单词	siphuncle
释义	siphuncle /ˈsʌɪfʌŋk(ə)l / noun Zoology (In shelled cephalopods such as nautiloids and ammonoids) a calcareous tube containing living tissue running through all the shell chambers, serving to pump fluid out of vacant chambers in order to adjust buoyancy.The dorsal siphuncles of the Clymeniida tend to be larger than the ventral siphuncles of other ammonoid clades.... Outwardly indistinguishable from other ammonoids, clymeniids are distinguished internally by their dorsal siphuncle, contrasted to a ventral siphuncle in almost all other ammonoids. Given that the shell that covers the siphuncle is its only permeable surface, the interchange of fluids can take place only through this structure. Origin Mid 18th century: from Latin siphunculus 'small tube'.
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