Sexual dimorphism in an under-ice spawning fish: the burbot (Lota lota)

Sexual dimorphic characteristics arise in response to differing selective pressures on the sexes and can be used to attract mates or signal reproductive readiness. How sexual dimorphism is expressed where visual cues may be of limited use is an underexplored aspect of reproductive ecology. The burbot (Lota lota (L., 1758)) is a common boreal fish that is not overtly sexually dimorphic. It spawns mid-winter in a light-limited under-ice environment. We examined a variety of morphological and reproductive characteristics in burbot from a northern lake over one full year to assess both seasonal and sex-based variation. Spawning occurred under ice in early February. Seasonal variation was more pronounced in females for many of the traits examined. Growth, fin lengths, swim bladder mass, and liver lipid concentration did not differ between the sexes. Male burbot had significantly higher body condition, larger gas glands, and smaller livers. Males also had significantly larger gonads than females, unusual for boreal fishes. The high gonadal investment of male burbot suggests that sperm competition may be intense in this species. This study demonstrates that sexual dimorphism can be subtle and is present in a seemingly monomorphic species—the burbot.

Saturated fat-rich diet increases fetal lipids and modulates LPL and leptin receptor expression in rat placentas

Metabolic alterations in obese and overweight mothers impact the placenta and the fetus, leading to anomalies in fetal growth and lipid accretion. The primary aim of the study was to examine the effect of a saturated fat-rich diet (FD) on growth, lipid accretion, and lipases, leptin and leptin receptor (ObR) expression in the placenta and fetal liver. We also aimed to find a role for fetal leptin in the modulation of placental and fetal liver lipase and ObR expression. Six-week-old rats were fed with a standard rat chow (control) or a 25% FD for 7 weeks until mating and during pregnancy. Also, in a group of control rats, fetuses were injected with leptin on days 19, 20, and 21 of pregnancy. On day 21, we assessed lipidemia, insulinemia, and leptinemia in mothers and fetuses. In the placenta and fetal liver, lipid concentration was assessed by thin layer chromatography (TLC) and the gene expression of lipoprotein lipase (LPL), endothelial lipase, insulin receptor (Insr), leptin, and ObR by RT-PCR. The FD induced hypertriglyceridemia and hyperleptinemia (P<0.01) in mothers and fetuses, an increase in maternal (P<0.05) and fetal weight (P<0.01), overaccumulation of lipids in fetal liver (P<0.01), and enhanced leptin expression in the placenta and fetal liver (P<0.05). Placental expression of IR and LPL was increased (P<0.05), and ObR decreased (P<0.05) in the FD group. Fetal administration of leptin induced the placental and fetal liver downregulation of ObR (P<0.05) and upregulation of LPL expression (P<0.05). The FD led to increased fetal lipid levels, which may result from high maternal lipid availability and fetal leptin effects.

An attempt to distinguish between the direct and indirect effects, in the laying domestic fowl, of added dietary copper sulphate

1. An experiment is reported in which the effects of giving copper sulphate-supplemented diets and control unsupplemented pair-fed diets to laying hens were compared.2. The level of food intake significantly adversely affected mean body-weight, egg number, egg weight, liver, kidney, oviduct and ovary weights. Gizzard weight/kg body-weight was significantly increased both with decreasing levels of food intake and increased CuSO4 supplementation.3. There was evidence of a depressing effect of CuSO4per se on egg production and possibly on oviduct and ovary weight.4. Liver lipid concentration was significantly decreased with decreasing levels of food intake and the results also suggest a depressing effect of CuSO4.5. The Cu concentrations and total contents in liver and kidneys were significantly increased by dietary added CuSO4. Liver and kidney Zn and Fe concentrations were increased with decreasing levels of food intake rather than by CuSO4. addition.

A study of the effects of dietary added cupric oxide on the laying, domestic fowl and a comparison with the effects of hydrated copper sulphate

1. An experiment is reported in which copper, as cupric oxide, was fed to two breeds of laying hen for 336 d at levels equivalent to 150, 300, 450, 600 and 750 mg added Cu/kg diet. The results obtained were compared with those found using similar diets to which the Cu was added as CuSO4. 5H2O.2. Addition of the CuO had no effect on food intake, food conversion efficiency, body-weight or egg production. The CuSO4 addition caused the quadratic response of food intake and the adverse effects on food intake, egg production and body-weight noted in previous experiments.3. The CuO had no effect on liver, kidney, ovary, oviduct or gizzard weight per unit body-weight while the CuSO4 decreased these with the exception of gizzard weight which was significantly increased.4. CuO addition did not affect liver Cu concentration but CuSO4 caused a subtantial increase of liver Cu especially at the 750 mg Cu/kg level of addition.5. CuO addition had no effect on liver lipid concentration but this was depressed at the highest level of CuSO4 addition. Effects on individual fatty acids are presented but no specific conclusions have been reached.

The influence of vitamin A status on the response of chickens to aflatoxin B1 and changes in liver lipid metabolism associated with aflatoxicosis

1 A series of experiments were conducted to investigate the effects of dietary retinol status on chickens ingesting aflatoxin B1. The effects of dietary supplementation with biotin and α-tocopherol were also examined.2. Aflatoxin B1 levels greater than I mg/kg diet had a detrimental effect on ‘liveability’, body-weight gain, food intake and food conversion efficiency. When fed for more than 2 weeks aflatoxin increased relative liver weight and liver lipid concentration. These effects were less pronounced with avitaminotic A chickens.3. A synergistic effect on hydropericardium development was observed between aflatoxin B, and retinol. This effect was not observed when the dietary level of α-tocopherol was increased tenfold.4. The specific activities of certain hepatic lipogenic and amino acid-metabolizing enzymes were influenced by aflatoxin ingestion. A reduction in lipogenic enzyme activity was observed before a reduction in the activities of amino acid-metabolizing enzymes.5. Liver fatty acid composition was significantly influenced by aflatoxin B1. The extent of these changes was reduced by the inclusion of additional dietary biotin.

The influence of essential fatty acids and food restriction on the specific activities of hepatic lipogenic and glutamate-metabolizing enzymes in the laying hen

1. Extended feeding of an essential fatty acid (EFA)-deficient diet to laying hens increased liver size and liver lipid concentration.2. The specific activities of hepatic lipogenic and glutamate-metabolizing enzymes were increased by feeding the EFA-deficient diet.3. Restriction of daily food intake to 75 % of ad lib. intake did not affect the response to dietary fat concentration.4. Hepatic enzyme activities in hens fed on restricted amounts of food and killed just before, or after, the normal daily feeding time indicated no reduced capacity for lipogenesis at the earlier time.