Regulatory mechanisms for the development of the migratory phenotype: Roles for photoperiod and the gonad

Ramenofsky, Marilyn; Németh, Zoltán

doi:10.1016/j.yhbeh.2014.04.012

Cited by 33 publications

(22 citation statements)

References 84 publications

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“…As CP size is androgen-dependent [47,48], this suggests effects of androgens on a time scale appropriate for the migratory transition. Hormone manipulation experiments have provided strong evidence for the role of testosterone in initiating a spring migratory state [7–10], though details about the quantity and timing of androgen secretion necessary to activate migratory physiology and behaviour remain unresolved [61]. In particular, obligate migrants may express a migratory state in spring when circulating levels of androgens are low [62,63], including in species where testosterone has been shown to be important in stimulating migratory physiology and/or behaviour (see control groups in [8,9]).…”

Section: Discussionmentioning

confidence: 99%

Increasing photoperiod stimulates the initiation of spring migratory behaviour and physiology in a facultative migrant, the pine siskin

2018

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The transition to a migratory state involves coordinated changes in physiology and behaviour. In species with regular, predictable (obligate) migrations, increasing day length triggers the expression of a spring migratory state and androgens play an important role in stimulating its development. By contrast, we know little about the environmental cues and endocrine mechanisms that regulate migration in species with less predictable (facultative) migrations. Here, we tested whether photoperiod stimulates a migratory state in a facultative nomadic migrant, the pine siskin (Spinus pinus). We exposed wintering birds to either a naturally increasing or short-day photoperiod and measured physiological and behavioural changes indicative of a migratory state. We also examined changes in circulating hormones that may play a role in the migratory transition. Natural-day, but not short-day, birds displayed physiological preparations for migration, including increases in fat deposition, and showed increased levels of migratory restlessness. We found no evidence for a role of corticosterone in the migratory transition, but testosterone may be important. This study is the first experimental test of the role of photoperiod in regulating facultative migration and demonstrates that the predictive cue used by many obligate migrants to time spring migration is also important in a facultative migrant.

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Section: Discussionmentioning

confidence: 99%

Increasing photoperiod stimulates the initiation of spring migratory behaviour and physiology in a facultative migrant, the pine siskin

2018

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“…Pectoralis muscle score also followed a seasonal (time of year) pattern, with marked peaks during the reproductive season, although higher in the seasonal (FJ) than in the aseasonal environment (AR). At least in FJ, this could be a result of the increases in circulating androgens during the reproductive season (Ramenofsky & Nemeth, ). However, birds in AR showed an increase in pectoralis muscle despite undetectable changes in T levels (see below), which suggests that other mechanisms could be acting, such as seasonal expression of androgen receptors and metabolizing enzymes in relation to circulating androgens (see Refs).…”

Section: Discussionmentioning

confidence: 99%

Contrasting seasonal and aseasonal environments across stages of the annual cycle in the rufous‐collared sparrow, Zonotrichia capensis: Differences in endocrine function, proteome and body condition

González-Gómez

Echeverrı́a

Estades

et al. 2018

Journal of Animal Ecology

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The timing and duration of life-history stages (LHSs) within the annual cycle can be affected by local environmental cues which are integrated through endocrine signalling mechanisms and changes in protein function. Most animals express a single LHS within a given period of the year because synchronous expression of LHSs is thought to be too costly energetically. However, in very rare and extremely stable conditions, breeding and moult have been observed to overlap extensively in rufous-collared sparrows (Zonotrichia capensis) living in valleys of the Atacama Desert-one of the most stable and aseasonal environments on Earth. To examine how LHS traits at different levels of organization are affected by environmental variability, we compared the temporal organization and duration of LHSs in populations in the Atacama Desert with those in the semiarid Fray Jorge National Park in the north of Chile-an extremely seasonal climate but with unpredictable droughts and heavy rainy seasons. We studied the effects of environmental variability on morphological variables related to body condition, endocrine traits and proteome. Birds living in the seasonal environment had a strict temporal division of LHSs, while birds living in the aseasonal environment failed to maintain a temporal division of LHSs resulting in direct overlap of breeding and moult. Further, higher circulating glucocorticoids and androgen concentrations were found in birds from seasonal compared to aseasonal populations. Despite these differences, body condition variables and protein expression were not related to the degree of seasonality but rather showed a strong relationship with hormone levels. These results suggest that animals adjust to their environment through changes in behavioural and endocrine traits and may be limited by less labile traits such as morphological variables or expression of specific proteins under certain circumstances. These data on free-living birds shed light on how different levels of life-history organization within an individual are linked to increasing environmental heterogeneity.

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“…In contrast with winter, birds sampled near the time of departure had nearly completed moult with a maximal moult score of 2. Higher scores with a maximum of 9 are observed in March in both field and laboratory studies indicating heavy moult [57]. At departure, with the energetically costly moult near completion, birds were well fuelled with elevated fat levels that contributed to the observed increase in body condition.…”

Section: Discussionmentioning

confidence: 99%

“…In this case, the authors hypothesized that this change in muscle morphology may be regulated by an endogenous circannual rhythm [75]. As with red knots, white-crowned sparrows exhibited greater muscle profile during preparation for spring departure but before the appearance of nocturnal migratory restlessness and without any indication of increased daytime locomotor activity [20,57]. However, flight muscle hypertrophy and lipid deposition have been observed to occur in concert with increased flapping activity in other migratory species, such as eared grebes ( Podiceps nigricollis ) at the conclusion of the spring stopover en route to breeding grounds [25].…”

Section: Discussionmentioning

confidence: 99%

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Altered expression of pectoral myosin heavy chain isoforms corresponds to migration status in the white-crowned sparrow (Zonotrichia leucophrys gambelii)

2016

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Birds undergo numerous changes as they progress through life-history stages, yet relatively few studies have examined how birds adapt to both the dynamic energetic and mechanical demands associated with such transitions. Myosin heavy chain (MyHC) expression, often linked with muscle fibre type, is strongly correlated with a muscle's mechanical power-generating capability, thus we examined several morphological properties, including MyHC expression of the pectoralis, in a long-distance migrant, the white-crowned sparrow (Zonotrichia leucophrys gambelii) throughout the progression from winter, spring departure and arrival on breeding grounds. White-crowned sparrows demonstrated significant phenotypic flexibility throughout the seasonal transition, including changes in prealternate moult status, lipid fuelling, body condition and flight muscle morphology. Pectoral MyHC expression also varied significantly over the course of the study. Wintering birds expressed a single, newly classified adult fast 2 isoform. At spring departure, pectoral isoform expression included two MyHC isoforms: the adult fast 2 isoform along with a smaller proportion of a newly present adult fast 1 isoform. By spring arrival, both adult fast isoforms present at departure remained, yet expression had shifted to a greater relative proportion of the adult fast 1 isoform. Altering pectoral MyHC isoform expression in preparation for and during spring migration may represent an adaptation to modulate muscle mechanical output to support long-distance flight.

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Regulatory mechanisms for the development of the migratory phenotype: Roles for photoperiod and the gonad

Cited by 33 publications

References 84 publications

Increasing photoperiod stimulates the initiation of spring migratory behaviour and physiology in a facultative migrant, the pine siskin

Increasing photoperiod stimulates the initiation of spring migratory behaviour and physiology in a facultative migrant, the pine siskin

Contrasting seasonal and aseasonal environments across stages of the annual cycle in the rufous‐collared sparrow, Zonotrichia capensis: Differences in endocrine function, proteome and body condition

Altered expression of pectoral myosin heavy chain isoforms corresponds to migration status in the white-crowned sparrow (Zonotrichia leucophrys gambelii)

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