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Nudibranch Pleurobranch Sea hares Bubble shells

Doridacea.gif

 The term Nudibranch is derived from the New Latin word Nudibranchia. “Nudus” means naked n Latin, while “branchia” means gills in Greek. The name Nudibranch can thus be translated into “naked gills”.

Nudibranchs possess a radular feeding organ, but they characteristically lack a shell, gills, and mantle cavity typical of other mollusks. The delicately coloured body has bizarre outgrowths, called cerata, which serve a defensive function, discharging nematocysts that the nudibranch has ingested from cnidarian prey. Cerata also function in gas exchange. Antenna-like organs (rhinophores) arise from the animal’s head. Nudibranchs reach lengths of 50mm .

Nudibranchs are devided into the following 4 classes Doridacea,Arminacea, Aeolidacea and Dendronotacea with Doridacea as the largest group

Nudibranchs occur in the shallow waters of all the world’s oceans, where they feed chiefly on other invertebrates, particularly sea anemones. Those of the family Tethyidae can swim. Among bottom creepers in warm seas are the doridacean nudibranchs such as Doris and Glossodoris.

 

 The Pleurobranchidae are a taxonomic family of sea slugs, marine opistobranch gastropod molluscs in the order Notaspidea.

The species in the family Pleurobranchidae have a prominent mantle and an internal shell that becomes reduced or is lost in adults. Some adult species have been seen feeding on ascidians. While larval pleurobranchids can be planktotrophic (feeding on plankton), lecithotrophic (deriving nutrition from yolk), or direct developing, many species produce secretions from their rich glandular mantle as a chemical defense against predators. Even the production of sulfuric acid has been reported.

Until recently this family was placed in the suborder Notaspidea. However, in the new taxonomy of Bouchet & Rocroi (2005), the family Pleurobranchidae has been placed in the superfamily Pleurobranchoidea, the only family belonging to the subclade Pleurobranchomorpha (sister to the subclade Nudibranchia), part of the clade Nudipleura

 The clade Aplysiomorpha commonly known as Sea hares (Aplysia species and related genera) are medium-sized to very large sea slugs with a soft internal shell made of protein. These are marine gastropod molluscs in the superfamilies Aplysioidea and Akeroidea.

The common name "sea hare" derives from their rounded shape and from the two long rhinophores that project upwards from their heads and that somewhat resemble rabbit ears.

Sea hares are mostly rather large, bulky creatures. The biggest species, Aplysia vaccaria, can reach a length of 75 centimetres  and a weight of 2 kilograms  and is arguably the largest gastropod species.

Sea hares have soft bodies with an internal shell, and like all opistobranch mollusks they are hermaphroditic. Unlike many other gastropods, they are more or less bilaterally symmetrical in their external appearance. The foot has lateral projections, or "parapodia"

 The suborder Cephalaspidea, also known bubble snails, is a suborder of sea slugs and bubble snails, marine opisthobranch gastropod mollusks. Members of this worldwide clade appear to be the most primitive of the opisthobranchs.

Headshield slugs are the most morphologically diverse group of all opisthobranchs.

The vast majority possess a shell, although it may be reduced or internal. They have a well-developed headshield, a characteristic broadening at the head, which is used to plow beneath the surface of the sand. This headshield prevents the sand entering the mantle cavity. There is a muscular foot with or without parapodia (= fleshy winglike flaps).

Headshield slugs live just beneath the surface of the sand and can also be seen crawling on rocks. They have well-developed sensory structures to detect prey, which may be other opisthobranchs, polychaetes or bristleworms and foraminiferans. Several species are voracious carnivores.

Members of the brightly colored genus Chelidonura also have well-developed eyes on the anterior end of the head and bundles of sensory cilia around the mouth.



 

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