ABSTRACT
It has been reported that fish may match the extent of their respiration to their need for gaseous exchange by failing to ventilate certain gills. One third of the respiratory movements of the lamprey (Lampetra fluviatilis), when in oxygenated tap water, consist of contractions of the anterior two or three branchial chambers only. In partially deoxygenated water the anterior five and finally all of the branchial chambers become active (Wikgren, 1953). In Raja batis water is taken in through the spiracles during rest and perfuses only the anterior four gill pouches. When swimming, water enters through the mouth as well and perfuses the posterior gills (Darbishire, 1907). The dogfish Scyliorhinus canicula has a similar division of the spiracular and buccal inflows between the anterior and posterior gills (Hughes, 1960). In the eel, van Dam (1938) reports that during rest only the gills of one side may be ventilated.
