Postweaning environmental and social factors influencing the onset and expression of agonistic behavior in Norway rats

Two studies were conducted to determine the importance of the postweaning environment and social milieu in regulating the expression of intraspecific aggression in Norway rats. In Experiment 1, male rats were housed either individually or in pairs at 21 days of age. In addition, one-half of the singly housed and paired animals were given experiences with intruders during maturation. At 85 days of age, all animals were given a brief intruder test and then removed from their postweaning environment and provided individually with homecages for a two week period until tested for aggression toward intruders. Results of intruder tests given during maturation indicated agonistic exchanges appeared earlier and more frequently in cages housing a single resident than cages with cohabiting males. However, agonistic exchanges between singly reared residents and intruders had detrimental consequences in adulthood especially under long-term combat situations. That is, although individually reared animals, with early fighting experiences, were capable of initiating intraspecific aggression, such individuals were unable to defend their homecage over a long period of time as evidenced by the high number of wounds and tendency to lose body weight during adult fighting.In Experiment 2, male Norway rats were reared in pairs from 21 days of age and identified as dominant or subordinate on the basis of intracolony social interactions shown during maturation. At 80 days of age, animals were paired with individually reared males in an unfamiliar cage for a 20 day period and examined for agonistic behavior toward intruders at 100 days of age. Group-reared subordinate males exhibited defensive behavior during confrontations with individually reared animals and incurred more wounds and lost more body weight than their cohabiting partner. In addition, subordinate males showed significantly fewer offensive postures toward intruders than individually reared cohabitants. In contrast, group-reared dominant animals did not differ from individually reared males in display of agonistic patterns, in number of wounds, and body weight changes during the period of cohabitation. These findings demonstrate that early rearing factors have pronounced effects on agonistic behavior. Animals experiencing defeat during development are more likely to lose agonistic confrontations in unfamiliar territory than either animals dominant in their early social interactions or animals without the experience of winning or losing agonistic encounters. These results have implications for the understanding of agonistic behavior and predicting outcomes of animal contests, and reveal important differences in agonistic experiences among animals reared in groups.     

Behavior of ergatoid males in the ant,Cardiocondyla nuda

Summary Ergatoid males of the ant,Cardiocondyla nuda, attack and frequently kill young males during or shortly after eclosion. Smaller colonies therefore contain typically only one adult male, which may inseminate all alate queens which are reared in the colony over a few weeks. In larger colonies, several males may be present, however, fighting among adult males was not observed. We discuss the significance of male fighting behavior in ants.     

Influence of previous sexual experience and post-emergence rearing conditions on the mating behavior ofChryseida bennetti

Experiments were carried out to study the possible effects of a (first) sexual experience and prior rearing conditions on the subsequent sexual behavior ofChryseida bennetti (Hymenoptera: Eurytomidae), an ectoparasitoid of the bean weevilAcanthoscelides obtectus (Say) (Coleoptera: Bruchidae). A clear reduction in latency before male courtship was observed in experienced males. Multiple matings were performed both by naive and experienced males. A tendency to reduce the post-mating courtship behavior duration was observed in experienced males, although this reduction was not significant. Rearing conditions also seem to influence the mating behavior of this species: the number of copulations (with the same female) was reduced when males were reared in groups. On the contrary, isolated males performed multiple matings with both grouped and isolated females, although they mated 3 times only with isolated ones. Again, a reduction of the duration of the post-mating courtship behavior was observed both in grouped males and grouped or isolated females. It seems likely that males that have been reared in groups benefit from a certain influence of social experience that is reflected on their later sexual behavior.     

Activation and inhibition of isolation induced inter-male fighting behavior in castrate male CD-1 mice treated with steroidal hormones

Intermale fighting behavior between castrate male CD-1 mice living in isolation and castrate male CD-1 mice living in groups of 10 was activated by treating the isolated males with either testosterone or testosterone propionate. Fighting behavior was not activated by treating isolated males with androstenedione or dihydrotesterone even though these androgens were active in maintaining seminal vesicle weight at levels equal to, or greater than, those observed in gonadally intact males. Neither fighting behavior nor seminal vesicle weight was stimulated by treatment with progesterone, estradiol benzoate, or estradiol benzoate plus progesterone. Concurrent administration of progesterone inhibited fighting behavior activated by low, but not moderate to high doses of testosterone propionate. These results suggest that the hormone requirements for activation of fighting behavior in the male CD-1 mouse are more restrictive than those for maintenance of peripheral target tissues and that progesterone acts in the brain to competitively inhibit androgen-activated fighting.     

Further Evidence for Selective Differences between Isoalleles in Drosophila

A number of separate strains of Drosophila pseudoobscura were inbred for 38 generations of brother-sister mating with forced heterozygosity for two alleles of either the octanol dehydrogenase or esterase-5 locus. Crosses were set up within each of these inbred lines such that simple mendelian ratios were expected, and eggs from these crosses were placed on media with additions of simple chemicals likely to interact with alleles of the two loci—octanol and ethanol for the ODH locus and tributyrin and triacetin for the E-5 locus. Similar crosses were set up involving parental flies with normally heterozygous genetic background as a control.—Significant deviations from mendelian expectation were observed in inbred E-5 flies grown on tributyrin, inbred ODH males grown on octanol, and inbred ODH females grown on ethanol. There was also a strong effect of octanol medium on males of one of the inbred E-5 lines, and a weak effect of tributyrin medium on ODH inbred females.—The probability that these results reflect interactions between these loci and the environment is assessed in the light of differences between the present results and those obtained at earlier stages of inbreeding.     

Comparative analysis of the anxiety-related behaviors in four inbred mice

An anxiety-related behavior is an emotional response of an organism, which is quantitatively measured by several behavioral paradigms. We employed two most frequently used behavioral tests, the open field and light-dark exploration, to comparatively analyze the anxiety-like behaviors in four inbred mice. For an accurate recording of movement, motion analysis software was developed that acquires a real-time video input to generate a behavioral path. Effects of the strains on the test results were evaluated by ANOVA with the Newman-Keuls post hoc comparison. Eight different behavioral indices, four from each tests, were grouped into two classes; the results of duration, center crossing, transition, rearing, and ambulation indicate strain differences of FVB/N>C57BL/6J>/=BALB/cA>/=CBA/N (I), while stretched-attend posture, peeping, and defecation show the tendency of FVB/N=C57BL/6J相似文献   

Genetic variation and the performance of a mass‐reared parasitoid,Trichogramma pretiosum (Hymenoptera: Trichogrammatidae), in laboratory trials

During mass rearing, adaptation of biological control agents to the rearing environment is a potential problem. Using the parasitoid wasp Trichogramma pretiosum, the performance of 26 highly inbred lines, five composite ‘populations’ (created from the inbred lines) and one insectary‐reared population was compared using fertility life tables. Of the composite populations, three were created with maximal and identical genetic variation as a mixture of all 26 inbred lines, but these were then reared for a different number of generations (2, 6 or 17) before their performance was measured. The remaining two composite populations were created based on the performance of the individual inbred lines: one was a combination of two inbred lines with a high intrinsic rate of natural increase (rm), ‘high rm’; and the other was a combination of two lines with a ‘low rm’. High and low rm populations were reared for two generations prior to testing. Parameters measured were fertility, longevity and sex ratio. We found no difference between the maximally variable population reared for two generations and the ‘high rm’ population (rm = 0.285 and 0.282, respectively). ‘Low rm’ was the population with the lower performance (rm = 0.255). Genetically variable population reared for two generations for 48 h produced significantly more offspring than the populations reared for 6 and 17 generations. Hybrid population derived from the high‐rm lines did significantly better than that derived from the low‐rm lines. Low‐performance populations become more male based than high performance at 48 h. The potential benefits to improve population's performance using inbred lines for mass rearing are discussed.     

Genetic profile of alloxan-induced diabetes-susceptible mice (ALS) and-resistant mice (ALR)

Two inbred strains from a foundation stock derived from Crj: CD-1 (ICR) mice were established after more than 20 generations of full-sib mating, and by simultaneous selective breeding for developing and not developing diabetes after alloxan administration (45 mg/kg in males, 47 mg/kg in females). To elucidate the genetic background of the two inbred strains, i. e., alloxan-induced diabetes-susceptible (ALS) strain and alloxan-induced diabetes-resistant (ALR) strain, their biochemical genetic markers and immunogenetic markers were examined. 1) For both strains, investigation of biochemical genetic markers at 19 loci and immunogenetic markers at 11 loci revealed no variation in any gene within the same strain, showing to be homogeneous, thus indicating establishment of the inbred strains. 2) The two strains differed from each other at 2 loci of biochemical genetic markers and at 5 loci of immunogenetic markers. 3) The ALS and ALR strains can be regarded as new inbred strains derived from ICR mice. 4) The results show that the marker genes of the two strains are different at 7 loci, but it remains unclear whether or not these genes are involved in the difference between the two strains in susceptibility to alloxan.     

Sexual behavior and male volatile compounds in wild and mass‐reared strains of the Mexican fruit fly Anastrepha ludens (Diptera: Tephritidae) held under different colony management regimes

We compared the calling and mating behavior and volatile release of wild males Anastrepha ludens (Loew) with males from 4 mass‐reared strains: (i) a standard mass‐reared colony (control), (ii) a genetic sexing strain (Tap‐7), (iii) a colony started from males selected on their survival and mating competitiveness abilities (selected), and (iv) a hybrid colony started by crossing wild males with control females. Selected and wild males were more competitive, achieving more matings under field cage conditions. Mass‐reared strains showed higher percentages of pheromone calling males under field conditions except for Tap‐7 males, which showed the highest percentages of pheromone calling males under laboratory cage conditions. For mature males of all strains, field‐cage calling behavior increased during the last hour before sunset, with almost a 2 fold increase exhibited by wild males during the last half hour. The highest peak mating activity of the 4 mass‐reared strains occurred 30 min earlier than for wild males. By means of solid phase microextraction (SPME) plus gas chromatography‐mass spectrometry (GC‐MS), the composition of volatiles released by males was analyzed and quantified. Wild males emitted significantly less amounts of (E,E)‐α‐farnesene but emitted significantly more amounts of (E,E)‐suspensolide as they aged than mass‐reared males. Within the 4 mass‐reared strains, Tap‐7 released significantly more amounts of (E,E)‐α‐farnesene and hybrid more of (E,E)‐suspensolide. Differences in chemical composition could be explained by the intrinsic characteristics of the strains and the colony management regimes. Characterization of calling behavior and age changes of volatile composition between wild and mass‐reared strains could explain the differences in mating competitiveness and may be useful for optimizing the sterile insect technique in A. ludens.     

A role for strain differences in waveforms of ultrasonic vocalizations during male-female interaction

Male mice emit ultrasonic vocalizations (USVs) towards females during male-female interaction. It has been reported that USVs of adult male mice have the capability of attracting females. Although the waveform pattern of USVs is affected by genetic background, differences among strains with respect to USV and the effects of these differences on courtship behavior have not been analyzed fully. We analyzed USV patterns, as well as actual social behavior during USV recording, in 13 inbred mouse strains, which included laboratory and wild-derived strains. Significant effects of strain were observed for the frequency of USV emission, duration, and frequency of the waveform category. Principal component (PC) analysis showed that PC1 was related to frequency and duration, and PC2-4 were related to each waveform. In the comparison of USV patterns and behaviors among strains, wild-derived KJR mice displayed the highest scores for PC2-4, and female mice paired with KJR males did not emit rejection-related click sounds. It is assumed that the waveforms emitted by KJR males have a positive effect in male-female interaction. Therefore, we extracted waveforms in PC2-4 from the USV recordings of KJR mice to produce a sound file, "HIGH2-4". As a negative control, another sound file ("LOW2-4") was created by extracting waveforms in PC2-4 from strains with low scores for these components. In the playback experiments using these sound files, female mice were attracted to the speaker that played HIGH2-4 but not the speaker that played LOW2-4. These results highlight the role of strain differences in the waveforms of male USVs during male-female interaction. The results indicated that female mice use male USVs as information when selecting a suitable mate.     

Behavioral Cost of Reproduction in a Freshwater Crustacean (Eulimnadia texana)

It is commonly noted that investments in reproduction, both physiological and behavioral, can trade off with other life‐history traits, such as growth and survival. In males, behavioral reproductive activities (e.g., copulations) are associated with weight loss, increased predation risk, reduced future reproductive output, and decreased lifespans. It is uncommon to find species in which increased copulations actually increase survival. Herein, we examine one such species, the androdioecious (males + hermaphrodites) crustacean Eulimnadia texana, in which increased copulations have been associated with increased lifespan. We examined two potential causes of this association: (1) males not copulating actually expend significant energy by searching for mates and (2) males are experiencing shorter lifespan primarily because they are more inbred than hermaphrodites. We found that isolated males did indeed expend more energy than hermaphrodites, consistent with previous studies showing that males swim over twice as much as hermaphrodites when isolated. Additionally, although inbreeding was associated with reduced lifespan, outcrossed males still had shorter lifespans relative to outcrossed hermaphrodites. Thus, isolated males consistently show decreased lifespans relative to isolated hermaphrodites, which is not explainable only on the basis of level of inbreeding. We conclude that the costly searching behavior of these males is the likely underlying cause of this observed difference in lifespan between the sexes, as previously suggested.     

THE EVOLUTION OF ALTERNATIVE REPRODUCTIVE TACTICS IN MALE CARDIOCONDYLA ANTS

Alternative reproductive tactics are often associated with discontinuous variation in morphology but may evolve independent from each other. Based on life‐history data and a phylogeny we examine how male morphology and reproductive behavior are linked in the evolution of the ant genus Cardiocondyla. Wingless Cardiocondyla males engage in lethal fighting for access to female sexuals, whereas winged males disperse and mate away from the nest. This basic pattern shows considerable variation across species. A phylogeny based on ～3 kbp sequence data shows that male diphenism and lethal fighting are ancestral traits tightly linked in evolution. Winged males were lost convergently in several species groups, apparently in response to the low probability of encountering female sexuals in nests without a resident fighter male. An early dichotomy separates two clades with alternative male morphologies and fighting behavior, but phenotype and fighting strategy are not correlated with the presence of winged males.     

Female expression of the H-2-linked sex-limited protein (Slp) due to non-H-2 genes

Female mice of 15 inbred strains in which males express the H-2-linked sex-limited protein (Slp) were tested for the production of this protein. Four inbred strains (FM, LG/J, NZB, PL/J) were found in which females produce Slp in the absence of hormonal manipulation. Crosses have been made between strains FM, NZB, or PL/J and several Slp-negative strains. Slp-typing of the F₁, F₂, and backcross progeny, as well as of a number of recombinant inbred strains, indicates that production of Slp by normal females of these strains depends upon the concurrent presence of an Slp-positive,H-t2-linked allele and of permissive alleles of one or two non-H-2 autosomal genes. Complementation studies with two of the strains (FM and PL) indicate that an identical genetic mechanism mediates expression of Slp in females of these two strains. FM-derived animals carrying the testicular feminization mutation (tfm) also express Slp, as do castrated NZB mice, indicating that Slp expression in these instances is not dependent upon testosterone as it is in other inbred strains. It is concluded from these results that genes distinct from the putative structural gene for Slp influence the sex-limitation of its expression.     

A non-social and isolate rearing condition induces an irreversible shift toward continued fights in the male fighting fish (Betta splendens)

Effects of rearing conditions were examined in the development of agonistic behaviors in the male fighting fish. In group-I (highly social), fish were communally reared. In group-II (highly social and isolate), fish were individually housed and exposed to the group-I fish through transparent walls until the sexual maturity (from 6 to 12 weeks post-hatch). In group-III (social and isolate), individually housed fish were similarly exposed to other fish within the group. In group-IV (non-social and isolate), individually housed fish were further visually isolated. Agonisitc behaviors were compared among males of the groups-II, -III, and -IV in their fights against the group-I male. The group-IV males showed significantly higher rate of wins than the groups-II and -III males, without differences in the incidence of agonistic behaviors (butt-or-bite, chase, and gill-cover erect) before the termination of the mutual fights. Increased incidence of agonistic behaviors was found after the termination (particularly in the unilateral chase), suggesting that the group-IV males continued to fight even after the opponent male displayed a submission. The aggression was also enhanced in the group-II, when they were thereafter reared in a social isolation after the sexual maturation; a critical period was thus not found. The enhanced aggression was not reversed in the group-IV, when they were thereafter exposed to social stimuli; shift to the continued fights was irreversible. Possible fitness gain of the enhanced aggression was discussed in terms of the adjustability to altered biological resources.     

Nuclear DNA Polymorphisms Among Strains of Microseris bigelovii (Asteraceae: Lactuceae) Amplified from Arbitrary Primers

The autogamous annual Microseris bigelovii occurs in isolated populations along a narrow strip of land along the Pacific Coast from Southern California to Victoria, B. C. — Thirteen inbred strains were derived from 11 representative populations. Nuclear DNA from these strains was amplified using single arbitrary 10-base-pair primers. 194 amplification products were obtained with 22 primers. Of these, 44 were shared by all strains, 32 were present or absent in only one of the strains. The remaining 118 amplification products were shared by 2 to 11 strains. Attempts to construct a cladogram of the 13 inbred genotypes revealed 5 monophyletic groups. Two of these consist of duplicate isolates from two populations each, two comprise two strains each derived from neighboring populations, and one comprises the three populations from Victoria, B. C., which are postulated to be the result of local differentiation after a single founder event. The Victoria populations share the only known chloroplast mutation in M. bigelovii with a strain from the San Mateo County south of San Francisco. Beyond the local groups of strains we found more or less random allele associations rather than cladistic groupings, with overall genetic distances (UPGMA) more or less related to geographic distance. Achene transport, too rare for direct observationmust be effective to allow gene flow among populationsin M. bigelovii.     

Endocrine and energetic mediation of play behavior in free-living Belding's ground squirrels.

Many juvenile mammals play, and rates and patterns of play behavior often differ between young males and females. The sexual dimorphisms typical of mammalian play suggest that it might be influenced by gonadal hormones. Moreover, because play competes with growth, physical development, and acquisition of fat reserves for available energy, play behavior should theoretically be influenced by energetic variables. We examined patterns of social play behavior and endocrine and energetic mediation of social play in free-living juvenile Belding's ground squirrels (Spermophilus beldingi). Bouts of social play in young S. beldingi resembled adult copulation and fighting, and young males initiated sexual play but not play fighting at much higher rates than did young females. To elucidate the proximal causes of play, we altered early androgen exposure by treating females with testosterone (T) at birth and used females treated with oil vehicle as controls. We concurrently manipulated energy availability by provisioning with extra food and used unprovisioned squirrels as controls. Hourly rates of play behavior were highest near the time of weaning and declined thereafter among both experimental and control groups of juveniles. Thus, we observed no influence of either T treatment or food provisioning on the temporal patterning of play behavior. Perinatal T treatment had no effect on play fighting, but caused rates of sexual play behavior initiated by young females to increase to near those observed for young males, suggesting that T organizes a masculine tendency to initiate sexual play behavior but not play fighting. Food provisioning increased rates of play among males and females from both T-treated and control litters, suggesting that energy availability limits play behavior.     

Allotypes of murine factor B controlled by a locus within the S region of the H-2 complex

Bf protein was directly precipitated from a mixture of EDTA-plasma from 13 different, inbred strains and rabbit IgG anti-mouse Bf, and was isolated by SDS-PAGE. The gel pieces containing Bf protein were digested by trypsin after labeling with 125I-Na, and then peptides of Bf protein with each mouse strain were compared by two-dimensional peptide mapping. The results for the peptide patterns with the standard B10 congenic strains (all of which Bf phenotypes had been already designated as Bf.1 because of the identical isoelectric point values) revealed two distinct peptide patterns. The peptide pattern of Bf protein appeared to be identical in each of the inbred strains, but only one of the 36 spots in the fingerprint observed either with B10 or B10.BR (designated tentatively as Bf.1 (b.k.) ) was not detected in that from B10.D2 and B10.S (designated tentatively as Bf.1 (d.s.) ). The results of peptide mapping with intra-H-2 recombinant inbred strains show that this structural variant was mapped to the S region, which is direct evidence that allotypes of murine Bf are encoded by a structural gene within the MHC.     

Individual differences in the attack behavior of male mice: a function of attack stimulus and hormonal state

Male CFW mice were tested for fighting behavior directed against olfactory bulbectomized male mice and against lactating female mice. Some males were tested with each stimulus type before and after castration. Some males were tested first following castration and then after testosterone treatment. All gonadally intact males attacked bulbectomized males and 25% attacked lactating females. After castration 81% attacked males on at least one occasion and 62% began to attack lactating females, although individual differences in the pattern of post-castration behavior were large. Individual differences in attack behavior were also large in males whose first tests followed castration. Of these, 60% attacked both stimuli. Following testosterone treatment, attack against males increased while attack against females was inhibited. Hormonal stimulation reduced individual differences in behavior and increased males' discrimination between the two types of stimuli.     

Queen number influences the timing of the sexual production in colonies of Cardiocondyla ants

Wingless males of the ant genus Cardiocondyla engage in fatal fighting for access to female sexual nestmates. Older, heavily sclerotized males are usually capable of eliminating all younger rivals, whose cuticle is still soft. In Cardiocondyla sp. A, this type of local mate competition (LMC) has turned the standard pattern of brood production of social insects upside down, in that mother queens in multi-queen colonies produce extremely long-lived sons very early in the life cycle of the colony. Here, we investigated the emergence pattern of sexuals in two species with LMC, in which males are much less long-lived. Queens of Cardiocondyla obscurior and Cardiocondyla minutior reared their first sons significantly earlier in multi-queen than in single-queen societies. In addition, first female sexuals also emerged earlier in multi-queen colonies, so that early males had mating opportunities. Hence, the timing of sexual production appears to be well predicted by evolutionary theory, in particular by local mate and queen-queen competition.     

Effects of physical and social experiences and octopamine receptor agonist on fighting behavior of male crickets Velarifictorus aspersus (Orthoptera: Gryllidae)

Fighting commonly occurs among animals and is very important for resolving conflicts between conspecific individuals over limited resources. The plasticity of fighting strategies and neurobiological mechanisms underlying fighting behavior of insects are not fully understood. In the present study, we examined whether physical and social experiences affected the aggressiveness of males of the cricket Velarifictorus aspersus Walker, and whether an octopamine (OA) receptor agonist could affected the aggressiveness of males exposed to different experiences. We found that flight and winning a fight significantly enhanced male aggressiveness, while losing a fight significantly suppressed male aggressiveness, consistent with the findings of existing studies on other cricket species. We also found that female presence had a stronger enhancing effect on male aggressiveness than flight or winning a fight. These findings demonstrated that physical and social experiences can affect the fighting behavior of male V. aspersus. Topical application of a 0.15?M solution of an OA receptor agonist (chlordimeform, CDM) significantly increased male aggression level, suggesting that OA may play an important role as a neuromodulator in controlling fighting behavior of males of this species. Despite displaying a significantly higher aggression level (level 5 or 6), CDM-treated losers did not escalate to physical combat, while fights between courting males usually resulted in physical escalation. It is likely that fighting behavior is only partly regulated by OA, and additional regulatory pathways may be involved in achieving physical combat.