Runcinida
Runcinida is an order of small, predatory sea slugs, belonging to the class Nudibranchia within the phylum Mollusca. These fascinating creatures are characterized by their unique morphology and often striking coloration, which makes them a popular subject for marine biologists and enthusiasts alike.
Common Names
Runcinida are commonly known as "aeolids" due to their prominent cerata, which are finger-like projections along their backs. They are also sometimes called "aeolid nudibranchs" or "aeolid sea slugs."
Characteristics
Runcinida possess several distinctive features that set them apart from other nudibranchs. Some of the most notable characteristics include:
- Cerata: The most striking feature of aeolids is their numerous, finger-like projections known as cerata. These cerata are covered in cnidosacs, which are sacs that contain stinging cells called nematocysts. The nematocysts are acquired from the prey, typically hydroids, and are used for defense and to paralyze prey.
- Rhinophores: Aeolids have two sensory organs called rhinophores located on the top of their heads. These rhinophores are used to detect food and other stimuli in their environment.
- Mouth: The mouth of an aeolid is equipped with a radula, a ribbon-like structure with rows of teeth. The radula is used to scrape food off surfaces and to tear prey.
- Digestive System: Aeolids have a simple digestive system that allows them to quickly process their food. The cerata play a crucial role in digestion, with the cnidosacs containing enzymes that break down prey.
- Coloration: Aeolids exhibit a wide range of colors and patterns, often resembling their prey or their surrounding environment. This coloration serves as camouflage, warning coloration, or a combination of both.
Environments
Runcinida are found in a variety of marine environments, including shallow waters, rocky shores, and kelp forests. They are typically found on the underside of rocks, in crevices, or on seaweed. Some species may even be found in deeper waters.