Duration Of Moult Research Articles

Primary moult of European Turtle Dove Streptopelia turtur in northern Senegal

ABSTRACT We used tabulated data from the literature, collected in northern Senegal, to estimate the parameters of moult of the European Turtle Dove Streptopelia turtur, a ‘Vulnerable’ species. Moult duration was 177 days, and the estimated average start and end dates were 16 August and 9 February respectively. The results of the moult analysis were compatible with independent studies of migration and residency; coordinated long-term monitoring of the components of the annual cycle would help an understanding of the conservation needs of this species. The European Turtle Dove is the most migratory member of the order Columbiformes; a comparison with three other members of the order, using the Underhill–Zucchini moult model, shows that moult duration of the European Turtle Dove is the shortest, but only by a small margin.

Moult of overwintering Wood Warblers Phylloscopus sibilatrix in an annual-cycle perspective

Wood Warblers, an Afro-Palearctic migrant species, are declining steadily in Europe likely due to mortality outside their breeding grounds. However, little is known about their overwintering, and records about the sensitive life-cycle stage of moult in Africa are practically absent. To fill this gap, we report on moult of Wood Warblers captured over two winters (January–February) in 2019–2020 in Cameroon. We caught 14 individuals, of which 12 were monitored for flight feather moult. All inspected individuals showed advanced stages of flight feather renewal. Despite low sample sizes, Underhill-Zucchini moult models aptly explained variation in primary and secondary moult (R2 = 0.61). Estimated moult onset date was 26 December, completion date was 25 February, and moult duration was 61 days. These findings fit well with experimental data on the annual cycle and the timing of recently published migration tracks of Wood Warblers. Jointly, the data suggest that moult timing is set by an internal programme, which enables Wood Warblers to organise their multi-stage migration such that they reach suitable moulting habitat in time, and can depart in time with a fresh plumage for the breeding grounds. In our study, moult occurred during the peak of the dry season, which in Cameroon nonetheless shows high relative humidity. During our mist-netting on 28 cocoa plantations of varying shade cover, Wood Warblers were caught on 6 farms whose canopies were comparatively open. These data suggest that the birds encounter in Cameroon relatively stable climatic conditions for moult, and do not measurably prefer closed-canopy forests. Our findings are important, because successful moult increases survival prospects and because moult needs to be safely embedded in a migratory life cycle. Hence, information on moult timing and location is essential for identifying year-round vulnerabilities of Wood Warblers.

Ecological and evolutionary significance of molt in lowland Neotropical landbirds

AbstractThe slow-paced life history of many Neotropical birds (e.g., high survival and low fecundity) is hypothesized to increase lifetime fitness through investments in self-maintenance over reproduction relative to their temperate counterparts. Molt is a key investment in self-maintenance and is readily shaped by environmental conditions. As such, variation in molt strategies may be a key mechanism underlying life-history trade-offs and adaptation to new environments. Here, we review molt strategies from a diversity of lowland Neotropical landbirds and examine how variation in molt strategies, characterized by differences in molt insertions, timing, extent, and duration contribute to life-history variation and adaptation to diverse ecological conditions. In addition to our synthesis, we present a case study to examine the relationship between home range size and duration of the definitive prebasic molt of a well-studied subset of Amazonian landbirds. Our results suggest a connection between prolonged molt duration and larger home range size of small-to-medium-sized Amazonian landbirds. Our aims were to identify key gaps in our knowledge of Neotropical bird molt, to stimulate further comparative studies into the evolution of molt strategies, and to highlight how variation in molt strategies may be a key mechanism underlying life-history variation across latitudes.

Post-Juvenile and Post-Breeding Moult of the Black Wheatear Oenanthe leucura in South-Eastern Spain: Slowed Down Due to Climatic Aridity?

Despite increasing interest in moult in birds, there are still clear gaps in our knowledge of this topic. For example, many aspects of the moult of several European passerines remain unknown. Here, I describe the extent of the postjuvenile and the post-breeding moult of Black Wheatears Oenanthe leucura in south-eastern Spain and analyse the possible influence of ecological factors on moult in this species. The post-juvenile moult of Black Wheatears involved a variable number of greater coverts (six in most cases), but tertials, alula feathers and the carpal covert were also moulted frequently. Primaries were never moulted, while secondaries and tail feathers were moulted in 1.5% of 65 birds. The number of feathers moulted in the post-juvenile moult was not related to sex or individuals' body size. The post-breeding moult occurred between late June and mid-November and followed the typical sequence of European passerines. It had a mean duration of 145 days, with no differences between sexes or years. The body condition of wheatears did not decrease as the moult advanced. The duration of the post-breeding moult of Black Wheatears was almost double the mean duration described for European passerines and is among the longest period ever described for passerines. The resident status and medium size of the species may partly explain the long duration of the post-breeding moult, but the low seasonality and high aridity of the study area seem to be the main drivers of the pattern found.

Determinants and constraints of feather growth.

During the periodic moult of the plumage of birds, a fast regrowth of feathers would shorten the time of reduced plumage functionality. However, it has long been known that feather growth-rate is limited and that long feathers take disproportionally longer to grow than small feathers, which has severe consequences on moult duration and the completeness of moult in large birds. The reasons for the limitations of feather-growth must be related to the size and/or functions of the feather follicle, but are largely unknown. Here we measured the size of the feather follicle (taking calamus width as a proxy) and related it to parameters of feather growth (feather growth-rate by mass and by length) and feather structure (feather length, mass, massiveness [mass of feather material per mm feather-length]). We used three independent datasets which allowed for interspecific analyses, and for intraspecific comparisons of differently structured feathers within the framework of biological scaling. We found that the cross-sectional area of the calamus (as a proxy of feather follicle size) was directly proportional to feather growth-rate by mass. Hence, factors acting at a two-dimensional scale (possibly nutrient supply to the growing feather) determines feather growth rate by mass, rather than the linear arrangement of stem cells (in a circular configuration) as had previously been assumed. Feather follicle size was correlated with both feather length and massiveness, hence it seems to be adapted to some extent to feather structure. Feather growth-rate by length was dependent on both the feather material produced per unit time (growth-rate by mass) and the amount of material deposited per unit feather-length. Follicle size not only determines feather growth-rate by mass, but also directly the structural design (shape, number of barbs, etc.) of a feather. Therefore, feather growth-rate is severely constrained by the requirements imposed by the structural feather design.

Effects of Temperature on the Survival and Larval Development of Deiratonotus Japonicus (Brachyura, Camptandriidae) as a Biological Indicator

Deiratonotus japonicus (D. japonicus) inhabits isolated locations and upstream brackish waters from Kanagawa Prefecture to Okinawa Prefecture in Japan. This species faces the threat of extinction because of changing habitat conditions. Our previous studies have shown that its complete larval development from hatching to metamorphosis consists of five zoeal stages and one megalopal stage. In this study, the effect of temperature on the survival and growth of larval development in D. japonicus under controlled laboratory conditions of 13, 18, 23, 24, 25, and 26 °C was investigated by rearing larvae (30 PSU; 12:12 h light/dark cycle; fed a diet of Brachionus plicatilis rotundiformis and Artemia sp. nauplii). The survival rates and developmental periods were measured for each larval stage. The highest survival rates were obtained at 18–24 °C. Metamorphosis to megalopa occurred at 23–25 °C. There were rapid and synchronous developments at 25–26 °C but delayed and extended developments at 13 °C. The molting period decreased with increasing temperature. With decreasing temperature, the beginning of the development and duration of molting was prolonged. In addition, there were very low survival rates at 13 °C and 26 °C in all zoeal stages. Our results indicate that the early larval stages of D. japonicus are well adapted to 18–24 °C, the range observed in the estuarine marine environment of the Kita River during the breeding season. Optimum larval survival and growth were obtained at 23 °C. Temperature significantly affected the survival rate, developmental period, and molting of the larvae. The relationship between the cumulative periods of development from hatching through individual larval stages (y) and temperatures (T) was described as a power function (y = a × Tb).

Estimation of moult duration in birds with suspended moults: the case of the Red Crossbill and its relation to reproduction

Suspended moult is a relatively common phenomenon in birds, but it has remained relatively ignored for a long time in studies dealing with moulting process. Furthermore, the new and increasing number of models used to estimate moult duration systematically omit the fact that suspended moults can occur and that they significantly alter parameter estimates. Taking suspended moults into account is critical to obtain reliable moult-associated parameter estimates, which is fundamental given the demographic and evolutionary consequences of moult in birds. The main goal of this work is to develop a standardised method useful for characterising the main moulting parameters (such as the duration and starting date) of bird species that perform suspended moults. Additionally, with the aim of delving into our understanding of when and why suspended moults happen, we study their relationship with the occurrence of second breeding attempts in summer. We used data obtained from a Red Crossbill population in the Pyrenees during a period of 17 years. We observed that the percentage of crossbills undergoing suspended moult was approximately 50% during summer (July–August) and that moult suspension ultimately gives rise to a lengthened moulting period. Underhill–Zucchini models assume a time-linear replacement of feathers, overestimating the moult duration. Based on these same modelling approaches, we proposed a method to calculate the real moult duration after removing the time during which the moult was suspended. We also obtained evidence supporting the idea that crossbills suspend their moult as a strategy that could increase their breeding output in summer. The method proposed here can be used as a tool for working with species that undergo suspended moults.

Growth, molting duration and carapace hardness of blue swimming crab, Portunus pelagicus, instars at different water temperatures

Survival and growth of blue swimming crab, Portunus pelagicus from instar 1 stage to instar 8 stage (C1 to C8), molting duration and time of hardening from instar C7 to C8 were examined at 24 °C, 28 °C and 32 °C. The carapace width decreased with increasing temperature, whereas the intermolt period also decreased. The inter-molt period of crab molted from C1 to C8 was 59.23 ± 4.22 days, 48.19 ± 3.52 days, and 38.66 ± 2.15 at 24 °C, 28 °C, and 32 °C, respectively. The survival of crabs from C1-C2 stage to C7-C8 stage range from 70% to 80% and the present study showed that survival decreases at the highest temperature of 32 °C. The time spent for complete molting of crab from emergence of swimming legs to chelae was 181, 123, and 103 s, at 24 °C, 28 °C, and 32 °C, respectively. The harding time (time required for hardening) of the carapace was 16–17 h, 12–13 h, and 9–10 h at 24 °C, 28 °C, and 32 °C, respectively. It is concluded that crab instars reared at high temperature of 32 °C decrease intermolt period, duration of exuviation and harding time. Data on molting time and carapace hardiness can be used for assessing the suitable time for stocking and changing the water culture.

Breeding status influences timing but not duration of moult in the Northern FulmarFulmarus glacialis

Seabirds are key marine top predator species that are often used as indicators of the environmental quality of the oceans. Their breeding phenology has been studied extensively, but their pelagic habits mean less is known about the phenology of other events during the non‐breeding period. Here, we used miniaturized saltwater immersion light‐based geolocators (GLS) to investigate moult phenology in individuals with known breeding histories in a population of Northern FulmarFulmarus glacialisin Orkney, Scotland. As seabirds spend more time on the water during moult, moulting periods can be identified from patterns of variation in the amount of time that birds are in contact with saltwater. Estimates of daily variation in this behaviour during the non‐breeding period were based upon wet/dry sensors and then modelled to characterize the timing of the moult. Light‐based geolocation provided information on the areas used by each individual during its moult period. Inter‐individual variability in moult timing was investigated in relation to sex and breeding success in the previous summer. We found a sex difference in the location of the moult, but not in its timing. However, the timing of moult did differ between individuals that had succeeded or failed in their previous breeding attempt, with successful breeders moulting the latest. In contrast, the duration of moult did not depend on prior reproductive success, but there was evidence of inter‐annual variation in moult duration.GLSstudies have provided a step change in our understanding of the at‐sea distribution of pelagic seabirds. Our work highlights how activity data from these devices can add value to such studies by identifying key phases of the annual cycle, and locations at these times, when seabirds may be at particular risk. Furthermore, our findings indicate that individual and inter‐annual variation in breeding success may influence phenological patterns in other phases of the Northern Fulmar annual cycle.

Older birds have better feathers: A longitudinal study on the long-distance migratory Sand Martin, Riparia riparia.

Feather quality is of critical importance to long-distance migratory birds. Here, we report a series of analyses of a unique data set encompassing known-age individuals of the long-distance migratory Sand Martin (Riparia riparia). Sampling over 17 years along the Tisza River, eastern Hungary, has resulted in the recapture of numerous individuals enabling longitudinal and cross-sectional investigation of the role of adaptation to variable environmental conditions on feather morphology. We show that older individuals tend to possess better quality feathers, measured using bending stiffness, feather length and thickness as proxies. Bending stiffness and feather thickness do not change with individual age, in contrast with increases in feather length and declines in daily feather growth versus age of individual alongside moult duration. Individuals who live to older ages tend to have similar, or higher, feather growth rates and better feather quality than individuals captured at younger ages. Thus, on the basis of strong selection against individuals with slow feather growth, as seen in other species of swallows and martins, which causes a delay in moult completion, the results of this analysis highlight the potential cost of producing better quality feathers when this depends on moult duration. Feather length also does change during the lifetime of the individual and thus enabled us to further investigate influence of individual and environmental conditions during the moult. The results of this analysis provide important insights on the adaptive significance of these traits, and the potential use of physical characteristics in unravelling the reasons why long distance migratory bird populations are in global decline.

Annual Cycles of Wagtails (Passeriformes, Motacillidae) in Northwestern Siberia: Comparative Aspects

Abstract—The annual cycles of pipits and wagtails, which were studied during field and experimental observations in the Lower Ob River basin and Yamal Peninsula, have many common features. All species are similar in dates of arrival, nesting, molting, and departure onset; however, the timing of postnuptial migration and prenuptial molting differ somewhat. Positive air temperatures are an environmental factor that determines the beginning of arrival to the forest tundra and tundras. Only yellow wagtails arrive with developed gonads, while the other species require additional stimulation by a photoperiod of 24L : 0D. The reduction of some nesting stages is presumably an attempt of boreal populations to increase reproductive success. Differences in the annual cycle program are observed during the postnesting period. These variations include the timing of the onset and duration of postjuvenile and postnuptial molting, as well as the degree of overlap of postnuptial molting with nesting, the degree of overlap of the migration state with molting, photoperiodic molting conditions, and autumn migration. The intraspecific rhythm of migration in combination with environmental conditions along the migration track determines the timing of arrival to wintering sites. The threshold values of photoperiodic intervals of wintering and prenuptial molting in different species correspond to the latitude of hibernation and, possibly, determine this latitude.

Effect of molting on the concentration of plasma 25-hydroxyvitamin D in captive African penguins (Spheniscus demersus)

Feed intake and body weight are drastically altered in penguins during peri-molting period, and molting is known to affect the nutritional status of vitamin A and E. Although vitamin D status is not known in penguins during peri-molting period, vitamin D intake is supposed to be remarkably altered. The objective of the present study was to clarify the alterations in plasma 25-hydroxyvitamin D (25(OH)D) concentration, the most reliable biomarker for assessing vitamin D status, and vitamin D intake during peri-molting period. Blood samples were collected from seven adult male African penguins (Spheniscus demersus) in the control period, pre-molting period, early-molting period, and late-molting period. The dietary content of vitamin D and calcium (Ca) were higher than that of the estimated requirements. Feed intake increased in the pre-molting period and drastically decreased during the molting periods. Body weight increased in the pre-molting period, followed by the loss of weight towards the end of the experiment. Although vitamin D and Ca intakes decreased during the molting periods, plasma 25(OH)D concentration increased during the molting periods and the increase in plasma Ca concentration was also observed in the late-molting period. These results suggest that the reduction in body fat induced by reducing feed intake stimulated the release of vitamin D from body fat, which increased plasma 25(OH)D and Ca concentrations in molting penguins. Penguins are unlikely to suffer from typical hypervitaminosis D even during molting and vitamin D toxicity is not a realistic problem in penguins because of the short duration of molting.

Plumage development and moult in captive Black-bellied Sandgrouse Pterocles orientalis: age and sex variations

The sandgrouse, family Pteroclididae, are a group of birds adapted to open, arid habitats and powerful fliers but information on their plumage development and moult is scarce. In this study, the annual cycle of body plumage development, sequence and duration of primary flight feathers moult were investigated in Black-bellied Sandgrouse Pterocles orientalis, from hatching to the adult stage. Body plumage differed among juvenile, immature and subadult birds before their first breeding season. Yearling Black-bellied Sandgrouse showed three annual moults with only the pre-breeding one being complete. Juvenal body plumage was acquired shortly before the first attempts to fly at 5–6 weeks of age. The acquisition of definitive adult body plumage took place after the breeding season in late August, when birds were about 10–12 months old. The species typically replaced all primaries annually with a gradual descendent moult at a slow rate, taking 10–11 months for their completion, from December to September, including the breeding period. This study provides the first detailed analysis of flight feather development and moulting in the Black-bellied Sandgrouse, which provides useful ageing criteria based on the patterns of both primary growth and moult.

Timing and duration of primary molt in Northern Hemisphere skuas and jaegers

ABSTRACT We compared the primary molt of the 4 species of skuas and jaegers (Stercorariidae) that breed in the Northern Hemisphere: Long-tailed Jaeger (Stercorarius longicaudus), Parasitic Jaeger (S. parasiticus), Pomarine Jaeger (S. pomarinus), and Great Skua (S. skua). We analyzed primary molt data of 1,573 individuals of multiple age classes, mostly collected from photographs taken at sea but also from museum specimens and beached individuals. Whereas molt duration generally increased with species' size, molt duration in Parasitic and Pomarine jaegers was surprisingly similar given their size difference. Larger species started primary molt earlier and showed more overlap with postbreeding migration, such that there was complete overlap in Great Skua but no overlap in Long-tailed Jaeger. Within jaeger species, the first primary molt cycle took longer than later molt cycles. We suggest that, unlike birds in their first primary molt cycle, birds in their second or subsequent primary molt cycles are time-c...

Convergence of biannual moulting strategies across birds and mammals.

Birds and mammals have developed numerous strategies for replacing worn feathers and hair. Moulting usually occurs on an annual basis; however, moults that take place twice per year (biannual moults) also occur. Here, we review the forces driving the evolution of various moult strategies, focusing on the special case of the complete biannual moult as a convergence of selection pressures across birds and mammals. Current evidence suggests that harsh environmental conditions or seasonality (e.g. larger variation in temperatures) drive evolution of a biannual moult. In turn, the biannual moult can respond to secondary selection that results in phenotypic alteration such as colour changes for mate choice dynamics (sexual selection) or camouflage requirements (natural selection). We discuss the contributions of natural and sexual selection to the evolution of biannual moulting strategies in the contexts of energetics, niche selection, functionality and physiological mechanisms. Finally, we suggest that moult strategies are directly related to species niche because environmental attributes drive the utility (e.g. thermoregulation, camouflage, social dynamics) of the hair or feathers. Functional efficiency of moult may be undermined if the pace of evolution fails to match that of the changing climate. Thus, future research should seek to understand the plasticity of moult duration and phenology, especially in the context of annual cycles.

Development of Thermoregulatory Capability in Weddell Seal Pups

One of the greatest metabolic costs for endotherms is the energy allocated to thermoregulation. Weddell seals (Leptonychotes weddellii) are the southernmost breeding mammals, and as such are born into one of the most challenging thermal environments on the planet. During their nursing period, Weddell seal pups must develop the capability to survive both on the ice and in the water. Pups also concurrently shift from the use of fur to a reliance on blubber for insulation. This study examined the thermal and energetic costs associated with development and thermoregulation in Weddell seal pups. Metabolic rate (MR) in air was measured longitudinally for 4 pups every 2 weeks, starting at 1 week of age through the transition to independence (7 weeks); MR in water was measured in the same pups beginning at 3 weeks. Additionally, we assessed the molt status of each pup, and estimated body composition (blubber vs. lean mass) based on an elliptical cones model. There was a high degree of individual variability in mass‐specific MR in air in 1 week old pups (5.96–10.87 ml O2 min−1 kg−1), though in general it remained stable or decreased slightly from 1–7 weeks of age. Mass‐specific MR in water declined from 3 weeks to 7 weeks of age for 2 of the 4 pups, and remained stable for 2 pups. The difference between mass‐specific MR in air and in water also decreased from 3 to 7 weeks for 2 pups and remained steady for 2 pups; but by 5 weeks of age the difference between MR in air and in water was marginal for all 4 pups. Timing of the initiation of the molt and molt duration was also variable; two pups had molted patches by 3 weeks of age, and all but 1 pup were fully molted by 7 weeks of age. All pups gained mass from 1 to 5 weeks of age at an average rate of 2.02 ± 0.09 kg day−1 and the proportion of blubber increased from 1–3 weeks (25% to 38% of body mass). Blubber proportion remained steady from 3–5 weeks (38% to 40% of body mass) because pups gained proportionally more lean mass (61% of total mass gained). By 7 weeks, 3 of the 4 pups had weaned and were losing mass. Timing of MR equivalence in air and water did not vary with molt status (amount of lanugo) or with estimated body composition. Overall, these results indicate that Weddell seal pups have developed their thermal capabilities by ~5 weeks of age to protect themselves against increased heat loss in water, independent of the amount of lanugo fur or body composition.Support or Funding InformationThis project was funded by the National Science Foundation, Office of Polar Programs (#1543539).This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Retrospectively analysing condition in historical samples of birds

AbstractLarge amounts of nitrogen are used as fertilizer across the globe annually exceeding 100 million metric tons, with consequences for primary productivity and effects at higher trophic levels. We measured δ15N values in feathers from samples of eiders Somateria mollissima wintering on the Danish coast in 2014‐2016 and a century ago, using museum specimens. Blue mussels Mytilus edulis are filter feeders relying on phytoplankton as food and they constitute the main diet of eiders. Feather δ15N increased by 40% during the past century reflecting increased terrestrial runoff of N through agricultural use of fertilizer, in turn supporting increased primary production in shallow coastal systems. This increase in δ15N was associated with an increase in body mass and longer duration of moult. However, there was a recent decrease in the quality of feathers as reflected by more fault bars and a higher degree of feather wear suggesting that longer duration of moult comes at a cost in terms of poorer feather quality. These findings imply that terrestrial nitrogen subsidies to coastal marine systems from anthropogenic sources has profound effects on species such as the eider as revealed by the effects on body condition and plumage quality and hence the ability to fly and dive.

Primary moult of continental Black-tailed Godwits Limosa limosa limosa in the Doñana wetlands, Spain

ABSTRACTCapsule: Most Continental Black-tailed Godwits Limosa limosa limosa using the Doñana wetlands during post-breeding migration appear to begin moult before they arrive and suspend moult before they migrate onwards to West Africa.Aims: We aim to describe the primary moult strategies and patterns in the Continental Black-tailed Godwits using the Doñana wetlands, a major passage and wintering area for waterbirds in southern Spain.Methods: Individual godwits were captured, marked and their primary moult was scored in Doñana during the non-breeding season (June–March) in 2011 and 2012. Data from resightings of colour-marked godwits and birds equipped with satellite transmitters were used to estimate stopover duration during post-breeding migration (June–September) to determine if godwits move to West Africa before completing their primary moult.Results: Average primary moult duration was estimated to be 84 days ± 9 se, during 29 June–21 September and did not differ between sexes. Only 2% of individuals were observed with suspended moult. We estimated stopover duration in Doñana to be 13 days ± 2 se before migrating to West Africa.Conclusions: Most godwits stage for about two weeks in the Doñana wetlands during southward migration, moult their primaries and appear to suspend moult before crossing the Sahara. Others may complete their primary moult in Doñana, or elsewhere in Europe and overwinter in Doñana where increasing numbers of godwits have been detected in recent years. A few individuals may finish the moult in Doñana and migrate to West Africa late in the post-breeding season.

Duration and intensity of primary molt in two neotropical grasslands Passerines

La descripción de patrones y mecánica de muda de las aves ha permitido esclarecer la dinámica en ciclos de vida de especies de zonas templadas. Pocos estudios evalúan estos aspectos en aves neotropicales, dificultando su discusión funcional y evolutiva. Acá comparamos la duración de muda de primarias e intensidad de muda de vuelo en dos especies de paseriformes neotropicales, V. jacarina y S. intermedia. Desarrollamos el estudio al norte del departamento de Tolima (Colombia); capturamos las aves en un matorral y las marcamos con anillos de colores. Utilizamos los métodos de Pimm, y Rohwer y Wang para estimar la duración, y calculamos la intensidad de muda según Rohwer. La duración de muda de V. jacarina fue de 59 días (IC 95 % = 48–74) y 80 días (IC 95 % = 64–96), mientras que para S. intermedia fue de 80 (IC 95 % = 66–105) y 100 días (IC 95 % = 75–124). Estos resultados fueron consistentes con la duración de muda de paseriformes con masas similares, aunque mayores que en especies de latitudes altas, apoyando la hipótesis del bajo ritmo de vida en evaluar la duración en especies con baja captura, con muda suspendida, o baja asincronía entre individuos. La intensidad de muda fue mayor en S. intermedia (13 plumas) que en V. jacarina (9,3 plumas), resultados mayores que otros paseriformes neotropicales, que pueden representar una respuesta adaptativa a presiones ecológicas específicas.

An essential role of Rieske domain oxygenase Neverland in the molting cycle of black tiger shrimp, Penaeus monodon

Molting is an important process for development and growth in arthropods. In crustaceans, molt is regulated by ecdysteroids or molting hormones that are synthesized in Y-organs. However, ecdysteroid biosynthesis pathway in crustaceans and its participating enzymes have not been well studied so far. In this study, a Rieske domain oxygenase, the enzyme that acts as cholesterol 7,8-dehydrogenase by converting cholesterol to 7-dehydrocholesterol in the first step of the ecdysteroid biosynthesis was characterized in black tiger shrimp, Penaeus monodon. A full-length cDNA of P. monodon's Rieske domain oxygenase Neverland (PmNvd) was successfully cloned. The expression of PmNvd was dominantly found in the Y-organ, and changed during molting period. The PmNvd mRNA level was low in intermolt and early premolt stages, then dramatically increased in the mid premolt stage suggesting its role in molt regulation. The function of PmNvd in the molting process was investigated by RNAi approach. Silencing of PmNvd transcript in shrimp by specific double-stranded RNA (dsNvd) led to prolonged molt duration with abnormal molting progression, i.e. the molting process got stuck at early premolt stage. In addition, 20-hydroxyecdysone titer in the hemolymph of dsNvd-injected shrimp was significantly reduced compared with that in NaCl-injected shrimp. These evidences suggested a crucial role of PmNvd in molt progression, particularly during the initiation of premolt phase via the regulation of ecdysteroid production.