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Title: The coelacanth rostral organ is a unique low-resolution electro-detector that facilitates the feeding strike.
Creator: Berquist, Rachel M., Galinsky, Vitaly L., Kajiura, Stephen M., Frank, Lawrence R.
Abstract/Description: The cartilaginous and non-neopterygian bony fishes have an electric sense typically comprised of hundreds or thousands of sensory canals distributed in broad clusters over the head. This morphology facilitates neural encoding of local electric field intensity, orientation, and polarity, used for determining the position of nearby prey. The coelacanth rostral organ electric sense, however, is unique in having only three paired sensory canals with distribution restricted to the dorsal snout,...
Show moreThe cartilaginous and non-neopterygian bony fishes have an electric sense typically comprised of hundreds or thousands of sensory canals distributed in broad clusters over the head. This morphology facilitates neural encoding of local electric field intensity, orientation, and polarity, used for determining the position of nearby prey. The coelacanth rostral organ electric sense, however, is unique in having only three paired sensory canals with distribution restricted to the dorsal snout, raising questions about its function. To address this, we employed magnetic resonance imaging methods to map electrosensory canal morphology in the extant coelacanth, Latimeria chalumnae, and a simple dipole ‘rabbit ears’ antennae model with toroidal gain function to approximate their directional sensitivity. This identified a unique focal region of electrosensitivity directly in front of the mouth, and is the first evidence of a low-resolution electro-detector that solely facilitates prey ingestion.
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Date Issued: 2015-08-11
PURL: http://purl.flvc.org/fau/fd/FAUIR000024
Format: Citation

Title: Quantification of Massive Seasonal Aggregations of Blacktip Sharks (Carcharhinus limbatus) in Southeast Florida.
Creator: Kajiura, Stephen M., Tellman, Shari L.
Abstract/Description: Southeast Florida witnesses an enormous seasonal influx of upper trophic level marine predators each year as massive aggregations of migrating blacktip sharks (Carcharhinus limbatus) overwinter in nearshore waters. The narrow shelf and close proximity of the Gulf Stream current to the Palm Beach County shoreline drive tens of thousands of sharks to the shallow, coastal environment. This natural bottleneck provides a unique opportunity to estimate relative abundance. Over a four year period...
Show moreSoutheast Florida witnesses an enormous seasonal influx of upper trophic level marine predators each year as massive aggregations of migrating blacktip sharks (Carcharhinus limbatus) overwinter in nearshore waters. The narrow shelf and close proximity of the Gulf Stream current to the Palm Beach County shoreline drive tens of thousands of sharks to the shallow, coastal environment. This natural bottleneck provides a unique opportunity to estimate relative abundance. Over a four year period from 2011–2014, an aerial survey was flown approximately biweekly along the length of Palm Beach County. A high definition video camera and digital still camera mounted out of the airplane window provided a continuous record of the belt transect which extended 200 m seaward from the shoreline between Boca Raton Inlet and Jupiter Inlet. The number of sharks within the survey transect was directly counted from the video. Shark abundance peaked in the winter (January-March) with a maximum in 2011 of 12,128 individuals counted within the 75.6 km-2 belt transect. This resulted in a maximum density of 803.2 sharks km-2. By the late spring (April-May), shark abundance had sharply declined to 1.1% of its peak, where it remained until spiking again in January of the following year. Shark abundance was inversely correlated with water temperature and large numbers of sharks were found only when water temperatures were less than 25°C. Shark abundance was also correlated with day of the year but not with barometric pressure. Although shark abundance was not correlated with photoperiod, the departure of the sharks from southeast Florida occurred around the vernal equinox. The shark migration along the United States eastern seaboard corresponds spatially and temporally with the spawning aggregations of various baitfish species. These baseline abundance data can be compared to future studies to determine if shark population size is changing and if sharks are restricting their southward migration as global water temperatures increase.
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Date Issued: 2016-03-30
PURL: http://purl.flvc.org/fau/fd/FAUIR000074
Format: Citation

Title: Temporal resolution and spectral sensitivity of the visual system of three coastal shark speciesfrom different light environments.
Creator: McComb, Dawn Michelle, Frank, Tamara M., Hueter, R. E., Kajiura, Stephen M., Harbor Branch Oceanographic Institute
Date Issued: 2010
PURL: http://purl.flvc.org/fau/fd/FA00007091
Subject Headings: Sharks, Visual system, Spectral sensitivity, Night Vision
Format: Document (PDF)

Title: Electric Field Detection in Sawfish and Shovelnose Rays.
Creator: Wueringer, Barbara E., Squire, Lyle, Jr., Kajiura, Stephen M., Tibbetts, Ian R., Hart, Nathan S., Collin, Shaun P., Laudet, Vincent
Abstract/Description: In the aquatic environment, living organisms emit weak dipole electric fields, which spread in the surrounding water. Elasmobranchs detect these dipole electric fields with their highly sensitive electroreceptors, the ampullae of Lorenzini. Freshwater sawfish, Pristis microdon, and two species of shovelnose rays, Glaucostegus typus and Aptychotrema rostrata were tested for their reactions towards weak artificial electric dipole fields. The comparison of sawfishes and shovelnose rays sheds...
Show moreIn the aquatic environment, living organisms emit weak dipole electric fields, which spread in the surrounding water. Elasmobranchs detect these dipole electric fields with their highly sensitive electroreceptors, the ampullae of Lorenzini. Freshwater sawfish, Pristis microdon, and two species of shovelnose rays, Glaucostegus typus and Aptychotrema rostrata were tested for their reactions towards weak artificial electric dipole fields. The comparison of sawfishes and shovelnose rays sheds light on the evolution and function of the elongated rostrum (‘saw’) of sawfish, as both groups evolved from a shovelnose ray-like ancestor. Electric stimuli were presented both on the substrate (to mimic benthic prey) and suspended in the water column (to mimic free-swimming prey). Analysis of around 480 behavioural sequences shows that all three species are highly sensitive towards weak electric dipole fields, and initiate behavioural responses at median field strengths between 5.15 and 79.6 nVcm^-1. The response behaviours used by sawfish and shovelnose rays depended on the location of the dipoles. The elongation of the sawfish’s rostrum clearly expanded their electroreceptive search area into the water column and enables them to target free-swimming prey.
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Date Issued: 2012-07-25
PURL: http://purl.flvc.org/fau/fd/FAUIR000073
Format: Citation

Title: A content analysis of 32 years of Shark Week documentaries.
Creator: Lisa B. Whitenack, Brady L. Mickley, Julia Saltzman, Stephen M. Kajiura, Catherine C. Macdonald, David S. Shiffman
Abstract/Description: Despite evidence of their importance to marine ecosystems, at least 32% of all chondrichthyan species are estimated or assessed as threatened with extinction. In addition to the logistical difficulties of effectively conserving wide-ranging marine species, shark conservation is believed to have been hindered in the past by public perceptions of sharks as dangerous to humans. Shark Week is a high-profile, international programming event that has potentially enormous influence on public...
Show moreDespite evidence of their importance to marine ecosystems, at least 32% of all chondrichthyan species are estimated or assessed as threatened with extinction. In addition to the logistical difficulties of effectively conserving wide-ranging marine species, shark conservation is believed to have been hindered in the past by public perceptions of sharks as dangerous to humans. Shark Week is a high-profile, international programming event that has potentially enormous influence on public perceptions of sharks, shark research, shark researchers, and shark conservation. However, Shark Week has received regular criticism for poor factual accuracy, fearmongering, bias, and inaccurate representations of science and scientists. This research analyzes the content and titles of Shark Week episodes across its entire 32 years of programming to determine if there are trends in species covered, research techniques featured, expert identity, conservation messaging, type of programming, and portrayal of sharks. We analyzed titles from 272 episodes (100%) of Shark Week programming and the content of all available (201; 73.9%) episodes. Our data demonstrate that the majority of episodes are not focused on shark bites, although such shows are common and many Shark Week programs frame sharks around fear, risk, and adrenaline. While criticisms of disproportionate attention to particular charismatic species (e.g. great whites, bull sharks, and tiger sharks) are accurate and supported by data, 79 shark species have been featured briefly at least once. Shark Week’s depictions of research and of experts are biased towards a small set of (typically visual and expensive) research methodologies and (mostly white, mostly male) experts, including presentation of many white male non-scientists as scientific experts. While sharks are more often portrayed negatively than positively, limited conservation messaging does appear in 53% of episodes analyzed. Results suggest that as a whole, while Shark Week is likely contributing to the collective public perception of sharks as bad, even relatively small alterations to programming decisions could substantially improve the presentation of sharks and shark science and conservation issues.
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Date Issued: 2022
PURL: http://purl.flvc.org/fau/fd/FAUIR000533
Format: Document (PDF)

Title: Sexual and Ontogenetic Dimorphisms in the Anterior Lateral Line Nerve of the Yellow Singray, Urobatis jamaicensis.
Creator: Kramer, Katie, Newton, Kyle C., Kajiura, Stephen M., Office of Undergraduate Research and Inquiry
Abstract/Description: To fully understand the function of the elasmobranch electrosensory system it is necessary to examine electrosensory nerves extending from the ampullae of Lorenzini to the central nervous system. Studies detailing the composition of sensory axons are rare, but they have shown that ontogenetic and sexual dimorphism exists in the anterior lateral line nerve (ALLN) of numerous species. This study obtained a count of the number of axons comprising the ALLN in male vs. female and adult vs....
Show moreTo fully understand the function of the elasmobranch electrosensory system it is necessary to examine electrosensory nerves extending from the ampullae of Lorenzini to the central nervous system. Studies detailing the composition of sensory axons are rare, but they have shown that ontogenetic and sexual dimorphism exists in the anterior lateral line nerve (ALLN) of numerous species. This study obtained a count of the number of axons comprising the ALLN in male vs. female and adult vs. juvenile yellow stingrays (Urobatis jamaicensis). We hypothesized that males have more axons than females, and that the number of axons is ontogenetically constant. We expect males to have 30% more axons in their ALLN, and that the number of axons is ontogenetically constant for both sexes. This study will provide unique data about the electrosensory nerves of Yellow stingrays that can be used in future studies to make comparisons between other species.
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Date Issued: 2017
PURL: http://purl.flvc.org/fau/fd/FA00005624
Subject Headings: College students --Research --United States.
Format: Document (PDF)

Title: Ecomorphology of Shark Electroreceptors.
Creator: Cornett, Anthony D., Kajiura, Stephen M., Florida Atlantic University
Abstract/Description: Sharks possess an electrosensory system which allows the detection of electric fields . How this system varies among related taxa and among species inhabiting different environments remains unexplored. Electroreceptor number was quantified for representative species of related taxa (genera, families, orders) from different environments (pelagic, coastal, deepwater) and taxa from similar environments to determine potential phylogenetic constraint or evolutionary convergence. Coastal open water...
Show moreSharks possess an electrosensory system which allows the detection of electric fields . How this system varies among related taxa and among species inhabiting different environments remains unexplored. Electroreceptor number was quantified for representative species of related taxa (genera, families, orders) from different environments (pelagic, coastal, deepwater) and taxa from similar environments to determine potential phylogenetic constraint or evolutionary convergence. Coastal open water sharks possess the greatest number of electroreceptors; deepwater sharks the least. Pelagic and coastal benthic sharks retain comparable electrosensory pore numbers despite inhabiting vastly different environments. Electrosensory pores were primarily located in ventral distributions, except among coastal open water sharks which possess roughly even distributions around the head. Among related species and genera, pore numbers and distribution are comparable, with greater variation among higher taxa. Results implicate evolutionary convergence as the primary influence in electroreceptor development, while phylogenetic constraint establishes similar base values for number and distribution.
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Date Issued: 2006
PURL: http://purl.flvc.org/fau/fd/FA00000737
Subject Headings: Sharks--Ecology, Sharks--Morphology, Echolocation (Physiology), Aquatic animals--Physiology, Senses and sensation, Adaptation (Biology)
Format: Document (PDF)

Title: Cognitive and magnetosensory ecology of the yellow stingray, Urobatis jamaicensis.
Creator: Newton, Kyle C., Kajiura, Stephen M., Florida Atlantic University, Charles E. Schmidt College of Science, Department of Biological Sciences
Abstract/Description: Elasmobranchs (sharks, skates, and rays) migrate across a wide range of spatiotemporal scales, display philopatry, seasonal residency, and maintain home ranges. Many animals use the Earth’s magnetic field to orient and navigate between habitats. The geomagnetic field provides a variety of sensory cues to magnetically sensitive species, which could potentially use the polarity, or intensity and inclination angle of the field, to derive a sense of direction, or location, during migration....
Show moreElasmobranchs (sharks, skates, and rays) migrate across a wide range of spatiotemporal scales, display philopatry, seasonal residency, and maintain home ranges. Many animals use the Earth’s magnetic field to orient and navigate between habitats. The geomagnetic field provides a variety of sensory cues to magnetically sensitive species, which could potentially use the polarity, or intensity and inclination angle of the field, to derive a sense of direction, or location, during migration. Magnetoreception has never been unequivocally demonstrated in any elasmobranch species and the cognitive abilities of these fishes are poorly studied. This project used behavioral conditioning assays that paired magnetic and reinforcement stimuli in order to elicit behavioral responses. The specific goals were to determine if the yellow stingray, Urobatis jamaicensis, could detect magnetic fields, to quantify the nature of the magnetic stimuli it could detect, and to quantify the learning and memory capabilities of this species. The results supported the original hypotheses and demonstrated that the yellow stingray could: discriminate between magnetic and non-magnetic objects; detect and discriminate between changes in geomagnetic field strength and inclination angle; and use geomagnetic field polarity to solve a navigational task. The yellow stingray learned behavioral tasks faster and retained the memories of learned associations longer than any batoid (skate or ray) to date. The data also suggest that this species can classify magnetic field stimuli into categories and learn similar behavioral tasks with increased efficiency, which indicate behavioral flexibility. These data support the idea that cartilaginous fishes use the geomagnetic field as an environmental cue to derive a sense of location and direction during migrations. Future studies should investigate the mechanism, physiological threshold, and sensitivity range of the elasmobranch magnetic sense in order to understand the effects of anthropogenic activities and environmental change on the migratory ability of these fishes.
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Date Issued: 2017
PURL: http://purl.flvc.org/fau/fd/FA00004883, http://purl.flvc.org/fau/fd/FA00004883
Subject Headings: Animal behavior., Animal migration., Magnetic fields--Physiological effect., Senses and sensation., Adaptation (Biology)
Format: Document (PDF)

Title: Effect of Deepwater Horizon Crude Oil on Olfaction and Electroreception in the Atlantic Stingray, Dasyatis sabina.
Creator: Cave, Eloise, Kajiura, Stephen M., Florida Atlantic University, Charles E. Schmidt College of Science, Department of Biological Sciences
Abstract/Description: Crude oil causes both lethal and sublethal effects on marine organisms, but the impact upon sensory function remains unexplored. Elasmobranchs rely upon the effective functioning of their sensory systems for use in feeding, mating, and predator avoidance. The objective of this study was to test the effect of crude oil upon the olfactory and electroreceptive sensitivity of the Atlantic stingray, Dasyatis sabina. The magnitudes of the electro-olfactogram (EOG) responses were significantly...
Show moreCrude oil causes both lethal and sublethal effects on marine organisms, but the impact upon sensory function remains unexplored. Elasmobranchs rely upon the effective functioning of their sensory systems for use in feeding, mating, and predator avoidance. The objective of this study was to test the effect of crude oil upon the olfactory and electroreceptive sensitivity of the Atlantic stingray, Dasyatis sabina. The magnitudes of the electro-olfactogram (EOG) responses were significantly depressed by 26% (Glutamic Acid) to 157% (Cysteine) for all amino acids when stingrays were exposed to crude oil. The shapes of the EOG responses when exposed to oil were also significantly different, exhibiting a more protracted response compared to un-exposed stingrays. Oil exposed stingrays exhibited a significant decrease in orientation distance to prey-simulating electric fields. This study is the first to quantify the effects of crude oil on olfactory and electrosensory sensitivity of marine predators.
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Date Issued: 2016
PURL: http://purl.flvc.org/fau/fd/FA00004776, http://purl.flvc.org/fau/fd/FA00004776
Subject Headings: BP Deepwater Horizon Explosion and Oil Spill, 2010., Stingrays--Physiology., Deep-sea biology., Adaptation (Biology), Electroreceptors., Oil spills--Environmental aspects., Olfactometry.
Format: Document (PDF)

Title: Electroreception in the Euryhaline Stingray, Dasyatis sabina.
Creator: McGowan, David W., Kajiura, Stephen M., Florida Atlantic University, Department of Biological Sciences, Charles E. Schmidt College of Science
Abstract/Description: This study determined the electrosensitivity of a euryhaline elasmobranch, the Atlantic stingray, Dasyatis sabina, throughout the range of salinities that it would naturally encounter. It quantified the behavioral response of the stingrays to prey-simulating electric stimuli in freshwater, brackish, and full strength seawater. The electroreceptive capability of stingrays from a permanent freshwater population in the St. Johns River system was also compared with stingrays that inhabit the...
Show moreThis study determined the electrosensitivity of a euryhaline elasmobranch, the Atlantic stingray, Dasyatis sabina, throughout the range of salinities that it would naturally encounter. It quantified the behavioral response of the stingrays to prey-simulating electric stimuli in freshwater, brackish, and full strength seawater. The electroreceptive capability of stingrays from a permanent freshwater population in the St. Johns River system was also compared with stingrays that inhabit the tidally-dynamic Indian River Lagoon in east Florida. This study demonstrated that D. sabina can detect prey-simulating electric fields in freshwater, but the function of its electrosensory system is significantly reduced. The SJR stingrays did not demonstrate an enhanced electrosensitivity in freshwater, nor did they have reduced sensitivity when introduced to higher salinities. The reduction in electrosensitivity and detection range in freshwater is attributed to both an environmental factor (electrical resistivity of the water) and the physiological limitations of the ampullary canals.
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Date Issued: 2008
PURL: http://purl.flvc.org/fau/fd/FA00000797
Subject Headings: Stingrays
Format: Document (PDF)

Title: MIGRATORY PATTERNS AND SEXUAL SEGREGATION IN THE BLACKTIP SHARK, CARCHARHINUS LIMBATUS, OFF THE UNITED STATES EAST COAST.
Creator: Bowers, Mary Elizabeth, Kajiura, Stephen M., Florida Atlantic University, Department of Biological Sciences, Charles E. Schmidt College of Science
Abstract/Description: Many marine species distributions have shifted poleward in response to global climate change. Many environmental characteristics will be affected by climate change including temperature and phytoplankton concentration; yet, photoperiod will remain the same. It is imperative to gather baseline distribution data on migratory species so that these shifts can be measured and mitigated. Sex-specific differences in reproductive strategies cause sexual segregation, sex-specific differences in...
Show moreMany marine species distributions have shifted poleward in response to global climate change. Many environmental characteristics will be affected by climate change including temperature and phytoplankton concentration; yet, photoperiod will remain the same. It is imperative to gather baseline distribution data on migratory species so that these shifts can be measured and mitigated. Sex-specific differences in reproductive strategies cause sexual segregation, sex-specific differences in spatial distribution. Female blacktip sharks exhibit a synchronous, biennial reproductive cycle in which one year of reproduction is followed by a resting year. Acoustic telemetry can be used in conjunction with collaborative networks to track migratory species over great distances. However, the irregular spacing of acoustic receivers often results in sporadic detection data, which can lead to skewed distribution information. This project developed and tested an analysis process to regularize sporadic acoustic detection data. Those regularized data were then applied to cluster analyses to determine the seasonal spatial distributions of blacktip sharks, Carcharhinus limbatus, off the United States East Coast and corresponding environmental correlates of latitudinal movement. Sexes of this population were investigated separately and in combination. Differences in distribution were evaluated between sexes, and within females, between reproductive states. These data showed that the U.S. East Coast blacktip shark population distributes from Palm Beach County, FL to Long Island, NY and exhibits sexual segregation, in which females display a more truncated migratory pattern than males.
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Date Issued: 2023
PURL: http://purl.flvc.org/fau/fd/FA00014172
Subject Headings: Blacktip shark, Carcharhinus limbatus, Fishes--Migration
Format: Document (PDF)

FAU Theses and Dissertations (5)	+ -
FAU College Collections (4)	+ -
HBOI Faculty Contributions (1)	+ -
FAU Undergraduate Student Research (1)	+ -

Adaptation (Biology) (3)	+ -
Animal behavior. (1)	+ -
Animal migration. (1)	+ -
Aquatic animals--Physiology (1)	+ -
BP Deepwater Horizon Explosion and Oil Spill, 2010. (1)	+ -

Blacktip shark (1)	+ -
Carcharhinus limbatus (1)	+ -
College students --Research --United States. (1)	+ -
Deep-sea biology. (1)	+ -
Echolocation (Physiology) (1)	+ -
Electroreceptors. (1)	+ -
Fishes--Migration (1)	+ -
Magnetic fields--Physiological effect. (1)	+ -
Night Vision (1)	+ -
Oil spills--Environmental aspects. (1)	+ -
Olfactometry. (1)	+ -
Senses and sensation (1)	+ -
Senses and sensation. (1)	+ -
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Sharks--Ecology (1)	+ -
Sharks--Morphology (1)	+ -
Spectral sensitivity (1)	+ -
Stingrays (1)	+ -
Stingrays--Physiology. (1)	+ -
Visual system (1)	+ -

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article (5)	+ -
poster (1)	+ -

Kajiura, Stephen M. (10)	+ -
Florida Atlantic University (5)	+ -
Charles E. Schmidt College of Science (4)	+ -
Department of Biological Sciences (4)	+ -
Newton, Kyle C. (2)	+ -

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