Sea turtles often carry various organisms on their shells and bodies, including barnacles, a type of crustacean. While many barnacle-turtle relationships are harmless, known as commensalism, a heavy accumulation or attachment by specialized species can cause significant harm.
The Nature of Barnacle-Turtle Relationships
Barnacles are sessile crustaceans, meaning they remain fixed in one place as adults. They begin their lives as free-swimming larvae, seeking a hard surface to attach to and cementing themselves permanently. Sea turtles provide an ideal mobile habitat, offering a stable platform, constant transport through nutrient-rich waters for filter feeding, and protection.
The most common barnacles found on sea turtles belong to the genus Chelonibia. The species Chelonibia testudinaria is frequently observed on their shells. This association is generally considered commensal, where the barnacle benefits from the ride and access to food, while the turtle is typically unaffected. However, this relationship can become problematic when barnacle numbers become excessive or when certain types of barnacles embed themselves into the turtle’s tissues.
Specific Harms to Sea Turtles
Barnacles can impact sea turtles, particularly when infestations are severe. A substantial number increases the turtle’s surface area and disrupts its streamlined shape, leading to greater hydrodynamic drag. This increased resistance makes swimming more difficult and requires the turtle to expend more energy for routine activities such as foraging, migrating, or escaping predators.
Barnacles growing near a turtle’s sensory organs can also pose direct threats. If they attach around the mouth, they can interfere with the turtle’s ability to forage and eat effectively. Barnacles on the eyelids or nostrils can obstruct vision, making it challenging for the turtle to navigate and find food, or impede breathing.
Certain barnacle species, known as embedding barnacles, can cause direct physical damage. These species, such as Stephanolepas muricata, can bore into the turtle’s shell or soft tissues, creating lesions, eroding the shell, or providing entry points for bacterial and fungal infections. Even surface-attaching barnacles, if present in large numbers, can cause skin irritation and abrasions, potentially leading to secondary infections.
Additionally, the accumulated weight from extensive barnacle growth can affect the turtle’s buoyancy, making it harder to surface for air or dive for food. An excessive barnacle load often signals that the turtle may already be in a weakened state due to illness, injury, or malnutrition, as healthy turtles are generally better able to manage their epibiont loads.
Managing Barnacle Overgrowth
Sea turtles employ several natural strategies to manage barnacle growth. Some species, like green sea turtles, can shed barnacles when they naturally molt their scutes, the plates that make up their shell. Turtles also rub their shells against hard surfaces like rocks or coral to dislodge attached organisms. In some marine environments, turtles may visit “cleaning stations” where various fish species, such as surgeonfish, will consume barnacles and algae from their bodies. Healthy and active turtles are generally more effective at keeping their barnacle loads in check.
When barnacle infestations become severe and compromise a turtle’s health, human intervention is often necessary. Marine animal rehabilitation centers and veterinarians provide care for heavily encrusted and debilitated turtles. The process typically involves the careful manual removal of barnacles using specialized tools. This procedure requires precision to avoid further injury to the turtle’s shell or skin.
After removal, turtles may receive freshwater soaks to eliminate any remaining barnacle remnants, along with antibiotics for potential infections and supportive care for dehydration or malnutrition. Such interventions are reserved for cases where the barnacle overgrowth significantly threatens the turtle’s survival.