Project description:The modern walrus Odobenus rosmarus is characterized by marked sexual dimorphism, related to its polygynous behavior and the aggressive competition between males during the breeding season. Previous studies treated skeletal sexual dimorphism in walruses either qualitatively or with basic quantitative measurements. The present study combines a detailed qualitative comparison of male and female walrus mandibles with quantitative two-dimensional geometric morphometrics analysis (principal component analysis, Procrustes ANOVA and a linear discriminant analysis). In addition to identifying previously recognized sexually dimorphic features (e.g., convexity of the anterior margin of the mandible in adult males), our study finds new morphological differences between males and females, such as a relative dorsal expansion of the anterior part of the mandible and an accentuated concavity between the dorsal margin and the coronoid process in adult males. Both our qualitative comparisons and quantitative analyses demonstrate that sexual dimorphism as expressed in the mandible of extant walruses is statistically significant and that (variation in) mandibular morphology can be used as tool to attribute sex with a good degree of accuracy to isolated mandibles or skeletons lacking the cranium. Sexual dimorphism in walruses is directly related to their sexual behavior, characterized as aggressive in males and linked to a polygynous reproduction system. Indeed, the difference in size of the tusks between males and females but also the use of these during intraspecific fights, can reasonably account for this great mandibular morphological disparity between adult males and females, but also among different ontogenetic stages. Finally, the results obtained in the present study may serve as a starting point for assessing sexual dimorphism more in-depth and studying inter- and intraspecific variation in the mandibles of fossil walruses by identifying quantified size and shape mandibular features.
Project description:Mangatangi parvum gen. n. and sp. and Forsteropsalis pureroa sp. n. are described from the North Island of New Zealand. Pantopsalis listeri (White 1849) and Pantopsalis cheliferoides (Colenso 1882) are redescribed and no longer regarded as nomina dubia; Pantopsalis luna (Forster 1944) is identified as a junior synonym of Pantopsalis listeri. A key to Pantopsalis species is provided.
Project description:Sexual dimorphism in feeding stylets is recorded among some Phlaeothripinae that have maxillary stylets long and close together in females but wider apart in males. These atypical long feeding stylets have been found in two new species of Haplothrips from China, both taken on Artemisia from Plateau zone. Two species are described and illustrated: H.helanshanensissp. nov. from Helanshan Mountain and H.longistylussp. nov. from Tibet. There is no evidence of any association between feeding behaviors and feeding stylet orientation.
Project description:Ektaphelenchus koreanus n. sp. is isolated from Pinus packaging wood from Korea in Ningbo customs. The new species can be characterized by having four incisures in the lateral field, the excretory pore located posterior to nerve ring, female devoid of vulval flap, and having long post-vulval intestinal sac (55-106 μm), tail with a finely rounded terminus. Six caudal papillae in male and spicule short (12.7-13.7 μm), having broad squared to rounded condylus, triangular rounded rostrum, cucullus absent. Morphologically the species is most similar with E. berbericus, E. joyceae, E. oleae, E. ibericus, and E. taiwanensis but it can be differentiated by plenty of morphometrical and morphological characters. In addition, a morphometry table of Ektaphelenchus is also presented.
Project description:Sexual selection is often considered as a critical evolutionary force promoting sexual size dimorphism (SSD) in animals. However, empirical evidence for a positive relationship between sexual selection on males and male-biased SSD received mixed support depending on the studied taxonomic group and on the method used to quantify sexual selection. Here, we present a meta-analytic approach accounting for phylogenetic non-independence to test how standardized metrics of the opportunity and strength of pre-copulatory sexual selection relate to SSD across a broad range of animal taxa comprising up to 95 effect sizes from 59 species. We found that SSD based on length measurements was correlated with the sex difference in the opportunity for sexual selection but showed a weak and statistically non-significant relationship with the sex difference in the Bateman gradient. These findings suggest that pre-copulatory sexual selection plays a limited role for the evolution of SSD in a broad phylogenetic context.
Project description:In the present study, we utilized a label-free proteomics approach to identify and quantify proteins that are the basis of sexual dimorphism in the GI tract of zebrafish. The results of present study in combination with an extensive literature review can provide an in-depth insight into the molecular mechanisms that distinguish sexes in the digestion and absorption of nutritional materials needed for body maintenance and gametogenesis, as well as their abilities for drug metabolism.
Project description:The genus Plistobunus Pocock, 1903 and its type species Plistobunus rapax Pocock, 1903 are redescribed based on the type material deposited in the British Museum of Natural History (BMNH), London. In addition, a new Plistobunus species from Hainan Island is described and illustrated of Plistobunus columnariussp. n. The new species is diagnosed by having a row of 12 setiferous tubercles on anterior margin of carapace, and the femur of pedipalpus ventrally with 13 setiferous tubercles in male.
Project description:A new species, Apteroloma zhejiangensesp. n., is described from Zhejiang Province, China. The habitus and sexual characters of the new species are illustrated. Apteroloma jinfo Růžička, is reported for the first time from China: Hubei and Hunan Provinces, and Apteroloma potanini (Semenov, 1893) from Ningxia and Henan Provinces. Presence of Apteroloma kozlovi Semenov-Tian-Shanskij & Znojko in Semenov-Tian-Shanskij, 1932 in South Korea is confirmed based on re-examined material.
Project description:Meiosis is a highly conserved and essential process in gametogenesis in sexually reproducing organisms. However, there are substantial sex-specific differences within individual species with respect to meiosis-related chromatin reorganization, recombination, and tolerance for meiotic defects. A wide range of murine models have been developed over the past two decades to study the complex regulatory processes governing mammalian meiosis. The present review article thus provides a comprehensive overview of the knockout mice that have been employed to study meiosis, with a particular focus on gene- and gametogenesis-related sexual dimorphism observed in these model animals. In so doing, we aim to provide a firm foundation for the future study of sex-specific differences in meiosis at the molecular level.