2017 National Save-The-Sea-Turtle Foundation Graduate Scholarships at Florida Atlantic University
Mike Salmon, Ph.D., Research Professor
Department of Biological Sciences
Florida Atlantic University
Department of Biological Sciences
Florida Atlantic University
The National Save The Sea Turtle Foundation has again funded generous scholarships for graduate students in the Department of Biological Sciences at Florida Atlantic University. An increase in the dollar amount this year enabling the department to provide support to 8 talented, hard-working students who are making substantial progress toward completing advanced (Masters, Doctoral) degrees. Their research projects have in common that they deal with central topics in marine biology: how animals are functionally designed, how they exploit and perceive their environment, how they interact with one another, and how they are affected by human-induced environmental change.
It’s no accident that the organisms selected for these studies are “charismatic megafauna” – large, magnificent creatures that have persisted on earth for millions of years, play a dominant role in marine ecosystems, and have captured the interest and attention of humans throughout our history. They are unfortunately also organisms whose numbers have been severely depleted, thanks to our increasingly efficient ability to harvest them and to degrade the habitats they require to replace their numbers. These are, specifically, the marine turtles and the cartilaginous fishes (sharks, skates, rays).
It’s also no accident that our marine biology faculty and students highlight these animals as subjects, and center their work on these important topics. The knowledge gained from the studies described below will contribute importantly to our understanding of how these creatures can be managed to promote their recovery. Those goals will only be accomplished by faculty and students that set high standards for achievement. But, we also depend upon the financial support provided by organizations sympathetic to our objectives, such as the National Save The Sea Turtle Foundation.
It’s no accident that the organisms selected for these studies are “charismatic megafauna” – large, magnificent creatures that have persisted on earth for millions of years, play a dominant role in marine ecosystems, and have captured the interest and attention of humans throughout our history. They are unfortunately also organisms whose numbers have been severely depleted, thanks to our increasingly efficient ability to harvest them and to degrade the habitats they require to replace their numbers. These are, specifically, the marine turtles and the cartilaginous fishes (sharks, skates, rays).
It’s also no accident that our marine biology faculty and students highlight these animals as subjects, and center their work on these important topics. The knowledge gained from the studies described below will contribute importantly to our understanding of how these creatures can be managed to promote their recovery. Those goals will only be accomplished by faculty and students that set high standards for achievement. But, we also depend upon the financial support provided by organizations sympathetic to our objectives, such as the National Save The Sea Turtle Foundation.
Rachel Bladow
Response to Human-Induced Environmental Change
Climate change is predicted to result in a rise in average temperature, changes in the distribution of rainfall, as well as changes in the severity and frequency of storms and hurricanes. Rachel Bladow’s research is designed to identify
Climate change is predicted to result in a rise in average temperature, changes in the distribution of rainfall, as well as changes in the severity and frequency of storms and hurricanes. Rachel Bladow’s research is designed to identify
the effects of these climatic perturbations on the productivity of sea turtle nests on our beaches. Rachel collects all unhatched eggs from the nest after the hatchlings have emerged. After opening all the unhatched eggs, she then determines the stage of development when the embryos died, all as a function of what happened to the nest during incubation. If incubation temperatures are too hot, embryonic death can occur, leading to a decrease in hatching and emergence success.
The goal is to determine which stages of embryonic development are vulnerable to these high temperatures. The 2016 nesting season was unusually warm and dry, which resulted in high average temperatures inside the nest and a large proportion of death during embryonic development. The result has been a steady decline in average nest productivity on Boca Raton beaches from about 80% of the eggs resulting in hatchlings that left the nest in 2013, to about 38% (for loggerheads) and 54% (for green turtles) in 2016.
Alexandra Lolavar is studying how climatic conditions affect hatchling sex ratios (the proportion of male to female turtles that develop from a sample of eggs). In sea turtles the environment, and especially temperature, determines each individual’s sex. Warmer temps result in more females and cooler temps in more males (the “hot” babes, “cool” guys rule). This principle applies when sea turtle eggs are incubated at a fixed temperature under laboratory conditions. However, sex ratios are unpredictable under natural conditions as nests experience fluctuating temperatures. Alex found that nests exposed to similar ambient temperature but more rainfall produced more males than nests exposed to drier conditions. Her research now centers on better defining the relationship between temperature, moisture, and other variables (such as oxygen availability) as contributors to nest sex ratios. Her work has also forced biologists to consider how changes in precipitation patterns, also predicted to occur as a result of climate change, will affect the number of male and female hatchlings ultimately produced by natural nests.
Alexandra Lolavar
Alexandra Lolavar is studying how climatic conditions affect hatchling sex ratios (the proportion of male to female turtles that develop from a sample of eggs). In sea turtles the environment, and especially temperature, determines each individual’s sex. Warmer temps result in more females and cooler temps in more males (the “hot” babes, “cool” guys rule). This principle applies when sea turtle eggs are incubated at a fixed temperature under laboratory conditions. However, sex ratios are unpredictable under natural conditions as nests experience fluctuating temperatures. Alex found that nests exposed to similar ambient temperature but more rainfall produced more males than nests exposed to drier conditions. Her research now centers on better defining the relationship between temperature, moisture, and other variables (such as oxygen availability) as contributors to nest sex ratios. Her work has also forced biologists to consider how changes in precipitation patterns, also predicted to occur as a result of climate change, will affect the number of male and female hatchlings ultimately produced by natural nests.
Boris Tezak
What does seem clear, however, is that warmer temperatures bias sex ratios toward females but by how much, how often, and at what beach locations? Boris Tezak and his collaborator, Itzel Sifuentes are attempting to answer these questions. The problem is that hatchling sex can’t be determined by external appearance. In the past, the only alternatives were to sacrifice the turtle to examine its reproductive organs (not a solution when dealing with endangered species!) or to rear turtles in the laboratory until they were large enough to distinguish sex by laparoscopy (a time-consuming and expensive procedure).
Tezak and Sifuentes have developed a reliable method for determining hatchling sex by taking a small drop of blood and testing for the presence of sex-specific proteins. That procedure should allow biologists to immediately and inexpensively estimate the sex ratios of the turtles produced annually from nests placed not only on Florida’s beaches, but on nesting beaches worldwide.
Given that climate change is likely to shift sex ratios toward the production of more females, could there come a time some 15-20 years from now (as today’s hatchlings become sexually mature) when there won’t be enough males to service all the females? Since mating takes place out to sea, how would we even know that such a problem existed? We might recognize the problem if we knew how many males mate with individual females now, making any change occurring later obvious. Jake Lasala has been using genetics to characterize mating patterns and, at the same time, estimate the number of sexually active males to sexually active females present in current populations. His findings thus far indicate that some marine turtles are promiscuous, that is, the 100 or so hatchlings from each nest usually are sired by more than one father. Each female loggerhead, for example, mates with between 4 and 5 males whereas each green turtle female mates with 1-3 males. Jake has not found the same male mating with more than any one of the many females whose nests he has surveyed. That suggests that presently, there are plenty of males for each female but that situation could change if warmer temperatures result in nests producing an overabundance of female hatchlings. This study also leads to another important conclusion: females apparently prefer to mate with more than one male, probably because by doing so they produce hatchlings that are more genetically diverse than if their mom had only one mate. That diversity could promote better hatchling survival but advantages like that disappear if male representation in the population continues to decline.
Given that climate change is likely to shift sex ratios toward the production of more females, could there come a time some 15-20 years from now (as today’s hatchlings become sexually mature) when there won’t be enough males to service all the females? Since mating takes place out to sea, how would we even know that such a problem existed? We might recognize the problem if we knew how many males mate with individual females now, making any change occurring later obvious. Jake Lasala has been using genetics to characterize mating patterns and, at the same time, estimate the number of sexually active males to sexually active females present in current populations. His findings thus far indicate that some marine turtles are promiscuous, that is, the 100 or so hatchlings from each nest usually are sired by more than one father. Each female loggerhead, for example, mates with between 4 and 5 males whereas each green turtle female mates with 1-3 males. Jake has not found the same male mating with more than any one of the many females whose nests he has surveyed. That suggests that presently, there are plenty of males for each female but that situation could change if warmer temperatures result in nests producing an overabundance of female hatchlings. This study also leads to another important conclusion: females apparently prefer to mate with more than one male, probably because by doing so they produce hatchlings that are more genetically diverse than if their mom had only one mate. That diversity could promote better hatchling survival but advantages like that disappear if male representation in the population continues to decline.
Environmental Perception and Exploitation
Christina Coppenrath is increasing our understanding of how leatherbacks exploit their environment by determining how these turtles select oceanic habitats where they feed. Female leatherbacks migrate long distances from the subtropical and tropical beaches where they nest to the highly productive, cold water oceanic regions where they feed. Each female can spend 2 – 4 years feeding before they sequester sufficient energy to migrate back to the tropics, produce hundreds of eggs, and nest once again. There is growing evidence that females remember the location of their nesting beach based upon characteristics they learned as hatchlings, but little is known about how they select their feeding sites. Some biologists have speculated that there might be a link, expressed genetically, between where females nest and where they feed. Christina has been testing that hypothesis with leatherbacks that nest on Florida’s beaches. She uses novel molecular techniques that not only identify the female genetically but also the oceanic region where she feeds. Both female genetics and feeding signatures are present in and can be analyzed from small samples of skin and blood, taken from the female while she is nesting. Christina has identified sites where females are feeding before they nest but hasn’t found a link between female genetics and feeding location. Apparently, each female decides where to feed using criteria that differ from those used to select a nesting site. That discovery actually makes good sense since
the characteristics that make each of these locations “optimal” are unrelated. Moving forward, she will compare the oceanic habitats that are exploited by Florida’s leatherbacks to those utilized by other leatherback populations in the Atlantic Ocean.
For over 50 years, biologists have been intrigued by the ability of hatchling sea turtles to immediately orient toward the sea (“seafinding”), within seconds after emerging from an underground nest into a world that they’ve never before encountered. How they do it is a story that has become more interesting as old explanations become modified by new discoveries. There has remained one constant: hatchlings depend upon visual cues. But visual information can include many features - light intensity, color, form vision or some combination of those attributes – each of which needs to be identified. Adding to this complexity is that hatchling
Christina Coppenrath is increasing our understanding of how leatherbacks exploit their environment by determining how these turtles select oceanic habitats where they feed. Female leatherbacks migrate long distances from the subtropical and tropical beaches where they nest to the highly productive, cold water oceanic regions where they feed. Each female can spend 2 – 4 years feeding before they sequester sufficient energy to migrate back to the tropics, produce hundreds of eggs, and nest once again. There is growing evidence that females remember the location of their nesting beach based upon characteristics they learned as hatchlings, but little is known about how they select their feeding sites. Some biologists have speculated that there might be a link, expressed genetically, between where females nest and where they feed. Christina has been testing that hypothesis with leatherbacks that nest on Florida’s beaches. She uses novel molecular techniques that not only identify the female genetically but also the oceanic region where she feeds. Both female genetics and feeding signatures are present in and can be analyzed from small samples of skin and blood, taken from the female while she is nesting. Christina has identified sites where females are feeding before they nest but hasn’t found a link between female genetics and feeding location. Apparently, each female decides where to feed using criteria that differ from those used to select a nesting site. That discovery actually makes good sense since
Christina Coppenrath
For over 50 years, biologists have been intrigued by the ability of hatchling sea turtles to immediately orient toward the sea (“seafinding”), within seconds after emerging from an underground nest into a world that they’ve never before encountered. How they do it is a story that has become more interesting as old explanations become modified by new discoveries. There has remained one constant: hatchlings depend upon visual cues. But visual information can include many features - light intensity, color, form vision or some combination of those attributes – each of which needs to be identified. Adding to this complexity is that hatchling
orientation usually occurs at night, and vision at night depends upon receptors that are very sensitive to light but insensitive to its color, known as rods. For that reason, it was largely believed that seafinding was accomplished by using only light intensity cues, coupled with form vision. But, recent discoveries indicate that light consisting of the
shorter wavelengths (ultraviolet, violet and blue), that rods can’t detect, evoke the strongest orientation responses from hatchlings, and these wavelengths are present at nesting beaches, even at night. Lisa Celano plans experiments designed to measure the light wavelengths at the beach, then compare that wavelength distribution to how well green turtles orient to the same wavelengths under laboratory conditions. This combination of field and lab observations should at long last explain how sea turtles use wavelength, in addition to other cues, to locate the sea – at least for now!
Biomechanical Structure and Function
Two of our graduate students have interests in the mechanical properties of the muscles, bones and ligaments used by aquatic animals to swim so efficiently. Sharks are of special interest since in these animals, the skeleton is composed mostly of cartilage rather than bone. It turns out that the properties of cartilage vary and can support efficient swimming. That said, our understanding of how locomotion is accomplished in these and other large marine animals is far from complete.
Danielle Ingle is a third year doctoral student with a strong background in exercise science, anatomy and biomechanics. Her research passion is investigating how bones from the spine of large aquatic animals such as manatees, dolphins, and sharks, are structured to support and withstand the stresses involved in underwater movement. In previous studies she has gained experience dissecting the spinal columns of several species of dolphins and whales, and has used computer tomography (CT) scans to better understanding relationships between vertebral structure and function. She is now analyzing the mechanical properties of the vertebrae found in these animals by measuring their ability to withstand compressive forces, mimicking those that occur during active swimming by each species.
Danielle Ingle
Biomechanical Structure and Function
Two of our graduate students have interests in the mechanical properties of the muscles, bones and ligaments used by aquatic animals to swim so efficiently. Sharks are of special interest since in these animals, the skeleton is composed mostly of cartilage rather than bone. It turns out that the properties of cartilage vary and can support efficient swimming. That said, our understanding of how locomotion is accomplished in these and other large marine animals is far from complete.
Danielle Ingle is a third year doctoral student with a strong background in exercise science, anatomy and biomechanics. Her research passion is investigating how bones from the spine of large aquatic animals such as manatees, dolphins, and sharks, are structured to support and withstand the stresses involved in underwater movement. In previous studies she has gained experience dissecting the spinal columns of several species of dolphins and whales, and has used computer tomography (CT) scans to better understanding relationships between vertebral structure and function. She is now analyzing the mechanical properties of the vertebrae found in these animals by measuring their ability to withstand compressive forces, mimicking those that occur during active swimming by each species.
Sarah Hoffman
Lisa Celano
