Entodinium contractum

Cedrola, Franciane, Martinele, Isabel, Dias, Roberto Júnio Pedroso, Fregulia, Priscila & D’Agosto, Marta, 2016, Rumen ciliates in Brazilian sheep (Ovis aries), with new records and redescription of Entodinium contractum (Entodiniomorphida: Ophryoscolecidae), Zootaxa 4088 (2), pp. 292-300 : 293-297

E. contractum , which was originally discovered in the rumen contents of the gaur Smith (Kofoid & Christenson 1933) and not found since, was rediscovered in the present study. This species is redescribed here in detail ( Figure 3 and Table 2 ) using the information obtained from specimens stained with the Lugol’s solution and impregnated with silver carbonate.

The body of E. contractum has a pear shape ( Figure 3 A and 3B) and is laterally compressed and slightly rounded at the posterior end (body length 52.09 µm ± 3.14 [mean ± SD] and body width 32.64 µm ± 2.76). There are no caudal processes. The external surface contains small longitudinal striations ( Figures 3 C and 3D). A single retractable ciliary zone (adoral ciliary zone) is located at the anterior end of the body, surrounding the vestibular opening ( Figure 3 A and 3B). The vestibulum is long and prominent (occupying ~1/3 of the body length) and curves dorsally toward the macronucleus ( Figures 3 C and 3D). The ectoplasm is clear and contains the nuclear apparatus and the contractile vacuole ( Figures 3 A-D). The macronucleus, rod shape, is wider in the anterior region than in the back, long and slightly curved (macronuclear length: 47.46 µm ± 7.35). The micronucleus is oval and is located ventral to the macronucleus ( Figure 3 C and 3D). A small contractile vacuole is located on the right surface of the macronucleus. The endoplasm is clear and often contains a considerable number of digestive vacuoles. The rectum is a slender tubular structure at the posterior end of the body and opens through a small pore, the cytoproct ( Figures 3 A and 3B).

The oral infraciliature of E. contractum is composed of an adoral polybrachykinety (AP), vestibular polybrachykinety (VP), and paralabial kineties (PK). The C-shaped AP involves the vestibular opening. The VP has the same width as does the AP and extends into the vestibulum from the dorsal edge of the AP. The PK is composed of more than four short transverse kineties which extend along the right ventral side of the AP ( Figure 3 C and 3D).

Figures

FIGURE 3. Entodinium contractum Kofoid & Christenson recorded in Brazilian sheep. A. Schematic drawing based on live observation; B. Specimen of Entodinium contractum after Lugol’s solution; C. Schematic drawing based on silver carbonate impregnation. D. Specimen of Entodinium contractum after silver carbonete impregnation. ACZ: Adoral ciliary zone; AP: Adoral polybrachkynety; Ma: Macronucleus; Mi: Micronucleus; Ve: Vestibulum; VP: Vestibular polybrachkynety. Bars: 20 µm.

Tables

TABLE 2. Morphometric characterization of Entodinium contractum recorded in Brazilian sheep.

Characters Mean	SD	Min	Max	CV (%)	n
Body length* 52.09	3.14	44.47	58.21	6	20
Body width 32.64	2.76	26.71	38.50	8	20
Body length / width Body 1.60	0 0.14	1.37	1.92	9	20
Macronuclear length 47.46	7.35	42.20	50.32	15	20
Macronuclear width 5.47	0.66	4.32	6.72	12	20
Macronuclear length / body length 0.91	0 0.14	0 0.40	1.05	15	20
Macronuclear length / width Macronuclear 8.83	1.80	3.26	11.65	20	20