Parr-smolt transformation in nonanadromous Atlantic salmon Salmo salar and effects of sexual maturation on the parr-smolt transformation in male anadromous Atlantic salmon

The parr-smolt transformation was compared in male and female anadromous (SRxSR), nonanadromous (LLxLL) and hybrid (SRxLL) Atlantic salmon, Salmo salar. Seasonal patterns in total lipid content, moisture content, condition factor, silvering, and branchial Na+-K+ ATPase activity indicate that smoltification occurred in immature SRxSR females while previously mature SRxSR males did not smoltify. It was also apparent that, in general, smoltification was not completed in either sex of the SRxLL or LLxLL salmon. Histological examination of gill tissue revealed that chloride cells appeared to decline in number over the summer in fish retained in freshwater, whereas seawater acclimated fish, at this time, had numerous well developed chloride cells. -- Wild anadromous smolts of the Exploits River stock had high branchial Na+-K+ ATPase activity and adapted to seawater without marked elevation of plasma sodium or chloride1 ion concentration. Mortality was high in LLxLL salmon during the course of exposure to seawater and the group exhibited elevated plasma ion concentrations. Induction of branchial Na+-K+ ATPase activity did not appear to lower plasma ion concentrations in LLxLL salmon exposed to seawater. It appears that genetic differences in smolting patterns occur in mature male salmon from anadromous populations. As well, differences appear to exist in adaptability to seawater among stocks of nonanadromous Atlantic salmon. Differences in smoltification patterns in anadromous and nod anadromous salmon are discussed in terms of the evolution of the different life history patterns observed in the two forms

Polymerase chain reaction (PCR) primers for the amplification of five nuclear introns in vertebrates

[Extract] Advancements in evolutionary genetics, as well as the conservation of biodiversity, increasingly require direct analyses of sequence variation in nuclear DNA. Recent studies indicate that nuclear introns have variabilities useful for both phylogenetics and population genetics (reviewed in Friesen 2000); however, use of introns is currently limited by the paucity of polymerase chain reaction (PCR) primers that have been demonstrated to have broad taxonomic utility (although several primers with less general or uncertain utilities have been published; reviewed in Friesen 2000). We have designed 30 general PCR primers for nuclear introns for vertebrates

Intron variation in marbled murrelets detected using analyses of single-stranded conformational polymorphisms

Combination of the targeted amplification of nuclear introns and the analysis of single-stranded conformational polymorphisms has the potential to provide an inexpensive, rapid, versatile and sensitive genetic assay for evolutionary studies and conservation. We are developing primers and protocols to analyse nuclear introns in vertebrates, and are testing them in a population genetic study of marbled murrelets Brachyramphus marmoratus. Here we present protocols and results for introns for aldolase B, α-enolase, glyceraldehyde-3-phosphate dehydrogenase and lamin A. Results suggest that this approach presents a potentially powerful method for detecting genetic variation within and among local populations and species of animals: (i) a variety of genes can be surveyed, including genes of special interest such as those involved in disease resistance; (ii) assays are rapid and relatively inexpensive; (iii) large numbers of genes can be assayed, enabling accurate estimation of variation in the total genome; (iv) almost any mutation can be detected in the genes amplified; (v) the exact nature of variation can be investigated by sequence analysis if desired; (vi) statistical methods previously developed for proteins and/or sequence data can be used; (vii) protocols can be easily transferred to other species and other laboratories; and (viii) assays can be performed on old or degraded samples, blood or museum skins, so that animals need not be killed. Results of analyses for murrelets support earlier evidence that North American and Asiatic subspecies represent reproductively isolated species, and that genetic differences exist among murrelets from different sites within North America

Population genetic structure and conservation of marbled murrelets (Brachyramphus marmoratus)

Marbled murrelets (Brachyramphus marmoratus) are coastal seabirds that nest from California to the Aleutian Islands. They are declining and considered threatened in several regions. We compared variation in the mitochondrial control region, four nuclear introns and three microsatellite loci among194 murrelets from throughout their range except Washington and Oregon. Significant population genetic structure was found: nine private control region haplotypes and three private intron alleles occurred at high frequency in the Aleutians and California; global estimates of FST or ΦST and most pairwise estimates involving the Aleutians and/or California were significant; and marked isolation-by-distance was found. Given the available samples, murrelets appear to comprise five genetic management units: (1) western Aleutian Islands, (2) central Aleutian Islands, (3) mainland Alaska and British Columbia, (4) northern California, and (5) central California

Physiological seawater adaptation in juvenile Atlantic salmon (Salmo salar) autumn migrants

1. About 25 % of juvenile Atlantic salmon (Salmo salar) migrating downstream in the River Frome in southern England do so in the autumn rather than in the spring. Here, we examine the physiological status of these fish with regard to those features that adapt them to sea water during the parr–smolt transformation (i.e. gill Na+K+ ATPase activity; the number, size and type of chloride cells on the gill lamellae; salinity tolerance and relative plasma thyroid levels). 2. Autumn migrants, and those fish which subsequently reside in the tidal reaches during the winter, are not sufficiently physiologically adapted to permit permanent or early, entry into the marine environment. 3. It is not known what proportion of autumn migrating fish survive and return to spawn as adults. If significant numbers do return, however, the production from tidal reach habitats must be taken into account in the development of salmon stock management strategies, especially monitoring and assessment programmes, and in the evaluation of factors affecting stocks