Chemical Defence

Temporal variation is one of the least known components of defence production in marine organisms. Here we examined whether there is a predictable temporal pattern in the production of chemical and structural defences by a marine invertebrate. To assess the seasonal variation in chemical defence, we measured ascididemin, the main pyridoacridine alkaloid in the blue Mediterranean morph of the ascidian Cystodytes sp. Structural defence variability was assessed on the basis of colony ash content, as it contains mainly spicules. Ascididemin concentration and the colony ash content displayed an annual cycle, reaching a minimum in spring and peaking in summer. Cross-correlation analyses with existing data on growth and reproduction suggested a significant trade-off between investment in reproduction and the other biological parameters considered (growth, inorganic content and ascididemin concentration). Our results suggest that optimization of resource allocation, probably influenced by biotic interactions and physical factors, shaped the temporal trends observed in secondary metabolite concentration and inorganic content.

The rutaceous tree Zanthoxylum myriacanthum is a 'nonspecific' myrmecophyte that offers food via extrafloral nectaries (EFN) as well as nesting space for ants inside its hollow branches and twigs. A total of 33 different species of ants from 4 subfamilies were recorded on the tree. Twenty-eight (85%) of these species were found nesting inside the domatia. None of these stem-nesting ant species appears to be a specialist occupant of Z. myriacanthum. Most of the nesting ant species showed no or little degree of effectiveness in anti-herbivore protection when loss of leaf area of inhabited branches is compared with those of uninhabited branches (the EFN of the latter still being accessible for ant visitors). For one ant species we could demonstrate a highly significant reduction of leaf area loss. The outcome of ant colonization on Z. myriacanthum will likely be diffuse because ant partners can vary markedly in space and time. In addition to biotic defence the tree also invests...

... For example, compartmentation and the formation of complexes with phenol derivatives in the vacuole may be another example of the mechanisms of resistance to heavy metals (Larcher, 1995; Tong, Kneer, & ... (79:20:1) solution for 20 min (Markham, 1982; Nawa, Asano, Motoori ...

Stick and leaf insects (Phasmida) representing 19 species (53 individuals) were collected in a lowland dipterocarp forest (Lambir Hills, Sarawak, Malaysia). Dual-choice tests were conducted to examine whether phasmids discriminate between young and old leaves of seven plant species. A second set of tests examined the preferences of phasmids for leaves from Dryobalanops lanceolata (Dipterocarpaceae) saplings versus leaves from the