Kin selection and the evolution of monogamy

A two-locus genetic model is studied in which one locus controls the tendency of individuals to act altruistically toward siblings and the other locus controls the mating habits of females. It is demonstrated that genetic variation at the altruism locus is often sufficient to induce an increase in the frequency of genes that cause females to produce all of their offspring with a single mate. This occurs because of nonrandom associations that develop between genes that cause altruism and those that affect female mating behavior. The results provide a new explanation for the evolution of monogamy, and they suggest a previously unexplored mechanism for the evolution of a variety of other behavioral traits as well.     

A genetic test of the natal homing versus social facilitation models for green turtle migration

Female green turtles exhibit strong nest-site fidelity as adults, but whether the nesting beach is the natal site is not known. Under the natal homing hypothesis, females return to their natal beach to nest, whereas under the social facilitation model, virgin females follow experienced breeders to nesting beaches and after a "favorable" nesting experience, fix on that site for future nestings. Differences shown in mitochondrial DNA genotype frequency among green turtle colonies in the Caribbean Sea and Atlantic Ocean are consistent with natal homing expectations and indicate that social facilitation to nonnatal sites is rare.     

Zinc deficiency in murine milk underlies expression of the lethal milk (lm) mutation

The inability of nursing pups to survive on milk of mice homozygous for the recessive mutation, lethal milk (lm), is correlated with a reduction in zinc levels of both milk and pup carcass. Administration of zinc to pups nursing on lmlm dams reduces the observed mortality and morbidity. It is suggested that lm alters zinc transport from maternal blood to milk and that its study may provide useful information for understanding the rare human disease, acrodermatitis enteropathica.     

BEHAVIOR OF ADULT RATS IS MODIFIED BY THE EXPERIENCES THEIR MOTHERS HAD AS INFANTS

Some rat pups were handled for 20 days in infancy, while others were not. When the rats reached adulthood the females were bred. Some of the offspring were left with their natural mothers, others were fostered to mothers of the same background (handled/nonhandled) as that of their natural mothers, while still others were fostered to mothers with a different background from that of their natural mothers. The offspring were weaned and weighed at 21 days; at 50 days, activity and defecation scores were obtained in the open field. The weights at weaning and the defecation scores at 50 days were significantly influenced by the experience in infancy of the "postnatal" mother, whether she was the natural mother or a foster mother. The natural mother and the foster mother jointly affected the open-field activity of the offspring.     

Premature births in California sea lions: association with high organochlorine pollutant residue levels

Premature pupping in California sea lions has been noted on the breeding islands since 1968. Organochlorine pesticides and polychlorinated biphenyl residues were two to eight times higher in tissues of premature parturient females and pups than in similar tissues of full-term parturient females and pups collected on San Miguel Island in 1970.     

Evidence for mate fidelity in the gray seal

Colonially breeding gray seals are polygynous. Males are larger than females, compete with each other for position among aggregated females, and contribute no parental care. Genetic analysis of pups born on the island of North Rona, Scotland, reveals large numbers of full siblings, although dominant males father disproportionately few of these. This result cannot be explained by mating patterns based solely on male dominance and the spatio-temporal organization of the breeding colony. Instead, many full siblings must result from choices favoring previous parental combinations. Thus, polygyny and partner fidelity appear to operate simultaneously in this breeding colony.     

Evolution and development of sex differences in cooperative behavior in meerkats

In cooperatively breeding birds, where helpers of both sexes assist with the provisioning and upbringing of offspring who are not their own, males tend to contribute more than females to rearing young. This sex difference has been attributed to paternity uncertainty, but could also occur because males contribute more where they are likely to remain and breed in their group of origin. In contrast to most birds, female meerkats (Suricata suricatta) are more likely to breed in their natal group than males. We show that female meerkat helpers contribute more to rearing young than males and that female helpers feed female pups more frequently than males. Our results suggest that sex differences in cooperative behavior are generated by sex differences in philopatry and occur because females derive greater direct benefits than males from raising recruits to their natal group. These findings support the view that direct, mutualistic benefits are important in the evolution of specialized cooperative behavior.     

Localization of heart poisons in the monarch butterfly

The cardiac glycosides that monarch butterflies sequester from milkweed plants during the larval stage differ remarkably in their emetic potency and are concentrated to different degrees in the various parts of the body as well as in the two sexes (Fig. 1). The very high concentrations of these compounds in the wings probably facilitate learned taste rejection in predators and account for the relatively high frequency of Danaid butterflies with beak-marked wings in natural populations. The cardiac glycosides in the abdomen have a much higher emetic potency than those in the rest of the body. Consequently, naive, extremely hungry, or forgetful birds which capture and peck off the wings but eat the abdomen discard the least emetic glycosides and ingest the most emetic, and thus again experience emesis. The nonrandom distribution of cardenolides in the wings, abdomen, and thorax, together with the fact that monarch males not only contain lower concentrations of cardiac glycosides than females but also contain cardenolides that are overall less emetic than those in females, is interpreted as evidence that these poisons are incorporated at a physiological cost. This cost, balanced against the benefits of protection from predation, provides a selective basis for the occurrence of both emetic and nonemetic individuals in natural populations. Since birds can discriminate emetic from nonemetic monarchs on the basis of taste, it is not necessary to invoke theories of kind of group selection to explain the evolution of this kind of unpalatability.     

Retinoblastoma: clues to human oncogenesis

The retinoblastoma gene can be considered a model for a class of recessive human cancer genes that have a "suppressor" or "regulatory" function. The loss or inactivation of both alleles of this gene appears to be a primary mechanism in the development of retinoblastoma. Such a mechanism is in direct contrast to that of putative human oncogenes which are thought to induce tumorigenesis following activation or alteration. The high incidence of second primary tumors among patients who inherit one inactive retinoblastoma allele also suggests that this cancer gene plays a key role in the etiology of several other primary malignancies. Finally, the observation that extra nonrandom copies of specific chromosomal regions occur in some of these tumors provides circumstantial evidence that an "expressor" gene (possibly an oncogene) may be involved in retinoblastoma development.     

Tournaments and slavery in a desert ant

Many species of ants engage in physical fighting when territorial borders are challenged. In contrast, colonies of the honeypot ant species Myrmecocystus mimicus conduct ritualized tournaments, in which hundreds of ants perform highly stereotyped display fights. Opposing colonies summon their worker forces to the tournament area by means of an alarm-recruitment system. When one colony is considerably stronger than the other, the tournament quickly ends, and the weaker colony is raided and its ants "enslaved." This is the first example of intraspecific slavery recorded in ants.     

Haplodiploidy and the evolution of facultative sex ratios in a primitively eusocial bee

In eusocial Hymenoptera, the haplodiploid system of sex determination creates relatedness asymmetries such that workers are more closely related on average to their sisters than to their brothers. For such societies, kin-selection theory and sex-ratio theory predict that workers maximize their inclusive fitness by biasing the investment sex ratio toward females. To test the prediction of sex-ratio biasing, relatedness asymmetries were experimentally manipulated in colonies of the primitively eusocial bee Augochlorella striata (Halictidae: Hymenoptera) by removing or not removing foundress queens. Queenright colonies (relatedness asymmetry present) produced a more female-biased sex ratio than did queenless colonies (relatedness asymmetry absent). Worker reproduction and unmated replacement queens can be discounted as alternative explanations. Workers therefore facultatively adjusted their colony's sex ratio and, in the presence of a relatedness asymmetry, biased the investment sex ratio toward their more closely related sisters and away from their more distantly related brothers.     

Enduring changes in dopamine receptor cells of pups from drug administration to pregnant and nursing rats

A decrease in specific [3H]spiroperidol binding to rat caudate tissue and a parallel decrease in sensitivity to apomorphine in eliciting stereotyped behavior was observed in the offspring of rat mothers treated with either haloperidol or alpha-methyl-p-tyrosine-methyl ester during pregnancy. In contrast, evidence of increased dopamine-receptor sensitivity was observed in the pups if haloperidol was administered to their mothers postpartum during nursing rather than during pregnancy.     

Sex pheromone of the queen butterfly: biology

Males of the queen butterfly Danaus gilippus berenice, deprived of the two extrusible brushlike "hairpencils" at the rear of their abdomen, are capable of courting females but incapable of seducing them. In normal courtship, an aphrodisiac secretion associated with the hairpencils is transferred by way of tiny cuticular "dust" particles to the antennae of the females. Of the two substances identified from the secretion, one (the ketone) acts as the chemical messenger that induces the females to mate. The only known function of the other compound (the diol) is to serve as a glue that sticks the dust to the female. Males were reared under conditions in which they produced subnormal amounts of ketone and showed reduced seductive capacity. Under certain experimental circumstances, the competence of these males was restored by addition of synthetic ketone.     

Early maternal separation increases gastric ulcer risk in rats by producing a latent thermoregulatory disturbance

Rat pups that are separated early from their mothers, at postnatal day 15, become hypothermic when subjected to physical restraint on postnatal day 30. Restraint of separated pups also elicits an unusually high incidence of gastric erosions, as well as insomnia and an increase in quiet wakefulness. If hypothermia during restraint is prevented, neither the erosions nor the behavioral responses occur. Rat pups separated at the customary age (postnatal day 22) do not become hypothermic during restraint, and the restraint of such pups is not associated with either gastric erosion or insomnia.     

Treehoppers transfer parental care to ants: a new benefit of mutualism

Female treehoppers (Publilia reticulata Van Duzee) modify their parental care behavior in the presence of ants. Females with untended young remain with their original brood, but females from ant-tended colonies readily desert their first brood and produce additional clutches. Care by female treehoppers, in the absence of ants, increases the probability that a colony will produce some survivors, but ant attendance greatly increases the number of surviving nymphs.     

Infantile experience with suckling odors determines adult sexual behavior in male rats

Because infant rats learn about odors that elicit suckling, and because certain chemosensory cues that help elicit mating behavior in adults are similar to those that elicit suckling, an experiment was undertaken to assess the influence of suckling-associated odors experienced during infancy on adult sexual behavior. Rat pups lived with and suckled dams whose nipple and vaginal odors were altered with citral, a lemon scent. The rats were weaned and never exposed again, until testing, to citral or females. At about 100 days of age, the males were paired in mating tests with a normal sexually receptive female or with a sexually receptive female that had been treated perivaginally with citral immediately before testing. The males ejaculated readily when paired with citral-treated females but were slow to achieve ejaculation when paired with normal females. These findings implicate an infantile experience as a determinant of adult sexual behavior in a mammal.     

Deficit in attachment behavior in mice lacking the mu-opioid receptor gene

Endogenous opioid binding to micro receptors is hypothesized to mediate natural rewards and has been proposed to be the basis of infant attachment behavior. Here, we report that micro-opioid receptor knockout mouse pups emit fewer ultrasonic vocalizations when removed from their mothers but not when exposed to cold or male mice odors. Moreover these knockout pups do not show a preference toward their mothers' cues and do not show ultrasonic calls potentiation after brief maternal exposure. Results from this study may indicate a molecular mechanism for diseases characterized by deficits in attachment behavior, such as autism or reactive attachment disorder.     

非孕期圈养林麝粪样皮质醇激素变化及其指示作用

于2010年4月底至9月中旬采集了陕西凤县圈养林麝的新鲜粪样,运用酶联免疫法（ELISA）测定了林麝非孕期的粪样皮质醇含量,探查林麝的应激生理状态。结果表明:圈养雌性林麝非孕期应激生理状态可以分为4个阶段（幼仔卧巢哺乳期、幼仔出巢哺乳期、幼仔单独饲养期、雌麝进入发情期）,其中,雌麝于产后的幼仔卧巢哺乳期处于较高的应激生理状态（产后第2~4周）,而雌麝与幼麝分离期处于较低的应激生理状态（产后第13~15周）;与此对应,单独饲养且与育幼无关的雄麝仅于饲料更换阶段（5月份）表现出一定的应激生理水平增高。分析得出,非孕期圈养林麝粪样皮质醇水平变化与重要的时间相联系,是导致应激生理状态变化的主导因素。认为圈养林麝非孕期应以雌麝的管护为主,尤其处于较高水平的第1阶段,是育幼雌麝饲喂和管护的敏感时期。      

Rapid expulsion of Trichinella spiralis in suckling rats

Orally administered Trichinella spiralis muscle larvae were rapidly expelled by rat pups suckling an immune dam. The immunity was delivered in the milk; substantial resistance was conferred on normal rat pups suckled for only 24 hours by a Trichinella-immune foster mother. The pups were protected by oral or systemic administration of specific serum antibodies. When infused into a normal lactating dam, these antibodies accumulated in the serum of her suckling pups.     

Sex differences in the brain: implications for explaining autism

Empathizing is the capacity to predict and to respond to the behavior of agents (usually people) by inferring their mental states and responding to these with an appropriate emotion. Systemizing is the capacity to predict and to respond to the behavior of nonagentive deterministic systems by analyzing input-operation-output relations and inferring the rules that govern such systems. At a population level, females are stronger empathizers and males are stronger systemizers. The "extreme male brain" theory posits that autism represents an extreme of the male pattern (impaired empathizing and enhanced systemizing). Here we suggest that specific aspects of autistic neuroanatomy may also be extremes of typical male neuroanatomy.