National Save the Sea Turtle Foundation provides Scholarships for FAU Biology graduate students in 2014
Biology graduate students at Florida Atlantic University were once again recipients of scholarship support from the National Save the Sea Turtle Foundation. For 2014, the Foundation doubled its contribution (from $2000 to $4000), which allowed our scholarship committee to make five award: two were continuing awards of $500 each for doctoral students who were supported last year, and three were new awards of $1000 each for students pursuing Master of Science degrees.
On behalf of the faculty in Biology who mentor these students, and as a representative of FAU's College of Science, I want to express the University's gratitude to the Foundation for its generosity and continued support. This is the third consecutive year that our graduate students have received National Save the Sea Turtle Foundation scholarships, and it's one of the reasons why the study of marine biology generally, and marine turtle biology in particular, continues to be one of the strongest programs at the University.
Here is a summary of the projects that have captivated the interest of the award recipients.
Stephanie Kedzuf: odor orientation by sea turtles.
Stephanie has been fascinated by the ability of marine turtles in the open ocean to locate regions of “high productivity”, that is, sites where they are more likely to find food. One possibility is that turtles accomplish that feat by swimming upwind toward an odor source that occurs only at oceanic sites where lots of food is available. An airborne substance (dimethyl sulfide or DMS) is used by some oceanic predators (marine birds, seals) to find those sites from several kilometers away. Could marine turtles also accomplish that feat? Recent studies done in other laboratories have shown that young loggerhead sea turtles can detect DMS, as well as the airborne odor of the artificial food they were fed while in captivity. But an ability to detect an odor doesn't mean that the animal can swim (or fly, or crawl) toward the source. Stephanie has done the experiments to find out. Her results show that neither loggerheads nor leatherbacks orient toward DMS or even food odors presented in air. However, food odors (but not DMS) presented either in air or under water induce green turtles and loggerheads to vigorously dive, search for food, and bite at any small object that remotely resembles something to eat. Similar responses to water-borne odors of jellyfish (the prey of leatherbacks) also induced a similar searching response. These results are consistent with the idea that marine turtles use a two-step process to find highly productive oceanic areas. They use their amazing magnetic maps to locate productive oceanic regions, then search the general area. When they smell prey odor, they begin a localized search which if successful, leads to a full belly.
Jacob Lasala: sea turtle sexual antics.
When Jake Lasala started researching sea turtles, he quickly noticed that most of our efforts are focused on counting and examining nesting females and their hatchlings on the beach. He wondered why no one was paying attention to male marine turtles and their contribution to this whole process. His research focuses on how male green turtles, loggerheads and leatherbacks contribute to the offspring from those nesting beaches and to their populations as a whole. To find out, Jake takes tissue samples from the nesting female and, as they emerge some 50 days later from the nest, a sample of her hatchlings. He then looks for genes in the hatchling that do not match Mom's genes; those must be from Dad! Further analysis enables him to determine whether that female mated with a one male or with two or more males. By repeating this process many times at a single nesting beach, Jake can determine how many males are offshore, looking for mates and contributing to the progeny at each nesting beach. He can also determine if the males are related to one another as brothers or cousins.
Knowing how many males are available to mate with females is obviously an important aspect of the biology of any species, and especially endangered marine turtles. In marine turtles, sex is determined in part by the temperature of the sand surrounding the developing eggs. Scientists are know that the earth is gradually warming. If this process continues unabated, the result will be the production of too many female turtles and not enough males. It's therefore essential to not only count the number of females that nest each year and the number of hatchlings that they produce. It's also important to “count” the number of males the females choose as mates, even though mating itself occurs out to sea and under water where humans (at least in most instances) can’t observe it. Jake's research helps get us one step closer to understanding how these marine turtles behave in the ocean, how easily they find mates, and how at some future date, we may have to manage the temperature of the sand around those nests to make sure that there are always enough male marine turtles.
Alexandra Lolavar: moisture and sex determination.
Alex is interested in understanding the impact of environmental factors on the nest environment in which sea turtle eggs complete development. That subject is an important aspect of sea turtle conservation, particularly because nest conditions during incubation greatly influence not only whether the eggs develop into viable hatchlings, but also the sex of the hatchlings. Sea turtles have temperature dependent sex determination (TSD) which is characterized by the production of males at cooler temperatures and females at warmer temperatures (the “cool guys” and “hot babes” rule). While biologists remain confident of temperature's role in sex determination, many studies have also attempted to understand if other factors are involved. Much of our understanding of how temperature determines sex comes from laboratory studies under constant conditions of temperature and humidity. However in the real world, nests on the beach can be affected by rainfall after a tropical storm system passes by, and influences the amount of moisture in the sand. Moisture in the form of rainfall is an environmental factor that has received relatively little attention; attempts to understand the influence of moisture on sex ratios have to a large extent failed, at least until now.
Alex's study aims to address the impacts of increased moisture on nest conditions and hatchling biology. She is designing experiments that will reveal whether moisture alone, or in combination with evaporative cooling, might result in the production of more males. The preliminary data thus far suggests that it does, and for that reason the hypothesis that global warming will lead to an overwhelming production of females may be premature. Global warming also results in an increase in evaporation, more storms and more precitation, all of which can have as of yet unknown effects on hatchling sex ratios. For those reasons, data from this study will provide much needed insights.
Andrea Reis and Boris Tezak: Identifying the sex of a hatchling.
You may have gathered from the above that we're just beginning to understand the mating behavior of marine turtles, as well as the way progeny of each sex are determined by environmental conditions. But to complicate matters even further, before marine turtles become sexually mature, it is very difficult (some would say impossibly difficult) to tell a boy from a girl on the basis of external appearance. Yet doing so, without having to either sacrifice the turtle or raise it to an older age under laboratory conditions, is of paramount importance for quickly and inexpensively estimating how many turtles of each sex are being produced annually at our nesting beaches. Andrea and Boris are each exploring novel techniques to determine sex from a tiny drop of hatchling blood, looking for markers that can provide scientists and turtle conservationists alike with reliable information at a minimal cost (to both the scientists and the turtles).
Andrea is in the process of developing a method to quantify concentrations of steroid hormones in the blood (estrogens, testosterone, and progesterone) of hatchlings, using a specialized technique called “High Performance Liquid Chromatography” or HPLC. This method provides a profile of these hormones in the blood; that profile differs between males and females, enabling a trained scientist to distinguish between the sexes.
Boris's method involves an entirely different approach: This procedure detects differences in certain proteins in the tissues of young turtles, even as hatchlings. Those differences in protein concentration ultimately cause the bipotential (meaning it can go either toward malesness or femaleness) sexual organ to turn into an ovary of a female or the testes of a male. These differences are present in the embryos, even before the eggs hatch! This technique is an extremely reliable method for identifying the sex of sea turtles – especially in species (like the leatherback) that are harder to sex. Currently, Boris is applying this technique to accurately identify the sex of the hatchlings of two of our common marine turtles - loggerheads and leatherbacks.