Sexual size dimorphism and corroboration of Rensch’s rule in Chersastus millipedes (Diplopoda: Pachybolidae)
01 Dec 2014-Journal of entomology and zoology studies (AkiNik Publications)-Vol. 2, Iss: 6, pp 264-266
TL;DR: Sexual Size Dimorphism (SSD) was investigated in the millipede genus Chersastus and an allometric coefficient of 0.85 found corroborates Rensch’s rule in this genus.
Abstract: Sexual Size Dimorphism (SSD) was investigated in the millipede genus Chersastus. Mass, length and width were used to compare intraspecific variation in four species. Interspecific variation in volume was calculated in 18 species and an allometric coefficient of 0.85 found, which corroborates Rensch’s rule in this genus.
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TL;DR: In this paper, the authors found evidence of a conflict of interests over control of copulation duration in Centrobolus inscriptus and found that female girth was positively correlated with the second copulation length.
Abstract: Centrobolus inscriptus provides evidence of a conflict of interests over control of copulation duration. Copulation in C. inscriptus lasts for 173 ± 41 min. The re-mating interval between double matings was not impacted by the first copulation duration but was negatively related to the second copulation duration, so that when a female endured a long interval the following copulation was shorter. Female girth was positively correlated to the second copulation duration. The first copulation duration was not significantly dependent on the sexual size dimorphism within copulating pairs, but the second copulation durations was. In these matters of physical combat, the relative sizes of the combatants are thought to be of primary importance.
24 citations
Cites background from "Sexual size dimorphism and corrobor..."
...Materials and Methods The literature was searched for all studies of Centrobolus inscriptus, both independent and dependent of copulation duration [1-18]....
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...Introduction Recent studies on the sexually dimorphic aposematic millipede Centrobolus inscriptus are providing insight into mating behaviour and ecology [1-18]....
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...inscriptus I found equal evidence for syncopulatory male control in prolonged copulations and struggles also under female control [1-18]....
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TL;DR: Preliminary evidence for sexual bimaturism in arthropods is found in the sexually size dimorphic genus Centrobolus intergenerational sexual differences in body size was examined in a population of C. inscriptus.
Abstract: Millipedes haverndeterminate growth and adult body sizes are fixed. In the sexually sizerndimorphic genus Centrobolus intergenerational sexual differences in bodyrnsize was examined in a population of C. inscriptus. Millipedes werernmeasured with minimum measurement error and volumetric body size calculatedrnaccording to l.π.r2. Four male and five female stadiarnwere detected in the population and figured. One evolutionary explanation forrnthe extra female stage is fecundity selection for larger female size. This isrnpreliminary evidence for sexual bimaturism in arthropods.
22 citations
TL;DR: Sexual size dimorphism was calculated in 18 species of the genus Centrobolus and illustrated as a regression as females are larger than males and the approximate relative position of C. inscriptus is shown.
Abstract: Millipedes illustrate reversed sexual size dimorphism (SSD) as females are larger than males. SSD was calculated in 18 species of the genus Centrobolus and illustrated as a regression. The approximate relative position of C. inscriptus is shown. The size of C. inscriptus was 2245mm3: 1841 mm3: (females: males; n=88) and logged (x = 3.351216; y = 3.265054) and plotted. The mean volume ratio for C. inscriptus was 1.219446. Sexual size dimorphism was visible with the naked eye.
20 citations
Cites background or methods from "Sexual size dimorphism and corrobor..."
...Introduction Millipedes illustrate reversed sexual size dimorphism (SSD) and females are larger than males ([1-3])....
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...Millipede SSD was thus calculated in the genus Centrobolus ([1])....
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...The size of C. inscriptus was obtained from Cooper (2014): males 1841mm3 and females 2245mm3 and logged (females/x = 3.351216; males/y = 3.265054) and plotted....
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...72 with the regression of log male volume on log female volume was highly significant with a positive slope less than 1([1])....
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...SSD in forest millipedes has successfully been understood as volumetric measurements using Centrobolus to corrobrate Rensch’s rule ([1])....
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TL;DR: Studies on Centrobolus spp.
Abstract: Studies on Centrobolus spp. were reviewed in which mechanisms of selection, sperm competition and cryptic female choice were studied. Approaches (1) quantify size dimorphism and find the selection pressures operating on the sexes, (2) determine the functional significance of male and female genitalia, (3) understand why there should be a conflict of sexual interests in prolonged copulations, and (4) resolve the mechanisms of sperm competition and cryptic female choice in comparing male mating strategies to female sperm usage were included.
18 citations
Cites background from "Sexual size dimorphism and corrobor..."
...Results 35 studies of the behavioural ecology of millipedes in southern Africa were shown ([8-43])....
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TL;DR: Rensch’s rule predict the negative associations between sexual size dimorphism (SSD) and body sizes for relatively larger females and this prediction was tested for forest and savanna diplopods using a geometric morphometric approach using calculations of length and width to derive shape volume.
Abstract: Rensch’s rule predict the negative associations between sexual size dimorphism (SSD) and body sizes for relatively larger females. This prediction was tested for forest and savanna diplopods using a geometric morphometric approach using calculations of length and width to derive shape volume based on the mathematical formulae for estimated cylindrical worm-like millipede size (l.π.r2) and spherical pill millipede size (4/3.π.r3): (i) Centrobolus (were collected in February 1996, South Africa) SSD was 0.63-2.89 (1.52±0.35; 267) (ii) Sphaerotherium (extracted from literature) SSD was 1.49-5.36 (2.96±1.40; n≥7); (iii) savanna (Calostreptus, Doratogonus, Odontopyge and Spinotarsus were collected in February 1989, Zimbabwe) and forest helminthomorphs (collected in February 1996, South Africa) SSD was 0.88-1.62 (1.26±0.23; 1233). Interspecific variation regressed was SSD (0.63-5.36) on body sizes (n=1273) with no significant negative correlations rejecting Rensch’s rule. Eco-morphological patterns were discussed.
18 citations
Cites background or methods from "Sexual size dimorphism and corrobor..."
...SSD has been studied in the Spirobolida genus Centrobolus with a relationship between the log of male and female volumes for 18 of 39 species suggesting corroboration of Rensch’s rule [30]....
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...The macro-evolutionary pattern is unresolved in Diplopoda [30]....
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References
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TL;DR: From the combination of knowledge and actions, someone can improve their skill and ability and this will lead them to live and work much better.
Abstract: From the combination of knowledge and actions, someone can improve their skill and ability. It will lead them to live and work much better. This is why, the students, workers, or even employers should have reading habit for books. Any book will give certain knowledge to take all benefits. This is what this evolution above the species level tells you. It will add more knowledge of you to life and work better. Try it and prove it.
929 citations
"Sexual size dimorphism and corrobor..." refers background in this paper
...In the present study, SSD in the genus Chersastus is investigated, Rensch’s rule [4] tested, which predicts that SSD is negatively correlated with mean body size....
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...They resemble the majority of invertebrates in that SSD is reversed [3-5]....
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Journal Article•
TL;DR: This work presents an alternative SDI based on the mean size of the larger sex divided by the meanSize dimorphism of the smaller sex with the result arbitrarily defined as positive when females are larger and negative in the converse case.
Abstract: Previous studies of sexual size dimorphism (SSD) use a variety of size dimorphism indices (SDI's) to quantify SSD. We propose that a useful SDI should meet four criteria as follows; 1) it should be properly scaled, 2) it should have high intuitive value, 3) it should produce values with one sign, (positive) when sex A is larger than sex B, and the opposite sign when sex B is larger, and 4) it should produce values that are symmetric around a central value, preferably zero. Many previously published SDI's do not meet any of these criteria, and none meet more than three. We present an alternative SDI based on the mean size of the larger sex divided by the mean size of the smaller sex with the result arbitrarily defined as positive (minus one) when females are larger and negative (plus one) in the converse case. Careful selection of a primary size variable is crucial to meaningful interpretation of sexual size differences.
536 citations
"Sexual size dimorphism and corrobor..." refers methods in this paper
...Exceptions (n=2), where sexes are equal, were submitted to a variance ratio test [8]: in C....
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...SSD was estimated as the mean female volume divided by mean male volume and converted into a SSD index by subtracting 1 [8]....
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TL;DR: General introduction Taxonomy, evolution, and zoogeography Basic anatomy, locomotion and ecomorphology Feeding and digestion Metabolism, excretion, and water balance.
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395 citations
"Sexual size dimorphism and corrobor..." refers background in this paper
...Introduction Millipedes are underrepresented in allometric analyses of Sexual Size Dimorphism (SSD) in invertebrates, although common sexual differences are known in body mass, length, width and leg dimensions of over half the taxa studied [1, 2]....
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TL;DR: It is argued here that there is a strong relationship between polygyny and positive allometry for sexual dimorphism in body size, and this evidence is based on an analysis of the relationship between the scaling of sexualDimorphisms in body weight and the breeding system for 53 primate species, which in most cases coincide with those chosen by Clutton-Brock et al.4 for their study.
Abstract: RENSCH1,2 showed, more than 20 years ago, that sexual dimorphism in body size tends to increase with increasing body size in various arthropod and avian taxa. Recently, the same positive relationship has been suggested for mammals in general3, and primates in particular4. Based on their findings on primates, Clutton-Brock et al.4 discussed several possible functional explanations for this relationship, but considered none of them wholly satisfactory. In particular, they rejected the hypothesis that positive allometry in sexual dimorphism in weight may be the product of an association of size and polygyny; they did not present statistical data to that effect, however. I argue here that, on the contrary, there is a strong relationship between polygyny and positive allometry for sexual dimorphism in body size. The evidence is based on an analysis of the relationship between the scaling of sexual dimorphism in body weight and the breeding system for 53 primate species, which in most cases coincide with those chosen by Clutton-Brock et al.4 for their study. The findings are incorporated into a multifactorial system on the evolution of sexual dimorphism in body size.
144 citations
"Sexual size dimorphism and corrobor..." refers methods in this paper
...Allometry for SSD was based on a general allometric model where male size = α (female size) β [9]....
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60 citations
"Sexual size dimorphism and corrobor..." refers background in this paper
...They resemble the majority of invertebrates in that SSD is reversed [3-5]....
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