Abstract
BackgroundHenneguya Thélohan, 1892 (Myxobolidae) is one of the most species-rich genera of myxosporean parasites infecting fish. Although common in nature, there are few reports of these parasites causing important disease in aquaculture. In this paper, we describe a new species of Henneguya infecting Pagrus major (Temminck & Schlegel), a fish host introduced to the Mediterranean Sea from Japan in the late 1980s.ResultsLarge plasmodia of the parasite were found in the bulbus arteriosus and in the ventricle of the infected fish. Spores were found mainly in the kidney and heart and were accompanied by melanized macrophages or vascular intimal proliferation mixed with a mild non-suppurative response, respectively. Comparisons of morphometric data for spore and polar capsule length and width, suggest a unique combination of features in the newly described species. Molecular analysis, based on 18S rDNA sequence of the parasite, followed by phylogenetic analysis, indicated that the parasite described here is a novel species of Henneguya, clustered with the marine congeneric species.ConclusionsHenneguya aegea n. sp. infects in aquaculture P. major, a host introduced as eggs to the Mediterranean from Japan. Despite the high host specificity of the myxobolid parasites, H. aegea n. sp. seems to be able to use P. major as a host and propagate successfully, causing morbidity and mortality. This could result in spillback of the new species from high density cultured non-native P. major to native fish hosts.
Highlights
Henneguya Thélohan, 1892 (Myxobolidae) is one of the most species-rich genera of myxosporean parasites infecting fish
Being exotic to the Mediterranean Sea, the red seabream showed limited, if any, pathological problems related to parasites, at least at the beginning of its rearing history, consistent with the assumption that most locally occurring parasites will be specific for local indigenous hosts
Most of the fish examined (~ 90%) appeared normal externally with no hemorrhages on skin or erosion of fins, but sometimes the skin was dull with superficial inflammation, minor erosions and scale loss
Summary
Henneguya Thélohan, 1892 (Myxobolidae) is one of the most species-rich genera of myxosporean parasites infecting fish. Katharios et al Parasites Vectors (2020) 13:27 post-harvest while consumers expect the normal bright pink-red of the wild fish [1,2,3] It was replaced in due course by the non-indigenous but morphologically similar congeneric red seabream, Pagrus major (Temminck & Schlegel) [4]. As it has been described for salmonids cultured in net pens in British Columbia, naïve species may contract some unusual infections when placed in a new geographical area [5]. Many of these “unusual” infections in salmonids were caused by myxosporean parasites
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