siphuncle n. [Gr. dim. siphon, tube] 1. (ARTHRO: Insecta) see cornicle. 2. (MOLL: Cephalopoda) A tubular vascular extension borne at the apex of the visceral hump, that runs through the outer chambers of the nautiloid shell and secretes gas into them for buoyancy. siphunculate a.
Siphuncula, sipunculans, sipunculids n.; n.pls. [Gr. dim. siphon, tube] A phylum of bilaterally, unsegmented, cylindrical, deposit-feeding, benthic marine worms, with tentacles and mouth located at the anterior extremity of the introvert.
sistentes n. [L. sistere, to stop] (ARTHRO: Insecta) The first generation of apterous exules on the secondary host that give rise to the alate sexuparae and apterous progredientes in the genus Adelges.
sitopore n. [Gr. sitos, food; poros, pore] (ARTHRO: Insecta) The basal part of the cibarial floor of the hypopharynx of generalized chewing insects.
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