RESUMEN
We investigated chemical cues among groups of zebrafish (Danio rerio) when communicating information about the risk of predation. We found that visual cues of the predator (tiger Oscar, Astronotus ocellatus) did not increase whole-body cortisol levels in groups of zebrafish but that water conditioned by these (donor) zebrafish stressed (target) conspecifics, thereby increasing whole-body cortisol. This finding was confirmed when these zebrafish groups were in different aquaria and communicated exclusively via water transfer. This result indicates that the stress induced in the target zebrafish does not depend on an increase in whole-body cortisol levels in the donor zebrafish. Because cortisol participation is rejected in this predation-risk communication, other chemicals from the stress systems should be investigated.
Asunto(s)
Hidrocortisona/metabolismo , Conducta Predatoria/fisiología , Estrés Fisiológico , Pez Cebra/metabolismo , Animales , Hidrocortisona/fisiología , Agua , Pez Cebra/fisiologíaRESUMEN
Nile tilapia fish were individually reared under similar light levels for 8 weeks under five colored light spectra (maximum wavelength absorbance): white (full light spectrum), blue (â¼452 nm), green (â¼516 nm), yellow (â¼520 nm) or red (â¼628 nm). The effects of light on feeding, latency to begin feeding, growth and feed conversion were measured during the last 4 weeks of the study (i.e., after acclimation). We found that red light stimulates feeding, as in humans, most likely by affecting central control centers, but the extra feeding is not converted into growth.
Asunto(s)
Conducta Alimentaria/efectos de los fármacos , Peces/crecimiento & desarrollo , Peces/fisiología , Luz , AnimalesRESUMEN
Electro-olfactogram recording was used to determine whether the olfactory epithelium of adult rainbow trout is specifically sensitive to bile acids, some of which have been hypothesized to function as pheromones. Of 38 bile acids that had been pre-screened for olfactory activity, 6 were selected. The rainbow trout-specific bile acids, taurocholic acid (TCA), and taurolithocholic acid 3-sulfate (TLS) were the most potent compounds tested. TLS had a distinctive dose-response curve. Cross-adaptation experiments demonstrated that sensitivity to bile acids is attributable to at least 3 independent classes of olfactory receptor sites. Our data suggest that bile acids are discriminated by olfaction in rainbow trout, supporting the possibility that these compounds function as pheromones.
Asunto(s)
Ácidos y Sales Biliares , Mucosa Olfatoria/fisiología , Oncorhynchus mykiss/fisiología , Feromonas , Olfato/fisiología , Adaptación Fisiológica/fisiología , Animales , ElectrofisiologíaRESUMEN
Electro-olfactogram recording was used to determine whether the olfactory epithelium of adult rainbow trout is specifically sensitive to bile acids, some of which have been hypothesized to function as pheromones. Of 38 bile acids that had been pre-screened for olfactory activity, 6 were selected. The rainbow trout-specific bile acids, taurocholic acid (TCA), and taurolithocholic acid 3-sulfate (TLS) were the most potent compounds tested. TLS had a distinctive dose-response curve. Cross-adaptation experiments demonstrated that sensitivity to bile acids is attributable to at least 3 independent classes of olfactory receptor sites. Our data suggest that bile acids are discriminated by olfaction in rainbow trout, supporting the possibility that these compounds function as pheromones.