First record of three African trichodinids (Ciliophora: Peritrichida) in cultured Nile tilapia (Oreochromis niloticus) in Saudi Arabia with re-evaluation of their host specificity

Abstract

Saudi Arabia has a developing aquaculture industry that farms primarily tilapia. Although trichodinids are presumably the most usually encountered protozoan parasites in these cultured fish, they have rarely been studied in this context, and there is no data on the species that might infect cultured tilapia in Saudi Arabia. The present study was therefore carried out as a general survey to investigate the occurrence and identify the species of trichodinids that can infect cultured tilapia (Oreochromis niloticus) in Saudi Arabia. A total of 500 tilapia fish were collected from fish farms in Riyadh city and examined in order to determine the species of trichodinids present in the positive specimens. Three species of trichodinids (Trichodina maritinkae, T. centrostrigeata and T. frenata) were isolated and described as new records in Saudi Arabia. These trichodinids were found simultaneously in the same fish with overall prevalence of 20% (100/500). The identification and characterization of these three species are documented based on Riyadh specimens, for the first time. Additionally, the present paper confirms the existence of T. frenata for the second time globally and establishes this trichodinid as a new parasite for O. niloticus. T. maritinkae is highly specific to clariids, and previously, it has not been reported from any fish species other than clariids. The present work also confirmed that T. centrostrigeata can also infest cichlid fish. The list of host records of these species is expanded and their host specificity re-evaluated based on the results of this study in addition to the previously published data. We conclude that there is a need for further study of the impacts of these Trichodina spp. on Saudi Arabian fishery sector.

First diagnosis of ectoparasitic ciliates (TrichodinaandChilodonella) on farmed juvenile yellow catfish,Tachysurus fulvidracoin China

“…Subsequently, T. maritinkae was described from two other South African Clarias species and from another Clarias species in Taiwan and China, thus the host specificity for Clarias species has been assumed (Basson & Van As, ; Van As & Basson, ). However, succeeding studies, including this study, have contradicted this opinion and indicated that T. maritinkae shows low host specificity (Abdel‐Baki et al, ; Yu, Zhao, & Tang, ). The population described in this study possessed shorter rays and fewer radial pins than those of the previously reported populations.…”

“…Trichodina species have long been considered a primary cause of disease outbreaks in cultured fish (Abdel‐Baki et al, ; Maciel, Garcia, Chagas, Fujimoto, & Tavares‐Dias, ; Saha, Bandyopadhyay, & Göçmen, ; Tang, Zhang, & Zhao, ; Valladao, Gallani, Padua, Martins, & Pilarski, ; Wang, Zhou, Guo, et al, ). Basson and Van As () pointed out that the larval and juvenile stages of fish are the most susceptible to Trichodina infestation.…”

“…Ectoparasitic ciliates are protozoan parasites that are considered highly harmful to cultured fish. Several species of these parasites can cause severe diseases and mass host mortality, resulting in considerable economic losses in the fisheries sector (Abdel-Baki, Al Ghamdi, & Al-Quraishy, 2017;Deng, Guo, Zhai, Wang, & Gu, 2015;El-Tantawy & El-Sherbiny, 2010;Lom & Dyková, 1992;Tang & Zhao, 2007;Wang, Deng, Zhou, Yang, & Gu, 2018). Trichodinids, which are morphologically characterized with the presence of a prominent denticular adhesive disc, are probably the most common ectoparasitic ciliates on various aquatic organisms (Lom, 1958;Van As & Basson, 1989).…”

Unveiling associations between ciliate parasites and bacterial microbiomes under warm‐water fish farm conditions – a review

“…Within these, the trichodinids are among the most commonly encountered; in the tilapia culture industry (Abdel‐Baki et al . , 2017), their infection pressure is linked to high levels of organic matter in the water (Madsen et al . , 2000).…”