Context: Scientists have identified the bacterium Vibrio pectenicida as the cause of a decade-long wasting disease that killed billions of starfish along North America’s Pacific coast.
Relevance of the Topic: Prelims: About Starfish and the cause behind its wasting disease.
Mass Mortality of Starfish
- Since 2013, starfish populations along the Pacific coast of North America have been devastated by a mysterious wasting disease leading to the death of over 5 billion sea stars.
- The disease caused disintegration of their bodies, leaving only organic mush, and triggered major ecological imbalances.
- For years, scientists suspected viruses like densovirus. Recently, researchers discovered that the disease was caused by bacterium Vibrio pectenicida, related to cholera-causing Vibrio cholerae.
About Starfish (Sea Stars):
- Habitat & Distribution: Found in all world oceans, from tropical coral reefs to cold deep-sea habitats. Most abundant in intertidal and subtidal zones.
- Feeding & Ecological Role:
- Carnivorous Predators: Feed on bivalves (clams, mussels), snails, and other invertebrates.
- Unique Feeding Method: Evert their stomachs outside their body to digest prey externally.
- Help regulate populations of prey species like sea urchins, thereby maintaining kelp forest ecosystems.
- Reproduction: Starfish reproduce both sexually (external fertilization) and asexually (regeneration).
- Regeneration: Can regrow lost arms; in some cases, a single arm can regenerate an entire new body.
- Threats: Many species face threats from:
- Marine diseases (e.g., Vibrio pectenicida in wasting disease)
- Ocean warming and acidification.
- Habitat destruction and pollution.
- Sunflower Sea Star is listed as Critically Endangered by the IUCN (2020) after a 90% population decline.
Other Key Facts:
- Starfish do not have a brain. Instead, they possess a nerve ring around the central disc, from which radial nerve cords extend into each arm to coordinate movement and sensory responses.
- They also lack a heart and blood. Circulation of nutrients, gases, and immune cells is carried out through coelomic fluid, aided by the water vascular system.
- No specialised excretory organs; nitrogenous waste is removed by diffusion through body surfaces.
Ecological Significance:
- Keystone Species Role: Starfish regulate sea urchin populations; their loss destabilises the marine food web.
- Maintains Kelp Forest Health: Overgrazing by unchecked urchin populations leads to kelp decline, reducing biodiversity and climate resilience. Kelp forests act as major blue carbon sinks; their destruction indirectly increases atmospheric CO₂.
Conservation Implications:
Identification enables targeted interventions:
- Probiotic treatments for wild starfish.
- Breeding Vibrio-resistant starfish in labs for reintroduction.
- Informs marine disease management protocols and biosecurity measures.