Gonostomum Sterki, 1878 (ref. ID; 2014)
Class Polyhymenophora: Subclass Spirotricha: Order Hypotrichida: Suborder Stichotrichina: Family Holostichidae (ref. ID; 2014)
Family Oxytrichidae Ehrenberg, 1838: Subfamily Oxytrichinae Jankowski, 1979 (ref. ID; 4894)

Synonym Plagiotricha Kent, 1882 (ref. ID; 2014, 4894) reported year? (ref. ID; 1618)

[ref. ID; 2014]
Flexible, elongate body, narrowing slightly anteriorly, dorso-ventrally flattened. 2 marginal rows of cirri and an oblique row of transverse cirri. The frontal cirri occur in 1 or 2 short, oblique rows which do not extend beyond the base of the peristome, plus several isolated cirri. Caudal cirri may or may not be present. AZM laterally placed and occupying the anterior body third. Macronucleus in several parts. Only a few 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; 2294]
A genus of hypotrich with a more or less flexible and elastic, but non-contractile body. The body shape is oval or elliptical, 60-150 um in length. The peristome area is confined to the lateral border and it posterior portion, in most cases, is abruptly bent towards the centre of the body. The AZM in the apical area is composed of long and thick membranelles. There are 3 distinct frontal cirri in the anterior region. Among the 6 to 20 ventral cirri present, one or two cirri are positioned just anterior of the transversals. No ventral cirri are present in the mid-ventral area. Two to four transverse cirri are present, which are not thickened in most species. There are two marginal cirral rows which are confluent posteriorly, or more correctly run posteriorly to meet several elongate caudal cirri. Dorsal cirri are not long enough to be seen from the ventral side of the body. Two oval macronuclei are present and a single micronucleus is situated near each of the macronuclei. A single contractile vacuole is situated just posterior of the end of the peristome area, at the left hand lateral border. The species belonging to this genus are found in salt water, fresh water and terrestrial soils. (ref. ID; 2294)

[ref. ID; 3640]
Gonostomum differs from the closely related Trachelostyla morphologically in body shape: the latter possesses "a narrow neck-like constriction in the anterior region". Otherwise, Trachelostyla resembles Gonostomum in that the porter's adoral zone of membranelles will be fully rebuilt during morphogenesis. Compared with the genus Kahliella, the ventral rows of Gonostomum seem to generate from five anlagen, and with no transverse and frontoterminal cirri in Kahliella, the two genera can be clearly separated. (ref. ID; 3640)

[ref. ID; 4894]
Improved characterization; Adoral zone of membranelles and undulating membranes in Gonostomum pattern. Frontoventral cirri in V-shaped pattern. Postoral ventral cirri right of adoral zone. Fewer than four transverse cirri. One right and one left row of marginal cirri. Three dorsal kineties. Caudal cirri present. Primary primordia. Dorsal morphogenesis in Gonostomum pattern. (ref. ID; 4894)
Remarks; Gonostomum is sometimes classified outside the oxytrichids, viz. in the Holostichidae (Corliss 1979; Tuffrau 1987) or Gonostomatidae (Small & Lynn 1985). However, ventral morphogenesis shows that Gonostomum evolved very likely from 18 FVT cirri oxytrichids (Borror 1972; Foissner 1982; Hemberger 1982; Song 1990; Tuffrau & Fleury 1994). In vivo easily distinguished from almost all genera (except the sister group Urosoma) of the oxytrichids by the distinctive shape of the adoral zone of membranelles and the widely spaced cilia of the paroral. These characters are strongly reminiscent of Kahliella and Wallackia (Berger & Foissner 1989), which have, however, many more cirral rows. The type species, Gonostomum affine, is the most common hypotrich in soil (Foissner 1987) (ref. ID; 4894)
Type species (original designation); Oxytricha affinis Stein, 1859 (ref. ID; 4894)


Gonostomum affine (Stein, 1859) Sterki, 1878 (ref. ID; 2294, 4861)
Syn; Gastrostyla affine Borror, 1972 (ref. ID; 2294); Gonostomum andoi Shibuya, 1929 (ref. ID; 2294); Oxytricha affinis Stein, 1859 (ref. ID; 2294); Plagiotricha affinis Kent, 1881-1882 (ref. ID; 2294); Stichochaeta affinis Gourret & Roeser, 1888 (ref. ID; 2294); Trachelstyla affine Buitkamp, 1977 (ref. ID; 2294)
Description; This free swimming species has been found in a variety of habitats including salt water, soil under leaf litter, moss and heathland. The body elongate and its anterior and posterior ends are narrowed and slightly pointed. Kent (1881-1882) described the body form as lanceolate. The peristome area is arcuate and is confined chiefly to the left lateral side, its posterior end bending inwards at the tip, terminating near the centre of the body. There are three frontal cirri in the anterior area and one buccal cirrus above the paroral membrane. According to Buitkamp (1977) there is one distinct frontal cirrus in the apical region, but Foissner (1982) in his detailed investigation found 3 frontal cirri as Stein (1859), Kent (1881-1882) and Kahl (1932) described. The ventral cirri number 8 to 13 in Stein's (1859) diagram, some of these making a slightly oblique row on the right side of the peristome. There are only 2 ventral cirri in the mid-ventral area, placed just in front of the transverse cirri. Three to five transverse cirri are present, whose length does not extend beyond the posterior end of the body in the original description. However, Kahl (1932), Wenzel (1953) and Foissner (1982) showed this animal having rather longer transverse cirri than those described by Stein (1859). Two marginal cirral rows are confluent posteriorly or terminate as a row of caudal cirri in some descriptions (Wenzel, 1953; Buitkamp, 1977). Two macronuclei are present. A contractile vacuole is situated just below the peristome. This animal was described by Stein (1859) and given the name Oxytricha affinis. Sterki (1878) noted the characteristic shape of the peristome are and the lack of mid-ventral cirri. In consequence he erected the new genus Gonostomum and transferred O. affinis to G. affine. Kent (1881-1882) pointed out that the name of Gonostomum closely resembled that of Gonostoma and Gonostomus which were already employed to designate certain genera of fish and molluscs. Consequently Kent appointed the new genus Plagiotricha which included P. affinis. Gourret & Roeser (1888) agreed with the action of Kent, but chose to transfer P. affinis to the genus Stichochaeta. Gonostomum andoi Shibuya, 1929 possesses a slightly different arrangement of cirri on the ventral surface from that of G. affine: that is, it displays a slightly higher number of frontoventral cirri and no cirri just anterior of transversals. But Kahl (1932) and Buitkamp (1977) showed the variation of form in G. affine especially the absence of ventral cirri just anterior of the transverse. Because other features of this organism resemble those of G. affine, we designate G. andoi as the synonym of G. affine. Kahl (1932) retained this organism as Gonostomum affine and gave Gonostomum andoi as its synonym. Borror (1972) transferred this organism to Gastrostyla affine because it possessed one oblique row of ventral cirri. However it is clear that this ventral cirral row in Gonostomum affine is not sufficiently developed to ensure removal to the genus Gastrostyla. Buitkamp (1977) proposed the new combination Trachelostyla affine, however Foissner (1982) retained this species in the genus Gonostomum. In agreement with Kahl (1932) and Foissner (1982), the confluence of the 2 marginal cirral rows (Stein, 1859), the possession of caudal cirri (Wenzel, 1953), the presence of two ventral cirri just anterior the transversals and 2 macronuclei are sufficient to retain this organism in the genus Gonostomum. (ref. ID; 2294)
Measurements; The length recorded by Kahl (1932) was 95-115 um, however those of Wenzel (1953) were measured as 63-125 um. (ref. ID; 2294)
Gonostomum algiocola Gellert, 1942 (ref. ID; 2294)
Syn; Trachelostyla affine Buitkamp, 1977 (ref. ID; 2294); Trachelostyla canadensis Buitkamp & Wilbert, 1974 (ref. ID; 2294)
Description; This species was found in association with green plants on rocks, feeding on flagellates. The body displays an oval or elliptical shape. The peristome area is confined to the left lateral border and the AZM extends backwards to nearly half the body length. A quarter of the peristome is bent inwards toward the body. In the frontal area 10 thick cirri are usually observed, including 3 frontal cirri and 1 buccal cirrus. Five ventral cirri make a slightly oblique row in the frontal region. Mid-ventral cirri are absent. Transverse cirri number two and there are two caudal cirri present. There are 15 left marginals and 18 right marginals. Two macro- and two micronuclei are present. These features are characteristic of the genus Gonostomum. Buitkamp and Wilbert (1974) isolated Trachelostyla canadensis from prairie soil in Canada. Buitkamp (1977) transferred this species to T. affine in his revision of the genus Trachelostyla. The presence of 3 frontal cirri, 1 buccal cirrus, 2 transverse cirri and 2 macronulei, also the lack of ventral cirri in the mid-ventral area indicate this species has a strong similarity to that of Gonostomum algicola although there are 2 caudal cirri instead 3 in G. algicola. These taxonomic features are clearly sufficient to designate this animal as the synonym of G. algicola. (ref. ID; 2294)
Measurements; The length has been recorded as 60-100 um. (ref. ID; 2294)
Gonostomum bryonicolum Gellert, 1956 (ref. ID; 2294, 2365)
See; Trachelostyla affine (ref. ID; 2365)
Syn; Trachelostyla affine Buitkamp, 1977 (ref. ID; 2294); Trachelostyla bryonicolum Borror, 1972 (ref. ID; 2294)
Description; The ciliate was found in the humus layer of soil samples and has been designated a detritus feeder, 60 um in length. The body is oval, cylindrical and peristome region is arcuate and confined chiefly to the left lateral border, consequently its posterior end bends abruptly inwards, terminating near the centre of the body where the buccal apparatus is situated. In the anterior region there are 3 distinct frontal and 4 ventral cirri, behind which are a separate pair of ventral cirri. One buccal cirrus is situated just above the anterior-most end of the paroral membrane. There is only one ventral cirrus in the midventral area, placed just in front of the four transverse cirri. Two marginal cirri rows terminate as a group of four caudal cirri at the posterior. Four cirral rows of long bristles on the dorsal side have been described. Two macronuclei are present together with one micronucleus, and one contractile vacuole is situated near the termination of the peristome. Borror (1972) and Buitkamp (1977) transferred this species to the genus Trachelostyla as T. bryonicolum and T. affine, respectively. The existence of caudal cirri and a ventral cirrus just anterior of the transversals, indicate that it should be retained in the genus Gonostomum as G. bryonicolum. (ref. ID; 2294)
Gonostomum ciliophorum Gellert, 1956 (ref. ID; 2294, 2365)
See; Trachelostyla affine (ref. ID; 2365)
Syn; Trachelostyla affine Buitkamp, 1977 (ref. ID; 2294); Trachelostyla ciliophorum Borror, 1972 (ref. ID; 2294)
Description; This species has been described as a bacteria and detritus feeder, and was found in the humus layer of soil. The body, 70 um in length, displays a slender and oval form. The peristome area is confined chiefly to the left lateral border, its posterior portion bending inwards into the body. The buccal apparatus is located at the posterior end of the AZM. Three distinct frontal, one buccal and seven ventral cirri are present on the right of the peristome. There are two ventral cirri in the posterioventral area placed just anterior of the transverse. There are four transverse cirri, two of which were longer than the others. Two marginal cirral rows are confluent posteriorly where no caudal cirri are situated. Two macronuclei with one micronucleus are present, one at the front and the other in the midventral area. Without detailed comments, Borror (1972) transferred this species to the genus Trachelostyla as T. ciliophorum and Buitkamp (1977) proposed the new combination Trachelostyla affine, again with scant information. Here it has been retained in the genus Gonostomum, as G. ciliophorum despite the revision of Borror (1972) and Buitkamp (1977) who clearly did not take into account the presence of confluent marginals and other diagnostic features. (ref. ID; 2294)
Gonostomum spirotrichoides Gellert, 1956 (ref. ID; 2294, 2365)
See; Trachelostyla affine (ref. ID; 2365)
Syn; Trachelostyla affine Buitkamp, 1977 (ref. ID; 2294); Trachelostyla spirotrichoides Borror, 1972 (ref. ID; 2294)
Description; This species has been found in soil under moss, feeding on bacteria and detritus. The body length is 110 um and its form is elongate and cylindrical. The peristome region is confined to the left lateral edge and extends backwards to nearly the centre of the body. The AZM comprises 27 membranelles of which 4 membranelles in the apical area are distinctly longer than others. The buccal opening is situated at the posterior extremity of the AZM, which displays a funnel like appearance. There are 3 distinct frontal cirri at the apex of the cell. Among the five ventral cirri present, three cirri are arranged in one oblique row extending from the right to the left of the body. It is not certain whether one cirrus which is situated below the end of this cirral row, is a buccal cirrus. Two isolated cirri are present at the region just below the majority of the ventrals and there is another pair of ventral cirri just in front of the 4 transversals. The number of right marginal cirri is 19, left marginal cirri number 15. Between the two marginal cirral rows there are four caudal cirri situated at the posterior. On the dorsal surface, three cirral rows of long bristles have been described. Two macronuclei with one micronucleus are present at the fronto- and midventral areas, respectively. A contractile vacuole is situated at the left of the posterior end of the AZM. Because of the possession of caudal cirri, the presence of two ventral cirri just anterior of the transversals and two macronuclei, Borror (1972) was clearly in error in attributing this animal to the genus Trachelostyla, as T. spirotrichoides. Buitkamp's (1977) designation of the new combination Trachelostyla affine is also incorrect. Based on the present study this species has been retained in the genus Gonostomum, as G. spirotrichoides. (ref. ID; 2294)
Gonostomum strenua (Engelmann, 1862) (ref. ID; 3640, 4896, 7423) or (Engelmann, 1862) Sterki, 1878 (ref. ID; 2294) reported author and year? (ref. ID; 191)
Syn; Oxytricha strenua Engelmann, 1862 (ref. ID; 2294); Plagiotricha strenua Kent, 1881-1882 (ref. ID; 2294); Stichochaeta strenua Gourret & Roeser, 1888 (ref. ID; 2294)
Description; This organism has a flexible and contractile form, the body being elongate and elliptical. It has been described from fresh water. Its anterior and posterior ends are evenly rounded. The frontal region is slightly thinner and dorsoventrally thicker than the posterior area. The peristome area is very narrow and confined to the left hand lateral edge, its posterior end being inwards, extending nearly to the centre of the body. The adoral zone of membranelles in the lateral area of the peristome is longer than that of Gonostomum affine. There are 23-25 frontoventral cirri, most of which form two slightly oblique rows, one row extending two thirds of the total body length, the other row being only half as long. No frontoventral cirri are present in front of the 4 transverse cirri. We assume that among the transverse cirri, possibly two can be counted as frontoventrals. The right and left marginal cirri were confluent posteriorly. At the posterior extremity there were 4 long, fine caudal cirri. Two macronuclei are present in the midventral area and one contractile vacuole is situated just below the peristome. Engelmann (1862) first described this organism under the name Oxytricha strenua. Sterki (1862) established the new genus Gonsotomum and transferred O. strenua to G. strenua on the same basis that O. affinis was transferred to G. affine. Kent (1881-1882) erected the new genus Plagiotricha and proposed P. strenua, and Gourret and Roeser (1888) transferred this organism to Stichochaeta strenua. Kahl (1932) and Stiller (1974) redescribed it as G. strenuum and G. strenua, respectively. Borror (1972) retained only G. strenua in the genus Gonostomum and adopted Oxytricha tricornis Milne, 1886-1887 as its synonym. After careful study of the original description and diagram of O. tricornis it is clear that it should be excluded from Gonostomum and from Oxytricha because of the unusual form taken by peristome. (ref. ID; 2294)
Body shape very similar to that of G. affine, in vivo about 90-120 x 25-50 um, ellipsoid with parallel margins, anterior end obviously pointed, posterior end rounded; dorsal-ventrally about 2:1 flattened. Subpellicular granules small, colorless and difficult to observe; which, after ejecting, appear to be spindle-like, about 1-1.5 um long and not impregnated with protargol. Cytoplasm colorless with numerous spherical fine inclusions. Contractile vacuole nearly at the level of the cytostome. Food vacuoles relatively large, very often containing green algae or bacteria. Movement moderately rapid, usually creeping, sometimes swimming freely with rotation around the long axis of the cell. Cysts have not been found. Two macronuclear segments with small spherical nucleoli, conspicuously separated lying longitudinally slightly left of the median. Micronuclei constantly located near the macronuclear segments. Adoral zone of membranelles about half of the body length, cilia of the membranelles 15-20 um. Buccal area relatively narrow, the short, simple organized endoral membrane about half as long as the paroral one, that is typically zig-zag-like. Three enlarged frontal cirri ca. 20 um long, occur closely behind the coronal membranelles and buccal cirrus near the anterior end of the paroral membrane. A short row of front-terminal cirri are at the upper right corner. There are also frontoventral cirri in three rows, obliquely arranged, with the 3rd one terminating usually under the level of the cytostome. Quite often five to six fine transverse cirri in two rows have their terminal lying between the margin rows. Occasionally, one to two separated cirri can be seen anterior to the transverse cirri. The anterior end of the right marginal row often extends onto the dorso-lateral surface anteriorly and its posterior end terminates in the transverse cirri. In contrast to the right one, the left marginal row is posterior end distinctly curved, extending to the cell's extreme end; and therefore is very difficult to distinguish from the caudal cirri. Dorsal cilia ca. 3 um long, are not evident in vivo in this population with constant three dorsal kineties. Each of the dorsal kineties has a terminal caudal cirrus that is relatively fine, and obviously longer than the other cirri (ca. 20 um), extending posteriorly almost to the ventral side. The infraciliature of G. strenua is only slightly different from that of the closely related species G. affine. (ref. ID; 3640)
European population. Size in vivo about 80-130 x 20-55 um, ellipsoid, with a pointed anterior end and a rounded posterior end. Contractile vacuole nearly at level of the cytostome. Extrusomes, after ejection, appear to be spindle-like, about 6 um long; sometimes they appear in silver carbonate impregnation. Food vacuoles filled with bacteria. Movement moderately rapid usually creeping, sometimes swimming with rotation around the long axis of cells. Buccal area relatively narrow. Paroral membrane is straight and typically zig-zag like. Endoral membrane about half as long as the paroral membrane and composed by pairs of kinetosomes. Adoral zone of membranelles about 50% of body length. Each membranelle is composed of four kineties: the two upper kineties are shorter, with 3-5 basal bodies and two longer ones with 16-14 basal bodies. The somatic ventral infraciliature shows three enlarged frontal cirri, one buccal cirrus near the anterior end of the paroral membrane, a short row of fronto-terminal cirri, three rows of frontoventral cirri, two rows marginal cirri, right and left, and four to five fine transverse cirri. The dorsal side has three dorsal kineties and each of the dorsal kineties has a terminal caudal cirrus. The number of dorsal dikinetids per kinety is 14-25. The nuclear apparatus is formed by two ellipsoid macronuclear segments, with one or more (2-5) micronuclei located near them. This ciliate may form spherical resting cysts, 40 um in diameter with a smooth wall cover. (ref. ID; 4896)
[Stomatogenesis]: The oral primordium originates apokinetally with the proliferation of basal bodies to form a narrow anarchic field. The oral primordium grows to a large field of loosely arranged basal bodies extending between the adoral zone of membranelles and the posterior end of the cell. Further kinetosomal proliferation and membranellar differentiation produce a new adoral zone of membranelles for the opisthe. The differentiation of membranelles proceeds posterior while the primordium for the undulating membrane separate as a group loosely arranged pairs of kinetosomes at the right side of the differentiating adoral zone of membranelles. The parental adoral zone of membranelles is retained. The anterior portions of the parental paroral and endoral membrane reorganize. (ref. ID; 4852)
[Development of the cirral primordia]: When the oral primordium from the opisthe starts to increase its size in the anterior area, there is a proliferation of the last cirri of the frontoterminal cirri, and a long oral primordium as anlage I appears to the left of the anlage II. There is also at the same time a disorganization of the buccal cirri and the first files of frontoventral cirri. Finally, a dedifferentiation on the third frontoventral line takes place. The final result is the development of six anlagen. In the further course of morphogenesis the primary primordium separate in such a way that finally a set of 6 anlagen each for proter and opisthe is formed. (ref. ID; 4852)
[Development of the somatic primordia]: The marginal primordia can be observed within marginal rows of both the porter and the opisthe. The cirri at the same place are already disorganized. At the same time each of the anlagen on the dorsal surface breaks up and migrates along the parental dorsal kineties forwards and backwards. The development of the dorsal infraciliature shows no special feature. (ref. ID; 4852)
Differentiation of new cirri: The segregation of the new cirri is the following: frontal cirri originate from anlage I, II and III; frontoterminal cirri from anlage VI; buccal cirri from anlage II; the frontoventral cirri from anlagen II, IV and V; and finally the transversal cirri from anlage V and VI (Song 1990). (ref. ID; 4852)
[Nuclear apparatus]: When cortical morphogenesis begins each macronuclear segment shows a replication band. The macronuclear fragments fuse. Later the macronucleus starts to elongate and finally divides in two fragments. Finally, a new division occurs and two macronucleus segments are formed, one for the proter and one for the opisthe. In general, the nuclear apparatus follows a divisional pattern like that of other hypotrichs possessing two macronuclear segments and two or more micronuclei. (ref. ID; 4852)
[Morphogenesis]: The morphogenetic processes are not shown in detail in the original study, but they are similar the processes in Paramphisiella caudata indicating long primary primordia for most ventral anlagen and a N3 anlagen development generating the two rightmost ventral rows five and six. This N3 anlage most likely originates from posterior cirri of row five and the oral primordium. (ref. ID; 7423)
Remarks; Slight morphologic differences have been found between the European population of G. strenua and the Asian population described by Song (1990). The most important are: 1) the number of micronuclei is 2-5 (median 4) in the European population instead of 2-3 (median 2) in the Asian population; 2) the number of transverse cirri is 4-6 (median 4) in the European population while 4-7 cirri (median 6) are present in the Asian population. The differences observed in cells size and macronucleus and in the diameter of micronuclei may be caused by the different methods used. However, a higher number of differences with respect to the Asian population described by Song (1990) has been found during the first stages of morphogenesis. The two main differences observed were: first, the dedifferentiation and proliferation of last cirrus of the frontoterminal cirri, and second that in the European population the five rows of basal bodies from the right anterior end of the oral primordium are neither formed nor migrated into anterior direction. The rest of the morphogenesis is similar to that described by Song (1990), and the morphogenesis in general is also very similar to that of G. affine described by Hemberger (1982). (ref. ID; 4852)
Measurements; The length recorded by Engelmann was 150 um. (ref. ID; 2294)
Gonostomum strenuum (Engelmann, 1862) (ref. ID; 1621) reported year? (ref. ID; 1618)
Description; Elongate; with caudal bristles; fresh water. (ref. ID; 1618)
Measurements; About 150 um long. (ref. ID; 1618)