Principal Investigator

Dr. Christopher Marshall

    
   
 
Associate Professor
      
       
Current Members

Lori Timm
Graduate

Graduate
Graduate
.
Former Graduate Members
 
Graduate
Graduate
Graduate
         
.Former Undergraduate Members

Heidi Amin

Jennifer Hill

 Rachel Neuenhoff
Mandi Moss

Undergraduate

Undergraduate

Undergraduate
Undergraduate
  .      
High School Intern
         
 
Descriptions
 
 
Dr. Christopher Marshall: Dr. Christopher Marshall is the PI of the lab. His work focuses on integrating morphology, physiology, and behavioral performance of feeding in marine vertebrates to provide information regarding an organism's foraging ecology, and their conservation. This work includes investigations of natural history and comparative neurobiology of sensory systems of marine vertebrates.
Lori Timm: The specialized behaviors and sensitivity to environmental changes exhibited by sea otters makes them useful as a management-indicator species, and a useful tool in promoting the protection and health of ecosystems. Benthic foraging by sea otters is an important component of their natural history, and substantially influences their environment. However, little is known regarding their feeding adaptations and feeding performance. Therefore, the overall goal of this project is to investigate the feeding capabilities of sea otters to begin to understand the costs of foraging, as well as, the ecological role the sea otter plays in a coastal community. The ecomorphology of feeding in sea otters will be investigated by integrating behavioral and kinematic studies of both wild and captive sea otters, with bite performance testing, measures of jaw muscle physiology, and craniodental morphological analyses of specimens in natural history collections. The specialized behaviors and sensitivity to environmental changes exhibited by sea otters makes them useful as a management-indicator species, and a useful tool in promoting the protection and health of ecosystems. Benthic foraging by sea otters is an important component of their natural history, and substantially influences their environment. However, little is known regarding their feeding adaptations and feeding performance. Therefore, the overall goal of this project is to investigate the feeding capabilities of sea otters to begin to understand the costs of foraging, as well as, the ecological role the sea otter plays in a coastal community. The ecomorphology of feeding in sea otters will be investigated by integrating behavioral and kinematic studies of both wild and captive sea otters, with bite performance testing, measures of jaw muscle physiology, and craniodental morphological analyses of specimens in natural history collections.
Emily Kane: Our knowledge of the diversity and evolution of mammalian feeding is largely limited to terrestrial taxa; in general the biomechanics of marine mammal feeding has been overlooked. The majority of marine mammal feeding studies lack the detailed functional analyses commonly found in comparative feeding investigations of non-mammalian aquatic vertebrates. Other than suckling behavior, suction feeding is rare among terrestrial mammals. In contrast, suction feeding is considered to be a common mode of feeding among marine mammals. However, there are few detailed functional data to support or dispute these claims. The inclusion of marine mammal taxa in biomechanical studies of feeding is important to the larger goal of understanding the diversity and evolution of mammalian feeding. My research will focus on characterizing the kinematics of feeding on of beluga whale, pacific white-sided dolphin, and pilot whale suction feeding, which will add to data from previous studies of odontocete feeding conducted in the Marshall lab. I will also be performing a meta-analysis of both my research and previous research in the lab in order to begin to examine the relationships among taxa in an evolutionary context as well as the ecological implications of the associated feeding strategies. This will involve the integration of both kinematic motion analysis of digitally recorded feeding events and biomechanical analysis of pressure forces produced during the feeding event. In addition, pilot whales have recently been acknowledged as a target recovery species of longline bycatch in the Atlantic ocean. Modification of fishery gear help to reduce marine mammal bycatch, however an understanding of how pilot whales, and other odontocetes, feed is necessary before we can understand what type of modifications would be the best. My project will attempt to address this issue by utilizing pilot whales as one of my study species.
Rachel Neuenhoff: Age determination is an important tool in the study of mammalian populations, particularly populations such as marine mammals that exhibit long life spans and delayed maturity. Demographic models that investigate marine mammal populations require accurate representations of age structure. Surprisingly, few recent demographic data are available for bottlenose dolphin populations from the northern and western Gulf of Mexico. This is despite the fact that Tursiops truncatus is the most common cetacean in the northwest Gulf of Mexico, and the most commonly stranded species in Texas. Rachel will be collecting teeth from stranded bottlenose dolphins along the Texas coast. Teeth will be sectioned and stained for age analyses. The data will then be used to determine (1) population age structure, (2) growth from length-at-age stranding data, (3) mean length-at-birth, and (4) calving season. This work will be compared to a similar data set ranging from ~1980-1990 and will increase our knowledge of the population demographics and natural history of bottlenose dolphins off the coast of Texas over the twenty years.
Brian Bloodworth: Research Interests: Cetaceans demonstrate a diversity of feeding adaptations that allow them to exploit their resources. However, to date, few data on the function of their feeding apparatus are known. My thesis research focuses on the comparative biomechanics of odontocete suction and non-suction feeding mechanisms. To investigate these feeding modes we use pygmy and dwarf sperm whales (kogiids) as models of odontocete suction feeders, and bottlenose dolphins as representatives of non-suction feeding odontocetes. The specific aims of the research are to determine the relative importance of suction versus biting for feeding in odontocetes, and investigate the adaptations of the hyolingual structure for suction feeding. These goals will be accomplished by integrating video footage of controlled feeding trials of both captive kogiids and bottlenose dolphins with biomechanical modeling of their hyolingual apparatus (tongue, hyoid, and associated structures). Kinematic profiles of suction and non-suction feeding odontocetes are compared and contrasted. Dissections of the hyolingual apparatus, vector analysis, measures of cross sectional area and fiber length will allow us to estimate potential maximal force production between presumed suction and non-suction feeding odontocetes. The integration of morphological and behavioral feeding data will provide new information on the function and diversity of odontocete feeding mechanisms and their adaptations to the aquatic environment. (Publication)
Janelle Case: Research interests: In order to understand the nutritional ecology of an organism, it is important to understand its ability to exploit these resources. One way to measure this is through behavioral performance studies of feeding capability. The main component of my research project is to measure the behavioral performances of juvenile red snapper feeding in the laboratory through controlled experimental feeding trials and subsequent analysis of feeding motions (motion analysis). Furthermore, feeding capability can also influence how well a species can compete with a congener or another ecologically similar species, which Janelle will demonstrate by comparing red snapper to other snapper species. The insight gained from these results can also be used towards conservation efforts. The last portion of her project entails a comparison between the feeding capabilities of wild caught versus hatchery raised red snapper which may provide essential information on the future survival of hatchery raised fish in the wild. (Publication)
Alejandra Salazar: Research interests: Recent data reporting the large longline fishery bycatch of loggerhead and leatherback sea turtles is a serious concern for both managers and conservationists. Recent reports that changing the type of hook and bait can reduce sea turtle bycatch is intriguing, but does not address the direct mechanisms of how the hooking phenomenon actually occurs, nor its relationship with hook design and bait. The ability of loggerheads to excel in biting, and their associated feeding biomechanics (i.e., bite force capability, feeding behavior, and jaw-joint mechanics) is likely responsible for their vulnerability to fishery gear and in the hooking phenomenon. Ale will be investigating the behavioral performance and biomechanics of biting in loggerhead turtles at the Galveston NOAA Fisheries sea turtle facility. This one-of-a-kind facility provides an ideal situation to investigate bite biomechanics of loggerhead turtles from many size classes.
Heidi Amin: Heidi Amin was a Texas Institute of Oceanography Undergraduate Fellow in the lab and investigated the sensory biology of bearded seals. She is a co-author with Dr. Marshall on a published article (LINK) regarding bearded seal vibrissae. (Publication)
Jennifer Hill: Jennifer Hill was an undergraduate intern student studying the lateral line system in Atlantic stingrays using retrograde neuroanatomical tracing techniques.  She is currently pursuing her Ph.D. at Georgia Tech.
Mandi Moss:Mandi Moss: Pygmy and dwarf sperm whales (Kogia breviceps and K. sima), or kogiids, comprise the second largest group of stranded cetaceans along the Southeast U.S. coast. Kogiids that strand alive typically do not survive rehabilitation efforts and, historically, have succumbed to gastrointestinal (GI) complications within a month of captivity. Lethal GI complications result from gastric torsion and compaction related to indigestibility of food items outside the normal kogiid diet. Free-ranging kogiids specialize on deep-sea cephalopods, which are not commercially available. Instead, rehabilitators are forced to use common market squid and mackerel for rehabilitating kogiids. It is thought that kogiids possess a derived digestive anatomy and physiology. However, basic data regarding the structure and function of kogiid digestive tracts are unavailable. The objective of my Texas Institute of Oceanography Undergraduate Fellowship to conduct a systematic investigation of the anatomy and physiology of the kogiid GI tract to provide rehabilitation staff with a normal baseline of tract structure and function. This objective will be accomplished by: (1) characterizing the unusual gross anatomy of the kogiid GI tract and (2) characterizing the microanatomical and physiological function of each major GI tract segment using histocytochemical methods.  Mandi is currently pursuing her M.S. at Georgia Southern University..
Zach Leman: Clear Creek High School Intern