Mammals have seven cervical vertebrae, a number that remains remarkably constant. I propose the lack of variation is caused by developmental constraints: to wit, changes in Hox gene expression, which lead are associated with neural problems and an increased susceptibility early childhood cancer stillbirths. In vertebrates, genes involved development skeletal axis nervous system, among other things. humans mice, been shown also be normal abnormal (cancer) proliferation cell lines; several...

The second to fourth digit ratio (2D:4D) is smaller in human males than females and hence this trait sexually dimorphic. thought be established during early prenatal development under the influence of sex hormones. However, general assumption establishment has hardly been studied. In our study, we analyzed 2D:4D 327 deceased fetuses. We measured lengths 169 male 158 female fetuses ranging from 14 42 weeks old. Our results showed a slight, but significant, sexual dimorphism expected...

In this study we investigate the possible role of phenotypic plasticity and genetic assimilation in process adaptation evolutionary change cichlid Pseudocrenilabrus multicolor victoriae . field compared a population stable hypoxic habitat with one well‐oxygenated habitat. laboratory, individuals from same mother raised under or conditions to examine plasticity. Morphological parameters three categories were measured: (a) gill apparatus, (b) surrounding structural elements, (c) outer shape...

Mammals as a rule have seven cervical vertebrae, except for sloths and manatees. Bateson proposed that the change in number of vertebrae is due to homeotic transformations. A recent hypothesis proposes unchanged instead derived pattern abnormal primaxial/abaxial patterning.We test detailed predictions from both hypotheses skeletal patterns manatees hypotheses. We find strong support Bateson's homeosis hypothesis. The observed vertebral rib cannot be explained by changes patterning. Vertebral...

Abstract In most animal taxa, longevity increases with body size across species, as predicted by the oxidative stress theory of aging. contrast, in within‐species comparisons mammals and especially domestic dogs (e.g. Patronek et al., '97 ; Michell, '99 Egenvall 2000 Speakman 2003 ), decreases size. We explore two datasets for find support a negative relationship between if we consider variation breeds. Within breeds, however, is not slightly, but significantly, positive larger datasets. The...

(4) Flies never or rarely oviposited in non-host and marked fruit respectively, both cases emigrated from trees harbouring those soon after examining the fruit. (5) exhibited success-motivated search following discovery of oviposition uninfested, unmarked (6) visited more fruit, often remained longer high v. low densities clusters. (7) sooner last egg they laid on high, low, clusters (Giving Up Time shorter). (8) Rhagoletis pomonella foraging behaviour is discussed relation to current theory.

Why do all mammals, except for sloths and manatees, have exactly seven cervical vertebrae? In other vertebrates regions, the vertebral number varies considerably. We investigated whether natural selection constrains of vertebrae in humans. To this end, we determined incidence ribs homeotic changes radiographs deceased human fetuses infants, analyzed several existing datasets on infants adults. Our data show that transformations change are extremely common humans, but strongly selected...

The mammalian vertebral column is highly variable, reflecting adaptations to a wide range of lifestyles, from burrowing in moles flying bats. However, many taxa, the number trunk vertebrae surprisingly constant. We argue that this constancy results strong selection against initial changes these numbers fast running and agile mammals, whereas such weak slower-running, sturdier mammals. rationale require homeotic transformations into sacral vertebrae, or vice versa, mutations toward generally...

In this study we explore the possible role of phenotypic plasticity in process adaptation and evolutionary change African cichlid Pseudocrenilabrus multicolor victoriae.Parental fish were collected from a hypoxic swamp, lake ecotone, river Uganda.Broods (F1) split grown under hypoxia or normoxia.We measured morphological parameters gill apparatus, structural elements surrounding gills, brain mass, body shape.Most traits showed substantial response to rearing environment.Population effects...

SUMMARY (1) Patch time allocation by the parasitoid Asobara tabida Nees was studied on patches with different host densities. (2) The increased its searching and giving up increasing density. These increases were caused a response of to number encounters unparasitized hosts; amount kairomone in patch may have had an additional incremental effect time. (3) Encounters parasitized hosts no (4) percentage first density then levelled off at densities more than four larvae per patch, thus...

Resource polymorphisms and competition for resources are significant factors in speciation. Many examples come from fishes, cichlids of particular importance because their role as model organisms at the interface ecology, development, genetics evolution. However, analysis trophic resource use fishes can be difficult time-consuming, fossil fish species it is particularly problematic. Here, we present evidence that tooth microwear based on high-resolution (sub-micrometre scale)...

In humans, an increasing body of evidence has linked the frequency cervical ribs to stillbirths, other malformations and early childhood cancers. However, in a putatively healthy fetal population is not sufficiently known assess actual medical risks these prenatal findings. We therefore analyzed presence skeletal anomalies series 199 electively aborted fetuses, which were whole-mount stained with alizarin red specific for tissues. Results show that approximately 40% fetuses had ribs, even...

Homeotic transformations of vertebrae are particularly common in humans and tend to come associated with malformations a wide variety organ systems. In dataset 1,389 deceased human foetuses infants majority had cervical ribs approximately half these individuals also missing twelfth or lumbar ribs. ~10 % all cases there was an additional shift the lumbo-sacral boundary and, hence, homeotic resulted shifts at least three vertebral boundaries. We found strong coupling between abnormality...

Abstract This study compares the pharyngeal biting mechanism of Cichlidae, a family perciform fishes that is characterized by many anatomical specializations, with Centrarchidae, possesses generalized anatomy. Our objective was to trace key structural and functional changes in jaw apparatus have arisen evolution from derived (cichlid) condition. We propose mechanical model Centrarchidae compare this an already existing for Cichlidae. Central our centrarchid coupling between upper lower jaws....

We studied three factors affecting the allocation of patch time and intensity searching by larval parasitoid Asobara tabida Nees.We found that: 1. A. reacts to a water-soluble kairomone, produced its host Drosophila melanogaster Meigen in that a) spent on (yeast which D. larvae had crawled fed) increased S-shaped fashion with increasing kairomone concentration.b) concentration until it levels off at higher concentrations.2. recognized areas previously searched conspecific less intensely such...

In vertebrates, the relative proportion of number trunk and caudal vertebrae is an important determinant body shape. While among amphibians frogs toads show low variation in numbers, salamanders numbers vary widely, giving rise to phenotypes range from short-bodied long-tailed long-bodied short-tailed. We analysed vertebral family Salamandridae a phylogenetic context calculated relationship between changes climate other environmental parameters. A significant association was found...

Body plans are remarkably well conserved, but on (very) rare occasions important novelties evolve. Such involve changes at the genotypic and phenotypic level affecting both developmental adult traits. At all levels, duplications play an role in evolution of novelties. Mutations for duplications, including mutations body parts, as other plan, particular homeotic ones, occur surprisingly frequently. Hence limitation appears to be relatively unimportant conservation plans. However, parts rarely...