RESUMEN
Whole-body concentrations of cortisol and glucose were measured in three-spined sticklebacks Gasterosteus aculeatus from two rivers (Rivers Ray and Ock) in southern England during a 30 month period in order to assess effects on the stress axis of (1) remediation of a wastewater treatment works (WWTW) effluent (River Ray) and (2) episodic changes in flow rate arising from periods of high rainfall (Rivers Ray and Ock). The postcapture concentrations of cortisol and glucose in fish from both rivers did not exhibit a seasonal periodicity but did show significant between-sample, between-site and between-river variation, superimposed upon a consistent downward trend for each analyte during the monitoring period. Corticosteroid and glucose concentrations following capture were inversely linked with a progressive increase in condition of the fish during this period. Site-dependent trends possibly related to exposure to the WWTW effluent were detected for both analytes in fish from the River Ray. For fish in the River Ray, a significant proportion of variation in both corticosteroid and glucose concentrations, additional to the downward trend with time, was accounted for by temporal proximity of the sample to exceptional flow events arising from episodes of high rainfall and high turbidity. This relationship was not statistically significant for fish from the River Ock. These data suggest that the responsiveness of the stress axis in free-living G. aculeatus may be altered by exposure to WWTW effluent and by exposure to physical changes in the aquatic environment such as those arising from extreme weather events. The magnitude of these effects may be increased by exposure to both stressors concurrently.
Asunto(s)
Monitoreo del Ambiente/métodos , Lluvia , Smegmamorpha/fisiología , Estrés Fisiológico , Contaminantes Químicos del Agua/efectos adversos , Animales , Glucemia , Inglaterra , Hidrocortisona/sangre , Ríos/química , Estaciones del Año , Movimientos del AguaRESUMEN
Measurement of steroids that are released into the water via the gills has previously been shown to be an effective way of studying the reproductive endocrinology of the male three-spined stickleback Gasterosteus aculeatus without having to kill the fish. In the present paper, a previous observation on the existence of a compound other than 11-ketotestosterone (11-KT) in water, which cross-reacted in the 11-KT radioimmunoassay was repeated. The amounts of this compound, however, were not sufficient to warrant a separation step prior to carrying out assay. The lack of association between androstenedione levels in water and those in plasma was also confirmed. For the first time, the amounts of testosterone released into the water were shown to be positively correlated with the amounts in plasma, the sampling procedure (placing the fish for 30 min in 50 ml water) had no effect on the rate of release of cortisol but caused a rapid drop in the rate of release of 11-KT (which means that the fish should not be sampled twice in short succession), physical interaction between two nesting males (which was accompanied by aggression) significantly increased the rate of release of 11-KT, androstenedione and testosterone (but not of cortisol) and the rate of release of 11-KT was at its maximum between 2 and 4 h after exposure.