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A tubelike structure in the body of a shelled cephalopod, such as a nautilus, extending through each chamber of the shell.

[Latin sīphunculus, diminutive of sīphō, sīphōn-, siphon; see siphon.]

si·phun′cu·lar (-kyə-lər), si·phun′cu·late (-lĭt) adj.
References in periodicals archive ?
Apterae are pale green, with a darker green spot on abdominal tergite 5 between the siphuncular bases.
This process neutralized the siphuncular defense system of the aphids, making predation easier (Toft 1995).