Effects of the herbicide paraquat on the ecology of a reservoir

Toxicity experiments indicated that changes in the fauna following the use of paraquat for weed control were likely to be indirect effects caused by the death and destruction of angiosperms. Generally, invertebrates living amongst the emergent vegetation in the margins of the reservoir and on the sediments were unaffected though the density of the benthic ostracod Cypridopsis vidua increased rapidly after the death of angiosperms. Of the planktonic invertebrates, those which were generally closely associated with the macrophytes were eliminated or survived at lower densities. Many of the invertebrates intimately associated with the angiosperms (e.g. Lepidoptera, Tricho-ptera. Gastropoda) were lost completely or colonized the replacement growth of Chara globularis at reduced densities: these effects were extended to the year after treatment. A few species colonizing Chara were able to establish densities comparable with those found on the angiosperms in the pre-herbicide period but in some cases the time of peak density was delayed. Data from fish gut analyses indicated that there was a change in the diet of the eel following the death of the angiosperms and that this was largely a reflection of the loss, or reduction in density, of many invertebrates associated with the angiosperms.     

Dispersed cuticles of putative non-vascular plants from the Lower Devonian of Britain

Dispersed cuticles with surface ornamentation recovered from the Lower Old Red Sandstone (Gedinnian) of Hereford and Worcester, England, are described, named and placed in an artificial, morphologically based classification system. Four species of the new genus Cosmochlaina are distinguished on the nature of the ornament. The affinities of the plants covered by such cuticles remain unknown: the cuticles are named to facilitate their use in biogeographic, stratigraphic and evolutionary studies.     

Changes in food selection by workers of the pharaoh''s ant, Monomorium pharaonis

The results from simple choice test experiments with laboratory and field colonies of pharaoh's ants have revealed two behavioural traits that influence the way in which foraging worker ants respond to foods. Initially, worker ants from laboratory colonies showed a distinct preference for certain foods (e.g. honey and peanut butter). However, when given only these 'preferred' foods continuously for several weeks, workers showed a marked preference for other foods when offered a choice. This 'satiation' response occurred even though the initial diet was originally highly attractive to foraging workers. In addition, workers show a marked tendency to alternate between carbohydrate foods and protein foods. Thus, workers from colonies fed predominantly on proteins, subsequently showed a marked preference for carbohydrates, and vice versa. The 'satiation' and 'alternation' responses to foods ensure that colonies receive a diet that is both varied and balanced. In addition, these aspects of feeding behaviour have important consequences for the use of food-based baits in control measures against Monomorium pharaonis (L.).