• Title/Summary/Keyword: sexual dimorphism

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Sexual Dimorphism on the Shell of Littorina brevicula (Philippi) (Gastropoda: Littorinidae)

  • SON Min Ho
    • Korean Journal of Fisheries and Aquatic Sciences
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    • v.30 no.6
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    • pp.992-996
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    • 1997
  • Study on sexual dimorphism in Littorphism in Littorina brevicula should be interesting to examine that how the species prevent niche-overlap between the sexes? and how the species act differently in the reproductive roles of the sexes? Sexual dimorphism on the shell of L. brevicula was examined with 211 periwinkles larger than 5 mm shell length in Pusan, Korea. Sexual dimorphism was detected in the aperture length only. Aperture length of the female was longer than that of the male. A difference in the sexual role in the reproduction seems to be a probable explanation for the sexual dimorphism in the aperture length. The reproductive role of the male is to choose the best female and to transfer the sperm successfully by copulation, and the role of the female is to spawn their fertilised eggs into the seawater successfully. Perhaps females migrate to lower elevations on the shore than the males, so that they are submerged when they spawn. Because wave action at the lower area of the shore is stranger than that at the higher area on the shore, the females might need larger aperture size than the males to avoid dislodgement.

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Effects of Age, Brain-regional Selectivity, and Ovariectomy on Sexual Dimorphism of Organophosphate Pesticide Terbufos

  • Kim, Seung-Yong;KimKwon, Yun-Hee;Kwon, Oh-Seung
    • Proceedings of the PSK Conference
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    • pp.186.2-187
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    • 2003
  • A sexual dimorphism in terbufos (S-t-butylthiomethyl-O,O-diethyl phosphorodithioate: TBF) toxicity was not reported and remains unclear. Previously. we reported that TBF treatment showed sexual dimorphic effects on acetylcholinesterase (AchE) activity. We further investigated that sexual dimorphism of TBF was affected to age and brain-regional selectivity, and whether ovary plays an important role in the effect. (omitted)

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Analysis of Gonadosomatic Index (GSI) and Sexual Dimorphism of Coreoleuciscus splendidus in Age Groups (연령에 따른 쉬리 Coreoleuciscus splendidus의 성적이형과 생식소 숙도 분석)

  • Song, Ha-Yoon;Kim, Kyeong-Mu;Shin, A-Ri;Lee, Jin-Seok;Park, Hee-Won;Lee, Wan-Ok
    • Korean Journal of Ichthyology
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    • v.29 no.3
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    • pp.176-189
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    • 2017
  • Age estimation and sexual dimorphism of Coreoleuciscus splendidus were estimated using otolith, length-frequency distribution and 23 morphological measurements, from 245 individuals collected from September 2016, February and April 2017 in the Gapyeong stream, Han River, Korea. Result of age estimation of C. splendidus, we most examined were 2, 3 and 4-age, and the maximum observed ages were 5-age. Nine out of twenty-three morphometric measurements were significantly different between the genders. Anal fin have showing major sexual dimorphism in particular between adult individuals. This sexual dimorphism was based on extension of anal fin soft rays of male individuals. Therefore anal fin of males is always longer and wider than females. During spawning season male individuals possess nuptial tubercles on anal fin rays. However, another measurements and morphological characters does not exhibit sexual dimorphism in the between male and female individuals. The sexual dimorphism was observed to only over 2-years old individuals with sexual maturity. But juvenile and 1-years old individuals do not have sexual dimorphism with sexual maturity. Peak season of spawning was April to May and they start first spawning at 2-age. The ages at major spawning groups were most 3-age, and they maximum GSI index was 14.91 (female), 8.96 (male) at 5-age, respectively.

Sexual Dimorphism in Eightspine Stickleback, Pungitius sinensis: Gasterosteidae (가시고기(Pungitius sinensis: Gasterosteidae)의 성적 이형)

  • 채병수;양홍준
    • The Korean Journal of Zoology
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    • v.33 no.3
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    • pp.260-265
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    • 1990
  • Pungitius sinensis specimens were collected from the Namdae River and Chusu River drained into Sea of Japan, and their morphological characters were investigated to determine if this species shows sexual dimorphism. The ratio of the head length to the body length revealed marked sexual difference; the head length in males was longer than in females. The snout length and body depth at anus showed a tendency to be larger in males than in females. This dimorphism seems to be related to breeding habits. The ethological significance of the larger head of males was discussed.

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Sex and Population Differences in Intelligence Are Partly Caused by Sexual Selection: Hn Evolutionary Hypothesis

  • Piffer, Davide
    • Interdisciplinary Bio Central
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    • v.6 no.4
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    • pp.2.1-2.7
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    • 2014
  • Sexual dimorphism in intelligence suggests that this phenotype is a sexually selected trait. This view is supported by an overrepresentation (compared to the autosomal genome) of genes affecting cognition on the X chromosome. The aim of this study is to test the hypothesis that sexual selection can explain sex and country-level differences in performance on tests of fluid intelligence. Nationally representative samples from N = 44 countries were obtained from the Programme for International Student Assessment (PISA) Creative Problem Solving (CPS), which evaluates the core of intelligence, that is novel problem solving ability. Sexual selection has the double effect of increasing the prevalence of a favored phenotype and reducing genetic variation in sexually selected traits. Matching these predictions from evolutionary theory, the average country fluid intelligence is positively correlated to sexual dimorphism after partialling out per capita GDP and the latter in turn is inversely correlated to variance in intelligence scores within populations. Males have a higher variance than females but there is a negative correlation between male-female difference in variance and sexual dimorphism in intelligence, suggesting that selection reduces variance more in the selected sex. Average country male height is negatively correlated to sexual dimorphism in intelligence, a fact that supports the notion of a trade-off between physical and intellectual competition in the context of access to females. The results of this study, if replicated, imply that genome-wide association studies of cognition may benefit from a focus on sex chromosomes, which so far have been neglected. Another implication of this study is that intelligence has continued to evolve after different human populations migrated out of Africa and possibly up to the 19th century, as suggested by the substantial variability in sex differences even between neighbouring countries.

Sexual Size Dimorphism of the Mouthpart and Antenna of Cyllorhynchites ursulus in Korea (한국에 서식하는 도토리거위벌레(Cyllorhynchites ursulus) 구기 및 더듬이 길이의 성적이형성 연구)

  • Kim, Ji Young;Kim, Yung Kun;Lee, Yoo Ran;Lee, Eunok
    • Korean Journal of Environmental Biology
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    • v.35 no.4
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    • pp.515-520
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    • 2017
  • Sexual dimorphism of the mouthpart, antenna and mandible of the Cyllorhynchites ursulus in South Korea was studied with linear measurements. The mouthpart and antenna measurements were conducted with a stereoscopic microscope using 122 specimens (72 males and 50 females). Microscopic observation of the mandible were conducted with a Field Emission Scanning Electron Microscope (FE-SEM) using 103 specimens (73 males and 30 females). Results showed that the size difference between males and females was significant in the size of the mouthpart and antenna. On the other hand, we could not detect sexual size dimorphism in the microstructure of the mandible. The bivariate plots made by the result of Principal Component Analysis (PCA) and Discriminant Analysis (DA) showed a size dimorphism in the size of the mouthpart and the antenna between males and females. Based on our study, sexual dimorphism in the mouthpart and antenna exists in C. ursulus from the South Korean population, and this difference seems to be related to the behavioral differences between males and females.

Sexual Dimorphism in a River Sculpin(Cottus poecilopus Heckel) in Korea (한국산 둑중개 (Cottus poecilopus Heckel)의 성적 이형)

  • Byeon, Hwa-Kun
    • Korean Journal of Ichthyology
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    • v.8 no.1
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    • pp.14-21
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    • 1996
  • The sexual dimorphism of river sculpin (Cottus poecilopus Heckel) was investigated samples were collected from the Chiak stream from January 1993 to April 1994. Sexual dimorphism in body size and some morphological characteristics were observed in this species ; males were larger in size and had a larger mouth, anal fin, ventral fin and pevic fin than females. Males have a genital papilla and nuptial color, but females do not. Females may mate preferentially with large males. Larger males could be superior in nest defense and fanning of eggs to smaller ones, thus resulting in higher survival of eggs. Similary, the larger mouth in males could be advantageous in acquiring and defending their nests. Such sexual dimorphism in this species may reflect to outcome of sexual selection.

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Sexual Dimorphism in Morphometric Characteristics of Korean Chub Zacco koreanus (Pisces, Cyprinidae)

  • Kim, Young-Ja;Zhang, Chang-Ik;Park, In-Seok;Na, Jong-Hun;Olin, Paul
    • Journal of Ecology and Environment
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    • v.31 no.2
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    • pp.107-113
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    • 2008
  • We measured a set of 37 morphological characteristics in 97 specimens of adult Korean chub, Zacco koreanus, trapped in the Milyang River, Korea, in May and October of 2005. Twelve out of thirty-seven morphometric measurements were significantly different between the sexes. In particular, both the pectoral fin length and the direct distance between the insertion of the dorsal fin and the insertion of the anal fin were highly significant (p < 0.001). This sexual dimorphism may reflect the outcome of sexual selection in this species.

Comparative Analysis of Sexual Dimorphism Between Spawning Season and Non-Spawning Season in the Grass Puffer, Takifugu niphobles (복섬, Takifugu niphobles의 산란기 및 비산란기에 따른 성적이형 비교)

  • KIM, Dong Soo;GIL, Hyun Woo;LEE, Tae Ho;PARK, In-Seok
    • Journal of Fisheries and Marine Sciences Education
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    • v.29 no.2
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    • pp.447-452
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    • 2017
  • A closely associated set of characteristics was analyzed using both classical and truss dimensions to discriminate sexual dimorphism between spawning season and non spawning season in grass puffer, Takifugu niphobles. In non-spawning season, $1{\times}10/Ls$ of classical dimension was significantly different between male and female (P<0.05). In spawning season, $1{\times}9/Ls$ and $1{\times}10/Ls$ of classical dimension, $3{\times}8/Ls$, $3{\times}9/Ls$, $3{\times}10/Ls$, $4{\times}8/Ls$, $4{\times}9/Ls$ and $8{\times}9/Ls$ of truss dimension and $7{\times}9/HL$ of head part dimension were significantly different between male and female (P<0.05). The results of this study may be useful as basic information of other fish species to compare the change of sexual dimorphism between spawning season and non spawning season.

Morphometric Characteristics and Fin Dimorphism between Male and Female on the Marine Medaka, Oryzias dancena

  • Im, Jae Hyun;Gil, Hyun Woo;Lee, Tae Ho;Kong, Hee Jeong;Ahn, Cheol Min;Kim, Bong Seok;Kim, Dong Soo;Zhang, Chang Ik;Park, In-Seok
    • Development and Reproduction
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    • v.20 no.4
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    • pp.331-347
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    • 2016
  • Sexual dimorphism is the most conspicuous difference between the sexes. This study examines possible sexual dimorphism and the relative growth patterns of morphometric characteristics in the marine medaka, Oryzias dancena for their potential to help differentiate between males and females of this species. The von Bertalanffy growth parameters estimated by a non-linear regression method were $L_{\infty}=30.2mm$, K=3.22/year, and ${\tau}_0=-0.05$. All 18 characteristics measured showed a difference between males and females from 70 days after hatching. Each of these characteristics were significantly different between sexes (ANCOVA, P<0.05), and the ratio of standard length between sexes showed that males were larger than females for all five morphometric measurements. Fin length measurements were taken for 21 distances of anal fin and 7 distances of dorsal fin between landmarks. There were all differences for all dorsal fin rays between the males and the females and there is significant difference in 70 days after their hatch when the sexual dimorphism is presented. The significant difference (P<0.05) in fin ray for male and female was more greatly seen as they grow. Male marine medaka showed more rapid growth than females, with longer length, dorsal fins and anal fins. Differences in these characteristics will be useful during experiments when it is necessary to differentiate between sexes of marine medaka.