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Zheng P, Liang T, Shi L. Are toe fringes important for lizard burying in highly mobile sand? Front Zool 2024; 21:25. [PMID: 39343896 PMCID: PMC11440683 DOI: 10.1186/s12983-024-00546-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2024] [Accepted: 09/24/2024] [Indexed: 10/01/2024] Open
Abstract
Toe fringes are a key innovation for sand dwelling lizards, and the relationship between toe fringe function and substrate properties is helpful in understanding the adaptation of lizards to sand dune environments. We tested the sand burial performance of Phrynocephalus mystaceus on different sand substrates with toe fringe manipulation, with the aim of assessing whether the function of the toe fringes shifts under different substrate properties, especially in highly mobile substrates. The sand burial performance of P. mystaceus was influenced by substrate properties in relation to the toe fringe states of the lizard. After removal of the bilateral toe fringes, the sand burial ability score of P. mystaceus was significantly higher on sand substrates below 100 mesh than on native sand substrates. As the angle of stability of the substrate properties decreased, the sand burial performance of the lizard was even better after the bilateral toe fringes were removed. The results of the LASSO model and the path analysis model showed that the stability angle provided the opposite effect on sand burial performance in different toe fringe states. These results further suggest that the sand burial function of toe fringes may not be suitable for highly mobile sand substrates. It remains to be tested further whether the function of toe fringes is more important for running on sand.
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Affiliation(s)
- Peng Zheng
- Key Laboratory of Ecological Adaptation and Evolution of Extreme Environment Biology in Xinjiang, College of Life Sciences, Xinjiang Agricultural University, Ürümqi, 830052, Xinjiang, China
| | - Tao Liang
- Key Laboratory of Ecological Adaptation and Evolution of Extreme Environment Biology in Xinjiang, College of Life Sciences, Xinjiang Agricultural University, Ürümqi, 830052, Xinjiang, China
- Tel Aviv University, 69978, Tel Aviv, Israel
| | - Lei Shi
- Key Laboratory of Ecological Adaptation and Evolution of Extreme Environment Biology in Xinjiang, College of Life Sciences, Xinjiang Agricultural University, Ürümqi, 830052, Xinjiang, China.
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Lupu DC, Monedero I, Rodriguez-Ruiz C, Pita M, Turiegano E. In support of 2D:4D: More data exploring its conflicting results on handedness, sexual orientation and sex differences. PLoS One 2023; 18:e0280514. [PMID: 37607180 PMCID: PMC10443882 DOI: 10.1371/journal.pone.0280514] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Accepted: 12/28/2022] [Indexed: 08/24/2023] Open
Abstract
In the last few years, several studies have questioned the value of the second-to-fourth digit ratio (2D:4D) as a measure of exposure to sex hormones before birth. Controversy has also extended to the 2D:4D association with individual features previously related to this exposure such as handedness and sexual orientation. Given that it has been argued that sex differences in 2D:4D could be a consequence of body-size differences, we have tested in a large sample the allometric relationship between finger lengths and body size. Our results show that the association is either allometric or isometric, depending on the analyses performed. In any case, the deviation from isometry is not large enough to explain the typically observed sex difference in this trait. We have also tested the association between sexual orientation and 2D:4D, finding a relationship between 2D:4D and sexual orientation in men but not in women. We attribute this discordance with previously published meta-analysis to differences in genetic background, a variable that has gained relevance in recent years in studies involving 2D:4D. Finally, we did not find any relationship between 2D:4D and handedness, evaluated through self-reported preference and hand performance. Our main conclusion is that 2D:4D shows differences between sexes beyond their disparity in body size. In our opinion, 2D:4D can be used cautiously as an indicator of intrauterine exposure to sex hormones taking into account some considerations, such as analysing a very large sample and taking careful measurements of the ethnicity of the sample.
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Affiliation(s)
| | - Ignacio Monedero
- Departamento de Fisiología, Universidad Autónoma de Madrid, Madrid, España
| | | | - Miguel Pita
- Departamento de Biología, Universidad Autónoma de Madrid, Madrid, España
| | - Enrique Turiegano
- Departamento de Biología, Universidad Autónoma de Madrid, Madrid, España
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Kaczmarski M, Kaczmarek JM, Jankowiak Ł, Kolenda K, Tryjanowski P. Digit ratio in the common toad Bufo bufo: the effects of reduced fingers and of age dependency. ZOOLOGICAL LETTERS 2021; 7:5. [PMID: 33766147 PMCID: PMC7992345 DOI: 10.1186/s40851-021-00174-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Accepted: 03/11/2021] [Indexed: 06/12/2023]
Abstract
INTRODUCTION Despite the growing number of studies describing digit ratio patterns in tetrapods, knowledge concerning certain basic issues is still scarce. In lower vertebrates such as tailless amphibians (Anura), the numbering of individual fingers on the forelimbs and their homology with the fingers of other vertebrates pose an unsolved problem. Based on reviewed data on anuran limb development, we argue that the correct finger numbering scheme should be based on the assumption that the first finger, not the fifth finger, was reduced on the forelimbs. We analyzed the digit ratio in the common toad (Bufo bufo, Bufonidae), a species characterized by well-developed sexual dimorphism whereby females are larger than males, using both numbering schemes present in the literature. RESULTS We found that the digit ratio on hindlimbs differed significantly between the sexes only in the cases of left 2D:3D, with lower digit ratios in females, and of left 3D:4D, with lower digit ratios in males. We found that sex was the only significant variable for forelimbs, differentiating 2D:3D on the left forelimb, with lower digit ratios in females; 2D:4D on the right forelimb, with lower digit ratios in males; and 3D:4D on both forelimbs, with lower digit ratios in males. These results relate to variant II reflecting the hypothesis that the first digit was reduced during phylogenesis. There was no relationship between the body size (SVL) of individuals and any digit ratio, excluding 2D:4D on the right forelimbs in models with age variables. Additionally, for a subset of data where individual age was known, the models indicated that age was linked to significant differences in 2D:4D and 3D:4D on the left hindlimbs, while age, SVL, and sex influenced 2D:4D on the right forelimbs. CONCLUSION We emphasize the importance of the problem of the correct numbering of forelimb digits in Anura and, under the assumption that it was the fifth digit that was reduced, argue that earlier results on digit ratio in this group should be interpreted with caution. The detected relationship between digit ratio and age in amphibians expands our knowledge, indicating that the age of individuals should be included in future digit ratio studies. This relationship may also apply to studies using digit ratio as a noninvasive indicator of endocrine disruption in amphibians.
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Affiliation(s)
- Mikołaj Kaczmarski
- Institute of Zoology, Poznań University of Life Sciences, Wojska Polskiego 71c, PL 60-625 Poznań, Poland
| | - Jan M. Kaczmarek
- Institute of Zoology, Poznań University of Life Sciences, Wojska Polskiego 71c, PL 60-625 Poznań, Poland
| | - Łukasz Jankowiak
- Institute of Biology, University of Szczecin, Wąska 13, PL 71-415 Szczecin, Poland
| | - Krzysztof Kolenda
- Amphibian Biology Group, Department of Evolutionary Biology and Conservation of Vertebrates, Institute of Environmental Biology, University of Wrocław, Sienkiewicza 21, PL 50-335 Wrocław, Poland
| | - Piotr Tryjanowski
- Institute of Zoology, Poznań University of Life Sciences, Wojska Polskiego 71c, PL 60-625 Poznań, Poland
- Faculty of Environmental Sciences, Czech University of Life Sciences Prague, Kamýcká 129, 165 00 Prague 6, Czech Republic
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Miranda KG, Goulart MJ, Galdino CB. Digit ratio in three species of tropidurid lizards. HERPETOZOA 2021. [DOI: 10.3897/herpetozoa.34.e59064] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Proportions between pairs of digits are linked to fitness in tetrapods and they can be influenced by sex hormones through individuals’ ontogenies. Therefore, in many species, the proportions amongst finger length ratios (referred as digit ratio, i.e. 2D second and 4D fourth digits) can differ between males and females. We investigated whether the three most commonly used forelimb digit ratios are sexually dimorphic in three tropidurid species. In one of the three lizard species, Eurolophosaurus nanuzae, males and females differ for only 2D:4D digit ratio. Otherwise, our results on the studied Tropidurus species conform to previous studies showing no differences in digit ratios between males and females. Hence, it might be the case of local selective forces shaping interpopulation variation in the expression of sexual dimorphism for digit ratio.
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Rostovtseva VV, Mezentseva AA, Windhager S, Butovskaya ML. Second-to-fourth digit ratio and facial shape in Buryats of Southern Siberia. Early Hum Dev 2020; 149:105138. [PMID: 32750625 PMCID: PMC7374133 DOI: 10.1016/j.earlhumdev.2020.105138] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/21/2020] [Revised: 07/08/2020] [Accepted: 07/14/2020] [Indexed: 11/29/2022]
Abstract
BACKGROUND The 2nd-to-4th digit ratio (2D:4D) is a putative predictor of a prenatal exposure to sex hormones. 2D:4D is sexually dimorphic (males < females). Studies, linking digit ratio and full facial shapes among Europeans, show that a low 2D:4D is associated with a set of male-specific facial features. Buryats - Mongolian people from Southern Siberia - demonstrate a different pattern of facial sexual dimorphism than Europeans (narrower and more vertically elongated faces in men as opposed to women). AIM The aim of the present study was to investigate the association between facial shape and the 2D:4D in comparison to the pattern of facial sexual dimorphism in Buryats. SUBJECTS Buryats: 88 men and 80 women aged 20 ± 2 years. OUTCOME MEASURES To assess relationship between facial shape and 2D:4D we used a geometric morphometric approach based on standardized full-face frontal photographs and direct measurements of the digit lengths among right-handed individuals. RESULTS The results revealed that 2D:4D was associated with facial morphology in Buryat men, and to a lesser extent in women. Narrower faces, elongated in the vertical direction, and a narrower lower facial outline, were characteristic of Buryat men with low 2D:4D ratios, which corresponded to the male-like facial shapes in Buryats. CONCLUSIONS In Europeans, such facial features were reported for men with a high 2D:4D, which corresponded more to female-like European facial shapes. Hence, our results show that sex-specific morphogenesis in humans is multidirectional, and that digit ratio is capable of predicting sex-specific facial traits even in populations with differing sexually-dimorphic morphology.
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Affiliation(s)
- Victoria V. Rostovtseva
- Institute of Ethnology and Anthropology, Russian Academy of Sciences, Leninskiy pr-t 32a, Moscow 119334, Russia,Corresponding author
| | - Anna A. Mezentseva
- Department of Ethnology, Lomonosov Moscow State University, Lomonosovskiy pr-t 27/4, Moscow 119192, Russia
| | - Sonja Windhager
- Department of Evolutionary Anthropology, University of Vienna, Althanstrasse 14, Vienna 1090, Austria
| | - Marina L. Butovskaya
- Institute of Ethnology and Anthropology, Russian Academy of Sciences, Leninskiy pr-t 32a, Moscow 119334, Russia,National Research University Higher School of Economics, Myasnitskaya str. 20, Moscow 101000, Russia
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Asymmetric Behavior in Ptyodactylus guttatus: Can a Digit Ratio Reflect Brain Laterality? Symmetry (Basel) 2020. [DOI: 10.3390/sym12091490] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
The digit ratio, an indicator of brain laterality, is the ratio of the second and fourth digits on the left (L24) or right foot (R24). Much of the research on the digit ratio and brain laterality focuses on primates, rather than other species such as reptiles. We tested whether the digit ratio in the gecko Ptyodactylus guttatus was associated with behaviors attributed to brain laterality. We examined risk-taking behavior (time spent under cover), foot preference (which foot was the first to start moving) and the side from which geckos bypassed an obstacle, in relation to the digit ratio. Geckos with longer fourth digits on their left hind foot (higher digit ratio) spent more time under cover. Geckos starting to move with their left leg were much more likely to bypass obstacles from the right side, and vice versa. This is the first evidence of laterality being associated with the digit ratio in reptiles. Comparisons among vertebrates are needed in order to decipher the evolutionary origin of the commonalities and peculiarities of brain asymmetry and disentangle the patterns and drivers of our evolutionary tree.
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Lofeu L, Brandt R, Kohlsdorf T. Digit identity matters: origin and evolution of sexual dimorphism in the digit lengths of tropidurid lizards. Biol J Linn Soc Lond 2020. [DOI: 10.1093/biolinnean/blaa088] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
Abstract
Sexual dimorphism in digit lengths reflects phenotypic evolution mediated by developmental steroids. Differences in the identity of the sexually-dimorphic digit may evolve if the concentrations of sex-steroid receptors in the digit are easily modified and the initial changes have low impact on fitness. Accordingly, sexual dimorphism in digit lengths might initially originate under neutral selective regimes, being subsequently co-opted by embryonic hormonal effects on sensitive traits that are more likely to be targeted by selection. Correlated variation among sexually-dimorphic traits might therefore reflect pleiotropic hormonal modulation during development. Moreover, the identity and trend of the sexually-dimorphic digit might be evolutionarily labile even among closely-related species. We evaluated this model by assessing the identity of sexually-dimorphic digits among 11 Tropiduridae lizard species and inferring evolutionary patterns of sexual dimorphism. Assuming that digit lengths can be used as a proxy for hormonal modulation of steroid-sensitive traits during development, we tested for evolutionary associations among sexual dimorphism of digit lengths, body size and other traits that may be direct targets of sexual selection in the Tropiduridae. Sexual dimorphism in digit lengths is evolutionarily labile in the Tropiduridae, and diversity, instead of conservatism, seems to rule developmental mechanisms underlying the evolution of sexual dimorphism in digit ratios.
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Affiliation(s)
- Leandro Lofeu
- Department of Biology, FFCLRP, University of São Paulo, Ribeirão Preto, São Paulo, Brazil
| | - Renata Brandt
- Department of Biology, FFCLRP, University of São Paulo, Ribeirão Preto, São Paulo, Brazil
- Science North, Sudbury, ON, Canada
| | - Tiana Kohlsdorf
- Department of Biology, FFCLRP, University of São Paulo, Ribeirão Preto, São Paulo, Brazil
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Butovskaya M, Rostovtseva V, Butovskaya P, Burkova V, Dronova D, Filatova V, Sukhodolskaya E, Vasiliev V, Mesa T, Rosa A, Lazebny O. Oxytocin receptor gene polymorphism (rs53576) and digit ratio associates with aggression: comparison in seven ethnic groups. J Physiol Anthropol 2020; 39:20. [PMID: 32795360 PMCID: PMC7427763 DOI: 10.1186/s40101-020-00232-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2020] [Accepted: 08/03/2020] [Indexed: 11/10/2022] Open
Abstract
Background The specific role of the oxytocin receptor (OXTR) gene polymorphisms in emotional support seeking, related to social norms and culturally normative behavior, has been discussed in several studies. Evidence on the association between aggression and OXTR polymorphisms has also been reported. The goal of the current study was to analyze the effect of the OXTR rs53576 polymorphism, prenatal testosterone effect (second-to-fourth digit ratio, or 2D:4D), and culture on aggression assessed with the Buss-Perry Aggression Questionnaire (BPAQ). Methods The data were collected in Russia and Tanzania and included seven ethnic groups of European, Asian, and African origin. The total sample included 1705 adults (837 males, 868 females). All the subjects were evaluated with the BPAQ. As a measure of prenatal androgenization, the second and fourth digits were measured directly from hand, and the digit ratios were calculated. All the participants provided buccal samples, from which genomic DNA was extracted, and the OXTR gene rs53576 polymorphism was genotyped. Statistical analysis was performed using SPSS version 23.0; the alpha level for all analyses was set at 0.05. Results The ethnic group factor was the most significant predictor of ratings on BPAQ (medium effect size for physical aggression, anger and hostility scales, and low for verbal aggression). To study the effect of sex, the OXTR polymorphism, and prenatal androgenization, we conducted the z-score transformation for BPAQ scales and 2D:4D for each ethnic group and pooled these data into new z-score variables. According to the GLM analysis after leveling the effects of culture (z-transformation), all four scales of BPAQ demonstrated association with sex (main effects), with men scoring higher on physical and verbal aggression and women scoring higher on anger and hostility. Anger and hostility scales were also associated with OXTR polymorphism and 2D:4D of the right hand. The lowest levels of anger and hostility were observed in individuals with the AA genotype, especially in men. Conclusions Our data suggest that both oxytocin (OXTR gene polymorphism) and fetal testosterone (2D:4D) may significantly affect emotional (anger) and cognitive (hostility) aggression in humans, given the leveling the role of culture.
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Affiliation(s)
- Marina Butovskaya
- Institute of Ethnology and Anthropology, Russian Academy of Sciences, Leninsky Prospect 32a, 119991, Moscow, Russia. .,National Research University Higher School of Economics, Moscow, Russia.
| | - Victoria Rostovtseva
- Institute of Ethnology and Anthropology, Russian Academy of Sciences, Leninsky Prospect 32a, 119991, Moscow, Russia
| | | | - Valentina Burkova
- Institute of Ethnology and Anthropology, Russian Academy of Sciences, Leninsky Prospect 32a, 119991, Moscow, Russia.,National Research University Higher School of Economics, Moscow, Russia
| | - Daria Dronova
- Institute of Ethnology and Anthropology, Russian Academy of Sciences, Leninsky Prospect 32a, 119991, Moscow, Russia
| | - Vasilisa Filatova
- Institute of Ethnology and Anthropology, Russian Academy of Sciences, Leninsky Prospect 32a, 119991, Moscow, Russia
| | - Eugenia Sukhodolskaya
- Federal Budget Institution of Science "Central Research Institute of Epidemiology" of The Federal Service on Customers' Rights Protection and Human Well-being Surveillance, Moscow, Russia
| | - Vasiliy Vasiliev
- Institute of Gene Biology, Russian Academy of Sciences, Moscow, Russia
| | - Tania Mesa
- Secció de Zoologia i Antropologia Biològica, Departament de Biologia Evolutiva, Ecologia i Ciències Ambientals, Facultat de Biologia, Universitat de Barcelona (UB), Barcelona, Spain
| | - Araceli Rosa
- Secció de Zoologia i Antropologia Biològica, Departament de Biologia Evolutiva, Ecologia i Ciències Ambientals, Facultat de Biologia, Universitat de Barcelona (UB), Barcelona, Spain.,Institut de Biomedicina de la Universitat de Barcelona (IBUB), Barcelona, Spain.,Centre for Biomedical Research Network on Mental Health (CIBERSAM), Instituto de Salud Carlos III, Barcelona, Spain
| | - Oleg Lazebny
- Koltzov Institute of Developmental Biology, Russian Academy of Sciences, Moscow, Russia
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Kaczmarski M, Ziemblińska K, Tryjanowski P. Sand lizards Lacerta agilis with higher digit ratios are more likely to autotomy. J Anat 2020; 237:1103-1113. [PMID: 32659045 DOI: 10.1111/joa.13277] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2019] [Revised: 05/16/2020] [Accepted: 06/18/2020] [Indexed: 12/21/2022] Open
Abstract
Digit ratio is a morphological feature regarded as a biomarker of the balance of sex hormones during early development. The exposure of embryos to a set of sex hormones and the mutual relations between those hormones cause the emergence of individual morphological and/or behavioural characteristics as well as differences between sexes. We have thus hypothesised that differences in one of these morphological traits-digit ratio-may be a proxy representing a tendency towards tail autotomy. The aim of this study is to investigate the digit ratio (2D:3D, 2D:4D, 3D:4D) of the sand lizard, Lacerta agilis, Lacertidae, a species characterised by well-developed sexual dimorphism, whereby females are larger than males. We also tested associations between patterns in digit ratio and caudal autotomy, a common defensive mechanism among lizards. To our knowledge, the relationship between a tendency towards autotomy and digit ratio pattern has never been researched. To date, studies on autotomy have mainly focused on the consequences, costs or evolutionary background of tail loss. Hence, researchers examined mostly the frequency of autotomy in the context of predatory pressure or habitat conditions, omitting an individual's behavioural tendency to shed its tail. However, behavioural traits can affect an individual's exposure to predator attack and consequently the need to use an anti-predator strategy. Thus, following this logic, dropping the tail may be the result of the lizard's intraspecific personality characteristics, resulting from the effect of hormones on behaviour or innate traits. Therefore, we suggest that the inclusion of autotomy as a factor explaining observed digit ratio patterns and their variability between taxa has great potential. We used computerised measurements of photographed limbs to determine the length of digits. We found that the digit ratios for all four limbs were significantly lower in females than in males, excluding the 3D:4D ratio for the right hindlimbs. Therefore, the results confirmed the pattern already observed for most lizards. The novel element in our study is the detection of the relationship between a tendency towards caudal autotomy and digit ratio. Individuals with a tendency towards autotomy have a higher 2D:4D ratio in the right forelimbs and a lower 2D:3D ratio in the right hindlimbs. Obtained results suggest that these morphological characteristics are most likely related to intraspecific differences (between bold and shy individuals) which consequently may determine an individual's reaction or susceptibility to be a prey and escape behaviour. Thus, our results are probably the first attempt to link digit ratio to the susceptibility of lizards to tail autotomy.
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Affiliation(s)
- Mikołaj Kaczmarski
- Institute of Zoology, Poznań University of Life Sciences, Poznań, Poland
| | - Klaudia Ziemblińska
- Department of Meteorology, Poznań University of Life Sciences, Poznań, Poland
| | - Piotr Tryjanowski
- Institute of Zoology, Poznań University of Life Sciences, Poznań, Poland.,Faculty of Environmental Sciences, Czech University of Life Sciences Prague, Prague 6, Czech Republic
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Stibbard-Hawkes DNE. No Association between 2D:4D Ratio and Hunting Success among Hadza Hunters. HUMAN NATURE (HAWTHORNE, N.Y.) 2020; 31:22-42. [PMID: 31838723 DOI: 10.1007/s12110-019-09359-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The ratio of index- and ring-finger lengths (2D:4D ratio) is thought to be related to prenatal androgen exposure, and in many, though not all, populations, men have a lower average digit ratio than do women. In many studies an inverse relationship has been observed, among both men and women, between 2D:4D ratio and measures of athletic ability. It has been further suggested that, in hunter-gatherer populations, 2D:4D ratio might also be negatively correlated with hunting ability, itself assumed to be contingent on athleticism. This hypothesis has been tested using endurance running performance among runners from a Western, educated, and industrialized population as a proximate measure of hunting ability. However, it has not previously been tested among actual hunter-gatherers using more ecologically valid measures of hunting ability and success. The current study addresses this question among Tanzanian Hadza hunter-gatherers. I employ a novel method of assessing hunting reputation that, unlike previous methods, allows granular distinctions to be made between hunters at all levels of perceived ability. I find no statistically significant relationship between digit ratio and either hunting reputation or two important hunting skills. I confirm that Hadza men have higher mean 2D:4D ratios than men in many Western populations. I discuss the notion that 2D:4D ratio may be the consequence of an allometric scaling relationship between relative and absolute finger lengths. Although it is difficult to draw clear conclusions from these results, the current study provides no support for the theorized relationship between 2D:4D ratio and hunting skill.
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Roy R, Kundu R, Sengupta M, Som P. Association between digit length ratio (2D:4D) and polycystic ovarian syndrome (PCOS)—A study among eastern Indian population. J ANAT SOC INDIA 2018. [DOI: 10.1016/j.jasi.2017.12.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Woodhead N, Hare KM, Cree A. Sexual Dimorphism of Digit-Length Ratio in a Viviparous Lizard: Influence of Age, but not Preservation State or Sex of Interuterine Twin. Anat Rec (Hoboken) 2018; 301:1169-1178. [PMID: 29544025 DOI: 10.1002/ar.23803] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2017] [Revised: 11/23/2017] [Accepted: 12/09/2017] [Indexed: 02/04/2023]
Abstract
The existence of sex differences in digit-length ratio (especially between the second and fourth digits, 2D:4D) is well established for humans from fetal life onwards, and has been linked with later performance. In rodents, the ratio is affected prenatally by exposure to androgens and estrogens, with some research suggesting an influence from sex of the neighbouring intrauterine fetus. However, the ubiquity and ontogenetic development of sexual dimorphism in digit ratios is not well established among wild amniotes. We report the first digit ratios for a gekkotan lizard, representing a speciose lineage in which viviparity has evolved independently from mammals and other reptiles. For the gecko Woodworthia "Otago/Southland", in which up to two embryos develop in separate uteri, we found: (1) significant sexual dimorphism in adults in 2D:3D of the right hindlimb only (larger in males), but not in 2D:4D for any limb; (2) no dimorphism in ratios for young juveniles, with no influence of sex of the interuterine twin, and no relationship with sprint speed; (3) in preserved tissues of the same juveniles, no sexual dimorphism in ratios, but a change in relative lengths of some digits with preservation. The ontogenetic pattern might be explained by altered sex-steroid exposure at the transition to adulthood rather than during prenatal development. Our results support a phylogenetic hypothesis that sauropsids (birds and reptiles) differ from mammals in the direction of sex difference, if present. Experiments are needed to establish the roles of androgens and estrogens in establishing these sex differences in lizards. Anat Rec, 301:1169-1178, 2018. © 2018 Wiley Periodicals, Inc.
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Affiliation(s)
- Nikita Woodhead
- Department of Zoology, University of Otago, PO Box 56, Dunedin, 9054, New Zealand
| | - Kelly M Hare
- Department of Zoology, University of Otago, PO Box 56, Dunedin, 9054, New Zealand
| | - Alison Cree
- Department of Zoology, University of Otago, PO Box 56, Dunedin, 9054, New Zealand
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Lofeu L, Brandt R, Kohlsdorf T. Phenotypic integration mediated by hormones: associations among digit ratios, body size and testosterone during tadpole development. BMC Evol Biol 2017; 17:175. [PMID: 28768472 PMCID: PMC5541650 DOI: 10.1186/s12862-017-1021-0] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2017] [Accepted: 07/26/2017] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND Developmental associations often explain phenotypic integration. The intersected hormonal regulation of ontogenetic processes fosters predictions of steroid-mediated phenotypic integration among sexually dimorphic traits, a statement defied by associations between classical dimorphism predictors (e.g. body size) and traits that apparently lack sex-specific functions (e.g. ratios between the lengths of Digits II and IV - 2D:4D). Developmental bases of female-biased 2D:4D have been identified, but these remain unclear for taxa presenting male-biased 2D:4D (e.g. anura). Here we propose two alternative hypotheses to investigate evolution of male-biased 2D:4D associated with sexually dimorphic body size using Leptodactylus frogs: I)'hypothesis of sex-specific digit responses' - Digit IV would be reactive to testosterone but exhibit responses in the opposite direction of those observed in female-biased 2D:4D lineages, so that Digit IV turns shorter in males; II) 'hypothesis of identity of the dimorphic digit'- Digit II would be the dimorphic digit. RESULTS We compiled the following databases using Leptodactylus frogs: 1) adults of two species from natural populations and 2) testosterone-treated L. fuscus at post-metamorphic stage. Studied traits seem monomorphic in L. fuscus; L. podicipinus exhibits male-biased 2D:4D. When present, 2D:4D dimorphism was male-biased and associated with dimorphic body size; sex differences resided on Digit II instead of IV, corroborating our 'hypothesis of identity of the dimorphic digit'. Developmental steroid roles were validated: testosterone-treated L. fuscus frogs were smaller and exhibited masculinized 2D:4D, and Digit II was the digit that responded to testosterone. CONCLUSION We propose a model where evolution of sexual dimorphism in 2D:4D first originates from the advent, in a given digit, of increased tissue sensitivity to steroids. Phenotypic integration with other sexually dimorphic traits would then occur through multi-trait hormonal effects during development. Such process of phenotypic integration seems fitness-independent in its origin and might explain several cases of steroid-mediated integration among sexually dimorphic traits.
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Affiliation(s)
- Leandro Lofeu
- Departamento de Biologia, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, 14040-901, Brazil
| | - Renata Brandt
- Departamento de Biologia, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, 14040-901, Brazil
| | - Tiana Kohlsdorf
- Departamento de Biologia, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, 14040-901, Brazil.
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14
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Tian H, Zhao X, Hu F, Hu H. Sex Determination According to the Lengths of Hand Bones in Rhesus Macaques (Macaca Mulatta). Anat Rec (Hoboken) 2017; 300:1741-1746. [PMID: 28681462 DOI: 10.1002/ar.23637] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2015] [Revised: 04/10/2017] [Accepted: 04/11/2017] [Indexed: 11/10/2022]
Abstract
Measurement of hand bone length has been used for sex determination in humans and nonhuman primates (McFadden and Bracht: Early Hum Dev 85 (2009) 117-124; El-Morsi and Al-Hawary: J Forensic Leg Med 20 (2013) 6-13). The aim of this study was to determine the sex of rhesus macaques (Macaca mulatta) on the basis of the lengths of corresponding rows of metacarpals and phalanges in a macaque population by means of developing discriminant functions. Measurements on direct dry bones only included lengths for 19 bones of the left hand in 39 macaques (consisting of 13 adult males and 26 adult females). The results revealed that the mean values of males were significantly greater than those of females for all of the metacarpals and phalanges. The results were obtained in 84.4% of accuracy from distal phalanges, 93.8% from middle phalanges, and 96.9% from both metacarpals and proximal phalanges, respectively. There was a remarkable difference in the magnitude of sex dimorphism in lengths of each section of the hand bones between the population of macaques and humans. This difference may be attributable to the interaction between genetic factors and various environmental factors. As sex differences of hand bones are population-specific (Lazenby: Am J phys Anthropol 118 (2002) 378-384; Lu, Huo, Shi, Peng, Dang, Jiao, Zhu, Zhong, and Chen: Acta Aantomica Sinica 39 (2008) 267-271; Eshak, Ahmed, and Gawad: J Forensic Leg Med 18 (2011) 246-252), the discriminant equations for all of the metacarpals and phalanges are applicable to the population of Macaca mulatta from the Taihang Mountain. Anat Rec, 2017. © 2017 Wiley Periodicals, Inc. Anat Rec, 300:1741-1746, 2017. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- Huaxiang Tian
- College of Fisheries, Henan Normal University, Xinxiang, 453007, China
| | - Xiaojin Zhao
- College of Fisheries, Henan Normal University, Xinxiang, 453007, China
| | - Fengxia Hu
- College of Fisheries, Henan Normal University, Xinxiang, 453007, China
| | - Haiyang Hu
- College of Fisheries, Henan Normal University, Xinxiang, 453007, China
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15
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Beaty LE, Emmering QC, Bernal XE. Mixed Sex Effects on the Second-to-Fourth Digit Ratio of Túngara Frogs (Engystomops pustulosus) and Cane Toads (Rhinella marina). Anat Rec (Hoboken) 2016; 299:421-7. [PMID: 26815928 DOI: 10.1002/ar.23322] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2015] [Revised: 12/01/2015] [Accepted: 12/21/2015] [Indexed: 11/06/2022]
Abstract
Sexual dimorphism in the ratio of digit lengths has been correlated to behavioral, physiological, and morphological traits in a variety of taxa. While sexual dimorphism in the second-to-fourth digit length ratio (2D:4D) is a well-established indicator of prenatal androgen exposure in mammals, investigations into the patterns of 2D:4D and the drivers of such variation in other taxa are lacking. We used linear mixed effects models to gain a mechanistic understanding of the factors that drive variation in the scaling relationship between the lengths of the second and fourth digits in two species of anurans: túngara frogs (Engystomops pustulosus) and cane toads (Rhinella marina). We found evidence for sexual dimorphism of the 2D:4D scaling relationship on the front feet of túngara frogs, with female frogs having a larger ratio than males resulting from a relatively longer second digit on females. To our knowledge, this mammal-like pattern of sex differences in digit ratio has not yet been reported for anurans. However, given the reduced number of digits on the front feet of anurans, and uncertainty about which digit was lost during evolutionary history, this apparent sexual dimorphism in the front feet of túngara frogs should be treated with caution. In contrast, we found no evidence of sexual dimorphism in 2D:4D on either the front or rear feet of cane toads. This study highlights ambiguities in 2D:4D across taxa and suggests that further research is needed to evaluate the effect of androgens on 2D:4D in animals other than placental mammals.
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Affiliation(s)
- Lynne E Beaty
- Department of Integrative Biology, Oklahoma State University, Stillwater, Oklahoma, USA
| | | | - Ximena E Bernal
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana, USA.,Smithsonian Tropical Research Institute, Gamboa, Republic of Panama
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16
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Nagy G, Blázi G, Hegyi G, Török J. Side-specific effect of yolk testosterone elevation on second-to-fourth digit ratio in a wild passerine. Naturwissenschaften 2016; 103:4. [PMID: 26732381 DOI: 10.1007/s00114-015-1328-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2015] [Revised: 11/26/2015] [Accepted: 12/19/2015] [Indexed: 11/30/2022]
Abstract
Second-to-fourth digit ratio is a widely investigated sexually dimorphic morphological trait in human studies and could reliably indicate the prenatal steroid environment. Conducting manipulative experiments to test this hypothesis comes up against ethical limits in humans. However, oviparous tetrapods may be excellent models to experimentally investigate the effects of prenatal steroids on offspring second-to-fourth digit ratio. In this field study, we injected collared flycatcher (Ficedula albicollis) eggs with physiological doses of testosterone. Fledglings from eggs with elevated yolk testosterone, regardless of their sex, had longer second digits on their left feet than controls, while the fourth digit did not differ between groups. Therefore, second-to-fourth digit ratio was higher in the testosterone-injected group, but only on the left foot. This is the first study which shows experimentally that early testosterone exposure can affect second-to-fourth digit ratio in a wild population of a passerine bird.
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Affiliation(s)
- Gergely Nagy
- Behavioural Ecology Group, Department of Systematic Zoology and Ecology, Eötvös Loránd University, Pázmány P. sétány 1/C, H-1117, Budapest, Hungary
| | - György Blázi
- Behavioural Ecology Group, Department of Systematic Zoology and Ecology, Eötvös Loránd University, Pázmány P. sétány 1/C, H-1117, Budapest, Hungary
| | - Gergely Hegyi
- Behavioural Ecology Group, Department of Systematic Zoology and Ecology, Eötvös Loránd University, Pázmány P. sétány 1/C, H-1117, Budapest, Hungary
| | - János Török
- Behavioural Ecology Group, Department of Systematic Zoology and Ecology, Eötvös Loránd University, Pázmány P. sétány 1/C, H-1117, Budapest, Hungary.
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17
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Balogová M, Nelson E, Uhrin M, Figurová M, Ledecký V, Zyśk B. No Sexual Dimorphism Detected in Digit Ratios of the Fire Salamander (Salamandra salamandra). Anat Rec (Hoboken) 2015. [PMID: 26199217 DOI: 10.1002/ar.23197] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
It has been proposed that digit ratio may be used as a biomarker of early developmental effects. Specifically, the second-to-fourth digit ratio (2D:4D) has been linked to the effects of sex hormones and their receptor genes, but other digit ratios have also been investigated. Across taxa, patterns of sexual dimorphism in digit ratios are ambiguous and a scarcity of studies in basal tetrapods makes it difficult to understand how ratios have evolved. Here, we focus on examining sex differences in digit ratios (2D:3D, 2D:4D, and 3D:4D) in a common amphibian, the fire salamander (Salamandra salamandra). We used graphic software to measure soft tissue digit length and digit bone length from X-rays. We found a nonsignificant tendency in males to have a lower 2D:3D than females; however, no sexual differences were detected in the other ratios. We discuss our results in the context of other studies of digit ratios, and how sex determination systems, as well as other factors, might impact patterns of sexual dimorphism, particularly in reptiles and in amphibians. Our findings suggest that caution is needed when using digit ratios as a potential indicator of prenatal hormonal effects in amphibians and highlight the need for more comparative studies to elucidate the evolutionary and genetic mechanisms implicated in sexually dimorphic patterns across taxonomic groups.
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Affiliation(s)
- Monika Balogová
- Institute of Biology and Ecology, Faculty of Science, P. J. Šafárik University, Košice, Slovakia
| | - Emma Nelson
- School of Medicine, University of Liverpool, Liverpool, United Kingdom.,Archaeology, Classics and Egyptology, University of Liverpool, Liverpool, United Kingdom
| | - Marcel Uhrin
- Institute of Biology and Ecology, Faculty of Science, P. J. Šafárik University, Košice, Slovakia.,Department of Forest Protection and Wildlife Management, Faculty of Forestry and Wood Sciences, Czech University of Life Sciences, Praha 6, Czech Republic
| | - Mária Figurová
- Clinic of Small Animals, University of Veterinary Medicine and Pharmacy, Košice, Slovakia
| | - Valent Ledecký
- Clinic of Small Animals, University of Veterinary Medicine and Pharmacy, Košice, Slovakia
| | - Bartłomiej Zyśk
- Department of Vertebrate Zoology and Human Biology, Institute of Biology, Cracow Pedagogical University, Kraków, Poland
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Van Damme R, Wijnrocx K, Boeye J, Huyghe K, Van Dongen S. Digit ratios in two lacertid lizards: sexual dimorphism and morphological and physiological correlates. ZOOMORPHOLOGY 2015. [DOI: 10.1007/s00435-015-0275-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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19
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Kaczmarski M, Kubicka AM, Tryjanowski P, Hromada M. Females Have Larger Ratio of Second-to-Fourth Digits Than Males in Four Species of Salamandridae, Caudata. Anat Rec (Hoboken) 2015; 298:1424-30. [PMID: 25704339 DOI: 10.1002/ar.23123] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2014] [Revised: 12/18/2014] [Accepted: 01/06/2015] [Indexed: 12/11/2022]
Abstract
Digit ratio (2D:4D) denotes the relative length of the second and fourth digits. It is considered to be a suitable biomarker of the in utero balance of fetal sex hormones, which affect early development of individuaĺs behavioral and morphological characteristics. In recent decades, digit ratio attracted a great attention in biology and psychology. However, for unmasking the biological basis of the phenomenon, extensive studies on non-human animals are necessary. Despite it was hypothesized that digit ratio is well conserved in all Tetrapoda, and there exist studies on mammals, birds, and reptiles, there are only two such study on anuran amphibians. Therefore, the aim of this study is to investigate the 2D:4D in the most basal salamanders, Caudata. We have studied digit ratio in four species of newts: Triturus cristatus, Mesotriton alpestris, Lissotriton montandoni, and Lissotriton vulgaris, using museum collection. We used computerized measuring of each limbś photos. We have found out that, in M. alpestris, females 2D:4D of all four limbs were significantly larger than in males. In L. montandoni and L. vulgaris, only 2D:4D of rear limbs significantly differed, in females being larger. In T. cristatus, digit ratios of males and females did not statistically differ. Thus, the results confirmed our hypothesis that at least in M. alpestris, L. montandoni, and L. vulgaris, females seem to have larger 2D:4D comparing to males, the pattern known from most mammals and opposite to birds, reptiles and anuran amphibians.
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Affiliation(s)
- Mikołaj Kaczmarski
- Department of Zoology, Institute of Zoology, Poznań University of Life Sciences, Poznań, Poland
| | - Anna Maria Kubicka
- Department of Human Evolutionary Biology, Institute of Anthropology, Faculty of Biology, Adam Mickiewicz University in Poznań, Poznań, Poland
| | - Piotr Tryjanowski
- Department of Zoology, Institute of Zoology, Poznań University of Life Sciences, Poznań, Poland
| | - Martin Hromada
- Department of Ecology, Faculty of Humanities and Natural Sciences, Laboratory and Museum of Evolutionary Ecology, University of Prešov, Prešov, Slovakia.,Department of Nature Conservation, Faculty of Biological Sciences, University of Zielona Góra, Zielona Góra, Poland
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20
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Albertine KH, Miller SC. The Anatomical Recordis Alive With Leapin' Lizards and Slitherin' Snakes. Anat Rec (Hoboken) 2014; 297:337-40. [DOI: 10.1002/ar.22873] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2014] [Accepted: 01/04/2014] [Indexed: 12/28/2022]
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