Gastrostyla

Gastrostyla Engelmann, 1862 (ref. ID; 2014, 7307)

Class Polyhymenophora: Subclass Spirotricha: Order Hypotrichida: Suborder Sporadotrichina: Family Oxytrichidae (ref. ID; 2014)
Family Amphisiellidae Jankowski, 1979 (ref. ID; 7307)
Family Parakahliellidae Eigner, 1997 (ref. ID; 7423)

Synonym Nothopleurotricha Diesing, 1866 (ref. ID; 2014)

[ref. ID; 2014]
Inflexible, elongate, ellipsoidal body. 2 rows of marginal cirri joining posteriorly. The ventral cirri consist of an oblique row and a few isolated others. Frontal cirri are distinct with the 3 along the anterior margin larger than the others. Transverse cirri present but caudal cirri absent. AZM extends halfway down the body. 2 contractile vacuoles, one located on either margin. 2 macronuclei each with an adjacent micronucleus. Several species have been described.
Quote; Colin R. Curds, Michael A. Gates and David McL. Roberts "British and other freshwater ciliated protozoa Part II Ciliophora: Oligohymenophora and Polyhymenophora" Cambridge University Press, 1983 (ref. ID; 2014)

[ref. ID; 2129]
The oral primordium originates apokinetally near the transverse cirri. The ACR commences anlagen formation within-row and originates from three rightmost anlagen. Two dorsal kineties develop from the right marginal row. One or two postperistomial cirri originating from third anlage from right. One cirrus left of ACR. Transverse cirri obliquely arranged, originate from more than two anlagen. Caudal cirri present. (ref. ID; 2129)

[ref. ID; 7307]
The ACR originates from three rightmost anlagen. Two dorsal kineties develop from right marginal row. One or two postperistomial cirri originate from third anlage from right. One cirrus left of ACR. Transverse cirri obliquely arranged, originate from more than two anlagen. Caudal cirri present. Species assignable: G. steinii Engelmann, 1862 (description of morphogenesis in Walker & Grim, 1973 and in the Hemberger dissertation, 1982) (ref. ID; 7307)

Gastrostyla affine (Stein, 1859) Borror, 1972
See; Gonostomum affine (ref. ID; 2294), Trachelostyla affine (ref. ID; 2365)
Gastrostyla dorsicirrata Foissner, 1982 (ref. ID; 662 original paper)
Gastrostyla minima Hemberger, 1985 (ref. ID; 4697 original paper)
See; Gastrostyla mystacea (ref. ID; 4609)
Gastrostyla muscorum Kahl (ref. ID; 1618, 1621)
Gastrostyla mystacea (Stein, 1859) Sterki, 1878 (ref. ID; 4609) reported author and year? (ref. ID; 1629)
Syn; Gastrostyla minima Hemberger, 1985 (ref. ID; 4609); Oxytricha mystacea Stein, 1859 (ref. ID; 4609)
Gastrostyla pulchra (Perejaslawzewa, 1885) (ref. ID; 1621, 2112, 3119)
Gastrostyla setifera (Engelmann, 1861) (ref. ID; 1621)
Gastrostyla steinei (ref. ID; 4471)
Gastrostyla steini Engelmann, 1861 (ref. ID; 1621, 2245) or 1862 (ref. ID; 662) reported year? (ref. ID; 1219, 5624)
Gastrostyla steini Hemberger, 1982 (ref. ID; 4719)
Gastrostyla steinii Engelmann, 1862 (ref. ID; 4488, 4609, 7423) reported year? (ref. ID; 662, 1335, 1629, 4111) reported author and year? (ref. ID; 191, 7570)
Gastrostyla sterkii (ref. ID; 191)
Gastrostyla vorax (ref. ID; 191)

Gastrostyla muscorum Kahl (ref. ID; 1618, 1621)

Descriptions

Macronucleus in eight parts; fresh water in vegetation. (ref. ID; 1618)

Measurements

130-200 um long. (ref. ID; 1618)

Gastrostyla steini Engelmann, 1861 (ref. ID; 1621, 2245) or 1862 (ref. ID; 662) reported year? (ref. ID; 1219, 5624)

Descriptions

Body outline ellipsoid; dorsal surface convex; ventral side flattened; 6 frontal, 5 transversal cirri, right and left marginal cirri meet as a continuous row posteriorly, ventral form an oblique row; 4 macronuclei and 4 micronuclei; 1 contractile vacuole close to the left side in the posterior vicinity of the buccal area. (ref. ID; 1219)

Measurements

Length 150-320 um. (ref. ID; 1219)

Gastrostyla steinii Engelmann, 1862 (ref. ID; 4488, 4609, 7423) reported year? (ref. ID; 662, 1335, 1629, 4111) reported author and year? (ref. ID; 191, 7570)

Descriptions

Encystment-excystment: The encystment and excystment of Gastrostyla steinii was examined with light microscopy (Weyer 1930). Although vegetative organisms contain numerous refractile bodies, these bodies are seldom encountered in a cyst. Encysting organisms develop a clear cytoplasm, which appears devoid of refractile bodies. The cells presumably extrude the bodies either by means of 'regurgitation' or form a cytoproct, although a cytoproct region has not been observed by light or electron microscoy in this study. Later in encystment, the animals become ellipsoidal to spherical in shape, cease to swim, sink to the bottom of the culture dish and rotate. Subsequent to the rounding, the cells usually encyst within three to four hours. Treatment with 60% D2O enhances encystment, whereas the control cysts at 14 degrees C retarded encystmet. Usually within one to two hours after the cysts have been placed in excystment medium, pulsation of an excystment vacuole is initiated and continues for several hours. During this time the organism rotates freely within the endocyst until, presumably from hydrostatic pressure, the ectocyst ruptures and the organism escapes both the ectocyst and mesocyst. Continued excystment vacuole activity further enlarges the endocyst, and approximately two hours later, the organism is released following endocyst dissolution. Cells treated with 60% D2O excysted normally. Numerous encysted cells with various degrees of fusion between macronuclei are present in protargol-stained preparations. Unimacronucleate cysts prevail among the older cysts, which suggest that macronuclear fusion usually occurs during encystment. Micronuclear fusion was not noted. (ref. ID; 7570)
Resting cysts: The resting cysts of G. steinii are spherical, average 27-29 um in diameter, and are not unlike the cysts of Oxytricha fallax (Grimes 1973). The cyst wall averages 1.5-2.0 um in thickness and is composed of four, usually distinct, layers. The outer layer or ectocyst, is lamellar in cross-section, whereas the second and thickest layer (mesocyst), labelled the "zwischeraum" by Weyer (1930), appears to be composed of numerous individual fibers set down perpendicularly in close-packed alternating layers. The third and usually thinnest layer is the tightly packed fibrillar endocyst; and the inner-most or granular layer appears, in well-preserved specimens, to be composed of a coarse electron dense material. The highly modified cytoplasm of the resting cyst is cosiderably more dense than that of a trophic form. It exhibits occasional autophagic vacuoles, peripheral aggregations of mitochondria, and starch-like granules. The four macronuclei of the trophic form are fused in the mature cyst. The macronuclear chromatin is structured into dense, central aggregates and more loosely organized peripheral aggregates. Nucleoli appear rounded and completely devoid of the densely staining, ring-shaped structures characteristic of vegetative cell nucleoli. Encysted macronuclei show densely packed chromatin and a layered covering of membranous and amorphous material. (ref. ID; 7570)

Remarks

The anterior N1 anlagen-part is generated de novo, above the row five. (ref. ID; 7423)