Effects of Habitat Complexity on Pair-Housed Zebrafish.

Sexually mature zebrafish were housed as single male-female pairs with or without plastic vegetation for 1, 5, or 10 d for comparison of whole-body cortisol measured by radioimmunoassay. Individually housed male zebrafish were used as controls. In the fish that were pair-housed without vegetation (NVeg), one animal died in 5 of 24 pairs, and one animal was alive but wounded in an additional pair. No deaths or wounds occurred in the fish that were pair-housed with vegetation (Veg). Cortisol levels did not differ between the treatment groups on day 1. On day 5, cortisol values were higher in the Veg group than in the individually housed fish (P < 0.0005) and the NVeg fish (P = 0.004). On day 10, the relationships were inversed: cortisol levels had risen in the individually housed and NVeg groups and had fallen to baseline levels in the Veg group. Cortisol values on day 10 were lower in the Veg group than in the individually housed (P = 0.004) and NVeg (P = 0.05) groups. Cortisol levels in individually housed male zebrafish increased over time. Although this study did not demonstrate a reduction in cortisol levels associated with providing vegetation, this enrichment prevented injury and death from fighting. These findings show how commonly used housing situations may affect the wellbeing of laboratory zebrafish.

Obesity impairs wound healing in ovariectomized female mice.

Obesity is increasing worldwide. Estrogen protects female mice from gaining weight in contrast to ovariectomy. Excess weight can inhibit wound healing. We determine the effects of obesity on wound healing in the presence and absence of estrogen. For this purpose, we generated (ovariectomized (OVX) and non-ovariectomized (NOVX)) lean mice by feeding a 30% calorie-restricted diet (CR), overweight mice a low-fat (LF) diet and obese mice a high-fat (HF) diet. CR mice had the lowest, LF an intermediate, and HF mice the highest body weights. OVX exacerbated weight gain in female mice. Wounds healed fastest in CR mice regardless of estrogen status. Contrastingly, wound healing in OVX obese female mice was delayed. In sum, OVX increased the propensity of gaining weight, CR mice healed wounds more rapidly than obese mice irrespective of estrogen status, and obesity in the absence of estrogen impaired wound healing.