scholarly journals Mapping of dextral : sinistral proportions in the chirally dimorphic land snail Amphidromus inversus

2015 ◽  
Author(s):  
Menno Schilthuizen ◽  
Sylvia Looijestijn ◽  
Sek Chuan Chua ◽  
Jesús Aguirre Gutiérrez ◽  
Ruth F. Castillo Cajas
Keyword(s):  
Vegetation Structure ◽  
Selection Procedure ◽  
General Linear Model ◽  
Land Snail ◽  
Mirror Image ◽  
Single Population ◽  
Overwhelming Evidence ◽  
Modelling Studies ◽  
Genetically Determined ◽  
Predation Rates

One of the very few snail taxa that display genetic antisymmetry (that is, roughly equal mixes of genetically determined clockwise [D] and anticlockwise [S] coiled individuals within a single population) are the circa 35 species of the tropical tree snail subgenus Amphidromus. Previous work has shown that this may be due to a particular type of sexual selection, in which sperm transfer is improved in copulations between the two mirror-image morphs. However, it is not yet clear why so often significant deviations from 50:50 proportions are found. Modelling studies show that population structure will affect the degree by which the dimorphism is skewed towards the morph associated with the recessive allele. In this study, we mapped the proportions of sinistrals (PropS) in 56 demes in A. inversus on the Malaysian island of Kapas. We also mapped population density, predation rates, and several measures of vegetation structure. Our results show that PropS amounts on average to 0.65, but across the island it varies from 0.30 to 0.85. Density and overall predation are inversely correlated. A general linear model selection procedure results in the proportion of sinistrals to be positively correlated with density and predation on dextrals. We find no overwhelming evidence for a role for drift in explaining the deviations from equal S:D proportions, but we do argue that further study of crab-snail interactions may be warranted.

scholarly journals Mapping of dextral : sinistral proportions in the chirally dimorphic land snail Amphidromus inversus

2015 ◽  
Author(s):  
Menno Schilthuizen ◽  
Sylvia Looijestijn ◽  
Sek Chuan Chua ◽  
Jesús Aguirre Gutiérrez ◽  
Ruth F. Castillo Cajas
Keyword(s):  
Vegetation Structure ◽  
Selection Procedure ◽  
General Linear Model ◽  
Land Snail ◽  
Mirror Image ◽  
Single Population ◽  
Overwhelming Evidence ◽  
Modelling Studies ◽  
Genetically Determined ◽  
Predation Rates

One of the very few snail taxa that display genetic antisymmetry (that is, roughly equal mixes of genetically determined clockwise [D] and anticlockwise [S] coiled individuals within a single population) are the circa 35 species of the tropical tree snail subgenus Amphidromus. Previous work has shown that this may be due to a particular type of sexual selection, in which sperm transfer is improved in copulations between the two mirror-image morphs. However, it is not yet clear why so often significant deviations from 50:50 proportions are found. Modelling studies show that population structure will affect the degree by which the dimorphism is skewed towards the morph associated with the recessive allele. In this study, we mapped the proportions of sinistrals (PropS) in 56 demes in A. inversus on the Malaysian island of Kapas. We also mapped population density, predation rates, and several measures of vegetation structure. Our results show that PropS amounts on average to 0.65, but across the island it varies from 0.30 to 0.85. Density and overall predation are inversely correlated. A general linear model selection procedure results in the proportion of sinistrals to be positively correlated with density and predation on dextrals. We find no overwhelming evidence for a role for drift in explaining the deviations from equal S:D proportions, but we do argue that further study of crab-snail interactions may be warranted.

scholarly journals Mapping of dextral : sinistral proportions in the chirally dimorphic land snail Amphidromus inversus

2014 ◽  
Author(s):  
Menno Schilthuizen ◽  
Sylvia Looijestijn ◽  
Sek Chuan Chua ◽  
Ruth F. Castillo Cajas
Keyword(s):  
Population Structure ◽  
Vegetation Structure ◽  
Predation Rate ◽  
Land Snail ◽  
Mirror Image ◽  
Single Population ◽  
Modelling Studies ◽  
Vegetation Parameters ◽  
Genetically Determined ◽  
Predation Rates

One of the very few snail taxa that display genetic antisymmetry (that is, roughly even mixes of genetically determined clockwise and anticlockwise individuals within a single population) are the circa 35 species of the tropical tree snail subgenus Amphidromus. Previous work has shown that this may be due to a particular type of sexual selection, in which sperm transfer is improved in copulations between the two mirror-image morphs. However, it is not yet clear why so often significant deviations from 50:50 proportions are found. Modelling studies show that population structure will affect the degree by which the dimorphism is skewed towards the morph associated with the recessive allele. In this study, we mapped the proportions of sinistrals (PropS) in 56 demes in A. inversus on the Malaysian island of Kapas. We also mapped population density, predation rates, and several measures of vegetation structure. Our results show that PropS amounts on average to 0.65, but across the island varies from 0.30 to 0.85. Density and overall predation are inversely correlated, but neither predicts PropS. Vegetation parameters also do not correlate with the proportion of sinistrals. We do, however, find a negative correlation between the predation rate on sinistrals and PropS, a finding which may warrant further study.

Effects of early feeding experience and age on the cannibalistic propensity of the land snail Arianta arbustorum

1987 ◽  
Vol 65 (12) ◽  
pp. 3068-3070 ◽  
Author(s):  
Bruno Baur
Keyword(s):  
Land Snail ◽  
Early Feeding ◽  
Vegetable Food ◽  
Egg Cannibalism ◽  
Feeding Experience ◽  
Arianta Arbustorum ◽  
Genetically Determined

The influence of early feeding experience on egg cannibalism was examined in hatchlings of the land snail Arianta arbustorum. The propensity for cannibalism was not affected by cannibalistic or by vegetarian early feeding experience. It was, however, negatively correlated with the age of the snails. Freshly hatched snails with no prior feeding experience chose eggs exclusively, while 16-day-old snails preferred vegetable food. Furthermore, the cannibalistic propensity varied between offspring from different clutches. Restriction of the cannibalistic propensity to the hatchling stage, its nonmodifiability, and differences in its extent between clutches suggest that egg cannibalism in A. arbustorum is a genetically determined trait.

An experimental study of the behavior of blue grouse (Dendragapus obscurus). I. Differences between the founders from three populations

1975 ◽  
Vol 53 (9) ◽  
pp. 1222-1237 ◽  
Author(s):  
Arthur T. Bergerud ◽  
H. Dennis Hemus
Keyword(s):  
Vancouver Island ◽  
Mirror Image ◽  
High Density ◽  
The Other ◽  
Low Density ◽  
Single Population ◽  
High Density Population ◽  
Dendragapus Obscurus ◽  
Field Workers ◽  
Density Population

In 1970 the authors compared the behavior of two low-density populations of blue grouse (Dendragapus obscurus) with the behavior of a high-density population on Vancouver Island. They then introduced individuals from these populations onto four islands and compared the behavior of these founders in 1971 and 1972.One island received founders from all three populations, while the other three islands each received founders from a single population. Birds from two low-density populations were quite observable, and displayed frequently when approached by field workers, both at their capture sites on Vancouver Island and in different habitats on the release sites on islands. The high-density population was much less observable, and displayed less frequently than did the two low-density populations, both at the capture sites and on the release islands. Male founders from the low-density populations were more aggressive in interacting with their mirror image than were males from the high-density population. Male founders from the high-density population dispersed less from the release sites, had smaller territories, and settled closer together than did males from the two low-density populations. These findings are consistent with the view that animals have a form of behavior that spaces them out as numbers rise, and so prevents unlimited increase in numbers.

Mirror Symmetric Topographic Maps Can Arise from Activity-Dependent Synaptic Changes

2005 ◽  
Vol 17 (5) ◽  
pp. 1059-1083 ◽  
Author(s):  
Reiner Schulz ◽  
James A. Reggia
Keyword(s):  
Developmental Disorders ◽  
Rotational Symmetry ◽  
Mirror Image ◽  
Topographic Maps ◽  
Chemical Markers ◽  
Occasional Occurrence ◽  
Synaptic Changes ◽  
Cortical Regions ◽  
Genetically Determined ◽  
Activity Dependent

Multiple adjacent, roughly mirror-image topographic maps are commonly observed in the sensory neocortex of many species. The cortical regions occupied by these maps are generally believed to be determined initially by genetically controlled chemical markers during development, with thalamocortical afferent activity subsequently exerting a progressively increasing influence over time. Here we use a computational model to show that adjacent topographic maps with mirror-image symmetry can arise from activity-dependent synaptic changes whenever the distribution radius of afferents sufficiently exceeds that of horizontal intracortical interactions. Which map edges become adjacent is strongly influenced by the probability distribution of input stimuli during map formation. Our results suggest that activity-dependent synaptic changes may play a role in influencing how adjacent maps become oriented following the initial establishment of cortical areas via genetically determined chemical markers. Further, the model unexpectedly predicts the occasional occurrence of adjacent maps with a different rotational symmetry. We speculate that such atypically oriented maps, in the context of otherwise normally interconnected cortical regions, might contribute to abnormal cortical information processing in some neuro developmental disorders.

III.—Genotypic Asymmetries

1944 ◽  
Vol 62 (1) ◽  
pp. 20-31 ◽  
Author(s):  
Gunnar Dahlberg
Keyword(s):  
Aortic Arch ◽  
Tricuspid Valve ◽  
Human Heart ◽  
Ventral Surface ◽  
Mirror Image ◽  
The Body ◽  
Litter Mate ◽  
Transitional Forms ◽  
The Right ◽  
Genetically Determined

In two earlier publications the author has suggested a theory of genetically determined asymmetries. Inherited asymmetry may be of two types. Many characters are unilateral (e.g. the aortic arch or the tricuspid valve of the human heart) or in some other way placed asymmetrically (e.g. the differentiation of organs along the cephalad-caudad axis of the body). The orientation of such gross asymmetries is in general irreversible. The author has pointed out that the study of uniovular twins which exhibit mirror-image similarities draws attention to a smaller class of reversible asymmetries. While an asymmetrical disposition of such a character is transmitted, its orientation is not fixed in the process of transmission. Thus a character may show itself on the left side in one generation or in one individual of a litter, and on the right side in another generation or in a litter mate. The extreme types of variation between which many transitional forms may be found are:(a) From left to right, or vice versa.(b) From caudad to cephalad extremity, or vice versa.(c) From dorsal to ventral surface, or vice versa.

scholarly journals Does Habitat Fragmentation Influence Nest Predation in the Shortgrass Prairie?

The Condor ◽  
2001 ◽  
Vol 103 (3) ◽  
pp. 530-536 ◽  
Author(s):  
Melissa N. Howard ◽  
Susan K. Skagen ◽  
Patricia L. Kennedy
Keyword(s):  
Habitat Fragmentation ◽  
Vegetation Structure ◽  
Nest Predation ◽  
Patch Size ◽  
Mortality Rates ◽  
Artificial Nests ◽  
Vegetation Height ◽  
Native Grassland ◽  
Shortgrass Prairie ◽  
Predation Rates

Abstract We examined the effects of habitat fragmentation and vegetation structure of shortgrass prairie and Conservation Reserve Program (CRP) lands on predation rates of artificial and natural nests in northeastern Colorado. The CRP provides federal payments to landowners to take highly erodible cropland out of agricultural production. In our study area, CRP lands have been reseeded primarily with non-native grasses, and this vegetation is taller than native shortgrass prairie. We measured three indices of habitat fragmentation (patch size, degree of matrix fragmentation, and distance from edge), none of which influenced mortality rates of artificial or natural nests. Vegetation structure did influence predation rates of artificial nests; daily mortality decreased significantly with increasing vegetation height. Vegetation structure did not influence predation rates of natural nests. CRP lands and shortgrass sites did not differ with respect to mortality rates of artificial nests. Our study area is only moderately fragmented; 62% of the study area is occupied by native grassland. We conclude that the extent of habitat fragmentation in our study area does not result in increased predation in remaining patches of shortgrass prairie habitat. ¿La Fragmentación de Hábitat Influencia la Depredación de Nidos en Praderas de Pasto Corto? Resumen. Examinamos los efectos de fragmentación de hábitat y estructura de la vegetación sobre la tasa de depredación de nidos artificiales y naturales en praderas de pasto corto y tierras del Programa de Reserva de Conservación (CRP) en el noreste de Colorado. El CRP proporciona pagos federales para que los dueños de las tierras retiren sus cultivos de áreas agrícolas altamente erosionables. En nuestra área de estudio, las tierras de CRP han sido vueltas a sembrar principalmente con céspedes no nativos que son más altos que la vegetación nativa de las praderas de pasto corto. Medimos tres índices de fragmentación de hábitat (tamaño del parche, grado de fragmentación de la matriz, y distancia al borde), ninguno de los cuales influyó sobre la tasa de mortalidad de nidos artificiales o naturales. La estructura de la vegetación influenció la tasa de depredación de nidos artificiales: la mortalidad diaria disminuyó significativamente con incrementos en la altura de la vegetación. La estructura de la vegetación no influenció la tasa de depredación de nidos naturales. Los sitios de CRP y de pastos cortos no difirieron con respecto a la tasa de mortalidad de nidos artificiales. Nuestra área de estudio es sólo moderadamente fragmentada pues el 62% del área es ocupada por prado nativo. Concluimos que el grado de fragmentación de hábitat en nuestra área del estudio no causa aumentos en la depredación en los parches de hábitat remanentes.

scholarly journals Snail shell colour evolution in urban heat islands detected via citizen science

2018 ◽  
Author(s):  
Niels A. G. Kerstes ◽  
Thijmen Breeschoten ◽  
Vincent Kalkman ◽  
Menno Schilthuizen
Keyword(s):  
Citizen Science ◽  
Elevated Temperatures ◽  
Land Snail ◽  
Urban Heat Islands ◽  
City Centre ◽  
Heat Islands ◽  
Cepaea Nemoralis ◽  
Urban Heat ◽  
Genetically Determined ◽  
The City

AbstractThe extreme environmental conditions that prevail in cities are known to cause selection pressures leading to adaptive changes in wild, city-dwelling, organisms (“urban evolution”). The urban heat island, elevated temperatures in the city centre due to a combination of generation, reflection, and trapping of heat, is one of the best recognised and most widespread urban environmental factors. Here, we used a citizen-science approach to study the effects of urban heat on genetically-determined shell colour in the land snail Cepaea nemoralis in the Netherlands. We used smartphone applications to obtain colour data on almost 8,000 snails throughout the country. Our analysis shows that snails in urban centres are more likely to be yellow than pink, an effect predicted on the basis of thermal selection. Urban yellow snails are also more likely to carry dark bands at the underside of the shell; these bands might affect thermoregulation in yet underexplored ways.

EPILEPSY, LIGHT-SENSITIVITY AND LEFT-HANDEDNESS IN A FAMILY WITH MONOZYGOTIC TRIPLETS

PEDIATRICS ◽  
1960 ◽  
Vol 25 (3) ◽  
pp. 385-399
Author(s):  
Karl-Magnus Herrlin
Keyword(s):  
Light Sensitivity ◽  
Mirror Image ◽  
Intermittent Light ◽  
Left Handedness ◽  
Left Handed ◽  
Cerebral Dysfunction ◽  
Photogenic Epilepsy ◽  
Genetically Determined ◽  
Light Flashes ◽  
Papillary Pattern

A family consisting of monozygotic, now 14-year-old triplets, their elder brother and parents are described. One triplet is right-handed and the other two are left-handed, as are a number of their relatives. After an analysis of the probable course in cleavage of the embryos, the hypothesis is put forward that the different handedness is due to a mirror-image mechanism in cleavage of one or possibly of both embryos. It is suggested that such a mechanism can also explain the reversed asymmetry in the papillary pattern of their hand prints in the hypothenar region. In the mother, myoclonic jerks are elicited by intermittent sunlight. During photic stimulation with the stroboscope, they are synchronous with the light flashes. The elder son has photogenic epilepsy. In his case, as in the triplets, intermittent light flashes from the stroboscope elicit a clinical seizure. It is postulated that the sensitivity to light in this family is due to a probably dominant, genetically determined cerebral dysfunction, which can be manifested clinically in different ways.

scholarly journals Vegetation structure influences predation rates of early nests in subarctic breeding waders

Ibis ◽  
2020 ◽  
Vol 162 (4) ◽  
pp. 1225-1236 ◽  
Author(s):  
Rebecca A. Laidlaw ◽  
Tómas G. Gunnarsson ◽  
Verónica Méndez ◽  
Camilo Carneiro ◽  
Böðvar Þórisson ◽  
...  
Keyword(s):  
Vegetation Structure ◽  
Breeding Waders ◽  
Predation Rates
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