Individual preferences for sound tool design in a parrot.

The rarity of tool manufacture in wild parrots is surprising because they share key life-history traits with advanced tool-using species, including large brains, complex sociality and prolonged parental care. When it does occur, tool manufacture in parrots tends to be innovative, spontaneous and individually variable, but most cases have been in captivity. In the wild, only palm cockatoos (Probosciger aterrimus) have been observed using tools regularly. However, they are unusual because they use tools to enhance their displays rather than for foraging or self-maintenance. Males in northern Australia make two types of tool from sticks and seed pods, which they tap rhythmically against a tree during display. We analysed 256 sound tools retrieved from 70 display trees. Drumsticks (89% of tools) were used more often than seed pod tools; most males manufactured only drumsticks, but some made both types. Individual males differed significantly in the design of their drumsticks including the length, width and mass but we found no evidence that neighbours copied each other. We discuss the highly individualized preferences for sound tool design in context of the behavioural predispositions behind the rarity of tool manufacture in wild parrots.

Sexual selection predicts brain structure in dragon lizards.

Phenotypic traits such as ornaments and armaments are generally shaped by sexual selection, which often favours larger and more elaborate males compared to females. But can sexual selection also influence the brain? Previous studies in vertebrates report contradictory results with no consistent pattern between variation in brain structure and the strength of sexual selection. We hypothesize that sexual selection will act in a consistent way on two vertebrate brain regions that directly regulate sexual behaviour: the medial preoptic nucleus (MPON) and the ventromedial hypothalamic nucleus (VMN). The MPON regulates male reproductive behaviour whereas the VMN regulates female reproductive behaviour and is also involved in male aggression. To test our hypothesis, we used high-resolution magnetic resonance imaging combined with traditional histology of brains in 14 dragon lizard species of the genus Ctenophorus that vary in the strength of precopulatory sexual selection. Males belonging to species that experience greater sexual selection had a larger MPON and a smaller VMN. Conversely, females did not show any patterns of variation in these brain regions. As the volumes of both these regions also correlated with brain volume (BV) in our models, we tested whether they show the same pattern of evolution in response to changes in BV and found that the do. Therefore, we show that the primary brain nuclei underlying reproductive behaviour in vertebrates can evolve in a mosaic fashion, differently between males and females, likely in response to sexual selection, and that these same regions are simultaneously evolving in concert in relation to overall brain size.

Geographical variation in allometry in the guppy (Poecilia reticulata).

Variation in static allometry, the power relationship between character size and body size among individuals at similar developmental stages, remains poorly understood. We tested whether predation or other ecological factors could affect static allometry by comparing the allometry between the caudal fin length and the body length in adult male guppies (Poecilia reticulata) among populations from different geographical areas, exposed to different predation pressures. Neither the allometric slopes nor the allometric elevations (intercept at constant slope) changed with predation pressure. However, populations from the Northern Range in Trinidad showed allometry with similar slopes but lower intercepts than populations from the Caroni and the Oropouche drainages. Because most of these populations are exposed to predation by the prawn Macrobrachium crenulatum, we speculated that the specific selection pressures exerted by this predator generated this change in relative caudal fin size, although effects of other environmental factors could not be ruled out. This study further suggests that the allometric elevation is more variable than the allometric slope.

Female guppies agree to differ: phenotypic and genetic variation in mate-choice behavior and the consequences for sexual selection.

Variation among females in mate choice may influence evolution by sexual selection. The genetic basis of this variation is of interest because the elaboration of mating preferences requires additive genetic variation in these traits. Here we measure the repeatability and heritability of two components of female choosiness (responsiveness and discrimination) and of female preference functions for the multiple ornaments borne by male guppies (Poecilia reticulata). We show that there is significant repeatable variation in both components of choosiness and in some preference functions but not in others. There appear to be several male ornaments that females find uniformly attractive and others for which females differ in preference. One consequence is that there is no universally attractive male phenotype. Only responsiveness shows significant additive genetic variation. Variation in responsiveness appears to mask variation in discrimination and some preference functions and may be the most biologically relevant source of phenotypic and genetic variation in mate-choice behavior. To test the potential evolutionary importance of the phenotypic variation in mate choice that we report, we estimated the opportunity for and the intensity of sexual selection under models of mate choice that excluded and that incorporated individual female variation. We then compared these estimates with estimates based on measured mating success. Incorporating individual variation in mate choice generally did not predict the outcome of sexual selection any better than models that ignored such variation.

Carotenoid scarcity, synthetic pteridine pigments and the evolution of sexual coloration in guppies (Poecilia reticulata).

Carotenoid-based sexual coloration is the classic example of an honest signal of mate quality. Animals cannot synthesize carotenoid pigments and ultimately depend on dietary sources. Thus, in carotenoid-poor environments, carotenoid coloration may be a direct indicator of foraging ability and an indirect indicator of health and vigour. Carotenoid coloration may also be affected, more directly, by parasites in some species. Carotenoids are not, however, the only conspicuous pigments available to animals. Pteridine pigments, with similar spectral properties, are displayed in the exoskeletons and wings of insects, the irides of birds and the skins of fishes, lizards and amphibians. Unlike carotenoids, pteridines are synthesized de novo by animals. We report that the orange spots that male guppies (Poecilia reticulata) display to females contain red pteridine pigments (drosopterins) in addition to carotenoids. We also examined the relationship between drosopterin production by males and carotenoid availability in the field. The results contrasted sharply with the hypothesis that males use drosopterins to compensate for carotenoid scarcity: males used more, not less, drosopterins in streams with higher carotenoid availability. The positive association between drosopterin use and carotenoid availability could reflect the costs of drosopterin synthesis or it could be a consequence of females preferring a particular pigment ratio or hue. Male guppies appear to use drosopterin pigments in a manner that dilutes, but does not eliminate, the indicator value of carotenoid coloration.

Direct and indirect sexual selection and quantitative genetics of male traits in guppies (Poecilia reticulata).

The ornamentation and displays on which sexual attractiveness and thus mating success are based may be complex and comprise several traits. Predicting the outcome of sexual selection on such complex phenotypes requires an understanding of both the direct operation of selection on each trait and the indirect consequences of selection operating directly on genetically correlated traits. Here we report the results of a quantitative genetic analysis of the ornamentation, sexual attractiveness, and mating success of male guppies (Poecilia reticulata). We analyze male ornamentation both from the point of view of single ornamental traits (e.g., the area of each color) and of composite measures of the way the entire pattern is likely to be perceived by females (e.g., the mean and contrast in chroma). We demonstrate that there is substantial additive genetic variation in almost all measures of male ornamentation and that much of this variation may be Y linked. Attractiveness and mating success are positively correlated at the phenotypic and genetic level. Orange area and chroma, the area of a male's tail, and the color contrast of his pattern overall are positively correlated with attractiveness and/or mating success at the phenotypic and genetic levels. Using attractiveness and mating success as measures of fitness, we estimate gradients of linear directional sexual selection operating on each male trait and use equations of multivariate evolutionary change to predict the response of male ornamentation to this sexual selection. From these analyses, we predict that indirect selection may have important effects on the evolution of male guppy color patterns.

Variation in response to artificial selection for light sensitivity in guppies (Poecilia reticulata).

We performed artificial selection on the visual system in guppies (Poecilia reticulata), using the optomotor reaction threshold as the selection criterion. Two lines were selected for increased sensitivity to blue light, two were selected for increased sensitivity to red light, and two were unselected controls. There was significant response to selection in all four selected lines and significant heritability for sensitivity. An examination of the spectral sensitivity function showed that the form of the response differed between the red and blue lines and among the red lines. Such divergence is likely because there are many different mechanisms allowing response to selection for spectral sensitivity. Diverse mechanisms allow a divergent response by different populations to the same selective pressures. Such a mechanism can promote diversity in vision and visual signals, and any multicomponent system where different components can respond to the same selective regime.

Sensory ecology, receiver biases and sexual selection.

During courtship, signals are sent between the sexes, and received signals contain information that forms the basis of decision making. Much is known about signal content, but less is known about signal design-what makes signals work efficiently? A consideration of design not only gives new insights into the evolution of signals (including novelty), but also allows the development of specific and testable predictions about the direction of evolution. Recently there has been increased interest in signal design, but this has resulted in some apparently divergent views in the literature.

Multiple-trait coevolution and environmental gradients in guppies.

Guppies show geographical variation in many different kinds of traits. Traits covary with each other, with predation and with other environmental factors. Phenotypic correlations are often assumed to result from genetic correlations, but may also result from covariation among different sources of natural selection and interactions among the traits' functions. This network of interactions could bias the direction of evolution in characteristic ways, and suggests how intraspecific variation may give rise to interspecific variation.

Some general comments on the evolution and design of animal communication systems.

Animal communication systems have evolved so that individuals can make decisions based upon the behaviour, physiology or morphology of others. Receiving mechanisms probably evolve to increase the efficiency and reliability of information reception whereas signals probably evolve to increase the efficiency of communication and reliability of manipulation of the receiving individual to the benefit of the emitter. The minimum requirement for clear reception suggests that any study of the evolution and design of communication systems must consider the factors that affect the quality of the received and processed signal. Critical information is needed about how the signal is generated and emitted, how it fares during transmission through air, water or substrate, how it is received and processed by the receiver's sensory and cognitive systems, and the factors which affect the fitness consequences of alternative ways of reacting to the information contained in the signal. These should allow predictions about the kinds and forms of signals used by animals signalling under known conditions. Phylogenetic history, and the geological time a clade spends in different signalling environments, will also affect signal evolution, and hence the success of predictions about signal design. We need to use methods of many different biological fields to understand the design and evolution of signals and signalling systems.

[The olfactory region of the bat Scotophilus heathi. Light and electron microscopic studies]. / Die Regio olfactoria der Fledermaus Scotophilus heathi. Licht- und elektronenmikroskopische Studien.

The present investigation reports light and electron microscopical aspects of the main olfactory epithelium (MOE) of the insectivorous bat Scotophilus heathi. Serial frontal sections of the nose and associated structures reveal: 1) that the MOE is located on most of the ethmoturbinals and on the proximal upper portion of the nasal septum; and 2) that the vomeronasal organ is absent in this species. The ultrastructure of the MOE of Scotophilus heathi is similar to that observed in other vertebrates. Moreover, we did not observe significant morphological differences between the MOE of male and female animals. Nevertheless, the supra-nuclear region of the supporting cells of males and females shows a different amount and distribution of "lysosome-like" cell organelles at the two times of the year investigated.

Variation in the appearance of guppy color patterns to guppies and their predators under different visual conditions.

Color patterns of natural populations of guppies (Poecilia reticulata) are a compromise between sexual selection and predation avoidance. Field data on ambient light spectra, water transmission spectra, courtship and attack distances, and cone pigments of guppies and their predators were used to calculate measures of conspicuousness of guppies under various combinations of visual conditions and vision. The results suggest that color patterns are relatively more conspicuous to guppies at the times and places of courtship and relatively less conspicuous at the times and places of maximum predator risk. Some implications to the evolution of vision, visual communication and behavior are discussed.

Correlated Evolution of Female Mating Preferences and Male Color Patterns in the Guppy Poecilia reticulata.

Sexual selection may explain why secondary sexual traits of males are so strongly developed in some species that they seem maladaptive. Female mate choice appears to favor the evolution of conspicuous color patterns in male guppies (Poecilia reticulata) from Trinidad, but color patterns vary strikingly among populations. According to most theory, correlated evolution of female mating preferences and preferred male traits within populations could promote this kind of divergence between populations. But mating preferences could also constrain the evolution of male traits. In some guppy populations, females discriminate among males based on variation in the extent of orange pigment in male color patterns, and populations differ significantly in the degree offemale preferences for orange area. In a comparison ofseven populations, the degree offemale preference based on orange is correlated with the population average orange area. Thus male traits and female preferences appear to be evolving in parallel.

Incidência de mortalidade embrionária em ovelhas submetidas à inseminaçäo artificial / Embryonic mortality in sheep inseminated artificially

A pesquisa incidiu sobre 170 ovelhas adultas da raça Corriedale, criadas em regime extensivo, sob moderadas condiçöes de nutriçäo, com peso médio de 35-40 kg, divididas em cinco grupos, sendo dois com estro induzido hormonalmente. O trabalho foi efetuado durante as estaçöes reprodutivas de 1986 e 1988, e os animais foram inseminados com sêmen fresco e congelado, pelas vias cervical e intra-uterina, esta mediante laparoscopia. A mortalidade embrionária foi medida indiretamente, pela relaçäo entre o número de fetos e o número de corpos lúteos encontrados nas ovelhas abatidas e que näo retornaram ao estro no prazo de 20 dias. A incidência da mortalidade embrionária mostrou-se equivalente quando se empregou o sêmen congelado pelas vias cervical e intra-uterina. O mesmo ocorreu com o uso do sêmen fresco e congelado pela via cervical, quando se utilizou o estro espontâneo. A mortalidade embrionária foi significativamente maior quando se aplicou sêmen congelado, tanto pela via cervical como intra-uterina, no estro induzido. O tratamento hormonal apesar de lograr aumento da taxa ovulatória näo influiu favoravelmente na prolificidade das ovelhas tratadas näo sendo por isso indicado para rebanhos que näo estejam em condiçöes nutritivas favoráveis

Bright ideas about parasites.

The Hamilton-Zuk hypothesis for parasite-mediated sexual selection in animals has generated much controversy. To resolve the arguments it will be necessary to incorporate many more details of the biology, ecology and evolution of hosts and parasites into studies of sexual selection.

Induçäo de estro ovulatório em ovelhas com emprego de estímulos elétricos e/ou hormonais - Nota prévia / Estrus and ovulatory response of ewes treated by eletric and/or hormonal stimulus

A induçäo do estro ovulatório em ovelhas, durante o anestro estacional, é obtida com gestágenos em associaçäo ao eCG. Na estaçäo reprodutiva, cinco ovelhas adultas da raça Corriedale receberam esponjas vaginais impregnadas com 50mg de medroxiprogesterona por 14 dias e, no momento de sua retirada, três sessöes de eletrochoque intervaladas de 12h. O estro induzido e o subsequente foram controlados por machos vasectomizados e o controle ovárico feito por laparoscopia aos 6 e 35 dias após a retirada da esponja. Na estaçäo anestral, 40 ovelhas adultas da raça Corriedale, subdivididas em grupos similares, foram submetidas a quatro tratamentos: EC, constituído de oito sessöes de eletrochoque (10 v, 3 vezes, durante 5", com 5" de descanso, no espaço de 2 dias); MAP + EC, tratamento com gestágeno por 14 dias e posteriormente eletrochoque na forma do primeiro grupo; MAP + GnRH, tratamento com gestágeno pelo mesmo período, e posteriormente 2 injeçöes endovenosas de GnRH; MAP + eCG, gestágeno 14 dias e uma injeçäo de 400 ui de eCG, via intramuscular. A partir do dia da retirada da esponja vaginal e por um período de 26 dias as ovelhas foram expostas a carneiros vasectomizados. Todos os grupos foram inseminados 48 a 60 horas após a retirada da esponja. No grupo MAP + eCG foi procedida laparoscopia adicional para colher informaçöes sobre mortalidade embrionária e/ou indicaçäo de prenhez. Quanto à manifestaçäo de estro, este foi verificado apenas nos tratamentos MAP + GnRH e MAP + eCG, respectivamente em 10 e 60% das fêmeas. No que diz respeito às condiçöes ovarianas, a ovulaçäo foi observada apenas nos tratamentos MAP + eCG (100%) e EC (20%). Em todos os grupos, as condiçöes vaginais às 60h após o início dos tratamentos, revelaram atividade estrogênica pela presença de hiperemia com muco hialino e/ou muco turvo abundante. Quanto à ovulaçäo, esta foi verificada numa freqüência de 20% no grupo EC e de 180% no grupo do tratamento convencional (MAP + eCG). No grupo MAP + eCG, na segunda laparoscopia, observou-se a persistência de corpos lúteos em 6 das 10 ovelhas, em uma a presença de "corpus albicans" sugerindo mortalidade embrionária e as três remanescentes provavelmente retornaram ao anestro, isto é, pela presença de ovários lisos. Os resultados säo indicativos de que o eletrochoque durante o anestro induziu desenvolvimento folicular, atividade estrogênica, ovulaçäo e até mesmo prenhez. Sempre que o gestágeno foi empregado obteve-se atividade estrogênica em grau var

Frequency-dependent predation, crypsis and aposematic coloration.

Frequency-dependent predation may maintain or prevent colour pattern polymorphisms in prey, and can be caused by a variety of biological phenomena, including perceptual processes (search images), optimal foraging and learning. Most species are preyed upon by more than one predator species, which are likely to differ in foraging styles, perceptual and learning abilities. Depending upon the interaction between predator vision, background and colour pattern parameters, certain morphs may be actively maintained in some conditions and not in others, even with the same predators. More than one kind of predator will also affect stability, and only slight changes in conditions can cause a transition between polymorphism and monomorphism. Frequency-dependent selection is not a panacea for the explanation of variation in animal colour patterns, although it may be important in some systems.

Visual pigment polymorphism in the guppy Poecilia reticulata.

Visual pigment polymorphism similar to that found in primates is described in the photoreceptors of wild-caught guppies (Poecilia reticulata). Microspectrophotometric examination of retinal cells revealed rod visual pigments with a lambda max close to 503 nm. Classes of cones with lambda max around 410 and 465 nm were found, together with a population of pigments in the 529-579 nm range. It is in these long-wavelength cones that polymorphism occurs. Male guppies are highly polymorphic for body colour and it is possible that the cone polymorphism is related to the appreciation of the different yellow, orange and red carotenoid colour spots that are used in sexual display.