The complete reproductive cycle of the mudskipper Periophthalmus novemradiatus with reference to previously documented cycle stages of other species within the genus

Abstract

This study provides the first comprehensive analysis of the entire reproductive cycle of the mudskipper Periophthalmus novemradiatus , monitoring 15 complete and three incomplete cycles filmed continuously day and night over 18 months under simulated tidal conditions. Combining behavioral quantification, burrow plaster casts, and orientation experiments, this article characterizes the species’ year-round reproductive ecology and provides a detailed comparative analysis with documented reproductive stages of congeneric species. Active mud transport was isolated from non-excavation behaviors using an empirical intra-burrow stay criterion of < 100 s. Males adapting to burrow depth significantly doubled their individual stay durations from the initial onset of digging (13.0 s) to advanced stages (27.5–34.0 s). Crucially, a massive energetic trade-off was discovered: recycling an existing burrow yielded a mechanical workload reduction of nearly 70%, requiring significantly fewer total excavation bouts (262.1 ± 123.0) than a new construction (948.6 ± 159.3; p < 0.001). Courtship analysis revealed high behavioral plasticity, with females exhibiting a significant, dichotomous separation in exit frequencies prior to spawning across different cycles ( p = 0.002). Paternal brood care lasted 8.96 ± 0.99 days, during which males fasted completely and periodically replenished the air within the established air-filled egg chamber, either utilizing the surrounding atmosphere at low tide or transporting trapped gas from the sealed upper passages during high tide. Larval hatching (3.14 ± 0.81 h; yielding 81 to 2223 larvae) was hydrodynamically facilitated by intensive male tail undulations, confirming the paternal role in larval release and solving a long-standing mystery of dispersal from hypoxic burrows. Finally, morphological tracking revealed superficial larval neuromasts becoming prominently visible from day 8 onwards, likely assisting in turbid-water spatial orientation.