No abstract

Myxosporeans are well-known parasites infecting food fishes in fresh and marine water around the globe. Grass carp (Ctenopharyngodon idella), a freshwater food fish commonly cultured in India with has significant economic importance. Herein, the study focuses on the description of a new myxosporean species, Myxobolus grassi sp. nov. from the gills as primary site and liver as secondary site of infection in grass carp. Both organs (gill and liver) were infected concurrently in the host and the prevalence of grass carp infection was 4.05% in gill filaments and liver, respectively. Identification of species was based on the morphological and morphometric features of the myxospore as well as 18S rDNA sequence data. A smear from gill and liver exhibited hundreds of morphologically similar myxospores. BLAST search revealed 98% sequence similarity and 0.03 genetic distance with M. catlae (KM029967) infecting gill lamellae of mrigal carp (Cirrhinus cirrhosus) from India and 98–84% sequence similarity with other myxobolids in India, China, Japan, Malaysia, Turkey and Hungary. Phylogenetically, it clustered with other myxobolids infecting gills and related organs (i.e., vital organ) of Indian cyprinid carp species. On the basis of myxospore morphology and 18S sequence, we propose M. grassi sp. nov.

The present study, discusses a first report of staining techniques with silver nitrate (AgNO3) stain for the preservation and identification of myxozoans globally. The silver nitrate stain was used to prepare permanent slide preparation of myxozoans with some adaptations made in our laboratory. Fresh air dried smear were stained with silver nitrate stain ensuing dark brown color polar capsules and light brown color of spore‐wall. The stain is everlasting for years differing to other stains like Geimsa, iron‐heamotoxylin Zeihl‐Neelsen Blue, and trichome stains. Research Highlights Stains usually fade with time and fail to disclose the morphological characters of the specimen. Present staining method helps to detect less infection in the tissue locating the myxospores. The Klein dry method (1958) is useful and suitable for long term preservation of the myxozoan slides and morphological description.

Parasitic infestations are one of the major problems in freshwater fish production. Clarias batrachus Linnaeus, 1758 (Clariidae) is a commercially important native catfish mainly used for food as it has very high iron content and other minerals. Unfortunately, it is difficult to breed in captivity and is highly prone to parasitic infections particularly the Myxobolus sp. The present article discusses a new species of Myxobolus identified as Myxobolus awadhii from the gills of C. batrachus. Plasmodia were found on the gill filaments with the intensity of infection to be moderate as indicated by gill plasmodial index (GPI = 6). The mature myxospores were oval to ellipsoidal in shape measuring 8.82-11.68 (10.57 ± 0.50) 9 5.76-7.37 (6.70 ± 0.36) lm in size. The present species was compared with species found from the same host and other resembling species as M. acanthorhodi, M. bhadurius, M. bilineatum, M. chrysichthyi. Present article deals with morphological and morphometric description of M. awadhii sp. nov. Morphological comparisons of the mature myxospores were done with the similar myxospores and species reported earlier from C. batrachus.