The identification and discrimination of 2 closely related and morphologically similar species of Gyrodactylus, G. salaris and G. thymalli, were assessed using the statistical classification methodologies Linear Discriminant Analysis (LDA) and k-Nearest Neighbours (KNN). These statistical methods were applied to morphometric measurements made on the gyrodactylid attachment hooks. The mean estim...

Species identification Gyrodactylids are ubiquitous monogenean ectoparasites on the skin and gills of teleost fish both in marine and freshwater ecosystems. The most recent species compilation lists some 400 gyrodactylid species. Gyrodactylus salaris is a species of this genus found on fins and skin of Atlantic and Baltic salmon in its freshwater phase (Figure 1). The small (0.5 1 mm) parasite ...

In January 2020, a mortality event was documented in endangered Pallid Sturgeon (Scaphirhynchus albus) at the Neosho National Fish Hatchery (Neosho, MO, USA). Moribund fish appeared emaciated, with hemorrhages on fins and rostrums. Mortality steadily increased, prompting an investigation into cause. No viral or bacterial pathogens were detected; however, high number of novel Gyrodactylus sp. id...

Two new resveratrol trimer derivatives, named rheumlhasol A (1) and rheumlhasol B (2) were isolated from the methanolic extract of roots of Rheum lhasaense A. J. Li et P. K. Hsiao together with four known resveratrol dimer derivatives, including maximol A (3), gnetin C (4), ε-viniferin (5), and pallidol (6). The structures were determined by combined spectroscopic methods and by comparison of t...

Prevalence and intensity of Gyrodactylus colemanensis and G. salmonis (Monogenea) parasitizing juvenile/adult brook trout Salvelinus fontinalis, rainbow trout Oncorhynchus mykiss, brown trout Salmo trutta, and Atlantic salmon Salmo salar at 3 localities over an 8 km stretch in the South River, Nova Scotia, Canada, were calculated 4 times over a 9 mo period (October 2009, December 2009, March 20...

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Gyrodactylus teuchis is a widespread parasite of wild and farmed salmonids throughout Europe. It has been frequently confused with the notifiable pathogen G. salaris, to which it bears a striking morphological similarity. The species is frequently referred to as 'cryptic', and diagnoses are primarily based on molecular evidence. We provide the first comprehensive re-description of G. teuchis fr...

The monogenean ectoparasite, Gyrodactylus salaris Malmberg, 1957, has had a devastating effect on wild Atlantic salmon (Salmo salar) since its introduction to Norway in the mid-1970s. In Lake Pålsbufjorden, southern Norway, upstream of the stretches of the River Numedalslågen with anadromous Atlantic salmon, a resident Arctic charr (Salvelinus alpinus) population has been reported to be infecte...

Gyrodactylus salaris is a serious pest of wild pre-smolt Atlantic salmon (Salmo salar) in Norway. The closely related G. thymalli, originally described from grayling (Thymallus thymallus), is assumed harmless to both grayling and salmon. The 2 species are difficult to distinguish using traditional, morphometric methods or molecular approaches. The aim of this study was to explore whether there ...