Sea stars are marine invertebrates belonging to the phylum Echinodermata, which also includes sea urchins and sea cucumbers. They inhabit diverse marine environments, from shallow intertidal zones to the ocean’s depths, with over 2,000 known species globally. These creatures play an important role in coastal ecosystems, and understanding their longevity reveals much about their biology and the health of marine habitats. A sea star’s lifespan varies considerably, depending on the specific species and environmental conditions.
Typical Sea Star Lifespans
Sea star lifespans vary significantly across species, ranging from a few years to several decades. Many common sea star species typically live for three to five years in the wild. However, some species exhibit much longer lifespans, reaching up to 35 years in natural environments.
For example, the common sea star, Asterias forbesi, can live for up to 35 years. The common European sea star, Asterias rubens, typically lives for seven to eight years. The ochre sea star (Pisaster ochraceus), found along the Pacific coast, can live for 4 to 20 years, with some individuals recorded to reach 34 years. Smaller species, such as Leptasterias hexactis, often live for around 10 years.
The sunflower sea star (Pycnopodia helianthoides), one of the largest species, generally has an average lifespan of five to 7.5 years in the wild, though some individuals have been observed to live for up to 65 years. Their exact lifespan in the wild remains difficult to determine due to a lack of age-determining features, but some have survived for decades in aquariums.
Factors Influencing Longevity
Several factors influence a sea star’s longevity, encompassing environmental and biological characteristics. Habitat quality, including water temperature, salinity, and oxygen levels, directly impacts their survival. A healthy environment with abundant food, such as marine organisms like mussels and clams, contributes to longer lifespans, allowing them to grow and thrive. Conversely, pollution or degraded habitats can reduce longevity due to stress and limited resources.
Disease significantly affects sea star populations, with Sea Star Wasting Disease (SSWD) being a notable example. This disease, which has caused mass mortalities since 2013, leads to symptoms like lesions, body fragmentation, and rapid decay, often resulting in death within days or weeks. While the exact cause can vary, SSWD has been linked to increased water temperatures in some areas, stressing sea stars and making them more susceptible to bacterial infections. Over 20 species have been affected, leading to significant population declines.
Body size and growth rate also play a role, as larger sea stars generally live longer than smaller ones. Regeneration, the ability to regrow lost arms or even an entire body from a portion of a severed limb, aids survival from predation or injury. This process is energy-intensive and can take several months to over a year to complete. Predators, such as fish, crabs, and birds, also contribute to natural mortality, impacting their time in the wild.