Epistylis riograndensis, Utz, Laura R. P., Farias, Ana Carolina Silva Rodrigues, Freitas, Eduarda Correa & Araújo, Gabriella Oliveira De, 2014

Utz, Laura R. P., Farias, Ana Carolina Silva Rodrigues, Freitas, Eduarda Correa & Araújo, Gabriella Oliveira De, 2014, Description of Epistylis riograndensis n. sp. (Ciliophora: Peritrichia) found in an artificial lake in Southern Brazil, Zootaxa 3869 (5), pp. 557-564: 559-561

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Epistylis riograndensis

n. sp.

Epistylis riograndensis  n. sp.

Diagnosis. Freshwater Epistylis  bearing green algae in its cytoplasm. The species exists as dichotomously branched, umbellate colonies of elongate zooids measuring on average 162 µm in length and 45 µm in width, with a C-shaped macronucleus that lies transversally in the adoral half of the cell. All infundibular polykineties consisted of 3 rows of kinetosomes; PK 2 terminated at the adstomal curvature of PK 1, and PK 3 terminated midway between the adstomal ends of PK 1 and PK 2.

Type locality. Artificial lake in the Botanical Garden located in Porto Alegre municipality (30.03 ’08’’ S; 51.10 ’ 40 ’’ W), Rio Grande do Sul, Brazil.

Etymology. The specific epithet refers to the state of Rio Grande do Sul.

Deposition of slide. One slide with protargol-stained specimens was deposited in the Protist Collection of the Museum of Science and Technology of the Pontifícia Universidade Catolica do Rio Grande do Sul, Brazil under the number MCTP 02.

Morphology of live specimens. Colonies of E. riograndensis  were alternating irregular branched with secondary and tertiary branches terminating at the same level to create an overall flabellate shape ( Figure 1View FIGURES 1 – 9 and 10View FIGURE 10 – 11 A). Neither the basal stalk nor the branches were contractile. The basal stalk had a smooth surface without ridges or protuberances ( Figure 1View FIGURES 1 – 9), and was approximately the same diameter as the primary branches ( Table 1) that were in general longer than the basal stalk. Colonies had up to 182 zooids, but usually consisted of 20–30 zooids of similar dimensions. Zooids were elongate and ranged from 115 to 221.5 µm in length, and from 35.7 to 50 µm in width ( Table 1; Figure 2View FIGURES 1 – 9). When contracted, the zooid was transversely folded in the region near the scopula ( Figure 10View FIGURE 10 – 11 B) The peristomial lip was wider than the body and the epistomial disk was moderately elevated above it ( Figure 3View FIGURES 1 – 9). A single “C-shaped” macronucleus was observed lying transversely in the adoral half of the cell ( Figure 4View FIGURES 1 – 9).

Morphology of stained specimens. Infraciliary characteristics and the macronucleus of E. riograndensis  were easily revealed by protargol staining. Reticulate somatic myonemes extended from the epistomial disk to the scopula of the zooid ( Figure 5View FIGURES 1 – 9). The trochal band was located 10 to 15 µm, on average adoral of the scopula ( Figure 6View FIGURES 1 – 9). The oral infraciliature was typical of peritrich ciliates and presented an inner polykinety and an outer haplokinety that made 1 ½ circuits around the peristome before entering the infundibulum. Three infundibular polykinetids (PK 1, PK 2, and PK 3) all consisting of three rows of kinetosomes, were observed ( Figure 7View FIGURES 1 – 9): rows of PK 1 were equal in length and ended adstomally at the margin of the cytostome ( Figure 8View FIGURES 1 – 9). Rows of PK 2 also were equal in length, terminating at the adstomal curvature of PK 1 on one end and merging with the rows of PK 1 abstomally ( Figure 8View FIGURES 1 – 9 and 11View FIGURE 10 – 11). PK 3 consisted of three long rows of kinetosomes of equal length that terminated approximately midway between the adstomal ends of PK 1 and PK 2 ( Figure 9View FIGURES 1 – 9 and 11View FIGURE 10 – 11).

Molecular analyses. The Epistylis riograndensis  18 S sequence allowed an assessment of its phylogenetic position within Peritrichia. All phylogenetic trees generated with different methods were congruent ( Figure 12View FIGURE 12), showing that E. riograndensis  clustered with other Epistylis  species within the order Vorticellida.

Character Mean (µm) SD (µm) Mode CV (%) Range Total length of the body from epistomial disk to aboral end 52.8 6.2 50 11.7 45 – 62.5 Width of the body at midpoint between oral and aboral ends 42 6.9 45 16.0 32.5 – 50 Distance between Trochal Band and Scopula 12.2 1.9 12.5 16.1 10 – 15 Length of Basal Stalk 85.0 8.6 87.5 10.1 75 – 100 Width of Basal Stalk 10.5 3.2 12.5 30.8 5 – 12.5 Length of the Macronucleus 21.4 4.1 25 19.5 12.5 – 25 Width of Macronucleus at Midpoint 10.8 3.0 12.5 28.4 7.5 – 15

TABLE 1. Measurements of live colonies of Epistylis riograndensis attached to coverslips collected from an artificial lake in the Botanical Garden, Southern Brazil. A total number of 25 zooids were measured for each character.

  Mean (µm)   Mode  
        14.5 115 – 212.5
Width of the body at midpoint between oral and aboral ends        

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