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OBJECTIVE: To determine reasons for horses to have neck radiographs performed, the incidence of transposition of the ventral lamina of C6 onto C7 (TC67), and the final diagnoses for all horses. Our hypotheses were to find a similar incidence of TC67, as has been previously reported, and an increased incidence of neck pain and dysfunction in horses with TC67. ANIMALS: 135 horses. METHODS: Retrospective observational study. Medical records of 135 horses with cervical vertebral column radiographs between 2020 and 2022 were assessed. Patient signalment, reasons for radiographs, radiographic findings, and diagnoses were analyzed. The Shapiro-Wilk test was used for normality determination. Nonparametric tests were used to analyze data. RESULTS: 20% of horses were diagnosed with TC67. Significantly more horses with TC67 were warmblood horses (63%); TC67 was found in 28% of warmblood horses. There was no significant difference in signalment or whether horses were in work between the groups, although significantly more horses with TC67 performed in English disciplines (71%). No differences in reasons for examination or final diagnoses of neurologic disease, cervical orthopedic disease, or lameness were present between groups. In horses with neck pain, TC67 was significantly more common (31%) than in horses without (18%). CLINICAL RELEVANCE: Our results indicated that TC67 occurs more in warmblood horses. In the small group of horses with neck pain reported, TC67 was more commonly seen than in those without. Given the complexity of this region and the paucity of studies exploring neck pain and neck biomechanics, we suggest the need for standardized prospective studies.
Assuntos
Vértebras Cervicais , Doenças dos Cavalos , Cervicalgia , Animais , Cavalos , Cervicalgia/veterinária , Estudos Retrospectivos , Masculino , Feminino , Radiografia/veterinária , Doenças do Sistema Nervoso/veterináriaRESUMO
Many actinopterygian fish groups, including fossil and extant polypteriforms and lepisosteiforms, fossil halecomorphs, and some basal teleosts, have stout bony scales covered by layers of ganoin-an enamel layer ornamented with minute tubercles. Ganoid scales preserve well as disarticulated remains and notably constitute most of the fossil record for polypteriform in both South America and Africa. Based on two variables (tubercle size and distance between tubercles), some authors reported that the ganoin tubercle ornamentation in these scales is constant within a species and differs between species and allows distinguishing species or at least groups of species. However, despite its promising potential for assessing polypteriform paleodiversity, this tool has remained unused, probably because the variables are not well defined, and intraspecific variation does not seem to have been considered. To address this gap, we aimed to test the intraspecific and intra-individual variation in the ornamentation of ganoid scales in the type species Polypterus bichir. We propose three different parameters to describe the tubercle ornamentation: the distance between contiguous tubercles centers, their density, and their relative spatial organization. With these parameters, we investigate the variation in ganoin ornamentation among four specimens and across different regions of the body. Our results show that the distribution of the tubercles is highly variable within a same species, regardless of the body region, and sometimes even between different sectors of a same scale. Moreover, the variation observed in P. bichir overlaps with the distribution described in the literature for several extant and fossil species. Thus far, the ornamentation of ganoid scales is not a reliable diagnostical feature for polypterids.
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Escamas de Animais , Animais , Escamas de Animais/anatomia & histologia , Peixes/anatomia & histologia , Peixes/classificação , Especificidade da EspécieRESUMO
KEY MESSAGE: Interspecific comparison of two Paspalum species has demonstrated that mating systems (selfing and outcrossing) contribute to variation (genetically and morphologically) within species through similar but mutually exclusive processes. Mating systems play a key role in the genetic dynamics of populations. Studies show that populations of selfing plants have less genetic diversity than outcrossing plants. Yet, many such studies have ignored morphological diversity. Here, we compared the morphological and molecular diversity patterns in populations of two phylogenetically-related sexual diploids that differ in their mating system: self-sterile Paspalum indecorum and self-fertile P. pumilum. We assessed the morphological variation using 16 morpho-phenological characters and the molecular diversity using three combinations of AFLPs. We compared the morphological and molecular diversity within and among populations in each mating system. Contrary to expectations, selfers showed higher morphological variation within populations, mainly in vegetative and phenological traits, compared to outcrossers. The high morphological variation within populations of selfers led to a low differentiation among populations. At molecular level, selfing populations showed lower levels of genotypic and genetic diversity than outcrossing populations. As expected, selfers showed higher population structure than outcrossers (PhiST = 0.301 and PhiST = 0.108, respectively). Increased homozygous combinations for the same trait/locus enhance morphological variation and reduce molecular variation within populations in selfing P. pumilum. Thus, selfing outcomes are opposite when comparing morphological and molecular variation in P. pumilum. Meanwhile, pollen flow in obligate outcrossing populations of P. indecorum increases within-population molecular variation, but tends to homogenize phenotypes within-population. Pollen flow in obligate outcrossers tends to merge geographically closer populations; but isolation by distance can lead to a weak differentiation among distant populations of P. indecorum.
Assuntos
Paspalum , Paspalum/genética , Diploide , Reprodução , Pólen , PlantasRESUMO
In the present study, the individual cultures of Proteus mirabilis (P. mirabilis) and Klebsiella pneumoniae (K. pneumoniae) were treated with morphologically modified silver nanoparticles (Ag NPs) and were found to display zones of inhibition of ~ 8 mm, 16 mm, 20 mm, and 22 mm (P. mirabilis) and 6 mm, 14 mm, 20 mm, and 24 mm (K. pneumoniae) at concentrations of 25 µg/ml, 50 µg/mL, 75 µg/mL, and 100 µg/mL, respectively. In addition, turbidity tests were performed based on O. D. values, which exhibited 92% and 90% growth inhibitions at 100 µg/mL concentration for P. mirabilis and K. pneumoniae, respectively. Furthermore, the IC50 concentration of Ag NPs was established for A549 lung cancer cells and found to be at 500 µg/mL. Evidently, the morphological variation of Ag NPs treated A549 lung cancer cells was exhibited with differential morphology studied by phase-contrast microscopy. The results demonstrated that the synthesized Ag NPs was not only efficient against gram-positive bacteria but also against gram-negative bacteria and A549 cancer cells, suggesting that the potential of these biosynthesized Ag NPs is a future drug discovery source for inhibiting bacteria and cancer cells.
Assuntos
Neoplasias Pulmonares , Nanopartículas Metálicas , Humanos , Prata/farmacologia , Descoberta de Drogas , Klebsiella pneumoniae , Proteus mirabilisRESUMO
Exposing an Evolutionary Algorithm that is used to evolve robot controllers to variable conditions is necessary to obtain solutions which are robust and can cross the reality gap. However, we do not yet have methods for analyzing and understanding the impact of the varying morphological conditions which impact the evolutionary process, and therefore for choosing suitable variation ranges. By morphological conditions, we refer to the starting state of the robot, and to variations in its sensor readings during operation due to noise. In this article, we introduce a method that permits us to measure the impact of these morphological variations and we analyze the relation between the amplitude of variations, the modality with which they are introduced, and the performance and robustness of evolving agents. Our results demonstrate that (i) the evolutionary algorithm can tolerate morphological variations which have a very high impact, (ii) variations affecting the actions of the agent are tolerated much better than variations affecting the initial state of the agent or of the environment, and (iii) improving the accuracy of the fitness measure through multiple evaluations is not always useful. Moreover, our results show that morphological variations permit generating solutions which perform better both in varying and non-varying conditions.
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ABSTRACT The Brazilian fauna of Meloidae is poorly studied, even though it includes more than 160 species. In this paper, we aimed at widening the knowledge on four species of blister beetles from this country. Specifically, we defined the uncertain range of Tetraonyx angulicollis, as extended in south-eastern Brazil rather than in Mexico, and implemented the description of the species with figures. We studied the taxonomy and distribution of three almost unknown species of Nemognatha from Brazil, São Paulo State, providing descriptions and figures of sexual characters and colour variability of N. beauregardi, to which is probably referable as a junior synonym of N. plaumanni, of N. rufoscutellaris and of N. cfr. gounellei. Moreover, we assigned these three species to the subgenus Pauronemognatha, recently recorded from South America.
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Euphlyctis cyanophlyctis (the skittering frog) is one of the most widespread species in Pakistan. Present study was aimed to know the presence of Euphlyctis cyanophlyctis in urban and rural areas of Lower Dir, the North-western Pakistan. A total of 33 frogs were collected, including 15 from rural and 18 from urban areas. The frogs were caught by hands covered with gloves instead of using nets. The collection was managed from August to October 2016 and from April to May 2018. Morphometric analysis, coloration as well as photographs of the frogs have been provided in detail. Skittering frogs were seen frequent in swampy areas near the water bodies. These frogs were mostly seen after sunset.(AU)
Euphlyctis cyanophlyctis (a rã que desliza) é uma das espécies mais comuns no Paquistão. O presente estudo teve como objetivo conhecer a presença de Euphlyctis cyanophlyctis em áreas urbanas e rurais de Lower Dir, noroeste do Paquistão. Um total de 33 sapos foram coletados, incluindo 15 de áreas rurais e 18 de áreas urbanas. As rãs foram apanhadas com as mãos cobertas com luvas em vez de redes. A coleta foi gerenciada de agosto a outubro de 2016 e de abril a maio de 2018. Análises morfométricas, coloração e também fotografias das rãs foram fornecidas em detalhes. Rãs saltitantes foram vistas freqüentemente em áreas pantanosas próximas aos corpos dágua. Essas rãs eram vistas principalmente após o pôr do sol.(AU)
Assuntos
Animais , Bufonidae/anatomia & histologia , Bufonidae/crescimento & desenvolvimentoRESUMO
Euphlyctis cyanophlyctis (the skittering frog) is one of the most widespread species in Pakistan. Present study was aimed to know the presence of Euphlyctis cyanophlyctis in urban and rural areas of Lower Dir, the North-western Pakistan. A total of 33 frogs were collected, including 15 from rural and 18 from urban areas. The frogs were caught by hands covered with gloves instead of using nets. The collection was managed from August to October 2016 and from April to May 2018. Morphometric analysis, coloration as well as photographs of the frogs have been provided in detail. Skittering frogs were seen frequent in swampy areas near the water bodies. These frogs were mostly seen after sunset.
Euphlyctis cyanophlyctis (a rã que desliza) é uma das espécies mais comuns no Paquistão. O presente estudo teve como objetivo conhecer a presença de Euphlyctis cyanophlyctis em áreas urbanas e rurais de Lower Dir, noroeste do Paquistão. Um total de 33 sapos foram coletados, incluindo 15 de áreas rurais e 18 de áreas urbanas. As rãs foram apanhadas com as mãos cobertas com luvas em vez de redes. A coleta foi gerenciada de agosto a outubro de 2016 e de abril a maio de 2018. Análises morfométricas, coloração e também fotografias das rãs foram fornecidas em detalhes. Rãs saltitantes foram vistas freqüentemente em áreas pantanosas próximas aos corpos dágua. Essas rãs eram vistas principalmente após o pôr do sol.
Assuntos
Animais , Bufonidae/anatomia & histologia , Bufonidae/crescimento & desenvolvimentoRESUMO
Abstract Euphlyctis cyanophlyctis (the skittering frog) is one of the most widespread species in Pakistan. Present study was aimed to know the presence of Euphlyctis cyanophlyctis in urban and rural areas of Lower Dir, the North-western Pakistan. A total of 33 frogs were collected, including 15 from rural and 18 from urban areas. The frogs were caught by hands covered with gloves instead of using nets. The collection was managed from August to October 2016 and from April to May 2018. Morphometric analysis, coloration as well as photographs of the frogs have been provided in detail. Skittering frogs were seen frequent in swampy areas near the water bodies. These frogs were mostly seen after sunset.
Resumo Euphlyctis cyanophlyctis (a rã que desliza) é uma das espécies mais comuns no Paquistão. O presente estudo teve como objetivo conhecer a presença de Euphlyctis cyanophlyctis em áreas urbanas e rurais de Lower Dir, noroeste do Paquistão. Um total de 33 sapos foram coletados, incluindo 15 de áreas rurais e 18 de áreas urbanas. As rãs foram apanhadas com as mãos cobertas com luvas em vez de redes. A coleta foi gerenciada de agosto a outubro de 2016 e de abril a maio de 2018. Análises morfométricas, coloração e também fotografias das rãs foram fornecidas em detalhes. Rãs saltitantes foram vistas freqüentemente em áreas pantanosas próximas aos corpos d'água. Essas rãs eram vistas principalmente após o pôr do sol.
RESUMO
Euphlyctis cyanophlyctis (the skittering frog) is one of the most widespread species in Pakistan. Present study was aimed to know the presence of Euphlyctis cyanophlyctis in urban and rural areas of Lower Dir, the North-western Pakistan. A total of 33 frogs were collected, including 15 from rural and 18 from urban areas. The frogs were caught by hands covered with gloves instead of using nets. The collection was managed from August to October 2016 and from April to May 2018. Morphometric analysis, coloration as well as photographs of the frogs have been provided in detail. Skittering frogs were seen frequent in swampy areas near the water bodies. These frogs were mostly seen after sunset.
Euphlyctis cyanophlyctis (a rã que desliza) é uma das espécies mais comuns no Paquistão. O presente estudo teve como objetivo conhecer a presença de Euphlyctis cyanophlyctis em áreas urbanas e rurais de Lower Dir, noroeste do Paquistão. Um total de 33 sapos foram coletados, incluindo 15 de áreas rurais e 18 de áreas urbanas. As rãs foram apanhadas com as mãos cobertas com luvas em vez de redes. A coleta foi gerenciada de agosto a outubro de 2016 e de abril a maio de 2018. Análises morfométricas, coloração e também fotografias das rãs foram fornecidas em detalhes. Rãs saltitantes foram vistas freqüentemente em áreas pantanosas próximas aos corpos d'água. Essas rãs eram vistas principalmente após o pôr do sol.
Assuntos
Animais , Anuros , PaquistãoRESUMO
The Batrachideinae subfamily is a well-defined and taxonomically stable taxon, with a pantropical distribution and an important representation in the Neotropical region. In this study, the characters and distributions of the genera and species are discussed based on a morphological analysis and a key to genera of the American Batrachideinae is also provided. New synonymies are established: Tettigidea Scudder, 1862 = Eotetrix Gorochov, 2012 syn. nov.; Batrachidea mucronata (Saint-Fargeau Serville, 1825) = Tettigidea granulosa Bruner, 1913 syn. nov.; Batrachidea planus (Hancock, 1907) = Batrachidea brevis (Hancock, 1909) syn. nov.; Tettigidea lateralis (Say, 1824) = Tettigidea nicaraguae Bruner, 1895 syn. nov.; Tettigidea lateralis (Say, 1824) = Tettigidea annulipes Bruner, 1910 syn. nov.; Tettigidea cuspidata Scudder, 1875 = Tettigidea corrugata Bruner, 1910 syn. nov.; Tettigidea cuspidata Scudder, 1875 = Tettigidea multicostata Bolívar, 1887 syn. nov.; Tettigidea chapadensis Bruner, 1910 = Tettigidea costalis Bruner, 1910 syn. nov.; Tettigidea chapadensis Bruner, 1910 = Tettigidea hancocki Bruner, 1910 syn. nov.; Tettigidea intermedia Bruner, 1910 = Tettigidea subatera Bruner, 1910 syn. nov.; Tettigidea scudderi Bolívar, 1887 = Tettigidea steinbachi Bruner, 1920 syn. nov. Three species are transferred from the genus Tettigidea to the genus Paxilla Bolívar, 1887: Paxilla mexicana (Hancock, 1915) comb. nov., Paxilla tecta (Morse, 1900) comb. nov., Paxilla nigra (Morse, 1900) comb. nov.; Tettigidea unicornis (Gorochov, 2012) comb. nov. is transferred from the genus Eotetrix Gorochov, 2012 to Tettigidea, and Batrachidea planus (Hancock, 1907) comb. nov. from Tettigidea to Batrachidea Serville, 1838. Five new species groups (lateralis, armata, cuspidata, paratecta and scudderi) are recognized in the genus Tettigidea. Neotype of Tettigidea lateralis lateralis is designated. Keys to the Batrachideinae genera and species of the most diverse American genera (Tettigidea and Paxilla) are also provided.
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Ortópteros , Distribuição Animal , AnimaisRESUMO
The region of Lagoa Santa, Minas Gerais, Brazil, is one of the most important karstic areas of the Brazilian Quaternary due to the faunistic diversity of living and extinct forms. Among them, some taxa remain poorly studied, as is the case of Calomys anoblepas Winge 1887. Despite the recent allocation of the taxon within Juliomys, its description and morphological analysis are condensed, based on comparative few specimens and on few informative characters. In this study, we investigate characters proposed to distinguish species of Juliomys, and reevaluate the taxonomic status of the fossil Juliomys anoblepas. We analyzed 80 cranio-dental morphological characters in 233 specimens represented by the four species currently recognized: J. pictipes (Osgood 1933), J. rimofrons Oliveira Bonvicino 2002, J. ossitenuis Costa, Pavan, Leite Fagundes 2007, and J. ximenezi Christoff, Vieira, Oliveira, Gonçalves, Valiati Tomasi 2016. We also performed principal component analysis on eight craniodental measurements available for the J. anoblepas hypodigm. The review of morphological systems and the evaluation of the characters used in the literature revealed that there are no diagnostic characters in the anterior portion of the skull and in the molar series of Juliomys, being difficult to differentiate the fossil from the other living species. Only six qualitative characters were variable and applicable to the hypodigm of J. anoblepas. Characters are polymorphic, invariable, or the fossil is not sufficiently complete to determinate its states. The taxon could not be morphometrically differentiated from J. pictipes and J. ossitenuis. Based on the results presented herein, we consider J. anoblepas as a nomen dubium and restrict its name to the taxon's hypodigm.
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Arvicolinae , Sigmodontinae , Animais , Brasil , Fósseis , Filogenia , RoedoresRESUMO
We perform a review of the Erythrolamprus reginae species group and putative related taxa (E. dorsocorallinus, E. zweifeli, and E. oligolepis), based on external morphology and hemipenial characters. We infer species boundaries among taxa traditionally associated with this group, recognizing two nominal subspecies (Erythrolamprus reginae reginae and E. r. macrosomus) in the species level. We propose the synonymy of E. r. semilineatus with E. reginae and recognize the validity of the related taxa, such as: E. dorsocorallinus, E. zweifeli, and E. oligolepis. In addition, two specimens occurring in the state Amapá, Brazil, are herein described as a new species. Therefore, we provide an identification key for the species of the group and discuss some of the combination of morphological features useful to delimitate the species of this group, in comparison with other representatives of the genus Erythrolamprus.
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Colubridae , Animais , BrasilRESUMO
We describe a new species of Pachyphloea from the Natural National Park (NNP) Chicaque, Cundinamarca in the Colombian Andes, providing data on the structure and variability of its eggs. In addition, we synonymize Grylloclonia n. syn. under Pachyphloea, and provide a key for distinguishing males and females of the known species. Finally, we discuss the taxonomical delimitation of genera within the tribe Xerosomatini, and highlight the necessity of carrying out additional studies in this particular taxon of stick insects.
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Insetos , Neópteros , Animais , Feminino , MasculinoRESUMO
Morphological variation is strongly related to variation in the ecological characteristics and evolutionary history of each taxon. To explore how geographical variation in morphology is related to different climatic gradients and phylogenetic structure, we analyzed the variation of morphological traits (body size, bill, and wing) of 64 species of tyrant flycatchers (Tyrannidae) distributed in Mexico. We measured these morphological traits in specimens from biological collections and related them to the climatic and topographic data of each collection locality. We performed the analyses separately at two levels: (1) the regional level and (2) the assemblage level, which was split into (assemblage I) lowland forests and (assemblage II) highland forests and other vegetation types. We also calculated the phylogenetic structure of flycatchers of each locality in order to explore the influence of climatic variables and the phylogenetic structure on the morphological variation of tyrant flycatchers, by means of linear mixed-effects models. We mapped the spatial variation of the relationship between morphological traits and environmental gradients, taking into account the phylogenetic structure. Important climatic variables explaining the morphological variation were those of temperature ranges (seasonality) and the results suggest that the phylogenetic clustering increases towards the highlands of Sierra Madre Oriental and Sierra Madre del Sur, and the lowlands of Balsas Depression. For the regional level, the spatial distribution of body size showed a pattern coincident with Bergmann's rule, with increasing in size from south to north. In the tropical lowland forests assemblage, body size tend to increase in seasonally dry forests (western Mexico) and decrease in the humid ones (eastern Mexico). In the assemblage of highland forests and other types of vegetation, morphological trait values increased northeast to southwest. Phylogenetic structure helped to explain the variation of morphology at the assemblage level but not at the regional level. The patterns of trait variation in the lowland and highland assemblages suggest that parts of morphological variation are explained both by the climatic gradients and by the lineage relatedness of communities. Overall, our results suggest that morphological variation is best explained by a varied set of variables, and that regression models representing this variation, as well as integrating phylogenetic patterns at different community levels, provide a new understanding of the mechanisms underlying the links among biodiversity, its geographical setting, and environmental change.
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Sexual dimorfism refers to morphological differences between males and females of a species. It may be a result of different selection pressures acting on either or both sexes and may occur in any sexually-reproducing dioecious species, including fishes. We analyzed 63 females and 63 adult males of Gymnorhamphichthys rondoni (Gymnotiformes) collected by us or deposited in museum collections. Sex was identified through abdominal dissection. We measured length from snout to posterior end of anal-fin, anal-fin length, distance from anus to anal-fin origin, distance from genital papilla to anal-fin origin, body width at beginning of anal-fin, and head length. Morphometric data submitted to a Principal Component Analysis (PCA) grouped males and females according to variables related to body size (along the first component) and to head length and body height along the second and third components. Females were larger than males, whereas males had proportionally larger heads and higher bodies than females. The urogenital papilla of males and females showed differences in shape, size and relative position on the body. The female papilla was elongated horizontally, larger than that of males, and was located on a vertical line below the eye, while the papilla of the males was vertically elongated and located on a vertical line below the operculum. To our knowledge, this is the first recorded case of sexual dimorphism in a species of Rhamphichthyidae, a condition that is now known in all the currently recognized families of Gymnotiformes. (AU)
Assuntos
Peixe Elétrico , Caracteres Sexuais , Gimnotiformes , CabeçaRESUMO
Sexual dimorfism refers to morphological differences between males and females of a species. It may be a result of different selection pressures acting on either or both sexes and may occur in any sexually-reproducing dioecious species, including fishes. We analyzed 63 females and 63 adult males of Gymnorhamphichthys rondoni (Gymnotiformes) collected by us or deposited in museum collections. Sex was identified through abdominal dissection. We measured length from snout to posterior end of anal-fin, anal-fin length, distance from anus to anal-fin origin, distance from genital papilla to anal-fin origin, body width at beginning of anal-fin, and head length. Morphometric data submitted to a Principal Component Analysis (PCA) grouped males and females according to variables related to body size (along the first component) and to head length and body height along the second and third components. Females were larger than males, whereas males had proportionally larger heads and higher bodies than females. The urogenital papilla of males and females showed differences in shape, size and relative position on the body. The female papilla was elongated horizontally, larger than that of males, and was located on a vertical line below the eye, while the papilla of the males was vertically elongated and located on a vertical line below the operculum. To our knowledge, this is the first recorded case of sexual dimorphism in a species of Rhamphichthyidae, a condition that is now known in all the currently recognized families of Gymnotiformes.(AU)
Dimorfismo sexual é caracterizado por diferenças entre machos e fêmeas de uma espécie. Pode estar presente em qualquer ser vivo dioico que se reproduza sexualmente, inclusive peixes. Analisamos 63 fêmeas e 63 machos adultos de Gymnorhamphichthys rondoni (Gymnotiformes) coletados por nós ou obtidos em coleções. O sexo foi determinado por dissecção abdominal. Medimos o comprimento do focinho até o final da origem da nadadeira anal, comprimento da nadadeira anal, distância da papila genital até a origem da nadadeira anal, distância do ânus até a origem da nadadeira anal, altura do corpo e comprimento da cabeça. Dados morfométricos submetidos a uma Análise de Componentes Principais (PCA) agruparam machos e fêmeas de G. rondoni em função de variáveis relacionadas ao tamanho do corpo ao longo do primeiro componente, ao comprimento da cabeça e à altura do corpo ao longo do segundo e terceiro componentes. Fêmeas foram maiores que os machos, enquanto machos tiveram a cabeça proporcionalmente maior e o corpo mais alto que as fêmeas. A papila urogenital de machos e fêmeas diferiu no formato, tamanho e posição relativa no corpo. A papila das fêmeas foi alongada horizontalmente, maior que a dos machos e localizada na linha vertical abaixo do olho, enquanto que a papila dos machos foi alongada verticalmente e localizada na linha vertical abaixo do opérculo. Até onde sabemos, esse é o primeiro caso registrado de dimorfismo sexual em uma espécie de Rhamphichthyidae, uma condição que é agora conhecida para todas as famílias atualmente reconhecidas de Gymnotiformes.(AU)
Assuntos
Animais , Caracteres Sexuais , Peixe Elétrico/anatomia & histologia , Gimnotiformes/anatomia & histologiaRESUMO
Evidence suggests that past climatic fluctuations affected speciation of extant cycads. However, empirical genetic and morphological evidence explaining patterns and processes of species diversification are scarce. There are some explanations for the origin and evolution of the genus Ceratozamia, but with inconclusive results. To elucidate the evolution of Ceratozamia, we used genetic and phenotypic sources as empirical data, which were applied in a 'proximate-ultimate' framework (ecological and evolutionary scale, respectively). Our results suggested that the evolutionary mechanisms of speciation were shaped by deterministic (natural selection-adaptation) driven by climatic conditions associated to water stress, and probably enhanced by stochastic processes (gene drift and inbreeding). In general terms, punctuated evolution models were those that best explained the patterns of speciation throughout the phylogenetic history of the lineages encompassed in the genus Ceratozamia. Finally, we provide empirical evidence on the tempo and mode of the evolution of a 'living plant fossil'.
Assuntos
Evolução Biológica , Zamiaceae/anatomia & histologia , Animais , Fósseis , Especiação Genética , Fenótipo , Filogenia , Filogeografia , Tamanho da Amostra , América do Sul , Especificidade da Espécie , Fatores de Tempo , Zamiaceae/genéticaRESUMO
BACKGROUND: There is a biogeographic break located at 30°S in the southeast Pacific, in a coastal area of strong environmental discontinuities. Several marine benthic taxa with restricted dispersal have a coincident phylogeographic break at 30°S, indicating that genetic structure is moulded by life history traits that limit gene flow and thereby promote divergence and speciation. In order to evaluate intraspecific divergence at this biogeographic break, we investigated the genetic and morphological variation of the directly developing beach isopod Excirolana hirsuticauda along 1900 km of the southeast Pacific coast, across 30°S. RESULTS: The COI sequences and microsatellite data both identified a strong discontinuity between populations of E. hirsuticauda to the north and south of 30°S, and a second weaker phylogeographic break at approximately 35°S. The three genetic groups were evidenced by different past demographic and genetic diversity signatures, and were also clearly distinguished with microsatellite data clustering. The COI sequences established that the genetic divergence of E. hirsuticauda at 30°S started earlier than divergence at 35°. Additionally, the three groups have different past demographic signatures, with probable demographic expansion occurring earlier in the southern group (south of 35°S), associated with Pleistocene interglacial periods. Interestingly, body length, multivariate morphometric analyses, and the morphology of a fertilization-related morphological character in males, the appendix masculina, reinforced the three genetic groups detected with genetic data. CONCLUSIONS: The degree of divergence of COI sequences, microsatellite data, and morphology was concordant and showed two geographic areas in which divergence was promoted at differing historical periods. Variation in the appendix masculina of males has probably promoted reproductive isolation. This variation together with gene flow restrictions promoted by life history traits, small body size, oceanographic discontinuities and sandy-beach habitat continuity, likely influenced species divergence at 30°S in the southeast Pacific coast. The degree of genetic and morphological differentiation of populations to the north and south of 30°S suggests that E. hirsuticauda harbours intraspecific divergence consistent with reproductive isolation and an advanced stage of speciation. The speciation process within E. hirsuticauda has been shaped by both restrictions to gene flow and a prezygotic reproductive barrier.