Burrow residence of males and females of the mudskipper Periophthalmus modestus during reproduction

Pre-spawning reproductive behavior on the mudflat surface was reported previously for the mudskipper, Periophthalmus modestus, but it remains unknown how a pair spawns and fertilizes eggs within the spawning chamber of a burrow. In this study, we recorded reproductive behaviors from burrow entry of a pair to the departure of a female. In those cases, where spawning was suspected from a drastic reduction in the distension of the female's belly (N = 4), the female remained inside a burrow for 240-350 min without coming out onto the mudflat surface. In contrast, the male often but irregularly emerged from the burrow. In one case, a second male entered a burrow 169 min after the burrow entry of a female, resulting in her desertion from the burrow without spawning. During burrow cohabitation of the pair, burrow openings were often clogged by mud from inside. After the female left the burrow, the male remained inside the burrow for variable periods. Then, the male guarded the burrow for about one week. Upon termination of the burrow guarding, the male began excavating a new burrow near the previous one or repaired the burrow that he had guarded. A hypothesized scenario is proposed for the reproduction of this species for further investigation.