Written by: on May 19, 2020 @ 6:00 am

Sea urchins are often called the porcupines of the sea due to their prickly appearance. These spikey creatures can be found in all oceans, warm to cold, around the world in rock pools, mud, coral reefs, or sea grass beds. Like many invertebrates, sea urchins depend on a tough outer shell to keep them safe, and in their case, they have large spines as an extra protection measure. A sea urchin’s shell, called the test, is the organism’s defining feature.

A sea urchin’s shell is its greatest defense mechanism, warding off predators with ambulatory spikes. If a sea urchin feels a touch on its shell, their spines will point towards the source in defense. There are a few species of urchins known to release venom into the wounds that their spines create, paralyzing their victims. Snorkelers and divers are often injured when accidentally stepping on an urchin in shallow water.

Sea urchins are members of the phylum Echinodermata family which includes sea stars, sea lilies, sea cucumbers and sand dollars. This family can be identified by their hard outer body and radial symmetry once they reach adulthood. Radial symmetry means that these creatures have body parts that branch out from a central point, like the five arms of a starfish, a 5-sided example of radial symmetry.

These barbed creatures are vital for the environments they live in. While sea urchins are not currently endangered and can be found throughout the oceans of the world, their populations have been significantly impacted by pollution and the warming of our oceans. As the number of sea urchins dwindle due to human influence, the sea creatures that rely on them as a food source will be impacted as well. Protecting our oceans and wildlife must be a priority as we grow to understand the role our choices have on our planet.

Join our HTHT @ Home Science Experiment and make your own sea urchin: tps://sciencemadefun.net/downloads/EOTD_Sea_Urchin_Symmetry_Lesson.pdf

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