Cardiac Performance of Free-Swimming Wild Sockeye Salmon during the Reproductive Period.

Researchers have surmised that the ability to obtain dominance during reproduction is related to an individual's ability to better sequester the energy required for reproductive behaviors and develop secondary sexual characteristics, presumably through enhanced physiological performance. However, studies testing this idea are limited. Using sockeye salmon (Oncorhynchus nerka), we explored the relationship between heart rate and dominance behavior during spawning. We predicted that an individual's reproductive status and energy requirements associated with dominance can be assessed by relating routine heart rate to changes in spawning status over time (i.e., shifts among aggregation, subordinance, and dominance). Thus, we used routine heart rate as a proxy of relative energy expenditure. Heart rate increased with temperature, as expected, and was higher during the day than at night, a known diel pattern that became less pronounced as the spawning period progressed. Routine heart rate did not differ between sexes and average heart rate of the population did not differ among reproductive behaviors. At the individual level, heart rate did not change as behavior shifted from one state to another (e.g., dominance versus aggregation). No other trends existed between routine heart rate and sex, secondary sexual characteristics, survival duration or spawning success (for females only). Therefore, while our study revealed the complexity of the relationships between cardiac performance and reproductive behaviors in wild fish and demonstrated the importance of considering environmental factors when exploring individual heart rate, we found no support for heart rate being related to specific spawning behavioral status or secondary sexual characteristics.

Rendimiento Cardíaco del Salmón Rojo Salvaje que Natación Libre durante el Período ReproductivoLos investigadores han conjeturado que la capacidad de obtener dominio durante la reproducción está relacionada con la capacidad de un individuo de obtener mejor la energía requerida para los comportamientos reproductivos y desarrollar características sexuales secundarias, presumiblemente a través de un mejor rendimiento fisiológico. Sin embargo, los estudios que prueban esta idea son limitados. Usando Salmón rojo (Oncorhynchus nerka), exploramos la relación entre la frecuencia cardíaca y el comportamiento de dominación durante el desove. Predijimos que el estado reproductivo de un individuo y los requisitos de energía asociados con el dominio pueden evaluarse relacionando la frecuencia cardíaca de rutina con los cambios en el estado de desove a lo largo del tiempo (es decir, cambios entre la agregación, la subordinación y el dominio). Por lo tanto, utilizamos la frecuencia cardíaca de rutina como un proxy del gasto energético relativo. La frecuencia cardíaca aumentó con la temperatura, como se esperaba, y fue más alta durante el día que por la noche, un patrón conocido que se hizo menos pronunciado a medida que avanzaba el período de desove. La frecuencia cardíaca de rutina no difirió entre sexos y la frecuencia cardíaca promedio de la población no difirió entre los comportamientos reproductivos. A nivel individual, la frecuencia cardíaca no cambió a medida que el comportamiento cambió de un estado a otro (i.e., dominación vs. agregación). No se observaron otras tendencias entre la frecuencia cardíaca y el sexo de rutina, las características sexuales secundarias, la duración de la supervivencia o el éxito del desove (solo para hembras). Por lo tanto, si bien nuestro estudio reveló la complejidad de las relaciones entre el rendimiento cardíaco y los comportamientos reproductivos en el Salmón rojo y demostró la importancia de considerar los factores ambientales al explorar la frecuencia cardíaca individual, no encontramos respaldo para la frecuencia cardíaca relacionada con el estado conductual de desove específico o características sexuales secundarias.Translated to Spanish by J. Heras (herasj01@gmail.com).

Desempenho Cardíaco de Natação Livre em Salmão Sockeye Selvagem durante o Período ReprodutivoOs pesquisadores supuseram que a capacidade de obter dominância durante a reprodução está relacionada à capacidade de um indivíduo em melhor obter e aplicar a energia necessária para comportamentos reprodutivos e desenvolver características sexuais secundárias, presumivelmente por meio de um desempenho fisiológico aprimorado. No entanto, os estudos que testam essa ideia são limitados. Usando salmão sockeye (Oncorhynchus nerka), exploramos a relação entre a frequência cardíaca e o comportamento de dominância durante a desova.Previmos que o estado reprodutivo de um indivíduo e os requisitos de energia associados à dominância podem ser avaliados relacionando a freqüência cardíaca de rotina às mudanças no status de desova ao longo do tempo (ou seja, mudanças entre agregação, subordinação e dominância). Assim, usamos a frequência cardíaca de rotina como um indicador do relativo gasto energético. A frequência cardíaca aumentou com a temperatura, conforme o esperado, e foi maior durante o dia do que à noite, um conhecido padrão de diel que se tornou menos pronunciado à medida que o período de desova progredia. A frequência cardíaca de rotina não diferiu entre os sexos e a frequência cardíaca média da população não diferiu entre os comportamentos reprodutivos. No nível individual, a frequência cardíaca não mudou à medida que o comportamento mudou de um estado para outro (por exemplo, dominância versus agregação). Não foram observadas outras tendências entre freqüência cardíaca de rotina e sexo, características sexuais secundárias, duração da sobrevivência ou sucesso da desova (somente para mulheres). Portanto, embora nosso estudo tenha revelado a complexidade das relações entre desempenho cardíaco e comportamentos reprodutivos em peixes selvagens e demonstrado a importância de considerar fatores ambientais ao explorar a frequência cardíaca individual, não encontramos suporte que frequência cardíaca esteja relacionada ao status comportamental de desova específico ou à características sexuais secundárias.Translated to Portuguese by Diego Vaz (dbistonvaz@vims.edu).

Comparison of vegetable shortening and cocoa butter as vehicles for cortisol manipulation in Salmo trutta.

This study demonstrates that vegetable shortening and cocoa butter are two effective vehicles for intraperitoneal cortisol implants in juvenile teleosts, specifically brown trout Salmo trutta, residing in north temperate freshwater environments. Each vehicle showed a different pattern of cortisol elevation. Vegetable shortening was found to be a more suitable vehicle for long-term cortisol elevation [elevated at 3, 6 and 9 days post treatment (dpt)], while cocoa butter may be better suited for short-term cortisol elevation (only elevated at 3 dpt). Additionally, plasma cortisol levels were higher with cortisol-vegetable shortening than with cortisol-cocoa butter implants. Plasma glucose levels were elevated 6 and 9 dpt for fishes injected with cortisol-vegetable shortening, but did not change relative to controls and shams in cortisol-cocoa butter fishes. In conclusion, vegetable shortening and cocoa butter are both viable techniques for cortisol manipulation in fishes in temperate climates, providing researchers with different options depending on study objectives.

Heterospecific aggression and adaptive divergence in brook stickleback (Culaea inconstans).

Agonistic behavior between heterospecifics, in which individuals of one species attack another, may cause a subordinate species to shift resource or habitat use. Subsequent evolutionary responses to selection may mimic shifts expected under ecological character displacement, but with no role played by exploitative competition. Alternatively, aggressive behavior can evolve when fitness is improved by excluding members of a coexisting species from a defendable resource through interference. We tested whether heterospecific agonistic behavior has evolved in brook stickleback (Culaea inconstans) by comparing replicate allopatric populations to those sympatric with ninespine stickleback (Pungitius pungitius). We also tested for heritable variation in heterospecific aggressive behavior by rearing family groups in a common environment. Allopatric populations of brook stickleback were more aggressive than ninespine stickleback, suggesting that pre-existing aggression in brook stickleback contributed to niche shifts by ninespine stickleback. In addition, sympatric adult brook stickleback were more aggressive toward ninespine stickleback than brook stickleback from allopatric populations. Overt heterospecific aggressive behaviors were heritable, and aggression in juvenile brook stickleback increased with age in sympatric but not in allopatric populations reared in a common environment. Brook stickleback have evolved increased aggression when they coexist with ninespine stickleback. These stickleback communities have been structured by both evolved and pre-existing variation in heterospecific aggressive behavior in brook stickleback.