Cadmium in freshwaters: concentrations and chemistry

SUMMARY. 1. Concentrations of cadmium are reported for twenty largely unpolluted freshwaters in north-western England. They range from 15 to 117 ng l⁻¹ total Cd in the rivers and streams and from 18to51 ng l⁻¹ in the lakes, lying on the low side of values reported in the literature. The care required to obtain reliable data is stressed.
2. A comparison is made between the fraction of Cd found to be particulate (>0.2 μm) and that which is calculated to be adsorbed on particulate matter. This provides further insight into the speciation of Cd, as well as a test of the application of a simple adsorption model to the prediction of the observed speciation.
3.The adsorption model is found to be a poor predictor of the measured fraction of particulate Cd. Possible reasons for this are explored and the potentially important role of slow desorption kinetics is emphasized.     

Remodelling of Neuromuscular Systems During Insect Metamorphosis

During metamorphosis in the hawkmoth, Manduca sexta, the larvalthoracic legs are replaced by a new set of adult legs that includenew sensory neurons and muscles, and participate in new patternsof locomotor activity. Larval leg motoneurons persist to innervatethe new adult leg muscles, but undergo striking changes in dendriticmorphology that are regulated by the insect steroid, 20-hydroxyecdysone.In the periphery, the motor terminals regress as larval musclesdegenerate, and expand as new adult muscles form from myoblasts.Evidence obtained both in vivo and in vitro suggests that theproliferation of myoblasts during metamorphosis is dependentupon innervation.     

A comparison of habitat use, morphology, clinging performance and escape behaviour among two divergent green anole lizard (Anolis carolinensis) populations

We measured available and actual habitat use, morphology, escape behaviour and clinging ability in a large sample ( N  = 242) of green anoles, Anolis carolinensis , in a habitat consisting primarily of segregated dense clumps of broad leaves, Aspidistra elatior (Tulane University campus, LA) to compare against similar data collected previously from a more typical habitat c. 30 km away, consisting of continuous strands of bushes and trees (Good Hope Field, St. Charles Parish, LA). At Tulane the anoles perched primarily on the broad, smooth leaves of broad leaves, whereas in Good Hope Field (GHF) they predominantly perched on branches and tree trunks. The two populations differed significantly in morphology. In Tulane, the anoles tended to have shorter distal hindlimb elements, longer forelimb elements, and were more 'slender' than those at GHF. A comparison of escape behaviour showed population and sex differences. In both populations, females had significantly longer approach distances (i.e. were more 'wary') than males. These distances were, in addition, significantly longer at GHF than at Tulane for both sexes; this may be due to the potentially higher diversity and abundance of predators at GHF, although habituation to humans may also play a role. Anoles at Tulane had significantly larger toepads and higher clinging abilities than those at GHF. The enhanced clinging abilities of anoles at Tulane may have arisen due to their propensity to use smooth leaves as their primary substrate. Overall, our data reveal substantial ecological, behavioural, morphological, and functional differences among populations, some of which may be adaptive.  © 2005 The Linnean Society of London, Biological Journal of the Linnean Society , 2005, 85 , 223–234.     

Concerning invasive species: Reply to Brown and Sax

Abstract Biological invasions have commonly occurred, and to a lesser degree continue to do so, without human assistance. It is, however, a combination of the rate and magnitude, as well as the distances and agency involved, that separates human‐driven invasion processes from self‐perpetuated colonization events. Exotic species are a pervasive and major component of human‐induced global change. Decisions to manage invasive species will require judgements to be communicated from scientists to policy makers, because scientists may often be the only ones in the position to make them.     

Chloroplast DNA variability in old and recently introduced potato cultivars

Chloroplast DNA (cpDNA) variability has been examined in a range of tetraploid European potato cultivars. The potato genotypes studied included primitive cultivars such as Lumpers (1806), Yam (1836), Myatts Ashleaf (1847) and more recently bred cultivars such as Brodick (1990). Three cpDNA pheno-types were detected and these probably represent original introductions from South America into Europe. The most common cp phenotype was the T type cpDNA (Hosaka & Hanneman, 1988) characteristic of cultivars descended from cv. Rough Purple Chili. The presence of the T type cpDNA in the cultivar Yam indicates that this genotype which is of Andigena origin shares a common cytoplasm with other 5. tuberosum ssp. tuberosum clones which have a Chilean type cytoplasm. The implications of these results are discussed in relation to the origin of the T type cpDNA. Methods for increasing the cytoplasmic diversity of the cultivated potato gene pool are proposed.     

Changes in the Petiole of Leaves of Manihot esculenta (Crantz), on Rooting

The effects of age of leaf and of application of synthetic hormoneon the ability to produce roots, were investigated in leavesof Manihot esculenta. It was found that the age of the leafwas not critical to the process, but that the application ofhormone resulted in an early and prolific production of roots. The anatomy of the rooted petiole was investigated and was foundto differ from that of an unrooted petiole in three respects:in an increase in the amount of secondarily produced tissues;in the incomplete lignification of the secondary xylem and inthe production of adventitious roots from the interfascicularregions of the basal end.     

In situ bait plants as a method for detecting red core in strawberry fields

The spread of strawberry red core root disease (Phytophthora fragariae) from a heavily infested field with a history of 40 yr continuous strawberry growing, to and across an adjacent field where strawberries had never before been grown, was charted by growing bait plants of the highly susceptible alpine strawberry ‘Baron Solemacher’ at the intersections of an 8 m grid. Initially the fungus could not be detected by a soil sampling/glasshouse baiting test or in field grown baits, but after a very wet winter it was detected in the field grown bait plants. Most infections occurred in plants growing in a shallow depression running the length of the field, receiving drainage water from the higher infested site and where there had been standing water for much of the winter. The importance of topography was further demonstrated when baits were planted at commercial densities in two small areas of the field, one adjacent to and the other 18 m distant from the central depression. In the former many plants were infected within 2 months of planting whilst in the latter bait plants remained free of the disease for at least 18 months. The highly susceptible bait plants may be suitable for monitoring the health of commercial propagation stocks; they are easily propagated from seed and as they do not runner there is little hazard to stock purity.     

A Comparison of Abscission of Rubber (Hevea brasiliensis) Leaves Infected with Microcyclus ulei with Leaf Abscission Induced by Ethylene Treatment, Deblading and Senescence

Studies on the histology and on effects of growth substancesand phenols as well as changes in activities of pectinmethylesterase indicated that the mechanism of abscission of Hevealeaflets infected with Microcyclus ulei differed from the mechanismof abscission of debladed, ethylene treated and senescent leaves.An abscission layer which was formed during abscission of debladed,ethylene-treated and senescent leaves was absent during abscissionof heavily diseased leaves. The ratio of pectinmethyl esteraseactivities in tissues distal to the abscission zone to activitiesin tissues proximal to the zone decreased in debladed and ethylenetreated leaves but such decreases were not detected during abscissionof Hevea leaves infected with M. ulei. Hevea brasiliensis Muell. Arg., rubber, leaf abscission, Microcyclus ulei, ethylene, indol-3-ylacetic acid, kinetin