scholarly journals Sex change in scallop Patinopecten yessoensis: response to population composition?

PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e5240
Author(s):  
Alla V. Silina
Keyword(s):  
Sex Ratio ◽  
Sex Change ◽  
Older Age ◽  
Age Classes ◽  
Patinopecten Yessoensis ◽  
Sex Structure ◽  
Age Class ◽  
Younger Age ◽  
In The Wild ◽  
Age Frequency Distribution

Sex structure is very labile between populations and specific for each population because it is a result of genetic, ontogenetic and biocenotic influences on the mollusks. In this study, the age frequency distribution, age-sex structure, and sex ratio were assessed in the wild populations of the Yeso scallop Patinopecten yessoensis (Jay) observed at fifteen sites in the northwestern Sea of Japan (=East Sea). The sex ratio varied between the populations from 0.83:1 to 1.52:1 (males/females), with the mean sex ratio being 1.03 ± 0.05:1. Within a population, the proportions of males and females in term of number differed between age classes. Males were more numerous than females in the younger age classes, and females prevailed over males in the older age classes. It was found that in different scallop populations the sex change occurred at different ages. In the populations that predominantly consisted of young (two- to four-year-old) individuals, males prevailed over females in the age class 2 yr.; the equal male/female proportion was found in the age class 3 yr.; and in older age classes, females prevailed over males. Another pattern was observed in the populations that consisted mainly of middle-aged (five- to six-year-old) individuals. Here, the age-sex ratio became equal at an age of 4–6 years. In the old populations (mainly 6–12-year-olds) the equal male/female proportion was observed at an age of 8–10 years. Thus, the age of sex change was not uniform for the scallop populations. It depended on the age structure of the population and, thus, was socially controlled. The greater number of females in the older age classes suggests a protandric sex change.

scholarly journals Studi Kelompok Siamang (Hylobates Syndactylus) Di Repong Damar Pahmungan Pesisir Barat

2015 ◽  
Vol 3 (3) ◽  
pp. 85 ◽  
Author(s):  
Erna Maya Sari ◽  
Sugeng P. Harianto
Keyword(s):  
Sex Ratio ◽  
National Park ◽  
Local Community ◽  
Agroforestry Systems ◽  
Age Classes ◽  
Adult Age ◽  
Age Class ◽  
Hylobates Syndactylus ◽  
The Individual ◽  
Coastal District

Repong Damar in Pahmungan, West Coastal District is a buffer of Bukit Barisan Selatan National Park (TNBBS).  Repong Damar is one example of the success of agroforestry systems managed by local community that is still very traditional.  This area was identified as a component of siamang (Hylobates syndactylus) habitat.  The absence of data and the latest information about the siamang groups in Pekon Pahmungan were reasons of this research.  The purpose of this research was to determine the siamang groups in Repong Damar, used concentrated area methode.  The research was done on April 2015.  The results showed that the existence of siamang group in Repong Damar Pahmungan were 4 individuals/group.  The distribution of age classes in the individual phases of adult siamang were 2 individuals and the individual of adolescent phase were 2 individuals.  The sex ratio in the adult age class phase was 1:1 and at adolescent age class phase was 1:1.  Keywords: siamang, groups, repong damar

scholarly journals Age-Specific Differences in Asian Elephant Defecation, Dung Decay, Detection and Their Implication for Dung Count

2021 ◽  
Author(s):  
Ashokkumar Mohanarangan ◽  
Sakthivel Chinnaiyan ◽  
Sudhakar Kaliyaperumal ◽  
Swaminathan Shanmugavelu ◽  
Ajay A Desai
Keyword(s):  
Decay Rate ◽  
Tamil Nadu ◽  
Probability Of Detection ◽  
Lower Probability ◽  
Wet Season ◽  
Age Classes ◽  
Defecation Rate ◽  
Age Class ◽  
Count Method ◽  
Younger Age

Abstract The various components of the dung count method of population estimation were evaluated such as defecation rate, decay rate, detection probability of dung and age-specific estimates of elephant density based on dung size. The defecation rate of elephants was determined in captive elephants of the Mudumalai elephant camp, Tamil Nadu, India. A total of 14 elephants in the dry season (Dec-Mar 2002) and 17 elephants in the wet season (Jun-Oct 2007) of different age-sex classes were observed for 42 days and 51 days by focal sampling methods and circumference of largest dung pile were measured to determine the growth curve. Total and age-specific elephant density based on dung circumference were estimated using indirect dung count method, 24 transect lines of 2 ~ 4km resulting in a total of 125km distance in Mudumalai Tiger Reserve. The dung decay rate was determined by marking fresh dung piles (n = 1628) every month with an average of 125 ± 77 dung piles/month from Jan 2007 to Feb 2008. The mean defecation rate was 13.51±0.51 (n = 94) per day. The defecation rate varied across age-sex classes and seasons with a lower defecation rate for younger age classes. The dung circumference measurements showed similar growth curves to other Asian and African elephants. Dung size-based age classification significantly overestimates the adult age class, giving an estimate of 82% adults in the population against the true 48.5%. Experimental analysis of detection of dung across perpendicular distance detection of larger and smaller dung size/age classes is equal at a visible distance and declined significantly for younger age/size class at the furthest distance. Decay rate varied significantly according to age classes and across seasons, with lower dung survival rates of younger age classes compared to adults. The minimum required sample size for the dung decay experiment was 250. The age-specific estimate of elephant density based on the indirect dung count method revealed a precise estimate on density, both decay and defecation contribute less than 12% of the variance of the estimate. Age composition based on dung count is highly skewed towards adults, younger age class were low due to lower defecation and faster decay and lower probability of detection in the transect.

scholarly journals Towards a replicator dynamics model of age structured populations

2021 ◽  
Vol 82 (5) ◽  
Author(s):  
K. Argasinski ◽  
M. Broom
Keyword(s):  
Sex Ratio ◽  
Age Structure ◽  
Replicator Dynamics ◽  
Structured Populations ◽  
Reproductive Value ◽  
Leslie Matrix ◽  
Age Classes ◽  
Structured Population Model ◽  
Age Class ◽  
Age Structured

AbstractWe present a new modelling framework combining replicator dynamics, the standard model of frequency dependent selection, with an age-structured population model. The new framework allows for the modelling of populations consisting of competing strategies carried by individuals who change across their life cycle. Firstly the discretization of the McKendrick von Foerster model is derived. We show that the Euler–Lotka equation is satisfied when the new model reaches a steady state (i.e. stable frequencies between the age classes). This discretization consists of unit age classes where the timescale is chosen so that only a fraction of individuals play a single game round. This implies a linear dynamics and individuals not killed during the round are moved to the next age class; linearity means that the system is equivalent to a large Bernadelli–Lewis–Leslie matrix. Then we use the methodology of multipopulation games to derive two, mutually equivalent systems of equations. The first contains equations describing the evolution of the strategy frequencies in the whole population, completed by subsystems of equations describing the evolution of the age structure for each strategy. The second contains equations describing the changes of the general population’s age structure, completed with subsystems of equations describing the selection of the strategies within each age class. We then present the obtained system of replicator dynamics in the form of the mixed ODE-PDE system which is independent of the chosen timescale, and much simpler. The obtained results are illustrated by the example of the sex ratio model which shows that when different mortalities of the sexes are assumed, the sex ratio of 0.5 is obtained but that Fisher’s mechanism, driven by the reproductive value of the different sexes, is not in equilibrium.

scholarly journals Studi Populasi Siamang (Simphalangus syndactylus) DI Hutan Lindung Register 25 Pematang Tanggang Kabupaten Tanggamus

2017 ◽  
Vol 5 (3) ◽  
pp. 66
Author(s):  
Nur Lutfiatuz Zahra ◽  
Gunardi Djoko Winarno
Keyword(s):  
Land Use ◽  
Sex Ratio ◽  
Government Regulation ◽  
Community Forest ◽  
Age Classes ◽  
Adult Age ◽  
Age Class ◽  
Adult Phase ◽  
The Individual ◽  
Individual Adult

Siamang (Simphalangus syndactylus Raffles, 1821) was the primates that protected by government regulation of Republic Indonesia number 7 in 1999. The existence of the siamang was important role in forest as pollinator and seed dispersers. Conversion land has increased into plantations and agriculture so that siamang population became descreased. Protected forest on Register 25 Pematang Tanggang Tanggamus Regency was bordered by community forest, thus vulnerable to land use that siamang population became descreased. The aimed of the research was to find the size of the group, the composition of age, the sexual ratio and the habitat of siamang in protected forest Register 25 Pematang Tanggang. The method used an area concentrated in 3 areal observation. Observations were 30 days effective. The results of this research showed that the Group of siamang found about 3 groups/7 individuals. The distribution of age classes in the individual adult phase of siamang about 6 individuals, adolescent phase about 1 individual and baby phase not found in this group. The sex ratio value in the adult age class phase was 1:1 and at adolescent age class phase was 1:0. According to siamang society does not interfere with human activities so that  not harm for them and their habitat was quite adequate for a population of siamang. Keywords: protected forest, population, siamang

Conservation of the critically endangered Achondrostoma occidentale (Pisces: Cyprinidae): integrating habitat data in restocking programs to improve population recovery

Gaia Scientia ◽  
2016 ◽  
Vol 10 (2) ◽  
pp. 1-9
Author(s):  
D. Mameri ◽  
C. Sousa Santos ◽  
M. F. Magalhães ◽  
J. I. Robalo
Keyword(s):  
Iberian Peninsula ◽  
River Basins ◽  
Fish Abundance ◽  
Critically Endangered ◽  
Ex Situ ◽  
Population Recovery ◽  
Age Classes ◽  
Younger Age ◽  
Risk Of Extinction

Cyprinid fauna endemic to the Iberian Peninsula is currently facing several human-caused threats which enhance their risk of extinction. The populations of the critically endangered Achondrostoma occidentale, occurring only in three small and intermittent Portuguese river basins, have been reinforced with fish bred ex-situ in order to minimize their risk of extinction. This study aimed to describe the restocking actions conducted and to identify and characterize the summer refugia that should become targets for restoration and further restocking. The results evidence population increments and a high representativeness of younger age classes in the restocked populations. The importance of annual monitoring of fish abundance to assess how the species is coping with the stochastic and deterministic stressors that may eventually compromise its survival is highlighted.

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

1987 ◽  
Vol 65 (4) ◽  
pp. 1021-1027 ◽  
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.

scholarly journals Zika: an ongoing threat to women and infants

2018 ◽  
Vol 34 (11) ◽  
Author(s):  
Beatriz Macedo Coimbra dos Santos ◽  
Flavio Codeço Coelho ◽  
Margaret Armstrong ◽  
Valeria Saraceni ◽  
Cristina Lemos
Keyword(s):  
Sexual Transmission ◽  
Risk Groups ◽  
Gender Disparity ◽  
Incidence Rates ◽  
Older Age ◽  
Age Classes ◽  
Sharp Drop ◽  
Men And Women ◽  
Women And Children ◽  
Previous Summer

Recent data from the municipality of Rio de Janeiro, Brazil, shows a sharp drop in the number of reported occurrences of Zika during the summer of 2016/2017, compared to the previous summer. There is still a much higher incidence among women than men, almost certainly due to sexual transmission. An unexpected feature of the new data is that there are proportionally far more cases affecting children under 15 months than older age classes. By comparing incidence rates in 2016/2017 and 2015/2016, we were able to deduce the proportion of reported cases affecting men and women, and verify that gender disparity is still present. Women and children are still risk groups for Zika infection, even during non-epidemic seasons.

scholarly journals Slenderness of trees in black locust stands

2018 ◽  
Vol 79 (2) ◽  
pp. 113-117
Author(s):  
Szymon Bijak ◽  
Katarzyna Orzoł
Keyword(s):  
Standard Deviation ◽  
Black Locust ◽  
Robinia Pseudoacacia ◽  
Habitat Type ◽  
Stand Age ◽  
Age Classes ◽  
Breast Height ◽  
Age Class ◽  
Crown Length ◽  
Research Material

Abstract This paper investigates the slenderness of black locust (Robinia pseudoacacia) trees in relation to the biosocial status of the trees, stand age class, crown parameters and habitat type. The research material was collected on 35 research plots in the Sława Śląska, Sulechów and Głogów forest districts in western Poland and comprises 1058 trees. For each tree, we measured height (h) as well as diameter at breast height (d) and determined its biosocial status (Kraft class), crown length (CL) and relative crown length (rCL). The age class and habitat type were assessed at the plot level. Because the obtained values for slenderness (s=h/d) diverged significantly from the normal distribution, we used Kruskal-Wallis and Mann-Whitney tests to investigate the influence of the above-mentioned parameters on the h/d ratio. Black locust slenderness ranged from 0.31 to 1.95 with an average of 0.91 (standard deviation 0.24). It furthermore differed significantly between Kraft classes (the higher the biosocial status, the lower the slenderness) and age classes (the older the trees, the lower their slenderness). We also found a significant effect of the habitat type (in oligotrophic sites trees formed more slender trunks than in mesotrophic sites) and crown parameters on the h/d ratio (decreasing with increasing crown length and relative crown length). The obtained results suggest that the slenderness of black locust does not differ substantially from native broadleaved trees in Poland.

scholarly journals Aging Reduces EEG Markers of Recognition Despite Intact Performance: Implications for Forensic Memory Detection

2020 ◽  
Author(s):  
Robin Hellerstedt ◽  
Arianna Moccia ◽  
Chloe M. Brunskill ◽  
Howard Bowman ◽  
Zara M. Bergström
Keyword(s):  
Older Adults ◽  
Temporal Variability ◽  
Brain Activity ◽  
Age Groups ◽  
Older Age ◽  
Practical Applications ◽  
Younger Age ◽  
Behavioural Performance ◽  
Older Populations

AbstractERP-based forensic memory detection is based on the logic that guilty suspects will hold incriminating knowledge about crimes they have committed, and therefore should show parietal ERP positivities related to recognition when presented with reminders of their crimes. We predicted that such forensic memory detection might however be inaccurate in older adults, because of changes to recognition-related brain activity that occurs with aging. We measured both ERPs and EEG oscillations associated with episodic old/new recognition and forensic memory detection in 30 younger (age < 30) and 30 older (age > 65) adults. EEG oscillations were included as a complementary measure which is less sensitive to temporal variability and component overlap than ERPs. In line with predictions, recognition-related parietal ERP positivities were significantly reduced in the older compared to younger group in both tasks, despite highly similar behavioural performance. We also observed ageing-related reductions in oscillatory markers of recognition in the forensic memory detection test, while the oscillatory effects associated with episodic recognition were similar across age groups. This pattern of results suggests that while both forensic memory detection and episodic recognition are accompanied by ageing-induced reductions in parietal ERP positivities, these reductions may be caused by non-overlapping mechanisms across the two tasks. Our findings suggest that EEG-based forensic memory detection tests are invalid in older populations, limiting their practical applications.

Observations on Activity Patterns, Population and Den Characteristics of The Water Rat Hydromys chrysogaster Along Badger Creek, Victoria.

1995 ◽  
Vol 18 (1) ◽  
pp. 71
Author(s):  
J.L. Gardner ◽  
M. Serena
Keyword(s):  
Population Density ◽  
Activity Patterns ◽  
Home Ranges ◽  
Adult Males ◽  
Fish Farms ◽  
Age Classes ◽  
Irrigation Channels ◽  
In Captivity ◽  
In The Wild ◽  
Hydromys Chrysogaster

The Water Rat Hydromys chrysogaster is Australia&apos;s largest amphibious rodent, occupying freshwater rivers, lakes, and coastal and estuarine habitats throughout the continent (Watts and Aslin 1981). Little is known of the species&apos; social organisation or use of space in the wild although Harris (1978) suggested that adults might be intrasexually aggressive. The home ranges of all sex and age classes overlap to some extent but home ranges of adults of the same sex appear to overlap less (Harris 1978). Adult males occupy the largest home ranges which overlap those of one or more females. In captivity individuals kept in groups form hierarchies in which only the dominant females usually breed successfully (Olsen 1982). Fighting occurs primarily among males, with the highest incidence of injuries observed at the beginning of the main September-March breeding season (Olsen 1980, 1982). The results of trapping studies indicate that population density may vary considerably, with the greatest numbers of animals typically occupying man-modified habitats such as irrigation channels or fish farms (McNally 1960, Watts and Aslin 1981, Smales 1984). Aggressive behaviour appears to be related to pelage colour (phenotype) and population density; the higher the density the greater the number of injured individuals (Olsen 1980).

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