Search results for "sexual dimorphism"
showing 10 items of 154 documents
On the origins of body size dimorphism in primates
1986
Among many explanations concerning the origins of dimorphism in Primates, none has received as little attention as the differences in energy requirements of the two sexes. It is hypothesised that among Primates, a common strategy for overcoming the extra metabolic load of pregnency and lactation experienced by females during the greater part of their adult lifetimes, is for them to reduce their bodyweights relative to those of males. Such a strategy allows the mother plus infant combination to weight approximately as much as the species target weight or slightly less, preserving the balance between the species and the environment.
Mature Modifications and Dimorphism in Ammonoid Cephalopods
1996
The shell of an ammonoid is a kind of autobiography of the animal that once occupied it. Different parts of the shell tell different parts of the life history. The growth lines and the tiny intervals in between, along with the shape of the shell itself, record what was happening at the anterior end of the body. The septa and their sutures relate the tale of the other extremity.
Redescription of the rare European harvestman Dicranopalpus brevipes Marcellino, 1970, based on first records from Sardinia (Arachnida: Opiliones)
2020
New records of the small, enigmatic harvestman Dicranopalpus brevipes are presented, the male is redescribed and the female is described for the first time. The species originates from Sicily, while the novel findings are from Sardinia, where it may have been introduced by man. Paedomorphic modifications such as reduced sexual dimorphism in colouration and pedipalpal morphology, regression of genital structures and shortening of the legs, appear to result from its ground-dwelling habits induced by xeric climatic conditions. Avoiding the dry and hot season, D. brevipes matures in autumn and winter and has completed its lifecycle in April. Additional information on phenology, ecology, distrib…
Behavioral roles of the sexually dimorphic structures in the male harvestman, Phalangium opilio (Opiliones, Phalangiidae)
2006
Abstract: In various animal species, male sexual dimorphic characters may be used during intrasexual contests as ornaments to attract females, or to hold them before, during, or after copulation. In the well-known harvestman, Phalangium opilio L., 1758, the behavioral functions of these male sexually dimorphic structures have never been studied in detail. Therefore, in addition to a morphometric study, 21 male contests and 43 sexual interactions were analyzed. Our observations revealed that during contests, the male cheliceral horns form a surface by which the contestants use to push each other face-to-face while rapidly tapping their long pedipalps against the pedipalps of the opponent, oc…
Skull osteology ofParvilacerta parva, a small-sized lacertid lizard from Asia Minor
2002
The skull of the poorly known Asia Minor lacertid lizard Parvilacerta parva is described. In comparison to other palaearctic lacertids, Parvilacerta parva displays several peculiar traits such as a large braincase, a short parietal table, closed post-temporal openings, reduced ossification, or a large lacrimal. Many features are related to the small size of Parvilacerta parva and are of apparently heterochronic nature, as they can also be found in certain ontogenetic stages of other lacertid species. Small size and heterochrony even seem to be factors involved in the less-developed sexual dimorphism of Parvilacerta parva. The described morphology is interpreted to be related to a life histo…
Lifelong exposure to low dose xeno-hormones in rats : multi-generational effects of xeno-hormone mixtures on taste preferences, maternal behavior, an…
2012
During the last decade, the issue of health-related endocrine disruptors (ED) has been extended to the toxicity of mixtures. The objective of this study was to define the effects of lifelong exposure to ED mixtures, at low doses defined as "non-harmful" by the authorities. In this aim, the effects of mixtures combining genistein, vinclozolin and bisphenol A, have been investigated in the rat by using an integrative and multi-generational experimental approach which takes into account maternal behavior, feeding behavior and development. Our results show that these mixtures could: a) reduce maternal behavior, b) change taste preferences (sweet, salty), c) affect the development from the in ut…
Sex-specific responses to cold in a very cold-tolerant, northern Drosophila species
2020
AbstractOrganisms can plastically alter resource allocation in response to changing environmental factors. For example, in harsh conditions organisms are expected to shift investment from reproduction towards survival, however, the factors and mechanisms that govern the magnitude of such shifts are relatively poorly studied. Here we compared the impact of cold on males and females of the highly cold-tolerant species Drosophila montana at the phenotypic and transcriptomic levels. Although both sexes showed similar changes in cold tolerance and gene expression in response to cold treatment, indicating that the majority of changes are concordant between the sexes, we identified a clear reducti…
Exposition continue aux xéno-hormones à faibles doses chez le rat : effets multi-générationnels de mélanges sur les préférences gustatives, le compor…
2012
During the last decade, the issue of health-related endocrine disruptors (ED) has been extended to the toxicity of mixtures. The objective of this study was to define the effects of lifelong exposure to ED mixtures, at low doses defined as "non-harmful" by the authorities. In this aim, the effects of mixtures combining genistein, vinclozolin and bisphenol A, have been investigated in the rat by using an integrative and multi-generational experimental approach which takes into account maternal behavior, feeding behavior and development. Our results show that these mixtures could: a) reduce maternal behavior, b) change taste preferences (sweet, salty), c) affect the development from the in ut…
A Revised Sex Assessment of the Epigravettian Human Remain ST1 from San Teodoro Cave (Messina, Sicily)
2013
Bias in skeletal sexing is well known and depends upon the completeness of the skeletal remains. The problem is very hard concerning prehistorical remains. We applied ‘Visual methods’ and ‘Probabilistic Sex Diagnosis’ (DSP) on the coxal bones on the Epigravettian skeleton (ST1) from San Teodoro (Messina, Sicily). On the basis of cranial characters and the overall robustness of the postcranial skeleton, it was suggested, since the time of the discovery, a male sex for ST1. This determination was later modified on the basis of the pelvic girdle morphology, and the skeleton was attributed the female sex for many years by large consensus. Our results indicate without ambiguity that ST1 is a mal…
Can female preference explain sexual dichromatism in the pied flycatcher, Ficedula hypoleuca?
1990
How important female choice is for the evolution of male secondary sexual characteristics is controversial. Two field and one laboratory experiment, using the pied flycatcher, were performed to test the female choice aspect of sexual selection. In addition, non-manipulative data from 5 years are presented. The observational data suggest a slight preference for dark males by females but in field experiments in which males had territories at random sites (i.e. they did not choose a territory) or the colour of concurrently arriving males was altered, there was no preference for darker ones. Similarly, oestradiol-treated females did not prefer black or brown males in the laboratory. Thus, there…