Costasiella
Costasiella is a genus of sacoglossan sea slugs, commonly known as “sea sheep” or “leaf slugs” due to their distinctive appearance and feeding habits. These small, brightly colored mollusks are found in tropical and subtropical waters around the world, particularly in the Indo-Pacific region. They are known for their ability to photosynthesize, a unique adaptation that allows them to derive energy from sunlight like plants.
Characteristics
Members of the genus Costasiella typically have elongated, oval-shaped bodies with a pair of prominent rhinophores, which are sensory organs used for detecting food and their surroundings. Their bodies are covered in cerata, finger-like projections that give them a sheep-like appearance, hence the name "sea sheep". These cerata not only help with respiration but also serve as a defense mechanism by storing stinging cells from their prey, siphonophores, which are colonial organisms that include the Portuguese Man-of-War.
One of the most remarkable features of Costasiella is their ability to steal chloroplasts from their algal prey and incorporate them into their own cells, a process known as kleptoplasty. These chloroplasts, called "kleptoplasts", continue to photosynthesize within the sea slug's body, providing them with an additional source of energy. This adaptation allows Costasiella to survive for weeks without eating, relying solely on the energy produced by their stolen chloroplasts.
Costasiella species exhibit a wide range of colors, including green, blue, orange, and yellow, which often reflect the colors of their algal diet. This color variation is a form of camouflage, helping them to blend in with their surroundings and avoid predation.
Environment
Costasiella species are typically found in shallow, coastal waters, particularly in areas with abundant algae. They prefer habitats with rocky shores, seagrass beds, and coral reefs. These sea slugs are often found on the undersides of rocks, in crevices, and on seaweed, where they can access their primary food source, algae.
Diet
Costasiella species are herbivores, feeding primarily on various types of algae, particularly members of the genus Vaucheria. They use their radula, a ribbon-like structure in their mouth, to scrape algae from surfaces and ingest them. While they can also consume other types of algae, their primary diet is Vaucheria, which is essential for their kleptoplasty process.
Reproduction
Costasiella species are hermaphrodites, meaning that they possess both male and female reproductive organs. They reproduce sexually, typically laying their eggs in clusters on the underside of rocks, seaweeds, or other surfaces.
References
For further information, see these references: