siphuncle
/ˈsaɪfʌŋkl/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【动】（有壳软体动物头足纲的）通管, 室管, 体管。
词源
mid 18th cent.: from Latin siphunculus 'small tube'.