Edited by Veronique Altglas and Matthew Wood
Véronique Altglas and Matthew Wood
Matthew V. Wood and T. Keith Philips
A unique new genus and species of spider beetle from Namaqualand from the Succulent Karoo Biodiversity Hotspot in South Africa is described. The genus Carinomezium gen. n. is characterized by pronounced longitudinal carinae on the elytra, four large rounded setal tufts that cover the pronotum, and the very small body size. The single representative species, Carinomezium namaquaensis sp. n. is diagnosed, described, and illustrated. The phylogenetic placement of this taxon is also discussed.
Bruno M. Ngala, Simon R. Woods and Matthew A. Back
The biofumigation potential of leaf and root extracts of Brassica juncea and Raphanus sativus on Globodera pallida were assessed in vitro. In an efficacy study, G. pallida encysted eggs were exposed to six different concentrations of freeze-dried leaf or root extracts for 96 h and assessed for viability using hatching assays in 6-week-old potato root leachates (PRL). For B. juncea extracts an LC50 value of 0.027 mg ml−1 w/v was determined. The LC50 of Raphanus sativus root extracts was 0.032 mg ml−1, whereas leaf extracts were effective only at higher concentrations (⩾0.50 mg ml−1; w/v) and to a lesser extent. Hatching of G. pallida was enhanced in PRL following exposure to lower concentrations (0.063 mg ml−1) of R. sativus leaf extract. An analysis of the types and concentrations of glucosinolate (GSL) present in the freeze-dried tissues revealed that B. juncea leaf tissue was rich in 2-propenyl GSL (≈98%). Root tissue also had a high concentration of 2-propenyl GSL, but the leaf extracts were found to have a higher concentration (⩾90 μmol (g dry weight)−1) when compared with the root extract (⩾10 μmol (g dry weight)−1). Raphanus sativus had two-fold more root GSL, predominantly 2-phenylethyl GSL (⩾50 μmol (g dry weight)−1), when compared with the leaf tissue which was dominated by 4-methylsulfinylbutyl GSL (⩾20 μmol (g dry weight)−1). In summary, the strong suppression of G. pallida encysted eggs exhibited by lower concentrations of B. juncea extracts shows the potential of this species in G. pallida management if effectively incorporated into an integrated potato cyst nematode management scheme. In comparison with B. juncea, the biofumigation potential of R. sativus can be improved by maximising its root biomass production.
Ben C. Sheldon, Dawn Burnham, Matthew S. Sullivan and Barry Stevens-Wood
In two experiments inspired by theories of sequential information-gathering tasks such as sequential mate assessment, human subjects were asked to view sequences of pictures of mythical birds, each of which varied in value according to one of three stimuli, namely tail length, band width or intensity of black and carried an associated score. The subjects chose one picture from the sequence so as to maximise their points scored. Only one picture could be seen at a time, if a picture was rejected it could not be revisited and there was a small constant devaluation of each successive picture. In the first experiment two random sequences of each of the three stimuli were viewed and subjects were given no prior information on the population of pictures, nor was the devaluation specified. In the second experiment, which used only pictures which varied in tail length, subjects cach saw a different random sequence and then the same fixed sequence. In addition, they were told there was either a 5%, 10% or 20% devaluation of succesive birds, and half the subjects were given prior information on the population to be viewed. Thus in this experiment scores could be corrected for position in the sequence. To summarise the major results: 1. Choice was made at an early stage in the sequence, usually the 3rd, 4th or 5th picture, and this was consistent in both experiments. 2. In Experiment 2, subjects given prior information or smaller devaluation functions chose later in the sequence. 3. In Experiment 2 there were no differences in the corrected scores achieved by subjects in our treatments of prior information or devaluation, but subjects achieved higher absolute scores as the devaluation decreased. 4. In both experiments the value of the chosen picture was positively correlated with the mean value of the prior sequence seen when absolute scores are used, but in Experiment 2 this effect disappears when corrected scores are used. 5. A large positive jump was a cue to stop in both the random and fixed sequences. Identification of relevant variables and patterns of decision making may further enlarge our understanding of sequential assessment in humans and other animal species.