosa

Male spiny frogs ( Quasipaa spinosa) develop seasonal chest spines during the breeding season, but the structural basis, molecular changes, and reproductive role of this trait remain unclear. Therefore, to clarify how structural and molecular remodeling of the chest skin work together to form this important reproductive trait, we performed AB-PAS histological staining, quantitative proteomic analysis, and real-time quantitative PCR validation on male skin tissues. We then combined these analyses with spine blunting, reproductive competition experiments, and SSR-based paternity testing to examine chest spine formation and its relationship with male reproductive success. We found that Q. spinosa chest skin has specialized glandular structures and a collagen-rich dermal framework, suggesting that it provides a structural basis for later spine development. During the reproductive cycle, chest spine formation is accompanied by significant changes in extracellular matrix (ECM)-related proteins and pathways, including focal adhesions and ECM–receptor interactions. Moreover, the expression of genes related to the TGF-β/Smad signaling pathway and matrix remodeling was dynamically altered during this process. Reproductive experiments revealed that males with better-developed chest spines produced more offspring, whereas artificial blunting of the spines reduced reproductive success. Together, these results suggest that seasonal chest spine formation in Q. spinosa is closely related to extracellular matrix remodeling and contributes to male reproductive success during the breeding season. These findings provide practical implications for broodstock selection, conservation breeding, and the management of reproductive fitness in amphibian populations. In particular, chest spine development may serve as a practical indicator of male reproductive performance, linking an evolutionarily selected secondary sexual trait to reproductive management.