Seasonal changes in plasma steroid levels in relation to ovarian steroidogenic ultrastructural features and progesterone receptors in the house gecko, Hemidactylus flaviviridis, in Oman.

A comprehensive study of the annual ovarian cycle in the house gecko, Hemidactylus flaviviridis, was conducted in Oman. Circulating estradiol (E(2)), progesterone (P), and testosterone (T) were measured during the active and inactive phases of the cycle. The steroid levels were related to the steroidogenic ultrastructural features such as the abundance of smooth endoplasmic reticulum (SER), the presence of cisternal whorls, and close association of lipid droplets with swollen vesiculated mitochondria and SER. The steroids were measured using a sensitive detection technique HPLC-MS/MS. E(2) levels began to rise in January at the onset of vitellogenesis and continued to rise between February and May relative to ovulation, postovulation, gravidity and oviposition. Afterwards, E(2) remained low during the inactive phase (June-December). P levels increased significantly in March and peaked in April, which coincided with luteinization. P levels began to decline relative to luteolysis (May-June). Afterwards, it remained low throughout the inactive phase. T levels rose significantly in March-April coinciding with vitellogenesis, but decreased rapidly and significantly in May and remained low during the inactive phase. Progesterone receptors (PR), identified using immunohistochemistry, were strongly expressed during the breeding period, but were absent during the non-breeding period. The appearance of the steroidogenic ultrastructural features in the preovulatory and lutein granulosa cells was correlated with the significant rise in the three steroid levels and the PR. As the steroid levels declined, the granulosa cells underwent a general degeneration and disruption of the associated steroidogenic features.

The effects of diclofenac on the physiology of the green shore crab Carcinus maenas.

In recent years there has been increasing concern regarding the influx of pharmaceuticals into aquatic environments. One group of pharmaceuticals that has been identified as being of particular concern are the non-steroidal anti-inflammatory drugs (NSAIDs). This study examined the effects of one of the most commonly reported NSAID contaminants, diclofenac, on the physiology of Carcinus maenas. Two environmentally realistic concentrations were examined in this study (10 ng/l and 100 ng/l) at two salinities (35 and 17.5 psu). Female and male crabs were exposed to these two concentrations for 7 days. Following exposure, haemolymph samples were taken from the animals. Measurements were taken for oxyhaemocyanin and lactate concentrations. The effects of this compound on osmoregulatory capacity (OC) in C. maenas were also measured. Exposure to diclofenac had no significant effect on haemolymph lactate and oxyhaemocyanin concentrations suggesting that exposure to this compound does not elicit a stress response in this species. However, exposure to this pharmaceutical did have significant effects on both the OC and the haemolymph osmolality in C. maenas. At both salinities the data suggests that the osmoregulatory ability of C. maenas is impaired when exposed to diclofenac.

The effects of a synthetic pyrethroid pesticide on some aspects of reproduction in Atlantic salmon (Salmo salar L.).

The synthetic pyrethroid pesticide cypermethrin, a known contaminant of tributaries supporting spawning salmonid fish, had a significant sublethal impact upon the pheromonal mediated endocrine system in mature male Atlantic salmon (Salmo salar L.) parr. Previous studies have demonstrated that ovulated female salmon release a priming pheromone in their urine (considered to be the F-type prostaglandin, PGF(2alpha) which is subsequently detected by the olfactory system of mature male salmon parr and results in increased levels of plasma sex steroids and expressible milt. Exposure of mature male parr for a 5 day period to a water concentration of < 0.004 microg l(-1) cypermethrin significantly reduced or inhibited the olfactory response to PGF(2alpha). In addition, exposure of male parr to cypermethrin significantly reduced their ability to respond to the priming effect of the pheromone. The priming effect on milt and plasma 17,20beta-dihydroxy-4-pregnen-3-one levels were abolished at water concentrations of < 0.004 and 0.028 microg l(-1)cypermethrin, respectively. The effect of cypermethrin on the priming response did not appear to be due to a direct effect on the testes, since the ability of testes to respond to pituitary extract stimulation in vitro was not impaired in males exposed to cypermethrin. In addition, exposure of salmon milt and eggs to a concentration of 0.1 microg l(-1) cypermethrin during fertilisation subsequently reduced the number of fertilised eggs. The results of the study suggest that low levels of cypermethrin in the aquatic environment may have a significant effect on Atlantic salmon populations through disruption of reproductive functions.

Plasma and tissue thyroxine and triiodothyronine contents in sublethally stressed, aluminum-exposed brown trout (Salmo trutta).

Immature female brown trout, Salmo trutta, were exposed to pH 5.0 soft water in the presence or absence of aluminum (Al) at 12.5 micrograms liter-1 and their plasma concentrations and tissue contents of thyroxine (T4) and triiodothyronine (T3) were compared with those of a control group of trout held in pH 7.0 soft water. After 120 hr, plasma cortisol, glucose, T4, and T3 concentrations were greater in the Al-exposed trout than in trout exposed to acid conditions alone, indicating that although the Al conditions were sublethal, a significant stress response was elicited. Significant increases in liver T4 content, liver 5'-monodeiodinase activity and liver T3 content indicated increased hepatic T4 to T3 conversion in the Al-exposed trout. The T4 contents of brain, gill filaments, white muscle, heart ventricle, caudal kidney, and ovary were not significantly altered by Al exposure. The T3 content of caudal kidney and ovary were significantly lower in Al-exposed trout than in control fish in neutral water but were unchanged in the brain, gill filaments, heart ventricle, and white muscle of these trout. The present data support previous observations of increased plasma T3 concentrations in sublethally Al-exposed brown trout and indicate that at least part of the increased plasma T3 concentration is due to an increased hepatic uptake of T4 and monodeiodination to T3. However, analysis of nonhepatic tissue T3 content gave no indication of increased T3 production by these tissues.

Milt and endocrine responses of mature male Atlantic salmon (Salmo salar L.) parr to water-borne testosterone, 17,20 beta-dihydroxy-4-pregnen-3-one 20-sulfate, and the urines from adult female and male salmon.

Mature male Atlantic salmon (Salmo salar L.) parr responded to the urine from ovulated females with significant increases in plasma gonadotropin II, 17,20 beta-dihydroxy-4-pregnen-3-one, testosterone, and 11-ketotestosterone concentrations and volumes of expressible milt. There were also significant increases in biliary free steroid and steroid conjugate concentrations. Urine from mature adult male salmon also affected male parr, which responded with increased plasma gonadotropin II concentrations and expressible milt. However, male urine did not elevate the plasma and bile concentrations of any of the steroids. When two of the three known steroids which are detected by the mature male salmon parr olfactory epithelium were tested for priming activity, results showed that these compounds had little or no activity when added to the water. Only plasma gonadotropin II concentrations increased in mature male parr exposed to 17,20 beta-dihydroxy-4-pregnen-3-one 20-sulfate. Female and mature adult male urines contain at least one priming pheromone and there was no conclusive evidence for this priming pheromone being one of the tested steroids. However, the fact that water-borne 17,20 beta-dihydroxy-4-pregnen-3-one 20-sulfate can have a physiological effect in male parr suggests that it may have a role as one of a mixture of compounds in female urine that males detect and respond to. The lack of a priming-like effect of testosterone supports a previous hypothesis that the major pheromonal role of this steroid is as an attractant for mature male salmon parr.

Plasma prolactin, cortisol, and thyroid responses of the brown trout (Salmo trutta) exposed to lethal and sublethal aluminium in acidic soft waters.

Brown trout, with indwelling dorsal aortic cannulae, were exposed to various concentrations of aluminium (Al; 50 micrograms liter-1, 100% mortality over 48 hr; 25 micrograms liter-1, 50% mortality over 120 hr; 12.5 micrograms liter-1, 0% mortality over 120 hr) in acidic (pH 5.0) soft water. The plasma concentrations of prolactin (PRL), cortisol, thyroxine (T4), and triiodothyronine (T3) were monitored. Plasma PRL concentrations were transiently depressed (to less than 20% of resting concentrations) after 12 hr in trout in the two highest water Al concentrations, but were unchanged in the trout exposed to 12.5 micrograms liter-1 Al. Plasma cortisol concentrations were elevated in response to all water Al levels and remained elevated in trout in the lethal conditions. The sublethally exposed trout showed a recovery in plasma cortisol concentrations by 120 hr. Plasma T4 concentrations were significantly elevated in trout exposed to both the lethal and the sublethal Al concentrations (from mean resting concentrations of 1-2 ng ml-1 to peaks of 8.9 and 9.0 ng ml-1 in the 50 and 12.5 micrograms liter-1 Al groups, respectively), although a recovery in plasma concentrations was evident in the sublethally exposed trout from 72 hr onwards. Plasma T3 concentrations were relatively stable in the trout exposed to the two highest doses of Al, whereas the trout under the lowest, sublethal, Al conditions exhibited a sustained (12-72 hr) elevation in plasma T3 concentrations (from a mean resting concentration of 0.9 ng ml-1 to a peak of 4.2 ng ml-1 at 48 hr). No clear relationship was apparent between the plasma PRL concentrations and the previously reported ionoregulatory status of the trout.

The impact of sewage sludge exposure on the reproduction of the sand goby, Pomatoschistus minutus.

Adult sand gobies were exposed to 0.1% sewage sludge for 19 weeks prior to the end of spawning. Exposure to sewage sludge had a significant effect on male mortality rates but no significant effects on the gonadosomatic index of males or females. There were no major effects of sludge exposure on testes androgen content or on testes release of androgens after in vitro gonadotrophin stimulation. Fecundity and the number of larvae produced were not significantly affected by the sludge exposure. There was a tendency for eggs and larvae from sludge-exposed females to have a higher mortality rate. At a population level, however, there was a major reduction in the number of eggs and larvae produced in the sludge-exposed population which reflected a failure of some females to spawn. Of the larvae produced, 60-70% from sludge-exposed parents were lighter and had a larger yolk-sac volume compared to larvae from non-exposed parents which may have indicated impaired yolk utilisation.

Ionoregulatory and respiratory responses of brown trout, Salmo trutta, exposed to lethal and sublethal aluminium in acidic soft waters.

Soft water acclimated (Ca(2+) 0.02 mM; Na(+) 0.03 mM; K(+) 0.01 mM; pH 7.0), cannulated brown trout (Salmo trutta) were exposed to various pH and aluminium (Al) regimes (pH 7.0, pH 5.0, pH 5.0 plus Al: 50, 25, and 12.5 µg l(-1)) for up to 5 days in order to determine (i) the sublethal concentration of Al at pH 5.0 for this species (ii) their ionoregulatory and respiratory status. No mortality or physiological disturbances were evident at pH 7.0 or pH 5.0. All trout died within 48 h at pH 5.0 in the presence of Al at 50 µg l(-1) and 67% died over the 5 day period at pH 5.0 in the presence of Al at 25 µg l(-1). Fish at these lethal Al concentrations showed significant decreases in arterial blood oxygen content (CaO2) but no changes in plasma osmolarity or the concentrations of plasma Na(+), K(+) and Cl(-). Physiological disturbance was more marked at the 50 µg l(-1) Al concentration. The surviving fish at 25 µg l(-1) showed few signs of physiological recovery while continually exposed to this regime. No fish died during the exposure to water of pH 5.0 containing 12.5 µg l(-1) Al, but physiological disturbance was still apparent. These sublethally-stressed trout showed a transient decline in the plasma concentrations of Na(+) and Cl(-1). Although CaO2 decreased, recovery was evident. The data suggest that in the brown trout, environmental Al concentration is as important as pH and calcium concentration in determining the physiological status of the fish.