“That thing looks prehistoric!” A student excitedly points out a horseshoe crab as it crawls by. This bottom-dwelling invertebrate has been in existence since before the dinosaurs, with relatively little change in its anatomy. We are ankle deep in a tidal creek that winds through the salt marsh around Cabbage Island, a small marsh island that lies between Skidaway and Wassaw islands. As an intern at the University of Georgia Marine Extension and Georgia Sea Grant, teaching about these islands and the animals that inhabit them is one of the activities I enjoy most. I’m eight months into the internship and the wonder has yet to wear off.
Spending each day teaching in and around the estuary allows us to witness the seasonal changes underway. One of the most stunning changes is the spring horseshoe crab spawning. Starting in April, horseshoe crabs will come onshore to reproduce and lay eggs along the beach. The small olive green eggs provide migratory shorebirds sustenance during their lengthy migration from Argentina to the Arctic Circle.
In addition to this ecological role, horseshoe crab blood is valuable for biomedical use. A compound found in its blood can detect the presence of bacteria, and it is used to check medical equipment to ensure that it is sterile. On a recent day, an eighth grade biology class took a field trip to observe hundreds of these horseshoe crabs and shorebirds. The class, developed by Marine Educator and Outreach Coordinator Dodie Sanders, serves both an educational and a conservation purpose.
The students are learning about the animals’ life history as well as gaining valuable research skills. They spread out along the beach equipped with data sheets, measuring tape and an identification sheet. They first collect quantitative data, by measuring the length of the telson, the long stiff tail used to aid the animal in righting itself. They also estimate if the animal is young or old based on the appearance of the hard exoskeleton.
Horseshoe crabs molt, or shed, their exoskeleton 18 times before reaching their full size. Younger animals tend to have relatively clean exoskeletons compared to the barnacle-encrusted exoskeleton of older individuals. All of the data gathered by students helps us understand more about horseshoe crab reproductive behavior and will be passed on to Jane Brockman, a researcher at the University of Florida, who is studying the mating and nesting behavior of horseshoe crabs.
At the end of the day the students will return to their school with raw data to practice analytical skills. A few small green eggs will be carefully transported to the UGA Marine Education Center and Aquarium where they will be raised to juveniles. Adult horseshoe crabs also reside in public touch tanks and accompany staff on outreach events where they capture the attention of adults and children alike. People stop in their tracks at the sight of the large brown helmet of the body bending at the hinge, their twelve, jointed legs scrambling, and the long, pointed telson swerving.
The opportunity to touch, hold and feed these animals often changes perceptions and helps the general public understand that the creatures are harmless. The telson carries no venom and is used by the animal to help flip itself upright. Many aquarium visitors spend time on Tybee Island or other barrier island beaches along the Georgia coast where they may encounter wild horseshoe crabs as they come onshore this spring. This interactive approach helps to draw a connection between humans, animals and important coastal and estuarine habitats.
Horseshoe crabs are just one of the many animals housed at the UGA Marine Education Center and Aquarium that serve as ambassadors for the surrounding salt marsh and beaches. Visitors are able to get an up close look at many of the coastal fish and invertebrates that live right in our backyard. As an educator, I feel incredibly grateful to have access to aquarium exhibits, and the coastal ecosystems they represent, as teaching resources. As the internship wraps up I will be taking away an appreciation for how hands-on interactions with live animals can spark students’ interest in conserving and studying the coast.