Type Of Sexual Dimorphism Research Articles

Two new genera of coastal Talitridae (Amphipoda: Senticaudata) from Chile, with the first record of Platorchestia Bousfield, 1982 in the southeastern Pacific coast

Using samples of talitrid amphipods collected on the coast of Chile, we describe two new monotypic genera characterized by particular types of sexual dimorphism, and we report the first record of the genus Platorchestia Bousfield, 1982 in the southeastern Pacific coast. In the subfamily Platorchestiinae, the genus Atacamorchestia gen. nov. and its new species Atacamorchestia atacamensis sp. nov. was collected in marine rocky coasts, in several localities in northern Chile. This new taxon is characterized principally by presence of T setae in male appendages, a feature shared with the genus Vallorchestia from Australia, but with a different distribution of these structures. The first specimens of Platorchestia in the Southeastern Pacific were obtained in Antofagasta, northern Chile, however they were identified only to genus level because a more in-depth taxonomic analysis will be necessary to determine their status. Finally, in the subfamily Talitrinae, Lafkenorchestia gen. nov. and its new species Lafkenorchestia oyarzuni sp. nov. were found on rocky marine shores and in estuaries in southern Chile, between La Araucania and Los Lagos regions. This new taxon is characterized by distinct modifications in basis and merus of male pereopod 7, showing some morphological similarities with the New Zealand genera Subantarctorchestia and Pictonorchestia. For each species, descriptions and illustrations are presented.

Does cryptic dichromatism exist in the Saffron Finch (Sicalis flaveola)? Colorimetric variables and the avian visual model

Sexual dichromatism, a particular type of sexual dimorphism, occurs in several species and has been associated with sexual selection. In some cases, the differences are so small that they are imperceptible to humans, but possibly detected by birds. The objective measurement of color with spectrophotometers and detailed analyses according to the perception ability of the avian eye have revealed that some species that were once considered to be monochromatic, are in fact dichromatic and able to perceive these differences. In the tropics, the Saffron Finch (Sicalis flaveola) does not present marked sexual dimorphism in coloration, which makes studies in behavioral ecology, natural history and population dynamics difficult. To assess whether there is dichromatism in the species, the reflectance (between 300 and 700 ​nm) of ten body regions was measured in 196 wild adults in Cali-Colombia. Sex was determined using the CHD1 gene on the sex chromosomes. Reflectance spectra were analyzed using: colorimetric variables and the avian visual model. We found that reflectance shows a bimodal curve in all body regions, except the crown. Males presented higher reflectance at long wavelengths, while for females this occurred in ultraviolet wavelengths. For the visual model, we found that there are significant intrasexual differences; however only in crown coloration is there a possible perceived difference between sexes. We conclude that in the Saffron Finch there are color differences between the sexes in all regions considering the physical phenomenon (reflectance), but in general, when evaluating color perception (avian visual model), there are no differences between the sexes in most of the body regions. The intrasexual differences are significant, indicating the possibility of these being signals that influence social interactions in the species.

Distinct hormonal regulation of two types of sexual dimorphism in submandibular gland of mice.

The submandibular gland (SMG) of mice exhibits prominent sexual dimorphism in two aspects: the preferential development of granular convoluted tubule (GCT) cells and the earlier disappearance of granular intercalated duct (GID) cells in males after puberty. The former is dependent on androgens and thyroid hormones, whereas the hormonal dependence of the latter remains obscure. In the present study, we examined the effects of the postnatal administration of androgens and thyroid hormones to wild-type (WT) and androgen-receptor-knockout (ARKO) mice on these two types of sexual dimorphism by counting the numbers of GCT and GID cells labeled with nerve growth factor and submandibular gland protein C, respectively, as immunohistochemical markers. WT females and ARKO males and females exhibited a lower number of GCT cells and higher number of GID cells at 5 and 11weeks postpartum than WT males. The administration of dihydrotestosterone for 1-2weeks prior to these ages caused an increase in GCT cells and decrease in GID cells in WT females to similar levels as those in WT males, whereas it had no effects in ARKO, indicating that both types of sexual dimorphism are androgen-dependent. In contrast, the administration of thyroxine caused an increase in GCT cells but did not cause a decrease in GID cells in WT females or ARKO, indicating that the former is dependent on thyroid hormones, whereas the latter is not. The present results suggest that the two types of sexual dimorphism in the mouse SMG undergo distinct forms of hormonal regulation and, therefore, have different mechanisms.

Anthropometric Characteristics of Young Women in Yakutia, Depending on the Type of Sexual Dimorphism and Ethnos

Anthropometric Characteristics of Young Women in Yakutia, Depending on the Type of Sexual Dimorphism and Ethnos

Pathways to elaboration of sexual dimorphism in bird plumage patterns

Patterns, such as bars and spots, are common in birds. Some patterns can function in camouflage and/or communication and can benefit both males and females, paving the way for elaboration in sexual dimorphism. Historically, sexual dichromatism was predominantly considered to be a consequence of mating systems. However, the distribution of traits between the sexes is not always indicative of function; genetic correlation may cause traits to evolve in both sexes and traits may serve a social function in males and/or females. In addition, sexual dichromatism in bird plumage patterns can be composed of multiple types of patterns within and/or between the sexes. Therefore, there can be more than one type of dimorphism and some are more elaborate than others. Under classical models of genetic correlation, patterns evolve in both sexes followed by a loss of patterning in one sex. Elaborate types of sexual dimorphism in plumage patterns may be due to selection acting on existing patterns and are perhaps derived. Waterfowl (Anseriformes) and gamebirds (Galliformes) arguably have the most striking plumage patterns. Using 288 species from these orders I reconstructed the evolutionary history of plumage pattern dimorphism. There was little support for genetic correlation but elaborate types of dimorphism are probably derived. Backward and forward evolutionary transitions between different types of dimorphism can occur by loss or elaboration. These results demonstrate that plumage patterns are evolutionary labile and current forms may represent shifting adaptations to a changing environment.

New genus and species of Seirini (Collembola, Entomobryidae) from Caatinga Biome, Northeastern Brazil

ABSTRACT A new genus and a new species of Seirini (Entomobryidae) are described. The new genus, Tyrannoseira n. gen., is represented by three Brazilian Seira-like species with a peculiar type of sexual dimorphism: the first pair of legs of adult males bears several spine-like setae in distinct positions, the femur is enlarged and the tibiotarsus is slender. The combination of these morphological features produces clasping structures used during male-male interactions. The new genus is known only from Caatinga, a unique semi-arid biome exclusively present in Brazil. A new species, Tyrannoseira sex n. sp., is also described from Sao Joao do Cariri, Paraiba State. Seira raptora and S. bicolorcornuta, described from Caatinga, are also included in the newly described genus. An identification key for the three species of the new genus is also given. Sexual dimorphism and aspects of the systematics of Seira are discussed.

Ecology and mating competition influence sexual dimorphism in Tanganyikan cichlids

Sexual selection contributes strongly to the evolution of sexual dimorphism among animal taxa. However, recent comparative analyses have shown that evolution of sexual dimorphism can be influenced by extrinsic factors like mating system and environment, and also that different types of sexual dimorphism may present distinct evolutionary pathways. Investigating the co-variation among different types of sexual dimorphism and their association with environmental factors can therefore provide important information about the mechanisms generating variation in sexual dimorphism among contemporary species. Using phylogenetic comparative analyses comparing 49 species of Tanganyikan cichlid fishes, we first investigated the pairwise relationship between three types of sexual dimorphism [size dimorphism (SSD), colour dimorphism (COD) and shape dimorphism (SHD)] and how they were related to the strength of pre- and post-copulatory sexual selection. We then investigated the influence of ecological features on sexual dimorphism. Our results showed that although SSD was associated with the overall strength of sexual selection it was not related to other types of sexual dimorphism. Also, SSD co-varied with female size and spawning habitat, suggesting a role for female adaptations to spawn in small crevices and shells influencing SSD in this group. Further, COD and SHD were positively associated and both show positive relationships with the strength of sexual selection. Finally, the level of COD and SHD was related to habitat complexity. Our results thus highlight distinct evolutionary pathways for different types of sexual dimorphism and further that ecological factors have influenced the evolution of sexual dimorphism in Tanganyikan cichlid fishes.

Anatomic and acoustic sexual dimorphism in the sound emission system of Phoenicoprocta capistrata (Lepidoptera: Arctiidae)

Both sexes of Phoenicoprocta capistrata have functional tymbals. The scanning electron microscopy revealed differences in the morphology of these organs in males and females. Male tymbals have a well-developed striated band, constituted by 21 +/- 2 regularly arranged striae whereas female tymbals lack a striated band. This type of sexual dimorphism is rare in Arctiidae. The recording of the sound produced by moths held by the wings revealed that while males produced trains of pulses organized in modulation cycles, females produced clicks at low repetition rate following very irregular patterns. Statistically, there are differences between sexes in terms of the duration of pulses, which were 355 +/- 24 micros in the case of males and 289 +/- 29 micros for females. The spectral characteristics of the pulses also show sexual dimorphism. Male pulses are more tuned (Q(10) = 5.2 +/- 0.5) than female pulses (Q (10) = 2.7 +/- 0.5) and have a higher best frequency (42 +/- 1 kHz vs. 29 +/- 2 kHz). To our knowledge, this is the first report on an arctiid moth showing sexual dimorphism in tymbal's anatomy that leads to a best frequency dimorphism. Males produce sound at mating attempts. The sounds recorded during mating are modulation cycles with the same spectral characteristics as those recorded when males are held by the wings. The morphological and acoustic features of female tymbals could indicate a process of degeneration and adaptation to conditions under which the emission of complex patterns is not necessary.

Ontogeny and sexual dimorphism in the Middle/Late Devonian rhomboentomozoid ostracod <i>Franklinella</i>

Abstract. A large number of three-dimensionally preserved, pyritized specimens of different instars of the rhomboentomozoid ostracod Franklinella (Franklinella) lysogorensis n. sp. were recovered from a mudstone of the Givetian/Frasnian transition beds at Wzdół in the Holy Cross Mountains, Poland. Seven growth stages are identified. Sexual dimorphism is manifested by differences of ribbing pattern in adults. Within the superfamily Entomozoacea, the presence of two types of sexual dimorphism is suggested: ornamental in rhomboentomozoids and domiciliar in entomoprimitiids. Formerly poorly known morphological features of the rhomboentomozoids, including the anteroventral indentation and a contact list ornamented by fine striation, are described.

Sexual dimorphism in relation to swarming and pair formation patterns in leptocerid caddisflies (Trichoptera: Leptoceridae)

North European Leptoceridae (Trichoptera) perform three types of swarming flight patterns: (1) swarming males of Athripsodesand Ceracleafly in horizontal zigzag patterns over the water surface, (2) the Mystacidesspp. perform vertical zigzag movements, and (3) the flight of males of Triaenodes unanimisMcLach. is a mixture of the horizontal and vertical zigzagging. Also three groups of pair formation behavior can be distinguished. In the first group, of Athripsodesand Ceraclea,the females fly into the male swarms, where they are grasped and carried to the riparian vegetation by the flying males with the females hanging upside-down in genitalia coupling. In the second group, a Mystacidesfemale is caught by a male, when approaching a swarm and both use their wings to fly in tandem to the shore where they copulate. In the third group, of Triaenodes bicolor(Curt.) and Oecetis lacustris(Curt.), the males fly searching for females sitting on aquatic plants and when a female is found the male lands and they copulate immediately while clinging to the plant. The different swarming and mating behaviors might have favored selection for three types of sexual dimorphism: (1) longer forewings in males than females in species which fly in copula, (2) larger eyes in males of the vertically zigzagging species, and (3) much smaller males in the group where males search for females sitting on aquatic plants. In the second group approaching females are detected by males before reaching the swarm and in the third group the female almost always mates with the male which is the first to find her. In conclusion, we suggest that females of Athripsodesand Ceracleahave a greater choice among swarming males than do females of Mystacides, T. bicolor,and O. Lacustris.

A New Species of Oribatoid Mite from Guam with a Key to the Species of the Genus Nasozetes Sellnick 1930 (Acarina, Oribatei)

Among mites collected on Guam in July 1946 was a species of Nasozetes found on the breadfruit (Artocarpus altilis). This mite herein described as new is closely related to the typical species, Nasozetes sumatrensis Sellnick (1930), and to Nasozetes choerognathus Willmann (1931b) the only 2 previously described species of this genus which belongs in the family Eremaeidae Willmann (1931a). The main generic character is an unusual sexual dimorphism in which the males possess a prominent anterior extension of the rostrum which is expanded into a circular disc or nose (Figs. A, E & F). This rostral expansion is much reduced in the females of N. sumatrensis and is entirely absent from the females of the new species (Fig. C). There are no descriptions of the females of N. choerognathus; therefore it is impossible to determine if this species exhibits the same type of sexual dimorphism. This condition is not known to be present in any other genus of the oribatoid mites. The author has been able to study this mite through the courtesy of Dr. E. W. Baker, Acarologist, Entomology Research Branch, U. S. Dept. of Agriculture. The material was collected by Dr. H. K. Townes during an entomological survey of Micronesia under the auspices of the U. S. Commercial Co., Honolulu, T. H.