Morphological and molecular identification of epibiontic sessilid Epistylis semiciculus n. sp. (ciliophora, Peritrichia) from Procambarus clarkia (Crustacea, Decapoda) in China

Abstract

Data on sessilinasis from Procambarus clarkia are limited. This study investigates sessilid diversity in Hubei Province, China in 2016. Procambarus clarkia pereopods were covered by two sessilid morphotypes in April and May, and the gills were adhered by one of these two morphotypes (morphotype I) in January. Identifying the two morphotypes according to their morphological characters through live observations and protargol-stained method is difficult. Both morphotypes show almost identical morphological characteristics: zooids present vase-shaped, the length-to-width ratio is 2:1, the semicircle-shaped peristomial disk is evidently above the peristomial lip, single contractile vacuole is located below the peristomial lip, and the oral infraciliature shows identical arrangement which can be distinguished from other Epistylis. However, the morphometric data of the two morphotypes are significant different: body size of morphotype I is 78.9–103.8 × 32.1–54.6 μm, whereas that of morphotypes II is 136.7–171.5 × 60.9–88.0 μm. To further identify the two morphotypes, molecular regions including small subunit ribosomal DNA (SSU rDNA) sequences, large subunit ribosomal DNA (LSU rDNA) sequences, and ITS1-5.8S-ITS2 sequences were used. Results supported that the two morphotypes are single species of genus Epistylis rather than distinct species based in their distinct size ranges and temporal presence events. We assigned it the name E. semiciculus n. sp. with respect to the semicircular peristomial disk. Overall, these findings emphasized the importance of using molecular data to solve the identification confusion caused by ontogenetic processes. This study is the first morphological and molecular characterization of a sessilid isolated from P. clarkia under aquaculture conditions.

Farmed Chinese Perch (Siniperca chuatsi) Coinfected with Parasites and Oomycete Pathogens

“…Although this method is still in its infancy, with immature technology for domestication, it represents a future development trend of the Chinese perch farming industry [3][4][5]. Nonetheless, a challenge lies ahead in the form of Sessilida ciliate infections, which tend to spread during intensive culture conditions [13,15,16]. In the present study, Sessilida ciliates mainly parasitized the dorsal fins of Chinese perch, and generally, they did not directly cause death but rather allowed secondary oomycete infection.…”

“…Although this method is still in its infancy, with immature technology fo domestication, it represents a future development trend of the Chinese perch farmin industry [3][4][5]. Nonetheless, a challenge lies ahead in the form of Sessilida cilia infections, which tend to spread during intensive culture conditions [13,15,16]. In th…”

On four epibiotic peritrichous ciliates (Protozoa, Ciliophora) found in Lake Weishan Wetland: morphological and molecular data support the establishment of a new genus, Parapiosoma gen. nov., and two new species

“…However, the remaining epistylidids still do not form a monophyletic group and their systematics remains confused due to the lack of sufficient morphological and molecular data for most species. Additionally, recent studies have shown that epibiotic epistylidids could provide new insights for exploring the evolutionary routes for sessilids, although compared to their free-living counterparts, investigations of epibiotic epistylidids are limited (Lu et al 2020 ; Song et al 2003 ; Wang et al 2017 ; Zhou et al 2019a , b ).…”

Ciliates as Symbionts

“…Also, very different topics about ciliates and their hosts have been developed as shown: symbiotic interactions [epibiotic, hyperepibiotic, commensals, parasites (obligates and facultatives)], codiversification: [29][30][31][32][33][34][35][36][37]. Morphology (variation, molecular characterization): [38], clevellandellid, Nyctotheroides; [39], Dicontophrya; [40,41] peritrichs. Taxonomy (new family, genus or species), redescription, revision: Apostomatia: [42]; Apostomatida: [43]; Trichodina: [44]; Epistylis and Opercularia: [45]; Spirochona: [46]; Buetschlia and Charonina: [47,48,[49][50][51]31].…”