Image: X-ray of leatherjacket spine
An x-ray image of a the dorsal spine of a leatherjacket from the Australian Museum Ichthyology Collection.
- James King
- © Australian Museum
Many of the triggerfishes (Family Balistidae) and leatherjackets (Family Monacanthidae) have a first dorsal fin spine that can be locked into an erect position.
This is made possible by a ball and socket "trigger-like" mechanism. The base of the second spine slots into a groove in the first spine. The locking mechanism is released when the second spine is depressed.