annual cycle Dotaz Zobrazit nápovědu
Life-history theory predicts that current behaviour affects future reproduction, implying that animals should optimise their escape strategies to reflect fitness costs and benefits of premature escape. Both costs and benefits of escape may change temporally with important consequences for the evolution of escape strategies. Moreover, escape strategies of species may differ according to their positions on slow-fast pace of life gradients. We studied risk-taking in long-distance migratory animals, waders (Charadriiformes), during the annual cycle, i.e., breeding in Europe, stopover in the Middle East and wintering in tropical Africa. Phylogenetically informed comparative analyses revealed that risk-taking (measured as flight initiation distance, FID) changed significantly over the year, being lowest during breeding and peaking at stopover sites. Similarly, relationships between risk-taking and life-history traits changed among stages of the annual cycle. While risk-taking significantly decreased with increasing body mass during breeding, risk-taking-body mass relationship became marginally significant in winter and disappeared during migration. The positive trend of risk-taking along slow-fast pace of life gradient measured as adult survival was only found during breeding. The season-dependent relationships between risk-taking and life history traits suggest that migrating animals respond to fluctuating environments by adopting behavioural plasticity.
- MeSH
- chov MeSH
- migrace zvířat fyziologie MeSH
- ptáci fyziologie MeSH
- riskování MeSH
- roční období * MeSH
- rozmnožování * MeSH
- zvířata MeSH
- zvláštnosti životní historie MeSH
- Check Tag
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
The aim of the study was to investigate the seasonal variation in isokinetic strength of the knee flexors and extensors, and conventional (H/QCONV) and functional (H/QFUNC) hamstring to quadriceps strength ratios in highly trained adolescent soccer players. The players (n=11; age 17.8±0.3) were measured at the end of the competitive season (autumn), at the beginning and the end of pre-season (winter) and during the sixth week of a new competitive season. Isokinetic peak torque (concentric and eccentric) was measured at 60°·s-1 in a sitting position with the hip flexed at 100°. The testing range of motion was set from 10 - 90° of knee flexion. The players performed a set of five maximum repetitions for both the dominant and non-dominant leg. Statistically significant differences (p<0.001) between the four seasonal measurements were noted for peak torque of the dominant leg knee flexors in concentric muscle action only. A post hoc analysis revealed a statistically significant increase in peak torque from the 1st to the 4th measurement (p<0.001; d=0.692) and from the 2nd to the 4th (p<0.01; d=0.564). The differences in the changes of peak torque of the knee flexors and extensors depending on type of muscle action and tendencies found in the H/Q ratios throughout the annual training cycle indicate that strength assessment of the knee flexors and extensors and their balance throughout the annual training cycle could be beneficial for elite male adolescent soccer players both in terms of performance and risk of injury.
- Publikační typ
- časopisecké články MeSH
The aim of this study was to assess monthly testicular development in the cultured breeding stock of sterlet, Acipenser ruthenus, using histological and serum sex steroid changes. Testicular development in the adult male was examined monthly and showed four distinct phases including resting, pre-spawning, spawning and post-spawning. Also, seasonal changes of the testes were described according to its variations in gonadosomatic index (GSI) during different phases of testicular development. Using histology, we identified continuous spermatogenesis and asynchronous gonad development pattern in the testes of male sterlet, which shows that regulation of annual gonadal cycle is influenced by season. Results also showed variation in the GSI value and number of spermatogenic cells according to each season during annual cycle of gonad, as the highest value of GSI was recorded during spawning phase (spring; March-May). Hormonal profiles of 11-ketotestosterone (11-KT) showed peak, which indicated a seasonal pattern of gonadal development. The 11-KT concentration increased considerably during the spermatogenesis (pre-spawning phase) and remained quite high throughout the pre-spermiation period. In the final phase of testicular development (spawning phase), the 11-KT markedly dropped. This study undertook an examination of complete reproductive development in cultured sterlet sturgeon to provide a valuable guide for the future sterlet studies, and allows comparison of reproductive development between sturgeon species.
- MeSH
- časové faktory MeSH
- roční období MeSH
- rozmnožování fyziologie MeSH
- ryby fyziologie MeSH
- spermatogeneze MeSH
- testis anatomie a histologie diagnostické zobrazování fyziologie MeSH
- testosteron analogy a deriváty krev MeSH
- zvířata MeSH
- Check Tag
- mužské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- MeSH
- buněčný cyklus MeSH
- Escherichia coli růst a vývoj MeSH
- kultivační média MeSH
- thymin metabolismus MeSH
- Publikační typ
- kongresy MeSH
- MeSH
- histocytochemie MeSH
- ovarium metabolismus ultrastruktura MeSH
- Perciformes fyziologie MeSH
- rozmnožování * MeSH
- zvířata MeSH
- Check Tag
- ženské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
BACKGROUND: Hatching is modulated by a combination of intrinsic and extrinsic factors. Annual killifish are adapted to complete their entire life cycle in annually desiccating habitats. Spending most of their life in the embryonic stage, they have evolved adaptations to survive desiccated conditions and match their hatching with the unpredictable onset of the aquatic phase of the pool. We examined spatial and temporal synchrony of hatching in natural populations of four species of African annual killifish (genus Nothobranchius). We compared differences and variability in hatching dates among years, regions, pools, and species and matched them with data on inundations of individual pools. RESULTS: Inundations typically coincided with peak rainfall in early January. We found considerable spatial and temporal synchrony in 1 year, but less synchrony in the other 2 years. Hatching generally occurred 0-20 days after inundation; fish at most sites hatched synchronously (<1 week) but some sites showed protracted hatching or two age cohorts. One species tended to hatch earlier than the other three. CONCLUSIONS: We suggest that hatching of annual killifish in the wild is a result of the interplay between environmental conditions and individual predisposition to respond to threshold environmental cues, ensuring effective bet-hedging against unpredictable inundation. Developmental Dynamics 246:827-837, 2017. © 2017 Wiley Periodicals, Inc.
