Biological effects of El Niño on the Galápagos penguin

Long-term monitoring of physical and biological parameters is essential for understanding the effects of El Niño on bird populations, particularly for small or declining populations. We examined the biological effects of El Niño activity from 1965 to 2004 using instrumental sea-surface temperatures from the Galápagos Islands and 20 years of census counts of the Galápagos penguin. Between 1965 and 2004, nine El Niño events were recorded of which two were strong and seven were weak. The two strong El Niño events of 1982-1983 and 1997-1998 were followed by crashes of 77% and 65% of the penguin population, respectively. The evidence suggests that the increased frequency of weak El Niño events limits population recovery. The 2004 penguin population is estimated to be at less than 50% of that prior to the strong 1982-1983 El Niño event. We discuss the biological effects of increased El Niño intensity and frequency within the context of a 6000-year record of El Niño influence and in the light of increasing anthropogenic threats operating after 1535, when the Archipelago was discovered by Europeans.     

Localized control of ligand binding in hemoglobin: effect of tertiary structure on picosecond geminate recombination

The picosecond geminate rebinding of molecular oxygen was monitored in a variety of different human, reptilian, and fish hemoglobins. The fast (100 to 200 picoseconds) component of the rebinding is highly sensitive to protein structure. Both proximal and distal perturbations of the heme affect this rebinding process. The rebinding yield for the fast process correlates with the frequency of the stretching motion of the iron-proximal histidine mode (VFe-His) observed in the transient Raman spectra of photodissociated ligated hemoglobins. The high-affinity R-state species exhibit the highest values for VFe-His and the highest yields for fast rebinding, whereas low affinity R-state species and T-state species exhibit lower values of VFe-His and correspondingly reduced yields for this geminate process. These findings link protein control of ligand binding with events at the heme.     

Mid-ocean ridges: discontinuities, segments and giant cracks

Geological observations reveal that mid-ocean ridges are segmented by numerous rigid and nonrigid discontinuities. A hierarchy of segmentation, ranging from large, long-lived segments to others that are small, migratory, and transient, determines the pattern and timing of creation of new ocean floor. To the extent that spreading segments behave like giant cracks in a plate, the crack propagation force at segment tips increases with segment length, which may explain why long segments tend to lengthen and prevail over shorter neighboring segments. Partial melting caused by decompression of the upper mantle due to plate separation and changes in the direction of spreading result in the spawning of new short segments so that a balance of long and short segments is maintained.     

Relation of Geomagnetic Disturbances to Circulation Changes at 30,000-Foot Level

From analyses of waves in the circulation pattern at the jet-stream level of the atmosphere during the winters of 1956-57 and 1957-58, it was found that, in comparison with other waves, those which appeared in the Alaska-Aleutian area about 3 days after a magnetic disturbance subsequently developed into large-amplitude disturbances.     

The impact of sport-hunting on the population dynamics of an African lion population in a protected area

Between 1999 and 2004 we undertook an ecological study of African lions (Panthera leo) in Hwange National Park, western Zimbabwe to measure the impact of sport-hunting beyond the park on the lion population within the park, using radio-telemetry and direct observation. 34 of 62 tagged lions died during the study (of which 24 were shot by sport hunters: 13 adult males, 5 adult females, 6 sub-adult males). Sport hunters in the safari areas surrounding the park killed 72% of tagged adult males from the study area. Over 30% of all males shot were sub-adult (<4 years). Hunting off-take of male lions doubled during 2001-2003 compared to levels in the three preceding years, which caused a decline in numbers of adult males in the population (from an adult sex ratio of 1:3 to 1:6 in favour of adult females). Home ranges made vacant by removal of adult males were filled by immigration of males from the park core. Infanticide was observed when new males entered prides. The proportion of male cubs increased between 1999 and 2004, which may have occurred to compensate for high adult male mortality.     

Radioactivity in otter scats in Britain following the chernobyl reactor accident

Radioactivity was determined in samples of otter (Lutra lutra) faeces (scats) collected from various regions of Great Britain in 1986 and 1987, following the Chernobyl nuclear reactor accident, and compared with a sample of scats collected in 1985 from central Wales. Samples of scats were also collected from the seashore adjacent to the Dounreay nuclear power station, northern Scotland, and compared with a control site, 40 to 60 km distant. Samples collected in 1986 from central Wales, Galloway and northern Scotland all contained significantly higher amounts of radioactivity than the 1985 sample from central Wales, with Galloway (mean 13 000 Bq kg^?1 dry weight) having significantly more radioactivity than other regions. A sample collected in central Wales in January 1987 had returned to the 1985 level of radioactivity, but a sample from Galloway in January 1987 remained high; this difference in response may be related to the acidic nature of Galloway rivers. No significant differences were found between samples collected from near Dounreay and the control site, though fallout from Chernobyl may have masked the effects of local discharges of radioactivity. The significance of the results to otter populations is discussed.     

Long-term resource variation and group size: A large-sample field test of the Resource Dispersion Hypothesis

Background  

The Resource Dispersion Hypothesis (RDH) proposes a mechanism for the passive formation of social groups where resources are dispersed, even in the absence of any benefits of group living per se. Despite supportive modelling, it lacks empirical testing. The RDH predicts that, rather than Territory Size (TS) increasing monotonically with Group Size (GS) to account for increasing metabolic needs, TS is constrained by the dispersion of resource patches, whereas GS is independently limited by their richness. We conducted multiple-year tests of these predictions using data from the long-term study of badgers Meles meles in Wytham Woods, England. The study has long failed to identify direct benefits from group living and, consequently, alternative explanations for their large group sizes have been sought.     

Effects of Hormonal Supplementation on Nuclear Maturation and Cortical Granules Distribution of Canine Oocytes During Various Reproductive Stages

The aim of this study was to evaluate the effects of hCG, progesterone and oestradiol supplementation on nuclear and cytoplasmic maturation of canine oocytes cultured for 24, 48, 72 and 96 h. Oocytes obtained from 18 healthy bitches were divided into three groups according to their reproductive status (follicular, luteal and anoestrus stages) and cultured in TCM 199 + 25 UI/ml of hCG + 1 μg/ml of progesterone + 1 μg/ml of 17‐β oestradiol or without hormonal supplementation (control) for different periods. Then, they were stained with FITC‐LCA‐Hoescht for chromatin configuration and cortical granules distribution and evaluated under an epifluorescence microscope. Culture time and the influence of different stages of the oestrous cycle were also evaluated. The present study demonstrated that there was no significant difference among the reproductive stages. With regards to culture medium, only oocytes from the supplemented medium were able to complete meiosis; however, significant difference was only noticed in the percentage of MI stage oocytes (p < 0.05) in the follicular and luteal group at 72 h of culture. Most oocytes in germinal vesicle, germinal vesicle breakdown and metaphase I stage had cortical granules distributed throughout the cytoplasm (immature pattern), irrespective of the culture period (p < 0.05). Cortical granules distributed immediately beneath the plasma membrane (mature) was only observed in metaphase II stage oocytes, but not all of them presented matured cytoplasm. Our results reveal that cortical granules distribution in canine oocytes matured in vitro did not progressed in correspondence with nuclear stage changes and are in accordance with those from other species.