Biology subjects

Portugal, S.

Publications and source records attributed to Portugal, S..

5 recordsLinked to original sources

bioRxiv2020

Pre-winter fattening and fat loss during wing moult: the annual cycle of fat deposition in captive barnacle geese (branta leucopsis)

Many different physiological changes have been observed in wild waterfowl during the flightless stage of wing moult, including a loss of body mass. Previously we established that captive barnacle geese (Branta leucopsis) underwent this characteristic decrease in body mass during their wing moult, even though they had unlimited and unrestricted access to food. In the present study we aimed to determine if this body mass loss during moult comprised mainly a reduction in fat stores, and to ascertain if the captive geese undergo pre-migratory and pre-winter fattening over a similar temporal scale to their wild conspecifics. The non-destructive technique of deuterium oxide isotope dilution was employed to provide repeated measurements of estimated fat deposition from a captive flock of fourteen barnacle geese. Birds were injected with deuterium oxide at 7 distinct intervals for one annual cycle. During the flightless period of the moult, body fat decreased by approximately 40% from the pre-moult value. During late-September and early October, body fat reached its highest point in the annual cycle, both as an absolute value and as a percentage of total body mass. We propose that while the energetic cost of wing moult is not the ultimate cause of fat loss in moulting barnacle geese, the approximate 212 g of fat catabolised during moult would provide sufficient energy to cover the cost of the replacement of the flight feathers, estimated to be 6384 kJ, over an approximate 42 day period. We conclude that the previously recorded increase in metabolism during moult in the geese, led to the use of endogenous fat reserves because the birds reduced rather than increased their food intake rates owing to the increased risk of predation when flightless. We also conclude that captive barnacle geese do undergo pre-winter and pre-migratory fattening, providing further evidence of the innate nature of these fat deposition cycles.Competing Interest StatementThe authors have declared no competing interest.View Full Text

zoology↗

bioRxiv2020

The determinants of aggression in male Siamese fighting fish, Betta splendens

Siamese fighting fish, Betta splendens, have been extensively studied due to their aggression and stereotypical displays. Many studies have focused on their characteristic opercular flaring, while the less aggressive and less energetically costly lateral display have been comparatively understudied. Many factors have been shown to influence aggression in Bettas, notably body length and the personality trait of boldness, however, the role that colour plays in determining an individuals aggressiveness is much less clear. The role of colour has only been briefly studied, and based on human interpretations of colour, i.e. limited to what the receivers eyes and sensory systems actually can process and discriminate, with results suggesting blue males are more aggressive than red males. Using male-male interactions, measuring opercular flaring and lateral display we found that colour and personality do play a role in determining the degree of aggressiveness in Betta splendens. Blue-finned males were more aggressive, performing longer lateral displays more frequently. Blue fins are a phenotype observed in wild type males and is likely selected for to allow visual cues to travel through the murky water they inhabit. Body mass was positively correlated with lateral display frequency, and opercular flare frequency and duration. Finally, neophobic individuals - individuals that were less willing to approach a novel object - were more aggressive, performing significantly more lateral displays. This indicates that personality may impact fighting strategy, with males either choosing to end conflicts quickly with more aggressive displays or to outlast their opponent with less energetically costly displays.

animal behavior and cognition↗

bioRxiv2020

Overall dynamic body acceleration as an indicator of dominance in homing pigeons

The benefits of dominance are well known and numerous, including first access to resources such as food, mates and nesting sites. Less well studied are the potential costs associated with being dominant. Here, the movement of two flocks of domestic homing pigeons (Columba livia) - measured via accelerometry loggers - was recorded over a period of two weeks. Movement was then used to calculate each individuals daily overall dynamic body acceleration (ODBA, G), which can be used as a proxy for energy expenditure. The dominance hierarchy of the two flocks was determined via group-level antagonistic interactions, and demonstrated a significantly linear structure. The most dominant bird within each flock was found to move significantly more than conspecifics - on average, c.39% greater than the individual with the next highest degree of movement - indicating a possible cost to possessing the top rank within a hierarchy. Despite the dominance hierarchy being linear, mean daily total ODBA did not reflect a linear nature, with no pattern observed between rank and ODBA, once the top ranked individuals had been accounted for. This suggest that energy expenditure may be more reflective of a despotic hierarchy. These results show the potential for the future use of accelerometery as a tool to study the fusion of energetics and behaviour. Subject Categorybehaviour Subject Areasbehaviour, physiology

animal behavior and cognition↗

bioRxiv2020

Mechanics Of Flight Feathers: Effects Of Captivity?

ABSTRACTFeathers act as aerodynamic cantilevers, and to withstand the prolonged cyclical loading that occurs during flight, feathers must be stiff, lightweight and strong. We experimentally tested the differences in feather structure, primarily stiffness and size, between (a) wild and captive Barnacle Geese Branta leucopsis, and (b) primary feathers dropped during the annual flight feather moult, and those feathers freshly regrown during the moult process. We found that, despite having undergone a 5,000km round-trip migration, flight feathers dropped during moult in the wild geese were stiffer than those measured in the captive geese, both for those dropped during moult and those re-grown. We propose that this may be related to diet or stress in the captive geese.Competing Interest StatementThe authors have declared no competing interest.View Full Text

zoology↗

bioRxiv2020

Plasmodium falciparum-specific IgM B cells dominate in children, expand with malaria and produce parasite inhibitory IgM

IgG antibodies are known to play a central role in naturally acquired immunity to blood-stage malaria in humans, but little is known about the IgM response to blood-stage malaria, the mechanisms by which IgM may protect, or the underlying biology of Plasmodium falciparum (Pf)-specific IgM B cells. In a Mali cohort spanning infants to adults we conducted a longitudinal analysis of B cells specific for the Pf blood-stage antigens AMA1 and MSP1, as well as the comparator antigen influenza hemagglutinin (HA). At the uninfected baseline, before the malaria season, Pf-specific memory B cells (MBCs) in children are disproportionally IgM+ and only gradually shift to IgG+ with age, in contrast to HA-specific MBCs that are predominantly IgG+ from infancy to adulthood. In response to acute febrile malaria, Pf-specific IgM B cells increase in frequency and upregulate activation and co-stimulatory markers. B cell receptor (BCR) analysis showed that Pf-specific IgM B cells are somatically hypermutated at levels comparable to HA-specific IgG B cells. Finally, IgM antibodies from the plasma of malaria-exposed individuals were comparable to IgG in inhibiting Pf blood-stage growth in vitro, and significantly better at enhancing phagocytosis of Pf merozoites, suggesting that IgM may protect through both direct neutralization and opsonization. Thus, somatically hypermutated Pf-specific IgM MBCs dominate in early life, are activated and expand during acute malaria and are associated with plasma IgM that inhibits parasite growth in vitro.

immunology↗