Image: Mouth of a Sevenspot Archerfish
The mouth of a Sevenspot Archerfish, Toxotes chatareus. Note the groove along the roof of the mouth and the shape of the tongue.
- Mark McGrouther
- © Australian Museum
Archerfishes have adaptations to the mouth which enable them to accurately spit a jet of water to knock insects out of overhanging branches. A deep groove runs along the roof of the mouth. A ridge along the top of the tongue fits into this groove. When an Archerfish shoots a jet of water, it raises its tongue against the roof of the mouth forming a tube. The gill covers are then quickly closed, which forces water along the tube. The tip of the tongue acts as a valve.
The fish was collected in the McKinlay River near Mount Douglas, Northern Territory. It is registered in the Australian Museum Ichthyology Collection (I.20453-005).