Competition For Attachment Sites Research Articles

Variation in the attachment sites of ticks to Australian lizards

Abstract A number of species of reptile ticks in Australia, particularly those using the sleepy lizard (Trachydosaurus rugosus) as their dominant host, form parapatric boundaries wherever they come into contact. A variety of hypotheses have been put forward to explain these boundaries, none of which has yet been demonstrated to be correct. Two of these, one involving reproductive interference and the other competition for attachment sites to hosts, were based on field observations of differences in attachment sites between species and regional variation in attachment sites within species. These hypotheses assume that species-specific attachment site preferences are static. Here we show, using data from single-species infestations of T. rugosus, that this is not the case for either Aponomma hydrosauri males or Amblyomma albolimbatum males or females. We suggest that dynamics in attachment site choice are driven, at least in part, by male movement in search of females.

Specificity of attachment sites of larval water mites (Hydrachnidia, Acari) on their insect hosts (Chironomidae, Diptera) – evidence from some stream-living species

This study concerns the parasite-host associations of water mite larvae and their chironomid hosts in a small stream on the North German Plain. The different feeding sites on the host were tested as to whether they represented a strategy of the parasites regarding host partitioning. The attachment sites of nine ectoparasitic water mite species were observed in detail: Aturus fontinalis, Atractides nodipalpis, Feltria rouxi, Hygrobates nigromaculatus, Protzia eximia, Sperchonopsis verrucosa, Sperchon clupeifer, S. setiger and Lebertia inaequalis. Aturus fontinalis, A. nodipalpis, F. rouxi and H. nigromaculatus distinctly preferred sites on the abdomen of the host, whereas the other species preferred feeding sites on the thorax. The four species that preferentially attached to the abdomen of the host showed a distinct specificity for selected segmental and/or intersegmental regions. All species differed in their sites along the length of the abdomen. The order of attachment on the abdominal segments was, from anterior to posterior: H. nigromaculatus, F. rouxi, A. fontinalis and A. nodipalpis. The sites were analysed with regard to segmental and intersegmental attachment, the proportion of dorsal and ventral sites and the differences between attachment to different host species. Larvae attached to their hosts as single individuals showed only slight differences from the sites of mites on hosts that carried many mite larvae. The finding that less than 10% of the chironomids were parasitized by more than one water mite species suggested that, at least in the zoocoenosis of the studied collecting site, the interspecific competition for attachment sites was not strong. However, the specificity of attachment sites clearly had the potential of diminishing competition between water mite species by host partitioning. Intra- and interspecific competition for preferred sites and preparasitic constraints are discussed.

Biological Control of Grape Crown Gall by Strain F2/5 Is Not Associated with Agrocin Production or Competition for Attachment Sites on Grape Cells

ABSTRACT Agrocin-minus mutants of nontumorigenic Agrobacterium vitis strain F2/5 controlled grape crown gall as well as the wild-type strain, indicating that agrocin is not a major factor in the mechanism of biological control. Relative levels of attachment to grape cells by tumorigenic and biocontrol strains were also measured. Attachment of tumorigenic strains (CG49 and K306) and biological control strains (F2/5 and agrocin-minus mutant 1077) was often reduced when mixtures of the strains were applied. However, high populations (10(3) to 10(5) CFU/ml) of all strains attached following mixed inoculations, suggesting that competition for attachment sites is also not a factor in the mechanism of biological control. Transfer of T-DNA to grape by CG49 was prevented or greatly inhibited in the presence of F2/5 or 1077 as measured by expression of the GUS reporter gene. The Ti plasmid virulence genes, however, were induced by exudates from grape shoots that had been inoculated with F2/5. Sonicated and autoclaved preparations of F2/5 and 1077 did not control crown gall or inhibit T-DNA transfer. Control by F2/5 is specific to grape, since gall formation on tomato, sunflower, and Kalanchoe daigremontiana were not inhibited.

Interactions among microorganisms of the indigenous intestinal flora and their influence on the host.

The animal host and its intestinal microbial flora function together as a complex ecologic system in which there is a significant impact of the intestinal flora on the host as well as of components of the microbial flora on one another. Aerobic and anaerobic bacteria of the intestinal flora influence numerous anatomic, physiologic, and immunologic parameters of the host. Constituents of the indigenous intestinal flora also engage in a multitude of antagonistic and cooperative interactions. The normal bacterial intestinal flora represents an extremely important defense mechanism, which effectively interferes with the establishment of many important enteric pathogens. Mechanisms by which microorganisms suppress the growth of other microorganisms include modification of bile acids, stimulation of peristalsis, induction of immunologic responses, depletion of essential substrates from the environment, competition for attachment sites, creation of restrictive physiologic environments, and elaboration of antibiotic-like substances. Components of the intestinal microbial flora also interact synergistically in the induction of disease or the utilization of substrate.

Resource Partitioning in Species of the Water Mite Genus Eylais

Resource partitioning was studied in 20 species of the water mite genus Eylais, the larvae of which parasitize adult Coleoptera and Hemiptera living in shallow ponds. Co—existence of sympatric species is possible because the mites exploit host resources in different ways. Most commonly they parasitize different species, but when hosts are identical, the mites remain segregated by differences in the precise site of attachment, biotope, or season of parasitism. Mite biology, host dispersal, and competition for attachment sites from other water mite species may restrict further subdivision of host resources.