Description of Two New Species of the Genus Vorticella (Ciliophora: Peritrichia) Epibionts on Pomacea canaliculata (Mollusca: Ampullariidae: Gastropoda) in Southern Brazil Author Pereira, Marcos W. O. Author Brito, Fabiano Carvalho Author Eizirik, Eduardo Author Utz, Laura R. P. text Zootaxa 2018 2018-10-31 4508 2 211 224 journal article 28050 10.11646/zootaxa.4508.2.4 d281727b-64ea-4ea1-a62e-86196701ad98 1175-5326 2607016 294C2462-ADF9-4C03-ABA0-81FC5B641EBA Vorticella veloxiiforme n.sp. Diagnosis. Freshwater peritrich, with a cup-shaped zooid measuring 57 X 41 µm on average. Conspicuous silver line system on pellicle. Horizontal, J-shaped macronucleus occupying 2/3 of the cell volume. One contractile vacuole next to the peristomial lip. Stalk with a strongly contracting a helical spasmoneme, and green endoplasmic granules. Three infundibular polykineties, each comprised of three rows of kinetosomes: P2 and P3 terminate at the same level adstomally. P1 has one longer row of kinetosomes, terminating below the level of P2 and P3, which is hook-like shaped abstomally. Type Locality . Patos Lagoon, Viamão (30° 19’70”S; 50°50’47”W ), Rio Grande do Sul , Brazil . Etymology . The specific epithet refers to the fast contraction mode of the trophont. Deposition of slide . Type material: A slide with a protargol-stained colony ( holotype ) was deposited in the Protist Collection of the Museum of Sciences and Technology of the Pontifícia Universidade Católica do Rio Grande do Sul (PUCRS), under the number MCTP05. The paratype , a slide with a marked protargol-stained colony, was deposited in the Protist Collection of the Natural History Museum in London. Morphology of live specimens. Zooids of V. veloxiiforme were inverted bell-shaped and measured on average 57.4 µm long and 41 µm wide ( Table 1 ). They also presented faint and closely spaced striae on the pellicle that, a thick peristomial lip, and a slightly elevated epistomial disk ( Figs. 1A and 2A ). A constriction below the peritomial lip was observed on the zooid body. A single contractile vacuole was found in the upper part of the zooid, close to the peristome ( Figs. 1A and 2A ). A J-shaped macronucleus was oriented along the oral-aboral axis and occupied approximately 2/3 of the volume of the cell body ( Figs. 1A , 2A and 2B ). The cytoplasm presented grayish and greenish food granules. The stalk measured on average 149.3µm in length ( Table 1 ). A spasmoneme was observed inside the stalk ( Figs. 1A and 2A ) and had several green endoplasmic granules throughout. Both the zooid and the stalk were very contractile. TABLE 1. Measurements of live specimens of V. veloxiiforme and V. ampullaria attached to Pomacea canaliculata from Patos Lagoon, Brazil. A total number of 25 zooids were measured for each character. All measurements are expressed in µm.

Character	Species	Mean	SD	Range	CV (%)
Total length of the body	U.veloxiiforme	57.4	5.5	47.5–67.5	10.0
U. ampullaria	69.8	8.1	55–87.5	10.0
Length from the peristomial lip	U.veloxiiforme	20	7.3	32.5–50	20.0
U. ampullaria	57	7.6	47.5–72.5	10.0
Width of the body	U.veloxiiforme	41	5.0	30–50	10.0
U. ampullaria	24.9	3.3	17.5–32.5	10.0
Width of the body at midpoint	U.veloxiiforme	31.8	4.9	25–37.5	20.0
U. ampullaria	30.8	5.2	22.5–37.5	20.0
Width of peristomial lip	U.veloxiiforme	51.1	5.6	37.5–62.5	10.0
U. ampullaria	31	3.9	25–37.5	10.0
Thickness of peristomial lip	U.veloxiiforme	9.1	1.8	7.5–12.5	20.0
U. ampullaria	5.4	2.4	2.5–7.5	50.0
Width of scopula	U.veloxiiforme	7.6	0.5	7.5–10	10.0
U. ampullaria	6	1.4	2.5–7.5	30.0
Length of basal stalk	U.veloxiiforme	149.3	79.1	12.5–290	60.0
U. ampullaria	114.5	66.2	17.5–240	60.0
Width of basal stalk	U.veloxiiforme	2.5	0	2.5	0
U. ampullaria	2.5	0	2.5	0

Morphology of stained specimens. The infraciliature and macronucleus of V. veloxiiforme was easily revealed by silver staining ( Figs. 1C and D , 2D ). Somatic myonemes extended from the peristomial lip to the scopula ( Fig. 1E and 3C ). The oral infraciliature was typical of peritrich ciliates, with all infundibular polykinetids composed by three rows of kinetosomes each ( Figs. 1D and 2B ). Rows of P1 were different in length: the adstomal end of the row closer to P2 was longer than the other two. The end of middle row was longer than distal rows in P1 ( Figs. 1D and 2B ). All rows of P2 showed different lengths abstomally, but all terminated at the same level adstomally ( Figs. 1D and 2B ). P3 consisted of three rows of kinetosomes forming a hook-like projection at the abstomal end ( Figs. 1D and 2B ). Adstomally, P3 terminated at the same level of P1 and P2 ( Figs. 1D and 2B ). The silver nitrate technique, and the scanning electron microscopy revealed a horizontal striation pattern and the presence of pellicular pores regularly spaced on the zooid ( Figs.3A and B ). On average, 62 horizontal sileverlines were present between the peristome and the trochal band, and 20 were counted between the trochal band and scopula ( Table 2 ; Fig. 3C ).