Dendraster excentricus, commonly known as the eccentric sand dollar, western sand dollar, Pacific sand dollar, biscuit-urchin, or sea cake, are commonly found in the Pacific Ocean, from Alaska to Baja, California. This creature has a flattened body with a distinct rounded shape. Besides, it’s covered with short spines and tiny tube feet that help it to move across the sand and capture prey.
The eccentric sand dollar is known for its irregular and asymmetrical arm arrangement, which gives it a somewhat lopsided appearance. Also, this species is an important predator in the intertidal ecosystem. It feeds on small invertebrates such as clams, snails, and other tiny organisms that live in the sand or nearby vegetation. Despite their prevalence in many coastal areas, Dendraster excentricus remains mysterious.
This informative article will explore Dendraster excentricus’ appearance, habitat, diet and ecological role, reproduction, and more.
Appearance
Biscuit urchins have five arms that are elongated and covered with small, spine-like projections called pedicellariae. They use these structures to capture and manipulate their prey. The arms are also covered with small, overlapping plates that give it a rough, sandpaper-like texture. Remember, these plates are made of calcium carbonate, the same material that makes up the shells of many marine organisms.
Their coloration can vary from pale grey or tan to shades of purple, green, and brown. The underside of the sea star is typically white or light-colored, and it is covered in tiny, tube-like feet that are used for movement and attachment to surfaces.
The food grooves, anus, and mouth are on the lower side.
Another interesting physical characteristic is their ability to change shape and size. When buried in the sand, this species can flatten itself out to increase its surface area and make it easier to move through the sand. At the same time, it can also contract its arms and raise its body off the sand to create a bowl-shaped depression that protects it from ocean currents.
Habitat
Dendraster excentricus is commonly found in intertidal areas. Since it’s a burrowing species, it prefers sandy habitats and can be found in places with fine and coarse sand.
The Pacific sand dollar is most commonly found in shallow waters, from the intertidal zone down to depths of about 30 to 90 meters. It’s often found in areas with moderate to intense wave action, and you can see them well during low tide.
Besides, it can tolerate a range of salinity levels. This species can also be found in areas with seagrass beds or kelp forests, where it may feed on small invertebrates that live among the vegetation.
Diet
Dendraster excentricus is a predator that feeds primarily on small invertebrates such as clams, snails, and other tiny organisms. This animal uses its long, flexible arms to capture and manipulate prey.
Their diet can vary depending on the availability of prey in their habitat. In areas with abundant prey, it may consume large numbers of clams or snails. On the other hand, it may feed on a broader range of small invertebrates in other areas.
Reproduction
Like other sea stars, Dendraster excentricus mainly reproduce sexually. They reach sexual maturity between one and four years of age. They have a relatively short lifespan, with most individuals living for about 5-10 years. They may undergo multiple reproductive cycles during this time, producing hundreds of offspring.
During sexual reproduction, males and females release their gametes (sperm and eggs) into the water. Fertilization occurs externally, and the resulting larvae develop and settle on the sea floor. The larvae then undergo metamorphosis and develop into juveniles that resemble adults.
Threats
Dendraster excentricus faces a variety of threats that impact its survival and abundance. Some of the main threats to this species include:
- Habitat destruction: The destruction of intertidal habitat due to human activities such as development, beach grooming, and dredging directly impacts their population.
- Pollution: Pollution from sources such as oil spills and sewage discharge have toxic effects on the species and their prey.
- Overfishing: Overfishing of the sea star’s prey species can impact the availability of food and negatively affect the sea star population.
- Climate change: Climate change and associated impacts such as ocean acidification, warming waters, and sea level rise disrupt the intertidal ecosystem and impact the distribution and abundance of Dendraster excentricus.
- Disease: Like many other sea stars, Dendraster excentricus is susceptible to sea star wasting, which can cause mass mortality and reduce the species’ population.
Despite the threats it faces, Dendraster excentricus remains an essential component of the intertidal ecosystem and is a fascinating species to observe and study.
Facts About Dendraster Excentricus
- Dendraster excentricus can be found along the western coast of North America, from Alaska to California.
- This species can grow up to 20 centimeters in diameter and has a flattened body with a distinct five-pointed star shape.
- The sand dollar sea star is a burrowing species that spends much of its time in the sand.
- Dendraster excentricus feeds primarily on small invertebrates such as clams, snails, and other tiny organisms living in the sand or nearby vegetation.
- The species faces various threats that impact its survival and abundance, including habitat destruction, pollution, overfishing, climate change, and disease.
FAQs
What is the body structure of the Dendraster excentricus?
Dendraster excentricus has a flattened body with a distinct five-pointed star shape. The body is covered with short spines and tiny tube feet that help it to move across the sand and capture its prey. Besides, its arms are arranged in an irregular and asymmetrical pattern. This gives this sea star a somewhat lopsided appearance.
Are Dendraster excentricus found in the Pacific Ocean?
Yes, Dendraster excentricus is found in the eastern Pacific Ocean along the western coast of North America, from Alaska to California. The species is typically found in the intertidal zone, where the ocean meets the shore. Moreover, it can be found on sandy beaches and rocky intertidal areas.
Can Dendraster excentricus be kept as a pet?
While Dendraster excentricus may be fascinating to observe and study, they are not typically kept as pets. They require specialized environments, feeding regimens, and care. Additionally, collecting them from the wild can negatively impact their populations and the health of the intertidal ecosystem. If need be, consult a certified expert in your locality to ascertain your level of preparedness.
Are Dendraster excentricus populations in danger?
Dendraster excentricus populations face various threats that impact their survival and abundance. Some are habitat destruction, pollution, overfishing, climate change, and disease. While the species is not currently listed as endangered or threatened, continued conservation efforts are needed to protect it and the intertidal ecosystem it inhabits.
