Vitamin D3 intoxication in naked mole-rats (Heterocephalus glaber) leads to hypercalcaemia and increased calcium deposition in teeth with evidence of abnormal skin calcification.

Naked mole-rats have no access to obvious sources of vitamin D and therefore have an impoverished vitamin D status. In an investigation into the effects of vitamin D supplementation, inadvertently supraphysiological doses of 130,000 times the normal dose of vitamin D were administered. Within 5 days animals appeared lethargic, with reduced food intake. All but one of the seven animals were killed and blood was collected. Plasma vitamin D metabolites 25(OH)D and 1,25(OH)2D and calcium were determined. Both vitamin D metabolite concentrations exceeded the upper limits of sensitivity of the assays (> 100 ng/ml 25(OH)D and > 210 pg/ml 1,25(OH)2D). Active calcium uptake in the intestine was evident along with concomitant increases in calcium concentration in plasma, bone, and teeth. The remaining animal survived, but showed scab-like formations in the skin around the lower jaw and along the nipple line. X-ray analyses revealed calcium deposition in these cornified regions, although there was no evidence of metastatic calcification in other tissues. Deposition of excess calcium in skin that is regularly sloughed off and in teeth that are continuously worn down and replaced may reduce the vitamin D-induced hypercalcaemia and thus alleviate the effects of vitamin D intoxication.

Steroid hormones and agonistic behavior in a cichlid teleost, Aequidens pulcher.

The effects of three steroid hormones on the agonistic behavior of female Aequidens pulcher have been evaluated. Testosterone, estradiol, and cortisol were tested using an immersion technique to minimize trauma, and we also examined metyrapone, a blocker of cortisol biosynthesis. Two different experimental protocols were employed, the first investigating agonistic interactions within groups of fish, and the second examining the responses of isolated fish to models and mirrors. Differences between replicates were small, and both protocols supported similar conclusions. Each of the three hormones produced a characteristically different spectrum of behaviors when compared to the controls. Testosterone increased agonistic behavior in all experimental situations, while estradiol had a generally opposite effect; this may reflect the natural modulation of behavior by hormones during the reproductive cycle of A. pulcher. Cortisol also had distinct behavioral effects; available evidence suggests that this steroid increases submissive components of agonistic behavior, and that observed increases in some aggressive components are an indirect consequence, dependent upon the feedback of social information received by each fish. Metyrapone treatment greatly reduced all agonistic behaviors, groups of fish forming shoals typical of juveniles. This was not reversed by replacement therapy with cortisol, which suggests that metyrapone affects behavior by an alternative, possibly toxic, mechanism.