Responses of the egg-tending gobiid fish Valenciennea longipinnis to the fluctuation of dissolved oxygen in the burrow

Responses of the egg-tending male Valenciennea longipinnis (Gobiidae), a species inhabiting the near-shore moat on coral reefs, to the fluctuation of dissolved oxygen (D.O.) concentration in its enclosed burrow, were studied. D.O. concentration in egg-tending burrows decreased from high tide to low tide during the daytime. D.O. concentrations in 12 egg-tending burrows at low tide ranged from 2.17–4.50 ml D.O. L⁻¹ (43.8–91.9% D.O. saturation) on the day after spawning. In the laboratory, an egg-tending male increased the frequency and duration of fanning as D.O. concentration decreased. Below about 1.2 ml D.O. L^–1 (about 25% D.O. saturation), the frequency of fanning began to decrease. The frequency and duration of fanning increased with developmental stage of the eggs, perhaps in response to an increase in oxygen consumption of eggs with developmental stage. The rapid adjustments of fanning behavior to D.O. concentration in the burrow and developmental stage of the eggs showed indirectly that the primary role of fanning is a supply of oxygenated sea water to the eggs.