An attempt to estimate the predatory pressure exerted by the lesser weever, Trachinus vipera Cuvier, in the southern North Sea

In order to evaluate the impact of the lesser weever on the ecosystem of the southern North Sea, geographical distribution, density, growth, production and food requirements have been estimated. High densities were found on and around the Brown Ridge, an area with high tidal current velocities, medium grain-size of the sediment and a poor benthic fauna. Growth is restricted to the months of June October. During the winter cessation of growth a considerable loss of weight (about 20%) takes place. Mortality has been estimated by using the average size frequency distribution of all catches made from 1972 to 1984. The resulting convex type of survival curve indicates a high survival rate of the II to IV-group fishes. The production (estimated with Allen's graphical method) of a population of 100 individuals including all age groups (0-VI) amounts to 123.7 g AFDW-year'. In areas with highest densities, consequently, production amounts to 0.018–0.078 g AFDW-m² -year^-1. With an assumed transfer efficiency of 10% through the year, food requirements amounts to 0.18–0.78 g AFDW-m ² -year ^-1. Since the lesser weever feeds mainly on fish (85.6%), almost exclusively on gobies (Pomatoschistus sp.), and with an assumed transfer efficiency of approximately 10%, the indirect predatory pressure exerted by it may amount to 1.6 6.7g AFDW-m ².year ^-1. A possible feeding by gobies on pelagic organisms (calanoids, mysids) is discussed.     

A simple simulation model of dispersal of animals among units of discrete habitats

Summary A simple simulation model of dispersal of animals among units of discrete habitats has been constructed. This model outputs the numbers of animals reaching each of twenty-five habitats at preselected loci in a grid under a variety of operating conditions. These conditions consist of variables controlling directionality, velocity and mortality during dispersal. The relationship between numbers of animals reaching a particular site and the distance of that site from the starting point was investigated. Similarly, the effects of directionality (as determined by the variance of the normal distribution used to assign directions of movement), mortality and velocity on the overall rate of success were studied. A negative exponential-type drop off in numbers of animals reaching a site was predicted with increasing distance from the starting point. The relationship between percent success, directionality and rate of mortality was predicted to be curvilinear; the percentage declining with decreased directionality and increased mortality. A positive linear relationship was indicated between the spatial displacement per iteration used and percent success.Wherever possible the assumptions and predictions of the model are compared with available data. The assumptions concerning initial and subsequent directions of movement were found to be borne out by the data examined as were the results showing the relationship between numbers at each site and distance from starting point. The other results of the simulations were more difficult to compare with available data and some of these remain to be tested.The advantages and disadvantages of the model and the prospects for its expansion are discussed. It is concluded that the model is simplistic but that this gives it a generality and versatility which make it a useful tool for further thinking and investigation on the process of dispersal.     

Tidal rhythms in activity in the intertidal gastropodPolinices incei (Philippi)

When removed into the laboratory, the intertidal snailPolinices incei, retains a tidal rhythm in activity for several days when maintained under conditions of constant light. There is, in addition, a gradual decline in activity following collection and a batch to batch effect of some note. When a 12∶12 light regime is maintained there is apparent also a c. 24 h rhythm in activity which may supercede the tidal one under some circumstances. The simplest explanation of the results is that there exist both tidal and diel rhythms. These results are compared with those observed by others for a variety of marine organisms, the adaptiveness of the behaviour pattern is discussed, and the implications of the work for further behavioural studies is explored.     

A molecular phylogeny of the hawkmoth genus Hyles (Lepidoptera: Sphingidae, Macroglossinae)

The hawkmoth genus Hyles is one of 15 genera in the subtribe Choerocampina of the subfamily Macroglossinae. Due to a remarkable uniformity, morphological characters usually used to identify and classify Lepidoptera at the species level cannot be used in this genus. Instead, we used DNA sequences comprising about 2300 bp derived from the mitochondrial genes COX I, COX II, and tRNA-leucine to elucidate the phylogeny of Hyles. The results corroborate the monophyly of Hyles but conflict with previous internal classifications of the genus based on morphology. Hyles seems to have evolved in the Neotropics during the Oligocene/Eocene epochs and the molecular data (which evolved clock-like) confirm the hypothesis that it is a very young genus that radiated on a global scale rather quickly. We hypothesize its sister group to be one of the genera Deilephila, Theretra or Xylophanes. The Nearctic may have been colonized rapidly by Hyles once the land bridge formed during the Pliocene, since within this same Epoch, the invasion of the Palaearctic appears to have proceeded from the East, via the Bering route. The colonization of Australia appears to have occurred rather early in Hyles radiation, although the route is not clear. We propose that the radiation of the Hyles euphorbiae-complex s. str. (HEC) occurred as recently as the Pliocene/Pleistocene boundary and that its roots can still be reconstructed in Asia. Hyles dahlii is closely related to the HEC, but a sister group relationship to the HEC s. str. cannot be corroborated unequivocally. HEC population ranges appear to have tracked climate oscillations during the Pleistocene Ice Ages, resulting in hybridization around the Mediterranean Sea as they repeatedly intermingled. Comparison of the phylogeny with food plant affiliations leads us to hypothesize that Euphorbia monophagy evolved at least two times independently within Hyles.     

An IL-12-independent role for CD40-CD154 in mediating effector responses: studies in cell-mediated glomerulonephritis and dermal delayed-type hypersensitivity

Crescentic glomerulonephritis (GN) results from IL-12-driven Th1-directed cell-mediated responses (akin to delayed-type hypersensitivity (DTH)) directed against glomerular Ags. CD40-CD154 interactions are critical for IL-12 production and Th1 polarization of immune responses. Crescentic anti-glomerular basement membrane GN was induced in C57BL/6 (wild-type (WT)) mice (sensitized to sheep globulin) by planting this Ag (as sheep anti-mouse glomerular basement membrane globulin) in their glomeruli. Crescentic GN did not develop in CD40(-/-) mice due to significantly reduced nephritogenic Th1 responses. IL-12 was administered to CD40(-/-) mice with GN to dissect interactions between IL-12 and CD40 in inducing nephritogenic immunity and injury. Administration of IL-12 to CD40(-/-) mice restored Th cell IFN-gamma production, and up-regulated intrarenal chemokines and glomerular T cell and macrophage accumulation compared with WT control mice. Despite this, renal macrophages were not activated and renal injury and dermal DTH were not restored. Thus, CD40-directed IL-12 drives Th1 generation and effector cell recruitment but CD40 is required for activation. To test this hypothesis, activated OT-II OVA-specific CD4(+) cells and OVA(323-339)-loaded nonresponsive APCs were transferred into footpads of WT, CD40(-/-), and macrophage-depleted WT mice. WT mice developed significant DTH compared with CD40(-/-) and macrophage-depleted WT mice. This study demonstrated that CD40-induced IL-12 is required for generation of systemic Th1 immunity to nephritogenic Ags, and that IL-12 enhances Th1 effector cell recruitment to peripheral sites of Ag presentation via generation of local chemokines. Effector cell activation, renal DTH-like injury, and dermal DTH require direct Th1 CD154/macrophage CD40 interactions.     

Elevational turnover in the composition of leaf miners and their interactions with host plants in Australian subtropical rainforest

Leaf miners are specialist herbivorous insects that are potentially vulnerable to environmental change because of their dependency on particular host plants. Little, however, is known about how climate affects the distribution of leaf miner communities and their interactions with host plants. Elevational gradients are useful tools for understanding how ecological communities respond to local clines in climate. Given that plant communities are known to undergo elevational turnover in response to changes in climatic conditions, we expect that leaf miner species will also change with elevation. We repeatedly hand collected leaf miners along three elevational gradients in subtropical rainforest in eastern Australia. Individual leaf miners were counted and identified to species, and their host plants were recorded. We tested if leaf miner species richness and the number of unique interactions among leaf miner and host plant species were affected by elevation. We also tested if the composition of leaf miner species and the composition of interactions between leaf miners and host plants showed a relationship with elevation. The rarefied number of unique leaf miner–host plant interactions significantly decreased with elevation, with a slight peak at approx. 700 m a.s.l., while neither rarefied or observed species richness (species density) of leaf miners nor observed numbers of unique interactions (interaction density) were significantly affected by elevation. The composition of leaf miner species and the composition of leaf miner–host plant interactions (occurrence of pairwise interactions) were significantly related to elevation. Elevational turnover in leaf miner species composition indicated that different species varied in their response to changes in biotic and/or abiotic conditions imposed by increasing elevation. Through our analyses, we identified four leaf miner species that may be locally vulnerable to climate change, as a result of their restricted elevational distribution and level of host specificity.