scholarly journals MAINTENANCE OF A "PARASITIC" B CHROMOSOME IN THE GRASSHOPPER MELANOPLUS FEMUR-RUBRUM

Genetics ◽  
1977 ◽  
Vol 87 (3) ◽  
pp. 499-512
Author(s):  
Uzi Nur
Keyword(s):  
New York ◽  
Transmission Rate ◽  
B Chromosome ◽  
B Chromosomes ◽  
High Rate ◽  
Adult Males ◽  
High Transmission ◽  
In The Wild ◽  
Males And Females ◽  
The Mean

ABSTRACT About 10-15% of the males and females of the grasshopper Melanoplus femur-rubrum collected near Rochester, New York, possessed a supernumerary B chromosome. The frequency of the B chromosome remained fairly constant during the years 1971-1974. The B chromosome was shown previously to be transmitted at a rate of about 0.5 and 0.8 by 1B males and females, respectively. This study was designed to determine the forces preventing the B chromosome from increasing in frequency due to the high rate of transmission by the females. Eighty inseminated females collected in the wild were analyzed cytologically together with their embryos (10-20 per female). Ten of the 80 females had a B chromosome, and they transmitted it at a rate of about 0.75. Among the 983 embryos analyzed, 0.141 had one B, 0.007 had two, and the mean number of B chromosomes per embryo was 0.155. The frequency of the B chromosome in the sperm pool (0.061) was consistent with a 0.5 rate of transmission. Individuals with two B chromosomes apparently have low viability, because about six were expected, but none was found among 851 adult males and females examined. The data suggest that the viability of the 1B individuals was only about 0.86 that of the OB individuals. There was no evidence that the B chromosome increased the fecundity of either the 1B males or females. It was concluded, therefore, that the B chromosome reduced the fitness of all the individuals carrying it and was thus "parasitic," and that it was maintained in the population only because of its high transmission rate. The maintenance of other B chromosomes with high transmission rates is reviewed.

scholarly journals High Rate of SARS-CoV-2 Transmission due to Choir Practice in France at the Beginning of the COVID-19 Pandemic

2020 ◽  
Author(s):  
Nathalie CHARLOTTE
Keyword(s):  
Attack Rate ◽  
Transmission Rate ◽  
High Rate ◽  
Individual Risk ◽  
High Transmission ◽  
The Mean ◽  
The Individual ◽  
Practice Methods ◽  
Index Cases ◽  
Close Contacts

Background: There has been little focus on the individual risk of acquiring COVID-19 related to choir practice. Methods: We report the case of a high transmission rate of SARS-CoV-2 linked to an indoor choir rehearsal in France in March 2020 at the beginning of the COVID-19 pandemic. Results: A total of 27 participants, including 25 male singers, a conductor and an accompanist attended a choir practice on March 12, 2020. The practice was indoor and took place in a non-ventilated space of 45 m2. No choir member reported having been symptomatic for COVID-19 between March 2 and March 12.The mean age of the participants was 66.9 (range 35-86) years. 70% of the participants (19 of 27) were diagnosed with COVID-19 from 1 to 12 days after the rehearsal with a median of 5.1 days. 36% of the cases needed a hospitalization (7/19), and 21% (4/19) were admitted to an ICU. The index cases were possibly multiple. Discussion: The choir practice was planned in March 2020 at a period when the number of new cases of COVID-19 began to grow exponentially in France because SARS-CoV-2 was actively circulating. The secondary attack rate (70%) was much higher than it is described within households (10-20%) and among close contacts made outside households (0-5%). Singing might have contributed to enhance SARS-CoV-2 person-to-person transmission through emission of droplets and aerosolization in a closed non ventilated space with a relative high number of people including multiple pre-symptomatic suspected index cases. Conclusion: Indoor choir practice should be suspended during SARS-CoV-2 outbreaks. Further studies are necessary to test the spread of the virus by the act of singing. As the benefits of the barrier measures and social distancing are known to be effective in terms of a reduction in the incidence of the COVID-19, experts recommendations concerning the resuming of choir practice are necessary.

Distribution and reproductive biology of the blackchin guitarfish, Rhinobatos cemiculus (Pisces: Rhinobatidae), in Tunisian waters (central Mediterranean)

1994 ◽  
Vol 45 (4) ◽  
pp. 551 ◽  
Author(s):  
C Capape ◽  
J Zaouali
Keyword(s):  
Reproductive Biology ◽  
Gravid Female ◽  
Total Sample ◽  
High Rate ◽  
Adult Males ◽  
Central Mediterranean ◽  
Chemical Balance ◽  
Adult Females ◽  
Males And Females ◽  
The Mean

Aspects of the reproductive biology of Rhinobatos cemiculus are described from specimens collected in Tunisian waters. Sizes at first sexual maturity of males and females are 1000 mm and 1100 mm total length (TL), respectively. Adult females are generally larger than adult males, the maximum TL for males and females being 1920 mm and 2300 mm, respectively. The smallest gravid female observed was 1220 mm TL. R. cemiculus is an aplacental viviparous species, with each female having two ovaries and two uteri, both functional. Ripe oocytes in the ovaries, ova, embryos and fully developed fetuses in the uteri are symmetrically distributed. The gestation period could last for a maximum of eight months. Vitellogenesis proceeds in parallel with gestation, and at the time of parturition a crop of ripe oocytes is ready to be ovulated. Ovulation and parturition occur during winter and summer, respectively. There is probably one litter per year. The mean TL and mean weight of fully developed fetuses are 39.6 mm and 115.1 g, respectively. A computed chemical balance of development, based on the mean dry weights of fully developed fetuses and ripe oocytes, is 1.01. This low value is due to the fact that R. cemiculus is purely a lecithotrophic species. Fecundity ranges from 5 to 12 young per litter. Ovarian fecundity and uterine fecundity are slightly correlated with the size of females. Females are more numerous than males in the total sample, as well as in utero and at the juvenile stage; however, this is not the case for subadults and adults. This phenomenon is probably due to segregation of the sexes at different depths during certain stages of the reproductive cycle rather than to a high rate of mortality among subadult and adult females.

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 Transmission rate variation among three B chromosome variants in the fish Prochilodus lineatus (Characiformes, Prochilodontidae)

2013 ◽  
Vol 85 (4) ◽  
pp. 1371-1377 ◽  
Author(s):  
MANOLO PENITENTE ◽  
TATIANA A. VOLTOLIN ◽  
JOSE A. SENHORINI ◽  
JEHUD BORTOLOZZI ◽  
FAUSTO FORESTI ◽  
...  
Keyword(s):  
Transmission Rate ◽  
B Chromosome ◽  
B Chromosomes ◽  
Rate Variation ◽  
Parental Line ◽  
Prochilodus Lineatus ◽  
Extinction Process ◽  
Cytogenetic Studies ◽  
Acrocentric Chromosomes ◽  
Interesting System

Cytogenetic studies were developed in Prochilodus lineatus (Valenciennes 1836), describing an interesting system of small supernumerary chromosomes. The purpose of this work is to study the frequency and morphology of B chromosomes in individuals from the parental line and the inheritance patterns of these elements in individuals obtained from controlled crosses in the species P. lineatus. The transmission rate of B chromosomes revealed a kB=0.388 for the acrocentric type, a kB=0.507 for the metacentric type and a kB=0.526 for the submetacentric type. The obtained results raise hypothesis that B-acrocentric chromosomes are involved in an extinction process in this species, while the metacentric and submetacentric supernumerary elements comprises a neutral mechanism and follows a Mendelian transmission rate.

Sex Ratios and Lengths of Adult Sea Lampreys (Petromyzon marinus) from a Lake Ontario Tributary

1974 ◽  
Vol 31 (1) ◽  
pp. 122-124 ◽  
Author(s):  
I. C. Potter ◽  
F. W. H. Beamish ◽  
B. G. H. Johnson
Keyword(s):  
Narrow Range ◽  
Sex Ratios ◽  
Petromyzon Marinus ◽  
Lake Ontario ◽  
Sea Lamprey ◽  
Adult Males ◽  
Sea Lampreys ◽  
Males And Females ◽  
The Mean ◽  
Humber River

The mean lengths of adult males and females of the sea lamprey (Petromyzon marinus) migrating into the Humber River from Lake Ontario in each of the years 1968–1972 varied little, and were similar to those found by other workers in recently established populations in the upper lakes. In contrast, the ratio of males to females, which lay within the narrow range of 1:1 to 1.26:1, was similar to those reported for long-established populations.

The dynamics of B chromosomes in populations of the Australian plague locust, Chortoicetes terminifera (Walker)

1984 ◽  
Vol 26 (2) ◽  
pp. 194-208 ◽  
Author(s):  
P. C. Gregg ◽  
G. C. Webb ◽  
M. A. Adena
Keyword(s):  
New South ◽  
Female Parent ◽  
B Chromosome ◽  
Average Frequency ◽  
B Chromosomes ◽  
Banding Patterns ◽  
South Wales ◽  
Random Fashion ◽  
Accumulation Mechanism ◽  
Males And Females

The B chromosomes of Chortoicetes terminifera possess an accumulation mechanism. B chromosomes were transmitted at a rate of 0.766 in one B(♂) × zero B(♀) crosses and 0.477 in zero B(♂) one × B(♀) crosses. In crosses where the female had a B chromosome, there were significant differences in transmission rates between pods, but these were not related to differences in G-banding patterns of the B chromosomes involved. In crosses where either the male or female parent had two B chromosomes the B chromosomes did not segregate perfectly, nor did they segregate in a random fashion. The closest resemblance to the behaviour of normal bivalents occurred when the two B chromosomes were of the same, rather than different, G-banding variants, and when they were present in the male rather than the female parent. B chromosomes occurred at eight localities scattered throughout New South Wales. No locality was found where they were not present. The average frequency of B chromosomes was 14.0% for one-B individuals and 0.8% for two-B individuals. There were no significant differences in B-chromosome frequency between males and females. Of the eight localities, only one had a B-chromosome frequency significantly different from any other locality. This relatively uniformity of B-chromosome distribution is interpreted as a consequence of the migratory nature of C. terminifera. A model was constructed to simulate the dynamics of B chromosomes in locust populations. Three main dynamic patterns were recognized, and these were related to differences in the fitness of one-B and two-B individuals. It was concluded that the B chromosome of C. terminifera is probably parasitic, although the simulation model revealed some difficulties which suggest that caution should be applied to the description of any B chromosome as purely parasitic.Key words: B chromosomes, locust, meiotic drive, G-banding, fitness. Chortoicetes terminifera (Walker).

Use of Nest Trees by the Mountain Brushtail Possum (Trichosurus caninus) (Phalangeridae : Marsupialia). III. Spatial Configuration and Co-occupancy of Nest Trees

1997 ◽  
Vol 24 (6) ◽  
pp. 661 ◽  
Author(s):  
D. B. Lindenmayer ◽  
A. Welsh ◽  
C. F. Donnelly
Keyword(s):  
Breeding Season ◽  
Spatial Configuration ◽  
Brushtail Possum ◽  
Adult Males ◽  
Long Distance ◽  
The Core ◽  
Eastern Australia ◽  
Large Trees ◽  
Males And Females ◽  
The Mean

Radio-tracking was used to examine the spatial configuration and co-occupancy of large trees with hollows occupied by 16 mountain brushtail possums (Trichosurus caninus) at Cambarville in the central highlands of Victoria, south-eastern Australia. The distance that animals moved between trees on successive days was also examined. Our analyses showed that animals often remained in a given den tree on successive days. On nights when animals did shift between den sites, they typically moved to a new tree that was relatively nearby (< 200 m). Long-distance movements (e.g. > 300 m) between den trees were rare. Considerable variation was found between individuals in the size of areas encompassing trees used frequently (≥5 times) (‘core denning range’) and those encompassing all occupied trees [i.e. including those used infrequently (< 5 times)] (‘total denning range’). The mean area of the core denning range averaged about 1·1 ha for males and 0·7 ha for females. The mean value for the total denning range was approximately 2·6 ha for males and females respectively. Considerable overlap was found in the total denning ranges of pairs of adult males and pairs of adult females. For most animals, the total denning range was shared with the total denning ranges of several other animals. There was substantial variation in the extent of this overlap, ranging from complete enclosure to the sharing of a single tree. The extent of overlap was more limited for the core denning ranges, particularly among females. We observed differences in the extent of the overlap of the total denning ranges of pairs of males and pairs of females in the breeding season (January–March) and non-breeding season (the remaining months of the year). Fewer instances of overlapping total denning ranges among pairs of both males and females were found during the breeding season. The total denning ranges in the breeding season were generally smaller than those in the non- breeding season. Simultaneous co-occupancy of a given den tree by T. caninus was relatively common. Unexpectedly, there was a number of instances of groups of three or four adult animals sharing the same den site on the same night. We recorded several instances of sharing by pairs of animals of the same sex, especially adult males. However, most records of simultaneous tree use were by an adult male and an adult female T. caninus. The extent of overlap in the denning ranges of animals and the prevalence of simultaneous co-occupancy of den trees indicate that the social behaviour of T. caninus at Cambarville may be different from that observed among populations of the species elsewhere in Australia. Possible reasons for these differences are outlined.

scholarly journals Changing sex for selfish gain: B chromosomes of Lake Malawi cichlid fish

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Frances E. Clark ◽  
Thomas D. Kocher
Keyword(s):  
Linkage Group ◽  
Transmission Rate ◽  
Cichlid Fish ◽  
Meiotic Drive ◽  
B Chromosome ◽  
Lake Malawi ◽  
B Chromosomes ◽  
Normal Complement ◽  
Biased Sex Ratio ◽  
Average Transmission

AbstractB chromosomes are extra, non-essential chromosomes present in addition to the normal complement of A chromosomes. Many species of cichlid fish in Lake Malawi carry a haploid, female-restricted B chromosome. Here we show that this B chromosome exhibits drive, with an average transmission rate of 70%. The offspring of B-transmitting females exhibit a strongly female-biased sex ratio. Genotyping of these offspring reveals the B chromosome carries a female sex determiner that is epistatically dominant to an XY system on linkage group 7. We suggest that this sex determiner evolved to enhance the meiotic drive of the B chromosome. This is some of the first evidence that female meiotic drive can lead to the invasion of new sex chromosomes solely to benefit the driver, and not to compensate for skewed sex ratios.

Variability of skull and dental characteristics in Mus spicilegus from the northern border of its distributional range

Biologia ◽  
2014 ◽  
Vol 69 (10) ◽  
Author(s):  
Alexander Čanády ◽  
Ladislav Mošanský ◽  
Lucia Uličná
Keyword(s):  
Field Trapping ◽  
Regional Level ◽  
Adult Males ◽  
Mean Values ◽  
Mus Spicilegus ◽  
Northern Border ◽  
Skull Measurements ◽  
Males And Females ◽  
The Mean ◽  
Dental Traits

AbstractResults of morphometric analysis of the mound-building mouse (Mus spicilegus) evaluated in this study originate from field trapping in the eastern part of Slovakia during the years 2003–2008. Twenty-four cranial and dental variables and the zygomatic index (A/B) of 80 skulls (43 males, 37 females) were measured and evaluated with respect to the sex of the mice. Despite the fact that the overlap of skull measurements in adult males and females was high, sexual dimorphism was confirmed for several skull and dental traits. On average, the values for adult females of M. spicilegus were higher than males, with the exception of dental traits and the zygomatic index. Significant differences between adult males and females were found for the mean values of ten skull and dental parameters (LB, LCb, FL, LD, LMd, LaZ, LM1, LM1, LaM1 and LaM1). The values for the zygomatic index (A/B) overlapped between both sexes, but the higher average values in adult males were statistically significant. The results showed that the variability of the species confirmed in this paper was probably caused only at the regional level and did not differ from the findings reported by several authors for species from neighboring countries.

scholarly journals Population Cytology of the Genus Phaulacridium VI. Seasonal Changes in the Frequency of the B Chromosome in a Population of Ph. vittatum

1977 ◽  
Vol 30 (4) ◽  
pp. 329 ◽  
Author(s):  
M Westerman ◽  
J Dempsey
Keyword(s):  
Seasonal Changes ◽  
Chiasma Frequency ◽  
Sequential Sampling ◽  
Late Summer ◽  
B Chromosome ◽  
B Chromosomes ◽  
Adult Males ◽  
University Campus ◽  
Maximum Value ◽  
Significant Difference

Sequential sampling of adult males from the La Trobe University campus population of Ph. Vittatum has been carried out over two successive years. Within each year there is seen to be a similar change in frequency of males carrying a large, mitotically stable B chromosome. Early in the summer, when adults first appear, the B frequency of the population is low; it then rises to a maximum value in late summer and then declines once more. Possible reasons for this change in B frequency are discussed. Chiasma frequency scores of individuals with and without B chromosomes were also recorded for each sample. It was found that although at anyone time there was no significant difference between individuals with and without B chromosomes, due no doubt to the small numbers sampled, nonetheless the chiasma frequency of the former was always higher than the latter. Since this was the finding for collections over three years, it is concluded that the B chromosomes of Ph. vittatum, like those of other acridids, raise mean cell chiasma frequency.

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