The Atlantic sand fiddler crab Uca pugilator is an extremely abundant crab found along the eastern coast of the United States. Fiddler crabs have a life cycle with an obligatory planktonic larval phase of 30-90 days,w...The Atlantic sand fiddler crab Uca pugilator is an extremely abundant crab found along the eastern coast of the United States. Fiddler crabs have a life cycle with an obligatory planktonic larval phase of 30-90 days,which might be expected to lead to widespread larval dispersal and consequent genetic homogeneity over considerable distances. However,a large amount of morphological and behavioral variation is found between northern and southern populations along the eastern coast. This study was undertaken to determine the population genetic structure of U.pugilator and to determine whether these differences may have a genetic basis. The population structure of the fiddler crab was analyzed using 472 individuals collected from 12 sites along the eastern coast. PCR-based single stand conformation polymorphism (SSCP) was used to investigate between-site variation in the mitochondrial 16S rRNA gene of these individuals. Analysis of genetic variation indicated frequent gene flow between nearby localities,but much reduced levels between populations separated by larger geographic distances. Thus,despite the potential for high dispersal by planktonic larvae,population differentiation and isolation by distance is evident between northern and southern populations of U.pugilator. A high amount of genetic differentiation (F ST =0.3468) was found between northern and southern regions suggesting that the morphological and behavioral differences between these two regions have a genetic basis and may represent subspecies.展开更多
<span style="font-family:Verdana;">Fiddler crabs are described as ecosystem engineers because of their burrow constructing ability. It was hypothesized that human activity will impact crab burrows. The...<span style="font-family:Verdana;">Fiddler crabs are described as ecosystem engineers because of their burrow constructing ability. It was hypothesized that human activity will impact crab burrows. The study area was delineated into lowly, medium and highly impacted plots. Crab holes were randomly counted and their width, length and surface area estimated. Burrow soils were collected and analyzed for Cadmium (Cd), Lead (Pb) and Zinc (Zn) using spectrophotometric method (HACH DR 890 colorimeter). The result indicates that burrow width was significantly different between impacted plots (P < 0.05). Lowly impacted plot had the largest width while highly impacted plot had the smallest width. In contrast, there was no significant difference in burrow length (P > 0.05), but highly impacted plot has the longest length while lowly impacted plot has the shortest length. Again, the surface area of crab burrow varies significantly (P < 0.05), and lowly impacted plot had the largest area (507.95 ± 61.84 cm<sup><span style="font-family:Verdana;">2</sup><span style="font-family:Verdana;">) followed by medium (390.30 ± 57.65 cm<sup><span style="font-family:Verdana;">2</sup><span style="font-family:Verdana;">) and high (265.16 ± 30.85 cm<sup><span style="font-family:Verdana;">2</sup><span style="font-family:Verdana;">) impacted plots. Similarly, lowly impacted area has more number of burrows (<span style="font-family:Verdana;">n <span style="font-family:Verdana;">= 55) followed by medium (<span style="font-family:Verdana;">n <span style="font-family:Verdana;">= 30) and highly (<span style="font-family:Verdana;">n<span style="font-family:Verdana;"> = 23) impacted plots. Highly impacted plot had the highest Cd and Pb concentration whereas lowly impacted plot had the highest Zn concentration. This implies that burrow morphology and chemistry exemplify the level of anthropogenic impact.展开更多
The continuous excavation of burrows by fiddler crabs generates bioturbation in the sediment,which can be estimated from burrow morphology.The aim of the present study was to describe the burrow morphology of Uca urug...The continuous excavation of burrows by fiddler crabs generates bioturbation in the sediment,which can be estimated from burrow morphology.The aim of the present study was to describe the burrow morphology of Uca uruguayensis and U.leptodactylus and its relationship with demography of resident individuals and to estimate the level of bioturbation in the sediment generated by each species.For all individuals from each of the 2 species,sex was determined and the carapace width(CW;mm)measured.Burrows were characterized according to burrow diameter(BD;mm),maximum burrow depth(MBD;mm)and burrow volume(BV;cm^(3)).The density of each species in the study area was also evaluated.In both species,the males were larger and occupied burrows with higher BV compared to females.Differences between sexes in relation to the burrow characteristics might reflect sexual dimorphism within the group and are probably related to the fact that males use the burrows for mating.BD and BV showed significant positive relationships with the size of resident crabs.The amount of sediment removed per burrow was estimated from mean BV:10.78 cm^(3)of sediment/burrow for U.uruguayensis and 12.38 cm^(3)of sediment/burrow for U.leptodactylus.Despite the density and depth differences between the 2 species,the similarity in burrow volume suggests that U.uruguayensis and U.leptodactylus present the same importance in terms of the bioturbation process.Burrow morphology is highly associated with characteristics of the occupant,although extrinsic factors should also be considered,and its description can provide estimates on the bioturbation generated by Uca species in mangrove forests.展开更多
基金supported by grants from Academic Excellence, Allen Paulson College of Science and Technology and Graduate Funds from Jack N. Averitt College of Graduate Studies, Georgia Southern University
文摘The Atlantic sand fiddler crab Uca pugilator is an extremely abundant crab found along the eastern coast of the United States. Fiddler crabs have a life cycle with an obligatory planktonic larval phase of 30-90 days,which might be expected to lead to widespread larval dispersal and consequent genetic homogeneity over considerable distances. However,a large amount of morphological and behavioral variation is found between northern and southern populations along the eastern coast. This study was undertaken to determine the population genetic structure of U.pugilator and to determine whether these differences may have a genetic basis. The population structure of the fiddler crab was analyzed using 472 individuals collected from 12 sites along the eastern coast. PCR-based single stand conformation polymorphism (SSCP) was used to investigate between-site variation in the mitochondrial 16S rRNA gene of these individuals. Analysis of genetic variation indicated frequent gene flow between nearby localities,but much reduced levels between populations separated by larger geographic distances. Thus,despite the potential for high dispersal by planktonic larvae,population differentiation and isolation by distance is evident between northern and southern populations of U.pugilator. A high amount of genetic differentiation (F ST =0.3468) was found between northern and southern regions suggesting that the morphological and behavioral differences between these two regions have a genetic basis and may represent subspecies.
文摘<span style="font-family:Verdana;">Fiddler crabs are described as ecosystem engineers because of their burrow constructing ability. It was hypothesized that human activity will impact crab burrows. The study area was delineated into lowly, medium and highly impacted plots. Crab holes were randomly counted and their width, length and surface area estimated. Burrow soils were collected and analyzed for Cadmium (Cd), Lead (Pb) and Zinc (Zn) using spectrophotometric method (HACH DR 890 colorimeter). The result indicates that burrow width was significantly different between impacted plots (P < 0.05). Lowly impacted plot had the largest width while highly impacted plot had the smallest width. In contrast, there was no significant difference in burrow length (P > 0.05), but highly impacted plot has the longest length while lowly impacted plot has the shortest length. Again, the surface area of crab burrow varies significantly (P < 0.05), and lowly impacted plot had the largest area (507.95 ± 61.84 cm<sup><span style="font-family:Verdana;">2</sup><span style="font-family:Verdana;">) followed by medium (390.30 ± 57.65 cm<sup><span style="font-family:Verdana;">2</sup><span style="font-family:Verdana;">) and high (265.16 ± 30.85 cm<sup><span style="font-family:Verdana;">2</sup><span style="font-family:Verdana;">) impacted plots. Similarly, lowly impacted area has more number of burrows (<span style="font-family:Verdana;">n <span style="font-family:Verdana;">= 55) followed by medium (<span style="font-family:Verdana;">n <span style="font-family:Verdana;">= 30) and highly (<span style="font-family:Verdana;">n<span style="font-family:Verdana;"> = 23) impacted plots. Highly impacted plot had the highest Cd and Pb concentration whereas lowly impacted plot had the highest Zn concentration. This implies that burrow morphology and chemistry exemplify the level of anthropogenic impact.
基金The Fundação de AmparoàPesquisa do Estado de São Paulo provided the first author a scientific undergraduate scholarship(2010/01252-5)。
文摘The continuous excavation of burrows by fiddler crabs generates bioturbation in the sediment,which can be estimated from burrow morphology.The aim of the present study was to describe the burrow morphology of Uca uruguayensis and U.leptodactylus and its relationship with demography of resident individuals and to estimate the level of bioturbation in the sediment generated by each species.For all individuals from each of the 2 species,sex was determined and the carapace width(CW;mm)measured.Burrows were characterized according to burrow diameter(BD;mm),maximum burrow depth(MBD;mm)and burrow volume(BV;cm^(3)).The density of each species in the study area was also evaluated.In both species,the males were larger and occupied burrows with higher BV compared to females.Differences between sexes in relation to the burrow characteristics might reflect sexual dimorphism within the group and are probably related to the fact that males use the burrows for mating.BD and BV showed significant positive relationships with the size of resident crabs.The amount of sediment removed per burrow was estimated from mean BV:10.78 cm^(3)of sediment/burrow for U.uruguayensis and 12.38 cm^(3)of sediment/burrow for U.leptodactylus.Despite the density and depth differences between the 2 species,the similarity in burrow volume suggests that U.uruguayensis and U.leptodactylus present the same importance in terms of the bioturbation process.Burrow morphology is highly associated with characteristics of the occupant,although extrinsic factors should also be considered,and its description can provide estimates on the bioturbation generated by Uca species in mangrove forests.
