|
Sacoglossa, commonly known as the sacoglossans or the "sap-sucking sea slugs",〔Anonymous. (Last changed: December 2008). ("Sap-sucking slugs" ). Accessed 12 January 2010.〕 are a clade of small sea slugs and sea snails, marine gastropod mollusks that belong to the clade Heterobranchia. Sacoglossans live by ingesting the cellular contents of algae, hence the adjective "sap-sucking". Some sacoglossans simply digest the fluid which they suck from the algae, but in some other species the slugs sequester and utilize within their own tissues living chloroplasts from the algae they eat, a very unusual phenomenon known as kleptoplasty, for the "stolen" plastids. This earns them the title of the "solar-powered sea slugs", and makes them unique among metazoan organisms, for otherwise kleptoplasty is known only among single-celled protists. The Sacoglossa are divided into two clades: the shelled families (Oxynoacea) and the shell-less families (Plakobranchacea). There are four families of shelled species: Cylindrobullidae, Volvatellidae, Oxynoidae and Juliidae, the bivalved gastropods. The shell-less Plakobranchacea are grouped in six families, divided between two clades ("superfamilies"), the Plakobranchoidea and the Limapontioidea. All saccoglossans are distinguished from related groups by the presence of a single row of teeth on the radula. The teeth are adapted for the suctorial feeding habits of the group. Kathe R. Jensen (2007)〔Jensen K. R. (November 2007). ("Biogeography of the Sacoglossa (Mollusca, Opisthobranchia)" ). ''Bonner zoologische Beiträge'' 55(2006)(3-4): 255–281.〕 recognized 284 valid species within the Sacoglossa. == Appearance == Many of these gastropods (e.g. ''Elysia spp.'') resemble winged slugs with a pair of cephalic tentacles. In photosynthetic members of the group, the wings, or parapodia, can be unfurled to maximise the area of the organism that is struck by sunlight.〔 In others (e.g. ''Placida spp.'') cylindrical cerata extend from the dorsal surface. The majority of saccoglossans are between one and three centimetres in length; they are typically uniform in color because of the chloroplasts they ingest which end up installed in their own cells.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Sacoglossa」の詳細全文を読む スポンサード リンク
|