Morphological characteristics and DNA sequencing were used to identify plerocercoids of a Schistocephalus sp. infecting slimy sculpin (Cottus cognatus) from northern New Brunswick and plerocercoids of Ligula intestinalis infecting blacknose dace (Rhinichthys atratulus) in Fundy National Park (FNP, New Brunswick). To our knowledge, no previous publications documented either cestode from New Brunswick, Canada. Blacknose dace represent a new host record for L. intestinalis. Identifications were made based on the presence or absence of segmentation and sequencing partial nicotinamide adenine dinucleotide dehydrogenase subunit 1 (ND1; mitochondrial DNA) and/or partial cytochrome c oxidase subunit 1 (COI; mitochondrial DNA). Plerocercoids from blacknose dace in FNP were identified as Ligula intestinalis based on >99% nucleotide identity with COI for this species in the NCBI GenBank database. Plerocercoids in slimy sculpin from northern New Brunswick were identified as a Schistocephalus sp. based on high nucleotide identity with congenerics in the NCBI GenBank database. The absence of GenBank entries with sufficient high percent identity to our specimens, and potential species hybrids in this genus, prevents species-level identification of Schistocephalus sp. plerocercoids currently. The absence of previous documentation of these cestodes might reflect recent environmental change promoting the transmission of these parasites that can modulate host fish behavior, induce sterility of host fishes, and contribute to epizootics.

Canadian fish-based environmental effects monitoring programs use individual and population-level endpoints to assess aquatic health. Impacts of coal mining and selenium (Se) exposure were assessed in slimy sculpin (Cottus cognatus) from reference streams located both inside and outside of a coal zone, and from 1 stream with a history of coal mining, using traditional environmental effects monitoring endpoints. In addition, physical characteristics of the streams and benthic macro-invertebrate communities were assessed. To determine whether the assessment of effects could be improved by including molecular markers, real-time polymerase chain reaction assays were optimized for genes associated with reproduction (vtg, esr1, star, cyp19a1, and gys2), and oxidative and cellular stress (sod1, gpx, gsr, cat, and hsp 90). Water Se levels exceeded guidelines in the stream with historical mining (4 μg/L), but benthic macroinvertebrates did not exceed dietary thresholds (2-3 μg/g dry wt). Whole-body Se levels were above British Columbia\'s tissue guideline in fish from all streams, but only above the draft US Environmental Protection Agency (USEPA) criterion (7.91 μg/g dry wt) at the reference stream inside the coal zone. Some markers of cellular and oxidative stress were elevated in fish liver at the exposed site (sod1, gpx), but some were lower (cat, sod1, gpx, gsr, hsp90) in the gonads of fish inside the coal zone. Some of the differences in gene expression levels between the reference and impacted sites were sex dependent. Based on benthic macroinvertebrate assessments, the authors hypothesize that traditional and molecular differences in slimy sculpin at impacted sites may be driven by food availability rather than Se exposure. The present study is the first to adapt molecular endpoints in the slimy sculpin for aquatic health assessments.

Sampling in Iliamna Lake, Alaska, U.S.A. revealed that a greater proportion of coastrange sculpins Cottus aleuticus were infected by the cestode Schistocephalus solidus than slimy sculpins Cottus cognatus (52 v. 23%), and infected C. aleuticus contained more cestodes than did C. cognatus (2·1 v. 1·3 per fish). Consumption of sockeye salmon Oncorhynchus nerka eggs (the primary diet item) was lower in fishes with cestodes, and a model based on cestode prevalence and age composition estimated higher rates of infection and parasite-associated mortality in C. aleuticus compared with C. cognatus.