Mudskippers brood their eggs in air but submerge them for hatching

Abstract

SUMMARY Intertidal mudflats are highly productive ecosystems that impose severe environmental challenges on their occupants due to tidal oscillations and extreme shifts in habitat conditions. Reproduction on mudflats requires protection of developing eggs from thermal and salinity extremes,O2 shortage, dislodgement by currents, siltation and predation. Mudskippers are air-breathing, amphibious fishes, and one of few vertebrates that reside on mudflats. They lay their eggs in mud burrows containing extremely hypoxic water, raising the question of how the eggs survive. We found that the Japanese mudskipper Periophthalmus modestus deposits its eggs on the walls of an air-filled chamber within its burrow. To ensure adequate O2 for egg development, the burrow-guarding male mudskipper deposits mouthfuls of fresh air into the egg chamber during each low tide, a behaviour that can be upregulated by egg-chamber hypoxia. When egg development is complete the male, on a nocturnal rising tide, removes the egg-chamber air and releases it outside the burrow. This floods the egg chamber and induces egg hatching. Thus, P. modestus has developed a reproductive strategy that allows it to nurture eggs in this severe habitat rather than migrating away from the mudflat. This requires that mudskipper eggs be specialized to develop in air and that the air-breathing capacity of the egg-guarding male be integrated in a complex behavioural repertoire that includes egg guarding, ferrying air to and from the egg chamber, and sensing O2 levels therein, all in concert with the tidal cycle.

Food preference of the giant mudskipperPeriophthalmodon schlosseri(Teleostei : Gobiidae)

“…Another possibility is female P. schlosseri has been chased off from the male's burrow after laying their eggs. According to Sayer (2005) and Ishimatsu et al (2007), the female will be driven out from the burrow after mating. The male P. schlosseri assumes broodcare responsibilities.…”

Fish embryos on land: terrestrial embryo deposition lowers oxygen uptake without altering growth or survival in the amphibious fishKryptolebias marmoratus

“…For example, California grunion (Leuresthes tenuis) spawn in damp sand, which offers embryos physical protection and higher oxygen levels relative to water (Walker, 1949;Darken et al 1998;Martin et al, 2011). The Japanese mudskipper Periophthalmus modestus incubates embryos in air-filled chambers under water, built into mudflats and filled with air by the action of the parents (Ishimatsu et al, 2007). Mummichog (Fundulus heteroclitus) embryos are periodically exposed to an aerial environment during low tides where they hatch earlier relative to embryos in water (Taylor et al, 1977;Tingaud-Sequeira et al, 2009.…”

Amphibious fishes: evolution and phenotypic plasticity

“…Other groups -including oxudercine mudskippers (e.g. Ishimatsu et al, 1998Ishimatsu et al, , 2007, stichaeid pricklebacks (e.g. Coleman, 1992) and aplocheiloid killifishes (e.g.…”