In addition to gender, weight and body measurements, scientists also gather keratin (shell scrapings) and several different blood samples from the turtles. These samples are sent to different scientists all over the United States. There is a wealth of information in the samples and the data gathered from them is used in numerous areas of research. Below are brief descriptions of a few of the studies being conducted using these samples.
Sea Turtle Sex Ratios
The Owens lab has been collaborating with the South Carolina Department
of Natural Resources in their "In water sea turtle research program".
Our roll is to assist in answering the very tricky question of how
many male and female turtles there are in the populations of loggerheads,
Kemp's ridleys and green sea turtles off the Carolinas. This is a
doubly interesting question and not as trivial as it might seem. In
the first place, sea turtle sex is not externally obvious. That is
they do not exhibit secondary sex characteristics until they reach
adulthood, when it is obvious. However since sea turtles may take
from 15 to 50 years to reach sexual maturity, and since most of the
turtles in the population are juveniles, it is a serious issue. In
addition, a quirk of sea turtle biology also adds additional mystery
and importance to determining the sex ratio of these difficult to
capture animals. The sex of most vertebrates is determined by genetics,
as in the genes on human X and Y chromosomes. In sea turtles there
is no genetic sex determination; rather, sex is determined by the
temperature at which eggs are incubated. As it turns out cool beaches
like those in the Carolinas are more likely to produce males while
warmer beaches like those in Florida produce many more females (possibly
as high as 90% females). Thus, for populations that are threatened
or endangered it is of critical importance to know the male and female
production in order to be able to model and understand long-term population
Comparison of feeding areas to nesting surveys
At the University of South Carolina, we are looking at mitochondrial DNA sequence diversity in samples of individuals inhabiting feeding grounds off the coasts of Georgia and South Carolina. We genotype this feeding aggregation, then compare their genetic 'constitution' against gene frequencies collected from nesting beach surveys. Using statistical analyses, we are able to estimate the contribution of various nesting beaches to the offshore feedings aggregations. The basic message so far from these genetic analyses is that the feeding aggregation is composed primarily of individuals from nearby coastal nesting beaches. We are in year four of this study, multiple years allows us to understand the temporal variation in nesting beach contribution to offshore feeding areas.
Contaminant levels and turtle health
Environmental contaminants, such as PCBs, pesticides, and mercury, are analyzed in blood samples. Mercury is also measured in keratin scrapings from the turtles' shells. These chemicals are released into the environment by human activities and are known to accumulate in animal tissues. They are commonly found in wildlife, including sea turtles, and if the concentrations are high enough, they are known to produce toxic effects. Knowing the concentrations in the sea turtles from the southeast coast of the U.S. is important so that we can compare the concentrations to indicators of health, such as white blood cell counts, blood chemistry values, and immune system functions.
This project involves the investigation of captive, wild and rehabilitated sea turtles for plasma levels of vitamin D. Vitamin D levels have been shown to be critical for development of young turtles and healing processes. To date research has not been conducted on serum vitamin D levels or UVB spectrum lighting requirements in sea turtles. Two unique collaborative opportunities have availed themselves this year. These opportunities include obtaining plasma from wild sea turtles in South Carolina with Dr. Al Segars from the SC Department of Natural Resources and analysis of serum vitamin D levels at Boston University School of Medicine with Dr. Holick
This novel investigation will provide critical data for UVB spectrum lighting requirements for sea turtles held in captivity for display, head start, and rehabilitation programs. Understanding this nutritional need may also greatly enhance the healing process for injured sea turtles and allow for proper growth and development for head-start sea turtles. The wild sea turtle survey work is necessary to provide normal serum vitamin D levels in apparently healthy populations of sea turtles.
Leslie Boerner Neville
Publication of Project Oceanica.
For questions or comments, e-mail Oceanica.