All organisms need to consume food to survive and some of the most fascinating behavioral innovations have evolved for organisms to do just that-feed. We have a special interest in studying the mechanisms guiding feeding diversification in vertebrate clades. Therefore, we tend to always have a wide range of projects that consider feeding transitions in vertebrates. Feeding transitions are a broad topic and can involve how animals find food, prey capture behaviors, and dietary changes. All of these projects have involved our team taking a closer look at morphology and behavior. Examining feeding transitions through a comparative evolutionary lens allows us to better understand where and when transitions evolve.
Pharyngeal Jaw Innovation
Raptorial jaws help moray eels swallow large prey.
Moray eels are large predatory fish that are found on coral reefs world-wide and yet little is known about their feeding mechanics. In studies published in 2007 & 2008 I describe a novel prey transport mechanism in moray eels (pharyngeal transport, Fig. 1). My study revealed that morays have a reduced capacity to suction feed and apprehend their prey by biting. When the prey item is apprehended in their oral jaws, morays protract a pair of pharyngeal jaws, located behind the head, into their oral cavity. Once in the oral cavity, the pharyngeal jaws bite down on the prey item and transport the prey into the esophagus.
The moray transport mechanism is the first alternative prey transport mechanism to suction reported in an aquatic vertebrate and the first example of a vertebrate using a second set of jaws to grasp and transport prey from the oral jaws into the esophagus. The transport behavior of morays is also convergent with the prey transport mechanism used by snakes. Similar to snakes, moray eels are large elongate limbless predators that have evolved a strategy for ratcheting down large prey. However, rather than ratchet from side to side using independent movement of the left and right jaws like a snake, morays ratchet from front to back using independent movement of two separate jaw systems.
You can read about this in the NewYorkTimes.
Since these papers, I have documented the biomechanical diversity of the oral jaws of various moray species. The majority of morays swallow large prey whole, although some morays process their prey in their oral jaws before ingesting them. One might imagine that swallowing large prey whole requires specialized adaptations of the digestive tract. My present goals are to understand the digestive physiology of consuming large prey whole versus consuming chunks of prey, two strategies seen in the feeding ecology of morays.
Morphological and Functional Innovation: Raptorial jaws help moray eels swallow large prey
Moray eels are large predatory fish that are found on coral reefs world-wide and yet little is known about their feeding mechanics. In studies published in 2007 & 2008 I describe a novel prey transport mechanism in moray eels (pharyngeal transport, Fig. 1). My study revealed that morays have a reduced capacity to suction feed and apprehend their prey by biting. When the prey item is apprehended in their oral jaws, morays protract a pair of pharyngeal jaws, located behind the head, into their oral cavity. Once in the oral cavity, the pharyngeal jaws bite down on the prey item and transport the prey into the esophagus.
The moray transport mechanism is the first alternative prey transport mechanism to suction reported in an aquatic vertebrate and the first example of a vertebrate using a second set of jaws to grasp and transport prey from the oral jaws into the esophagus. The transport behavior of morays is also convergent with the prey transport mechanism used by snakes. Similar to snakes, moray eels are large elongate limbless predators that have evolved a strategy for ratcheting down large prey. However, rather than ratchet from side to side using independent movement of the left and right jaws like a snake, morays ratchet from front to back using independent movement of two separate jaw systems.
Since these papers, I have documented the biomechanical diversity of the oral jaws of various moray species. The majority of morays swallow large prey whole, although some morays process their prey in their oral jaws before ingesting them. One might imagine that swallowing large prey whole requires specialized adaptations of the digestive tract. My present goals are to understand the digestive physiology of consuming large prey whole versus consuming chunks of prey, two strategies seen in the feeding ecology of morays.
Current Research
The teleost skull is one of the most heavily studied functional units among vertebrates and has been used as a model for numerous biomechanical studies, however, the majority of these studies focus on suction feeding. Although suction feeding is considered the most commonly used prey capture mechanism across aquatic vertebrates, biting as a prey acquisition strategy has evolved independently in several teleost clades. The evolution of biting appears to have had an effect on the transport and respiratory complex for some of these biting taxa. For example, during my postdoctoral research, I discovered that moray eels, a species rich clade of anguilliform fishes, do not rely on suction to feed, but apprehend their prey by biting. In addition to biting their prey, I found that morays have evolved an alternative method of transporting their prey (see Recent Research section). This functional innovation in moray transport behavior provides an opportunity to examine how functional innovations in integrated systems arise. I hypothesize that the evolution of biting has had downstream effects on different modules comprising the cranio-musculoskeletal system of teleosts.
My current research, funded by the National Science Foundation (IOS -0819009), investigates trait correlation in the teleost skull. In this body of work I examine three distinct modules, or developmental complexes, of the teleost skull: the oral jaws, the hyobranchial system, and the opercular series (Fig. 2) in anguilliform fishes. I am specifically interested in documenting how changes in the oral jaws (i.e. extreme elongation as seen in many biting taxa) affects the hyobranchial and opercular system which may result in functional specialization and novel prey transport and respiratory modes, as observed in morays.
