Sorogena stoianovitchae

Ciliates that form collections of spores on aerial stalks, actively swimming cells (theronts) about 30-40 x 20-30 microns, feeding trophonts 40-75 x 30-55 microns. More or less reniform, ventral side sigmoid and often slightly indented at contractile vacuole, dorsal side convex. Both ends usually broadly rounded, rarely tapered. Anteriorly, left of median (when seen right laterally), a small, hyaline dome with entrance to cytostome at centre. Theronts slightly to markedly (2:1) flattened laterally and slightly curved in ventral view. Trophonts not or inconspicuously flattened. Nuclear apparatus approximately in centre of cell. Macronucleus spherical to slightly eltipsoid, with 'small nucleoli. Single micronucleus (2-4 x 2-3 microns) in macronuclear indentation. Contractile vacuole subterminal, surrounded by many small vesicles; single excretory pore. Cortex distinctly furrowed by somatic kineties, very flexible, cells compressed by coverslip exhibit amoeboid movement. Many mucocysts 1-2 x 0.5-1 microns in size, may be responsible for silvery refractile appearance of live cells. Mucocysts released when methyl green-pyronin is added and form a coat around cell. Cytoplasm of theronts clear without remarkable inclusions. Trophonts contain numerous food vacuoles, but no food reserves. Posteriorly often a large, brownish defecation vacuole with granular content. Feeding very similar to Woodruffides metabolicus; mouth opens widely to cover prey. Usually entire Colpoda cells are drawn in, as many as 5 observed within single predatory cells. Swims by rotation about longitudinal axis, may creep on bottom of culture dish. Cilia about 8 microns long, mostly paired, probably some single in posterior portion of cell. 18-20 somatic kineties, distinctly right spiralling, spaced almost equidistantly, more densely ciliated in anterior half and at right side than in posterior half and at left side. All kineties converge at oral dome, some of right and ventral side shortened posteriorly, terminating near excretory pore of contractile vacuole and cytopyge. Some scattered, distinctly shortened kineties hardly reaching posterior half of cell. Slight dorsal shoulder or hump tilts oral apparatus ventrally. Oral aperture surrounded by non-ciliated lip, the oral dome, which projects 1-3 microns forward. Oral dome more pronounced in theronts than trophonts and sole character distinguishing Sorogena from Platyophrya in vivo. Paroral membrane at right base of oral dome, semicircular, consists of 21-29 ciliated dikinetids; cilia about 5 microns long. At left base of oral dome 3-5 (mostly 4) adoral organelles usually consisting of 2 long rows with 3 basal bodies each and 1 short row with 2 basal bodies; short row sometimes lacking or reduced to 1 basal body; about half adoral basal bodies barren. Cytopharynx supported by long microtubules extending from paroral dikinetids over oral dome and by nematodesmata originating from anterior basal bodies of somatic kineties, from paroral dikinetids and probably from adoral organelles. Forms cysts on a stalked sorocarp. Resting cysts 23-55 microns in diameter, ectocyst smooth. Infraciliature very likely retained. Cysts with immobile content from sorocarps show normal infraciliature when rehydrated for 1 hour. Mature resting cysts fail to impregnate with silver, probably due to thick ectocyst. Sorocarps with furrowed, tapered stalk, 293-1121 microns tall. Sori (structures with spores) 98-488 microns in diameter, contain as many as several hundred sorocysts 18-32 microns in diameter. Sorocarps occasionally minute with as few as 4 sorocysts. Stalk non-cellular, composed of fibrillar matrix of complex protein-polysaccharide molecules. Stalk material produced by mucocysts and other specific vesicles appearing during aggregation, secreted as compact clump or clumps of material which expands during hydration. Expanded stalk material initially viscous, soon solidifying through dehydration or cross-linking to form sheath which provides structural support and controls expansion of newly secreted stalk material. Sorogenic cell continues to secrete stalk material which expands once outside cell; resultant force is directed upward by sheath, thereby moving cells further above surface.