The Escherichia coli low-copy-number plasmid R1 contains a segregation machinery composed of parC, ParR and parM. The R1 centromere-like site parC contains two separate sets of repeats. By atomic force microscopy (AFM) we show here that ParR molecules bind to each of the 5-fold repeated iterons separately with the intervening sequence unbound by ParR. The two ParR protein complexes on parC do n...

While nonanadromous males (stream-resident and/or mature male parr) contribute to reproduction in anadromous salmonids, little is known about their impacts on key population genetic parameters. Here, we evaluated the contribution of Atlantic salmon mature male parr to the effective number of breeders (Nb) using both demographic (variance in reproductive success) and genetic (linkage disequilibr...

The crypsis hypothesis of salmonid parr coloration and behaviour is evaluated in light ot the criteria for protective resemblance. A review of the literature indicates that salmonid parr coloration and behaviour correspond to a cryptic interpretation. Experiments on coho salmon, Oncorhynchus kisutch, parr substrate colour preference indicate that the behavioural correlate of appropriate backgro...

In lymphoid neoplasia, molecular assays to confirm clonality rely on the fact that lymphoid cells normally contain DNA regions with unique sequences, resulting from recombination of the V, D, and J genes. The purpose of this study was to determine the utility of polymerase chain reaction (PCR) for antigen receptor rearrangements (PARR) for molecular staging and predicting prognosis in canine ly...

Juvenile stages of rainbow trout, smaller parr and older juveniles, termed smolts, show differences in red muscle contractile properties: parr red muscle has faster kinetics and a faster maximum shortening velocity than smolt red muscle. A developmental reduction in the number of MHC isoforms as detected by SDS-PAGE between parr and smolt has also been observed. To investigate whether this shif...

Nocturnal underwater counts of Atlantic salmon Salmo salar parr were made on four consecutive occasions (two lunar cycles, samplings at both the full and new moon) at four 40m long sites in the Sainte-Marguerite River, Québec, Canada, between 30 June and 14 August 2003. Atlantic salmon parr counts did not differ significantly between moon phases. Cloud cover ranged from 0 to 100% during the stu...

Episodic acidification resulting in increased acidity and inorganic aluminum (Al(i)) is known to impact anadromous salmonids and has been identified as a possible cause of Atlantic salmon population decline. Sensitive life-stages such as smolts may be particularly vulnerable to impacts of short-term (days-week) acid/Al exposure, however the extent and mechanism(s) of this remain unknown. To det...

Successful re-introduction of captively-bred Atlantic salmon (Salmo salar) populations to their historical natal river systems may be difficult until patterns of local genetic adaptation by the parr stage are better understood. Divergence in parr size, shape, pigmentation, and SNP allele frequencies was compared for five endangered salmon populations from the Bay of Fundy. Differences among pop...

During normal development, rainbow trout undergo a shift in red muscle contraction kinetics and swimming kinematics. Young trout parr have faster muscle kinetics and faster tailbeat frequency during swimming than older, larger juvenile trout. In this study, the thyroid hormone thyroxine (T(4)) was used to induce these changes in trout parr. This allowed a comparison of swimming kinematics, thro...

In order to elucidate the developmental basis for smolting, Atlantic salmon, Salmo salar, parr (b11.5 cm) and smolts (N12.5 cm) were exposed to natural daylength (LDN) and increased daylength (LD16:8) starting in late February and gill Na,K– ATPase activity and circulating hormone levels monitored from January to May. Gill Na,K–ATPase activity remained low and constant in both groups of parr. I...