ブリの鰓換水

Ventilation in the yellowtail, Seriola quinqueradiata (Perciformes : Carangidae)

Creators Yamamoto Ken-ichi

Creators Handa Takeshi

Creators Yokota Motohiro

Creators Yoshida Satoshi

The ventilation of the yellowtail, Seriola quinqueradiata (active marine teleost) was examined by directly measuring the ventilation volume, the water pressures in the buccal and opercular cavities, and the difference of the water pressures under the normoxic and hypoxic conditions. The flow velocities in the mouth, the gill slit and the secondary lamella, and the mean flow areas of the water course over the three parts were calculated using the values of the parameters measured. Under severe hypoxic condition, the ventilation volume and the mean flow velocities were higher than those under the normoxic condition. The venltilation volume increased to 5.00l/min/kg which was nearly 5 times as high as 1.01l/min/kg under the normoxic condition. The mean flow velocities were elevated from 39.7cm/sec to 71.5cm/sec at the mouth and from 33.6cm/sec to 50.3cm/sec at the secondary lamella. However, the velocity at the gill slit was 35.5-38.4cm/sec and roughly constant. The mean flow areas were also broardened from 0.69cm 2 to 1.59cm 2 at the mouth, from 0.83cm 2 to 1.33cm 2 at the secondary lamella, and from 0.69cm 2 to 4.19cm 2 at the gill slit. From the relational expression of the mean flow areas and the mean flow velocities, the hydraulic pressures at which the buccal and opercular valves begin to open were estimated: -1.7mmH_2O　or higher for the buccal valve, and 6.6mmH_2O or higher for the opercular valve. Moreover, the hydraulic pressure at which the water begins to flow between the secondary lamellae was assumed to be 4.9mmH_2O or higher.

[ISSN]0370-9361