Learning and memory using nociceptors in the sea hare, "Aplysia" has been described. Their leathery skin contains toxins which make this sea hare practically inedible to most predators. In the Philippines the eggs of the Sea Hare are eaten as a delicacy. This species of sea hare is unique for its shell resilience in acidified ocean environments. "Aplysia parvula" was long seen as a circumtropical sea hare species, but Golestani et al. Some gastropods, such as the sea hare "Aplysia", appear to lack respiratory pigments altogether. This sea hare may be found in dense concentrations or singly. This sea hare occurs in the eastern Atlantic and the Mediterranean. This sea hare lives in areas that are sheltered from rough currents. In the sea hare "Aplysia californica", the rhinophores are able to detect pheromones. Like all "Aplysia" species, the California sea hare is herbivorous. This is a circumtropical sea hare, the only species in its genus. This sea hare has no purple gland and therefore cannot produce ink, just milky secretions.