The Control of Color in Mammals

SYNOPSIS. Recent advances in the biology of mammalian pigmentationare reviewed.Particular attention is given to emerging informationon the integration of pigmentary events occurring at differentlevels of biological organization within mammalian skin andhair. The structural and functional significance of keratinocytesand melanocytes as components of mammalian epidermal melaninunits is viewed from this perspective. New evidence on the natureof genetic, developmental, endocrine, and radiation influenceson performance of melanocytes and the establishment of pigmentarypatterns is summarized.     

鸟类羽色多态现象:概念及其进化制假说

多态现象对了解物种的遗传、变异和进化有着重要意义,鸟类羽色多态现象的进化机制,是多态现象研究中非常重要的内容.鸟类羽色多态现象的进化机制假说主要有分化选择假说、异类选择假说和非随机性交配假说等.本文对鸟类羽色多态现象的概念和以上进化机制假说进行了综述,并针对鸟类羽色多态现象进化机制研究中存在争议的问题及研究的不足提出了自己的看法.     

鸟类羽色多态现象：概念及其进化机制假说

多态现象对了解物种的遗传、变异和进化有着重要意义,鸟类羽色多态现象的进化机制,是多态现象研究中非常重要的内容。鸟类羽色多态现象的进化机制假说主要有：分化选择假说、异类选择假说和非随机性交配假说等。本文对鸟类羽色多态现象的概念和以上进化机制假说进行了综述,并针对鸟类羽色多态现象进化机制研究中存在争议的问题及研究的不足提出了自己的看法。     

Coordinated Control of Respiratory Pattern During Locomotion in Birds

SYNOPSIS. Cineradiographic studies of magpies and pigeons inflight, coupled with measurements of air sac pressures and tracnealairflows, indicate a significant compressive effect of downstrokeand expansive effect of upstroke. These mechanical impacts ofthe wingbeat cycle upon the respiratory system likely contributeto a phasic coordination of the two cycles that, in these species,ensures that upstroke corresponds to the transition into inspirationand downstroke corresponds to the transition into expiration,regardless of the ratio of wingbeats to breaths. Similar phasicpatterns have been reported for other birds. Respiratory muscleactivity patterns indicate that the upstroke may indeed assistinspiratory airflow and that the downstroke may assist expiratoryairflow. Stimulation of ventilation with 5% CO₂ during flightdid not alter the phasic coordination patterns between respiratoryand wingbeat cycles in either pigeons or magpies. These data support the concepts that 1) interactions of locomotorand respiratory central controllers likely play an importantrole in regulating respiratory pattern during locomotion inbirds and 2) peripheral neural feedback of information aboutthe mechanical impact of the wingbeat cycle upon the functioningof the respiratory pump is likely to make a strong contributionto a respiratory pattern that is coordinated with the locomotorpattern in an energetically appropriate phasic relationship.The failure to alter that pattern with chemical stimulationof breathing suggests that the neural interaction between locomotorand respiratory networks is quite robust     

Control of the Cranio-Cervical System During Feeding in Birds

The avian neck is a complex, kinematically redundant system,which plays a role during inter alia food prehension and manipulation.Kinematical analysis shows that chickens (Gallus domesticus)move their vertebrae according to a geometric principle thatmaximizes angular rotation efficiency. The movement patternshows simultaneous rotations in some joints, while not in theothers. Anseriformes show a pattern of successive, rather thansimultaneous rotations in the rostral part of the neck. A kinematicalmodel indicates that the geometric principle produces an anseriform-likepattern only if a constraint on the movement of the caudal vertebraeis introduced. The strength of this constraint, required fora realistic simulation, is related to the amount of stretchin the long dorsal neck muscles (M. biventer and M. longus collidorsalis), which have a different configuration in Anseriformescompared to the chicken. To investigate whether the differencein movement pattern is a result of differences in anatomy only,or also of differences in neuromotor patterns, the EMG-patternsof the neck muscles of the mallard and chicken during drinkingand pecking were studied. Considerable overlap in the activityof antagonists is found in mallards, but not in chickens. Musclesin the rostral part of the neck are activated successively inmallards, but simultaneously in chickens. We conclude that thedifference in movement patterning between chickens and Anseriformes,results from both a difference in the control system of theneck, and a difference in the anatomy. The anseriform patternis found in water as well as on land, which suggests that neckmovement in both environments is controlled by the same neuromotorpatterns. The modifications in motor control system and anatomyof the Anseriformes may have evolved as an adaptation to aquaticfeeding, since the anseriform pattern is energetically morebeneficial in an aquatic environment than on land.     

鸟类的“帮手效应”

众所周知,繁殖鸟能否成功繁殖,并使后代存活取决于许多因素.繁殖鸟往往需要消耗很多的精力来进行繁殖,这对它们来说十分不利.但在部分鸟类中,存在一种常见的生殖合作形式,就是非双亲个体帮助繁殖鸟来喂养它们的后代.帮手鸟帮助它们筑巢,孵卵,觅食,喂食和保护领域等,极大提高了繁殖鸟的适合度,即所谓的"帮手效应".同时帮手鸟也获得了未来的适合度.     

The Discourse of the Birds

Modern humans spend much of their time deploying a very rarefied form of intelligence, manipulating abstract symbols while their muscled body is mostly inert. Other animals, in a constant and largely unmediated relation with their earthly surroundings, think with the whole of their bodies. This kind of distributed sentience, this intelligence in the limbs, is especially keen in the case of birds of flight. Unlike most creatures of the ground, who must traverse an opaque surface of only two-plus dimensions as we make our way through the world, a soaring bird continually adjusts minute muscles in its wings to navigate an omnidimensional plenum of currents and interference patterns that alter from moment to moment. Flight itself may usefully be considered as a kind of thinking—as a sort of gliding within the mind. Moreover, since birds are commonly the most mobile inhabitants of any woodland, able to fly over and scan numerous events occurring on the ground, their varied utterances provide a crucial source of information for many other animals. This paper, written as a philosophic essay, explores avian cognition from a phenomenological standpoint. It then reflects upon the vocalizations of birds—noting the major role that such avian calls, cries, and songs have played in the development of human culture.     

The evolution of partial migration in Birds

Partial migration, i.e.when one fraction of the population is migratory and the other sedentary, appears to be a widespread phenomenon among many animal taxa, ranging from insects to higher vertebrates. Partial migration in birds was first documented for several Holarctic populations many decades ago. The evolution and maintenance of this particular migratory system have only recently been more thoroughly examined, but our knowledge and understanding of the problem is still incomplete. Currently, one of the main concerns is the fitness balancing of the two behavioural alternatives, i.e. whether migrants and residents within a population are equally fit or if one of the categories is inferior and making 'the best of a bad situation'. Closely tied to this question is the proximate regulation of the migratory and sedentary habits. It has been suggested that a social dominance system might be powerful enough to keep this migration system going; alternatively, a pooulation might be divided into two genetically distinct morphs with different preprogrammed Migratory behaviours.