Eccentric Sand Dollar

Fascinating facts about the Eccentric Sand Dollar

• The eccentric sand dollar typically measures about 76 mm across, but exceptional individuals can reach a width of 120 mm, making them noticeably larger than most of their peers. Their test is a broad, flattened disc that rests on the seabed and often washes ashore, where its shape is easy to recognise. The colour of the living animal ranges from gray and brown to black or shades of purple, while the dead skeleton appears grey-white on beaches.
• In suitable sandy habitats a single square yard can support as many as 625 eccentric sand dollars, creating a dense carpet of overlapping tests that are half buried in the substrate. This remarkable density is typical of both subtidal bays and the low intertidal zone along the northeast Pacific coast, where the animals congregate for feeding and protection.
• When a steady water flow passes over them, eccentric sand dollars gather in aligned rows, digging their front edges into the sand and raising their rear edges so the current sweeps across their bodies from right to left. This orientation turns each disc into a hydrofoil, channeling suspended food particles toward their mouths and enhancing feeding efficiency for the whole group.
• Eccentric sand dollars can live for as long as thirteen years, a figure that scientists determine by examining the animal's hard test. By counting the concentric growth rings on the calcareous plates or the tiny pores arranged in a petal of the petalidium, researchers can estimate an individual's age. This long lifespan means that, unlike many predators, old age itself is considered the primary cause of death for the species.
• Mass mortality events strike eccentric sand dollars when extreme conditions expose them to air or force them onto the beach. If a low tide occurs at a hot midday, the animals can be left out of the water for only two to three hours, leading to rapid desiccation, while powerful storms can wash them ashore where they become buried in sand.

Sources

Every fact above was checked against these pages, and kept only where one of them states it.

• Wikipedia

At a glance

About the Eccentric Sand Dollar

In the shifting sands of the ocean floor, the eccentric sand dollar moves with a quiet purpose, its numerous tiny tube feet rippling like a ghostly aura as it slowly rotates to face the currents that bring it sustenance. As it burrows into the sediment, its fragile, flower-like body remains exposed, a testament to its remarkable adaptability in this harsh, submerged world. With each delicate movement, the sand dollar weaves a subtle spell of resilience, its very existence a reminder of the intricate beauty that thrives in the darkest, most mysterious depths of our planet.

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