Abstract Agonistic interactions in most animals reflect individual social experience and nutritio... more Abstract Agonistic interactions in most animals reflect individual social experience and nutritional status. Crustaceans establish social hierarchies in which dominant individuals tend to be largest, most aggressive, and have the greatest access to resources such as mates, shelter, and food. Subordinates, on the other hand, are smaller and lack access to resources. However, to become dominant, individuals must grow, a process that requires nutrients. Crustacean grow through a process known as molting, where animals shed their external skeleton and rebuild a larger carapace. During molt, animals are very vulnerable to predators and potential competitors. Thus, an animal must balance the potential benefit of growth with the risk of injury resulting from agonistic interactions during molting. In this study we asked how being in a social group influences molting behavior. The crayfish Orconectes obscurus were isolated for 7 days and then placed into either an individual tank or into a tank with 2 same-sex crayfish. Interactions in group tanks were recorded and analyzed to determine social status of each individual. Animals were observed daily for 30 days to note movement patterns and molts. Although dominant individuals typically have greater access to limited resources required for molting and would theoretically molt sooner and more frequently than subordinates, when food was equally available to all individuals, subordinates actually molted sooner and more frequently than dominant individuals. Additionally, there was a seasonal effect in which the molt rate and frequency was greatest in the summer. These findings suggest that sociality and seasonality strongly influence molting behavior in crustaceans.
Communication signals are shaped by the opposing selection pressures imposed by predators and mat... more Communication signals are shaped by the opposing selection pressures imposed by predators and mates. A dynamic signal might serve as an adaptive compromise between an inconspicuous signal that evades predators and an extravagant signal preferred by females. Such a signal has been described in the gymnotiform electric fish, Brachyhypopomus gauderio, which produces a sexually dimorphic electric organ discharge (EOD). The
Résumé/Abstract The communication signals of electric fish can be dynamic, varying between the se... more Résumé/Abstract The communication signals of electric fish can be dynamic, varying between the sexes on a circadian rhythm and in response to social and environmental cues. In the gymnotiform fish Brachyhypopomus gauderio waveform shape of the electric organ ...
The hypothalamic-pituitary-adrenal/interrenal axis couples serotonergic activity in the brain to ... more The hypothalamic-pituitary-adrenal/interrenal axis couples serotonergic activity in the brain to the peripheral regulators of energy balance and response to stress. The regulation of peripheral systems occurs largely through the release of peptide hormones, especially the melanocortins (adrenocorticotropic hormone [ACTH] and alpha melanocyte stimulating hormone [α–MSH]), and beta-endorphin. Once in circulation, these peptides regulate a wide range of processes; α–MSH in particular regulates behaviors and physiologies with sexual and social functions. We investigated the role of the HPI and melanocortin peptides in regulation of electric social signals in the gymnotiform electric fish, Brachyhypopomus pinnicaudatus. We found that corticotropin releasing factor, thyrotropin-releasing hormone, and α–MSH, three peptide hormones of the HPI/HPA, increased electric signal waveform amplitude and duration when injected into free-swimming fish. A fourth peptide, a synthetic cyclic-α–MSH analog attenuated the normal circadian and socially-induced EOD enhancements in vivo. When applied to the electrogenic cells (electrocytes) in vitro, only α–MSH increased the amplitude and duration of the electrocyte discharge similar to the waveform enhancements seen in vivo. The cyclic-α–MSH analog had no effect on its own, but blocked or attenuated α–MSH-induced enhancements in the single-cell discharge parameters, demonstrating that this compound functions as a silent antagonist at the electrocyte. Overall, these results strongly suggest that the HPI regulates the EOD communication signal, and demonstrate that circulating melanocortin peptides enhance the electrocyte discharge waveform.
Abstract Agonistic interactions in most animals reflect individual social experience and nutritio... more Abstract Agonistic interactions in most animals reflect individual social experience and nutritional status. Crustaceans establish social hierarchies in which dominant individuals tend to be largest, most aggressive, and have the greatest access to resources such as mates, shelter, and food. Subordinates, on the other hand, are smaller and lack access to resources. However, to become dominant, individuals must grow, a process that requires nutrients. Crustacean grow through a process known as molting, where animals shed their external skeleton and rebuild a larger carapace. During molt, animals are very vulnerable to predators and potential competitors. Thus, an animal must balance the potential benefit of growth with the risk of injury resulting from agonistic interactions during molting. In this study we asked how being in a social group influences molting behavior. The crayfish Orconectes obscurus were isolated for 7 days and then placed into either an individual tank or into a tank with 2 same-sex crayfish. Interactions in group tanks were recorded and analyzed to determine social status of each individual. Animals were observed daily for 30 days to note movement patterns and molts. Although dominant individuals typically have greater access to limited resources required for molting and would theoretically molt sooner and more frequently than subordinates, when food was equally available to all individuals, subordinates actually molted sooner and more frequently than dominant individuals. Additionally, there was a seasonal effect in which the molt rate and frequency was greatest in the summer. These findings suggest that sociality and seasonality strongly influence molting behavior in crustaceans.
Communication signals are shaped by the opposing selection pressures imposed by predators and mat... more Communication signals are shaped by the opposing selection pressures imposed by predators and mates. A dynamic signal might serve as an adaptive compromise between an inconspicuous signal that evades predators and an extravagant signal preferred by females. Such a signal has been described in the gymnotiform electric fish, Brachyhypopomus gauderio, which produces a sexually dimorphic electric organ discharge (EOD). The
Résumé/Abstract The communication signals of electric fish can be dynamic, varying between the se... more Résumé/Abstract The communication signals of electric fish can be dynamic, varying between the sexes on a circadian rhythm and in response to social and environmental cues. In the gymnotiform fish Brachyhypopomus gauderio waveform shape of the electric organ ...
The hypothalamic-pituitary-adrenal/interrenal axis couples serotonergic activity in the brain to ... more The hypothalamic-pituitary-adrenal/interrenal axis couples serotonergic activity in the brain to the peripheral regulators of energy balance and response to stress. The regulation of peripheral systems occurs largely through the release of peptide hormones, especially the melanocortins (adrenocorticotropic hormone [ACTH] and alpha melanocyte stimulating hormone [α–MSH]), and beta-endorphin. Once in circulation, these peptides regulate a wide range of processes; α–MSH in particular regulates behaviors and physiologies with sexual and social functions. We investigated the role of the HPI and melanocortin peptides in regulation of electric social signals in the gymnotiform electric fish, Brachyhypopomus pinnicaudatus. We found that corticotropin releasing factor, thyrotropin-releasing hormone, and α–MSH, three peptide hormones of the HPI/HPA, increased electric signal waveform amplitude and duration when injected into free-swimming fish. A fourth peptide, a synthetic cyclic-α–MSH analog attenuated the normal circadian and socially-induced EOD enhancements in vivo. When applied to the electrogenic cells (electrocytes) in vitro, only α–MSH increased the amplitude and duration of the electrocyte discharge similar to the waveform enhancements seen in vivo. The cyclic-α–MSH analog had no effect on its own, but blocked or attenuated α–MSH-induced enhancements in the single-cell discharge parameters, demonstrating that this compound functions as a silent antagonist at the electrocyte. Overall, these results strongly suggest that the HPI regulates the EOD communication signal, and demonstrate that circulating melanocortin peptides enhance the electrocyte discharge waveform.
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Papers by Anya Goldina