What are the genetics behind sexual dimorphism in dog body size?4 answersSexual dimorphism in dog body size is influenced by genetic factors ^[Frynta et al.]. The tendency for male-larger sexual size dimorphism (SSD) follows Rensch's rule, where larger breeds exhibit greater SSD ^[Frynta et al.]. Among dog breeds, SSD becomes smaller with decreasing body size, and the smallest breeds are nearly monomorphic ^[Frynta et al.]. The evolution of SSD in dogs is shaped by artificial selection, which has led to the variability of body size and corresponding changes in SSD among breeds ^[Frynta et al.]. The genetic mechanisms underlying sexual dimorphism in dog body size are not explicitly mentioned in the abstracts provided. However, it can be inferred that the genetic basis of SSD in dogs involves the interplay of multiple genes and their expression patterns, which are influenced by artificial selection and potentially other factors such as mating systems and social organization ^[Sheard]. Further research is needed to fully understand the genetics behind sexual dimorphism in dog body size.
Can distribution to nerve and blood supply affect avian testes?5 answersThe distribution of nerve and blood supply can affect avian testes. In Pekin ducks, the testicular arteries run to the center of the testis and terminate as branching arteries, allowing sufficient contact between blood and seminiferous tubules. Simple testicular cysts in ostriches have a richer innervation compared to the normal portion of the testis, similar to the innervation observed in cryptorchid testes of mammals. Species-specific differences in the adrenergic innervation of testicular blood vessels have been found in rabbits, guinea pigs, dogs, and cats. The distribution and density of cerebral perivascular acetylcholinesterase (AChE) nerves differ among avian species, indicating species-specific cholinergic controlling mechanisms for cerebral circulation in birds. In Macacus monkeys, nerve elements are present in the ooplasm of primary follicle oocytes, suggesting a role for the nervous system in the maturation and ovulation of these oocytes.
Are there seasonal changes in sperm parameters?5 answersSeasonal changes in sperm parameters have been observed in several studies. In a study conducted in Beijing, China, it was found that sperm concentration and progressive motility were significantly higher in the spring compared to other seasons. Another study in the same region also reported similar findings, with sperm concentration and total sperm count being lower in the summer compared to other seasons. In Indian men, it was observed that the progressive motility of sperm decreased from pre-monsoon to autumn, indicating the effect of rising temperature on sperm motility. Additionally, in a study on horses, it was found that the proportion of morphologically normal sperm and various computer-assisted semen analysis (CASA) parameters were higher during the breeding season compared to the non-breeding season. These findings suggest that there are indeed seasonal variations in sperm parameters, with factors such as temperature playing a role in influencing semen quality.
How much is the average density in the body of a bird?5 answersThe average density in the body of a bird varies among species, but it generally ranges from 0.602-1.050 g/cm3.The density of a bird's body is influenced by factors such as wingspan, circumference, and body length. There are significant negative correlations between dry density and wingspan, dry circumference, or body length.Feathers make up a varying percentage of a bird's body mass, with some species having 9-10% of their body mass in feathers and others having 2-4%.The relationship between body size and density in birds is not well understood, and it differs from other zoological groups.Further research is needed to explore the factors that influence bird density and to better understand the relationship between body size and density in birds.
What are the anthropometric parameters that are most important for distinguishing between individuals?5 answersAnthropometric parameters that are important for distinguishing between individuals include waist circumference to height ratio (WHtR) and waist to hip circumference ratio (WHR). These parameters have been found to have the greatest discriminative ability in predicting the development of type 2 diabetes in overweight or obese individuals with early carbohydrate metabolism disorders. Additionally, the soft tissue profile of an individual, including skeletal, dental, and facial components, plays a role in facial attractiveness and orthodontic treatment goals. Furthermore, different ideal weight tables have been found to classify individuals differently in terms of malnutrition and obesity, indicating the importance of considering these tables when assessing anthropometric parameters. Lastly, body mass index (BMI) and waist-hip ratio (WHR) have been recommended for evaluating health risks, but more precise indices, such as a health index (HI), may be needed for diagnosing common diseases.
How can morphological characteristics be used to identify species?5 answersMorphological characteristics can be used to identify species by examining their macroscopic and microscopic features. Macroscopic features include colony diameter, color, exudates, and texture, while microscopic features include conidial heads, stipes, vesicles shape and seriation, metula covering, conidia size, shape, and roughness. By studying these characteristics, researchers can compare the morphological features of the species they are trying to identify with those of standard species. Additionally, statistical classification can be used to determine the taxon of subjects based on their traits, such as morphology. This approach involves using a statistical model to determine the taxon of subjects based on their characteristics or traits, and determining combinations of traits that signify each taxon. Bayesian approaches and decision rules can be used for classification, allowing for uncertainty in classification and model selection. Micromorphological characteristics, such as trichome types, can also be used to differentiate species and subspecies.