Trachelostyla Kahl, 1932 (ref. ID; 2014)
Class Polyhymenophora: Subclass Spirotricha: Order Hypotrichida: Suborder Stichotrichina: Family Holostichidae (ref. ID; 2014)

Synonym Gonostomum Maupas, 1883 pro parte (ref. ID; 2294); Stichochaeta Gourret & Roeser, 1888 pro parte (ref. ID; 2294); Stichochaeta Cohn, 1866 (ref. ID; 2014)

[ref. ID; 2014]
Long, narrow body sometimes with constricted, neck-like peristomial region. 2 rows of marginal cirri which are not confluent posteriorly. Without rows of ventral cirri. Isolated frontal cirri present, with the 3 most anterior being strongly developed. There may be 2 cirri just anterior to the transverse cirri. Some species may have caudal cirri. Contractile vacuole equatorial. AZM stretches a third to halfway down the length of the body. Macronucleus in two parts each with a micronucleus. Several species have been described.
Revision by Buitkamp (1977). Borror (1972) transferred several species from different genera into this genus. Jankowski (1978) transferred T. dibua Dragesco, 1954 into the new genus Cossothigma.
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 free swimming genus of hypotrich with a fragile and elastic, but non-contractile body, 130-190 um in length. This organisms possesses a narrow neck-like constriction in the anterior region. The peristome area is confined to the left lateral border, its posterior part bending abruptly and extending nearly to the centre of the body. Five to 10 frontventral cirri are present in the anterior region, but frontventral cirri in the mid- and posterioventral area are absent. Five or six transverse cirri are distinct in the posterior and form anterior oblique row. There are two marginal cirral rows which are not confluent posteriorly. No caudal cirri are present. Fine dorsal cirri can be observed from the ventral side. These appear to make two rows at the edge of the body and where these terminate at the posterior end some authors in earlier descriptions have clearly misinterpreted these as caudal cirri. Numerous macronuclei are dispersed throughout the body. This genus is found in marine habitats, and may be described as truly interstitial. (ref. ID; 2294)

Trachelostyla caudata Kahl, 1932 (ref. ID; 1621, 2117, 2294, 2316, 2365, 3119)
Description; This psammophilic species was reported to be common in the coastal areas of many European countries and Russia. Locomotion is similar to T. pediculiformis, but the 'head region' is not lifted from the substrate during forward movement. The body, 156 um in length, is fragile and elastic but not contractile. It is elongated and has a narrowed 'neck-like' anterior and a narrowed 'tail-like' posterior region. The form of the peristome area is similar to T. pediculiformis which is confined to the left lateral border of the 'head' area, and its posterior bends abruptly, extending backwards to near the centre of the body. Five long membranelles of the AZM are present at the apex of the cell, but the membranelles of the lateral portion are rather short and 'brush-like'. The characteristically long membrane which T. pediculiformis possesses in the buccal area is not present in this species. Among the four frontventral cirri, 3 make a row, but the forth cirrus from the apex is slightly separated from the other three. The length of these cirri is approximately the same as that of the marginal cirri. There are no frontventral cirri in the mid- and posterioventral area. Five thick transverse cirri are present, as Kahl (1932) described, these make a oblique row from the left to the right hand side. The right marginal cirral row starts from the base of the narrowed 'head' and the left marginal row begins just posterior of the end of the peristome. The two marginal rows terminate at the base of the transverse cirri. At both the right and left edges of the body, faint dorsal cilia are clearly displayed. These dorsal cilia of the right hand edge run from the top of the apical area, and join the other dorsal row of cilia of the left hand side at the posterior end of the body. Dorsal cilia or cirri are not as long as those of T. pediculiformis and do not extend to any great length in the caudal area. There are 8-10 dorsal cirral rows according to Kahl (1932). A contractile vacuole is situated just posterior of the peristome end. In Kahl's (1932) diagram, 11 macronuclei are shown. This animal was originally found in the sands of Kiel by Kahl (1932). In agreement with both Borror (1972) and Buitkamp (1977) this organism has been retained in the genus Trachelostyla. (ref. ID; 2294)
Elongated body, 145 um long, characteristically attenuated to form a 'neck' like region. Buccal cavity forms a short groove extending one quarter of the length of the body. Five long transverse cirri observed with four or five frontals. (ref. ID; 2316)
Trachelostyla pediculiformis (Cohn, 1866) (ref. ID; 3119) or (Cohn, 1866) Kahl, 1932 (ref. ID; 1335, 1621, 2117, 2294, 2316, 2365, 3388) reported author and year? (ref. ID; 191)
Syn; Gonostomum ped Maupas, 1883 (ref. ID; 1621); Gonostomum pediculiforme Maupas, 1883 (ref. ID; 2294, 2365); Stichochaeta corsica Gourret & Roeser, 1887 (ref. ID; 2365) or 1888 (ref. ID; 2294); Stichochaeta pediculiformis Cohn, 1866 (ref. ID; 2294, 2365)
Description; This highly psammophilic species has been commonly encountered in many coastal areas of Europe, Russia, North and South America and the Sea of Japan. The body is characteristically flexible. Its locomotion as well as its body shape is distinct enough to distinguish it from other ciliates, frequently moving forward and backward and repeatedly raising the 'head' region above the substance, constantly searching between the sand grains. The body is elongate, 136-196 um in length. The anterior region, which comprises one-third of entire body length, is attenuated and produced as a narrower neck-like process. The posterior end is rounded in this species. The peristome area is confined to the left lateral border of the anterior region for most of its length. The posterior quarter of peristome area is bent inwards, and eventually extends to near the centre of the body. The buccal opening is situated at the 'shoulder-like' ridge at the base of the 'neck' region. There are five long membranelles of the AZM at the anterior extremity. A bundle of several long cilia-like membranelles are clearly seen in the buccal area which is entirely consistent with Cohn's (1866) published diagram. The very thin, membrane-like dorsal edge of the peristome extends for half the total length of the AZM on the left side. These are transparent and easily overlooked. The anterior area displays three frontal and seven ventral cirri. Maupas (1883), Kahl (1932) and Borror (1972) indicated the number of these cirri as 8, 11 and 11, respectively, including three distinct frontal cirri. There are no ventral cirri in the middle and posterior of the body as Kahl (1932) described. However in the description Maupas (1883) and Borror (1972) two ventral cirri just anterior of transverse cirri were present. Five or sometimes six transverse cirri make an oblique row from the left hand to the right hand side of the body. The right marginal cirral row starts from the 'shoulder' adjacent to the apical area and left row runs from just below the buccal region. These two marginal rows are not confluent posteriorly and terminate at the base of the transverse cirri. At both lateral edges rows of very fine and long cilia can be observed, they are particularly long in the posterior region. Maupas (1883) designated these long cilia at the posterior end as caudal cirri, however Kahl (1932) found them projecting from the dorsal surface of the body: that is to say these thread-like cilia of the lateral and posterior are bristles originating from the dorsal side. Cohn (1866) found this species and appointed the name Stichochaeta pediculiformis. Maupas (1883) also described these organism and transferred it to the genus Gonostomum as G. pediculiforme because he found it had quite different morphological features in the peristome area, and cirral arrangements from the genus Stichochaeta of Claparede & Lachmann (1858), Kahl redescribed G. pediculiforme in 1928. However, he erected the new genus Trachelostyla in 1932 giving the reason that the organism had a 'neck-forming' narrowed peristome area and its two marginal cirral rows were not confluent at posterior end of the body. He included two species in this genus, T. pediculiformis and T. caudata. Borror (1972) and Butikamp (1977) agreed with Kahl (1932) and placed Gonostomum pediculiforme and Stichochaeta pediculiformis as synonyms of T. pediculiformis. In agreement with Kahl (1932), Borror (1972) and Buitkamp (1977), the possession of narrowed 'head' area, clearly defined transverse cirri, the non-convergent marginal cirral rows posteriorly and the absence of caudal cirri are sufficient reason to retain this species in the genus Trachelostyla Gourret & Roeser (1888) described Stichochaeta corsica as having serried rows of adoral 'cirri', long and fine caudal 'cilia', dorsal 'cilia' and transverse cirri. Careful analysis of their description and diagram reveals the long and fine cilia at the posterior extremity of the body are in reality dorsal bristles, not caudal cirri. From a detailed survey of morphological features it is clear that S. corsica must be considered a synonym of T. pediculiformis. (ref. ID; 2294)
Measurements; Mean length recorded 120 um. (ref. ID; 2316)