1. Shark Olfaction
2. Shark Brain Morphology
3. Ponyfish (Leiognathidae) Light Organs
4. Cranial Endothermy in Opah (Lampris guttatus)
5. Red Muscle in shortfin mako shark (Isurus oxyrinchus) and salmon shark (Lamna ditropis)
6. Coral Complexity
7. Publications and Abstracts

Shark Olfaction

Stephen M. Kajiura
Elasmobranch Research Laboratory at Florida Atlantic University

Tricia Meredith
Elasmobranch Research Laboratory at Florida Atlantic University

Lawrence Frank
University of California, San Diego

Project description:
Sharks possess among the largest olfactory organs of any vertebrate and hammerhead sharks in particular have a greatly expanded olfactory rosette. Their large olfactory organs and acute sensitivity have contributed to their reputation as swimming noses. However, very few studies have actually tested the threshold sensitivity of sharks to odor stimuli. We will employ functional MRI to image the olfactory organs of sharks as they are exposed to a variety of odorants to determine how low a concentration the sharks are actually able to detect. The functional data will be combined with high resolution anatomical data to better understand the form and function of the olfactory organ in the sharks

Shark Brain Morphology

Kara Yopak
University of California, San Diego

Lawrence Frank
University of California, San Diego

Glenn Northcutt
Scripps Institution of Oceanography

Project description:
Chondrichthyans (cartilaginous fishes) occupy a basal position in vertebrate evolution and offer a relatively unexplored opportunity to study the evolution of vertebrate brains. Our study examines the brain morphology of elasmobranchs (sharks, skates, and rays) in relation to both phylogeny and ecology. There is significant variation in both brain size and complexity across cartilaginous fish species. Using MRI, we will assess relative brain size and the relative size of five major brain areas (telencephalon, diencephalon, mesencephalon, cerebellum, and medulla) in a range of chondrichthyan species. This project aims to work with other members of the DFL project to contribute to the master specimen digital database.

Ponyfish (Leiognathidae) Light Organs

John Sparks
American Museum of Natural History

Prosanta Chakrabarty
American Museum of Natural History

Lawrence Frank
University of California, San Diego

Project description:
We are interested in studying Leiognathidae (ponyfish) because they provide an extraordinary and unmatched biological system that combines dramatic sexual dimorphism and photic signaling. The light organ system in these fishes differs greatly between species and sexes, but is seldom studied and not very well understood. As our group works out phylogenetic relationships between these fishes, we will be able to better understand how this light organ system evolved. Part of understanding the relationships requires collecting new material from the different parts of the world these species are found. While collecting, we found that many species were undescribed and most of the taxonomy was incorrect. Unfortunately, much of the original material used to describe these species (type specimens) is lost or in poor condition. With MRI we are able to find important characters in this rare material that would otherwise be concealed to us. We can see more structural detail than would be possible through dissection, and we can view the entire system in situ. This significantly improves our ability to identify ponyfish clades and helps us better understand the evolution of the light organ system.

Cranial Endothermy in Opah (Lampris guttatus)

Kathryn Dickson
California State University Fullerton

Rosa Runcie
California State University Fullerton

Donald Hawn
National Marine Fisheries Service, Pacific Islands Fisheries Science Center, Honolulu, Hawaii

Heidi Dewar
National Marine Fisheries Service, Southwest Fisheries Science Center, La Jolla, CA

Lawrence Frank
University of California San Diego

Project Description :
Cranial endothermy is the ability of certain fishes to maintain the temperature of the cranial region (eye and brain) at a temperature significantly higher than the surrounding water temperature. Cranial endothermy has evolved by convergence in billfishes, the butterfly mackerel, tunas, and lamnid sharks. The purpose of this project is to document cranial endothermy in another teleost fish species, the opah or moonfish (Lampris guttatus). Like all other cranial endotherms, this species experiences rapid changes in seawater temperature as it moves vertically within the water column. MRI allows us to visualize the three-dimensional arrangement of the heat source and the heat retention mechanisms required for cranial endothermy in L. guttatus. This study will contribute to understanding the evolution of endothermy in fishes and the physiological ecology of this unique fish.

Methods:
T1-weighted 3D spoiled gradient recalled echo acquisition with image and segmentation analyses

Red Muscle in shortfin mako shark (Isurus oxyrinchus) and salmon shark (Lamna ditropis)

Investigators:
Cameron Perry, Daniel Cartamil, Diego Bernal, Chugey A. Sepulveda, Rebecca J. Theilmann, Jeffrey Graham, Lawrence R. Frank - University of California, San Diego

Project Description:
To differentiate muscle fiber types and quantify the amounts of slow, red aerobic muscle in the shortfin mako shark (Isurus oxyrinchus) and the salmon shark (Lamna ditropis)

Methods:
T1-weighted 3D spoiled gradient recalled echo acquisition with image and segmentation analyses.

Coral Complexity

David Zawada
US Geological Survey

Forest Rohwer
San Diego State University

Lawrence Frank
University of California, San Diego

Project description:
We are interested in how topographic complexity contributes to the biodiversity and habitat complexity of benthic communities, especially coral reefs. Coral reefs represent one of the roughest structures in the marine environment. This roughness is a significant component of the high degree of habitat complexity associated with reefs. Various studies have investigated reef rugosity at discrete spatial scales, ranging from kilometers down to millimeters. However, to date, few studies have addressed fine-scale roughness (<1 cm). MR images allow us to construct high-resolution 3D surface models of individual corals, which we use to estimate their roughness on spatial scales from 200 um to 1 cm in terms of fractal dimension.

Click to watch these animations of rendered coral MR data
(Quicktime format)

Publications and Abstracts

Interactive 3D Graphics for Web-based Data Analysis and Visualization for the Digital Fish Librray (DFL)
G Eichberger, CN Perry, HJ Walker, P Hastings, L Linsen, LR Frank
in 33rd International Conference and Exhibition on Computer Graphics and Interactive Techniques
Boston, MA
30 July - 3 August, 2006

May L, Frank LR, "An 8 Channel Geometry Optimized RF Coil Array for Imaging of Fish at 3T" , bibl. , (). Abstract Accepted ISMRM-ESMRMB Joint Annual Meeting, May 2007, Berlin, Germany

Perry CN, Cartamil DC, Bernal D, Sepulveda CA, Theilmann RJ, Graham JB, Frank LR, "Quantification of Red Myotomal Muscle Volume and Geometry in the Shortfin Mako Shark (Isurus oxyrinchus) and the Salmon Shark (Lamna ditropis), Using T1-Weighted Magnetic Resonance Imaging.", Journal of Morphology, 2007 . Accepted

Sepulveda CA, Dickson KA, Frank LR, Graham JB, "Cranial endothermy and a putative brain heater in the most basal tuna species, Allothunnus fallai.", Journal of Fish Biology, 2007 . Accepted