New data on flatfish scuticociliatosis reveal thatMiamiensis avidusandPhilasterides dicentrarchiare different species

Abstract

Scuticociliatosis is a severe disease in farmed flatfish. However, the causative agent is not always accurately identified. In this study, we identified two isolates of scuticociliates from an outbreak in cultured fine flounder Paralichthys adspersus. Scuticociliate identification was based on morphological data, examination of life stages and the use of molecular approaches. The isolates were compared with a strain of Philasterides dicentrachi from turbot Scophthalmus maximus and with a strain deposited in the American Type Culture Collection as Miamiensis avidus ATCC® 50180™. The use of morphological, biological and molecular methods enabled us to identify the isolates from the fine flouder as P. dicentrarchi. Comparison of P. dicentrachi isolates and M. avidus revealed some differences in the buccal apparatus. Unlike P. dicentrarchi, M. avidus has a life cycle with three forms: macrostomes (capable of feeding on P. dicentrarchi), microstomes and tomites. Additionally, we found differences in the 18S rRNA and α- and β-tubulin gene sequences, indicating that P. dicentrarchi and M. avidus are different species. We therefore reject the synonymy/conspecificity of the two taxa previously suggested. Finally, we suggest that a combination of morphological, biological, molecular (by multigene analysis) and serological techniques could improve the identification of scuticociliates parasites in fish.

Molecular data confirm the species status of Neoechinorhynchus personatus and N. yamagutii (Acanthocephala, Neoechinorhynchidae) from the Atlantic and Pacific grey mullets (Teleostei, Mugilidae)

“…DNA was analysed to estimate its purity and concentration with the NanoDrop ND-1000 Spectrophotometer (NanoDrop Technologies, USA). PCR amplifi cation was performed as previously described by Leiro et al (2000) and De Felipe et al (2017). Th e universal eukaryotic primers (F-566:5'-CAG CAG CCGCGGTAATTC C-3' and R-1200:5'-CCC GTGTTGAGTCAA ATT AAG C-3') proposed by Hadziavdic et al (2014) were used to amplify V4 and V5 variable region of 18S rRNA gene as regions with high taxonomic information.…”

Interactions between the Parasite Philasterides dicentrarchi and the Immune System of the Turbot Scophthalmus maximus. A Transcriptomic Analysis

“…The subclass Scuticociliatia (Protozoa, Ciliophora) includes several families of free-living ciliates that are abundant in marine habitats. Some scuticociliate species, including P. dicentrarchi , have acquired the capacity to infect fish, causing high mortalities in some cultured fish species, including flatfish [ 1 , 2 , 3 , 4 , 5 ]. However, there is no clear picture of what makes this scuticociliate a fish pathogen.…”

Metagenomic next-generation sequencing reveals Miamiensis avidus (Ciliophora: Scuticociliatida) in the 2017 epizootic of leopard sharks (Triakis semifasciata) in San Francisco Bay, California

“…This finding is consistent with reports of higher intraspecific variation of the cox1 gene (Jung et al 2011;Budiño et al 2011). Nonetheless, using multiple genes for molecular phenotyping can add confidence, as there remain discrepancies in the field about highly-similar taxa such as M. avidus and Philasterides dicentrarchi (Jung et al 2011;De Felipe et al 2017), and there are likely sub-species divisions yet to be realized (Gao, Katz, and Song 2012).…”