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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Eothinia

Eothinia Harring & Myers, 1922 (ref. ID; 1345) or 1924 (ref. ID; 3688)

ref. ID; 1663

With three eyespots. Both unci with one main tooth and accessory teeth. Littoral species. (ref. ID; 1663)

ref. ID; 1923

Inner margin of both rami finely toothed, symmetric. (ref. ID; 1923)

ref. ID; 3245

Notommatid rotifers with moderately elongate, fusiform, illoricate body, a distinct neck segment separating head and abdomen; the tail is moderately large or rudimentary, the foot two-jointed and short; the toes are rather short. The corona is obliquely frontal and may have a ventral chin; the marginal cilia are fairly short except on two lateral auricle-like areas. The mastax is virgate, but somewhat specialized; the inner edges of the rami are provided with numerous short closely spaced, needlelike teeth; the piston is well developed. The retrocerebral organ is well developed; both sac and glands are present; there is a cervical eyespot at the posterior end of the ganglion and two frontal eyespots on the apical plate. (ref. ID; 3245)
  1. Eothinia argus Harring & Myers, 1924 (ref. ID; 2017, 3245 original paper)
  2. Eothinia carogaensis Myers, 1937 (ref. ID; 1345, 2017)
  3. Eothinia elongata (Ehrenberg, 1832) (ref. ID; 1345, 1923, 2017, 3688) reported year? (ref. ID; 2933)
    Syn; Eosphora elongata Ehrenberg, 1832 (ref. ID; 1345, 2017, 3688); Eosphora striata Glascott, 1893 (ref. ID; 1345, 3688); Eothinia elongata Harring & Myers, 1922 (ref. ID; 2017, 3688); Eothinia elongata macra Berzins, 1949 (ref. ID; 2017); Eothinia lamellata Berzins, 1949 (ref. ID; 2017); Notommata elongata Bartsh, 1870 (ref. ID; 1345, 3688)
  4. Eothinia elongata macra Berzins, 1949
    See; Eothinia elongata (ref. ID; 2017)
  5. Eothinia eukolpa Myers, 1940 (ref. ID; 2017)
    Syn; Eothinia eukolpa Koste, 1978 (ref. ID; 2017)
  6. Eothinia lamellata Berzins (ref. ID; 2269)
    See; Eothinia elongata (ref. ID; 2017)
  7. Eothinia lasiobiotica Berzins (ref. ID; 1468)
    See; Eothinia triphaea (ref. ID; 2017)
  8. Eothinia poitera Myers, 1933 (ref. ID; 2017)
  9. Eothinia triphaea Harring & Myers, 1924 (ref. ID; 1468, 2017, 3245 original paper)
    Syn; Eothinia lasiobiotica Berzins, 1949 (ref. ID; 2017)

Eothinia argus Harring & Myers, 1924 (ref. ID; 2017, 3245 original paper)

Descriptions

The body of this species is fusiform and moderately elongate; its greatest width is about one fourth of the total length. The integument is moderately flexible and the outline fairly constant. It is a very transparent animal. The transverse folds limiting the head and neck segments are well marked. The head segment is very broad anteriorly and tapers towards the neck; its width is equal to the width of the abdomen. The neck segment is considerably narrower than the head. The abdomen is nearly cylindric for three fourths of its length and rounded posteriorly. The tail is small and three-lobed; the median lobe is subsquare and the lateral lobes rounded. The foot has two short joints of nearly equal length. The toes are slender, conical, acutely pointed and slightly decurved; their length is about one fourteenth of the total length. The corona is slightly oblique and terminates a short distance behind the mouth. The apical plate is strongly convex and unciliated; the buccal field is covered with very short, close-set cilia and has a median depression around the mouth. The marginal cilia are short except on two laterally projecting, auricle-like areas. The dorsal and lateral antennae are small setigerous papillae in the normal positions. The mastax is virgate and slightly asymmetric. The fulcrum is long and broad at the base, tapering gradually to the slightly incurved posterior end. The rami are roughly triangular and have moderately large alulae. There is a heartshaped opening just above the fulcrum; this is followed in the right ramus by four small teeth, two strong, apical teeth and two small teeth on the dorsal portion; the left ramus has five small teeth above the ventral opening and one large, apical tooth, followed by two small dorsal teeth. The rami are prolonged dorsally by two thin, blade-like curved pieces, not observed in the mastax of any other Notommatid. The unci have a single, large tooth with two small accessory teeth attached to the clubbed tip on the ventral side; the basal plate is irregularly oval and has a narrow, denticulate portion adjoining the tooth on the dorsal side. The basal plate of the manubria is large; the posterior branch is nearly straight and has a slight terminal expansion. Two slender, double-curved rods are imbedded in the walls of the mastax just below the posterior edges of the rami; they serve as support during the pumping action. The piston is large and muscular. On the left side is a granular area which appears to represent an atrophied salivary gland. The oesophagus is very long and slender. There is no constriction between the stomach and intestine. The gastric glands and ovary are normal. The cloaca functions as a bladder. The foot glands are pyriform and very small. The ganglion is large and saccate. The retrocerebral organ consists of a very small, pyriform sac and two short subserebral glands, which contain a rounded mass of bacteroids at the level of the eyespot. There are two accessory frontal eyespots on the apical plate in addition to the cervical eyespot at the posterior end of the ganglion. (ref. ID; 3245)

Comments

It is very closely related to E. triphaea, but is readily distinguished by the much shorter toes and the long retrocerebral sac. (ref. ID; 3245)

Type locality

Eothinia argus was collected in small numbers in Lenape Lake, at Mays Landing, New Jersey. (ref. ID; 3245)

Measurements

Total length 250-300; toes 18-22; trophi 38 µm. (ref. ID; 3245)

Eothinia triphaea Harring & Myers, 1924 (ref. ID; 1468, 2017, 3245 original paper)

Synonym

Eothinia lasiobiotica Berzins, 1949 (ref. ID; 2017)

Descriptions

The body of this species is fusiform and moderately elongate; its greatest width is about one fourth of the total length. The integument is very flexible and the outline changes according to the contractions of the animal. The body is very transparent. The transverse folds limiting the head and neck segments are unusually deep. The head segment is broadest anteriorly and tapers towards the neck; its width is but little less than the width of the abdomen. The neck segment is a little narrower than the head, but approximately the same length, slightly more than half the width. The abdomen increases very slightly in width for about half its length and then tapers gradually to the base of the foot; the tail is represented by a very slightly dorsal elevation. The two short foot joints continue the outline of the abdomen without any sudden reduction in width. The two toes are very long and slender, slightly decurved and incurved; they have a nearly hemispherical, slightly compressed, bulbous enlargement at the base. The length of the toes is about one seventh of the total length. The corona extends down on the ventral side about one fourth of the length of the body; the post-oral portion projects as a minute chin. The unciliated apical plate is strongly convex; the buccal field has a well marked, troughlike median depression in which the mouth is locate. The marginal cilia are short except on two lateral, auricle-like areas. The dorsal antenna is a short, stubby boss with a central depression, at the center of which is a tuft of sensory setae. The lateral antennae have not been observed. The mastax is virgate and resembles closely the type of the genus, but in the development of the unci it is a little nearer the normal Notommata-type. The fulcrum is extremely broad at the base and tapers somewhat abruptly to a slender, rodlike, slightly incurved posterior section. The rami are broadly triangular and nearly symmetrical; their inner edges are provided with short, close-set, needle-like teeth, beginning near the base and continuing to the apex. The unci have a subsquare basal plate with a well developed ventral tooth, clubbed at the tip, and a rudimentary second tooth, beginning near the base of the ventral tooth and crossing the basal plate diagonally to its dorsal edge. Two short and very slender accessory teeth are attached to the ventral edge of the principal tooth in each uncus. The basal plate of the manubrium is large and subsquare; the posterior portion is fairly stout and decurved at the tip. Two slender, slightly curved rods are imbedded in the walls of the mastax below the posterior edges of the rami; they serve as supports during the pumping action. The piston is well developed. The oesophagus is slender and moderately long. The stomach and intestine are not separated by any constriction. The gastric glands and ovary are normal. The cloaca appears to functions as a bladder. The foot glands are large, nearly circular and slightly compressed; they discharge into a small, spherical mucus reservoir, which is partly in the bulbous, basal enlargement of the toe. The ganglion is moderately large and nearly spherical. The retrocerebral sac is pyriform and very small; the subcerebral glands are short and always contain a rounded mass of bacteroids at the level of the cervical eyespot, thus producing the appearance of three eyespots in a transverse row. There are two accessory frontal eyespots on the apical plate in addition to the cervical eyespot at the posterior end of the ganglion. (ref. ID; 3245)

Type locality

Eothinia triphaea occurs in small numbers among sphagnum growing on the margins of shallow ponds. We have found it widely distributed in Vilas and Oneida Counties, Wisconsin, and also in ponds around Atlantic City, New Jersey, and at Hyattsville, near Washington, district of Columbia. (ref. ID; 3245)

Measurements

Total length 175-250; toes 25-35; trophi 28 long, 35 µm wide. (ref. ID; 3245)