Chromosomes and sex ratio of the collared lemming, Dicrostonyx richardsoni

The chromosomes of 18 laboratory-born Dicrostonyx richardsoni (= D. groenlandicus richardsoni) were examined. Eight females had 2n = 44 and two large metacentric chromosomes, three females and two males had 2n = 43 and three large metacentrics, and two females and three males had 2n = 42 and four large metacentrics. The observed chromosomal polymorphism was explained as a Robertsonian transformation in which metacentrics underwent centric fission to form two telocentrics, or two telocentrics fused to form a metacentric. No chromosomal differences were observed between males and females that had the same number of large metacentrics. The laboratory sex ratio at weaning was 0.38:1 (363 males, 596 females). Observed and expected distributions of proportions of male offspring among dams were significantly different if dams were assumed to produce males with binomial probability 0.5, or with probability 0.38. There was qualitative support for three female types, each producing males with probability 0.50, 0.25, or 0.33, as has been hypothesized for Dicrostonyx torquatus from Asia.

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Variation in Weight, Size, and Sex Ratio of Coccinellid Adults (Coleoptera: Coccinellidae)

The Canadian Entomologist ◽

10.4039/ent98639-6 ◽

1966 ◽

Vol 98 (6) ◽

pp. 639-644 ◽

Cited By ~ 10

Author(s):

B. C. Smith

Keyword(s):

Body Size ◽

Sex Ratio ◽

Water Content ◽

Food Supply ◽

Sexual Differences ◽

Intraspecies Variation ◽

Food Scarcity ◽

Food Requirement ◽

Males And Females

AbstractThe weight and size of coccinellid adults varied with species, sex, and feeding. Intraspecies variation in weight was generally similar in the eight species studied. Females were more variable than males in body size. Females of some species were heavier and larger than males, and species can be classified on a basis of difference in the weight and size of the sexes.An increase in the food supply after a period of food scarcity affected the sex ratio, as the minimum food requirement of females was greater than males. Females increased in weight more rapidly than males after feeding. The availability of food in the field affected the weight and size of some species. Adult water content was influenced by feeding but not by sex or the quantity of food given to the larva.Males were more abundant in species with small sexual differences in weight and size. The degree of difference in weight and size between males and females may be used as a criterion to select species that are best adapted to survive when food is scarce.

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Population parameters of ringed seals (Phoca hispida Schreber, 1775) in the Svalbard area

Canadian Journal of Zoology ◽

10.1139/z87-162 ◽

1987 ◽

Vol 65 (4) ◽

pp. 1021-1027 ◽

Cited By ~ 38

Author(s):

Christian Lydersen ◽

Ian Gjertz

Keyword(s):

Sex Ratio ◽

Ringed Seal ◽

Adult Males ◽

Population Parameters ◽

Phoca Hispida ◽

Age Class ◽

Ringed Seals ◽

Males And Females ◽

The Mean ◽

Sexually Mature

Samples were taken from 284 ringed seals (Phoca hispida) in the Svalbard area during April–July 1981 and March–April 1982. The age of 283 seals was determined by reading annuli in the cementum of the canine teeth. The mean age of the males was 11.3 years, and of the females, 14.9 years. Females were found to be significantly older than males. The mean length of sexually mature ringed seals was 128.9 cm for both sexes. The mean weight of adult males and females was 53.5 and 61.4 kg, respectively. Females were found to be significantly heavier than males. The sex ratio was 47.8% males and 52.2% females. Studies of microscopic sections of testis and epididymis from ringed seal males showed that 63, 75, and 80% of 5-, 6-, and 7-year-old animals, respectively, were sexually mature. The weights of testis and epididymis, diameters of tubuli, and the size of testis all showed a marked increase in the 5-year age-class. Macroscopic sections of ovaries from ringed seal females showed that 20, 60, and 80% of 3-, 4-, and 5-year-old animals, respectively, were sexually mature. The size of the ovaries showed a marked increase in the 5-year age-class. The ovulation rate of ringed seals from Svalbard was calculated to be 0.91.

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A new male-killing parasitism:Spiroplasmabacteria infect the ladybird beetleAnisosticta novemdecimpunctata(Coleoptera: Coccinellidae)

Parasitology ◽

10.1017/s0031182005009789 ◽

2006 ◽

Vol 132 (6) ◽

pp. 757-765 ◽

Cited By ~ 61

Author(s):

M. C. TINSLEY ◽

M. E. N. MAJERUS

Keyword(s):

Phylogenetic Analysis ◽

Sex Ratio ◽

High Efficiency ◽

Sex Ratios ◽

Egg Hatch ◽

Hatch Rate ◽

Male Killing ◽

Offspring Sex ◽

Novel Host ◽

Males And Females

Whilst most animals invest equally in males and females when they reproduce, a variety of vertically transmitted parasites has evolved the ability to distort the offspring sex ratios of their hosts. One such group of parasites are male-killing bacteria. Here we report the discovery of females of the ladybirdAnisosticta novemdecimpunctatathat produced highly female-biased offspring sex ratios associated with a 50% reduction in egg hatch rate. This trait was maternally transmitted with high efficiency, was antibiotic sensitive and was infectious following experimental haemolymph injection. We identified the cause as a male-killingSpiroplasmabacterium and phylogenetic analysis of rDNA revealed that it belongs to theSpiroplasma ixodetisclade in which other sex ratio distorters lie. We tested the potential for interspecific horizontal transfer by injection from an infectedA. novemdecimpunctataline into uninfected individuals of the two-spot ladybirdAdalia bipunctata. In this novel host, the bacterium was able to establish infection, transmit vertically and kill male embryos.

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Studies of the yellow-footed rock-wallaby, Petrogale xanthopus Gray (Marsupialia : Macropodidae). Population studies at Middle Gorge, South Australia

Wildlife Research ◽

10.1071/wr9940473 ◽

1994 ◽

Vol 21 (4) ◽

pp. 473 ◽

Cited By ~ 15

Author(s):

AC Robinson ◽

L Lim ◽

PD Cantry ◽

RB Jenkins ◽

CA MacDonald

Keyword(s):

Sex Ratio ◽

Population Studies ◽

South Australia ◽

Effective Rainfall ◽

Main Study ◽

Exchange System ◽

Two Phase ◽

Flinders Ranges ◽

Significant Bias ◽

Males And Females

A mark-recapture study of Petrogale xanthopus at Middle Gorge in the southern Flinders Ranges revealed that between January 1979 and January 1984 the estimated known-to-be-alive population ranged from 11 to 20. During the main study, individuals living to an estimated age of six years were recorded. Captures of marked animals after completion of the main study revealed both males and females living to at least 10 years old. Births occurred throughout the year but there appeared to be an increase in births following periods of effective rainfall. For the whole study the sex ratio of pouch young did not vary significantly from 1:1. When individuals that gave birth more than once during the study were examined, there was a significant bias towards male young in the later births. It is suggested that this species has a two-phase reproductive strategy with the extra males, produced by older females, sustaining a male-exchange system with nearby colonies.

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Red fox sex ratio and changes in the number in the Krasnoarmeisky District of the Samara Region

Samara Journal of Science ◽

10.17816/snv201872122 ◽

2018 ◽

Vol 7 (2) ◽

pp. 111-115

Author(s):

Olga Aleksandrovna Sklueva ◽

Valeriy Vitalyevich Sklyuev ◽

Rafik Ibragimovich Khakimov

Keyword(s):

Population Dynamics ◽

Sex Ratio ◽

Vulpes Vulpes ◽

Red Fox ◽

Direct Impact ◽

Age Composition ◽

Behavioral Adaptations ◽

Epizootic Process ◽

Males And Females ◽

Homeostatic State

The paper presents some data on the red fox ( Vulpes vulpes , Linnaeus, 1758) sex ratio in the Krasnoarmeysky District of the Samara Region. The results of winter trails traces of mammals show the placement of individual sites of males and females. The authors consider relationship between the population dynamics, sex and age composition and the placement of individual sites. Some aspects of behavioral adaptations and causes of changes in the number of animals in the study area are considered. The influence of a poaching factor on the dynamic indicators of the studied population and the possible danger of the epizootic process is described. A comparative analysis with the previously obtained data on the ratio of males and females in the litter is carried out. The paper indicates possible causes of animals number changes in the study areas. Poaching has a direct impact on the studied population homeostatic state maintaining mechanisms. There is also a forecast of poaching influence on deterioration of epidemiological and epizootic situation in the investigated region. In this paper we give recommendations to minimize possible damage by human activities.

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Analysis of the sex ratio in Bradysia matogrossensis (Diptera, Sciaridae)

Genetics and Molecular Biology ◽

10.1590/s1415-47572000000100018 ◽

2000 ◽

Vol 23 (1) ◽

pp. 97-103 ◽

Cited By ~ 4

Author(s):

Lincoln S. Rocha ◽

André Luiz P. Perondini

Keyword(s):

Sex Ratio ◽

Sex Determination ◽

X Chromosome ◽

Control Mechanism ◽

Sex Ratios ◽

Laboratory Strain ◽

Chromosome Elimination ◽

Common Control ◽

Males And Females ◽

Successive Generations

In sciarid flies, the control of sex determination and of the progeny sex ratio is exercised by the parental females, and is based on differential X-chromosome elimination in the initial stages of embryogenesis. In some species, the females produce unisexual progenies (monogenic females) while in others, the progenies consist of males and females (digenic females). The sex ratio of bisexual progenies is variable, and departs considerably from 1:1. Bradysia matogrossensis shows both monogenic and digenic reproduction. In a recently established laboratory strain of this species, 15% of the females were digenic, 10% produced only females, 13% produced only males, and 62% produced progenies with one predominant sex (33% predominantly of female and 29% predominantly male progenies). These progeny sex ratios were maintained in successive generations. Females from female-skewed progenies yielded female- and male-producing daughters in a 1:1 ratio. In contrast, daughters of females from male-skewed progenies produce bisexual or male-skewed progenies. The X-chromosome of B. matogrossensis shows no inversion or other gross aberration. These results suggest that the control of the progeny sex ratio (or differential X-chromosome elimination) involves more than one locus or, at least, more than one pair of alleles. The data also suggest that, in sciarid flies, monogeny and digeny may share a common control mechanism.

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REPRODUCTIVE ASPECTS OF SCALLOPED PERCHLET, Ambassis nalua (HAMILTON, 1822) IN PABEAN BAY INDRAMAYU, WEST JAVA

Jurnal Ilmu dan Teknologi Kelautan Tropis ◽

10.28930/jitkt.v9i1.17921 ◽

2017 ◽

Vol 9 (1) ◽

pp. 113

Author(s):

Nisha Desfi Arianti ◽

M.F. Rahardjo ◽

Ahmad Zahid

Keyword(s):

Sex Ratio ◽

Sampling Period ◽

Spawning Season ◽

West Java ◽

Fish Samples ◽

Length Range ◽

Males And Females ◽

Mature Fish ◽

First Maturity ◽

Somatic Index

ABSTRACTScalloped perchlet, Ambassis nalua, is one of fishes in Pabean Bay, Indramayu. This research aims to determine the reproductive aspects of Ambassis nalua in Pabean Bay Indramayu including sex ratio, spawning season, first maturity, fecundity and spawning pattern. Fish samples were collected by trap net and trammel net at three sites in Pabean Bay from April to October 2015. A total of 424 of A. nalua were caught, consist of 114 males and 310 females; with total length ranged from 38.04 to 112.63 mm and total weight ranged from 0.37 to 25.44 g. Sex ratio of mature fish was 1:1.9. The mature males and females were found in every month of sampling period. The gonado-somatic index (GSI) ranged from 0.40 to 0.83 and 2.36 to 4.54 for male and female, respectively. The peak of spawning season was found in September. The first maturity (Lm50) for male and female were 79.17 mm and 91.25 mm, respectively. The fecundity varied from 3,451–32,465 eggs. Egg diameter distribution shows that spawning pattern of A. nalua was batch spawner. Keywords: Ambassis nalua, spawning season, sex ratio, reproduction

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The spatial pattern of a Juniperus communis var. depressa population on a continental dune in subarctic Québec, Canada

Canadian Journal of Forest Research ◽

10.1139/x99-018 ◽

1999 ◽

Vol 29 (4) ◽

pp. 446-450 ◽

Cited By ~ 7

Author(s):

Gilles Houle ◽

Mario Duchesne

Keyword(s):

Sex Ratio ◽

Nearest Neighbor ◽

Dispersion Pattern ◽

Neighbor Distance ◽

Juniperus Communis ◽

Biased Sex Ratio ◽

Males And Females ◽

Nearest Neighbor Distance ◽

Population Dispersion ◽

Crown Size

We performed a nearest-neighbor analysis to determine the population dispersion pattern and the association between males and females in a Juniperus communis L. var. depressa Pursh population occupying a continental dune in subarctic Quebec, Canada. The overall dispersion pattern was contagious, and males (or females) were proportionately as likely to have a male as they were to have a female nearest neighbor. Crown size was positively related to nearest-neighbor distance for the male-male comparison only, suggesting a somewhat stronger intrasex competition between males. Nearest-neighbor distance increased with crown size (significantly related to age) suggesting a change in the intensity of aggregation with age possibly related to self-thinning. Higher mortality as a result of stronger male-male competition could explain the female-biased sex ratio and the absence of spatial segregation between sexes. The overall contagious dispersion pattern in the population may be related to the fact that most seed cones fall directly underneath the mother plant. Birds can eat the cones of J. communis and thus disperse seeds. However, these seeds are deposited in clumps, a process that may also explain contagion within the population.

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Panulirus echinatus population in the Brazilian oceanic ecosystem Rocas Atoll

Crustaceana ◽

10.1163/15685403-00003859 ◽

2019 ◽

Vol 92 (2) ◽

pp. 221-232 ◽

Cited By ~ 1

Author(s):

Juliana Gaeta ◽

Raúl Cruz

Keyword(s):

Sex Ratio ◽

Carapace Length ◽

Reproduction Period ◽

Males And Females ◽

The Mean ◽

Oceanic Ecosystem ◽

Abundant Population ◽

Future Information

Abstract In Rocas Atoll (03°51′S 033°48′W) a most abundant population of Panulirus echinatus Smith, 1869 was observed during free dives. Numbers of males and females were almost the same, with an overall sex ratio M : F = 1.1. In addition, males are larger than females, with a mean male carapace length (CL) of 92.6 ± 1.8 mm, while the female mean CL was 72.7 ± 1.0 mm and for both sex combined the mean CL was 83.1 ± 1.4 mm. The percentage of females breeding, i.e., with a spermatophore mass or eggs, was 75.1%. More information is needed to better understand the fluctuation in densities over a year cycle, the reproduction period, and differences in CL between males and females, as well as other aspects of the biology of this species. The present work and future information could help to formulate fisheries policies aimed at protecting P. echinatus stocks.

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Reproductive potential and nesting effects of Osmia rufa (syn. bicornis) female (Hymenoptera: Megachilidae)

Journal of Apicultural Science ◽

10.1515/jas-2016-0003 ◽

2016 ◽

Vol 60 (1) ◽

pp. 75-86 ◽

Cited By ~ 2

Author(s):

Karol Giejdasz ◽

Monika Fliszkiewicz ◽

Andrea Bednárová ◽

Natraj Krishnan

Keyword(s):

Sex Ratio ◽

Reproductive Potential ◽

Female Offspring ◽

Male Offspring ◽

Nesting Behavior ◽

Solitary Bee ◽

Male And Female ◽

Individual Female ◽

The Family ◽

Number Of Cells

Abstract The red mason bee Osmia rufa is a solitary bee belonging to the family Megachilidae, and is prone to nest in aggregations. Each female builds a nest separately in pre-existing cavities such as holes in wood and walls or empty plant stems. This is done by successively setting the cells in a linear series. In this study, we elucidate the nesting behavior and the reproductive potential of a single O. rufa female. The reproductive potential of nesting females was evaluated after the offspring finished development. We observed that an individual female may colonize up to five nest tubes and build 5-34 cells in them (16 on an average). During the nesting time the number of cells decreased with the sequence of nest tubes colonized by one female, which built a maximum of 11 cells in the first occupied nest and 5 cells in the last (fifth nest). Our observations indicated that 40% of nesting females colonized one nest tube as compared to 7% colonizing five nest tubes. Furthermore, in subsequent nest tubes the number of cells with freshly emerged females gradually decreased which was the reverse with males. Thus, the sex ratio (proportion of male and female offspring) may change during the nesting period. The female offspring predominated in the first two nesting tubes, while in the subsequent three tubes male offspring dominated. We also cataloged different causes of reduction in abundance of offspring in O. rufa females such as parasitization or problem associated with moulting.

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