Kate Griffiths

Telomere length in early life predicts lifespan

The attrition of telomeres, the ends of eukaryote chromosomes, is thought to play an important role in cell deterioration with advancing age. The observed variation in telomere length among individuals of the same age is therefore thought to be related to variation in potential longevity. Studies of this relationship are hampered by the time scale over which individuals need to be followed, particularly in long-lived species where lifespan variation is greatest. So far, data are based either on simple comparisons of telomere length among different age classes or on individuals whose telomere length is measured at most twice and whose subsequent survival is monitored for only a short proportion of the typical lifespan. Both approaches are subject to bias. Key studies, in which telomere length is tracked from early in life, and actual lifespan recorded, have been lacking. We measured telomere length in zebra finches (n = 99) from the nestling stage and at various points thereafter, and recorded their natural lifespan (which varied from less than 1 to almost 9 y). We found telomere length at 25 d to be a very strong predictor of realized lifespan (P < 0.001); those individuals living longest had relatively long telomeres at all points at which they were measured. Reproduction increased adult telomere loss, but this effect appeared transient and did not influence survival. Our results provide the strongest evidence available of the relationship between telomere length and lifespan and emphasize the importance of understanding factors that determine early life telomere length.

Sex-biased incidental mortality of albatrosses and petrels in longline fisheries: differential distributions at sea or differential access to baits mediated by sexual size dimorphism?

Skewed adult sex ratio (ASR) has been proposed as a common pattern in birds, frequently biased towards males and with larger biases in globally threatened species. In albatrosses and petrels, it has been suggested that differential mortality of one gender in fisheries is caused either by sexual size dimorphism giving males a competitive advantage, which allows more access of the larger sex (i.e. males) to discards and/or baits, or to at sea segregation of sexes. Here, we tested these hypotheses by determining ASRs in albatrosses and petrels trapped at sea when attending longline fishing vessels for discards in the southwestern Atlantic Ocean, and searched in the literature for patterns in ASR in albatrosses and petrels killed by fisheries in this area and elsewhere. We show that skewed ASR is common in albatrosses and petrels in the community attending vessels for discards, confirming results found for birds in general. There was no correlation between skewed ASR and conservation status, or between ASR and sexual size dimorphism. Our review of the sex of birds incidentally killed in fisheries found skewed ASR toward males, females or parity to be equally reported. Thus, sexual dimorphism in size does not explain skewed ASR in the community we sampled or in incidental captures in fisheries in the review. Differential at-sea distribution of sexes appears to be a better explanation of the patterns found in the community sampled at sea as well as skewed ASR in seabird fatalities, particularly distant from breeding areas.

Repeated exposure to stressful conditions can have beneficial effects on survival.

Repeated exposure to stressful circumstances is generally thought to be associated with increased pathology and reduced longevity. However, growing lines of evidence suggest that the effects of environmental stressors on survival and longevity depend on a multitude of factors and, under some circumstances, might be positive rather than negative. Here, using the zebra finch (Taeniopygia guttata), we show that repeated exposure to stressful conditions (i.e. unpredictable food availability), which induced no changes in body mass, was associated with a decrease in mortality rate and an increase in the age of death. As expected, the treated birds responded to the unpredictable food supply by increasing baseline glucocorticoid stress hormone secretion and there were no signs of habituation of this hormonal response to the treatment across time. Importantly, and consistent with previous literature, the magnitude of hormone increase induced by the treatment was significant, but relatively mild, since the baseline glucocorticoid concentrations in the treated birds were substantially lower than the peak levels that occur during an acute stress response in this species. Taken together, these data demonstrate that protracted exposure to relatively mild stressful circumstances can have beneficial lifespan effects.

Diversity in the structures and ligand-binding sites of nematode fatty acid and retinol-binding proteins revealed by Na-FAR-1 from Necator americanus.

Necator americanus fatty acid and retinol-binding protein-1 (Na-FAR-1) is an abundantly expressed FAR from a parasitic hookworm. The present work describes its tissue distribution, structure and ligand-binding characteristics and shows that Na-FAR-1 expands to transport multiple FA molecules in its internal cavity.

Is sex-specific mass gain in Cory’s shearwaters Calonectris diomedea related to begging and steroid hormone expression?

Mass differences between the sexes of dimorphic bird species often appear early in the nestling development. But how do adults know how much to feed a chick in a sexually dimorphic species? Do chicks of the heavier sex beg more? We studied begging in Cory’s shearwaters Calonectris diomedea, a species with heavier adult and juvenile males than females. We found that begging rates and call numbers were not different between male and female chicks, but parameters of begging intensity differed between the sexes in their relationship to chick body condition. For the same body condition, males had significantly higher begging call numbers and rates. Acoustical parameters, which were analysed semi-automatically, included the lengths of call and silence intervals, the minimum, mean and maximum frequency in a call and the number of frequency peaks within a call. We found no consistent differences of acoustic begging call elements between the sexes. Male and female chicks did not differ in the levels of the steroid hormones testosterone or corticosterone in the second quarter of the nestling period, and the mechanism leading to sex-related differences in begging rates for a given body condition remains unknown.

Subspecies status of Common Eiders Somateria mollissima in Shetland based on morphology and DNA

Capsule Morphometrics, plumage and mitochondrial DNA of Common Eiders Somateria mollissima in Shetland indicate that these birds should be classified as subspecies faeroeensis. Aims To test whether molecular data support the suggestion based on measurements that Common Eiders in Shetland belong to the subspecies faeroeensis. Methods DNA extracted from Common Eiders found dead in Shetland was amplified and a section of the mitochondrial genome was sequenced to compare with data from birds previously sampled from Iceland, Faroes, east England and continental Europe. Results Shetland Common Eiders are closely similar to birds from the Faroe Islands classified as subspecies faeroeensis, and somewhat distinct from the nominate mollissima to which all Scottish eiders have been conventionally assigned. Eiders from southern Iceland have haplotypes more similar to faeroeensis despite differing in plumage and being assigned on plumage to a different subspecies borealis. Conclusion Molecular data indicate a need to revise the classification of common eider subspecies, with birds from Shetland considered as subspecies faeroeensis.

Prolonged transition time between colostrum and mature milk in a bear, the giant panda, Ailuropoda melanoleuca

Bears produce the most altricial neonates of any placental mammal. We hypothesized that the transition from colostrum to mature milk in bears reflects a temporal and biochemical adaptation for altricial development and immune protection. Comparison of bear milks with milks of other eutherians yielded distinctive protein profiles. Proteomic and metabolomic analysis of serial milk samples collected from six giant pandas showed a prolonged transition from colostrum to main-phase lactation over approximately 30 days. Particularly striking are the persistence or sequential appearance of adaptive and innate immune factors. The endurance of immunoglobulin G suggests an unusual duration of trans-intestinal absorption of maternal antibodies, and is potentially relevant to the underdeveloped lymphoid system of giant panda neonates. Levels of certain milk oligosaccharides known to exert anti-microbial activities and/or that are conducive to the development of neonatal gut microbiomes underwent an almost complete changeover around days 20–30 postpartum, coincident with the maturation of the protein profile. A potential metabolic marker of starvation was detected, the prominence of which may reflect the natural postpartum period of anorexia in giant panda mothers. Early lactation in giant pandas, and possibly in other ursids, appears to be adapted for the unique requirements of unusually altricial eutherian neonates.

Two crystal forms of a helix-rich fatty acid- and retinol-binding protein, Na-FAR-1, from the parasitic nematode Necator americanus

Na-FAR-1, a fatty acid- and retinol-binding protein, was expressed in bacteria, purified and crystallized. Crystals grew in two different morphologies under the same conditions.

Are European starlings breeding in the Azores archipelago genetically distinct from birds breeding in mainland Europe

The European starling (Sturnus vulgaris) has recently been found to eat eggs of the endangered roseate tern (Sterna dougallii) in the Azores. Azorean starlings are considered an endemic subspecies (S. vulgaris granti), so we investigated how much genetic divergence has accumulated between the Azores and other European populations in order to assess whether lethal control measures might be possible, as previous experiments have found that taste aversion is not likely to be successful. For this purpose, we sequenced a region of the protein-coding mitochondrial gene ND2 for samples from six different populations. Of the 1,026 base pairs sequenced, 19 (1.7%) were variable and formed 15 different haplotypes. The Azores had high and significant genetic differentiation from all the other populations studied. Haplotype diversity was high in the mainland populations studied, ranging from 0.767 to 0.900, but there was no variation among the Azores samples, which were collected from a geographically broad region. Given the lack of genetic variability in the Azores birds and their abundance throughout the archipelago, lethal control on a local basis and as part of an integrated control plan can be seen as a reasonable measure to protect tern colonies.

Paternal attractiveness and the effects of differential allocation of parental investment

The differential allocation hypothesis (DAH) predicts that an individual should vary its reproductive investment according to the attractiveness of its mate. A recently revised version of the DAH makes explicit that investment can be positive, i.e. higher for the offspring of attractive males which should be of higher quality, or negative, i.e. higher for offspring of unattractive males, for example compensating for inheriting poor paternal genes. Moreover, investment can be made by the father and the mother. Here, we tested whether experimental manipulation of male attractiveness affected parental investment at different reproductive stages and thus influenced fitness-related traits in offspring. In two aviaries, all male zebra finches, Taeniopygia guttata, were given red leg rings to increase attractiveness and in two aviaries all males received green leg rings to decrease attractiveness. This controlled for assortative mating between treatments. Ring colour was merely an experimental manipulation of male attractiveness, not paternal quality, so we might expect additional investment to elevate offspring quality. Eggs were cross-fostered between and within treatments to allow differentiation of effects of investment in eggs and nestlings. Clutch and brood sizes were standardized. Both positive and negative investment were observed: Eggs from red-ringed fathers had higher yolk to albumen ratios than eggs from green-ringed fathers. Nestlings from eggs laid and incubated by parents in the red-ringed group had higher hatching masses than those in the green-ringed group. Both parents in the green-ringed group fed nestlings more frequently than red-ringed parents. Offspring performance was influenced by the treatment of both foster and biological parents, but combined effects of these different investment patterns on fitness-related traits were ambiguous. Male attractiveness appeared to affect patterns of reproductive investment but not consistently across all forms of reproductive investment suggesting that the costs and benefits of differential allocation vary among individuals and across contexts.