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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Trefusia

Trefusia De Man, 1893 (ref. ID; 3570, 7627)

Enoplida Filipjev, 1929: Family Trefusiidae Gerlach, 1966: Subfamily Trefusiiniae Gelach, 1966 (ref. ID; 3570)

Family Trefusiidae: Subfamily Trefusiinae (ref. ID; 7627)

ref. ID; 3570

Type species

Trefusia longicauda De Man, 1893 (ref. ID; 3570)
  1. Trefusia axonolaimoides Allgen, 1953 (ref. ID; 3570)
  2. Trefusia conica Gerlach, 1957 (ref. ID; 3570, 7627)
    See; Cytolaimium conicum (ref. ID; 3570)
  3. Trefusia cornea Gerlach, 1958 (ref. ID; 3570)
  4. Trefusia curvispiculosa Vincx & Vanreusel, 1989 (ref. ID; 1764 original paper)
  5. Trefusia filicauda Allgen, 1933 (ref. ID; 3570)
    Syn; Trefusia longispiculosa Bresslau & Stekhoven in Stekhoven, 1935 (ref. ID; 3570)
  6. Trefusia filum Stekhoven, 1942 (ref. ID; 3570)
  7. Trefusia helgolandica Riemann, 1966 (ref. ID; 3570)
  8. Trefusia litoralis (Allgen, 1932) (ref. ID; 1764) or (Allgen, 1932) De Coninck & Stekhoven, 1933 (ref. ID; 3570)
    Syn; Bognenia litoralis Allgen, 1932 (ref. ID; 3570)
  9. Trefusia longicauda De Man, 1893 (ref. ID; 3570)
  10. Trefusia longiseta Allgen, 1947 (ref. ID; 3570)
  11. Trefusia longispiculosa Bresslau & Stekhoven in Stekhoven, 1935
    See; Trefusia filicauda (ref. ID; 3570)
  12. Trefusia magna Filipjev, 1946 (ref. ID; 3570)
  13. Trefusia nidrosiensis Allgen, 1933 (ref. ID; 3570)
  14. Trefusia obtusicaudata Allgen, 1933 (ref. ID; 3570)
  15. Trefusia pseudolitoralis Vitiello, 1970 (ref. ID; 3570)
  16. Trefusia schiemeri Ott, 1977 (ref. ID; 7627 original paper)
    Syn; Triploides n. sp. Wieser et al. (ref. ID; 7627)
  17. Trefusia varians Gerlach, 1955 (ref. ID; 3570)
  18. Trefusia zostericola Allgen, 1933 (ref. ID; 3570)

Trefusia curvispiculosa Vincx & Vanreusel, 1989 (ref. ID; 1764 original paper)

Diagnosis

Trefusia curvispiculosa sp. nov. is characterized by the posterior position of the cephalic setae, the shape of the spicules and the filiform tail. (ref. ID; 1764)

Descriptions

Male: Body very long and slender with a rounded head end and a filiform tail with a rounded tip. Cuticle very faintly annulated; each annule about 0.5-1 µm broad. Three prominent lips are continuos with the remainder of the cervical region. The six internal labial sensilla are very thin and 2 µm long; the six external labial sensilla (17 µm long) are thick setae and consist of three segments. The dendritic processes are well pronounced and extend to the apical part of the jointed setae. The four cephalic setae (9 µm long) consist of two segments each and are situated posteriorly from the amphideal fovea. Numerous cervical setae (5-10 µm) are present and arranged into six longitudinal rows. No somatic setae on the remainder of the body. The amphideal fovea is ventrally wound, unispiral with an oval aperture; it is 9-10 µm wide (or 40-45% of the corresponding head diameter (= c.h.d.)) and its apical border is situated at 20 µm from the anterior end. Nine to twelve cervical, papilliform supplements are present; the first is situated at the level of the amphid and the last is situated at the level of the cardia. The buccal cavity is small, cyathiform without teeth and surrounded by the pharyngeal tissue. The pharynx is cylindrical and very muscular. Cardia 4 µm long and surrounded by intestinal cells. Nerve ring situated at 42-50% of the neck length. Ventral pore broad; outlet obviously sclerotized and situated anteriorly to the nerve ring. The ventral gland is very short and restricted to the pharyngeal region. Diorchic, with opposed outstretched testes ventrally from the intestine. Both testes are situated at the right of the vas deferens. Spicules with a characteristic shape: the shaft is curved anteriorly in its distal part; the capitulum is well developed and has a 10 µm long ventral protrusion; in some cases, two such ventral protrusions are present. Gubernaculum apparently lacking. The posterior part of the spicules is completely behind the cloaca. The functioning of the spicules is not well understood. The spicular musculature is well developed. Sperm cells amoeboid (6 µm in diameter) with and rod-shaped nucleus. Seven to thirteen preanal supplements present, resembling those in the pharyngeal region. Both groups of supplements consist of small papillae connected with small epidermal gland cells. Tail without seta, three caudal gland cells prominent. (ref. ID; 1764)

Trefusia litoralis (Allgen, 1932) (ref. ID; 1764) or (Allgen, 1932) De Coninck & Stekhoven, 1933 (ref. ID; 3570)

Synonym

Bognenia litoralis Allgen, 1932 (ref. ID; 3570)

Diagnosis

Riemann (1966) made a redescription of Trefusia litoralis on the basis of specimens from the German Bight of the North Sea. Reexamination of Riemann's specimens reveals that the differences with Vincx (1989) specimens are the number and position of the preanal papillae (only five to seven in the specimens from the German Bight) and the relatively length of the tail. The 15 preanal papillae of the Southern Bight specimens are more closely spaced so that the distance between the first and the last supplement is almost equal in the two morphotypes (107 µm for the Riemann specimens; 110 µm for Vincx specimens). Differences in the amount of preanal supplements between two morphotypes of the same species are also described by Vincx (1986) Neochromadora munita Lorenzen, 1972, Sabatieria celtica Southern, 1914 and S. punctata (Kreis, 1924). (ref. ID; 1764)

Descriptions

This species found sublittoral near shore. (ref. ID; 1764)
  • Male: Body slender and cylindrical. Head not set off; tail cylindrico-conical. Cuticle thin and very weakly annulated, from the level of the external labial setae to the tail tip. Head rounded, with three lips; the six internal labial sensilla are papilliform, the six external labial sensilla are thick setae (16 µm long) and consist of four articulating segments each. The apical segment is very short and pointed. The internal dendritic processes extend till the tip of the setae. The four cephalic setae are 6 µm long and consist of two artculating segments; they are situated at the level of or posterior to the amphideal fovea. Somatic setae irregularly distributed. Nine cervical, ventral papillae are present, four anterior and five posterior to the pore of the ventral gland; they are not evenly distributed. The amphideal fovea is ventrally wound, strongly cuticularized, conical to 'pouchlike' with a circular to oval 'apertura'. The variation in the structure of the amphideal fovea, which occupies about 26% of the corresponding head diameter, is probably due to the orientation of the observed specimens. The entrance of the receptor is always obvious. Buccal cavity very small, without teeth. The pharynx is cylindrical, slightly swollen in its terminal part and at the level of the buccal cavity; the pharynx extends to the lip region and surrounds the buccal cavity completely. Nerve ring not observed. The ventral pore is situated at 100 µm from the head end. The gland is short (40 µm long) and restricted to the pharyngeal region. Cardia very small. Intestinal tract with narrow lumen and thick wall cells; rectum 8.5 µm long. Diorchic, testes outstretched and opposed, situated ventrally from the intestinal tract. Posterior testis at the left side of the vas deferens. The sperm cells are hyaline oval structures, 2 µm long with a rod-shaped nucleus. Spicules paired and regularly curved, 24 µm long with cephalate proximal end. The spicules are provided with a very faintly sclerotized median stiffening piece. Fifteen small preanal supplements are present; the posterior ones are closer to each other than the anterior ones. The anteriormost supplement is situated at 110 µm from the cloacal opening. Tail without setae; three caudal glands prominent. (ref. ID; 1764)
  • Female: Didelphic, amphidelphic. with reflexed ovaries extending 515 µm posteriorly and 429 µm anteriorly in one female. The whole genital tract is situated at the right of the intestine. Both ovaries are reflexed to the left. Vulva simple, vagina 6 µm long; vaginal sphincter prominent; the dilatators of the vagina are also well developed. Uterus long with prominent wall cells, its proximal part filled with sperm cells. (ref. ID; 1764)

    Trefusia schiemeri Ott, 1977 (ref. ID; 7627 original paper)

    Synonym

    Triploides n. sp. Wieser et al. (ref. ID; 7627)

    Descriptions

    Body slender, cylindrical, head diameter 18-20 µm at the level of the articulated setae, diameter at the level of amphids 28-32 µm, at end of esophagus 30-45 µm, maximum body diameter in both sexes in midbody region, 40-48 µm, anal body diameter 37-42 µm in males, 30 µm in females. Cuticle thin, smooth, devoid of somatic setae, except for the cervical region. Head with 3 lips, 6 conical labial papillae, followed by a circle of 6 articulated setae, 11-13 µm (58-66% of c.b.m.) long with conspicuous nerve endings, at the level of the amphid a circle of 4 regular setae, 6-7 µm long (probably the cephalic setae), between 70 and 100 µm from the anterior end two circles of four cervical setae in submedian position, 5-6 µm long. Amphids pouchlike, with circular aperture, the latter 7.5-8 µm (26-28% of c.b.d.) in males, 4.5 µm (16%) in females wide. Stoma small, devoid of any armature, can be opened conically; esophagus long, 340-432 µm, with several plasmatic breaks in stomatal region, gradually widening from approximately 18 µm at the level of the amphid to 28 µm at its end; small cardia projecting into the intestine. Nerve ring and excretory system could not be observed. Tail for about 2/3 of its length conical, the last third more or less cylindrical tip slightly swollen, 5.5-6.2 anal body diameters long; three postanal caudal glands open through a simple spinneret terminally. Males diorchic, testes outstretched, opposed, anterior testis in anterior half of the body, posterior testis beginning at midbody or shortly thereafter; spicula stout, with a complicated cephalate proximal end, 53-55 µm (1.3-1.5 a.b.d.) long measured along arch, 45-51 µm (1.1-1.4 a.b.d.) measured along chord; no gubernaculum. The cloacal opening is large, round to elongated longitudinally so that in lateral view the male gonoduct in some specimen seems to open separately from the rectum (see also Riemann 1966, p.14). Females didelphic, gonades reflexed, extending 260-290 µm in both directions, oviducts long, thick walled, uteri continuous, short. Males bear rows of cervical and preanal papillae, which however are minute and their number and position extremely difficult to ascertain, especially since they only could be seen in lateral views. They all appear very close to the ventromedian line and the distinction of a true ventral and a subventral is rather arbitrary. Sometimes two papillae appear at about the same level but they never are exactly paired. In the holotype 8 such "pairs" could be found in the cervical region, the first of which appeared 53 µm from the anterior end. These "pairs" were followed by 7 single ventral papillae, the last of which was situated 90 µm anterior to the end of the esophagus. Preanally there is a cluster of 3 papillae 15-20 µm in front of the cloacal opening, a similar group 15 µm anteriad, then 1 single median papilla and about 10 irregular "pairs", 15-20 µm apart, the anteriormost about 200-220 µm in front of the anus. (ref. ID; 7627)

    Remarks

    The genus Trefusia De Man, 1893 as been carefully reviewed by Riemann (1966). However none of the diagnostic characters actually separates this genus from the remaining Trefusiidae, except maybe the amphid, which always seems to have an elongated fovea extending backwards, giving the amphid an oval to horse-shoe shaped outline. In all species of Cytolaimium Cobb 1920 and Rhabdocoma Cobb 1920 described so far the amphid appears circular with a double contour, the inner circle being obviously the aperture, the outer the outline of the fovea. Most of the species figured by Riemann (1966) also show the following characteristics not present in the above genera: the 6 articulated setae have blunt tips, like being cut off and are sometimes bifurcate (similar to Tripyloides) e.g. in T. conica Gerlach, 1957 (Riemann 1970, Fig.52) and T. filicauda Allgen, 1933 (Riemann 1966, p.6, Abb.2) (except for T. litoralis and the new species); the spicula have a characteristic handle shaped proximal end (except T. filicauda and T. litoralis). Characters which separate Trefusia from Cytolaimium are the presence of cervical papillae and the lack of both postanal papillae and cuticular plates under the preanal papillae in males; from Rhabdocoma the lack of the anterior female gonade in the latter genus. As a consequence, Trefusia conica Gerlach, 1957, which has been transferred to Cytolaimium Cobb in Gerlach and Riemann (1974) should return to Trefusia. Within the genus Trefusia the new species belongs to the group of species in which the subcephalic setae are on the level of the amphid. Within this group it is characterized by its medium sized tail (5.5-6 anal diameters). The tail in this species also does not appear to be as vulnerable as in most Trefusia species, because all specimen had uniform, complete tails. T. schiemeri appears to be close to T. litoralis in having more or less acute tips on the articulated setae and symmetrical amphids in adults. (ref. ID; 7627)

    Deposited materials

  • Holotype (male): U.S.N.M. Nr.54017 L: 2.385 mm, a: 53.0, b: 5.8-6.0 c: 9.8-10.4. (ref. ID; 7627)
  • Paratypes (male): U.S.N.M. Nr.54018-54019 L: 2.320-2.562 mm, a: 3-56.9 b: 5.8-6.0, c: 9.8-10.4. (ref. ID; 7627)
  • Paratypes (female): U.S.N.M. Nr.54020-54021 L: 1.83-2.68 mm a: 45.5-48.1, b: 5.3-6.4, c: 9.9-12.5. (ref. ID; 7627)