Reproduction in marine invertebrates in “stable” environments: the deep sea model

Summary

Studies over the last 15 years have revealed that deep-sea benthic megainvertebrates show a variety of reproductive patterns that are adapted to the deep-sea, an environment in which the fauna occurs at low densities and resources are sparse. In the NE Atlantic the majority of species reproduce year round whilst a limited number of species reproduce on a seasonal basis believed to be entrained by the deposition of surface derived organic material on the deep-sea bed. A third pattern of rapid growth and early reproduction is found in a limited number of species that utilize unpredictable and ephemeral resources in the deep sea. Examination of the fertilization and behavioural biology of species from the bathyal depths suggest some species enhance fertilization success by forming pairs during their breeding season. However, the same concentration of sperm, as seen in shallow water invertebrates, is required for successful fertilization. At least one deep-sea species of echinoid requires high pressure for successful embryogenesis suggesting a depth-related segregation of deep-sea fauna. The origin of megafaunal populations of deep-sea invertebrates in the N. Atlantic is discussed in the light of these new data in relation to varying reproductive patterns and the environmental changes that have occurred during the last deglaciation.     

Evaluation of Electric Fencing to Inhibit Feral Pig Movements

Abstract: Natural resource managers and agricultural producers are seeking innovative tools to minimize damages caused by rapidly expanding feral pig (Sus scrofa) populations. One tool that has received little scientific inquiry is the use of exclusion fences to protect economically and ecologically sensitive areas. Our objectives were to evaluate the ability of electric fencing to minimize feral pig movements in a captive setting as well as in rangeland and agriculture land. In captivity, we tested a 1-, 2-, and 3-strand electric fence. In our captive trial, we found 65% fewer intrusions (F_2,18 = 20.46, P < 0.001) for electric fences (x̄ = 12.4, SE = 2.8) compared with nonelectric fences (x̄ = 35.6, SE = 6.9). We found no difference (F_2,9 = 1.85, P = 0.212) for 1-strand (x̄ = 28.1, SE = 7.8), 2-strand (x̄ = 14.2, SE = 3.2), and 3-strand (x̄ = 16.9, SE = 4.3) electric fences. However, we found 50% and 40% fewer crossings for the 2- and 3-strand fences, respectively, compared with the 1-strand fence. In our rangeland trial, we found 49% fewer intrusions (F_2,18 =4.39, P = 0.028) into bait stations with a 2-strand electric fence (x̄ =4.1, SE = 1.8) compared with no fence (x̄ =8.1, SE = 2.4). Finally, in our agriculture trial, we found 64% less damage (X²₂ = 5.77, P = 0.016) to sorghum crops with a 2-strand electric fence (x̄ = 4.48, SE = 0.01%) compared with no electric fence (x̄ = 12.46, SE = 0.03%). Furthermore we found no (X¹₁ = 3.72, P = 0.054) wildlife pathways in areas with an electric fence (x̄ = 0.0, SE =0.0) compared with no fence (x̄ = 2.4, SE= 1.3). No electric fence design we tested was 100% pig-proof However, we found electric fencing restricted feral pig movements. Combining electric fencing with other damage control methods in an integrated management program may be the best method for alleviating feral pig damages.     

Vitamin E and selenium treatment of monocrotaline induced hepatotoxicity in rats

Monocrotaline (MCT) is a hepatotoxic pyrrolizidine alkaloid that is derived from plants; exposure may occur by consumption of contaminated grains, herbal teas and medicines. MCT can cause liver damage. We investigated the antioxidant effects of selenium (Se) and vitamin E against the toxic effects of MCT. Female Wistar albino rats were divided into four groups: a control group, an MCT group, an MCT + Se group, and an MCT + vitamin E group. Liver tissues were harvested, fixed, processed to paraffin and sections were cut. Anti-von Willebrand factor (vWF) immunohistochemistry, terminal deoxynucleotidyl transferase dUTP nick end-labeling (TUNEL), and hematoxylin and eosin staining were performed. Serum and liver tissue glutathione (GSH), catalase (CAT), and glutathione peroxidase (GPx) levels were measured. Histopathological and TUNEL data showed significantly increased liver damage in the MCT group compared to controls. Histopathological and TUNEL staining indicated significant improvements in the MCT + vitamin E and MCT + Se groups compared to the MCT group. MCT significantly reduced the serum GSH level and GPx activity, and liver GPx activity. Biochemical data indicated a significant improvement in serum GSH level in the MCT + vitamin E group compared to the MCT group. We suggest that vitamin E and Se afford limited protection against MCT hepatotoxicity.     

Landscape drivers of regional variation in the relationship between total phosphorus and chlorophyll in lakes

1. For north temperate lakes, the well‐studied empirical relationship between phosphorus (as measured by total phosphorus, TP), the most commonly limiting nutrient and algal biomass (as measured by chlorophyll a, CHL) has been found to vary across a wide range of landscape settings. Variation in the parameters of these TP–CHL regressions has been attributed to such lake variables as nitrogen/phosphorus ratios, organic carbon and alkalinity, all of which are strongly related to catchment characteristics (e.g. natural land cover and human land use). Although this suggests that landscape setting can help to explain much of the variation in ecoregional TP–CHL regression parameters, few studies have attempted to quantify relationships at an ecoregional spatial scale. 2. We tested the hypothesis that lake algal biomass and its predicted response to changes in phosphorus are related to both local‐scale features (e.g. lake and catchment) and ecoregional‐scale features, all of which affect the availability and transport of covarying solutes such as nitrogen, organic carbon and alkalinity. Specifically, we expected that land use and cover, acting at both local and ecoregional scales, would partially explain the spatial pattern in parameters of the TP–CHL regression. 3. We used a multilevel modelling framework and data from 2105 inland lakes spanning 35 ecoregions in six US states to test our hypothesis and identify specific local and ecoregional features that explain spatial heterogeneity in TP–CHL relationships. We include variables such as lake depth, natural land cover (for instance, wetland cover in the catchment of lakes and in the ecoregions) and human land use (for instance, agricultural land use in the catchment of lakes and in the ecoregions). 4. There was substantial heterogeneity in TP–CHL relationships across the 35 ecoregions. At the local scale, CHL was negatively and positively related to lake mean depth and percentage of wooded wetlands in the catchment, respectively. At the ecoregional scale, the slope parameter was positively related to the percentage of pasture in an ecoregion, indicating that CHL tends to respond more rapidly to changes in TP where there are high levels of agricultural pasture than where there is little. The intercept (i.e. the ecoregion‐average CHL) was negatively related to the percentage of wooded wetlands in the ecoregion. 5. By explicitly accounting for the hierarchical nature of lake–landscape interactions, we quantified the effects of landscape characteristics on the response of CHL to TP at two spatial scales. We provide new insight into ecoregional drivers of the rate at which algal biomass responds to changes in nutrient concentrations. Our results also indicate that the direction and magnitude of the effects of certain land use and cover characteristics on lake nutrient dynamics may be scale dependent and thus likely to represent different underlying mechanisms regulating lake productivity.     

Strawberry-Flavored Baits for Pharmaceutical Delivery to Feral Swine

ABSTRACT More effective methods to control feral swine (Sus scrofa) damage are needed. We evaluated 8 oral delivery systems designed to deliver pharmaceuticals to feral swine on 2 properties in southern Texas, USA. We used modified PIGOUT® feral pig bait (Animal Control Technologies Australia P/L, Somerton, Victoria, Australia) throughout our trials to compare species-specific visitation and removal rates. Given our consistent finding of high nontarget removal of baits intended for feral swine, we question whether a swine-specific oral delivery system exists for this region.