Evolutionary Feeding Biomechanics

How does our food shape how we look and behave?

freshwater ray gnawing on an insect
freshwater ray gnawing on an insect

Why study feeding?

 

Our food gives us the energy that drives our growth & self-repair. The act of getting that food, foraging, has a considerable effect on our fitness, our net reproductive output - nature's currency upon which selection acts.  How well we catch prey, consume prey, and digest it is our performance - and the higher our performance, the more metabolic energy we can bring to bear growing, maturing, and just generally being alive.  Not only for these important reasons - studying how animals feed is just intrinsically fascinating (at least to me) and who doesn't like food, no?  Given the preoccupation animals have with finding their next meal, the question of how our prey shapes our behaviors and appearance has driven my research program over the last several years.  What materials comprise your food?  How do these materials and structures change how animals approach capturing, processing, and digesting these foods?  

Freshwater ray from Guyana
Freshwater ray from Guyana

Why study piranhas & pacus?

 

The serrasalmids are an interesting group - not a large group, nor a small group of fishes (with just under a hundred described species), although there are dozens of undescribed taxa found throughout South America. Although most people think of piranhas as hypercarnivores - the majority of species in Serrasalmidae consume plant material like seeds, fruits, leaves, and nuts - piscivores are relatively recent on the scene. What is remarkable about these fishes is that they have relatively immobile skulls, relative to other fishes, and yet manage to process an incredible array of prey; prey composed of myriad materials with diverse qualities... How does such a simple system succeed in processing such diverse prey? How does cranial architecture and tooth shape interact to apply forces to prey and resist breakage in return? I am building a phylogenomic tree with Dr. Guillermo Orti at George Washington University to build an evolutionary scaffold with which we will examine feeding evolution across the serrasalmids. This effort will include collaborators from the Smithsonian, Royal Ontario Museum, and the GWU Departments of Biology, Biomimetics, and Engineering - to answer 'how does your food shape how you look and behave.'

Freshwater ray from Guyana
Freshwater ray from Guyana

Why study elasmobranchs?

 

Sharks, skates, rays, & chimaeras (chondrichthyan or cartilaginous fishes) are an amazing group of animals that survived the "test of time."  From their major radiation in the Devonian, cartilaginous fishes have been incredibly successful in the evolutionary game.  Although superficially similar to prehistoric chondrichthyans, modern sharks (neoselachians) are by no means outdated or "primitive."  They are both a window to understanding how and why early fishes were so successful and also a fascinating study system in terms of their unique (in regards to other vertebrates) characteristics, such as their predominantly cartilaginous skeleton, few overall skeletal elements, large size, predatory attributes & behavior, unique morphological & physiological traits (lack of a swim bladder, urea production, serial tooth replacement, the list goes on...).  Understanding evolutionary traits in context is key to understanding how that organism has come to function in its environment, which has direct application to management and ecological interest.

Dasyatis geijskesi - Demerara Estuary 2015
Dasyatis geijskesi - Demerara Estuary 2015

Why study functional morphology?

 

 

Functional morphology, molecular phylogenetics, and biomechanics are all sub-disciplines within biology that can teach us how an organism has adapted or evolved to function within a particular niche or ecosystem - the who, the what, and the when of natural history.  These disciplines provide complementary quantitative means by which scientists can understand how an organism performs a particular task, be it locomotion, feeding, or other behavior - and how augmentation or variation of a particular structure, modulated by behavior - allows that organism to achieve a particular level of fitness in its habitat / niche.  In more general terms, functional morphology allows us to answer (tentatively) how well an organism performs a particular task in relation to other organisms.  This understanding is most frequently applied to evolutionary studies seeking to understand why some groups are more speciose (species rich) than others.