Hidden jaws

Picture

Cichlid cranial image. Photo from journal article – GJ Fraser, CD Hulsey, RF Bloomquist, K Uyesugi, NR Manley, JT Streelman, “An ancient gene network is co-opted for teeth on old and new jaws,” PLoS Biology 7(2), Feb. 10, 2009.

How intently do you watch your cichlids when they eat? If you pay close attention when they eat anything more substantive than flakes (e.g., pellets, discs), you’ve probably noticed the food completely disappear but see little movement in the oral jaws. Why?

One of the defining morphological characteristics of the family cichlidae is the existence of pharyngeal dentition. Huh?

Cichlids have teeth in their throat. That’s right. In addition to whatever oral teeth they may have, all cichlids possess tiny teeth on the pharyngeal plate in the throat that are used to grind up food. This pharyngeal jaw action, often unnoticed to the naked eye, breaks down food for passage through the esophagus into the gut.

Interestingly enough, these teeth aren’t only used for processing food. They’re also used to produce sounds for communication purposes. In fact, if you’ve ever kept clown loaches (Chromobotia macracanthus) and heard the clicking sound they make, you’re hearing the pharyngeal teeth grinding together.

Watch your cichlids closely when they eat and you might just see the pharyngeal jaw muscles at work.

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