Spermatozoan ultrastructure and spermatogenesis in aplousobranch ascidians,with some phylogenetic considerations

Spermatozoa and some stages of spermatogenesis were studied for four species of aplousobranch ascidians. Spermatozoa of Clavelina lepadiformis (Müller) (family Clavelinidae) are plesiomorphous in that they have apical acrosomal vesicles and a moderately elongated, cylindrical nucleus. The elongated mitochondrion is twisted ea. 11/2 times around the nucleus. In their ultrastructural morphology, C. lepadiformis sperm conform in some respects to the least-derived ascidian sperm, those of the phlebobranch ascidian Ciona intestinalis L.; however, the sperm of Clavelina lepadiformis have two apomorphies not shared with those of Ciona sp.: (1) the mitochondrion of Clavelina lepadiformis is long and spiralled along the entire nucleus rather than being comparatively compact and not at all helical; (2) the mitochondrial cristae are elongated parallel to the long axis of the nucleus, whereas in Ciona sp. sperm the cristae are unmodified. In Distaplia sp., Aplidium sp. and Synoicum pulmonaria (Ellis and Solander) the spermatozoa are more derived and consist of a proximal cylindrical and a distal corkscrew-like part. The mitochondrion in Distaplia sp. and Aplidium sp. contains electron-dense material and extends in a long thread around the nucleus. In S. pulmonaria the mitochondrion surrounds the anterior part of the nucleus in mature spermatozoa, and an elongated, dense structure displaying fine striation is enclosed in the mitochondrion in late spermatids. The sperm ultrastructural morphology observed in this study is consistent with the majority view that clavelinids are closest to the ancestral ascidian but is also consistent with other conclusions, particularly that the Cionidae are closest to the stem ascidian.     

Zoogeography of Northwest Atlantic opisthobranch molluscs

Currently available information on the distribution of species of the opisthobranch orders Cephalaspidea, Nudibranchia and Sacoglossa (Mollusca: Gastropoda) in the northwest Atlantic Ocean is presented. Except for Sacoglossa, the fauna is markedly amphiatlantic, but the temperate West Atlantic component increases southward and dominates south of New Jersey. Species' diversity of nudibranchs and cephalaspids on the continental shelf decreases between northern New England and Cape Hatteras in association with a southward decline in the proportion of amphiatlantic species. This is not evident for the cephalaspids of the continental slope, a higher percentage of which are amphiatlantic. The entire fauna is subdivided into 5 groups: arctic, boreo-subarctic, boreal, West Atlantic temperate, and West Atlantic tropical. The latter does not extend north of Cape Hatteras, but the remaining groups broadly overlap in the northwest Atlantic. The southward limits of amphiatlantic species are presented and related to sea surface temperatures. The thermal characteristics of a critical zone between Cape Cod and Connecticut are discussed, and a maximum temperature of 15 °C is suggested for successful reproduction of the boreo-subarctic component, and 25 °C for the boreal component. The distribution of boreal species on both sides of the North Atlantic is discussed, and a suggestion is made that the southward speread of these species in North America is limited by extreme summer warming south of New Jersey, despite favorable winter temperatures, which extend much farther south.Contribution No. 66 of the Marine Research Laboratory, University of Connecticut, USA.     

Feeding and respiration rates of a planktonic copepod (<Emphasis Type="Italic">Calanus sinicus</Emphasis>) oversummering in Yellow Sea Cold Bottom Waters

The distribution, feeding and oxygen consumption of Calanus sinicus were studied in August 2001 on a transect across Yellow Sea Cold Bottom Waters (YSCBW) and two additional transects nearby. The distribution of C. sinicus adults and copepodites stage CV appeared to be well correlated with water temperature. They tended to concentrate in the YSCBW (>10,000 ind. m^–2) to avoid high surface temperature. Gut pigment contents varied from 0.44 to 2.53 ng chlorophyll a equivalents (chl a equiv.) ind.^–1 for adults, and from 0.24 to 2.24 ng chl a equiv. ind.^–1 for CV copepodites. We found no relationship between gut pigment contents and the ambient chl a concentrations. Although the gut evacuation rate constants are consistent with those measured for other copepods, their low gut pigment contents meant an estimated daily herbivorous ingestion of <3% of body carbon in the YSCBW and <10% outside the YSCBW. However, based on estimates of clearance rates, C. sinicus feeds actively whether in the YSCBW or not, so the low ingestion rates probably reflect shortage of food. Oxygen consumption rates of C. sinicus ranged from 0.21 to 0.84 l O₂ ind.^–1 h^–1, with high rates often associated with high temperature. From the oxygen consumption rates, daily loss of body carbon was estimated to be 4.0–13.7%, which exceeds our estimates of their carbon ingestion rates. C. sinicus was probably not in diapause, either within or outside the YSCBW, but this cold-water layer provides C. sinicus with a refuge to live through the hot, low-food summer.Communicated by T. Ikeda, Hakodate     

Single and joint effects of acetochlor and urea on earthworm Esisenia foelide populations in phaiozem

Much attention is paid to soil health and environmental safety. Earthworms are an important indicator of soil ecosystem health and safety. Ecological toxicity of acetochlor and excessive urea, in both their single and joint effects, on earthworm Esisenia foelide was thus studied using the soil-culture method. Acetochlor had an enhanced toxicity from low concentration to high concentration. The mortality of earthworms after a 6-day exposure was changed from 0 to 86.7%, and the weight change rate ranged from 7.86 to -30.43%, when the concentration of acetochlor was increased from 164 to 730 mg kg(-1). Urea expressed its positive and beneficial effects on earthworms when its concentration was lower than 500 mg kg(-1). Strongly toxic effects took place when the concentration of urea was higher than 1000 mg kg(-1). The mortality of earthworms exposed to urea reached 100% when its concentration was more than 1500 mg kg(-1). When the concentration of urea was lower than 500 mg kg(-1), there were antagonistic effects between the two agrochemicals on earthworms; when the concentration of urea was higher than 500 mg kg(-1), joint toxic effects of acetochlor and excessive urea on earthworms were synergic. In any case, excessive urea application is very harmful to the health of soil ecosystems.     

Field Studies on 32P Movement and P Leaching from Flooded Paddy Soils in the Region of Taihu Lake, China

Field experiments were done in two sites, Yixing and Changshu, Jiangsu province, China, to study P movement and leaching in flooded paddy soils. P movement in soil was investigated by using the KH₂ ³²PO₄ tracker method, and the amount of P leached from the soil layer in different depths was estimated by measuring P concentrations in the soil solution and saturated hydraulic conductivities in field. Determination was done about one month after P application. There was 46% and 42% of total ³²P retained in the 0–5cm layer of soil in the Yixing site and in the Changshu site respectively. The ³²P retained in the 25–30 cm layer was only about 1–2% of the total ³²P added. Furthermore, 8.01% of ³²P in the soil of Yixing site and 16.8% of ³²P in the soil of Changshu site was lost from the layer 0–30cm soil. The seasonal amounts of P leached from the top soil layer and from bottom layer are about 4.5–5.8% and 1.6–2.1% of the total P application, respectively. Changes of total P concentrations in soil solutions during rice growth showed that the fertilizer P applied before flooding of the paddy fields suffered a flash leaching loss and a slow leaching loss. We concluded that the fertilizer P could quickly move in the flooded paddy rice field and parts of it can enter into surface water and ground water. Unless the P application is well managed the risk of P loss and consequently environmental pollution exist.     

Adaptive behaviour of chironomid larvae (Chironomus riparius) in response to chemical stimuli from predators and resource density

Chemical-mediated effects of predatory fish on chironomid larvae behaviour have been ignored so far. Sediment-dwelling chironomid larvae inhabit protective burrows from which they extend their bodies only to feed on deposited detritus and microalgae from the surrounding sediment. Here, we performed factorial laboratory experiments to study whether fish-borne chemical cues (kairomones) are responsible for behavioural trait changes of chironomid larvae, and whether chironomid larvae are able to assess the densities of fish predators and food resources and the trade-off between them. We exposed naïve Chironomus riparius larvae to the chemical presence of zero, one, and ten predator fish (Rutilus rutilus) and offered two resource levels (low food, high food) for each treatment. Kairomones induced significant inherent behavioural trait changes in chironomid larvae. During the first 120 min after exposing chironomids to fish-conditioned water, we found a significant increase in digging activity with increasing predator density. After 3 days of exposure, the deepest chironomid burrows were found in treatments with the highest predator density. Chironomid larvae were significantly able to adjust their foraging behaviour to different predator densities and food concentrations and trade off between them; that is, when fish predators were more abundant or when more food resources were available, the foraging activities of larvae were significantly reduced. Our data suggest that chemically mediated trait changes (burrowing and foraging behaviour) may cascade through the littoral food web.     

Residues of organochlorinated pesticides in eggs of water birds from Tai Lake in China

The levels of organochlorine compounds in eggs of water birds from the colony on Tai Lake in China were studied. The eggs were collected in 2000 and belonged to the following species: 65 samples of black-crowned night heron (Nycticorax nycticorax), 36 samples of little egret (Egretta garzetta), 26 samples of cattle egret (Bubulcus ibis) from 13 clutches and 43 samples of Chinese pond heron (Ardeola bacchus) from 17 clutches. Dichlorodiphenyltrichloroethane (DDT) and its derivates (DDE and DDD), hexachlorocyclohexane (HCH) and its isomers (alpha-HCH, beta-HCH, gamma-HCH, delta-HCH), heptachlor, heptachlor epoxide, aldrin, dieldrin, endrin, endrin aldehyde, alpha-endosulfan, beta-endosulfan, and endosulfan sulfate were determined in the laboratory by gas chromatography. The data showed that DDE had the highest levels in all the samples, followed by beta-HCH. The mean levels of DDE among the water bird species were in the order as follows: black-crowned night heron (5464.26 ng/g, dry weight) > Chinese pond heron (2791.12 ng/g, dry weight) > little egret (1979.97 ng/g, dry weight) > cattle egret (660.11 ng/g, dry weight). DDT and its metabolites accounted for 90% of the total organochlorines, except that it was only 73% for cattle egret. The differences of the residue among the bird species were statistically significant and could be attributed to their variations in prey and habitat. Although the DDE burdens in Tai Lake were much lower than 8 microg/g (wet weight) which are thought to have significant adverse effects on black-crowned night herons, they would be expected to increase the risk of adverse effects on survival of chicks of herons and egrets, particularly black-crowned night heron, based on the critical value of 1 microg/g (wet weight) DDE. The burdens of HCHs in this study were higher and the cyclodienes were lower than those found elsewhere.     

Metabolism of a nonylphenol isomer by Sphingomonas sp. strain TTNP3

For elucidation of the metabolism of the endocrine disruptor nonylphenol by Sphingomonas sp. strain TTNP3, the degradation of an isomer of nonylphenol, 4(2,6-dimethyl-2-heptyl)-phenol, has been studied. As in the case of 4(3,5-dimethyl-3-heptyl)-phenol, the metabolism of this nonylphenol isomer leads to the formation of the NIH-shifted product 2(2,6-dimethyl-2-heptyl)-1,4-benzenediol (NIH: National Institute of Health), but also to the alkoxy derivative 4(2,6-dimethylheptan-2-yloxy)phenol as additional metabolite. To the best of our knowledge, this is the first report describing the formation of alkoxyphenol as a degradation product of nonylphenol. Additionally, these results provide for the first time evidence for slight differences in the biodegradation of the isomers of nonylphenol.     

Changes of Soil Microbiological Properties Caused by Land Use Changing From Rice–Wheat Rotation to Vegetable Cultivation

A survey was done recently in Jiaxing city of Zhejiang Province in the Yangtze River Delta to compare the differences of soil microbiological properties among paddy soils with different land use including continuous open-field vegetable cultivation (OFVC), plastic-greenhouse vegetable cultivation (PGVC) and traditional rice–wheat rotation (RWR). The soil types included are percolating, permeable and waterlogged paddy soils. The results indicate that the microbial flora was markedly changed as the land use changed for all the three soil types. In continuous vegetable cultivation soils, especially in PGVC soils, the bacteria amounts decreased dramatically, but the fungal and actinomyce amounts increased as compared with RWR soils. The dehydrogenase activities decreased significantly in vegetable soils, especially in PGVC soils as compared with RWR soils. The microbial biomass C and the total phospholipid contents (TPL) in vegetable cultivation soil greatly decreased as compared with RWR soils. Biolog analysis indicated that the kinds of carbon sources that could be metabolized by native microbes in PGVC soils greatly decreased as compared with OFVC soils and RWR soils, revealing that microbial diversity had decreased since land use change. The activities of some soil enzymes including urease, invertase and phosphase were all lower in OFVC soils than those in RWR soils, and those in PGVC soils were the lowest. The degradation of microbiological activities in continuous vegetable cultivation soils, especially in PGVC soils, as compared with RWR soils might have been caused by soil acidification and accumulation of salts due to overuse of both organic and inorganic fertilizers in vegetable cultivation.     

Charakterisierung von Holzasche aus Biomassefernheizwerken

Analyses of ashes from wood chips and bark combustion and research work about possibilities of utilization of these ashes showed that in general a mixture of bottom ash and cyclon fly-ash in the ratio as they occur in the plant can be used as a fertilizer and liming material. An important question is whether mineral impurities (sand, earth, stones) in the biomass are responsible for slagging on the grate (by lowering the melting point) because sintered and slagged ash with a particle size larger than 2 cm has to be sieved or milled before utilized. Furthermore, the influence of these impurities on the homogeneity of wood ash is important for taking and preparing samples for analysis. Usually, the occurring ash fractions in biomass district heating plants can only be volumetrically measured. In order to determine the actual mass flow and to proportion the ash-amounts for fertilization properly, it is necessary to know the bulk densities of the different ash fractions in dependence on the particle size and the biomass used. Moreover, the knowledge of the surface properties of fly-ash particles enables to evaluate the influencing variables on the process of heavy metal deposition from the flue gas to the fly-ash particles. This information represents the basis for a fractionated desublimation/condensation of heavy metals. The aim is to concentrate them in the filter fly-ash, because this smallest and finest ash fraction is cut off from the ash cycle and is disposed of. Conforming to these open questions, ashes from biomass district heating plants were examined. The facts and findings obtained represent the basis for technological measures in order to improve a closed cycle economy with wood ash.