Some aspects of buoyancy adaptations of chaetognaths
© Biologische Anstalt Helgoland 1991
Chaetognaths mainly keep to a preferred depth range by movement and resistance achieved by body shape. Some species, for exampleSagitta lyra andS. hexaptera, developed conspicuous, voluminous, gelatinous inner parts in the lateral fins. These are considered an aid toward buoyancy, as they compensate the increasing density caused by maturing gonads. Probably, the small size of the sexual organs ofS. enflata can also be regarded as a buoyancy adaptation.