Experimental corticosterone manipulation increases mature feather corticosterone content: implications for inferring avian stress history from feather analyses

Feathers incorporate circulating steroids during development. It is therefore assumed that the corticosterone (CORT) content of feathers (CORTf) represents an integrated measure of plasma CORT over the moult period. We tested this assumption by quantifying CORTf in feathers of house sparrows (Passer domesticus (Linnaeus, 1758)) that were plucked before and after experimental manipulation of circulating CORT. Two of the seven flight feathers collected from each bird were fully grown throughout the CORT-manipulation period. We found that CORTf of all seven feathers corresponded with plasma CORT levels of non-moulting reference sparrows given the same implants. Surprisingly, the CORTf of the two mature feathers was 4 to 10-fold higher than values measured in the new replacement feathers. Our results show that CORTf of mature feathers may be affected by circulating CORT outside the moulting period. The most plausible explanation for our results is that CORT was transferred onto feather surfaces externally, but the mechanisms involved remain to be identified. Researchers are encouraged to establish effective procedures, both in terms of solvent and duration, for removing surface residues without extracting CORT from within the feather. This will increase confidence when inferring moult-related stress status from feather analyses in future ecological studies.

Moulting phenology of the harbour seal in south-west Ireland

Studies on the phenology of harbour seal moult have been carried out in the Atlantic and Pacific, however there has been no research into this process in the Republic of Ireland, at the southern edge of the species range in the north-east Atlantic. Population estimates of harbour seals are derived by counts primarily during the moulting seasons. In the absence of information on the moult phenology planning the optimal timing of such surveys is impossible. Furthermore, changes in moult phenology may reflect changes in resource availability or competition, or demographic changes. The phenology of the harbour seal moult was investigated in south-west Ireland in this study. Timing of the moult differed among all cohorts, yearlings began moulting first followed by adult females and finally adult males. The number of seals hauled out was generally positively related to the proportion of seals in active moult. The timing of the moult period was different to other parts of the species' range and should be considered in determining optimal timing of future surveys for assessing populations abundance and trends in Ireland.

Some like it hot: the effect of temperature on brood development in the invasive crab Hemigrapsus takanoi (Decapoda: Brachyura: Varunidae)

The duration of brood development in the introduced crab, Hemigrapsus takanoi in the Oosterschelde, The Netherlands, was compared at three different water temperatures. At 12, 18 and 24°C the females took an average of 32, 11 and 8 days respectively to lay eggs, which took 86, 28 and 18 days respectively to complete development. Five stages of development were identified, with each brood stage comprising a similar proportion of the duration time at different temperatures. The duration of each brood stage was also somewhat proportional to the number of females found carrying each brood stage in the field at the beginning of the breeding season. There appears to be a trigger for the breeding season in H. takanoi in the field at around 15°C above which ovary development begins. The results suggest that an increase in water temperature as a result of climate change may result in an increased net reproductive rate in H. takanoi due to earlier onset of the breeding season and increased number of broods per inter-moult period resulting in population growth. Increased temperatures may therefore lead to increased invasiveness of H. takanoi where it is already present, and range extension into locations where its establishment is currently excluded by unsuitable temperature.

A crustacean Ca2+-binding protein with a glutamate-rich sequence promotes CaCO3 crystallization

The DD4 mRNA of the penaeid prawn Penaeus japonicus was shown previously to be expressed in the epidermis adjacent to the exoskeleton specifically during the post-moult period, when calcification of the exoskeleton took place. The encoded protein possessed a Ca2+-binding site, suggesting its involvement in the calcification of the exoskeleton. In the present study, an additional ORF (open reading frame) of 289 amino acids was identified at the 5′ end of the previous ORF. The newly identified part of the encoded protein included a region of approx. 120 amino acids that was highly rich in glutamate residues, and contained one or more Ca2+-binding sites. In an immunohistochemical study, signals were detected within calcified regions in the endocuticular layer of the exoskeleton. Bacterially expressed partial segments of the protein induced CaCO3 crystallization in vitro. Finally, a reverse transcription-PCR study showed that the expression was limited to an early part of the post-moult period, preceding significant calcification of the exoskeleton. These observations argue for the possibility that the encoded protein, renamed crustocalcin (CCN), promotes formation of CaCO3 crystals in the exoskeleton by inducing nucleation.

The annual cycle of the White-ruffed ManakinCorapipo leucorrhoa, a tropical frugivorous altitudinal migrant, and its food plants

SummaryFrugivorous White-ruffed ManakinsCorapipo leucorrhoa(Pipridae) showed pro nounced seasonal emigration from a pre-montane wet forest site (550 m) on the Atlantic slope of Costa Rica. “Resident” breeders left the area between August and October, and returned between February and April, at the onset of the breeding season. Female patterns differed from those of males primarily in later departure (October) and later return (April). I documented 57 fruit species in the diet at this locality and monitored phenology for 43 of those species, many of which were understorey members of the Melastomataceae. The emigration did not coincide with a period of local fruit shortage (relative to abundance at the same locality in other months), but the relative abundance and species composition of fruit resources in the areas to which the manakins migrated remains unknown. However, peak resources did coincide with the period in which recent fledglings would be commonest and the period during which most individuals were moulting prior ot emigration. Resources were lowest from November, when residents were absent, untilJune, well into the breeding season. Tentative evidence suggests considerable annual variation, possibly owing to differences in the timing of the rainy season. Individuals captured during the period when almost all “resident” breeders were absent (November) appeared to be transients, and were rarely recaptured. Weights differed between sexes, with females (χ = 12.5 ± 1.0) significantly heavier than males (χ = 11.1 ± 0.8). Males were lightest during the breeding season, intermediate in weight during the moulting period, and both sexes were heaviest during the migration period, when they accumulated subcutaneous fat. Females were lightest during the moult period, at which time many may also have dependent fledglings. Many other frugivores and nectarivores may engage in similar altitudinal migrations. Even where altitudinal migration is not possible, birds might migrate to other habitats with different fruit resources or phenologies. The design of nature reserves should accommodate the possibility of significant altitudinal (or cross-habitat) migration for many species of frugivores and nectarivores.

POST-MOULT CALCIFICATION IN THE BLUE CRAB, CALLINECTES SAPIDUS: TIMING AND MECHANISM

A series of experiments was conducted to elucidate the events immediately preceding and following moulting (ecdysis) in the blue crab, Callinectes sapldus Rathbun. The crabs gain weight (mostly water) to a level more than twice the premoult value excluding the shed carapace. The gain begins about 4 h before ecdysis, accelerates rapidly to a maximum rate at about the time of ecdysis, and is essentially complete by 2h after ecdysis. Both calcification and net H+ excretion remain at control (intermoult) levels until 1–2 h post-moult, whereupon a very rapid increase in both begins, with the same time course for both processes. The ratio of internal to external calcium concentration drops from 1.4:1 during intermoult to 0.85:1 by 2 days after the moult, reversing the electrochemical gradient during the post-moult period. Calcification is strongly inhibited by the protein synthesis inhibitors actinomycin D and cycloheximide. Isolated whole gills and gill slices do not show significant changes in rates of calcium uptake related to moult stage, indicating that the uptake of calcium across the gills may be largely passive. A low-affinity Ca2+-activated ATPase is present in both gills and epithelium, but only the epithelial activity shows a substantial (fivefold) increase in the hours after ecdysis. The control mechanisms for stimulation of the transport processes remain elusive. Eyestalkless crabs progress normally through moult and post-moult calcification. Peptide profiles from blood and from suspected neurohormone- producing tissues differ markedly with moult stage, but several different approaches to developing a bioassay using peptides from crab tissues and vertebrate sources have been unsuccessful. The physiological events in the hours surrounding ecdysis suggest a complex and precisely timed series of control signals.

Effect of flightlessness during moult on the iron content in the pectoralis muscle of the Giant Canada Goose (Branta canadensis maxima)

Adult male Giant Canada Geese, collected from a nonmigratory wild population during their premoult, moult, and postmoult periods were studied for changes in the pectoralis muscle. A significant (p ≤ 0.0001) drop in the lean dry weight of the pectoralis muscle during the moult period when the birds were flightless was attributed to disuse atrophy. The concentration of iron in the pectoralis muscle increased significantly (p ≤ 0.0054) during the moult, but the total amount of iron in the muscle remained constant during the three periods. It was revealed that iron was not lost during disuse atrophy, but that it became more concentrated as muscle mass decreased. The diverse results reported in the literature need to be reevaluated in light of concurrent changes in muscle under different experimental conditions and also the different fiber type composition of the muscles studied.