Developmental neuroethology: changes in escape and defensive behavior during growth of the lobster

The changes in relative efficacy of two incompatible behaviors was investigated during growth of the lobster, Homarus americanus. In larval and early juvenile stages, physiological and morphological factors favor use of the escape response over defensive behavior. In large animals, defensive behavior is preferred almost exclusively to escape behavior unless the claws are lost. The interaction of escape and defensive behavior is modified by neural and morphological factors, which are dependent on the stage in the life cycle of the organism.     

Environmental conditions at sea-cages, and ectoparasites on farmed European sea-bass, Dicentrarchus labrax (L.), and gilt-head sea-bream, Sparus aurata L., at two farms in Greece

Water quality in sea-cages, and metazoan ectoparasites on bass, Dicentrarchus labrax (L.), and bream, Sparus aurata L., were sampled at two fish farms in south-west Greece over 2 years. The seabed and marine life around the cages of one farm was surveyed using scuba. The most frequent and abundant parasites were the monogeans Sparicotyle chrysophrii and Furnestinia echeneis on the gills of bream, and Diplectanum aequans on the gills of bass. The copepod Caligus minimus occasionally occurred in the buccal cavity of bass, but only in low numbers. Prevalence and abundance of parasites increased with bass size but F echeneis levels decreased with bream size. There were no other clear relationships between water quality, parasite levels and fish size. Ammonia varied seasonally with sea temperature, and with oxygen levels below 6 mg 1^-1 on many occasions, it is possible that fish suffered stress from a combination of high ammonia and low oxygen conditions. There was no accumulation of waste food or faeces below the cages at the one farm surveyed, but there were thousands of wild fish, including mullet (Mugilidae), Spicara sp. and Diplodus spp., present around the cages. Water quality may be improved by changes in farm management, such as reducing stocking densities below the present 16 kg nr^-3. Oxygen should be monitored at the cages on site daily. How comparable environmental conditions and impacts, and parasitization are at other bass and bream sea cage farms is unknown.     

T cell activation by lipopeptide antigens

Unlike major histocompatibility proteins, which bind peptides, CD1 proteins display lipid antigens to T cells. Here, we report that CD1a presents a family of previously unknown lipopeptides from Mycobacterium tuberculosis, named didehydroxymycobactins because of their structural relation to mycobactin siderophores. T cell activation was mediated by the alphabeta T cell receptors and was specific for structure of the acyl and peptidic components of these antigens. These studies identify a means of intracellular pathogen detection and identify lipopeptides as a biochemical class of antigens for T cells, which, like conventional peptides, have a potential for marked structural diversity.     

Spatial relationship between Mycobacterium bovis strains in cattle and badgers in four areas in Ireland

We investigated whether strains (restriction fragment length polymorphism, RFLP-types) of Mycobacterium bovis isolated from badgers and from cattle clustered among and within four areas in Ireland. The spatial scan test and nearest-neighbor analysis were used as the spatial cluster-detection techniques. In addition, for each of the major strains, associations between the distance to badger setts and the "centroid" of the cattle farm were assessed in a logistic model. Overall, between September 1997 and May 2000, 316 and 287 M. bovis samples, from badgers and cattle, respectively, were strain-typed. The distribution of strains in badgers, and separately in cattle, differed among areas. Within each of the four large areas, badgers and cattle tended to have similar strains; this is consistent with the sharing of M. bovis strains within an area. In more detailed within-area analyses, some spatial clusters of M. bovis strains were detected, separately, in both cattle and badgers. Almost half of the infected badger setts with a specific strain were located outside of the "detected" clusters. There was no association between the number of infected badgers with a specific M. bovis strain within 2 or 5 km distances to cattle herds, and the risk of the same strain in cattle. We speculate about the dynamic nature of badger movements, as an explanation for the absence of more clusters of most of the strains of M. bovis isolated from badgers, and its impact on trying to study transmission of M. bovis between cattle and badger.     

The effect of the tuberculin test and the consequences of a delay in blood culture on the sensitivity of a gamma-interferon assay for the detection of Mycobacterium bovis infection in cattle

The strategic use of the gamma-interferon (IFN-gamma) assay (Bovigam) can provide a means for the early identification of Mycobacterium bovis infected cattle, thus ensuring their removal from an infected herd. It has been reported that performance of the test can be influenced by various factors including a recent tuberculin skin test and the length of delay between collection and processing of blood samples. In this study, single intradermal comparative tuberculin test (SICTT) reactor and non-reactor cattle were recruited from herds infected with M. bovis and grouped according to their SICTT responses. Group 1 comprised reactor cattle selected on the basis of their SICTT response to PPD-bovine (purified protein derivative of tuberculin) exceeding that of PPD-avian by at least 12mm. Group 2 animals were selected from herds undergoing routine surveillance for bovine tuberculosis and contained standard SICTT reactor cattle (PPD-bovine exceeding that of PPD-avian by at least 4mm) and non-reactors. We investigated the effects of the SICTT on the assay results by measuring the in vitro IFN-gamma responses of Group 1 reactor cattle at time intervals pre- and post-skin test. No significant differences were measured in the IFN-gamma responses of the reactor animals to PPD-bovine and PPD-avian for up to 65 days. To investigate if a delay in processing of blood affected the performance of the assay, we compared results using duplicate blood samples from Group 1 and Group 2 cattle stimulated with PPD antigen at 8h and at 24h after collection. In both groups of animals the mean optical density (OD) values of the assay at 24h post-collection were significantly lower than those at 8h. Our results demonstrated that a delay in processing of the blood samples from cattle subjected to routine surveillance could significantly impact on the outcome of the IFN-gamma assay resulting in a change of the IFN-gamma status of the animals.