Sharks, often regarded as the ocean’s apex predators, are frequently perceived as impervious to the ailments affecting other creatures. Despite this perception, sharks are susceptible to various diseases and health challenges, much like other marine wildlife. Their health often reflects the overall condition of the ocean itself.
Yes, Sharks Experience Illness
Sharks can be affected by a range of diseases, including bacterial, viral, and fungal infections. Bacterial infections, such as those caused by Vibrio or Staphylococcus, can manifest as lesions, discoloration, fin rot, and lethargy, particularly in injured or stressed sharks. Viral infections, though less documented, include a herpes-like viral dermatitis. Fungal infections, while less common, can also occur, especially in weakened or injured individuals.
Parasites, both internal and external, are frequently found in sharks and can significantly impact their well-being. Internal parasites like tapeworms can lead to weight loss and organ stress if infestations are heavy. External parasites, such as copepods, attach to the shark’s gills or skin, potentially causing irritation or secondary infections.
Sharks are not immune to tumors and cancer. Scientists have documented tumors in over 23 different shark species, affecting various organs including cartilage, livers, and reproductive organs. While the incidence of cancer might appear lower than in some other animals, this could be partly due to internal tumors often being invisible, and sick or deceased sharks typically sinking, making observation difficult. Severe injuries can compromise a shark’s health, leading to infections and sometimes the development of lesions or tumors.
The Shark Immune System
Sharks possess a sophisticated immune system, comprising both innate and adaptive components, which contributes to their remarkable resilience. Their ability to heal rapidly from wounds is particularly notable, even in marine environments teeming with bacteria. This rapid healing involves swift anti-inflammatory responses and is supported by a unique microbiome on their skin. Studies have shown that even severe injuries can heal remarkably quickly, with some whale sharks regenerating significant portions of their fins within months.
Research into shark biology has revealed unique adaptations within their immune system. Scientists have identified a compound called squalamine, originally found in dogfish shark livers, which exhibits potent antiviral properties against a range of human viruses, including hepatitis and dengue fever. This substance works by interfering with viral replication and has also shown promise in inhibiting tumor growth.
Genetic studies uncover unique modifications in shark immunity genes, believed to underpin their efficient wound healing and potential disease resistance. While sharks do get cancer, the historical misconception of their immunity was partly fueled by their cartilaginous skeletons. Scientific understanding confirms their robust immune system does not grant absolute immunity.
Environmental Factors Affecting Shark Health
External influences significantly impact shark health, often making them more vulnerable to illness. Pollution is a major concern, as sharks, being apex predators, accumulate high concentrations of toxic substances through bioaccumulation and biomagnification. These substances can build up in their tissues over their long lifespans, affecting their immune function, reproductive health, and behavior.
Plastic pollution, especially microplastics, poses a growing threat. Sharks can ingest microplastics, which can cause physical damage to their digestive tracts and increase exposure to adsorbed toxins. Ingested microplastics can also lead to malnutrition and interfere with immune responses and reproductive processes.
Habitat degradation, including the loss of crucial nursery and feeding grounds, stresses shark populations and diminishes their health. Climate change exacerbates these pressures through rising ocean temperatures, which alter prey distribution and force sharks to shift migratory patterns. This can increase sharks’ energetic demands and reduce their metabolic efficiency. Ocean acidification can also impair a shark’s ability to locate food.
Human interactions, particularly fisheries, also contribute to shark health issues. Injuries from fishing gear can lead to chronic inflammation, infections, and even death. Boat strikes are another source of severe trauma. The stress associated with capture and release during fishing activities can also compromise a shark’s immune system, leaving them more susceptible to disease.