Global population structure of albacore (Thunnus alalunga) inferred by RFLP analysis of the mitochondrial ATPase gene

The genetic population structure of the highly migratory albacore (Thunnus alalunga) was investigated using restriction fragment length polymorphism (RFLP) analysis of the mitochondrial ATPase gene amplified by the polymerase chain reaction (PCR). 620 individuals comprising 13 geographically distant samples (ten Pacific, two Atlantic and the Cape of Good Hope) were surveyed between 1991 and 1994 with two restriction endonucleases (Mse I and Rsa I), resulting in seven haplotypes. No heterogeneity was observed in the distribution of haplotypes among the ten samples from the North and South Pacific, nor among the samples from North and South Atlantic and Cape of Good Hope. However, highly significant heterogeneity was evident among Atlantic and Pacific samples. Higher haplotypic diversity (h) was observed in the Pacific samples (0.59 to 0.69) than in the Atlantic and Cape samples (0.22 to 0.43). These results suggest greater gene flow between albacore of the northern and southern hemispheres (within oceans) than between the Atlantic and Pacific Oceans.     

Multiple trans-Arctic passages in the red alga Phycodrys rubens: evidence from nuclear rDNA ITS sequences

In order to investigate how episodes of geological and climatic change have influenced the distribution and evolutionary diversification of Arctic to cold temperate-North Atlantic seaweed species, intraspecific genetic variation was analyzed among isolates of the sublittoral, benthic red alga Phycodrys rubens (collected between June 1992 and January 1994). Rooted phylogenetic analyses of nuclear ribosomal DNA internal transcribed spacer (ITS) sequences and the plastid encoded Rubisco spacer sequences suggest that P. rubens invaded the North Atlantic from the Pacific shortly after the opening of the Bering Strait (3 to 3.5 million years ago), colonizing both the western and eastern Atlantic coasts. Based on these data we further hypothesize that P. rubens survived along the European coasts during the more recent Pleistocene glaciations, while becoming locally extinct along the North American Atlantic coasts. Following retraction of the last ice sheet, the western Atlantic coast was colonized a second time from the Pacific. The presence of two distinct genetic types (based on ITS and Rubisco sequences) along the European coasts is postulated to be a result of isolation and subsequent differentiation. This is likely because ice-free areas are known to have existed in northern Scotland and Norway during the last glaciation. The presence of an East Atlantic genetic type along the West Atlantic coast is believed to be a recent introduction (caused by human activity) of P. rubens to Newfoundland.     

Movements of albacore tuna (Thunnus alalunga) in the South Pacific: Evidence from parasites

Parasites were collected from over 400 albacore (Thunnus alalunga) caught by surface trolling and longlining in the south-west Pacific between 1985 and 1988. Parasites found included 1 apicomplexan, 3 nematode species, 4 cestode species, 1 acanthocephalan, 12 digenean species and 3 copepod species. Twelve of these parasite species which could be accurately recognised and counted were used in the subsequent analyses. Parasite data from albacore caught around New Zealand show a decrease in prevalence of three didymozoid parasites with increasing fish length up to a fork length of 70 to 79 cm. The subsequent increase in prevalence of these didymozoids in large longline-caught fish is consistent with fish returning from spawning in tropical waters where re-infection is presumed to occur. Albacore collected at widely separate locations in the south-west Pacific have differences in parasite prevalence, supporting an hypothesis that juvenile albacore move south to New Zealand from the tropics and do not return until the onset of sexual maturity. Albacore appear to move along the subtropical convergence zone, as indicated by a decline in prevalence and abundance ofAnisakis simplex andHepatoxylon trichiuri from New Zealand to the central South Pacific. This is supported by tagging and seasonal movements of the fishery.     

The disposal of flue gas desulphurisation waste: sulphur gas emissions and their control

Flue gas desulphurisation (FGD) equipment to be fitted to UK coal-fired power stations will produce more than 0.8 Mtonnes of calcium sulphate, as gypsum. Most gypsum should be of commercial quality, but any low grade material disposed as waste has the potential to generate a range of sulphur gases, including H₂S, COS, CS₂, DMS and DMDS. Literature data from the USA indicates that well-oxidised waste with a high proportion of calcium sulphate (the main UK product of FGD) has relatively low emissions of sulphur gases, which are comparable to background levels from inland soils. However, sulphur gas fluxes are greatly enhanced where reducing conditions become established within the waste, hence disposal strategies should be formulated to prevent the sub-surface consumption of oxygen.     

Sexual selection and the tail ornaments of North American barn swallows

Summary In this study conducted in southeastern Ontario, Canada, we manipulated the length of outer tail feathers (streamers) of male barn swallows (Hirundo rustica) shortly after they returned to four small breeding colonies in the spring. Both streamers on most males in these colonies were experimentally either lengthened or shortened by 20 mm and as a result 10 randomly chosen males of each category had their streamer lengths manipulated before the fertile period of their mate. Males with elongated streamers had a significantly shorter pre-laying period (from arrival until first egg date) than those with shortened streamers and we interpret this as indicating that they obtained their mates more rapidly. Females mated to elongated males had significantly longer tails and laid their first egg significantly earlier than those mated to shortened males; no other indices of reproductive success differed between these two experimental groups. These results provide some support for previous work suggesting that females prefer males with longer streamers and thus that streamer length in this species is under the influence of sexual selection. We also found that males with longer natural streamers were significantly more likely to break them and that males were much more likely to break their streamers than were females. Since males participate in incubation in North America but not in Europe, we suggest that the aerodynamic disadvantages of streamer breakage that result from incubation attentiveness are at least partly responsible for the shorter streamer length of males in North America. Offprint requests to: R. Montgomerie     

Quecksilber in Boden und Pflanzen

The former mercury mining districts in Platina (Rheinland-Pfalz, Germany) are now overgrown with a more-or-less dense cover of vegetation. Much of the area is in agricultural use. Cultivated fields around the community of Mörsfeld have been analyzed. The mercury concentration in soil samples exceeds the threshold values set for sewage sludge by up to 10. 000 fold. Wheat grain cultivated in this area has a Hg content of up to 100 times higher than the threshold values set by the WHO/FAO. The accummulation was found to be organ specific and varies by species. The highest Hg concentration was measured in mosses, the lowest in leaves of shrubs.     

Accumulation of cadmium by larvae and adults of an Hawaiian bivalve,Isognomon californicum,during chronic exposure

Larvae and adults of an Hawaiian bivalve, Isognomon californicum, were exposed to sublethal, environmentally realistic concentrations of cadmium (2 and 20 ppb) for 28 d, and the accumulation of cadmium was evaluated. The concentrations of cadmium were expressed in terms of total cadmium (tissue and shell concentrations combined) and tissue cadmium. The accumulation rates of larvae were one to two orders of magnitude greater than adult rates. This study suggests that the faster uptake rates of larvae may explain why larvae are more sensitive than adults. Furthermore, the magnitude of differences between larval and adult accumulation rates may be related to metabolic rate. When larvae and adults were exposed to cadmium for only 14 d, followed by a 14 d depuration period, a substantial loss of cadmium was observed during the depuration period. Possible accumulation mechanisms and their similarity between larvae and adults are discussed.