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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Philodinavus

Philodinavus Harring, 1913

Class Digononta: Order Bdelloidea: Family Philodinavidae (ref. ID; 6806)

Order Philodinavida: Family Philodinavidae (ref. ID; 6565)

Synonym Microdina Murray, 1905 (ref. ID; 1345, 2978, 3137, 3688)

ref. ID; 1663

Rostrum present and perfect but no corona. With four toes. (ref. ID; 1663)

ref. ID; 1923

Corona even more greatly reduced; cilia limited to small area around mouth and tip of rostrum. Single species, littoral or running water. (ref. ID; 1923)

ref. ID; 3137

Toes are four, yolk mass with four nuclei. Gullet is very short. Teeth three of four on each side and at an anterior part of jaws. The wheel-organ completely lacking. (ref. ID; 3137)
  1. Philodinavus paradoxus (Murray, 1905) (ref. ID; 1345, 1663, 1828, 1923, 2276, 3042, 3137, 3688, 6939)
    Syn; Microcodina paradoxa Murray, 1905 (ref. ID; 1345); Microdina paradoxa Murray, 1905 (ref. ID; 2276, 3137, 3688); Philodinavus paradoxus Harring, 1913 (ref. ID; 1345, 2276, 3137, 3688)

Philodinavus paradoxus (Murray, 1905) (ref. ID; 1345, 1663, 1828, 1923, 2276, 3042, 3137, 3688, 6939)

Synonym

Microcodina paradoxa Murray, 1905 (ref. ID; 1345); Microdina paradoxa Murray, 1905 (ref. ID; 2276, 3137, 3688); Philodinavus paradoxus Harring, 1913 (ref. ID; 1345, 2276, 3137, 3688)

Descriptions

The surface of the stout body is smooth. Oesophagus and a large granular mass connected with it is of a bright crimson colour. At the level of mastax and at posterior end of the trunk the body is enlarged, between those parts it is contracted. The stomach is voluminous, the walls are filled with colored globules. The rostrum is two-jointed with two rostral lamellae. The head is small. The dorsal antenna is two-jointed. The foot is three-jointed. The spurs sit far apart and they vary in the form and in the length. The upper pair of the toes is smaller than the ventral one. D.f.: 3/3 or 4/4. The wheel-organ lack completely. Only some long cilia on the origin of the gullet can be regarded as constituting a rudimentary wheel-organ. The mouth-opening has a trifoliate form. The parts of the jaws articulate movably, they are not rigidly united as in other Bdelloidea. The rami form curved processes on the ventral sides. The manubria may have no loops, or many have from one to three, more or less distinct. (ref. ID; 3137)

The body is stout with a smooth surface. It is wider at the level of the mastax and at the posterior part of the trunk, giving the appearance of a worm-like animal. There are no traces of wheel-discs, and the corona is reduced to a trilobed field of short cilia around the mouth-opening. The rostrum has two segments, with two lamellae and is relatively short. The antenna is two-segmented, with the proximal segment longer than the distal. There is no eyespot. The foot has three segments, with two spurs and two pairs of toes, the dorsal pair smaller than the ventral pair. The spurs have often been reported as variable in shape (Bartos 1951; Voigt 1957; Donner 1965). The trophi are very close to the mouth opening. In contrast to other bdelloids, the unci, with 3-4 large teeth, move a lot and do not seem to be rigidly united. Manubria, fulcrum and rami are variously structured (Voigt 1957). The species is oviparous. The egg observed in specimens from the Oberer Seebach has a kidney-shape, with a hyaline zone in the ventral part. According to Donner (1965) the body can be partially or totally orange-red coloured (carotene grains). This carotene pigment is assumed to be relevant when the animals awake from anabiosis, and when they lay their eggs (Bartos 1951). (ref. ID; 6939)

Habitat

This species has been recorded on the shore of the River Danube among Fontinalis sp. moss and at temperature between 8 to 11.5 degrees C (Donner 1972). The same author, in a earlier publication Donner (1964), remarked the presence of this species only in running water ecosystems in Poland (Pawlowski 1958) and Hungary (Varga 1951). In the Oberer Seebach it was found in August and December 1994 at temperatures between 7 and 11 degrees C on drift samples at the surface of the stream (densities between 0.3 to 0.4 ind.litre-1). Nevertheless, it is plausible that the temperature range of the species might be wider than expected. Pax & Wulfert (1942) reported the species in a thermal spring at 22.2 degrees C. Another habitat where it has been found is the hyporheos down to 40 cm depth, in March 1992 (Schmid-Araya 1993). (ref. ID; 6939)

Examined material

The specimens were collected in the stream Oberer Seebach, lower Austria (47 degrees 51'N, 5 degrees 04'E) while performing drift experiments between August and December 1994. (ref. ID; 6939)

Measurements

Total length: up to 310 µm, antenna: 13-14 µm; egg length: 64 µm; trophi length: 19 µm width: 23 µm, spurs: 12 µm, dorsal toes: 9 µm, ventral toes 12 µm. (ref. ID; 6939)