Parasaleniidae
Parasaleniidae is a family of irregular sea urchins within the order Spatangoida. They are commonly known as “heart urchins” due to their heart-shaped bodies. These echinoderms are characterized by their flattened, oval-shaped tests (shells) and their specialized feeding structures.
Characteristics
Parasaleniid sea urchins exhibit several distinguishing features:
- Heart-shaped test: The test is flattened and heart-shaped, with a distinct anterior (front) and posterior (rear) end.
- Apical disc: The apical disc, located at the top of the test, contains the madreporite (a porous plate) and other sensory structures.
- Ambulacra: The ambulacra, or rows of tube feet, are arranged in a pattern of five pairs, with the anterior pair being the largest and most prominent.
- Peristome and periproct: The mouth (peristome) is located on the ventral (bottom) side of the test, while the anus (periproct) is positioned on the posterior end.
- Feeding apparatus: Parasaleniids have a specialized feeding apparatus called an "Aristotle's lantern," which consists of five calcium carbonate teeth used for scraping and ingesting food.
Environment
Parasaleniidae are primarily found in marine environments, inhabiting sandy or muddy bottoms in shallow to deep water. Their distribution is global, with species occurring in various oceans around the world.
References
For more information about Parasaleniidae, please refer to these reliable sources: