Sex ratio and sexual dimorphism in the dioecious Borderea pyrenaica (Dioscoreaceae)

The semi terrestrial crabs are important elements of the fauna of coastal regions. The aim of this study was to analyze the population structure of Armases angustipes (Dana, 1852) at estuaries of the Ariquindá River, considered a non impacted area, and Mamucabas River, considered a few impacted area, on the south coast of state of Pernambuco, Brazil. The species occurred in all months of the year. The number of individuals per month varied, being higher in the months of transition between the seasons. This is probably due to significant seasonal variations of air and burrow temperature and burrow salinity. There was no sexual dimorphism in size of A. angustipes in the mangrove of Ariquindá River, but males were larger than females in the mangrove of Mamucabas River. In both estuaries, the sex ratio did not differ from Mendelian proportion, but showed a deviation for females. The analysis of temporal variation in sex ratio showed significant differences in some months of the year. These variations are due to cyclical events that act distinctly on each sex. In both estuaries, size classes of carapace width were equally represented by both sexes. The ovigerous females of A. angustipes occurred only in some months of the year, especially in summer, in both estuaries. Probably the high phytoplankton productivity observed in summer favors the reproductive activity, since these algae serve as food for the larvae. Specimens of the population of Rio Ariquindá are largest and wider than those of Mamucabas River. This fact, associated with the low abundance of crabs and the lower frequency of ovigerous females observed in Mamucabas River, is an indication that this population may be influenced by the environmental impacts that this estuary has received.

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Sexual dimorphism in a top predator ( Notophthalmus viridescens ) drives aquatic prey community assembly

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2018.1717 ◽

2018 ◽

Vol 285 (1890) ◽

pp. 20181717 ◽

Cited By ~ 7

Author(s):

Denon Start ◽

Stephen De Lisle

Keyword(s):

Sexual Dimorphism ◽

Sex Ratio ◽

Intraspecific Variation ◽

Structure And Function ◽

Sexually Dimorphic ◽

Ecological Communities ◽

Top Predator ◽

Aquatic Mesocosms ◽

And Function ◽

The Impact

Intraspecific variation can have important consequences for the structure and function of ecological communities, and serves to link community ecology to evolutionary processes. Differences between the sexes are an overwhelmingly common form of intraspecific variation, but its community-level consequences have never been experimentally investigated. Here, we manipulate the sex ratio of a sexually dimorphic predacious newt in aquatic mesocosms, then track their impact on prey communities. Female and male newts preferentially forage in the benthic and pelagic zones, respectively, causing corresponding reductions in prey abundances in those habitats. Sex ratio differences also explained a large proportion (33%) of differences in the composition of entire pond communities. Ultimately, we demonstrate the impact of known patterns of sexual dimorphism in a predator on its prey, uncovering overlooked links between evolutionary adaptation and the structure of contemporary communities. Given the extreme prevalence of sexual dimorphism, we argue that the independent evolution of the sexes will often have important consequences for ecological communities.

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Sex ratio and sexual selection in wormshrimps (Crustacea, Amphipoda, Ingolfiellidea)

Contributions to Zoology ◽

10.1163/18759866-0750304007 ◽

2006 ◽

Vol 75 (03-04) ◽

pp. 189-194 ◽

Cited By ~ 8

Author(s):

Ronald Vonk ◽

Vincent Nijman

Keyword(s):

Sexual Selection ◽

Sexual Dimorphism ◽

Sex Ratio ◽

Habitat Use ◽

Individual Species ◽

Small Populations ◽

Secondary Sexual Characters ◽

Elusive Species ◽

The Individual ◽

Secondary Sexual

Small populations of several species of the groundwater dwelling amphipod genus Ingolfiella are found in caves, wells, seabottoms, beaches and riverbed interstitial habitats. To gain insight in the socio-ecology of these elusive species, we used data from collected specimens to explore the relationships between sexratios, display of secondary sexual characters and other morphological features, and habitat use. We extracted data on the sex ratios and the presence-absence of secondary sexual characters of 13 species from the literature and through examination of museum material. We found a clearly skewed sex ratio with a preponderance of females, both in the individual species as in the genus as a whole. However, sex ratio and the display of secondary sexual characters were not correlated, nor did these characters correlate with the amount of sexual dimorphism. It remains unknown why so many ingolfiellids have evolved these costly features.

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Sex Ratio and Sexual Dimorphism of Three Lice Species with Contrasting Prevalence Parasitizing the House Sparrow

Journal of Parasitology ◽

10.1645/ge-3157.1 ◽

2013 ◽

Vol 99 (1) ◽

pp. 24-30 ◽

Cited By ~ 13

Author(s):

Péter László Pap ◽

Costică Adam ◽

Csongor István Vágási ◽

Zoltán Benkő ◽

Orsolya Vincze

Keyword(s):

Sexual Dimorphism ◽

Sex Ratio ◽

House Sparrow

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Sexual dimorphism of the major chela and sex ratio as indicators of the mating system in the estuarine snapping shrimp Alpheus colombiensis Wicksten, 1988 (Decapoda: Caridea: Alpheidae)

Journal of Crustacean Biology ◽

10.1093/jcbiol/ruaa069 ◽

2020 ◽

Vol 40 (6) ◽

pp. 649-656

Author(s):

Juan C Azofeifa-Solano ◽

Jeffrey A Sibaja-Cordero ◽

Ingo S Wehrtmann

Keyword(s):

Sexual Selection ◽

Sexual Dimorphism ◽

Sex Ratio ◽

Mating System ◽

Mate Guarding ◽

Female Size ◽

Monogamous Species ◽

Low Degree ◽

Adult Sex Ratio ◽

Snapping Shrimps

Abstract The sexual selection over traits that favor access to mating partners could promote the emergence of sexual dimorphism when the pressure is different between sexes. Monogamous species are considered to have a low degree of sexual dimorphism. The highly diverse snapping shrimps are usually regarded as monogamous, but the mating system has been studied only in few species. We aimed to provide insights into the mating system and sexual dimorphism of Alpheus colombiensisWicksten, 1988. The adult sex ratio was female biased, and solitary ovigerous females were found, suggesting a temporary mate guarding type of mating system. Our results also revealed sexual dimorphism on the snapping claw, which is larger in males than in females. The male’s snapping claw is probably under sexual selection, which can be mediated by male-male competition or female choice. We also estimated the A. colombiensis female size at maturity at 5.2 ± 0.76 mm. Our results contradict the common idea that snapping shrimps are monogamous species, and support that A. colombiensis probably have a temporary mate guarding (e.g., males can sexually interact with more than one female, in opposition to sexual monogamy). This study also sustains the growing evidence that alpheid shrimps display snapping claw sexual dimorphism.

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SEXUAL DIMORPHISM AND SEX RATIO IN THE YELLOWSHOULDERED WIDOWBIRD EUPLECTES MACROURUS SOROR

Ostrich ◽

10.1080/00306525.1994.9632691 ◽

1994 ◽

Vol 65 (3-4) ◽

pp. 297-301 ◽

Cited By ~ 2

Author(s):

Udo M. Savalli

Keyword(s):

Sexual Dimorphism ◽

Sex Ratio

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The Tasmanian Whitebait, Lovettia seali (Johnston), and the Whitebait Fishery

Marine and Freshwater Research ◽

10.1071/mf9500155 ◽

1950 ◽

Vol 1 (2) ◽

pp. 155 ◽

Cited By ~ 21

Author(s):

M Blackburn

Keyword(s):

Growth Rate ◽

Sexual Dimorphism ◽

Sex Ratio ◽

Incubation Period ◽

Standard Length ◽

Southern Population ◽

History Of ◽

One Year

The biology of the aplochitonid Lovettia seali (Johnston), which comprises over 95 per cent. of the Tasmanian whitebait catch, has been studied. Over 78,000 fish from 95 samples were sexed and measured, and 1,200 were classified as to maturity, pigmentation stages, and the presence or absence of food in the stomach. Vertebra counts were made for 1,200 specimens, and there were other observations upon smaller amounts of material. There are marked resemblances to other salmonoids in most points of the biology. There is conspicuous sexual dimorphism. The fish are anadromous and at their ascent are all mature or almost so, and all of the same age (one year by otoliths). After spawning begins there is progressive discoloration and emaciation, followed almost invariably by death. About 0.001 per cent. of the stock consists of two-year fish. The eggs are large compared with the size of fish (extremes of standard length in the adult stock are 33 and 70 mm.) and the incubation period is about three weeks. The larvae drift downstream to the sea. Sex ratio is highly variable, but generally the males greatly outnumber the females. A northern and a southern population can be distinguished, the differences being in growth rate and pigmentation. Each population supports a separate fishery, which operates on the ascending shoals. The history of the fisheries is outlined. The southern fishery has never been important because the fish available at the principal fishing locality are excessively pigmented. More suitable fish could be taken by operating further downstream, where the fish are typically at an earlier stage of maturity. The northern fishery has been vigorously prosecuted and overfishing was probably the cause of the decline in abundance of stock in 1947 and 1948. If there was overfishing, it operated purely by excessive removal of reproducers. The order of the optimum catch is empirically identified and a programme for the management of the stock, aiming at its rehabilitation, is recommended.

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