Eothinia elongata (Ehrenberg, 1832)

Sørensen, Martin Vinther, 2006, On the rotifer fauna of Disko Island, Greenland, with notes on selected species from a stagnant freshwater lake, Zootaxa 1241, pp. 37-49 : 40

Eothinia elongata (Ehrenberg, 1832)

Several fairly large specimens were found in the sample. All investigated specimens had trophi of bdelloid rotifers in their stomach. The species has not been recorded from Greenland previously, but has been found in Europe ( Glascott 1893; Berzins 1949, 1978; Wulfert 1960), Russia and former Soviet Union ( Kutikova 1962, 1970), Asia ( Fernando & Zankai 1981; Sharma & Pant 1985), Australia ( Koste & Shiel 1980, 1991), North America ( Harring & Myers 1922; Chengalath & Koste 1989) and Brazil ( Segers & Dumont 1995). It is considered a rare cosmopolite.

The species is distinguished by its trophi morphology combined with the presence of one large salivary gland, and one cerebral and two frontal eyes. The recorded specimens were generally typical but deviated in some details in the trophi.

Trophi from two specimens were prepared for SEM ( Fig. 2 ). The rami are large and slightly asymmetrical, with long, pointed alulae ( Fig. 2 A–D). Most posteriorly on the ventral side, two extensions from each ramus form a small hinge ( Fig. 2 E). Basifenestrae and subbasifenestrae are present. The apical rami parts bend dorsally and have a dense row of fine teeth ( Fig. 2 C). Each ramus has approximately 20 teeth. A pair of small, twisted, fanshaped oral plates is attached on the ventral side of rami ( Fig. 2 B). The fulcrum is clearly divided into a dorsal and a ventral part ( Fig. 2 A, C–D). The dorsal part is broadened laterally and composed of relatively thick sclerofibrillae that are arranged both side­by­side and on top of each other. The ventral fulcrum part is much narrower laterally, composed of one horizontal row of thick sclerofibrillae. Each uncus has one tooth with a basal lamella ( Fig. 2 F). Each manubrium is composed of a long distal cauda and a small proximal head. The head is formed by the walls of the medial and posterior manubrium chambers. Apertures from both chambers are located 1/3 from the proximal end of the manubrium ( Fig. 2 A, D). A paired epipharynx composed of two large, fan­shaped plates is present ( Fig. 2 A). Both Harring and Myers (1922) and Wulfert (1960) illustrate the epipharyngeal elements as rod­shaped sclerites with expanded distal terminals. However, their descriptions are probably based on a misinterpretation. Most of the epipharyngeal fans are extremely delicate and feebly visible with LM whereas the central parts are more robust. This may cause the sclerites to appear more rod­shaped in LM. Measurements: Body: 504 µm; toes 37 µm; trophi 64 µm; rami 38 µm; fulcrum 37 µm; manubria 47 µm; unci 17 µm; epipharynx 15 µm; oral plates 6 µm.

Figures

FIGURE 2. Eothinia elongata. SEM­photos of trophi. A: lateral view. B: rami, ventral view. C: frontal view. D: ventrocaudal view. E: detail showing basal hinge on ventral side of rami. F: uncus. bf – basifenestra; ep – epipharynx; mm – aperture from medial manubrium chamber; op – oral plates; pm – aperture from posterior manubrium chamber; sf – subbasifenestra; ul – uncus lamellae; ut – principal uncus tooth.