Parechinidae

The Parechinidae are a family of sea urchins in the order Camarodonta. They are found in the Pacific Ocean, Indian Ocean, and Atlantic Ocean. Most species of this family are small, with test diameters ranging from 2 to 5 centimeters. They are characterized by having a very prominent peristome, which is the central opening on the underside of the test. The family also has small primary tubercles, which are the bumps on the test that support the spines.

Stony Sea Urchin – Paracentrotus lividus

Common Names

Parechinidae are commonly known as pencil urchins or slate pencil urchins due to their elongated, cylindrical shape and the often white, chalky texture of their tests.

Characteristics

The defining characteristics of the Parechinidae family include:

  • Small size: Test diameters typically range from 2 to 5 centimeters.
  • Elongated, cylindrical shape: This gives them the nickname pencil urchins.
  • Prominent peristome: The central opening on the underside of the test is large and distinct.
  • Small primary tubercles: The bumps that support the spines are relatively small.
  • Usually white or light-colored tests: The test is often chalky and white, hence the name slate pencil urchin.

Environments

Parechinidae are typically found in shallow coastal waters, often in rocky or coral reef habitats. They are common in the intertidal zone and can be found down to depths of around 100 meters.

Genera

The Parechinidae family includes two genera:

  • Parechinus: This genus contains the most common species, often referred to as pencil urchins. They have a smooth, rounded test and are typically white or light-colored.
  • Coelopleurus: This genus includes species with more elongated, pointed tests. They are often darker in color than Parechinus species.

References

For more information on the Parechinidae family, refer to the following reliable sources: