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PubMed2006

[Structural characteristics of arthropod community in grapery].

By the method of principal component analysis, this paper analyzed the characteristic parameters of arthropod community and its phytophagous and predacious sub-communities in grapery. The results showed that in the first principal component, the contribution of arthropod community, phytophagous sub-community and predacious sub-community was 66.70%, 73.39% and 54.17%, respectively. For arthropod community, the absolute values of normalized regressive coefficients of individuals' number N, Hill diversity index N1, Hill diversity index N2 and McIntosh index D(mc) were larger, indicating their greater contribution on the community. For phytophagous sub-community, N, N1, N2, N and S (total species) had greater contribution; while for predacious sub-community, the greater contribution was made by N1, N2, Shannon-Wiener diversity index H' and abundance R. Synthetically, N2 and N1 had greater contribution on the arthropod community and its phytophagous and predacious sub-communities in grapery, comparing with other characteristic parameters.

Animals↗
PubMedDate not supplied

Importance of tropomyosin in the allergy to household arthropods. Cross-reactivity with other invertebrate extracts.

The aim of the study was to investigate the involvement of the actin binding protein tropomyosin in the allergic sensitization of patients to household arthropods, as well as to study its panallergenic character in relation to other invertebrate extracts. Three arthropod extracts were prepared, namely fly (Musca domestica), moth (Ephestia spp.) and spider (Tegenaria spp.), and used to evaluate by cutaneous and RAST tests a population of 100 household arthropod allergic patients. Twenty-nine sera were selected for the subsequent SDS-PAGE Immunoblotting assays. IgE binding bands at 36, 34, 31, 27 and 17 kDa were detected in the fly extract by more than 50% of tested sera. In moth and spider extracts, the more relevant allergens were found at 34, 31, 24 and 110, 38, 35, 26, 19 kDa, respectively. A commercial polyclonal antiserum anti-chicken muscle tropomyosin was used for tropomyosin identification. Cross-reactivity studies performed by SDS-PAGE Immunoblotting, using a pool of household arthropod allergic patients and tropomyosin antiserum, preliminarily demonstrated the presence of such protein as a cross-reacting allergen in a large variety of extracts obtained from insects, mites, crustaceans, mollusks and parasites.

Allergens↗
PubMed2000

Arthropods and Multispecies Habitat Conservation Plans: Are We Missing Something?

Arthropods constitute well over one-half of the species of higher life on the planet and are the dominant terrestrial life form on the planet. Unfortunately, very little is known about most arthropod species. There are an estimated 163,487 species of insects in North America, of which only 66% are taxonomically known. Similarly, there are an estimated 35,514 species of North American arachnids, of which only 9316 are described; over 73% have yet to be discovered and described. Without the basic taxonomic and life history knowledge for most of the terrestrial species (i.e., arthropods) of North American ecosystems, land managers are faced with the challenge of developing, selecting, and managing biotic reserves and habitat conservation plans for which they know very little about the majority of organisms found within such reserves or covered by such plans. With respect to arthropods, this challenge includes taking into account poorly described species being used as political tools to stop development (as opposed to actually protecting a truly endangered species), thus confounding the habitat conservation planning process and ensuring that "surprises" in the form of new listings will occur within any multispecies habitat plan. Finally, using various scenarios and assumptions, estimates of the true number of endangered insects and arachnids are provided to illustrate the fact that the suspected number of threatened, endangered, and extinct species is probably low by at least an order of magnitude.

Journal Article↗
PubMed2001

Double-stranded RNA interference in the spider Cupiennius salei: the role of Distal-less is evolutionarily conserved in arthropod appendage formation.

Chelicerates represent a basal arthropod group, which makes them an excellent system for the study of evolutionary processes in arthropods. To enable functional studies in chelicerates, we developed a double-stranded RNA-interference (RNAi) protocol for spiders while studying the function of the Distal-less gene. We isolated the Distal-less gene from the spider Cupiennius salei. Cs-Dll gene expression is first seen in cells of the prosomal segments before the outgrowth of the appendages. After the appendages have formed, Cs-Dll is expressed in the distal portion of the prosomal appendages, and in addition, in the labrum, in two pairs of opisthosmal (abdominal) limb buds, in the head region, and at the posterior-most end of the spider embryo. In embryos, in which Dll was silenced by RNAi, the distal part of the prosomal appendages was missing and the labrum was completely absent. Thus, Dll also plays a crucial role in labrum formation. However, the complete lack of labrum in RNAi embryos may point to a different nature of the labrum from the segmental appendages. Our data show that the expression of Dll in the appendages is conserved among arthropods, and furthermore that the role of Dll is evolutionarily conserved in the formation of segmental appendages in arthropods.

Animals↗
PubMed1996

Anticoagulants in vector arthropods.

Arthropod-borne diseases cause significant morbidity and mortality worldwide. Mosquitoes alone may account for as many as three million deaths annually via the transmission of malaria. Because these diseases are transmitted to humans and to other vertebrates as a result of the ability of arthropods to feed on blood, the study of the biochemical mechanisms and adaptations that arthropods have evolved to facilitate hematophagy may provide insight into how this feeding behavior contributes to the transmission of disease. In this review, Kenneth Stark and Anthony James examine the diversity of arthropod anticoagulants and their role in hematophagy and potential implications for parasite transmission.

Journal Article↗
PubMed2003

Arthropod-like expression patterns of engrailed and wingless in the annelid Platynereis dumerilii suggest a role in segment formation.

The origin of animal segmentation, the periodic repetition of anatomical structures along the anteroposterior axis, is a long-standing issue that has been recently revived by comparative developmental genetics. In particular, a similar extensive morphological segmentation (or metamerism) is commonly recognized in annelids and arthropods. Mostly based on this supposedly homologous segmentation, these phyla have been united for a long time into the clade Articulata. However, recent phylogenetic analysis dismissed the Articulata and thus challenged the segmentation homology hypothesis. Here, we report the expression patterns of genes orthologous to the arthropod segmentation genes engrailed and wingless in the annelid Platynereis dumerilii. In Platynereis, engrailed and wingless are expressed in continuous ectodermal stripes on either side of the segmental boundary before, during, and after its formation; this expression pattern suggests that these genes are involved in segment formation. The striking similarities of engrailed and wingless expressions in Platynereis and arthropods may be due to evolutionary convergence or common heritage. In agreement with similarities in segment ontogeny and morphological organization in arthropods and annelids, we interpret our results as molecular evidence of a segmented ancestor of protostomes.

Animals↗
PubMed1998

An experimental chain of infection reveals that distinct Borrelia burgdorferi populations are selected in arthropod and mammalian hosts.

The prokaryotic, spirochaetal microorganism Borrelia burgdorferi is the causative agent of Lyme disease, an arthropod-borne disease of a variety of vertebrates and the most prevalent arthropod-borne disease of humans in the United States. In order to understand better the normal life cycle of B. burgdorferi, an experimental chain of infection was devised that involved multiple sequential arthropod and mammalian passages. By examining populations of B. burgdorferi emerging from different points in this infectious chain, we demonstrate that selection of B. burgdorferi populations peculiar to arthropod or vertebrate hosts is a property of at least one of the two ecologically distinct strains we examined. Distinct B. burgdorferi populations were identified using an antigenic profile, defined by a set of monoclonal antibodies to eight B. burgdorferi antigens, and a plasmid profile, defined by the naturally occurring plasmids in the starting clonal populations. These two profiles constituted the phenotypical signature of the population. In the strain exhibiting selection in the different hosts, transition from one host to another produced a striking series of alternating phenotypical signatures down the chain of infection. At the molecular level, the alternating signatures were manifested as a reciprocal relationship between the expression of certain antigenic forms of outer surface protein (Osp) B and OspC. In the case of OspC, the antigenic changes could be correlated to the presence of one of two distinctly different alleles of the ospC gene in a full-length and presumably transcriptionally active state. In the case of OspB, two alleles were again identified. However, their differences were minor and their relationship to OspB antigenic variation more complicated. In addition to the reciprocating changes in the antigenic profile, a reciprocating change in the size (probably the multimeric state) of a 9.0 kbp supercoiled plasmid was also noted. Selection of distinct populations in the tick may be responsible for the microorganism's ability to infect a wide range of vertebrate hosts efficiently, in that the tick might provide selective pressure for the elimination of the population selected in the previous host.

Amino Acid Sequence↗
PubMed2004

Formicine ants: An arthropod source for the pumiliotoxin alkaloids of dendrobatid poison frogs.

A remarkable diversity of bioactive lipophilic alkaloids is present in the skin of poison frogs and toads worldwide. Originally discovered in neotropical dendrobatid frogs, these alkaloids are now known from mantellid frogs of Madagascar, certain myobatrachid frogs of Australia, and certain bufonid toads of South America. Presumably serving as a passive chemical defense, these alkaloids appear to be sequestered from a variety of alkaloid-containing arthropods. The pumiliotoxins represent a major, widespread, group of alkaloids that are found in virtually all anurans that are chemically defended by the presence of lipophilic alkaloids. Identifying an arthropod source for these alkaloids has been a considerable challenge for chemical ecologists. However, an extensive collection of neotropical forest arthropods has now revealed a putative arthropod source of the pumiliotoxins. Here we report on the presence of pumiliotoxins in formicine ants of the genera Brachymyrmex and Paratrechina, as well as the presence of these ants in the stomach contents of the microsympatric pumiliotoxin-containing dendrobatid frog, Dendrobates pumilio. These pumiliotoxins are major alkaloids in D. pumilio, and Brachymyrmex and Paratrechina ants now represent the only known dietary sources of these toxic alkaloids. These findings further support the significance of ant-specialization and alkaloid sequestration in the evolution of bright warning coloration in poison frogs and toads.

Alkaloids↗
PubMed1998

A conserved mode of head segmentation in arthropods revealed by the expression pattern of Hox genes in a spider.

Chelicerates constitute a basic arthropod group with fossil representatives from as early as the Cambrian period. Embryonic development and the subdivision of the segmented body region into a prosoma and an opisthosoma are very similar in all extant chelicerates. The mode of head segmentation, however, has long been controversial. Although all other arthropod groups show a subdivision of the head region into six segments, the chelicerates are thought to have the first antennal segment missing. To examine this problem on a molecular level, we have compared the expression pattern of Hox genes in the spider Cupiennius salei with the pattern known from insects. Surprisingly, we find that the anterior expression borders of the Hox genes are in the same register and the same relative segmental position as in Drosophila. This contradicts the view that the homologue of the first antennal segment is absent in the spider. Instead, our data suggest that the cheliceral segment is homologous to the first antennal segment and the pedipalpal segment is homologous to the second antennal (or intercalary) segment in arthropods. Our finding implies that chelicerates, myriapods, crustaceans, and insects share a single mode of head segmentation, reinforcing the argument for a monophyletic origin of the arthropods.

Animals↗
PubMed2000

Expression patterns of hairy, even-skipped, and runt in the spider Cupiennius salei imply that these genes were segmentation genes in a basal arthropod.

There is an ongoing discussion on whether segmentation in different phyla has a common origin sharing a common genetic program. However, before comparing segmentation between phyla, it is necessary to identify the ancestral condition within each phylum. Even within the arthropods it is not clear which parts of the genetic network leading to segmentation are conserved in all groups. In this paper, we analyze the expression of three segmentation genes of the pair-rule class in the spider Cupiennius salei. Spiders are representatives of the Chelicerata, a monophyletic basic arthropod group. We find that in spider embryos, the orthologues for the Drosophila primary pair-rule genes hairy, even-skipped, and runt are expressed in stripes in the growth zone, where the segments are forming, suggesting a role for these genes in chelicerate segmentation. These data imply that the involvement of hairy, even-skipped, and runt in arthropod segmentation is an ancestral character for arthropods and is not restricted to a particular group of insects.

Animals↗
PubMed1992

Evidence from 12S ribosomal RNA sequences that onychophorans are modified arthropods.

The evolutionary relationships of the onychophorans (velvet worms) and the monophyly of the arthropods have generated considerable debate. Cladistic analyses of 12S ribosomal RNA sequences indicate that arthropods are monophyletic and include the onychophorans. Maximum parsimony analyses and monophyly testing within arthropods indicate that myriapods (millipedes and centipedes) form a sister group to all other assemblages, whereas crustaceans (shrimps and lobsters) plus hexapods (insects and allied groups) form a well-supported monophyletic group. Parsimony analysis further suggests that onychophorans form a sister group to chelicerates (spiders and scorpions) and crustaceans plus hexapods, but this relationship is not well supported by monophyly testing. These relationships conflict with current hypotheses of evolutionary pathways within arthropods.

Animals↗
PubMed1984

Blood leukocyte response in hosts parasitized by the hematophagous arthropods Triatoma protracta and Lutzomyia longipalpis.

The kinetics of peripheral blood basophil and eosinophil responses in guinea pigs to multiple infestation by nymphal and adult Triatoma protracta (vessel feeder) and adult Lutzomyia longipalpis (pool feeder) were examined. Hosts exhibited significant blood basophil and eosinophil responses to feeding by both arthropods. Basophilia was slow to develop and mild in intensity following primary Triatoma infestation but exhibited immediate anamnestic-type responses to secondary infestation, with marked but delayed-type responses to tertiary infestation. Basophilia developed quickly in guinea pigs infested with Lutzomyia, and this response remained fairly consistent throughout the three infestation periods. Eosinophils did not respond to primary Triatoma infestation but exhibited marked immediate responses to both secondary and tertiary infestations. Lutzomyia-infested hosts exhibited marked eosinophilia in response to all infestations. Eosinophil levels returned to control levels 10 days post-tertiary infestation in Triatoma hosts, whereas Lutzomyia hosts exhibited normal eosinophil levels within 3-4 days after peak response. This study demonstrates that hosts respond to fast-feeding hematophagous arthropods with a peripheral blood basophilia and eosinophilia, as reported for slow-feeding (ticks) hematophagous arthropods. The difference in feeding strategy, whether vessel or pool feeder, appears to be reflected by differences in host blood leukocyte kinetics in response to parasitization by specific arthropods.

Animals↗
PubMed2003

Antimicrobial and cytolytic peptides of venomous arthropods.

As a response to invading microorganisms, the innate immune system of arthropods has evolved a complex arrangement of constitutive and inducible antimicrobial peptides that immediately destroy a large variety of pathogens. At the same time, venomous arthropods have developed an additional offensive system in their venom glands to subdue their prey items. In this complex venom system, several enzymes, low-molecular-mass compounds, neurotoxins, antimicrobial and cytolytic peptides interact together, resulting in extremely rapid immobilization and/or killing of prey or aggressors. This review provides an overview of antimicrobial peptides identified in the hemolymph of venomous arthropods, and especially of cytolytic peptides in their venom. For these peptides a dual role is proposed: acting as antimicrobials as well as increasing the potency of the venom by influencing excitable cells.

Animals↗
PubMed1997

Ecological implications of control strategies: arthropods of domestic and production animals.

The control of arthropods of veterinary importance represents a disturbance for the ecosystem and its animal community. This disturbance can influence the densities of target and non-target organisms and their associated indirect interactions in the food web, leading to reductions in the species richness and diversities in the communities involved. Finely tuned control affecting the target organism alone can have unexpected consequences, depending on the relationships between the target and other organisms within the food web. Broad-spectrum control methods will have more wide ranging and less predictable consequences. Modifications within the community caused by arthropod control can take place over generations and may not be immediately apparent. Most modern techniques of control are designed to minimize environmental impact by concentrating specifically on the target organism. The effects of control of arthropod pests of domestic and production stock must be seen against a background of more general effects caused by rural development which acts to modify the environment continuously over a long time span.

Animals↗
PubMed1999

Mechanisms of arthropod transmission of plant and animal viruses.

A majority of the plant-infecting viruses and many of the animal-infecting viruses are dependent upon arthropod vectors for transmission between hosts and/or as alternative hosts. The viruses have evolved specific associations with their vectors, and we are beginning to understand the underlying mechanisms that regulate the virus transmission process. A majority of plant viruses are carried on the cuticle lining of a vector's mouthparts or foregut. This initially appeared to be simple mechanical contamination, but it is now known to be a biologically complex interaction between specific virus proteins and as yet unidentified vector cuticle-associated compounds. Numerous other plant viruses and the majority of animal viruses are carried within the body of the vector. These viruses have evolved specific mechanisms to enable them to be transported through multiple tissues and to evade vector defenses. In response, vector species have evolved so that not all individuals within a species are susceptible to virus infection or can serve as a competent vector. Not only are the virus components of the transmission process being identified, but also the genetic and physiological components of the vectors which determine their ability to be used successfully by the virus are being elucidated. The mechanisms of arthropod-virus associations are many and complex, but common themes are beginning to emerge which may allow the development of novel strategies to ultimately control epidemics caused by arthropod-borne viruses.

Animals↗
PubMedDate not supplied

Bacterial symbiosis in arthropods and the control of disease transmission.

Bacterial symbionts may be used as vehicles for expressing foreign genes in arthropods. Expression of selected genes can render an arthropod incapable of transmitting a second microorganism that is pathogenic for humans and is an alternative approach to the control of arthropod-borne diseases. We discuss the rationale for this alternative approach, its potential applications and limitations, and the regulatory concerns that may arise from its use in interrupting disease transmission in humans and animals.

Animals↗
PubMed1994

Vaccines against arthropods.

The possibility of vaccinating hosts against blood-feeding arthropods using antigens derived from salivary gland, gut, and other tissues is reviewed. These vaccines directed against vector arthropods also have the potential to effect the arthropods capacity to transmit pathogens, and this is distinct from transmission-blocking vaccines that use antigens derived from pathogens. Antigen extracts have been used in attempts to vaccinate against fleas, lice, keds, flies, mosquitoes, and a number of tick species. A vaccine against the cattle tick, Boophilus microplus (Canestrini), using a recombinant antigen, has been tested under field conditions. Ticks feeding on vaccinated hosts are damaged by an immune response directed against their gut cells. Some die on the host, others engorge but their fecundity is reduced. The Commonwealth Scientific Industrial Research Organization-Biotechnology Australia tick vaccine against B. microplus is cited as a model for the development of other vaccines. It is suggested that the weaker effects of vaccines against insects as compared with ticks are related to the different structure and physiologies of the gut rather than being related to time spent on the vertebrate host. These differences in the effects of vaccines on insects may favor vaccines which block the passage of pathogens into vector insects. Vaccines against mosquitoes have been shown to reduce susceptibility of mosquitoes to arboviruses. The potential of the different vaccines is discussed.

Animals↗
PubMed2004

A survey of the relationships among the viruses not considered arboviruses, vertebrates, and arthropods.

No single group of organisms demonstrates more extensive and diverse associations with animal viruses than the phylum Arthropoda. Compared with the well-recognized relationship found in arboviruses, however, most of the atypical arthropod-vertebrate relationships of the viruses normally not considered arboviruses have received much less attention, as they remain in the marginal areas of interest for most researchers in animal virology, veterinary medicine, medical entomology, and invertebrate pathology. However, this comprehensive review of the information gathered from several branches of virology by profession reveals highly valuable information potentially useful in the fields of research ranging from investigations of the mode of transmission of poorly understood or emerging viral diseases to studies of the evolution of biological transmission of animal viruses by arthropod vectors. The observations and data obtained for the animal virus relationships with arthropods and vertebrates outside the boundaries of arboviruses, in turn, can be used to reexamine more closely the definition of arboviruses. With increasing number of reports challenging one of the basic tenets of the definition of arbovirus (requirement of viremia in vertebrate host) and others describing virus-host relationships that complicate the definition of arbovirus, the accumulated information clearly demonstrates the difficulty of defining the boundaries of arboviruses.

Animals↗