Tolerance response to ammonia and nitrite in hatchlings paralarvae of <Emphasis Type="Italic">Octopus vulgaris</Emphasis> and its toxic effects on prey consumption rate and chromatophores activity

Ammonia and nitrite are among the most important water quality parameters. The aim of this study was to determine the acute toxicity of unionized ammonia and nitrite on newly hatched Octopus vulgaris paralarvae. Concretely, survival, feeding and chromatophore activity were examined under different NH₃ and NO₂ ⁻ concentrations. The median lethal concentration (LC 50) determined for 24 h was 10.7 ppm for NH₃ and 19.9 ppm for NO₂ ⁻. Based on these results, a concentration range was chosen to test the effect of this environmental contaminants in feeding and chromatophore activity (range between 2.5 and 20 ppm for feeding and 10 and 30 ppm for chromatophore activity), resulting in modifications in both parameters. In fact, a significant decrease (P < 0.05) in Artemia nauplii consumption by the paralarvae was observed with an increase in NH₃ and NO₂ ⁻. Similarly, the chromatophore activity was also affected by concentration of these contaminants, with decreasing response (P < 0.05) when submitted to stressful situations, as the ammonia and nitrite concentration was increased.     

Settling velocity and total ammonia nitrogen leaching from commercial feed and faecal pellets of gilthead seabream (Sparus aurata L. 1758) and seabass (Dicentrarchus labrax L. 1758)

The physico-chemical characteristics of particulate wastes of Sparus aurata and Dicentrarchus labrax were investigated. Changes in the dimensions, settling velocity and total ammonia nitrogen (TAN) leached from commercial feed pellets were investigated after soaking. Also, the settling velocity and TAN leached from faecal pellets of these fish were assessed at 15 and 25 °C. The settling velocity of feed pellets was influenced positively by pellet weight and negatively by immersion length as a result of changes in pellet dimensions after soaking. The settling velocity of faecal pellets was determined by pellet weight. The experimental design did not allow identification of any consistent effect of water temperature on settling velocity. Total ammonia nitrogen leaching over time from feed and faecal pellets was successfully explained by means of a first-order kinetic equation. For feed pellets, water temperature significantly affected the speed of the process and the time at which the maximum TAN leached was reached, but did not influence the maximum TAN leached. Leaching was related to feed pellet size, and so the smaller the pellet, the higher the leaching. Total ammonia nitrogen leaching from faecal pellets was greater per unit weight than in feed pellets. However, neither water temperature nor fish species influenced TAN leaching from faeces.     

Heavy Metals Contamination in Century-Old Manmade Technosols of Hope Bay, Antarctic Peninsula

Technosols are anthropogenic soils that may be strongly impacted by heavy metal deposition, which have not yet been described in Antarctica. In this paper, we present a chemical study of what is supposedly the oldest manmade soil from Antarctic Peninsula, developed in the vicinity of Trinity House and Nordenskjold Hut at Hope Bay. Chemical and morphological soil attributes indicate that a former ornithogenic site (penguin rookery) was further subjected to human disturbance, following local exploration since 1903. We detected very high amounts of heavy metals such as Cd, Cu, Pb, and Zn. For the most impacted site, pseudototal concentrations of these elements reach 47, 2,082, 19,381, and 5,225 mg kg^?1, respectively. Enrichment factors were calculated using Zr as reference element, and high values were found for these contaminated sites, qualifying some of them as extremely polluted. Also, both the mobilizable and mobile fraction of Cd and Pb indicate the need of intervention in the affected area. These findings are all consistent with the human impacts and strong contamination. Strong positive correlation between the pseudototal concentrations of Cd, Cu, Mn, Ni, Pb, and Zn indicates a similar source of pollution. These soils may represent the oldest Technosols in Antarctic Continent.     

Detection of Bemisia tabaci Mediterranean cryptic species on soybean in São Paulo and Paraná States (Brazil) and interaction of cowpea mild mottle virus with whiteflies

Since the detection of Bemisia tabaci Middle East-Asia Minor 1 (MEAM1) species in Brazil in the early 1990s, this whitefly has been the predominant species and the main viral vector in the country. In this work, whiteflies were collected from commercial soybean fields near and far from greenhouses where Mediterranean (MED) species had previously been detected infesting vegetable crops. Results indicated that MEAM1 was the predominant whitefly species in soybean in most sampling sites, while MED was found colonizing soybean plants in open field conditions alone and/or with MEAM1 in several places. Among the tested insects, MED species was mostly detected harbouring the facultative endosymbiont Hamiltonella. We also detected cowpea mild mottle virus (CPMMV) infecting soybean plants. Transmission assays demonstrated that MED species was more efficient transmitting CPMMV from beans to beans and from soybean to soybean plants than MEAM1, while MEAM1 was more efficient in transmitting the virus from soybean to bean than MED. Performance assays indicated that adult emergence of both species on CPMMV-infected soybean plants was higher when compared with the emergence on healthy plants. Moreover, nonviruliferous MED and MEAM1 adults preferred to settle more often on healthy plants, while viruliferous adults settled more often on CPMMV-infected soybean plants. As MED has already been found in soybean open fields in São Paulo and Paraná States, Brazil, and it is a good vector of CPMMV, we anticipate problems related to whitefly management and to increase in the incidence of the virus in soybean.     

Growth and mortality of common octopus Octopus vulgaris reared at different stocking densities in Mediterranean offshore cages

Four ongrowing cycles of common octopus ( Octopus vulgaris ), each with two stocking densities, were carried out in an offshore area in order to evaluate the effect of the following variables on growth ( G , % body weight day⁻¹) and mortality ( M , % day⁻¹): weight ( W , 0.5–3.0 kg), temperature ( T , 14–26 °C), stocking density (SD, 6–46 kg m⁻³), size dispersion, expressed as coefficient of variation (CV, 13–42%) and significant wave height (SWH: 0.4–1.2 m). The assays were performed in an 8 m³ stainless-steel floating cage divided into two compartments of 4 m³ each. For the range of temperatures considered (14–26 °C), G depended significantly on T and SWH, with maximum G values being obtained at 18.5 °C and with an important negative effect of SWH. M depended significantly on T, W and CV, mortality being minimal at 18 °C. The two other variables had an antagonistic effect, mortality increasing with greater size dispersion – suggesting that animals should be graded throughout the process – although the effect diminished as the sizes increased. The results point towards two alternatives for the commercial ongrowing of octopus under the particular conditions of the present study: (A) two ongrowing cycles of 3.5 months to reach a final weight of 2.5 kg or (B) one 5-month cycle to reach a final weight of 3.5 kg.