ON THE PROTONEPHRIDIA AND 'LARVAL KIDNEYS' OF NASSARIUS (HINIA) RETICULATUS (LINNAEUS) (CAENOGASTROPODA)

Protonephridia in marine streptoneuran gastropods are describedfor the first time. The organization of these paired organsof the intracapsular veliger larva of Nassarius reticulatusis described. The ciliary flame is formed by a single terminalcell. The duct is formed by one tubular cell and the aperturalcell, which forms the lips of the excretory pore. In addition,the surface of the apertural cell is covered to a great extentby the post-velar bud cell (usually termed ‘larval kidney’).Protonephridia like these are considered to be widely distributedamong streptoneuran gastropods. The homology of these organswith those of opis-thobranchs and pulmonates is suggested. Thepost-velar buds (= ‘larval kidneys’) are suggestedas a synapomorphous character of Caenogastropoda. The functionof the postvelar buds is discussed taking into considerationthe existence of a protonephridium and a possible functionalconnection between these two structures. (Received 14 June 1990; accepted 1 September 1990)     

Energy crops: current status and future prospects

Energy crops currently contribute a relatively small proportion to the total energy produced from biomass each year, but the proportion is set to grow over the next few decades. This paper reviews the current status of energy crops and their conversion technologies, assesses their potential to contribute to global energy demand and climate mitigation over the next few decades, and examines the future prospects. Previous estimates have suggested a technical potential for energy crops of～400 EJ yr^?1 by 2050. In a new analysis based on energy crop areas for each of the IPCC SRES scenarios in 2025 (as projected by the IMAGE 2.2 integrated assessment model), more conservative dry matter and energy yield estimates and an assessment of the impact on non‐CO₂ greenhouse gases were used to estimate the realistically achievable potential for energy crops by 2025 to be between 2 and 22 EJ yr^?1, which will offset～100–2070 Mt CO₂‐eq. yr^?1. These results suggest that additional production of energy crops alone is not sufficient to reduce emissions to meet a 550 μmol mol^?1 atmospheric CO₂ stabilization trajectory, but is sufficient to form an important component in a portfolio of climate mitigation measures, as well as to provide a significant sustainable energy resource to displace fossil fuel resources. Realizing the potential of energy crops will necessitate optimizing the dry matter and energy yield of these crops per area of land through the latest biotechnological routes, with or without the need for genetic modification. In future, the co‐benefits of bioenergy production will need to be optimized and methods will need to be developed to extract and refine high‐value products from the feedstock before it is used for energy production.     

Impact of intentionally injected carbon dioxide hydrate on deep-sea benthic foraminiferal survival

Sequestration of carbon dioxide (CO₂) in the ocean is being considered as a feasible mechanism to mitigate the alarming rate in its atmospheric rise. Little is known, however, about how the resulting hypercapnia and ocean acidification may affect marine fauna. In an effort to understand better the protistan reaction to such an environmental perturbation, the survivorship of benthic foraminifera, which is a prevalent group of protists, was studied in response to deep-sea CO₂ release. The survival response of calcareous, agglutinated, and thecate foraminifera was determined in two experiments at ∼3.1 and 3.3 km water depth in Monterey Bay (California, USA). Approximately 5 weeks after initial seafloor CO₂ release, in situ incubations of the live–dead indicator CellTracker Green were executed within seafloor-emplaced pushcores. Experimental treatments included direct exposure to CO₂ hydrate, two levels of lesser exposure adjacent to CO₂ hydrate, and controls, which were far removed from the CO₂ hydrate release. Results indicate that survivorship rates of agglutinated and thecate foraminifera were not significantly impacted by direct exposure but the survivorship of calcareous foraminifera was significantly lower in direct exposure treatments compared with controls. Observations suggest that, if large scale CO₂ sequestration is enacted on the deep-sea floor, survival of two major groups of this prevalent protistan taxon will likely not be severely impacted, while calcareous foraminifera will face considerable challenges to maintain their benthic populations in areas directly exposed to CO₂ hydrate.     

Invertebrate traits for the biomonitoring of large European rivers: an assessment of specific types of human impact

1. The power of selected biological invertebrate traits for discriminating different types of human impact (heavy metal pollution and cargo‐ship traffic) were tested using ecological reasoning and linear Discriminant Function Analysis (DFA). 2. Frequency distributions of individual traits and categories of traits from 68 least impacted river reaches (LIRRs) and 304 impacted river reaches were used to define simple assessment rules based on ecological reasoning for specific impairments in large European rivers. In calibration, a maximum of three variables with a priori predictions and two different impairment threshold levels were used. Similarly, DFA was performed on the same variables included in the ecological reasoning approach, but also on all available traits or trait categories. 3. Validation with an independent data set (40 LIRRs, 291 variously impacted river reaches) and using the ecological reasoning approach showed that 75–78% of the reaches were correctly assign with rules on all impact types, 35–57% with rules on heavy metal pollution and 78–93% with rules on cargo‐ship traffic. By comparison, validation showed that DFA performed globally poorer than the ecological reasoning approach. In addition, the performance of the rules based on ecological reasoning remained stable, whereas DFA performance changed between calibration and validation. 4. Although not defined for this purpose, our study provided alarming evidence regarding the impact of cargo‐ship traffic on invertebrate communities in river reaches. Reaches with cargo‐ship traffic were found to have more genera with long life cycles that reproduce repeatedly by ovoviviparity and have a sessile life. 5. The performance of our trait‐based approach to correctly assign reaches to either least impacted or impacted conditions should promote further research on the topic across larger geographic areas (without regionalization) and across smaller stream types to provide a powerful biomonitoring tool that fulfils current European Union directives.