Sexual differences in development and behaviour of larval Ischnura verticalis (Odonata: Coenagrionidae)

1992 ◽  
Vol 70 (6) ◽  
pp. 1161-1165 ◽  
Author(s):  
Robert L. Baker ◽  
Mark R. L. Forbes ◽  
Heather C. Proctor
Keyword(s):  
Life Cycle ◽  
Sex Ratio ◽  
Larval Development ◽  
Sex Ratios ◽  
Sexual Differences ◽  
Emergence Period ◽  
Southern Ontario ◽  
Male And Female ◽  
Ischnura Verticalis

The emergence period of Ischnura verticalis from a pond in southern Ontario lasted at least 97 days; the sex ratio of emerging larvae was not significantly different from 1:1. A 17-month study on larvae from the same pond indicated that the life cycle was univoltine and that male larvae tended to develop faster than female larvae. Analysis of instar distributions of larval I. verticalis collected from a series of ponds also indicated that males were in more advanced instars than females. In the laboratory, male I. verticalis larvae in the final instar developed faster than female larvae in the final instar but male and female larvae in the penultimate instar developed at approximately the same rate. Male larvae in the antepenultimate instar consistently spent more time moving and crawled farther than female larvae in the antepenultimate instar. Sexual differences in larval development and behaviour could help explain sexual differences in instar distributions and altered sex ratios at emergence.

scholarly journals In-Culture Selection and the Potential Effects of Changing Sex Ratios on the Reproductive Success of Multiannual Delayed Gametophytes of Saccharina latissima and Alaria esculenta

2021 ◽  
Vol 9 (11) ◽  
pp. 1250
Author(s):  
Alexander P. J. Ebbing ◽  
Gregory S. Fivash ◽  
Nuria B. Martin ◽  
Ronald Pierik ◽  
Tjeerd J. Bouma ◽  
...  
Keyword(s):  
Life Cycle ◽  
Reproductive Success ◽  
Sex Ratio ◽  
Female Gametophyte ◽  
Sex Ratios ◽  
Saccharina Latissima ◽  
Male And Female ◽  
Alaria Esculenta

Multiannual delayed gametophyte cultures can stay vegetative for years, while also having the ability to grow. This study aims to investigate whether male and female multiannual delayed gametophyte strains of the species Saccharina latissima and Alaria esculenta grow at different rates in culture. We furthermore assessed how changing sex ratios can affect the reproductive yields of these cultures. The results indicate that the reproductive yield of cultures declines with decreasing male:female ratios, a correlation that becomes especially apparent at higher culture densities for both species. Female gametophyte densities in particular affected the observed reproductive yield of the cultures, with S. latissima cultures showing a clear reproductive optimum (sporophytes·mL−1) at 0.013 mg·mL−1 DW female gametophyte biomass, while the reproductive success of A. esculenta peaked at a density of 0.025 mg·mL−1 DW of female gametophyte biomass, after which the reproductive yield started to decline in both species. The results show that the sex ratio of a gametophyte culture is an important biotic life cycle control, with higher amounts of female gametophyte biomass halting gametophyte reproduction. Understanding how these changing sex ratios in gametophyte cultures affect reproduction is especially important in the aquaculture of kelp, where reliable preforming cultures are key to long-term success.

Sex ratios of Sitodiplosis mosellana (Diptera: Cecidomyiidae): implications for pest management in wheat (Poaceae)

2004 ◽  
Vol 94 (6) ◽  
pp. 569-575 ◽  
Author(s):  
M.A.H. Smith ◽  
I.L. Wise ◽  
R.J. Lamb
Keyword(s):  
Life Cycle ◽  
Sex Ratio ◽  
Sex Ratios ◽  
Adult Emergence ◽  
Differential Mortality ◽  
Sitodiplosis Mosellana ◽  
Single Sex ◽  
Crop Resistance ◽  
Wheat Midge ◽  
Population Average

AbstractSex ratios of populations of the wheat midge Sitodiplosis mosellana Géhin, developing on wheat Triticum aestivum L., were determined at reproduction, adult emergence, and dispersal. The patterns of sex ratio through the life cycle of S. mosellana result from: (i) a genetic mechanism that causes all or nearly all of the progeny of individual females to be a single sex, with an overall sex ratio that is slightly biased at 54–57% females; (ii) a differential mortality during diapause that increases the sex ratio to 60–65% females; (iii) mating which occurs near the emergence site followed by female dispersal which causes the post-dispersal sex ratio to rise to nearly 100% females; and (iv) oviposition which spreads eggs among different plants and assures that the next generation has a local sex ratio close to the population average. These changes in sex ratio through the life cycle have implications for using crop resistance or pheromones to manage S. mosellana, because mating takes place quickly near emergence sites, and because mated females but not males disperse from emergence sites to oviposition sites. Crop refuges used to protect resistance genes against the evolution of virulence by S. mosellana must be interspersed to prevent assortative mating that would occur in separate blocks of resistant and susceptible plants. Monitoring or mating disruption using a pheromone would be ineffective when wheat is grown in rotation with a non-host crop.

scholarly journals Feeding Propensity and Cannibalism of Micraspis Discolor (Fab.) to Different Prey Species (Aphis craccivora and Nilaparbata lugens) under Laboratory

2016 ◽  
Vol 9 (1) ◽  
pp. 81-85 ◽  
Author(s):  
MZ Islam ◽  
SA Labani ◽  
AB Khan
Keyword(s):  
Life Cycle ◽  
Sex Ratio ◽  
Prey Species ◽  
Larval Period ◽  
Oviposition Period ◽  
Male And Female ◽  
Average Longevity ◽  
Brown Plant Hopper ◽  
Micraspis Discolor ◽  
Total Life

Feeding propensity and cannibalism of Micraspis discolor (Fab.) to different prey species (bean aphids and brown plant hopper ) was studied in the laboratory of the Department of Entomology, Bangladesh Agricultural University, Mymensingh, during January, 2007 to April, 2007. It was found that the highest pre-oviposition period was to 5.6±0.54 days when BPH were used and this period was lowest, 4.6±0.54 days using bean aphid. The oviposition period was maximum 40.20±1.78 days using bean aphid and minimum 29.00± 2.00 days were found using BPH. Maximum number of eggs 216.00±16.58 was laid when fed on bean aphid. The hatching percent was highest 88.71% using bean aphid and hatching percent was lowest 85.34% when fed on BPH. Incubation period varied from 2.40±0.54 to 3.80±0.44 days using different foods. However, the larvae passed through four larval instars and highest larval period was 10.00 ± 0.70 when BPH were used as food and lowest was 8.40 days feeding on bean aphid. Pupal period was 3.00±0.00 & 3.80±0.44 days when bean aphid & BPH were supplied as food. The average longevity of female was 38.60±3.78 and 31.40±2.96 days and that of male was 32.00±2.91 & 26.00±0.91 days when feeding on bean aphid and BPH respectively. It was significant at 1% level. The sex ratio of male and female was found (0.78:1.00) using different foods and these were not significant at 1% level. By this experiment, It was observed that feeding propensity of Micraspis discolor to different prey species during the total life cycle was as follows: bean aphid > BPH. It was also found that M. discolor had cannibalistic behavior and this was significant at 1% level.J. Environ. Sci. & Natural Resources, 9(1): 81-85 2016

Mechanism of Male Choice: Sex Ratios

2021 ◽  
pp. 109-118
Author(s):  
Ingo Schlupp
Keyword(s):  
Sex Ratio ◽  
Population Biology ◽  
Sex Ratios ◽  
Binary Choice ◽  
Mate Quality ◽  
Male And Female ◽  
Female Quality ◽  
Choice Tests

In this short chapter I want to discuss the role of sex ratios in choosiness. So far, we have mostly reviewed intrinsic reasons for male choosiness to be expressed such as male investment and female quality; however, sex ratios may also be important drivers of choosiness. Sex ratios are important in population biology and influence the evolution and structure of mating systems. Most important for the purpose of this book is that they can change quickly in time and space. Male and female choice are sensitive to such changes and can lead to situations where females are choosy when they are rare in a population but change to courtship and competition when males are rare. There are not many examples of this process, but there are likely some that have been overlooked. Interestingly, the majority of data on preferences are collected using binary choice tests, which almost always represent a 2:1 sex ratio. Furthermore, sex ratios do not take into account differences in mate quality, as all adult individuals are classified as either male or female without making any further distinction.

scholarly journals Relative growth and population dynamics of Macrobrachium iheringi (Decapoda, Palaemonidae)

2019 ◽  
Vol 59 ◽  
pp. e20195908 ◽  
Author(s):  
Caio Dos Santos Nogueira ◽  
Júlia Fernandes Perroca ◽  
Emerson Luiz Piantkoski ◽  
Rogerio Caetano da Costa ◽  
Fabiano Gazzi Taddei ◽  
...  
Keyword(s):  
Population Dynamics ◽  
Life Cycle ◽  
Sex Ratio ◽  
Larval Development ◽  
Sexual Maturity ◽  
Abiotic Factors ◽  
Relative Growth ◽  
Males And Females ◽  
Life Cycle Pattern ◽  
Precipitation And Temperature

During the ontogenetic development of crustaceans, the relative growth of some structures may change, especially during the transition from juvenile to adult. This study describes the relative growth of body structures of Macrobrachium iheringi, and provides information on its population dynamics, such as structure, fecundity, and morphological sexual maturity. The sampling of M. iheringi was carried out in “Ribeirão da Hortelã”, in Botucatu (SP, Brazil). The length of the carapace (CL), abdomen (AL), and ischium (IL), merus (ML), carpus (CrL), propodus (PpL), and dactyl (DcL) of the second right pereopod were measured. In addition, the width of the second abdominal pleura (PW) and propodus height (PpH) were included in analyses. The relationships that best demonstrated the changes in the allometric coefficient were CL vs PpL in males and females. The CL, in which males and females reach morphological sexual maturity, was estimated as 13.3 mm and 11.1 mm, respectively. The sex-ratio differed from the expected 1:1 and was skewed towards females. Precipitation and temperature influenced the abundance of different demographic classes. Macrobrachium iheringi has few but large eggs, which is expected since this species has an abbreviated larval development. Based on these results, we conclude that the propodus are good indicators of the size at onset of morphological sexual maturity. In addition, important information was obtained on the biology of M. iheringi, including its life cycle pattern, reproduction and influence of abiotic factors.

Male-biased adult sex ratios in a red squirrel population

1987 ◽  
Vol 65 (5) ◽  
pp. 1284-1286 ◽  
Author(s):  
T. Andrew Hurly
Keyword(s):  
Sex Ratio ◽  
Habitat Use ◽  
Sex Ratios ◽  
Sexual Differences ◽  
Differential Mortality ◽  
Red Squirrel ◽  
Red Squirrels ◽  
Male Mortality ◽  
Adult Sex Ratio ◽  
Sampling Biases

A 3-year study of a red squirrel population revealed that the adult sex ratio was biased towards males. There is no evidence that the skewed sex ratio was prejudiced by sampling biases due to sexual differences in mobility, observability, trappability, or habitat use. The tertiary juvenile sex ratio was even and therefore not the cause of the biased adult sex ratio. The data suggest that the skewed sex ratio may be the result of differential mortality. This is consistent with other reports of higher female than male mortality in red squirrels.

Observations on the larval development of Sacculina carcini (Crustacea: Cirripedia: Rhizocephala)

1988 ◽  
Vol 68 (3) ◽  
pp. 377-390 ◽  
Author(s):  
Graham Walker
Keyword(s):  
Larval Development ◽  
Seasonal Changes ◽  
Carapace Length ◽  
Sex Ratios ◽  
Stage Iv ◽  
Male And Female ◽  
Barnacle Species ◽  
Sacculina Carcini ◽  
Volume Measurements ◽  
Length Data

The larval development of the parasitic barnacle, Sacculina carcini, has been closely followed. Size and volume measurements have been made for the four naupliar stages and cyprids of both male and female broods. Volume increases between naupliar stages are minimal (x 1.03–1.09) and in line with other barnacle species with lecithotrophic larvae. However, the large volume reduction between stage IV and cyprid for S. carcini, which is more acute for the female larvae, is a unique characteristic. The reduced setation formulae of the larval appendages of S. carcini and another rhizocephalan are compared to those of larvae, both lecithotrophic and planktotrophic, of a range of barnacles. Sex ratios and carapace length data for 184 S. carcini cypris populations are presented which reinforce the seasonal changes in sex ratios.

Experimental observations on the sex ratio of adult Schistosoma mansoni, with comments on the natural male bias

Parasitology ◽  
2000 ◽  
Vol 121 (4) ◽  
pp. 379-383 ◽  
Author(s):  
J. BOISSIER ◽  
H. MONÉ
Keyword(s):  
Sex Ratio ◽  
Schistosoma Mansoni ◽  
Sex Ratios ◽  
Vertebrate Host ◽  
Natural Conditions ◽  
Male And Female ◽  
Male Bias ◽  
Biased Sex Ratio ◽  
And Bisexual

The sex ratio of adult worms has been observed biased towards males in Schistosoma mansoni under natural conditions. The origin of this bias is unknown. This paper determines whether males are more infective than females under controlled experimental bisexual conditions, and hence if the sex ratio is male-biased as a consequence of this. The male and female cercarial infectivities in uni- and bisexual vertebrate host infections using a range of controlled cercarial sex ratios were studied. The results showed that, in experimental unisexual infections, male cercariae were more infective than females, and that in experimental bisexual infections, male cercarial infectivity was similar to that of female, irrespective of cercarial sex ratio. Furthermore, cumulative male and female cercarial infectivity was maximal when sex ratio was equilibrated. The unbiased sex ratios obtained in our experimental bisexual infections are discussed in terms of behavioural and/or biochemical male–female interaction. Alternative explanations of the natural biased sex ratio are proposed.

Discord between field and laboratory sex ratios of the water mite Neumania papillator Marshall (Acari: Unionicolidae)

1992 ◽  
Vol 70 (12) ◽  
pp. 2483-2486 ◽  
Author(s):  
Heather C. Proctor
Keyword(s):  
Sex Ratio ◽  
Sex Determination ◽  
Sex Ratios ◽  
Differential Susceptibility ◽  
Environmental Sex Determination ◽  
Water Mite ◽  
Southern Ontario ◽  
Field Samples ◽  
Biased Distribution

I regularly sampled a pond in southern Ontario throughout the ice-free season in 1990 to determine adult phenology of the water mite Neumania papillator. Adult mites were present from 23 April to 9 November. Sex ratios in field samples were strongly male biased from 25 June to 2 November; however, mites raised from deutonymphs (juveniles) in the laboratory showed strongly female-biased sex ratios. Experiments indicated that differences in field and laboratory sex ratios could not be explained by differential susceptibility of the sexes to predation or starvation. Sex-biased distribution or trappability, or environmental sex determination may explain sex-ratio differences.

scholarly journals Sex Ratio Bias at Hatching and Fledging in the Roseate Tern

The Condor ◽  
2001 ◽  
Vol 103 (2) ◽  
pp. 385-389 ◽  
Author(s):  
Patricia Szczys ◽  
Ian C. T. Nisbet ◽  
Jeremy J. Hatch ◽  
Richard V. Kesseli
Keyword(s):  
Molecular Markers ◽  
Life Cycle ◽  
Sex Ratio ◽  
Sex Ratios ◽  
Ratio Bias ◽  
Sex Ratio Bias ◽  
Sterna Dougallii ◽  
Roseate Tern ◽  
Existing Data

Abstract Several hypotheses have been proposed to explain facultative manipulation of sex ratios in birds, but existing data are inconsistent within and among species, and do not clearly support any one of the hypotheses. The sex ratio among breeding Roseate Terns (Sterna dougallii) at Bird Island, Massachusetts is female-biased (56%). We sought to determine at what stage of the life cycle this sex ratio bias is established. We monitored 461 eggs from 252 nests and, using molecular markers, we sexed 342 chicks at hatching and followed them to a stage when survival (or non-survival) to fledging could be inferred. We found that the sex ratio at hatching (and, by inference, at fertilization) was biased toward females (55%). This bias was significant in chicks from first-laid eggs (58%) but not second-laid eggs (48%). We also found that the overall bias increased (to 56.6%) during the chick stage through differential loss of male chicks.

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