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PubMed2005

Genome-scale evidence of the nematode-arthropod clade.

BACKGROUND: The issue of whether coelomates form a single clade, the Coelomata, or whether all animals that moult an exoskeleton (such as the coelomate arthropods and the pseudocoelomate nematodes) form a distinct clade, the Ecdysozoa, is the most puzzling issue in animal systematics and a major open-ended subject in evolutionary biology. Previous single-gene and genome-scale analyses designed to resolve the issue have produced contradictory results. Here we present the first genome-scale phylogenetic evidence that strongly supports the Ecdysozoa hypothesis. RESULTS: Through the most extensive phylogenetic analysis carried out to date, the complete genomes of 11 eukaryotic species have been analyzed in order to find homologous sequences derived from 18 human chromosomes. Phylogenetic analysis of datasets showing an increased adjustment to equal evolutionary rates between nematode and arthropod sequences produced a gradual change from support for Coelomata to support for Ecdysozoa. Transition between topologies occurred when fast-evolving sequences of Caenorhabditis elegans were removed. When chordate, nematode and arthropod sequences were constrained to fit equal evolutionary rates, the Ecdysozoa topology was statistically accepted whereas Coelomata was rejected. CONCLUSIONS: The reliability of a monophyletic group clustering arthropods and nematodes was unequivocally accepted in datasets where traces of the long-branch attraction effect were removed. This is the first phylogenomic evidence to strongly support the 'moulting clade' hypothesis.

Animals↗

PubMed1999

Analysis of molecular marker expression reveals neuronal homology in distantly related arthropods.

Morphological studies suggest that insects and crustaceans of the Class Malacostraca (such as crayfish) share a set of homologous neurons. However, expression of molecular markers in these neurons has not been investigated, and the homology of insect and malacostracan neuroblasts, the neural stem cells that produce these neurons, has been questioned. Furthermore, it is not known whether crustaceans of the Class Branchiopoda (such as brine shrimp) or arthropods of the Order Collembola (springtails) possess neurons that are homologous to those of other arthropods. Assaying expression of molecular markers in the developing nervous systems of various arthropods could resolve some of these issues. Here, we examine expression of Even-skipped and Engrailed, two transcription factors that serve as insect embryonic CNS markers, across a number of arthropod species. This molecular analysis allows us to verify the homology of previously identified malacostracan neurons and to identify additional homologous neurons in malacostracans, collembolans and branchiopods. Engrailed expression in the neural stem cells of a number of crustaceans was also found to be conserved. We conclude that despite their distant phylogenetic relationships and divergent mechanisms of neurogenesis, insects, malacostracans, branchiopods and collembolans share many common CNS components.

Animals↗

PubMed2002

Parasegmental organization of the spider embryo implies that the parasegment is an evolutionary conserved entity in arthropod embryogenesis.

Spiders belong to the chelicerates, which is a basal arthropod group. To shed more light on the evolution of the segmentation process, orthologs of the Drosophila segment polarity genes engrailed, wingless/Wnt and cubitus interruptus have been recovered from the spider Cupiennius salei. The spider has two engrailed genes. The expression of Cs-engrailed-1 is reminiscent of engrailed expression in insects and crustaceans, suggesting that this gene is regulated in a similar way. This is different for the second spider engrailed gene, Cs-engrailed-2, which is expressed at the posterior cap of the embryo from which stripes split off, suggesting a different mode of regulation. Nevertheless, the Cs-engrailed-2 stripes eventually define the same border as the Cs-engrailed-1 stripes. The spider wingless/Wnt genes are expressed in different patterns from their orthologs in insects and crustaceans. The Cs-wingless gene is expressed in iterated stripes just anterior to the engrailed stripes, but is not expressed in the most ventral region of the germ band. However, Cs-Wnt5-1 appears to act in this ventral region. Cs-wingless and Cs-Wnt5-1 together seem to perform the role of insect wingless. Although there are differences, the wingless/Wnt-expressing cells and en-expressing cells seem to define an important boundary that is conserved among arthropods. This boundary may match the parasegmental compartment boundary and is even visible morphologically in the spider embryo. An additional piece of evidence for a parasegmental organization comes from the expression domains of the Hox genes that are confined to the boundaries, as molecularly defined by the engrailed and wingless/Wnt genes. Parasegments, therefore, are presumably important functional units and conserved entities in arthropod development and form an ancestral character of arthropods. The lack of by engrailed and wingless/Wnt-defined boundaries in other segmented phyla does not support a common origin of segmentation.

Amino Acid Sequence↗

PubMed2002

The midgut epithelium of aquatic arthropods: a critical target organ in environmental toxicology.

The midgut epithelium of aquatic arthropods is emerging as an important and toxicologically relevant organ system for monitoring environmental pollution. The peritrophic matrix of aquatic arthropods, which is secreted by the midgut epithelium cells, is perturbed by copper or cadmium. Molecular biological studies have identified and characterized two midgut genes induced by heavy metals in the midgut epithelium. Many other metal-responsive genes (MRGs) await characterization. One of the MRGs codes for an intestinal mucin, which is critical for protecting the midgut from toxins and pathogens. Another codes for a tubulin gene, which is critical for structure and function of the midgut epithelial cells. Perturbation of expression of either gene could condition aquatic arthropod survivorship. Induction of these MRGs is a more sensitive and rapid indicator of heavy-metal pollution than biological assays. Characterization of genes induced by pollutants could provide mechanistic understanding of fundamental cellular responses to pollutants and insight into determinants of aquatic arthropod population genetic structure and survivorship in nature.

Aedes↗

PubMed1992

Epidemiology and control of malaria and other arthropod-borne diseases.

Malaria and other arthropod born diseases remain a serious public health problem affecting the lives and health of certain social groups when the two basic strategies to control fail due to: (1) the lack of effective chemoprophylaxis/chemotherapy or the rapid development of drug resistance of the infectious agents and (2) the ineffectiveness of pesticides or the arthropod vectors develop resistance to them. These situations enhances the need for the design and implementation of other alternatives for sustainable health programmes. The application of the epidemiological methods is essential not only for analyzing the relevant data for the understanding of the biological characteristics of the infectious agents, their reservoirs and vectors and the methods for their control, but also for the assessment of the human behaviour, the environmental, social and economic factors involved in disease transmission and the capacity of the health systems to implement interventions for both changes in human behaviour and environmental management to purpose guaranteed prevention and control of malaria and other arthropod born diseases with efficiency, efficacy and equity. This paper discuss the evolution of the malaria and arthropod diseases programmes in the American Region and the perspectives for their integration into health promotion programs and emphasis is made in the need to establish solid basis in the decision-making process for the selection of intervention strategies to remove the risk factors determining the probability to get sick or die from ABDs. The implications of the general planning and the polices to be adopted in an area should be analyzed in the light of programme feasibility at the local level, in the multisectoral context of specific social groups and taking in consideration the principles of stratification and equity.

Animals↗

PubMedDate not supplied

Diversity of galling arthropods and host plants in a subtropical forest of Porto Alegre, southern Brazil.

Many hypotheses have been proposed to explain diversity patterns of galling insects. However, there are contradictory evidences on the evolutionary and ecological factors responsible for the trends. Furthermore, questions such as arthropod seasonality, sampling sufficiency and sampling team experience have been almost ignored. This study records galling arthropod diversity while paying attention to these questions. Seasonal sampling of galling arthropods and host plants were conducted in a humid subtropical forest of southern Brazil. Four transects were sampled twice per season, with two persons searching the vegetation for galls during 1h30min. After 96h.persons of sampling, 130 gall morphotypes on 84 species of host plants were recorded. An analysis of the numbers of galls and gall morphotypes found per transect along time showed that sampling team experience influences galler richness results and the interpretation of galler seasonality patterns. Different species had distinct seasonal patterns. Galling arthropod richness was bound to plant richness. Our results suggest that sampling team experience is an important factor that must be explicitly considered, as well as seasonality patterns of different galling species, at least for tropical/subtropical areas. Although sampling sufficiency was not reached, fauna heterogeneity at small spatial scales seems substantial: despite the proximity of the sampled transects (500 m), they harboured significantly specific faunas. This work adds to the literature records suggesting that both plant richness and specific composition of the vegetation have a strong influence on galler richness at least for local scales.

Animals↗

PubMed2001

Effects of an application of granular carbaryl on nontarget forest floor arthropods.

We evaluated the effects of a single application of granular carbaryl made against nymphal Ixodes scapularis Say on the diversity and abundance of forest arthropods taken in pitfall traps in oak and mixed oak-pine forest sites for 12 wk after treatment in central New Jersey. Significant short-term changes in arthropod assemblages were detected immediately posttreatment. Effects were not distributed equally across taxa. Seasonal changes in numbers and diversity of forest arthropods in the study areas may have affected the impact of the acaricide in the treatment area. Comparison with control areas indicated that reductions in abundance of some arthropod taxa in the treatment area were detectable 12 wk after treatment.

Animals↗

PubMed2000

Introduction of nonindigenous arthropod pests of animals.

A variety of pathways exist for the introduction of nonindigenous insects, ticks, and mites of veterinary importance into the United States. The most prominent includes the natural migration of mosquitoes and flies by the flight of adults, ectoparasites entering the country on wildlife transport hosts, and accidental introductions on animals legally imported through United States Department of Agriculture (USDA) quarantine facilities. Examples of the establishment and subsequent eradication of exotic pests of livestock are presented to illustrate the critical role of the USDA in protecting American agriculture with particular emphasis on the southern cattle tick, Boophilus microplus (Canestrini), the cattle tick, B. annulatus (Say), and the screwworm, Cochliomyia hominivorax (Coquerel). Priority group rating of nonindigenous arthropod pests and disease vectors are discussed. Although the primary responsibility for preventing the introduction and establishment of arthropods that affect livestock and poultry rests on the shoulders of USDA professionals, insect surveys by extension entomologists along with observations by research specialists and producers are also important in detecting exotic arthropod species. Animal health professionals from all sectors of the livestock and poultry industries may well be the first line of defense from the introduction of nonindigenous arthropods and the diseases they transmit.

Animal Diseases↗

PubMed2001

Arthropods as predators of ticks (Ixodoidea).

The existing information on arthropods as predators of ticks is based mainly on sporadic observations and their role in reducing tick populations and in most cases is still not clear. Some reports suggest that in certain ecological habitats arthropods play an important role in the control of the tick population. This publication reports on some 100 relevant publications that appeared between 1906 and 1999. Ants, beetles, and spiders seem to be the major arthropods preying on ticks. In general, engorged ticks are more often preyed upon by arthropods than are unfed or feeding ticks.

Animals↗

PubMed2004

Ectoparasites and other epifaunistic arthropods of sympatric cotton mice and golden mice: comparisons and implications for vector-borne zoonotic diseases.

Ectoparasite and epifaunistic arthropod biodiversity and infestation parameters were compared between 2 sympatric small rodent species, the cotton mouse (Peromyscus gossypinus (Le Conte)) and golden mouse (Ochrotomys nuttalli (Harlan)), in southern Georgia from 1992 to 2003. Because the cotton mouse is known to be a reservoir of more vector-borne zoonotic pathogens than the golden mouse, we hypothesized that it would be parasitized by more ectoparasites that are known to be vectors of these pathogens. Cotton mice (n = 202) were parasitized by 19 species of arthropods, whereas golden mice (n = 46) were parasitized by 12 species. Eleven species of arthropods were recovered from both host species, whereas 7 were recorded only from cotton mice, and 1 species only from golden mice. Infestation prevalences (percent of mice parasitized) were significantly higher for 1 species of arthropod (the tropical rat mite Ornithonyssus bacoti (Hirst)) infesting cotton mice and for 4 species (the flea Peromyscopsylla scotti Fox and the mites Glycyphagus hypudaei Koch, Androlaelaps casalis (Berlese), and Androlaelaps fahrenholzi (Berlese)) infesting golden mice. Mean intensities (mean per infested mouse) were significantly higher for 2 species (the flea Orchopeas leucopus (Baker) and the blacklegged tick Ixodes scapularis Say) infesting cotton mice and for 2 species (G. hypudaei and A. fahrenholzi) infesting golden mice. Ectoparasites that are known to be vectors of zoonotic pathogens were significantly more common on cotton mice than on golden mice. These ectoparasites included the rhopalopsyllid flea Polygenis gwyni (Fox), a vector of the agent of murine typhus; I. scapularis, the principal vector of the agents of Lyme borreliosis, human granulocytic ehrlichiosis, and human babesiosis; and O. bacoti, a laboratory vector of several zoonotic pathogens. However, 2 species of ixodid ticks that can transmit zoonotic pathogens were recovered from both host species. These were the American dog tick Dermacentor variabilis (Say), the principal vector of the agent of Rocky Mountain spotted fever in eastern North America, and Ixodes minor Neumann, an enzootic vector of the agent of Lyme borreliosis. Overall, the cotton mouse was parasitized by significantly more ectoparasites that are known to be vectors of zoonotic pathogens than was the golden mouse. These data support the hypothesis that the cotton mouse has greater epidemiological importance for zoonotic vector-borne pathogen transmission than does the golden mouse.

Animals↗

PubMedDate not supplied

Rickettsial pathogens and their arthropod vectors.

Rickettsial diseases, important causes of illness and death worldwide, exist primarily in endemic and enzootic foci that occasionally give rise to sporadic or seasonal outbreaks. Rickettsial pathogens are highly specialized for obligate intracellular survival in both the vertebrate host and the invertebrate vector. While studies often focus primarily on the vertebrate host, the arthropod vector is often more important in the natural maintenance of the pathogen. Consequently, coevolution of rickettsiae with arthropods is responsible for many features of the host-pathogen relationship that are unique among arthropod-borne diseases, including efficient pathogen replication, long-term maintenance of infection, and transstadial and transovarial transmission. This article examines the common features of the host-pathogen relationship and of the arthropod vectors of the typhus and spotted fever group rickettsiae.

Animals↗

PubMed1991

Parasitic and phoretic arthropods of the elephant-eared and the Santa Cruz kangaroo rats.

The parasitic and phoretic arthropods of the elephant-eared kangaroo rat (Dipodomys elephantinus) and Santa Cruz kangaroo rat (D. venustus) are reported; most of these represent new host records. Thirteen of 14 (93%) of D. elephantinus and 11 of 12 (92%) of D. venustus had 11 and nine arthropod species, respectively. Larval and nymphal stages of the tick Dermacentor occidentalis were the most prevalent parasite (77%) on D. elephantinus whereas the mesostigmatid mite Androlaelaps fahrenholzi was the most prevalent (56%) on D. venustus. The arthropod fauna of these two closely related rodents were similar with seven of the 14 arthropod species occurring on both host species. Two species of the host specific listrophorid mite of the genus Geomylichus were found on both hosts.

Animals↗

PubMed1998

[The principal arthropod vectors of disease. What are the risks of travellers' to be bitten? To be infected?].

Many blood-sucking arthropods are potential vectors of disease. To become a vector, the arthropod must be susceptible to the infective agent and must survive the incubation period so as to transmit the pathogens to a host. While some arthropod associated diseases affect only man (e.g. malaria) most of these diseases are (anthropo-) zoonoses with man often an accidental host. The risk of contamination depends on the one hand on the biting behaviour of the vector, its biology and distribution, and on the other hand on the sites visited by the traveller, the length of his stay, his activities, the conditions of sleeping accommodation. The risk of contracting malaria is very high in tropical Africa, in the forest area of South America and South East Asia, in Papua New Guinea. Malaria can be prevented if measures (e.g. pyrethroid impregnated bed nets, repellents) are taken to avoid bites of Anopheline mosquitoes between sunset and sunrise, but appropriate chemoprophylaxis must not be neglected. Lethal cases of yellow fever among unvaccinated travellers still occur despite a strict international regulation on vaccination requirements. Dengue is a major health problem in intertropical areas. As no vaccine is available, personal protection measures are recommended against daytime-biting mosquitoes, including the use of protective clothing, repellents. Other arthropod borne diseases among travellers are less common but the risks increase during adventure trips (e.g. zoonotic leishmaniasis, tick-borne relapsing fever) and humanitarian actions (e.g. risk of louse-borne typhus during visits of overcrowded prisons). Tick-borne diseases receive nowadays more attention. These diseases are not only restricted to some occupations (farmers, veterinarians) but also ramblers and campers are at risk. Attached ticks should be removed rapidly and carefully, since several hours of attachment are needed for transmission of spirochetes of LYME disease.

Animals↗

PubMed2000

Phylogenetic analysis of the Wnt gene family and discovery of an arthropod wnt-10 orthologue.

Wnt genes encode a conserved family of secreted signaling proteins that play many roles in arthropod and vertebrate development. We have investigated both the phylogenetic history and molecular evolution of this gene family. We have identified a novel Wnt gene in a diversity of arthropods that it is likely an orthologue of the vertebrate Wnt-10 group. Wnt-10 is one of only two cases in which orthology between protostome and deuterostome genes could be consistently assigned based on our analyses. Despite difficulties in assessing orthologies, all of our trees suggest that the most recent common ancestor of protostomes and deuterostomes possessed more than the five Wnt genes known from either arthropods or nematodes. This suggests that Wnt gene loss has occurred during protostome evolution. In addition, we examined the rate of amino acid evolution in the two arthropod/deuterostome orthology groups we identified. We found little rate variation across taxa, with the exception that Drosophila Wnt-1 is evolving more rapidly than all vertebrate and most arthropod orthologues.

Amino Acid Sequence↗

PubMed2002

[Temporal pattern of arthropod community on cultivated alfalfa grassland].

The variation of species and diversities of the arthropod community on cultivated alfalfa grassland was investigated and studied. Principal component analysis and optimal sorting method were used to study its temporal patterns. The results showed that the difference and regularity of species richness, and the diversity and evenness of the arthropod community at different time were obvious. The numbers of the species of insect pests and their natural enemies were the most in the last ten days of June, but the peak period of individual numbers of the natural enemies was later than that of insect pests. The main factors and temporal patterns of arthropod community in the course of seasons were obvious. Based on the results, the temporal patterns of arthropod community on cultivated alfalfa grassland could be divided into four stages: before the first ten days of May, the middle ten days of May to the first ten days of June, the middle ten days of June to the middle ten days of July, and after the middle ten days of July. Considering the climatic and phenological development, the characteristics of the pests and the natural enemies occurring in each stage were analyzed, and the corresponding management tactics were discussed.

Animals↗

PubMed2004

[Community structure and seasonal change of soil micro-arthropodes in the Lower Reaches of Liaohe River Plain under different land utilization].

The data on the soil micro-arthropodes under four land utilization types (fallow, forest, upland field and paddy) in the Lower Reaches of Liaohe River Plain were collected in a period from October 2000 to October 2001. Using the community parameters of population density, group richness, diversity index and evenness, the community structure and its seasonal changes were described. There were 12 groups of soil micro-arthropodes in this region, and of the groups, Collembola and Acarina were dominant, and Diptera, Coleoptera and Hymenoptera were often seen in fallow, forest and upland field, while Collembola, Acarina and Diptera were dominant in paddy. Both land utilization and seasonal change influenced the population density, group richness and diversity index of soil micro-arthropodes. The vertical distribution in both density and group number of arthropods in soil was in the order of surface > middle > bottom.

Agriculture↗

PubMed2005

[Effects of herbicides on diversity indices of cotton field arthropod community].

This paper studied the differences of the diversity, abundance and evenness of arthropod community and sub-community in cotton field among treatments haloxyfor-k (A), paraquat (B) and contrast (CK). The results showed that in the diversity of phytophagous sub-community, tA-CK = 3.099 and tB-CK = 2.449 (t > t0.05 = 2.228), the difference being significant, and in the diversity of predatory sub-community, tA-B = 2.260 and tA-CK = 2.377 (t > t0.05 = 2.228), the difference being also significant. In the arthropod community and sub-community, no significant difference was found for A-CK, B-CK and A-B. The abundance of arthropod community tA- CK = 4.359, and that of phytophagous sub-community tA-CK = 2.963, the effect being all significant (t > t0.05 = 2.228). No significant difference was found in the evenness of arthropod community and sub-community for A-B, A-CK and B-CK. The biodiversity had the same change trend for treatments haloxyfor-R (A) paraquat (B) and contrast (CK).

Animals↗

PubMed2005

[Community structure and its dynamics of predatory arthropod in different tobacco varieties fields].

With principal component analysis and using community structural characteristic indices, this paper studied the community structure and its dynamics of predatory arthropod in fields planted with tobacco varieties Nc89, Nc82 and K326. The results showed that in all test fields, spiders and predatory insects were the predominant components of the predatory arthropod community, and their relative abundances were 83.25%-86.87% and 13.13%-16.38%, respectively. There was a significant difference in the mean density (individuals per 8 plants) of the most common predatory arthropod groups between different tobacco varieties fields, which was the highest in K326 field, followed by Nc82, and Nc89 field. The individuals of both Linyphiidae and Coccinellidae played the dominant role in the community. There was a significant difference in the richness of predatory arthropod community between Nc89 and Nc82 fields, but the differences of other structural characteristic indices were not significant. The temporal dynamics of the richness and dominancy in all test fields had a trend of low-high-low, and those of the diversity and evenness index were high-low-high.

Animals↗