Sutural sinus see jugal sinus

sutural slope (MOLL: Gastropoda) An angle between the suture and plane perpendicular to the axis; sometimes equated to the sutural angle.

suture n. [L. sutura, seam] 1. Line of junction of 2 parts generally immovably connected. 2. (ARTHRO: Crustacea) In Cirripedia, a line or seam at the juncture of two compart-mental plates; weakly calcified areas of the integument for separation at ecdysis. 3. (ARTHRO: Insecta) Grooves marking the line of fusion of two former plates; a narrow membranous area between sclerites; line of juncture of elytra in Coleoptera. 4. (MOLL: Gastropoda) The continuous spiral line on the shell surface where whorls adjoin. sutural a.

swarming n. [A.S. swearm, swarm] (ARTHRO: Insecta) In social insects: a. The departure of a queen and workers from the parental nest to establish a new colony of highly euso-cial bees. b. In ants and termites, often applied to the mass departure of reproductive forms from the nests at the beginning of the nuptial flight.

swimmeret n. [A.S. swimman, to swim] (ARTHRO: Crustacea) An abdominal appendage functioning as a swimming organ; pleopod.

swimming bell (CNID) Any bell or umbrella-shaped cnidarian that moves through the water by contractions, especially Siphonophora; nectocalyx; nectophore.

swimming plate (CTENO) A short ridge bearing large fused cilia, arranged in eight meridional rows that function in locomotion.

switch gene The gene influencing the epigenotype to switch to a different developmental pathway.

sycon n. [Gr. sykon, fig] (PORIF) A sponge in which the choa-nocyte layer shows folding accompanied by superficial thickening of the mesohyl.

sylleibid n. [Gr. syllektos, gathered together] (PORIF) An aquiferous system transitional between syconoid and leucon-oid conditions, with elongate choanocyte chambers grouped around a common exhalant channel.

sylvan, silvan a. [L. sylva, silva, forest] Pertaining to or inhabiting the forests or woodland areas.

sylvatic, silvatic a. [L. sylva, silva, forest] In disease ecology, a parasite existing normally in the wild and not in the human environment. see synanthropism.

symbiology n. [Gr. symbiosis, life together; logos, discourse] The study of symbioses.

symbion(t) n. [Gr. symbiosis, life together; on, being] Any organism that exists in a relationship of mutual benefit with another organism; a symbiote.

symbiosis n. [Gr. symbiosis, life together] 1. The mutually beneficial living together of individuals of two different species. 2. Interrelationship of different species of organisms, ranging from beneficial, to neutral, to dehabilitating. symbiotic a. see mutualism, commensalism, parasitism.

symbiote n. [Gr. symbiosis, life together] An organism living in symbiosis; symbiont.

symmetry n. [Gr. symmetria, due proportion] The mode of body organization. symmetical a. see bilateral symmetry, radial symmetry.

sympathetic system 1. That portion of the autonomic nervous system directly connected with the brain and innervating the fore and middle intestine, heart and certain other parts. 2. (ARTHRO: Insecta) see stomogastric nervous system, ventral sympathetic nervous system.

sympatric hybridization The production of hybrid individuals between two sympatric species.

sympatric speciation Speciation with geographic isolation; the reproductive isolation occurring between segments of a single population.

sympatry n. [Gr. syn, together; patria, native country] The occurrence of two or more populations in the same area; usually referring to areas of overlap in species distributions.

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