The role of F-series prostaglandins as reproductive priming pheromones in the brown trout

Abstract

Electrophysiological studies demonstrated that the olfactory epithelium of mature male brown trout Salmo trutta parr was acutely sensitive to F-series prostaglandins (PGFs) PGF 1 and PGF 2 , with detection threshold concentrations of 10 11 . The olfactory epithelium was also sensitive to the PGF metabolite 15-ketoPGF 2 (threshold 10 8 ), but did not detect a further metabolite, 13,14,-dihydro-15-ketoPGF 2 . Immature brown trout did not detect any of the prostaglandins tested. Exposure of mature male brown trout parr to waterborne PGF 1 and PGF 2 (concentration 10 8 ), resulted in significant increases in levels of expressible milt and the plasma concentrations of 17,20 -dihydroxy-4-pregnen-3-one, testosterone and 11-ketotestosterone. The olfactory epithelium of both immature and mature male brown trout parr was sensitive to the urine and ovarian fluid from ovulated female brown trout. Exposure of mature male brown trout parr to ovarian fluid resulted in an increase in the levels of plasma 17,20 -dihydroxy-4-pregnen-3-one whilst exposure to urine increased the levels of expressible milt. In addition, PGF 2 was found to be present within both the urine and ovarian fluid of mature female brown trout. It is suggested that the F-series prostaglandins have a role as priming pheromones in male brown trout. 2002 The Fisheries Society of the British Isles

Behavioural and electrophysiological responses to F‐prostaglandins, putative spawning pheromones, in three salmonid fishes

“…The PGF response threshold values in the present study are similar to those found in Atlantic salmon and Arctic charr (Moore & Waring, 1996; Sveinsson & Hara, 2000). The response threshold for PGF 2α in brown trout is also consistent with another EOG study (Moore et al ., 2002). Values of PGF detection thresholds of 10 −11 M for two catostomid species (Cardwell et al ., 1992), 10 −10 M and 10 −11 M, for common carp Cyprinus carpio L. and goldfish are also reported (Sorensen et al ., 1988; Irvine & Sorensen, 1993).…”

Effects of copper on olfactory‐mediated endocrine responses and reproductive behaviour in mature male brown trout Salmo trutta parr to conspecific females

“…Immediately after collection, blood samples were centrifuged and plasma was decanted and frozen. Plasma was later analysed for content of 11KT and 17,20β‐P by specific radioimmunoassay (RIA) as described previously (Moore et al , 2002).…”

“…PGF 2α (Sigma) was dissolved and diluted in ethanol before priming. It has been previously shown that S. trutta males exposed to PGF 2α increases their volumes of milt and sex steroid hormone levels (Moore et al , 2002). The copper‐exposed group (five fish in each tank) was exposed to 10 or 100 µg l −1 copper for 4 days before being exposed to the priming solution.…”

“…The number of tanks used in the study was restricted and, to limit the time at the hatchery, the experimental groups were composed of more than one fish at the time. On the third day of treatment, both controls and copper‐exposed fish were stripped of milt (Moore et al , 2002) and allowed to recover for 24 h after water change with new solutions. The idea was that differences in priming responses with increased milt volumes between treatments should be clearer if the fish were stripped of milt (they were set to zero).…”

“…The priming exposure was for a 5 h period. The concentration of PGF 2α was chosen based on previous studies with S. trutta (Moore et al , 2002) and was estimated to be 10 −8 M. After the priming, two to three fish were anaesthetized singularly in 0·05% 2‐phenoxyethanol. Blood and milt from all fish were sampled within c. 20 min, and alternated between exposed and control fish.…”