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| Registros recuperados: 84 | |
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| Diniz,Pedro. |
| Sexual dimorphism in birds is often attributed to sexual selection, but another interpretation suggests the evolution of this phenomenon by natural selection. Predation may be an important selective pressure, acting mainly on females. In this study, I tested the latter hypothesis on the coal-crested finch (Charitospiza eucosma Oberholser, 1905) in a neotropical savanna of the Central Brazil (Cerrado). I used capture methods for ascertaining the sex ratio in the population, and focal observations to gather behavioral data. My results show that the sex ratio is skewed toward males (1:1.39). Males were more vigilant, vocalized for longer periods of time, and used higher perches than females. Females foraged more, spent more time on parental care and remained... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Birds; Foraging behavior; Predation risk; Sex ratio; Sexual dimorphism. |
| Ano: 2011 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1984-46702011000200003 |
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| Teodósio,Érico A. O.; Masunari,Setuko. |
| A study on population structure of Aegla schmitti Hobbs III, 1979 was carried out at Mananciais da Serra, in the municipality of Piraquara, state of Paraná, Brazil (25º29'S, 48º58'W). The following aspects were treated: temporal fluctuation in abundance, sex ratio, reproductive period and size composition based on carapace length. The animals were colleted with traps, nets, measured and returned to the reservoirs. This population was sampled monthly, in two reservoirs (Carvalho and Carvalhinho) constructed in the headwater streams with swift current and steep gradient, located on west side of Serra do Mar mountains, from November, 2004 to January, 2006. The water temperature varied from 11.0 (July, 2005) to 18.2ºC (March, 2007), dissolved oxygen from 7.0... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Aeglid crab; Sex ratio; Temporal distribution. |
| Ano: 2009 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1984-46702009000100004 |
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| García-Ulloa,Diego; Landa-Jaime,Víctor; Góngora-Gómez,Andrés Martín; García-Ulloa,Manuel; Hernández-Sepúlveda,Juan Antonio. |
| ABSTRACT Symbiosis between decapods and mollusks provides a unique opportunity to examine some of the evolutionary strategies employed by marine invertebrates. We describe the sexual and reproductive traits of the pearl oyster shrimp, Pontonia margarita Verril, 1869, found symbiotically inhabiting the mantle cavity of the rugose pen shell, Pinna rugosa Sowerby, 1835. Solitary males and females (ovigerous and non-ovigerous) and heterosexual pairs (with ovigerous and non-ovigerous females) were found in a total of 47 rugose pen shells collected from a sandy area with seagrass meadows on the southeastern coast of the Gulf of California, Mexico. The body length (BL) of female P. margarita was correlated with the shell volume of their rugose pen shell host. The... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Monogamy; Promiscuity; Reproduction; Sex ratio; Shrimp-pen shell association. |
| Ano: 2019 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1984-46702019000100312 |
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| Oliveira,Elton C. de; Fávaro,Luís Fernando. |
| The present study characterizes the oogenesis and the ovarian maturation scale, and determines the reproductive period, type of spawning, recruitment period, and population variations in the reproductive process of the flatfish Achirus lineatus (Linnaeus, 1758). Specimens were sampled on a monthly basis in the shallow near shore area of the Paranaguá Bay, state of Paraná, Brazil, from March 2006 to February 2007. The specimens collected were measured for morphometric data (total length and total weight) and their gonads were exposed for macroscopic evaluation. The gonads were subsequently removed, weighed and processed for microscopic analyses. Six phases of the ovarian follicle development were defined, as well as five ovarian development stages. Growth... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Oogenesis; Maturity scale; Reproductive period; Type of spawning; Sex ratio. |
| Ano: 2010 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1984-46702010000400004 |
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| Costa,Tarso; Soares-Gomes,Abilio. |
| A population of the fiddler crab Uca rapax (Smith, 1870) found in Itaipu Lagoon, southeast Brazil, was sampled monthly from July 2006 to June 2007 in order to study population and reproductive features. The sex ratio of the population was statistically different from the expected (1:1) in almost every month, with a predominance of males. The reproductive cycle and the recruitment of juveniles were continuous, with two peaks. The fecundity ranged from 1.110 to 13.189 eggs (4.984 ± 2.493.8), not differing statistically among seasons. In contrast, the relative fecundity (F') and the reproductive intensity index (RII) were highest in the summer. Female size at the onset of sexual maturity was estimated as 6.1 mm and egg diameter ranged from 0.20 to 0.28 mm.... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Fiddler crab; Fecundity; Reproduction; Sex ratio. |
| Ano: 2009 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1984-46702009000400009 |
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| Ramírez-Chaves,Héctor E.; Tamayo-Zuluaga,Andrés Fernando; Henao-Osorio,Jose J.; Cardona-Giraldo,Alexandra; Ossa-López,Paula A.; Rivera-Páez,Fredy A.. |
| ABSTRACT Some species of mastiff bats, Molossus Geoffroy, 1805, inhabit human shelters such as houses and barns. Among them, the Pallas’s mastiff bat, Molossus molossus Pallas, 1766, is the most common species in South America. There are a few studies on this bat in Colombia, mostly on colony size, diet, ectoparasite records, and activity patterns in the Andean and Caribbean regions. Here, we provide information on the prevalence of chiggerfleas, Hectopsylla pulex (Haller, 1880), on M. molossus, along with molecular data on the flea, and its distribution in Colombia. In addition, we describe the size and sex ratio of the infested bat colony, located in the central Andes of Colombia. The bat colony was represented by ca. 45 individuals, of which 33 were... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Colony; Distribution; Ectoparasites; Sex ratio; Urban ecosystems. |
| Ano: 2020 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1984-46702020000100320 |
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| Dalosto,Marcelo M.; Palaoro,Alexandre V.; Oliveira,Davi de; Samuelsson,Évelin; Santos,Sandro. |
| Aeglids are freshwater anomurans that are endemic from southern South America. While their population biology at the species-level is relatively well understood, intraspecific variation within populations has been poorly investigated. Our goal was to investigate the population biology of Aegla platensis Schmitt, 1942 from the Uruguay River Basin, and compare our data with data from other populations. We estimated biometric data, sex ratio, population density and size-class frequencies, and frequencies of ovigerous females and juveniles, from the austral spring of 2007 until autumn 2008. Sexual dimorphism was present in adults, with males being larger than females. Furthermore, males and females were significantly larger than previously recorded for the... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Aeglids; Ecological plasticity; Intraspecific variation; Population density; Sampling methods; Sex ratio. |
| Ano: 2014 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1984-46702014000300002 |
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| SARNO,RONALD J.; FRANKLIN,WILLIAM L.; PREXL,WALTER S.. |
| Data were collected on general activity patterns and population characteristics of free-ranging Andean Condors Vultur gryphus in Torres del Paine National Park, Chile from July 1992 to June 1994 during 3,680 h of observation. Seasonal differences were evident in relative abundance and activity patterns. The mean number of condors sighted/ observation significantly higher in fall-winter than in spring-summer. There was a significant decrease from spring-summer to fall-winter in the percentage of observations during which we sighted solitary condors and a significant increase in the number of groups of condors. In addition, mean monthly maximum group size was significantly larger in fall-winter than spring-summer. The sex ratio (males:females ) of juveniles... |
| Tipo: Journal article |
Palavras-chave: Andean Condor; Activity; Patagonia; Sex ratio. |
| Ano: 2000 |
URL: http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0716-078X2000000100001 |
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| Baptista,Cassiana; Pinheiro,Marcelo A. Amaro; Blankensteyn,Arno; Borzone,Carlos A.. |
| Swimming crabs are commonly found in the otter-trawl shrimp fishery by-catch, which operate intensively in the Coastal Plain of Leste Beach, where is located Shangri-lá Beach (25°37'30"S and 48°25'08"W), Paraná State. This work aimed to study the population structure of Callinectes ornatus Ordway, 1863, the most abundant swimming crab in this beach. Between March 2000 and April 2001, fortnightly visits were accomplished in Shangri-lá at the fish market, where all swimming crabs of one otter-trawl were collected. The following data from each individual of C. ornatus were obtained: sex, carapace width (excluding lateral spines), weight, and the gonadal maturation stage, based on its color and size. Juveniles and mature males were dominant, mean sexual... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: By-catch; Maturity; Population biology; Sex ratio; Swimming crab. |
| Ano: 2003 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0101-81752003000400018 |
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| Zanatta, Naiara; Universidade Estadual de Maringá; Cionek, Vivian de Mello; Universidade Estadual de Maringá; Benedito, Evanilde; Universidade Estadual de Maringá. |
| This study aimed to characterize the reproductive strategies of fish from first order streams. Samplings were performed every three months from June 2008 to March 2009, using electric fishing at three streams: Conceição, Scherer and Jurema, located in the municipalities of Diamante do Norte and Amaporã, Paraná State, Brazil. We obtained the total weight (g), standard or total length (cm), sex and maturation stage for each specimen. Limnological data were obtained with portable equipments. The minimum length at first maturation was established for each population, and reproduction period was determined by analyzing the distribution of maturation stages. The sex ratio was obtained and tested (X2) for significant differences. Eight species were analyzed and... |
| Tipo: Reprodução |
Palavras-chave: 2.00.00.00-6 upper Paraná river basin; Sex ratio; Conservation unit; Reproductive stages 2.05.02.00-1. |
| Ano: 2013 |
URL: http://periodicos.uem.br/ojs/index.php/ActaSciBiolSci/article/view/10932 |
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| COLLA,MARÍA FLORENCIA; CÉSAR,INÉS I.. |
| Abstract: Freshwater amphipods of the genus Hyalella have a great importance in aquatic ecosystems due to their role in matter and energy cycling and its utilization as bioindicators of environmental health. The aim of this work was to analyze relevant population parameters of Hyalellapampeana, such as population density and structure, individual body size, sex ratio, fecundity and recruitment, and to study the possible relation of these parameters to variations in environmental variables. Samples were taken monthly during a one-year period (2006) at three small ponds in the Natural Reserve Island of Martín García, Argentina. The inland aquatic environments showed distinctive physicochemical characteristics, mainly related to pH and conductivity values.... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Freshwater amphipoda; Body size; Fecundity; Sex ratio. |
| Ano: 2019 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652019000100620 |
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| Valenzuela,Carlos Y. |
| Fraternal birth order (FBO) appears as a prenatal cause of 15% of homosexual males (gays) through mnemonic maternal anti-male factors. Non-right-handed men seem to be protected from homosexuality. Four hypotheses are proposed: (1) androgenic factors of non-right-handedness neutralize anti-male factors; (2) non-right-handedness and homosexuality are lethal or produce mental impairment; (3) non-right-handed male embryos are insensitive to anti-male factors; (4) mothers of non-right-handed fetuses do not produce anti-male factors. Studies of the sex ratio (SR) of older and younger siblings show: (1) a significant heterogeneity in the SR of siblings of right or non-right handed heterosexual men and women; (2) lesbians are born among siblings with high SR; (3)... |
| Tipo: Journal article |
Palavras-chave: Homosexuality; Handedness; Sex ratio; Birth order; Fetomoternal tolerance; Genetic distortions. |
| Ano: 2010 |
URL: http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0716-97602010000300012 |
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| Brito,Elizângela Silva de; Strussmann,Christine; Penha,Jerry Magno Ferreira. |
| Studies on population structure of freshwater turtles belonging to the family Chelidae are scarce in Brazil. Herein we describe the structure of a population of the chelid Mesoclemmys vanderhaegei in a Cerrado area in the municipality of Chapada dos Guimarães, Mato Grosso, Brazil. A total of 80 individuals were captured in five collecting sites, from January to March 2007: 42 adult females, 27 adult males, and 11 juveniles with undetermined sex. Among 80 individuals, 24% were recaptured, at least once. This is the first attempt to estimate the size of a population of Mesoclemmys vanderhaegei. Our results suggest that additional sampling efforts are needed for more accurate estimates of population structure. Nevertheless, they surely provide minimum values... |
| Tipo: Info:eu-repo/semantics/other |
Palavras-chave: Chelidae; Neotropics; Sex ratio; Population size; Freshwater turtles. |
| Ano: 2009 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1676-06032009000400024 |
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| Castiglioni,Daniela da Silva; Limberger,Marcio; Castro,Vanessa da Silva; Ubessi,Francieli. |
| Abstract The study of population and reproductive traits provides information about the ecological structure of natural populations. This study aimed to characterize dynamics and reproductive traits of Hyalella palmeirensis from a natural pond from southern Brazil. The amphipods were sampled monthly (August 2012 to July 2013) by a person with the aid of a hand net for 20 minutes. Ovigerous females and pre-copulatory pairs were individualized in the field. A total of 12,325 individuals were sampled, being 1,421 males, 6,983 females (including 215 ovigerous females) and 3,921 juveniles. Paired and unpaired males were significantly greater in size than females. There was a positive correlation between body size (CL) of paired males and females. Males and... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Fecundity; Body size; Hyalella palmeirensis; Sex ratio; Reproduction; Recruitment. |
| Ano: 2020 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1676-06032020000200204 |
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| Registros recuperados: 84 | |
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