Abstract
This study was a co-operative investigation of myxosporean infections of Notopterus notopterus, the bronze featherback, which is a popular food fish in the South Asian region. We examined fish from Lake Kenyir, Malaysia and the River Ganga, Hastinapur, Uttar Pradesh, India, and observed infections with two myxosporeans: Myxidium cf. notopterum (Myxidiidae) and Henneguya ganapatiae (Myxobolidae), respectively. These species were identified by myxospore morphology, morphometry and host tissue affinity, and the original descriptions supplemented with small-subunit ribosomal DNA sequences and phylogenetic analysis. Free myxospores of M. cf. notopterum were found in the gallbladder, and measured 14.7 ± 0.6 μm long and 6.3 ± 0.6 μm wide; host, tissue and myxospore dimensions overlapped with the type, but differed in morphological details (spore shape, valve cell ridges) and locality (Malaysia versus India). Plasmodia and spores of H. ganapatiae were observed in gills, and myxospores had a spore body 9.7 ± 0.4 μm long, 4.5 ± 0.5 μm wide; sample locality, host, tissue, spore morphology and morphometry matched the original description. Small-subunit ribosomal DNA sequences were deposited in GenBank (M. cf. notopterum MT365527, H. ganapatiae MT365528) and both differed by >7% from congeneric species. Although the pathogenicity and clinical manifestation of myxozoan in humans are poorly understood, consumption of raw fish meat with myxozoan infection was reported to be associated with diarrhea. Identification of current parasite fauna from N. notopterus is an essential first step in assessing pathogen risks to stocks of this important food fish.
Highlights
The bronze featherback, Notopterus notopterus Pallas, 1769 (Osteoglossiformes) is a member of a group commonly called “knife fishes”, which are distributed widely in Africa, South and Southeast Asia (Talwar and Jhingran, 1991)
We found a Myxidium species, M. cf. notopterum, from the gall bladder of fish from Lake Kenyir, Malaysia, and we re-described Henneguya ganapatiae, from gills of N. notopterus from River Ganga, Hastinapur, Uttar Pradesh, India
The parasite fauna of fishes belonging to Notopteridae is poorly studied, with data available only for the bronze featherback, N. notopterus
Summary
The bronze featherback, Notopterus notopterus Pallas, 1769 (Osteoglossiformes) is a member of a group commonly called “knife fishes”, which are distributed widely in Africa, South and Southeast Asia (Talwar and Jhingran, 1991). Notopterus notopterus is a important food fish, with high commercial value. The fish is valued as a decorative species in the aquarium trade (Mohanty and Samanta, 2016). Natural populations are impacted by excessive harvesting, and pollution from industrial, domestic and agricultural sources, which has led to increased concentrations of heavy metals in fish tissue (Ngor et al, 2003; Shah et al, 2009; Mohanty and Samanta, 2016). Initial attempts have been made to culture the fish (Rahmatullah et al, 2009; Mohanty and Samanta, 2018). Identification of parasites that infect N. notopterus is a fundamental part of assessing disease risks to both wild and cultured stocks of this important food fish
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