This study examined the effects of various modifications of rearing practices on hatchery-reared Atlantic salmon (Salmo salar) fingerlings and compared condition and performance of hatchery fingerlings (age 0+) and yearlings (age 1+) with those of wild-reared Atlantic salmon. Reduced fish density (and increased ration) in rearing tanks promoted increased growth and condition factor and significant changes in muscle composition, including increased muscle lipid content and glycolytic enzyme activity, specfically phosphofructokinase and lactate dehydrogenase. However, these changes had no effect on anaerobic capacity. Moreover, swimming performance was poorer in fingerlings reared at low compared with normal density. Raising the water velocity from 0 to 4 cm ·s-1 (~0.7 body length ·s-1) had overall beneficial effects, most notably increased endurance in fixed velocity sprint tests and a reduction of ion loss in an epinephrine challenge test. Increasing velocity to 9 cm ·s-1 had no further effects. Wild fingerlings were larger with better fin quality and superior anaerobic capacity and swim performance. Even larger differences were seen between hatchery-reared and wild yearlings. It is concluded that significant changes in morphology, physiology, and muscle biochemistry of juvenile Atlantic salmon can be brought about by changing hatchery rearing conditions, but these changes are of limited effectiveness in reducing the difference between hatchery-reared and wild fish.

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Abstract. Methods are described for making chromosome preparations from developing embryos of Helophorus, for producing C‐ and G‐banding, and for staining the nucleolus organizer with silver. These methods are used to compare the karyotypes of two species currently included in H.aquaticus (L.). It is shown that these species differ because of reciprocal translocations between some chromosomes, and that they would therefore be unable to produce fertile hybrids. Morphological differences in the male and female genitalia are described, and the range of aedeagal variation shown by each species is established by reference to chromosome preparations from testis. Reference to the relevant type specimens shows that the two species are H.aequalis Thomson and H.aquaticus (L.). The latter is not a British species. Differences in the egg cocoons and third instar larvae are described. The present distributions and Pleistocene histories of the two species are described.

Within the Hydroporini, the Deronectes-group of genera are characterised by having the mesosternal fork and metasternal keel separated (or secondarily fused), the ventral elytral ridge posteriorly elevated but without ligula, and the male protarsus ventrally without adhesive discs. The genera of the group, viz. Deronectes Sharp, 1882, Stictotarsus Zimmermann, 1919, Scarodytes Gozis, 1914, and Nebrioporus Regimbart, 1906, are reclassified and a hypothesis of their phylogenetic relationships is presented. Karyotypes of 14 European species of Hydroporinae are discussed. Nebrioporus is extended to include most species with parameres with apex hook-like and sclerotised, with Potamonectes Zimmermann, 1921, as a junior synonym, syn. n. Nebrioporus s. str. and Zimmermannius Guignot, 1941 are recognized as subgenera of Nebrioporus. Scarodytes is kept as a separate genus because of its characteristic ventral sculpture and seemingly higher number of autosomes than in Nebrioporus. The species with simple parameres previously placed in Potamonectes are transferred to Stictotarsus together with S. bertrandi (Legros, 1956), previously in Deronectes. Consequently, Trichonectes Guignot, 1941, is a junior subjective synonym of Stictotarsus, syn.n. In an appendix, a check-list is provided for the species of the Deronectes-group. The subgenus Nebrioporus s. str. is divided into three species-groups: the kilimandjarensis-, the abyssinicus-, and the depressus-groups.

Species in cryptic complexes are, per definition, difficult to identify using morphological characters. One such complex was recently detected in the dung beetle Aphodius fimetarius (Linnaeus) sensu lato, an abundant dung beetle with a wide distribution. While the two component taxa, Aphodius fimetarius sensu stricto and Aphodius pedellus (De Geer) exhibit distinctly different karyotypes, the validity of subtle morphological characters proposed to distinguish between them has been debated. Given the variability and minor interspecific differences in external characters, the large‐scale distribution of respective taxa has remained unknown, as have potential differences in ecology and habits. In this study, we ask how A. fimetarius and A. pedellus can best be distinguished, whether the use of different types of characters (karyotypes, DNA sequences and morphological traits) results in consistent species identification, where these species occur and whether they exhibit ecological differences. In total, we inspected a material of 4401 individuals from across the globe, of which 183 were examined for both mtDNA sequences and morphology, 154 for both morphology and karyotype, and 9 (including the recently proposed neotype of Aphodius fimetarius) for all three types of characters. As a marker gene, we sequenced a 590 bp region of the cytochrome c oxidase I gene for 183 individuals. Overall, DNA sequences offered a clear‐cut distinction between taxa: sequences of A. fimetarius and A. pedellus differed by an average pairwise distance of 8.2%, whereas variation within species was only 0.9% for A. fimetarius and 0.5% for A. pedellus. Morphological and chromosomal characters offered species identifications consistent with that of molecular characters: karyotypes identified as A. pedellus consistently fell within one of the molecular clades, whereas karyotypes identified as A. fimetarius fell within the other clade. Likewise, the majority of individuals identified by morphological characters were assigned to the same species by sequence‐based characters. Both taxa thus defined were found to be Holarctic in distribution, with major sympatry within Central and Southern Europe and mixed patterns of sympatry within the US. Northern areas of Europe, Asia and North America are dominated by A. pedellus alone. Within A. pedellus, patterns of sequence diversity were indicative of a recent population expansion. In the western US, the phenology of a population of A. fimetarius was observed to significantly differ from that of a sympatric population of A. pedellus, thereby revealing an ecological difference between the two cryptic taxa. Overall, we conclude that all types of characters offered a consistent classification of the two species. Thus, the laborious karyotyping techniques used to originally establish the presence of two cryptic taxa can now be substituted by characters more easily applied to large ecological samples. Using this approach of integrative taxonomy, we were able to establish the global distribution and sp...

Chromosome preparations were made from mid-gut and ovarian cells of adult Notonecta glauca L., N. obliqua Thunberg, N. maculata F. and N. viridis Delcourt, using the acetic acid dissociation, air-drying method (Crozier 1968) with Giemsa staining. C-banding was obtained by treatment with barium hydroxide and salt-sodium citrate (2xSSC). The karyotypes of the first three species are very similar, with 11 pairs of autosomes plus XY sex chromosomes (plus sometimes a small 12th autosome pair in N. glauca), and the sequence of chromosome sizes very similar. However, the four longest pairs of autosomes, and the X chromosomes, have characteristic C-band patterns, which differ between the species. The karyotype of N. viridis is more distinct, with one pair of long autosomes, while the remaining chromosomes are much shorter. The long autosomes have distinct C-bands, but these are present in only one of the shorter pairs, as faint terminal bands. In warm conditions the long autosomes of N. viridis appear rod-like, but in cold conditions they have one end heavily condensed, giving a tadpole-like appearance.

Aim To undertake a quantitative review of the Quaternary fossil record of European water beetles to evaluate their geographical and temporal coverage, and to characterize the extent and typology of the shifts in their geographical ranges.Location Europe. MethodsWe compiled Quaternary water beetle records from public databases and published references. We included in the analyses species of 10 families of aquatic Coleoptera, and recorded range shifts through the comparison of the location of fossil remains with the current distribution of the species. We explored the ecological representativeness of the fossil record, as well as the relationship between range shifts and the habitat type of the species. ResultsOur final data set included over 9000 records for 259 water beetle species. Fossil remains of aquatic beetles have been documented exclusively north of 42°N, with most of the records from the British Isles and virtually none from southern Europe or the Mediterranean Basin. Over 80% of the records were from the Late Glacial and the Holocene periods (the last 15 kyr), and overall approximately 20% of the species have been recorded outside their present range (23% excluding Holocene records). Most range shifts were southern or western extensions of currently widespread, northern species, with 10 species displaying major range shifts through the Palaearctic. Lentic species were significantly more likely to have experienced major range shifts, even accounting for the general ecological bias of the fossil record towards lentic habitats. Main conclusionsOur results show that the Quaternary record of aquatic Coleoptera is geographically, temporally and ecologically skewed, necessitating caution when extrapolating general conclusions about range changes and ecological stability to other areas or periods on the basis of such scattered evidence. Most central and northern European species for which there are fossil records seem to have conserved their ranges through the Late Pleistocene, with geographical shifts mostly restricted to species with current widespread north Palaearctic or Holarctic distributions. Major range shifts through the Palaearctic are taxonomically uneven, suggesting either an idiosyncratic behaviour of taxa depending on ecological or phylogenetic factors, or a sampling artefact produced by the limited availability of taxonomic expertise.

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