Some patterns of age and geographical variation in fish fecundity

Some patterns of age and geographical variation in fecundity indices were analyzed in three freshwater fishes (river perch, bream, and Sevan khramulya). A trend to increase in the ovarian relative weight and mature egg size with age has been revealed. Two species with a wide range (perch and bream) demonstrated a tendency to decrease in the ovarian relative weight and increase in the definitive oocyte weight in females of populations living in the geographical center of the range. The coefficient of correlation between the absolute individual fecundity and body weight of females was proposed as a population marker of the fish reproductive system.     

Follicle-stimulating hormone receptor in felids: intra- and interspecies variation

Assisted reproductive technologies are increasingly applied to support breeding efforts for many endangered felids. To explain the highly variable responses among felids to exogenous gonadotropins (FSH, eCG), we analyzed a 567bp fragment spanning a hyper-variable region of the FSH receptor in the domestic cat (catFSHR) and nine wild felid species/subspecies (felFSHR). Phylogenetic analysis indicated that the newly sequenced felFSHRs, together with the bear FSHR, belong to the carnivore group closely related to the ungulate clade. Within Felidae, genetic distances were 0.0089 +/- 0.0018 for nucleotide and 0.0183 +/- 0.0044 for amino acid (aa) sequences. In pairwise comparisons among catFSHR and all new felFSHRs, similarity ranged from 98.6 to 99.5% for nucleotides and from 97.4 to 98.9% for aa. Besides interspecies variability, intraspecies variation was also detected on both the cDNA and the protein level. There were no indications for an expression of tissue-specific isoforms of FSHR in testis and ovary.     

Chromatic aberration of a dipteran corneal lens

Summary The longitudinal chromatic aberration (variation in the position of focus with wavelength) of corneal facet lenses of the houseflyMusca domestica is measured directly. The result is shown to agree with that calculated using the thick-lens formulas, the measured lens parameters and the dispersion of the refractive index of the lenses, measured with an interference microscope. The longitudinal chromatic aberration between the two wavelengths of peak absorption of fly rhabdomeres (360 nm and 495 nm) is about 2.5 m and comparable to the depth of focus of the lens, assuming the lens to be diffraction limited. Chromatic aberration is therefore expected to have little effect on optical image quality in the fly; in particular the effect on the modulation transfer function at the receptor level and on the angular sensitivity of the rhabdomeres is insignificant.Abbreviations LCA longitudinal chromatic aberration - MTF modulation transfer function     

Seasonal variation and the immune response: a fish perspective

The environment in which an animal lives affects the physiology and psychology of that animal. The greater the distance from the equator the more profound this influence becomes, as the environment becomes more variable over the years. Temperature, photoperiod, precipitation and other environmental conditions, which are directly or indirectly controlled by the season, can affect an animal. It is becoming apparent that these conditions may impact on the immune system, and this can affect animal health. This review looks at the known mechanisms for transducing environmental cues and how these can affect immune parameters and function. The main focus is fish, especially in relation to aquaculture and the associated disease risks. Work on other animal classes is included for comparison.     

Intraspecific variation in the lens proteins

A review of the literature indicates that intraspecific variation among the lens proteins (crystallins) is almost invariably quantitative rather than qualitative. Lens extracts were examined from inbred strains of the laboratory mouse, rat, and guinea pig and from domestic breeds of sheep. Differences in the mobilities of protein bands after electrophoresis in polyacrylamide gels were never found to be greater than the variation observed when a sample was repeatedly subjected to electrophoresis. Differences, however, were observed between widely separated populations of the bank vole (Clethrionomys glareolus). In bank voles and mice, there were variations in the intensities of bands. Electrophoresis of extracts in the presence of 6 m urea indicated that there were no major differences between six mouse strains in the subunits constituting their - and -crystallins. More detailed examination of -crystallins from two mouse strains by isoelectric focusing and amino acid analysis supported this conclusion.This work was carried out while one of the authors (T.H.D.) was supported by a Medical Research Council Research Studentship and a European Molecular Biology Organisation Fellowship. A grant from the Edinburgh University Weir Memorial Fund allowed the collection of some of the Yugoslavian bank voles.     

Analysis of copy number variation using quantitative interspecies competitive PCR

Over recent years small submicroscopic DNA copy-number variants (CNVs) have been highlighted as an important source of variation in the human genome, human phenotypic diversity and disease susceptibility. Consequently, there is a pressing need for the development of methods that allow the efficient, accurate and cheap measurement of genomic copy number polymorphisms in clinical cohorts. We have developed a simple competitive PCR based method to determine DNA copy number which uses the entire genome of a single chimpanzee as a competitor thus eliminating the requirement for competitive sequences to be synthesized for each assay. This results in the requirement for only a single reference sample for all assays and dramatically increases the potential for large numbers of loci to be analysed in multiplex. In this study we establish proof of concept by accurately detecting previously characterized mutations at the PARK2 locus and then demonstrating the potential of quantitative interspecies competitive PCR (qicPCR) to accurately genotype CNVs in association studies by analysing chromosome 22q11 deletions in a sample of previously characterized patients and normal controls.     

Intra- and interspecies variation among Bari-1 elements of the melanogaster species group.

We have investigated the distribution of sequences homologous to Bari-1, a Tc1-like transposable element first identified in Drosophila melanogaster, in 87 species of the Drosophila genus. We have also isolated and sequenced Bari-1 homologues from D. simulans, D. mauritiana, and D. sechellia, the species constituting with D. melanogaster the melanogaster complex, and from D. diplacantha and D. erecta, two phylogenetically more distant species of the melanogaster group. Within the melanogaster complex the Bari-1 elements are extremely similar to each other, showing nucleotide identity values of at least 99.3%. In contrast, Bari-1-like elements from D. diplacantha and D. erecta are on average only 70% similar to D. melanogaster Bari-1 and are usually defective due to nucleotide deletions and/or insertions in the ORFs encoding their transposases. In D. erecta the defective copies are all located in the chromocenter and on chromosome 4. Surprisingly, while D. melanogaster Bari-1 elements possess 26-bp inverted terminal repeats, their D. diplacantha and D. erecta homologues possess long inverted terminal repeats similar to the terminal structures observed in the S elements of D. melanogaster and in several other Tc1-like elements of different organisms. This finding, together with the nucleotide and amino acid identity level between D. diplacantha and D. erecta elements and Bari-1 of D. melanogaster, suggests a common evolutionary origin and a rapid diversification of the termini of these Drosophila Tc1-like elements.     

Eco-immunology of fish invasions: the role of MHC variation

The relationship between invaders and the pathogens encountered in their new environment can have a large effect on invasion success. Invaders can become free from their natural pathogens and reallocate costly immune resources to growth and reproduction, thereby increasing invasion success. Release from enemies and relaxation of selective pressures could render newly founded populations more variable at immune-related genes, such as the major histocompatibility complex (MHC), particularly when they have different origins. Using rainbow and brown trout, two of the world’s most successful fish invaders, we tested the general hypothesis that invaders should display high intrapopulation immunogenetic diversity and interpopulation divergence, due to the interplay between genetic drift and successive waves of genetically divergent introductions. We analysed genetic diversity and signatures of selection at the MHC class II β immune-related locus. In both species, MHC diversity (allelic richness and heterozygosity) for southern hemisphere populations was similar to values reported for populations at their native range. However, MHC functional diversity was limited, and population immunogenetic structuring weaker than that observed using neutral markers. Depleted MHC functional diversity could reflect a decrease in immune response, immune-related assortative mating or selection for resistance to newly encountered parasites. Given that the role of MHC diversity in the survival of these populations remains unclear, depleted functional diversity of invasive salmonids could compromise their long-term persistence. A better understanding of the eco-immunology of invaders may help in managing and preventing the impact of biological invasions, a major cause of loss of biodiversity worldwide.     

Adaptive nature of interspecies variation of histone H1 in insects

Summary An electrophoretic analysis of histone H1 and its fragments was carried out for several orders of insects. A total of more than 500 histone H1 variants were examined. For some of them a study of general molecular structure was performed by the method of incomplete succinylation. The molecular length of the fragment containing the C-terminal domain presumably responsible for chromatin condensation was found to be highly variable. The variance of the logarithm of the electrophoretic mobility of H1, which reflects its molecular length, was estimated for seven insect orders. There was no relationship between this variance and the evolutionary age of an order. On the other hand, the variance turned out to correlate strongly with the recent species number in the order, indicating that the accumulation of variation in H1 molecular length was in line with the general intensity of adaptive processes in the orders. This result seems to provide evidence for an adaptive mode of the evolution of the molecular length of H1. The possible role of H1 variability in adaptive evolution is discussed.     

Clonal and non-clonal chromosome aberrations and genome variation and aberration.

The theoretical view that genome aberrations rather than gene mutations cause a majority of cancers has gained increasing support from recent experimental data. Genetic aberration at the chromosome level is a key aspect of genome aberration and the systematic definition of chromosomal aberrations with their impact on genome variation and cancer genome evolution is of great importance. However, traditionally, efforts have focused on recurrent clonal chromosome aberrations (CCAs). The significance of stochastic non-clonal chromosome aberrations (NCCAs) is discussed in this paper with emphasis on the simple types of NCCAs that have until recently been considered "non-significant background". Comparison of various subtypes of transitional and late-stage CCAs with simple and complex types of NCCAs has uncovered a dynamic relationship among NCCAs, CCAs, overall genomic instability, and karyotypic evolution, as well as the stochastic nature of cancer evolution. Here, we review concepts and methodologies to measure NCCAs and discuss the possible causative mechanism and consequences of NCCAs. This study raises challenging questions regarding the concept of cancer evolution driven by stochastic chromosomal aberration mediated genome irregularities that could have repercussions reaching far beyond cancer and organismal genomes.     

Ventilatory threshold: measurement and variation with age

The purpose of this study is to present measurement of ventilatory threshold (VeT) and maximal oxygen uptake (VO2max) in a large group of predominantly older subjects using a bicycle ergometer and an automated measuring system. One hundred and twenty-seven healthy elderly subjects (mean age: 68) and 44 young and middle-aged subjects (mean age: 39) underwent a maximal exercise test with breath-by-breath measurement of ventilation and gas exchange variables. Ventilatory threshold was determined by visual inspection of the breakpoints in the VE/VO2 and PETO2 data curves. Additional measures were made in a subset of subjects to determine the reproducibility and interobserver variability of VeT and the relationship between VeT and the venous lactate threshold (LaT). Day-to-day reproducibility of VeT was good with a mean difference in VO2 at VeT on two occasions of 40.23 +/- 125 ml/min. Interobserver variability was low (intraclass correlation coefficient of r = 0.941) and VeT was found to correlate to LaT (r = 0.79, P less than 0.05) with LaT occurring a mean 2.3 min after VeT. VeT declined significantly with age in both males and females but less rapidly than VO2max. Both VO2max and VeT were found to vary with age, sex, height, and weight in a stepwise multiple-linear regression analysis. Age-associated changes in skeletal muscle composition may be in part responsible for the less precipitous decline in VeT with age compared with VO2max.     

Truncated PrP(c) in mammalian brain: interspecies variation and location in membrane rafts

A key molecular event in prion diseases is the conversion of cellular prion protein (PrP(c)) into an abnormal misfolded conformer (PrP(sc)). The PrP(c) N-terminal domain plays a central role in PrP(c) functions and in prion propagation. Because mammalian PrP(c) is found as a full-length and N-terminally truncated form, we examined the presence and amount of PrP(c) C-terminal fragment in the brain of different species. We found important variations between primates and rodents. In addition, our data show that the PrP(c) fragment is present in detergent-resistant raft domains, a membrane domain of critical importance for PrP(c) functions and its conversion into PrP(sc).     

Genetic architecture of hybrid male sterility in Drosophila: analysis of intraspecies variation for interspecies isolation

Background

The genetic basis of postzygotic isolation is a central puzzle in evolutionary biology. Evolutionary forces causing hybrid sterility or inviability act on the responsible genes while they still are polymorphic, thus we have to study these traits as they arise, before isolation is complete.

Methodology/Principal Findings

Isofemale strains of D. mojavensis vary significantly in their production of sterile F₁ sons when females are crossed to D. arizonae males. We took advantage of the intraspecific polymorphism, in a novel design, to perform quantitative trait locus (QTL) mapping analyses directly on F₁ hybrid male sterility itself. We found that the genetic architecture of the polymorphism for hybrid male sterility (HMS) in the F₁ is complex, involving multiple QTL, epistasis, and cytoplasmic effects.

Conclusions/Significance

The role of extensive intraspecific polymorphism, multiple QTL, and epistatic interactions in HMS in this young species pair shows that HMS is arising as a complex trait in this system. Directional selection alone would be unlikely to maintain polymorphism at multiple loci, thus we hypothesize that directional selection is unlikely to be the only evolutionary force influencing postzygotic isolation.     

Rocky intertidal fish communities of California: temporal and spatial variation

Synopsis We examined data from our own and published collections of intertidal and shallow littoral fishes of the North American Pacific Coast with respect to temporal and spatial trends in species composition and dominance. We compared (1) recent and past intertidal collections made five and seven years apart, respectively, for two California localities, (2) intertidal collections from twelve localities in California, Oregon, and British Columbia, and (3) intertidal versus subtidal collections at one California locality. Temporal comparisons indicated substantially lower abundance of the cottid Oligocottus snyderi at two California localities during 1984, at one locality due to depressed abundance of young. Interannual differences in abundances suggested that other tidepool fish assemblages undergo significant changes as well. Geographical comparisons indicated general similarity in species composition, with cottids predominating in tidepools although several other families also were well represented (e.g., Stichaeidae, Scorpaenidae). Eel-shaped stichaeids and pholids occurred at high densities in exposed boulder fields. Both the tidepool and boulder field assemblages showed north-south changes in species abundances. Comparison of collections from the intertidal and subtidal zones at one California locality demonstrated that fishes of these habitats form two essentially distinct assemblages, with most species restricted to or concentrated in one or the other habitat.     

River regulation and fish larvae: variation through space and time

1. Patterns in abundance and distribution of larval fish in a heavily regulated and a mildly regulated Australian lowland river were compared over four breeding seasons to gain some insight into how river regulation affects fish populations.
2. Larvae from a total of 13 species from nine families were recorded from the two rivers. The mildly regulated Broken River supported twice as many species as the heavily regulated Campaspe River. The two rivers shared three introduced species but only two native species. The dominant species in the Campaspe was not found in the Broken River.
3. The two most abundant species in the Campaspe were classified as `opportunists'. They are small, short-lived species, which spawn for up to 9 months, encompassing extremes in temperature and flow. The extended spawning period may place a subset of larvae in optimal conditions for recruitment and is hypothesised as being the key to the success of these species.
4. Most species spawned each year, despite large interannual variation in flow and temperature conditions. Poor recruitment over several decades, rather than a failure to spawn, is considered the most likely explanation for differences in the larval fish faunas between the two rivers.
5. The highly regulated section of the Campaspe River downstream of the regulating impoundment is thought to provide suboptimal habitat conditions for larvae relative to the less regulated downstream sections.
6. The timing of occurrence of larvae of the dominant species varied by breeding season and may be the result of flexibility in the timing of spawning.     

MHC variation and tissue transplantation in fish

Major histocompatibility complex (MHC) genes were originally discovered because of their role in tissue rejection in mammals and have subsequently been implicated in the incidence of autoimmune diseases and resistance to infectious diseases. Here we present the first demonstration that a gene defined by molecular sequence in the fish MHC, specifically a class II locus, plays an important role in tissue rejection. This effect in the endangered Gila topminnows appears to be additive and depends on the number of MHC alleles shared between the host and the recipient fish of the scale transplants. In addition, there was lower success of scale transplants in MHC-matched individuals in a population with high microsatellite variation than in a population with low variation. This suggests that other loci, presumably other MHC loci, play a significant role in transplantation success in fishes, as they do in mammals.     

Phylogenetic community structure: temporal variation in fish assemblage

Hypotheses about phylogenetic relationships among species allow inferences about the mechanisms that affect species coexistence. Nevertheless, most studies assume that phylogenetic patterns identified are stable over time. We used data on monthly samples of fish from a single lake over 10 years to show that the structure in phylogenetic assemblages varies over time and conclusions depend heavily on the time scale investigated. The data set was organized in guild structures and temporal scales (grouped at three temporal scales). Phylogenetic distance was measured as the mean pairwise distances (MPD) and as mean nearest‐neighbor distance (MNTD). Both distances were based on counts of nodes. We compared the observed values of MPD and MNTD with values that were generated randomly using null model independent swap. A serial runs test was used to assess the temporal independence of indices over time. The phylogenetic pattern in the whole assemblage and the functional groups varied widely over time. Conclusions about phylogenetic clustering or dispersion depended on the temporal scales. Conclusions about the frequency with which biotic processes and environmental filters affect the local assembly do not depend only on taxonomic grouping and spatial scales. While these analyzes allow the assertion that all proposed patterns apply to the fish assemblages in the floodplain, the assessment of the relative importance of these processes, and how they vary depending on the temporal scale and functional group studied, cannot be determined with the effort commonly used. It appears that, at least in the system that we studied, the assemblages are forming and breaking continuously, resulting in various phylogeny‐related structures that makes summarizing difficult.     

Haematological assessment of the effects of the anaesthetic MS 222 in natural and neutralized form in three freshwater fish species: interspecies differences

Interspecies haematological differences to MS 222 and neutralized MS 222 anaesthesia were investigated in Sarotherodon mossambicus, Cyprinus carpio and Salmo gairdneri acclimated under identical laboratory conditions. Anaesthesia with MS 222 resulted in a 'chemical stress' in all fish, as was evident from changes in the haematological profiles of the animals. Such species specific variations in the haematology persisted throughout the whole experiment protocol which employed different concentrations of the anaesthetic. The use of neutralized MS 222, whereby aquarium water quality remained unchanged, improved the haematological profile. Possible reasons for the interspecies differences observed are discussed.