Implications of Age, Size and Region on Mercury Contamination in Estuarine Fish Species

This study investigated the effects of age and length on mercury contamination in four fish species; yellow-eye mullet (Aldrichetta forsteri), black bream (Acanthopagrus butcheri), sand flathead (Platycephalus bassensis) and sea-run brown trout (Salmo trutta) from the Derwent Estuary, Tasmania, Australia, and examined the implications of these findings for public health monitoring. Mean mercury levels exceeded the Food Standards Australia and New Zealand maximum permitted level (0.5?mg?kg^?1) for all species except yellow-eye mullet. Mean levels in black bream were significantly higher (p?<?0.05) than other species and consequently are a particular concern for human health. Regional differences (p?<?0.05) in mercury levels in sand flathead were not obviously correlated with metal levels in the sediments. However, age and length significantly (p?<?0.05) influenced mercury levels in brown trout and sand flathead, with age being more strongly related to intraspecies differences. In addition, movement and distribution within the estuary and trophic status appeared to be important factors in contribution to interspecific variation. Consequently, a sound understanding of fish life history and biology is important in identifying species which may be susceptible to accumulating mercury and hence pose a potential threat to human health.     

Evaluation of a comprehensive method for total glycoalkaloid determination

Evaluation of the only available method for comprehensive total glycoalkaloid determination was carried out. The method comprised bisolvent extraction of glycoalkaloids followed by purification and non-aqueous titration of the aglycones released from the glycoalkaloids by acid hydrolysis. Our data show that use of the bisolvent extraction procedure can result in poor and variable recovery of glycoalkaloid standard. The post-extraction part of the analysis yielded high and reproducible recoveries of glycoalkaloid standard.     

NOTES AND COMMENTS—VAN DIE REDAKSIE

Experiments to test direct sowing as an establishment technique for Pinus radiata are described and discussed. It is concluded that sowing should be restricted to sites which can be established by planting without difficulty; that seed should be treated for dormancy; and that only repellent-coated seed should be used. Spot sowing proved an economically attractive method which deserves much wider attention. Costs of spot sowing operations are given and compared with planting costs. Sowing to establish dense stands is shown to be feasible but wasteful of seed. Burning is recommended before sowing to establish dense stands.     

Canine Ear Disease*

Abstract— —The authors describe briefly the anatomy and histology of the normal ear and the histopathological changes associated with otitis. The bacteria and fungi associated with infections of the ear are discussed. The incidence and results of treatment of otitis externa in out-patient and hospitalised cases are reported and the techniques and results of surgical procedures for conditions of the ear are detailed.     

Postbloom fruit drop of citrus and key lime anthracnose are caused by distinct phylogenetic lineages of Colletotrichum acutatum

Colletotrichum acutatum causes two diseases of citrus, postbloom fruit drop (PFD) and Key lime anthracnose (KLA). PFD is a disease restricted to flowers of sweet orange and most other citrus, and symptoms include petal necrosis, abscission of developing fruit, and the formation of persistent calyces. KLA is a disease of foliage, flowers, and fruits of Key lime only, and symptoms include necrotic lesions on leaves, fruits, twigs, flowers, and blight of entire shoots. The internal transcribed spacers 1 and 2 and the gene encoding the 5.8S ribosomal RNA subunit within the nuclear ribosomal cluster (ITS) and intron 2 of the glyceraldehyde-3-phosphate dehydrogenase gene (G3PD) were sequenced for isolates from PFD-affected sweet orange and KLA-affected Key limes collected in the United States (Florida), Brazil (S?o Paulo), Mexico, Belize, Costa Rica, and the Dominican Republic to determine if there are consistent genetic differences between PFD and KLA isolates over the geographic area where these diseases occur. Based on the sequence data, isolates clustered into two well-supported clades with little or no sequence variation among isolates within clades. One clade (PFD clade) contained PFD isolates from all countries sampled plus a few isolates from flowers of Key lime in Brazil. The other clade (KLA clade) contained KLA isolates from Key lime foliage from all countries sampled and one isolate from flowers of sweet orange in Mexico. In greenhouse inoculations with PFD and KLA isolates from Florida, isolates from both clades produced PFD symptoms on Orlando tangelo flowers, but KLA-clade isolates produced significantly less severe symptoms. PFD-clade isolates were not pathogenic to Key lime foliage, confirming previous studies. The differentiation of PFD and KLA isolates into two well-supported clades and the pathogenicity data indicate that PFD and KLA are caused by distinct phylogenetic lineages of C. acutatum that are also biologically distinct. PFD is a recently described disease (first reported in 1979) relative to KLA (first reported in 1912) and it had been proposed that strains causing PFD evolved from strains causing KLA eventually losing pathogenicity to Key lime foliage. We reject the hypothesis that PFD strains have diverged from KLA strains recently based on estimated divergence times of haplotypes and it appears that PFD and KLA strains have been dispersed throughout the Americas independently in association with each host.