Dimorphism In Number Research Articles

Antennal sensilla of cleptoparasitic and non-parasitic bees in two subfamilies of Apidae

In bees, most of the comparative studies linking the sensory system and behavior were performed in social species. Here, we describe the morphology of antennal sensilla in solitary and cleptoparasitic bees of Apinae and Nomadinae. The external and internal structure of sensilla and setae as well as their distribution in flagella were studied in detail in two different host-cleptoparasitic associations. In addition, taking into account the presence of pores, the distribution of sensilla was compared in females and males of 39 species of these subfamilies. It was found that males of non-parasitic bees showed a higher number of multiporous sensilla. Females had more uniporous and nonporous sensilla than males. Cleptoparasitic bees showed a low diversity in types of sensilla and no sexual dimorphism in number. The pattern of sensilla in males and their cleptoparasitic females was discussed in the context of their ecological roles.

Evolution of Sexual Dimorphism in the Number of Tail Vertebrae in Salamanders: Comparing Multiple Hypotheses

The evolution of sexual dimorphism is an important topic of evolutionary biology, but few studies have investigated the determinants of sexual dimorphism over broad phylogenetic scales. The number of vertebrae is a discrete character influencing multiple traits of individ- uals, and is particularly suitable to analyze processes determining morphological variation. We evaluated the support of multiple hypotheses concerning evolutionary processes that may cause sexual dimorphism in the number of caudal vertebrae in Urodela (tailed amphibians). We obtained counts of caudal vertebrae from (2,000 individ- uals representing 27 species of salamanders and newts from Europe and the Near East, and integrated these data with a molecular phylogeny and multiple information on species natural history. Per each species, we estimated sexual dimorphism in caudal vertebrae number. We then used phylogenetic least squares to relate this sexual dimorphism to natural history features (courtship complexity, body size dimorphism, sexual ornamentation, aquatic phenology) representing alternative hypotheses on processes that may explain sexual dimorphism. In 18 % of species, males had significantly more caudal vertebrae than females, while in no species did females have significantly more caudal vertebrae. Dimorphism was highest in species where males have more complex courtship behaviours, while the sup- port of other candidate mechanisms was weak. In many species, males use the tail during courtship displays, and sexual selection probably favours tails with more vertebrae. Dimorphism for the number of tail vertebrae was unrelated to other forms of dimorphism, such as sexual ornamenta- tion or body size differences. Multiple sexually dimorphic features may evolve independently because of the interplay between sexual selection, fecundity and natural selection.

Sexual dimorphism in number and proportion of neurons in the human median raphe nucleus

The number and proportion of neurons in the median raphe nuclei stained by the Golgy–Cox and Nissl methods was compared in males and females infants. When subjects are matched by age and cause of death the number and proportion of fusiform, ovoid and multipolar cells differs significantly between sexes at different ages.

Sexual Dimorphism in Numbers of Vasotocin-Immunoreactive Neurons in Brain Areas Associated with Reproductive Behaviors in the Roughskin Newt

Vasotocin (VT) and vasopressin control many endocrine and neuroendocrine functions, including the regulation of reproductive behaviors. In the roughskin newt (Taricha granulosa), VT administration can enhance courtship behaviors in males and egg-laying behaviors in females. This study used immunohistochemistry to investigate whether there are sex differences in VT in specific brain areas, and whether these differences persist in nonbreeding animals. Numbers of VT immunoreactive (ir) cell bodies were counted in males and females collected in February, April, June, and August. Radioimmunoassay of plasma samples confirmed that testosterone and 5α-dihydrotestosterone concentrations were higher in males than females, and that 17β-estradiol concentrations were higher in females than males. In 11 brain areas, no sexual or seasonal differences in the number of VTir cells were found. But in 3 brain regions—the bed nucleus of the stria terminalis (BNST), the nucleus amygdalae dorsolateralis (AMYG), and the anterior preoptic area (aPOA)—there were significantly greater numbers of VTir cells in males than in females, and these differences did not change seasonally. In the aPOA, an area important to male sex behaviors, the sexual dimorphism in VTir was particularly pronounced. In four brain regions, there were significantly greater numbers of VTir cells in females than males, but only in specific seasons. In April-collected (breeding) animals, more VTir cells were found in females than in males in the populations of VT cells within the pars dorsalis hypothalami and ventromedial hypothalamus, brain regions frequently associated with stress responses and female mating behaviors. In August-collected (nonbreeding) animals, more VTir cells were found in females than in males, in the region of the bed nucleus of the decussation of the fasciculus lateralis telencephali and in the nucleus visceralis superior, nucleus isthmi region. Significantly greater numbers of VTir cells were observed in the magnocellular preoptic area of males and females collected in February. These results indicate that the functional interactions between gonadal steroid hormones and VT are complex and appear to involve site-, sex-, and season-specific regulatory mechanisms. Furthermore, it seems likely that populations of VT neurons in the BNST, AMYG, and aPOA are involved in regulating male-specific behaviors, and that the VT neurons in the pars dorsalis hypothalami/ventromedial hypothalamus may be involved in female-specific behaviors.

Morphology of Sensory Structures on the Antennae, Maxillary and Labial Palpi, Tarsi, and Ovipositor of Adult Callosobruchus maculatus and C. subinnotatus (Coleoptera: Bruchidae)

The sensilla on the antennae, maxillary and labial palpi, tarsi and ovipositor of adult Callosobruchus maculatus (F.) and C. subinnotatus (Pic) were examined using light and scanning electron microscopy. Six types of antennal sensilla occur in both species. Type 1 are long and have longitudinal ridges and a conspicuous basal socket. These sensilla occur in rings at the distal margin of each antennal segment; the terminal segment bears 2 such rings. Type 2 sensilla are found on all segments and have a well developed basal socket and less conspicuous cuticular ridges. Type 3 sensilla are numerous and found only on flagellar segments. Type 4 sensilla are medium in length and stout. Types 5 and 6 sensilla are short, few, and are found along with type 4 sensilla in groups distally on the distal antennal segments. Types 1 and 2 are sensilla chaetica, type 3 are trichodea, and types 4, 5, and 6 are sensilla basiconica. Sexual dimorphism in numbers of antennal sensilla is observed. Maxillary and labial palps in both species have 3 types of sensilla. Two subtypes in type 3, fluted (3a) and blunt (3b), sensilla are observed in females of both species. Tarsi and ovipositor of both species have 3 types of sensilla each.

Intrapopulational and Interspecific Variation in Digital Limb Bones and Presacral Vertebrae of the Genus Hemiergis (Lacertilia, Scincidae)

The configuration of the phalanges and the number of presacral vertebrae vary within and among seven populations representing the five species of Hemiergis. Phalangeal variation within popu- lations is rare, being restricted to three of the seven populations sampled. Phalangeal variation among populations suggests a pattern of generally simultaneous reduction of phalanges in the manus and pes. This pattern is in contrast to that observed in Lerista, another genus of fossorial Australian skinks, in which the phalanges of the manus are reduced to a progressively greater degree than are the phalanges of the pes as limbs are reduced. All populations show sexual dimorphism in numbers of presacral vertebrae, females having more presacrals than males. The most parsimonious transformation series among modal

Sexual dimorphism in the numbers of neurons in the pelvic ganglia of adult rats

The major pelvic ganglion in the adult rat differs in neuron number in the two sexes. The female pelvic ganglion has 5892 ± 797 (mean ±S.D.) neurons while the male contains 14,654 ± 936. This sexual dimorphism in neuronal numbers in the autonomic nervous system is of interest because it suggests that endogenous hormone levels during development may have an influence on numbers of neurons in the adult pelvic ganglion.

Sexual Dimorphism in Number of Rostral Teeth of the Sawfish, Pristis perotteti Müller and Henle, 1841

Abstract Rostral tooth counts were made of 211 sawfish (Pristis perotteti) from the Lake Nicaragua-Rio San Juan System. The number of teeth is established early in development and it changes only on accidental loss of teeth, which are not replaced. The average number on the left side is equal to that on the right, but in individuals, either side may have as many as three more teeth than the other. Female tooth counts average 15.94 per side and range from 14 to 18, while males average 18.00 with a range of 16 to 20. Within litters, this dimorphism is also evident, but somewhat less overlap occurs between sexes. On the basis of only three males and three females, P. pectinatus does not appear to exhibit the same dimorphism.