Muscle mercury and selenium in fishes and semiaquatic mammals from a selenium-deficient area.

The aim of this study was to investigate and compare total mercury (Hg), selenium (Se), and Se:Hg molar ratios in fish muscles (phytophages n=3; benthophages n=32; predators n=5) and semiaquatic carnivores, including piscivores (the European otter n=8, the feral American mink n=7) and the omnivorous raccoon (n=37) from a riverine European ecosystem in a Se-deficient area. The Hg concentration in fish reached 0.337µg/g dry weight, dw (0.084µg/g wet weight, ww). We found significant differences among Hg levels in tested vertebrate groups (predators vs benthophages: 0.893 vs 0.281µg/g; piscivores vs omnivores: 6.085 vs 0.566µg/g dw). Fish groups did not differ in Se concentrations, with a mean value of 0.653µg/g dw. Significant differences were revealed between Se levels in piscivorous and omnivorous carnivores (0.360 vs 0.786µg/g dw, respectively). Fish Se:Hg molar ratio values were >2.2. Benthophages had higher the ratio than predators but similar to phytophages. Among carnivores, piscivores had much lower the ratio than raccoon (0.14 vs 3.75) but raccoon and fish medians did not significantly differ. We found almost two times higher Se levels in fish and raccoons compared to piscivores, possibly resulting from lower fish Se digestibility by piscivores in contrast to higher absorption of plant Se by many fish and omnivorous raccoons. Considering that a tissue Se:Hg molar ratio <1 may be connected with a Hg toxicity potential increase, we assume that piscivores in Se-deficient area are in worse situation and more exposed to Hg than fish and omnivores.

Phytosterols act as endocrine and metabolic disruptors in the European polecat (Mustela putorius).

Phytosterols or plant sterols (PS) are consumed as natural remedies and margarines by the general population in developed countries to lower elevated serum cholesterol levels. They are also present in high concentrations in pulp mill effluents. The aim of the study was to screen the endocrine and metabolic parameters of the European polecat (Mustela putorius) for the effects of PS. The results showed an increase in the plasma estradiol and TH levels with no effects on the hypophyseal regulatory hormones. The plasma ghrelin levels decreased. PS also affected intermediary metabolism. The liver glycogen content increased as did the kidney glucose-6-phosphatase activity. The liver lipase esterase activity, on the other hand, decreased due to PS. In serum lipids the total cholesterol did not change, but the low-density lipoprotein levels increased and the high-density lipoprotein-cholesterol ratio decreased. PS had widespread previously unreported effects on the physiology of the polecat. The multiple effects indicate the need of a thorough risk assessment of the effects and interactions of PS.

Use of a raw meat-based diet or a dry kibble diet for sand cats (Felis margarita).

Limited information is available on the utilization of different types of diets by captive exotic felid species. Utilization of diets by small exotic felids may differ depending on the diet fed. Eight sand cats (Felis margarita), which are small, 2- to 4-kg cats, were used to examine the digestibility of two types of diets: a raw meat-based diet and a dry kibble diet. Dry matter, crude protein and energy intakes and digestibilities were evaluated. Digestibilities for dry matter, energy, and crude protein were 83.5 +/- 4.8, 89.6 +/- 5.2, 92.4 +/- 5.3% for the raw meat-based diet and 72.7 +/- 12.3, 76.8 +/- 14.5, and 77.9 +/- 13.5% for the kibble diet. Physiological variables also were examined and included plasma taurine, vitamin A, retinyl palmitate, beta-carotene, calcium, and phosphorus. Plasma taurine means were 91.4 +/- 8.4 mumol/L in cats consuming the raw meat-based diet and 248.0 +/- 23.2 mumol/L in cats consuming the kibble diet. Plasma phosphorus was 5.2 +/- .1 and 4.5 +/- .1 mg/dL, respectively, in cats consuming raw meat-based and kibble diets. beta-Carotene was 25.2 +/- 2.9 and 2.9 +/- .3 micrograms/dL, respectively, for cats consuming the raw meat-based and kibble diets. These results indicate that diets formulated for small captive exotic felid species should be evaluated with respect to diet type and nutrient utilization.

Immunocytochemical localization of hypothalamic luteinizing hormone-releasing hormone in male ferrets.

LHRH-containing neurons within the hypothalamus were immunocytochemically identified in adult male ferrets that were either gonadally intact, castrated, or castrated and treated with testosterone. The distribution of LHRH-immunopositive neuron cell bodies was similar in the three treatment groups. The majority of these cells was located mediobasally in the retrochiasmatic area, including some within the ventrolateral aspects of the arcuate nucleus. These soma were associated with a dense basal LHRH fiber plexus which extended to the median eminence. A smaller number of cell bodies was found slightly more dorsal and lateral to the major concentration at the base and midline. Isolated LHRH perikarya were occasionally observed in dorsal areas of the hypothalamus. There were no differences in the mean total number of hypothalamic LHRH cell bodies identified in the three treatment groups. These results indicate that the documented negative feedback effects of testosterone on LH secretion in male ferrets are not the result of an alteration in the absolute number of neurons capable of synthesizing LHRH.

Selenium accumulation in mammals exposed to contaminated California irrigation drainwater.

In May 1984, 332 mammals of 10 species were collected at Kesterson Reservoir (San Joaquin Valley, Merced Co., CA), which had received selenium-laden irrigation drainwater, and at the nearby Volta Wildlife Area, which had not. The study concentrated on the California vole (Microtus californicus); 88 were taken at Kesterson, 89 at Volta. Mean selenium concentrations in livers were as much as 522 times higher at Kesterson. There were species-to-species differences at Kesterson; higher selenium concentrations occurred in carnivorous species and/or species that feed on foods closely linked to pond water. There were also pond-to-pond differences at Kesterson; drainwater historically was delivered to Ponds 1 and 2, where concentrations in 1984 were higher, with subsequent flow to other ponds, where they were lower. Whereas none of 50 adult female voles from Kesterson was pregnant, 12 of 41 (29%) from Volta were pregnant. However, this cessation of reproductive activity at Kesterson was probably not due to selenium toxicity but could have resulted because drying conditions at Kesterson forced voles to a seed diet earlier than at Volta. One malformation was found among five embryonic litters of three species from Kesterson. Mammals seem much less susceptible to selenium-induced embryonic abnormalities than birds. No adverse impacts of selenium on wild mammals were demonstrated; however, some sensitive species might have been extirpated from Kesterson before this study began. In addition, high concentrations in small mammal species at Kesterson may threaten predatory birds and mammals that feed on them, with the endangered San Joaquin kit fox (Vulpes macrotis mutica) of particular concern.