Researchers at Louisiana State University (LSU) have proposed that the rockhead poacher fish utilizes a unique bowl-shaped indentation in its head to produce buzzing sounds for communication. This feature is considered unusual among vertebrates.
Daniel Geldof, an LSU researcher, described the rockhead poacher's head as appearing to have a portion of its skull missing. This distinct characteristic has drawn scientific interest, with theories suggesting its purpose could involve camouflage, sensory functions, or sound production.
The fish inhabit shallow, rocky intertidal zones from California to Alaska and are adept at concealment, making specimen collection challenging. Researchers sometimes locate them in places like Deadman Bay, Washington, during low tide.
Geldof employed a microCT scanner to create a detailed 3D model of the fish's head cavity. The model revealed numerous tiny structures within the pit, including rods on the rear face and small bone spines pointing inward. These findings led Geldof to hypothesize that the spines function as water motion sensors.
Further observations indicated that rockhead poachers emit a vibrating sensation when handled underwater. Scans showed that the fish's first set of ribs are significantly enlarged and positioned against the bony dish at the base of the cranial pit. Researchers suggest that powerful muscles enable the fish to vibrate these ribs against the skull's dip, effectively creating a 'percussion instrument' within its head.
This sound production method is believed to be crucial for communication in their noisy tidal habitats, where the sounds of crashing waves make it difficult for small fish to be heard and for sound to be localized underwater.
Future research aims to explore further questions, such as the effect of the head cavity not being filled with water. The insights gained from studying the rockhead poacher could contribute to understanding effective underwater sound production and transmission.