Gammarus spp. are widespread throughout a diverse range of freshwater habitats and can be the dominant part of many benthic macroinvertebrate assemblages, in terms of both numbers and/or biomass. Although the vast majority of studies have emphasized the herbivorous nature of Gammarus spp. and their ‘shredder’ functional feeding group (FFG) classification, we show that a far wider food base is exploited than has been previously acknowledged. This ‘plasticity’ as herbivore/predator is linked to the success of Gammarus spp. in persisting in and colonizing/invading disturbance-prone ecosystems. Intraguild predation and cannibalism are more common than previously realized. This behaviour appears to be a causal mechanism in many amphipod species replacements. Additionally, Gammarus spp. are major predators of other members of the macroinvertebrate community. Furthermore, while many studies have emphasized fish predation on Gammarus spp., we illustrate how this fish[ratio ]amphipod, predator[ratio ]prey interaction may be a two-way process, with Gammarus spp. themselves preying upon juvenile and wounded/trapped fish. We urge that a new realism be adopted towards the trophic ecology of Gammarus spp. and their role as predators and prey and that previously established FFG assumptions of both the food and the feeder be questioned critically.

Amphibians occupy a wide range of habitat types from arid deserts to deep freshwater lakes; they may spend most of their life underground or high in cloud forest canopy. Some are found north of the Arctic Circle and can tolerate freezing conditions, while others have evolved a range of adaptations to avoid desiccation in some of the hotter areas of the world. The skin plays key roles in the everyday survival of amphibians and their ability to exploit a wide range of habitats and ecological conditions. The normal functions of the skin are surveyed and Eisner's biorational approach to chemical prospecting – seeking clues from an animal's behaviour and its interactions with its environment to reveal the presence of chemical compounds with potential medical or veterinary applications – is applied to amphibians. The biology and natural history of amphibian skin, its glands and their secretions are briefly reviewed. Four categories of compounds are found in the granular or poison glands, these are: biogenic amines, bufodienolides (bufogenins), alkaloids and steroids, peptides and proteins. Toads, particularly members of the genus Bufo, are identified as a particularly convenient and useful source of granular gland secretions. The potential medical-pharmaceutical significance of products derived from amphibian skin secretions is discussed. The need for a humane approach to this work is noted.

Once the inoculum of B. cinerea comes into contact with the host and starts to be active in the phyllosphere of a susceptible host tissue, a series of events take place. These events may develop into a process that leads to necrosis of the host, or may end in an arrested infection with minimal damage to the host tissue. Increased susceptibility to the pathogen is associated with factors that enhance ageing of the host tissues, such as the plant hormones ethylene and abscisic acid and elevation of free radical levels in the host tissue. Decreased susceptibility is obtained by inhibiting the production or activity of such factors in the presence of increased levels of plant hormones such as gibberellic acid, and by increasing the calcium content of the cell walls and by scavenging of free radicals in the host tissue. There is evidence for the induction of resistance in hosts affected by B. cinerea. Host tissues challenged by B. cinerea react at the DNA, RNA and protein level and accumulate pathogenicity related proteins, phytoalexins or other phenolic compounds. Deposition of polymers in cell walls and lignification have also been recorded in various hosts. The role of each of these factors in relation to protection is not clear. Moreover, some of the phenomena may occur too late to protect the host tissue against infection. Although the inhibition of specific proteins such as polygalacturonases has been suggested as a mechanism by which to inhibit disease, it is unlikely that the inhibition of one enzyme, would lead to significant restriction of infection. However, simultaneous inhibition of several hydrolytic enzymes produced by the pathogen should result in disease suppression. Possibilities of reducing the susceptibility of hosts or arresting further development of localized infections are discussed.

Previous phylogenetic analyses of caecilian neuroanatomical data yield results that are difficult to reconcile with those based upon more traditional morphological and molecular data. A review of the literature reveals problems in both the analyses and the data upon which the analyses were based. Revision of the neuroanatomical data resolves some, but not all, of these problems and yields a data set that, based on comparative measures of data quality, appears to represent some improvement over previous treatments. An extended data set of more traditional primarily morphological data is developed to facilitate the evaluation of caecilian relationships and the quality and utility of neuroanatomical and more traditional data. Separate and combined analyses of the neuroanatomical and traditional data produce a variety of results dependent upon character weighting, with little congruence among the results of the separate analyses and little support for relationships among the ‘higher’ caecilians with the combined data. Randomization tests indicate that: (1) there is significantly less incompatibility within each data set than that expected by chance alone; (2) the between-data-set incompatibility is significantly greater than that expected for random partitions of characters so the two data sets are significantly heterogeneous; (3) the neuroanatomical data appear generally of lower quality than the traditional data; (4) the neuroanatomical data are more compatible with the traditional data than are phylogenetically uninformative data. The lower quality of the neuroanatomical data may reflect small sample sizes. In addition, a subset of the neuroanatomical characters supports an unconventional grouping of all those caecilians with the most rudimentary eyes, which may reflect concerted homoplasy. Although the neuroanatomical data may be of lower quality than the traditional data, their compatibility with the traditional data suggests that they cannot be dismissed as phylogenetically meaningless. Conclusions on caecilian relationships are constrained by the conflict between the neuroanatomical and traditional data, the sensitivity of the combined analyses to weighting schemes, and by the limited support for the majority of groups in the majority of the analyses. Those hypotheses that are well supported are uncontroversial, although some have not been tested previously by numerical phylogenetic analyses. However, the data do not justify an hypothesis of ‘higher’ caecilian phylogeny that is both well resolved and well supported.