The Evolution of Cranial Forms in Anguilliform Fishes: Does Extreme Biting Promote or Constrain Morphological Diversity?

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The diversification of novel body forms and behavior patterns is of central interest in biology. One factor that may guide or constrain diversity in organismal design is the correlation of traits: individual trait diversity may be limited by their associations with other traits. Alternatively, a large change in one character or in a suite of functionally related traits may have far-reaching consequences on the integration of complex systems, greatly affecting the outcome of system design and behavior. Fish skulls are highly complex musculoskeletal systems that are used for critical survival behaviors such as prey capture, prey transport (swallowing), and respiration. Our knowledge of skull design in teleost fishes is derived almost entirely from studies of suction feeding, the dominant mode of prey capture, prey transport, and respiration for the majority of fishes. However, biting is an alternative prey capture behavior that has evolved across many fish groups and the evolutionary dynamics of morphological and behavioral evolution in biting lineages is poorly understood. This study will test the idea that the evolution of biting has promoted diversification in behavior and morphology in one of the most prominent groups of biting fishes: eels and their allies. Fishes that bite their prey rather than use suction, have modified their jaws in diverse ways. In some cases, jaw modification has had cascading effects on the transport and respiratory complex for some of these fish species that capture their prey by biting. For example, moray eels, a species rich group belonging to a larger group of fishes known as the anguilliforms, or true eels, do not rely on suction for capturing or swallowing their prey. Morays capture their prey by sinking their teeth into them. Once the prey is captured, morays protract their pharyngeal jaws, a second set of jaws in their throat, into their mouths to grab the prey item and transport the prey into their esophagus. This swallowing behavior is unlike any other fish transport behavior and presents the first alternative method for transporting prey without the use of suction in the aquatic environment. This novelty in moray transport behavior provides an opportunity to examine how functional innovations in integrated systems arise. This study will be the first comparative analysis on the functional implications of biting on teleost skull diversity. This work will also improve our understanding of eel relationships and will integrate fossil information with newly collected genetic data to produce the first time tree for the group. With this tree we propose to identify broad patterns of trait associations and trait modularity in the skull of eels to illustrate how a change in the oral jaws has had cascading effects on systems used for prey transport, and respiration. The principal investigator is a first time investigator who is committed to recruiting and encouraging young scientists, especially women. The collective efforts of this grant will provide training for graduate students and undergraduates in a variety of anatomical techniques, while also providing opportunities for these developing scientists to attend scientific meetings.