Dileptus Dujardin, 1841 (ref. ID; 2013, 4861)
Class Kinetofragminophora: Subclass Gymnostomata: Order Haptorida: Family Tracheliidae (ref. ID; 2013)

See Paradileptus, Pelagodileptus

[ref. ID; 2013]
Body shape highly elongate, size ranges 100-1,600 um long, rounded in cross-section, with long highly mobile, contractile prehensile anterior neck region. Ventral surface of neck lined with trichocysts. Some species have a pointed tail region, others are rounded posteriorly. At the base of neck lies the oral aperture which is supported by a cytopharyngeal basket of trichites (not always easily visible). The neck is often held extended, bent towards the dorsal surface. Trichocysts commonly present in cytoplasm and particularly down the unciliated ridge of the neck. Ciliation complete, in form of longitudinal kineties. Contractile vacuoles usually numerous in row along dorsal surface often with large terminal vacuole. Contractile vacuoles rarely on both dorsal and ventral surfaces. Macronucleus highly variable from species to species but usually in 2 to many parts which may be distributed throughout the cytoplasm or may be moniliform, rarely single but when so is elongate. Originally described by Dujardin (1841).
Quote; Colin R. Curds "British and other freshwater ciliated protozoa Part I Ciliophora: Kinetofragminophora" Cambridge University Press, 1982 (ref. ID; 2013)

[ref. ID; 4861]
Recent investigations showed that the genus Dileptus is polyphyletic: D. amphileptoides apparently lacks a usual pharyngeal apparatus (Foissner 1984) and D. monilatus lacks oblique preoral kineties (Foissner et al. 1995). In fact, years ago these species were chosen by Jankowski (1967) as types for two new subgenera of Dileptus (with many macronuclear nodules), viz. Dimacrocaryon (with two macronuclear nodules) and Monilicaryon (with moniliforme macronuclear), using their macronuclear configurations as sole diagnostic charcter; an unfortunate action because the same macronuclear pattern very likely evolved independently in several evolutionary lines of Dileptus s. l. Foissner (1984) thus amended Jankowski's diagnosis of Dimacrocaryon and suggested uniting binucleate species with a normal oral apparatus in a new genus, Rimaleptus. However, he did not appreciate this genus for the reason mentioned above. Further studies are necessary to elucidate whether or not the macronuclear of configuration can be used to split the genus according to its evolutionary wheer or not the macronuclear configuration can be used to split the genus according to this evolutionary history. For the present, it seems wise to keep all species which possess a usual infraciliature in the time-honoured genus Dilpetus. The somatic and oral infaciliature of most Dileptus species is very similar, except for the new species mentioned above and possibly some others. Thus, the classical species characters (size, shape, length of proboscis, nuclear apparatus, number and location of contractile vacuoles, biotope) used by Kahl (1931) and Dragesco (1963) are still valid. However, I would like to add another highly useful character, viz. the extrusomes which show a bewildering, yet hitherto unrecognized diversity in size, shape and arrangement (Song Weibo et al. 1988, present results and data from about 10 new terrestrial species not yet published). Usually these organelles do not stain with protargol and their shape is more or less altered by various fixatives. Thus, size, shape and arrangement of the extrusomes must be studied in live cells. (ref. ID; 4861)

Dileptus americanus Kahl, 1931 (ref. ID; 4861) reported year? (ref. ID; 1618, 1622)
Description; Proboscis bent dorsally sickle-like; macronucleus made up of 2 sausage-shaped or often horseshoe-shaped parts; 2 contractile vacuoles on dorsal side; in mosses. (ref. ID; 1618)
Measurements; 200 um long. (ref. ID; 1618)
Dileptus anser (O.F. Muller, 1786) (ref. ID; 1219, 1335, 1622, 2245, 2571, 3115, 3593, 4683) reported year? (ref. ID; 1618, 3698) reported author and year? (ref. ID; 3292, 4612, 4686, 7596)
Syn; Amphileptus anser Ehrenberg, 1838 (ref. ID; 3115); Amphileptus cygnus Claparede & Lachmann, 1859 (ref. ID; 4683); Amphileptus margaritifer Ehrenberg, 1838 (ref. ID; 3115); Dileptus gigas f. grojecensis Wrzesniowsky, 1870 (ref. ID; 4683); Dileptus gigas f. varsaviensis Wrzes., 1870 (ref. ID; 1622); Dileptus irregularis Maskell, 1888 (ref. ID; 1622); Vibrio anser O.F. Muller, 1786 (ref. ID; 4683)
Description; Slender with neck-like elongated proboscis at the anterior end which is slightly flattened and highly contractile; cytopharynx exhibiting long trichocysts; uniform ciliation all over the body, 2 rows of strong cilia and 3 rows of trichocysts along the ventral side of the proboscis; macronucleus divided into 200-500 small bodies; about 20 micronuclei; numerous contractile vacuoles along the dorsal side. (ref. ID; 1219)
Proboscis slightly flattened; macronucleus divided into 100 or more discoid bodies; sixteen or more vesicular micronuclei; contractile vacuoles in row on the aboral surface, with two to three in proboscis; in fresh water. (ref. ID; 1618)
Measurements; Length 200-600 um, average about 350 um. (ref. ID; 1219)
250-400 um, sometimes up to 600 um long. (ref. ID; 1618)
Dileptus costaricanus Foissner, 1995 (ref. ID; 4861 original paper)
Diagnosis; In vivo about 230-330 x 40 um, proboscis 30% of body length on average, posterior body end narrowly rounded to slightly pointed. Many macronuclear nodules. One row of contractile vacuoles each on dorsal and ventral side. Extrusomes conspicuous, thorn-shaped, not only in proboscis but also in single row around pharyngeal opening. (ref. ID; 4861)
Description; Shape blunt because proboscis rather wide and short and trunk not tailed; posterior end rounded in specimens collected from young raw culture, pointed in most cells found in old culture; postoral portion cylindroid, proboscis flattened leaf-like. Macronuclear nodules highly variable in shape and size, globular to ellipsoid, with few to many nucleoli, irregularly distributed throughout cell, difficult to count because narrowly spaced and of similar size as cytoplasmic inclusions; about 150-500 nodules seem common. Many globular micronuclei. Contractile vacuoles each with single excretory pore, dorsal row extends to anterior half of proboscis, ventral row commences near pharyngeal opening; pores not in single line but in narrow band in and between different kineties. Extrusomes of proboscis 5-7 x 1 um, distinctly curved, thorn- to club-shaped; those around inner pharyngeal wall 3 x 1 um, only slightly curved, drop-shaped, oriented perpendicularly to pharynx surface with thick end distally producing very conspicuous ring; both size types occur also in cytoplasm and do not stain with protargol. Pellicle and cytoplasm colourless. About 5 rows each of 1 x 0.5 um sized cortical granules between somatic kineties. Cytoplasm usually packed with 3-8 um sized fat globules. Food vacuoles with indiscernible content, possibly ciliates. Somatic and oral infraciliature without peculiarities, i.e. as in other well-investigated, large-sized species of genus (Foissner 1984, 1989; Golinska 1971). However, the dorsal brush will be described at some length because few detailed data are available. Paired dorsal brush cilia 2-3 um long and inflated, unpaired bristles 1-2 um long and rod-shaped. Brush formed by anterior portion of about 5 left lateral somatic kineties, except of those ending near pharyngeal opening and thus producing small, non-ciliated field along preoral kineties; brush kineties successively shortened forming remarkable pattern where 3 rows each of paired cilia extend for short distances in step-like manner side by side, giving impression of three-rowed dorsal brush; some unpaired bristles posterior of each row of paired cilia, often some unpaired basal bodies at anterior end of brush kineties. Pharyngeal opening small compared to size of cell, about 10 um in diameter, pharyngeal fibres inconspicuous. (ref. ID; 4861)
Comparison with related species; D. costaricanus differs from all multinucleate congeners by the shape and arrangement of the massive extrusomes (toxicysts); however, these character are difficult to rate because detailed date are lacking in most species. In C. margaritifer and D. mucronatus, two other large-sized species, the extrusomes are rod-shaped (Foissner 1984; Foissner et al. 1995); those of D. beersi are slightly thorn-shaped, but this information is based on mercuric chloride fixed specimens (Jones 1956). Possibly, most multinucleate Dileptus species have simple, i.e. rod-shaped extrusomes. A unique character of D. costaricanus is its ring of knotty extrusomes around the pharyngeal opening. Only two other multinucleate Dileptus species possess ventral contractile vacuoles, viz. D. anatinus Golinska 1971 (length more than 500 um; posterior end with short tail; extrusomes rod-shaped; Foissner et al. 1995) and D. dubius Vuxanovici, 1959 (described from single, 116 um long specimens found in a lake in Romania; extrusomes short and delicate; only one contractile vacuole underneath pharyngeal opening). (ref. ID; 4861)
Derivatio nominis; Named after the country (Costa Rica) where it was discovered. (ref. ID; 4861)
Type locality; Upper soil layer near the ranch house "La Casona" in the Santa Rosa National Park, Costa Rica, W 85 degrees 38', N 10 degrees 50'. (ref. ID; 4861)
Type specimens deposited; Slides with type and voucher specimens have been deposited in the Oberosterreichische Landesmuseum in Linz (LI), Austria. Relevant specimens are marked by a black ink circle on the cover glass. (ref. ID; 4861)
Dileptus monilatus (Stokes, 1886) (ref. ID; 1622, 1896) reported year? (ref. ID; 1618) or (Stokes, 1886) Kahl, 1931 (ref. ID; 4612)
See; Monilicaryon monilatus (ref. ID; 4612)
Description; Resembles D. anser, but the macronucleus moniliform. (ref. ID; 1618)
Dileptus similis Foissner, 1995 (ref. ID; 4861 original paper)
Diagnosis; In vivo about 200-300 x 60 um, proboscis 50% of body length on average, posterior body end broadly rounded. 2 macronuclear segments with micronucleus interposed. Single dorsal row of contractile vacuoles. Two size-types of rod-shaped extrusomes. (ref. ID; 4861)
Description; Shape blunt because length/width proportion rather narrow, viz. 3:1 to 5:1; postoral body portion cylindroid, proboscis very flexible, distinctly flattened, sickle-shaped, conspicuously widened near pharyngeal opening. Macronulear segments in centre of trunk, sausage-shaped, often side by side or one upon the other, contain many small nucleoli. About 6-8 contractile vacuoles each with several excretory pores, uppermost vacuole in proximal half of proboscis, posteriormost vacuole enlarged and slightly above cytopyge. Both types of extrusomes in proboscis and cytoplasm; large type 8-10 x 1 um in size and slightly fusiform, small type about 3 um long, delicate and rod-shaped. Pellicle and cytoplasm colourless. About 6 rows each of 0.8 um sized cortical granules between somatic kineties. Feeds on other ciliates, e.g. Frontonia depressa, which are ingested whole and digested in large food vacuoles. Somatic and oral infraciliature as described in D. costaricanus and D. conspicuus (Foissner 1989). However, both sides of proboscis have rather large field without cilia, that on left side larger than that on right. Paired dorsal brush cilia only 1-2 um long, rod-shaped, arranged as described in D. costaricanus. Pharyngeal opening large, viz. about 25 um in diameter; pharyngeal fibres delicate but numerous forming distinct outer and inner basket. (ref. ID; 4861)
Comparison with related species; D. similis resembles several other species as concern size, nuclear apparatus and contractile vacuoles, viz. D. robustus Vuxanovici, 1959 (a poorly described limnetic species with symbiotic algae), D. orientalis Song Weibo et al., 1988 (a terrestrial species with small, lemon-shaped extrusomes), and D. mucronatus Penard, 1922 (a freshwater and soil species with distinct tail). The similarities between D. similis and D. mucronatus are obviously considerable, and it thus cannot be excluded that the new species is an untailed, blunt ecotype of D. mucronatus. On the other hand, D. mucronatus, as redescribed by Foissner (1984), is much more slender (9:1) than D. similis (4:1), whose shape and infraciliature thus resemble D. conspicuus (redescribed in Foissner 1989). On superficial observation, D. similis is easily confused with D. terrenus Foissner, 1981 which, however, has a distinct tail and a single sausage-shaped macronucleus. Another, less similar terrestrial species is D. americanus Kahl, 1931 which is smaller (up to 200 um) and has only 2 contractile vacuoles. (ref. ID; 4861)
Derivatio nominis; The epithet refers to its similarity with D. mucronatus. (ref. ID; 4861)
Type locality; Upper soil layer near the ranch house "La Casona" in the Santa Rosa National Park, Costa Rica, W 85 degrees 38', N 10 degrees 50'. (ref. ID; 4861)
Type specimens deposited; Slides with type and voucher specimens have been deposited in the Oberosterreichische Landesmuseum in Linz (LI), Austria. Relevant specimens are marked by a black ink circle on the cover glass. (ref. ID; 4861)