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PubMed1993

Aggressive behaviour in immature captive Nile crocodiles, Crocodylus niloticus, in relation to feeding.

This study presents five aspects of aggressive behaviour in juvenile Nile crocodiles, Crocodylus niloticus, as observed in five cohorts of 6-18 month-old animals. During this period, the animals grew from a range of 35-55 cm, to a range of 65-115 cm. 1) Stock density related to aggression: decrease in density resulted in significant decrease in the frequency of agonistic events, with 0.64 events/100 crocodiles/min observed in a density of 6.7 crocodiles/m2, compared to 0.26 events/100 crocodiles/min observed in a density of 4.7 crocodiles/m2. 2) Aggression during feeding: in all five groups, there was a significantly higher level of aggression during feeding times. 3) Aggression related to body size: the largest crocodiles were the most aggressive group in agonistic events, mainly against the smallest ones. The largest group, the medium sized, was the least involved in agonistic events. 4) Aggression related to food preference: crocodile food preference was live fish > live chicks > dead fish > ground meat. Except for one food type (live chicks), a significant (p < 0.05) correlation was found between food preference and feeding related aggression in the prey diet groups. 5) Aggression related to an artificial selection for size: removal of the largest crocodiles (which formed 30% of the stock) from the population caused a dramatic decrease in all forms of aggressive behaviour.

Aggression↗
PubMedDate not supplied

Visual pigments and oil droplets in genetically manipulated and carotenoid deprived quail: a microspectrophotometric study.

The spectral absorbances of visual pigments and retinal oil droplets were studied in three groups of Japanese quail (Coturnix coturnix japonica): an unselected control population and two artificially selected strains that exhibited different early approach preferences between blue and red stimuli. The oil droplets were examined with and without prior carotenoid deprivation. Four cone pigments and five oil droplet types were identified, resembling those in other avian species. Carotenoid deprivation eliminated all pigmentation detectable in oil droplets by microspectrophotometry. Placement of chicks on normal diet gradually reintroduced normal pigmentation within the span of about a week. No statistically significant differences were found between normal and genetically selected birds in either visual pigments or oil droplet types, or in their relative proportions. It is concluded that differences in the early colour preferences of quail are unlikely to be a result of variation in the spectral properties of their photoreceptors.

Animals↗
PubMed1983

Unequal exchanges and the coevolution of X and Y rDNA arrays in Drosophila melanogaster.

We have examined the molecular basis of the response of individuals of D. melanogaster to artificial selection for high and low abdominal bristles. By monitoring the fate of particular rDNA spacer length variants associated with individually isolated X and Y chromosomes, we show that flies from the low bristle number selection lines have undergone an unequal exchange between the X and Y rDNA arrays. Such exchanges result in translocations between X and Y chromosomes, visualised as X.Y compound chromosomes at mitosis. Transfer of few copies of a length variant between X and Y indicates a clustering of variants. Flies that have reverted back to wild-type seemingly have undergone a second unequal exchange, giving rise to a compound X.Y chromosome containing Y rDNA of normal amounts. Unequal exchanges between X and Y rDNA arrays could contribute to the observed coevolution of rDNA sequences on these chromosomes. The biological significance of this outcome is discussed.

Animals↗
PubMed1980

Genetics in the analysis of behaviour.

Behaviour genetics has developed rapidly in the last two decades and has now gone far beyond the stage of merely measuring the extent to which individual differences on a particular behaviour can be attributed to genetic factors. This paper discusses the uses to which genetics can be put in efficient experimental design, in determining the generality of results and, most importantly, in the simultaneous analysis of several behaviours and their relationship to each other and to physical and biochemical parameters. Because the principles of genetics apply to all organisms, the first animal discussed is Drosophila, the vinegar fly, which is a vital tool in genetics but which has met with scant attention among psychologists. Drosophila has some unique advantages such as the sex mosaic technique for studying sexual behaviour, but most of the discussion concerns learning and the extent to which parallels can be found between Drosophila and the vertebrates, both in terms of process and of genetic control. It is demonstrated how strain differences and the response to artificial selection can distinguish between learning and other components of behaviour. Drosophila are also used to explain how the type of genetic control can suggest the way in which natural selection acts upon the particular behaviour and further examples from rodents are discussed to show that this is a general result across species. There are many inbred strains and selection lines of mice and rats and examples from a wide range of behaviours illustrate the advantages of using such stocks. The concept of the 'behavioural phenotype' is explained, where genetic differences on a wide range of behaviours are considered, rather than just focusing on one behaviour or one response to a particular drug or environmental treatment. Many different aspects of open-field behaviour, learning and mother-infant interaction are used as examples of this concept. The extent of genotype-environmental interaction is considered, since the possibility that each genotype will have a unique response to a brief discussion of human behaviour genetics, since here again the concern is not just with the trivial question of measuring 'heritability', but rather with how such information can be used to understand behaviour. The final suggestion is that psychology may gain by having more contact not only with geneticists, but also with the ecologists concerned with the significance of behavioural differences in the wild.

Aggression↗
PubMed1993

Phylogenetic relationships among wine yeast strains based on electrophoretic whole-cell protein patterns.

In the present work, a phylogenetic study based on protein electrophoretic profiles of Saccharomyces strains isolated from different Spanish wine regions has been carried out. Qualitative differences between the protein electrophoregrams were found at inter- and intraspecific level, but not between electrophoregrams of strains isolated at the same ecosystem. The numerical analysis of these results allowed us to conclude that intraspecific relationships are determined by ecological factors, as well as human influences (dispersion and artificial selection). A correlation between ecological and/or geographical origin and the relationships among strains was observed.

Cluster Analysis↗
PubMed1996

Biosynthetic enzymes regulating ratios of sex pheromone components in female redbanded leafroller moths.

Changes in key enzymes in the biosynthetic pathways of sex pheromone components can produce differences in component ratios and structures. The sex pheromone communication system is critical to reproduction and the maintenance of a species and so changes in this system can play a major role in the speciation process. Artificial selection of female redbanded leafroller moths that produced either higher or lower ratios of 14-/12-carbon pheromone components was used to study how the biosynthetic pathways were affected in the high and low populations. The results showed that the chain shortening enzymes were selective for the (E) isomer and so left the 14-carbon acyl intermediates enriched in the (Z) isomer. Thus, the high population, which has a higher amount of 12-carbon components, also has a lower ratio of E11-/Z11-14:OAc pheromone components. The data also suggested that chain shortening occurred prior to reduction and acetylation of the 14-carbon components. These changes are not sufficient to isolate the redbanded leafroller populations, but we discuss some cases where significant changes in pheromone component ratios are affected by the chain-shortening enzymes.

Acetyltransferases↗
PubMed2006

Sexual dimorphism in hybrids rats.

Laboratory rat strains descend from Wistar rats as a consequence of artificial selection. Previously we reported that the medial posterior division of the bed nucleus of the stria terminalis (BSTMP) was sexually dimorphic in Wistar and Long-Evans strains while the medial anterior division (BSTMA) and the locus coeruleus (LC) only showed sex differences in the ancestor Wistar strain. The lateral posterior division (BSTLP) was isomorphic in both strains. The present work studies the number of neurons in the BSTMP, BSTMA, BSTLP and LC of male and female Wistar and Long-Evans rats (F(0)) and their hybrid F(1) and F(2) generations. The BSTMP is sexually dimorphic in the F(0), F(1) and F(2) generations while sex differences in the LC are only seen in F(0) Wistar rats but not in the F(0) Long-Evans or the F(1) and F(2) hybrid generations. Sex differences in the BSTMA are seen in F(0) Wistar but not in F(0) Long-Evans rats and completely disappear in the F(2) generations. The number of neurons in the LC of both males and females decreased in heterozygotic individuals (F(1)) but increased in homozygotic (F(2)). However, the number of neurons in the BSTMP changes significantly over the generations, although the ratio of neurons (female/male) is stable and unaffected in homo- or heterozygosis. Thus, the mechanism that regulates the neuronal female/male ratio would be different from the one that controls the number of neurons. The facts that sex differences in the BSTMP are not affected by homo- or heterozygosis and that they are seen in several mammalian orders suggest the existence of a "fixed" type of brain sex differences in the Mammalia Class.

Animals↗
PubMed2005

Thermodynamical interpretation of evolutionary dynamics on a fitness landscape in an evolution reactor, II.

In our previous report [Aita, T., Morinaga, S., Hosimi, Y., 2004. Thermodynamical interpretation of evolutionary dynamics on a fitness landscape in an evolution reactor I. Bull. Math. Biol. 66, 1371-1403], an analogy between thermodynamics and adaptive walks on a Mt. Fuji-type fitness landscape in an artificial selection system was presented. Introducing the 'free fitness' as the sum of a fitness term and an entropy term and 'evolutionary force' as the gradient of free fitness on a fitness coordinate, we demonstrated that the adaptive walk (=evolution) is driven by the evolutionary force in the direction in which free fitness increases. In this report, we examine the effect of various modifications of the original model on the properties of the adaptive walk. The modifications were as follows: first, mutation distance d was distributed obeying binomial distribution; second, the selection process obeyed the natural selection protocol; third, ruggedness was introduced to the landscape according to the NK model; fourth, a noise was included in the fitness measurement. The effect of each modification was described in the same theoretical framework as the original model by introducing 'effective' quantities such as the effective mutation distance or the effective screening size.

Algorithms↗
PubMed2006

Evolutionary genetics of juvenile hormone and ecdysteroid regulation in Gryllus: a case study in the microevolution of endocrine regulation.

During the past 15 years the first detailed synthesis of endocrinology and population genetics has begun, in which natural genetic variations for endocrine regulators have been characterized, almost exclusively in species of the cricket genus Gryllus. Artificial selection studies have documented that regulators of the juvenile hormone titer can rapidly evolve and exhibit levels of genetic variability similar to other physiological traits. Strong genetic correlations exist between some but not all regulators of the JH titer during the juvenile stage. No genetic correlation exists between regulators functioning in juvenile and adult stages, and thus, endocrine regulation can evolve independently in these stages. Genetic variation in the JH titer, the ecdysteroid titer, and JHE activity, in adult and juvenile stages, have been documented in genetic stocks of wing-polymorphic crickets; morph-specific differences in these endocrine traits are potentially responsible for genetically based differences in aspects of wing and flight muscle development, adult egg production, and adult dispersal. An unexpected morph-specific, genetic polymorphism for a circadian rhythm for the JH titer was observed in both the laboratory and field. Few comparable studies exist in non-Gryllus species, in which in vivo endocrine-genetic variation has been directly quantified using reliable analytical methods; many reported cases of endocrine variation in these species have been obtained using an inappropriate method and thus should be considered unsubstantiated. Obtaining basic information on the characteristics of natural genetic variation for endocrine regulators still remains one of the most important tasks of the fledgling subdiscipline of evolutionary endocrinology. Single gene endocrine mutants in Drosophila are promising candidates for investigating molecular-genetic variation in natural populations. Future studies should also focus on endocrine traits studied in the field and geographic variation in endocrine regulation.

Animals↗
PubMed2006

Environmental rearing conditions produce forebrain differences in wild Chinook salmon Oncorhynchus tshawytscha.

Recent studies suggest that hatchery-reared fish can have smaller brain-to-body size ratios than wild fish. It is unclear, however, whether these differences are due to artificial selection or instead reflect differences in rearing environment during development. Here we explore how rearing conditions influence the development of two forebrain structures, the olfactory bulb and the telencephalon, in juvenile Chinook salmon (Oncorhynchus tshawytscha) spawned from wild-caught adults. First, we compared the sizes of the olfactory bulb and telencephalon between salmon reared in a wild stream vs. a conventional hatchery. We next compared the sizes of forebrain structures between fish reared in an enriched NATURES hatchery and fish reared in a conventional hatchery. All fish were size-matched and from the same genetic cohort. We found that olfactory bulb and telencephalon volumes relative to body size were significantly larger in wild fish compared to hatchery-reared fish. However, we found no differences between fish reared in enriched and conventional hatchery treatments. Our results suggest that significant differences in the volume of the olfactory bulb and telencephalon between hatchery and wild-reared fish can occur within a single generation.

Animals↗
PubMed2006

Plant genome organisation and diversity: the year of the junk!

Having gained a thorough understanding of the structure and organization of model plant genomes, such as those of Arabidopsis thaliana and rice, we have now started to investigate the most interesting aspect of genome structure - its variations. Variation in DNA sequence is responsible for the genetic component of phenotypic variation (i.e. the component upon which both natural and artificial selection act). Recent studies have started to shed light on sequence variation outside of the genic regions, owing mainly to large insertion/deletion (indel) polymorphisms caused by the presence or absence of transposable elements of different classes. In addition to long terminal repeat retrotransposons, DNA transposons have been shown to be responsible for these polymorphisms. These comprise Helitrons, CACTA and Mu-like elements that are capable of acquiring and piecing together fragments of plant genes and are often expressed. Future analyses of the functional roles of intergenic sequence variation will tell us if we will need to pay more attention not only to genes, but also to the 'junk' DNA surrounding them.

DNA, Intergenic↗
PubMed2005

Biodemography of a long-lived tephritid: reproduction and longevity in a large cohort of female Mexican fruit flies, Anastrepha ludens.

Age of sexual maturity, daily and lifetime reproductive rates, and life span were recorded in a laboratory cohort of Mexican fruit flies consisting of over 1100 females maintained individually. The results revealed that, relative to the medfly, the Mexfly is slower maturing (14 vs 17 days), more fecund (1400 vs 650-1100 eggs/female), and longer lived (50 vs 35 days). The results reinforced the generality of several earlier findings on the medfly including the deceleration of mortality at older ages and the weakness of the correlation between the rate of egg laying at early ages and both subsequent reproduction and remaining longevity. Discussion includes perspectives on the role of artificial selection in shaping the demographic traits of the mass-reared strain of Mexfly used in this study, as well as the overall significance of large scale biodemographic studies in understanding aging and longevity.

Aging↗
PubMed2007

Differential role of the 5-HT1A receptor in aggressive and non-aggressive mice: an across-strain comparison.

Differential role of the 5-HT(1A) receptor in aggressive and non-aggressive mice: an across-strain comparison. PHYSIOL BEHAV 00(0) 000-000, 2006. According to the serotonin (5-HT)-deficiency hypothesis of aggression, highly aggressive individuals are characterized by low brain 5-HT neurotransmission. Key regulatory mechanisms acting on the serotonergic neuron involve the activation of the somatodendritic inhibitory 5-HT(1A) autoreceptor (short feedback loop) and/or the activation of postsynaptic 5-HT(1A) receptors expressed on neurons in cortico-limbic areas (long feedback loop). In this study, we examined whether low serotonin neurotransmission is associated with enhanced 5-HT(1A) (auto)receptor activity in highly aggressive animals. Male mice (SAL-LAL, TA-TNA, NC900-NC100) obtained through different artificial-selection breeding programs for aggression were observed in a resident-intruder test. The prefrontal cortex level of 5-HT and its metabolite 5-HIAA were determined by means of HPLC. The activity of the 5-HT(1A) receptors was assessed by means of the hypothermic response to the selective 5-HT(1A) agonists S-15535 (preferential autoreceptor agonist) and 8-OHDPAT (full pre- and postsynaptic receptor agonist). Highly aggressive mice had lower serotonin levels in the prefrontal cortex and two out of three aggressive strains had higher 5-HT(1A) (auto)receptor sensitivity. The results strengthen the validity of the serotonin-deficiency hypothesis of aggression and suggest that chronic exaggerated activity of the 5-HT(1A) receptor may be a causative link in the neural cascade of events leading to 5-HT hypofunction in aggressive individuals.

Aggression↗
PubMed2006

Phylogenetic fragrance patterns in Nicotiana sections Alatae and Suaveolentes.

We analyzed floral volatiles from eight tobacco species (Nicotiana; Solanaceae) including newly discovered Brazilian taxa (Nicotiana mutabilis and "Rastroensis") in section Alatae. Eighty-four compounds were found, including mono- and sesquiterpenoids, nitrogenous compounds, benzenoid and aliphatic alcohols, aldehydes and esters. Floral scent from recent accessions of Nicotiana alata, Nicotiana bonariensis and Nicotiana langsdorffii differed from previously published data, suggesting intraspecific variation in scent composition at the level of biosynthetic class. Newly discovered taxa in Alatae, like their relatives, emit large amounts of 1,8-cineole and smaller amounts of monoterpenes on a nocturnal rhythm, constituting a chemical synapomorphy for this lineage. Fragrance data from three species of Nicotiana sect. Suaveolentes, the sister group of Alatae, (two Australian species: N. cavicola, N. ingulba; one African species: N. africana), were compared to previously reported data from their close relative, N. suaveolens. Like N. suaveolens, N. cavicola and N. ingulba emit fragrances dominated by benzenoids and phenylpropanoids, whereas the flowers of N. africana lacked a distinct floral scent and instead emitted only small amounts of an aliphatic methyl ester from foliage. Interestingly, this ester also is emitted from foliage of N. longiflora and N. plumbaginifolia (both in section Alatae s.l.), which share a common ancestor with N. africana. This result, combined with the synapomorphic pattern of 1,8 cineole emission in Alatae s.s., suggests that phylogenetic signal explains a major component of fragrance composition among tobacco species in sections Alatae and Suaveolentes. At the intraspecific level, interpopulational scent variation is widespread in sect. Alatae, and may reflect edaphic specialization, introgression, local pollinator shifts, genetic drift or artificial selection in cultivation. Further studies with genetically and geographically well-defined populations are needed to distinguish between these possibilities.

Cyclohexanols↗
PubMed2006

Simple sequence repeats as advantageous mutators in evolution.

Simple sequence repeats (SSRs) often serve to modify genes with which they are associated. The influence of SSRs on gene regulation, transcription and protein function typically depends on the number of repeats, while mutations that add or subtract repeat units are both frequent and reversible. SSRs thus provide a prolific source of quantitative and qualitative variation. Over the past decade, researchers have found that this spontaneous variation has been tapped by natural and artificial selection to adjust almost every aspect of gene function. These studies support the hypothesis that SSRs, by virtue of their special mutational and functional qualities, have a major role in generating the genetic variation underlying adaptive evolution.

Animals↗
PubMed2004

Japanese domesticated chickens have been derived from Shamo traditional fighting cocks.

With the aim of elucidating the evolutionary origin of Japanese domesticated chickens, this study evolutionarily analyzed 85 chicken mtDNA sequences. Thirty-four various ornamental chickens, 42 fighting cocks (Shamo), and nine long-crowing chickens (Naganakidori) were included. Of the Shamo, 18 were sampled from Okinawa, while the remaining 24 were collected in other islands around Japan. In addition, three Southeast Asian Junglefowls were used as a reference to determine the common ancestor of Japanese domesticated chickens. A phylogenetic tree was constructed for the 88 mtDNA sequences revealing that the Shamo group from Okinawa clearly diverged from the other Japanese domesticated chickens studied. This strongly suggests that all Japanese domesticated chickens, including the ornamental varieties and Naganakidori, derived from the ancestors of the Shamo in Okinawa. To create novel varieties of ornamental chickens, intensive artificial selection is imposed on ancestral Shamo populations, resulting in profoundly differentiated Japanese domesticated chickens.

Animals↗
PubMed2003

Is a wild mammal kept and reared in captivity still a wild animal?

This study compared domestic guinea pigs (Cavia aperea f. porcellus; DGP) and two different populations of the wild cavy (Cavia aperea), its ancestor, to examine whether rearing of wild mammals in captivity affects their behavior and physiological stress responses. One population of wild cavies consisted of wild-trapped animals and their first laboratory-reared offspring (WGP-1). The animals of the other population were reared in captivity for about 30 generations (WGP-30). The spontaneous behavior of each of six groups of WGP-1 and WGP-30 and nine groups of DGP, each consisting of one adult male and two adult females, was analyzed quantitatively. Blood samples of the males were taken to determine cortisol, epinephrine, and norepinephrine concentrations. In addition, the exploratory behavior of 60-day-old male WGP-1, WGP-30, and DGP was investigated in an exploration apparatus. The domesticated animals displayed significantly less aggression, but significantly more sociopositive and male courtship behavior than their wild ancestors. In addition, DGP were much less attentive to their physical environment. Surprisingly, no behavioral difference was found between WGP-1 and WGP-30. Basal cortisol concentrations did not differ between wild and domestic guinea pigs. Catecholamine concentrations, however, as well as the challenge values of cortisol, were distinctly reduced in the DGP. WGP-1 and WGP-30 did not differ with respect to their endocrine stress responses. In the exploration apparatus both forms of wild cavies were much more explorative than the domestic animals. These data suggest that the long-term breeding and rearing of wild guinea pigs in captivity do not result in significant changes in behavior and hormonal stress responses. It appears to take much longer periods of time and artificial selection by humans to bring about characters of domestication in wild animals.

Aggression↗
PubMed2000

"Affinity maturation" of ligands for HCV-specific serum antibodies.

We have previously screened a phage-displayed random peptide library using sera from patients and identified ligands binding to antibodies specifically associated with the hepatitis C virus infection. The ability of these peptides to detect HCV-specific antibodies was improved through an in vitro procedure which mimics the natural process of antibody affinity maturation operating in secondary immune response. Libraries were generated by mutating the sequence of the original peptide through a protocol that efficiently introduced substitution, insertion and deletion mutations on a single or population of clones. Screening these libraries isolated mutants that displayed increased specific reactivity with a broader range of sera from HCV-infected patients. Several variants of the original peptide were identified which discriminate between the various components of the specific polyclonal response. This methodology to select artificial ligands from RPL using sera and to enhance their diagnostic properties by affinity maturation makes the development of a diagnostic assay to detect disease-associated antibodies feasible, without requiring the natural antigen.

Amino Acid Sequence↗