The family Nassariidae includes a number of species that are distributed throughout the world. Each species has a characteristic shell shape, tooth shape, and behavior. However, the classification of species in this f...The family Nassariidae includes a number of species that are distributed throughout the world. Each species has a characteristic shell shape, tooth shape, and behavior. However, the classification of species in this family of the Rhachiglossa is controversial. We describe the radulae of 22 species from China in detail using optical and scanning electron microscopy. These species are considered to be representatives of two subfamilies, two genera, and 10 subgenera. Our results suggest that the morphology of the central tooth and the pair of lateral teeth and the presence or absence of a pair of intermediate accessory lateral teeth could be used to distinguish among species. We found no support for the subgeneric differentiation of the species. However, the presence or absence of the intermediate lateral accessory plate was characteristic of species divisions. We noted sexual dimorphism in the shape of the teeth in some species, and considerable variability of the shape of teeth within a single species. Based on our results, the genus Nassarius cannot be split into subgenera using radula morphology.展开更多
Several biometric measures were taken from 48 adult （mean age 2.78 ±1.71 years） Basset Hound dogs （24 males and 24 females） belonging to four different farms. For each animal, the following biometrical measur...Several biometric measures were taken from 48 adult （mean age 2.78 ±1.71 years） Basset Hound dogs （24 males and 24 females） belonging to four different farms. For each animal, the following biometrical measurements were considered： withers height, chest height, chest depth, trunk length, rump length, ischium width of the rump, ear and nose length, chest and cannon circumference. Results showed that sexual dimorphism was not present; however two morphological groups of Basset Hound with some differences were found. The first group consisted of animals with high and broad chest, while the second one was more compact, with more pronounced nose and ears. Considering breed health, it would be interesting to select the subjects of the first group since showing an anatomical less susceptible to some conformational disorders typical of the breed. On the contrary, focusing our interest on the breed hunting attitude, the second group would have some characteristics more suitable for this purpose.展开更多
Why do two sexes of the same species differ in body size holds a long-standing question of evolutionary biology. While many across-species comparisons have focused on ultimate causes behind sexual size dimorphism （SS...Why do two sexes of the same species differ in body size holds a long-standing question of evolutionary biology. While many across-species comparisons have focused on ultimate causes behind sexual size dimorphism （SSD）, only have a few been directed toward elucidating its ontogenetic basis. Urodeles are an amphibian group in which the direction and degree of SSD vary greatly among species. Using demographic data yielded by skeletochronology for 33 urodele species, the current study re- veals a positive across-species correlation between SSD and the sex difference in mean age of adult animals, and the latter in- creases with the corresponding difference in age at maturity; annual growth rate does not differ between the sexes. We conclude that extended longevities in one sex, which is mediated by delayed maturation, would allow it to grow for longer and get larger, with growth rate making a weak contribution to body size. The sex-specific divergence in ontogenetic trajectory might be ex- plained by potentially high growth costs of reproduction to females in association with stronger fecundity selection, and to males that are expected to experience stronger sexual selection [Current Zoology 59 （1）： 142-150, 2013].展开更多
基金Supported by the National Natural Science Foundation of China (No. 41076104)the Knowledge Innovation Program of Chinese Academy of Sciences (No. KSCX2-YW-Z-0916)the Knowledge Innovation Program of Institute of Oceanology, Chinese Academy of Sciences (No. 2007-12)
文摘The family Nassariidae includes a number of species that are distributed throughout the world. Each species has a characteristic shell shape, tooth shape, and behavior. However, the classification of species in this family of the Rhachiglossa is controversial. We describe the radulae of 22 species from China in detail using optical and scanning electron microscopy. These species are considered to be representatives of two subfamilies, two genera, and 10 subgenera. Our results suggest that the morphology of the central tooth and the pair of lateral teeth and the presence or absence of a pair of intermediate accessory lateral teeth could be used to distinguish among species. We found no support for the subgeneric differentiation of the species. However, the presence or absence of the intermediate lateral accessory plate was characteristic of species divisions. We noted sexual dimorphism in the shape of the teeth in some species, and considerable variability of the shape of teeth within a single species. Based on our results, the genus Nassarius cannot be split into subgenera using radula morphology.
文摘Several biometric measures were taken from 48 adult （mean age 2.78 ±1.71 years） Basset Hound dogs （24 males and 24 females） belonging to four different farms. For each animal, the following biometrical measurements were considered： withers height, chest height, chest depth, trunk length, rump length, ischium width of the rump, ear and nose length, chest and cannon circumference. Results showed that sexual dimorphism was not present; however two morphological groups of Basset Hound with some differences were found. The first group consisted of animals with high and broad chest, while the second one was more compact, with more pronounced nose and ears. Considering breed health, it would be interesting to select the subjects of the first group since showing an anatomical less susceptible to some conformational disorders typical of the breed. On the contrary, focusing our interest on the breed hunting attitude, the second group would have some characteristics more suitable for this purpose.
文摘Why do two sexes of the same species differ in body size holds a long-standing question of evolutionary biology. While many across-species comparisons have focused on ultimate causes behind sexual size dimorphism （SSD）, only have a few been directed toward elucidating its ontogenetic basis. Urodeles are an amphibian group in which the direction and degree of SSD vary greatly among species. Using demographic data yielded by skeletochronology for 33 urodele species, the current study re- veals a positive across-species correlation between SSD and the sex difference in mean age of adult animals, and the latter in- creases with the corresponding difference in age at maturity; annual growth rate does not differ between the sexes. We conclude that extended longevities in one sex, which is mediated by delayed maturation, would allow it to grow for longer and get larger, with growth rate making a weak contribution to body size. The sex-specific divergence in ontogenetic trajectory might be ex- plained by potentially high growth costs of reproduction to females in association with stronger fecundity selection, and to males that are expected to experience stronger sexual selection [Current Zoology 59 （1）： 142-150, 2013].
