Lobsters are marine crustaceans found on ocean floors. They often host barnacles attached to their hard exoskeletons. This article explores the connection between barnacles and lobsters, detailing how these sessile organisms attach and the ways their presence can influence a lobster’s life.
Understanding Barnacles and Their Attachment
Barnacles are crustaceans, sharing a lineage with crabs and lobsters. Unlike their mobile relatives, adult barnacles adopt a sessile lifestyle, remaining fixed in one spot. Their life cycle begins with free-swimming larval stages that drift in ocean currents. The cyprid stage actively seeks a suitable surface for permanent attachment.
Once a cyprid larva locates a substrate, such as a lobster’s shell, it secretes a strong adhesive from its antennules, bonding the barnacle to the surface. After attachment, the larva develops into the familiar cone-shaped adult with a hard, calcareous shell. Barnacles are filter feeders, extending feather-like appendages called cirri to comb the water for plankton. Lobsters provide a stable platform, assisting these sessile filter feeders in accessing food from water currents.
How Barnacles Affect Lobsters
Barnacles can impose various burdens on lobsters. One direct impact is the increased physical load. A significant number add weight and increase hydrodynamic drag, making it challenging for the lobster to move efficiently. This additional resistance requires the lobster to expend more energy for swimming, foraging, or escaping predators.
Barnacles can also hinder a lobster’s ability to molt, the process of shedding its old exoskeleton. If barnacles heavily encrust the shell, especially near exit points or joints, they can obstruct the lobster’s emergence. A difficult or incomplete molt can be fatal, as the lobster might get stuck or suffer injuries.
Barnacle attachment can impair a lobster’s movement and feeding capabilities. If barnacles settle near limb joints or mouthparts, they can restrict the lobster’s flexibility and interfere with its ability to manipulate food. While barnacles do not directly parasitize the lobster, their firm attachment can cause localized irritation or minor shell damage. Heavy infestations may also indirectly increase a lobster’s susceptibility to predation due to reduced mobility or compromised camouflage.
Lobster Responses and Ecological Context
Lobsters possess a natural mechanism for shedding barnacles and other attached organisms: molting. As a lobster grows, it periodically sheds its entire outer shell, including any barnacles cemented to it. This process provides a fresh, clean exoskeleton, temporarily freeing the lobster from its epibionts. A new, soft shell forms underneath the old one, allowing the lobster to back out of its old casing.
Beyond molting, lobsters may also engage in grooming behaviors, using their smaller legs and claws to dislodge minor debris or loosely attached organisms. However, firmly attached barnacles are often resistant to such efforts. A common level of barnacle presence does not automatically signify an unhealthy lobster, especially if it is approaching a molt.
The relationship between barnacles and lobsters is commensal, where the barnacle benefits from a stable substrate and food access, while the lobster is largely unaffected. However, this relationship can shift if the barnacle infestation becomes severe. The burden imposed by numerous barnacles, through increased drag or molting interference, can then become detrimental to the lobster’s health and survival. This highlights the nuanced balance within marine ecosystems.