Eutrophication of reservoirs in South Korea

Natural lakes in South Korea are limited in number and generally quite small. As a result, reservoirs and regulated rivers are the major sources of freshwater for society. About 18 000 reservoirs have been constructed in South Korea, and they are particularly important for domestic water supply. Thirteen of the major reservoirs were surveyed in this general assessment of the trophic state of South Korean reservoirs. Ten reservoirs were from the upper or middle reaches of rivers (including eight of the ten largest reservoirs in Korea), and three were estuarine reservoirs. Reservoirs in the mountainous district of South Korea were usually mesotrophic, whereas the estuarine reservoirs were highly eutrophic. Because total nitrogen to total phosphorus ratios were always between 18 and 163, phosphorus was probably more limiting than nitrogen for algal growth. However, hydraulic residence time and light penetration may be limiting in the nutrient-enriched downstream reservoirs. In winter, algal density was lowest in deep reservoirs, perhaps due to deep mixing. During the same season, algal density was high in shallow reservoirs, perhaps due to a favorable hydraulic residence time. Factors contributing to the observed eutrophication patterns, including nutrient runoff from agriculture, animal farms, fish aquaculture, and urban areas, are discussed. According to the national budget of phosphorus, fertilizer and livestock manure are major source of phosphorus, contributing 133 400 and 73 700 tons of phosphorus per year, respectively, while human excretion discharges 30 000 tons P year⁻¹. Reduction of the application of fertilizer, proper treatment of manure, and conservation of topsoil may be the most practical and effective measures to prevent further lake eutrophication. Received: February 15, 2001 / Accepted: July 2, 2001     

Conodont biostratigraphy of Tournaisian shallow-water carbonates in central Guangxi,South China

The conodont faunas of Tournaisian shallow-water carbonates from central Guangxi are described mainly for biostratigraphic purposes. A complete series of samples was collected from the Long’an and Du’an formations in the Long’an section. These formations are characterized by lime-mudstone, skeletal and peloidal wackestone, packstone and grainstone with typical shallow-water biota. Overall, these samples produced 809 identifiable Pl elements, belonging to 50 species in 11 genera, of which one species and one subspecies are new. The fauna enables the establishment of seven biozones (in ascending order): Polygnathus spicatus, Siphonodella homosimplex, S. sinensis, S. dasaibaensis, Polygnathus communis carina Acme, Gnathodus cuneiformis, and P. communis porcatus zones. Based on these new collections from central Guangxi and on data from the literature, a conflated Tournaisian conodont zonation is proposed for shallow-water successions in South China. Most of the conodont zones correlate well with their counterparts recognized in Western Europe, which may be of greater significance in stratigraphic correlation than previously thought.     

Parasitism, oddity and the mechanism of shoal choice

When choosing between shoals differing in Schistocephalus solidus infection status, uninfected test sticklebacks Gasterosteus aculeatus showed a preference for joining uninfected conspecifics when shoal sizes were equal, but reversed this preference when the relative size of the infected shoal was increased by a factor of 3. When given a choice between a shoal composed of size-matched minnows Phoxinus phoxinus and a shoal composed of the same number of all uninfected or all S. solidus -infected sticklebacks, test fish always preferred the sticklebacks, regardless of their infection status, over the minnow shoal. These observations suggest that species, parasite status and shoal size are all of importance when fish decide which shoal to join.     

Epidemiology of Dermatophytoses in an Area South of Tehran,Iran

Dermatophyte infections have been considered to be a major public health problem in many parts of the world. The aim of this study was to identify the etiological and epidemiological factors of dermatophyte infections in an area south of Tehran. A total of 1254 patients suspected to have dermatophytic lesions were examined over a period of three years (1999-2001). Material collected from skin, hair, and nails was submitted to direct microscopic examination using KOH, cultured in Sabouraud dextrose agar and microscopically examined for colony morphology, in order to the identify the 169 dermatophytes isolated. The prevalence of dermatophytoses was 13.5% (95% CI: 11.7-15.5%). Their incidence was 10.6 per 100,000 person-years (95% CI: 8.5-13.2). Epiderophyton floccosum was the most frequent dermatophyte isolated (31.4%) followed by Trichophyton rubrum (18.3%), T. mentegrophytes (17.2%), T. violaceum (16.6%), Microsporum canis (6.5%), T. verrucosum (4.7%) and M. gypseum (4.1%). Epidermophytes floccosum was found to be the most common isolated dermatophyte in age groups 20-29 (30.2%). Tinea corporis (31.4%) was the most common type of infection, followed by tinea cruris (20.7%), tinea manuum (15.4%), tinea capitis (12.4%), tinea pedis (10.6%), tinea faciei (7.1%), and tinea unguium (2.4%). The frequency rate of all of the types of tinea was higher in males than in females. The anthrophilic species E. floccosum was the most common dermatophyte as a causative agent of tinea. The most prevalent fungal infection was tinea corporis caused by E. floccosum.     

Depositional processes of ribbon carbonates in Middle Cambrian of Iran (Deh-Sufiyan Formation,Central Alborz)

A variety of ribbon carbonates of the Deh-Sufiyan Formation (Middle Cambrian) in Central Alborz Range of northern Iran are studied to provide facies characterization and paleoenvironmental interpretation of ribbon carbonates on shallow-marine carbonate platforms. Seven types of ribbon carbonates are divided based mainly on sedimentary structures, ichnofossils, and bed geometry, which represent deposition during different phases of storm-induced processes. The different features of the storm deposits in ribbon carbonates such as hummocky and swaley cross-stratification, planar lamination, and combined-flow-ripple cross-stratification were formed by combined flows. Identification and interpretation of ichnological signatures and the spatial arrangement of succession of sedimentary structures are used to further refine sedimentary interpretations of parameters such as wave energy, substrate properties, variability in sedimentation rates, and proximality-distality trends of a wave-dominated marine ramp sequence. Successions from individual storm events reflect deposition during increasing combined oscillatory and unidirectional flow succeeded by the waning stages. The study provides depositional processes and models of various ribbon carbonates that may be useful for facies interpretation of ribbon rocks elsewhere.     

Revision of the foraminiferal biozonation scheme in Upper Cretaceous carbonates of the Dezful Embayment,Zagros, Iran: Integrated palaeontological,sedimentological and geochemical investigation

Cretaceous carbonate successions of the Bangestan Group, such as the Sarvak and Ilam formations, are among the most prolific hydrocarbon reserves of the Middle East. However, relatively little is known about their detailed palaeontology and biostratigraphy. Moreover, due to lithological similarity of these carbonate formations recognition of their boundaries in subsurface studies is problematic. To investigate these units, biostratigraphic analyses were carried out on nearly 1100 m of cores, including core plug samples and thin sections prepared from five giant and supergiant oilfields in the northern and southern Dezful Embayment, SW Iran. Accordingly, 59 species of foraminifera (assigned to 43 genera) as well as 11 species of non-foraminifera (10 genera) were recognized. As a result, three biozones were identified, which in stratigraphic order are: Nezzazata-Alveolinids Assemblage Zone; Moncharmontia apenninica-Nezzazatinella-Dicyclina Assemblage Zone; and Rotalia skourensis-algae Assemblage Zone. These are compared with the Wynd's (1965) biozonation scheme, previously introduced in the Zagros area, and a revised scheme is presented. Accordingly, a Cenomanian–Turonian age and a Coniacian–Campanian age are envisaged for the Upper Sarvak and Ilam formations, respectively. In our new biostratigraphic scheme, the Sarvak–Ilam formations boundary is considered to be located above the Moncharmontia apenninica-Nezzazatinella-Dicyclina Assemblage Zone (equivalent of Valvulammina-Dicyclina Assemblage Zone of Wynd, 1965), that is Turonian in age. This zone is bounded by two palaeoexposure surfaces, which correspond approximately to the C–T boundary transitional interval and a post-Turonian, which can be possibly assigned to the Coniacian. Significant sedimentological features of these disconformities include bauxitic–lateritic horizons, karstified profiles and solution-collapsed breccias. Geochemical signatures of these meteorically altered surfaces are also considered to calibrate biofacies and biozones. Finally, we compared our new biozonation scheme with other studies in neighboring areas of SW Iran and the Middle East.     

The effect of hunger, shoal size and the presence of a predator on shoal cohesiveness in bluntnose minnows, Pimephales notatus Rafinesque

Shoals of fish vary in their degree of cohesiveness as certain conditions such as hunger, predation risk and shoal size vary: this study relates this variation to the benefits of shoaling. Shoals of bluntnose minnows, Pimephales notatus Rafinesque, consisting of different numbers of individuals were starved for 5, 24 or 72 h and allowed to forage in the presence or absence of a predator. Cohesiveness was measured as the dispersion offish within the shoal (the radius of the longest axis of the shoal corrected for the number of fish in the shoal), straggle frequency (the number of movements by individuals of at least 5 body lengths away from the shoal) and aggressive interactions between shoal members. Cohesiveness increased as shoal size and the benefits per individual increased. Cohesiveness also increased in the presence of a predator, as did the importance of shoaling as a means of reducing predation risk. Cohesivenes decreased as hunger level increased, possibly as a result of increased competition for food among shoal members.     

Chromosomal evolution in the South American Nymphalidae

We give the chromosome numbers of about 80 species or subspecies of Biblidinae as well as of numbers of neotropical Libytheinae (one species), Cyrestinae (4) Apaturinae (7), Nymphalinae (about 40), Limenitidinae (16) and Heliconiinae (11). Libytheana has about n=32, the Biblidinae, Apaturinae and Nymphalinae have in general n=31, the Limenitidinae have n=30, the few Argynnini n=31 and the few species of Acraeni studied have also mostly n=31. The results agree with earlier data from the Afrotropical species of these taxa. We supplement these data with our earlier observations on Heliconiini, Danainae and the Neotropical Satyroid taxa. The lepidopteran modal n=29-31 represents clearly the ancestral condition among the Nymphalidae, from which taxa with various chromosome numbers have differentiated. The overall results show that Neotropical taxa have a tendency to evolve karyotype instability, which is in stark contrast to the otherwise stable chromosome numbers that characterize both Lepidoptera and Trichoptera.     

Synthesis and Release of Dopamine in Rat Brain: Comparison Between Substantia Nigra Pars Compacta, Pars Reticulata, and Striatum

Dopamine (DA) is synthesized and released not only from the terminals of the nigrostriatal dopaminergic neuronal pathway, but also from the dendrites in the substantia nigra. We have investigated the regulation of the DA turnover, the DA synthesis rate, and the DA release in the substantia nigra pars compacts (SNpc) and pars reticulata (SNpr) in vivo. As a measure of DA turnover, we have assessed the concentrations of 3,4-dihydroxyphenylacetic acid and homovanillic acid. As a measure of the DA synthesis rate, we have determined the 3,4-dihydroxyphenylalanine accumulation after inhibition of aromatic L-amino acid decarboxylase by 3-hydroxybenzylhydrazine. As a measure of DA release, we have investigated the disappearance rate of DA after inhibition of its synthesis by alpha-methyl-p-tyrosine and the 3-methoxytyramine accumulation following monoamine oxidase inhibition by pargyline. Both the DA turnover and the DA synthesis rate increased following treatment with the DA receptor antagonist haloperidol and decreased following treatment with the DA receptor agonist apomorphine in the SNpc and in the SNpr, but the effects of the drugs were less pronounced than in the striatum. gamma-Butyrolactone treatment, which suppresses the firing of the dopaminergic neurons, increased the DA synthesis rate in the striatum (165%), but had no such effect in the SNpc or SNpr. Haloperidol, apomorphine, and gamma-butyrolactone increased, decreased, and abolished, respectively, the DA release in the striatum, but the drugs had no or only slight effects on the alpha-methyl-p-tyrosine-induced DA disappearance and on the pargyline-induced 3-methoxytyramine accumulation in the SNpc or SNpr. Taken together, these results indicate that the DA synthesis rate, but not the DA release, are influenced by DA receptor activity and neuronal firing in the SNpc and SNpr. This is in contrast to the situation in the striatum, where both the DA synthesis rate and the DA release are under such control.     

Kin structure and shoal composition dynamics in the guppy, Poecilia reticulata

Although kin associations between fish can develop in the laboratory, the importance of kin structure in natural social groups remains uncertain. Guppies ( Poecilia reticulata ) possess many behavioural and life-history traits that promote kin structure, and so constitute ideal candidates for testing its general significance amongst fish. We collected 25 adult only shoals from ∼150 m stretches along two Trinidadian rivers. The 272 sampled fish were genotyped from a pool of seven hypervariable microsatellite loci. Although mark-recapture experiments have previously detected male-biased dispersal, which is predicted from the guppy mating system and which may have important implications for population differentiation, we found no sex-biases in dispersal between shoals. Because sex-biased dispersal was not evident, males and females were pooled in analyses of kin structure. Relatedness levels within each shoal did not differ significantly from zero, indicating that kin selection does not contribute to gross structure. Instead, our data is more consistent with the hypothesis that individual-level selection underlies shoal composition dynamics. These dynamics have important implications for the evolution of cooperative behaviour in guppies.     

Pars intermedia and Background Adaptation in the Skate,Raja radiata

The background adaptation ability in intact skates, Raja radiata, is extremely variable. Many specimens take several days for adaptation, whereas some show rapid and distinct responses. The dermal and epidermal melanophores do not always react simultaneously. Neurointermediate lobectomy abolishes the black-background response. Injection of neuro-intermediate lobe extracts and pure α-MSH into these specimens result in temporary darkening, but the paling time is different in these two types of treatments.     

Pars,PI 3-kinase,and the establishment of neuronal polarity

As reported in this issue of Cell, the protein complex consisting of mPar3, mPar6, and atypical protein kinase C is selectively localized to the axonal growth cone of cultured hippocampal neurons and is required for specification of the axon.     

Mechanisms underlying shoal composition in the Trinidadian guppy, Poecilia reticulata

Free-ranging groups are frequently assorted by phenotypic characters. However, very little is known about the underlying processes that determine this structuring. In this study, we investigate the mechanisms underlying the phenotypic composition of shoals of guppies ( Poecilia reticulata ) in a high-predation stream in Trinidad's Northern Mountain Range. We collected 57 entire wild shoals, which were strongly assorted by body length. Shoal encounters staged within an experimental arena showed shoal fission (but not fusion) events to be an important mechanism in generating phenotypic assortment. In the wild, fission and fusion between guppy shoals occurred extremely frequently and thus are unlikely to constrain the opportunities for shoal assortment. However, fission and fusion processes occur under the restrictions imposed by the distribution of individuals within the environment. We observed size specific segregation within the habitat in three dimensions, providing a passive mechanism that contributes to the maintenance of the observed homogeneity of group composition. Furthermore sex differences were found in social behaviour. Individual male guppies switched between shoals more frequently than females and left a shoal more often than females. We argue that shoal composition is determined by habitat segregation on a medium spatial scale and by fission/fusion processes on a small spatial scale (with sex-specific shoal dynamics adding a additional layer of complexity).     

Concomitant replacement of language and mtDNA in South Caspian populations of Iran

The Gilaki and Mazandarani occupy the South Caspian region of Iran and speak languages belonging to the North-Western branch of Iranian languages . It has been suggested that their ancestors came from the Caucasus region, perhaps displacing an earlier group in the South Caspian . Linguistic evidence supports this scenario, in that the Gilaki and Mazandarani languages (but not other Iranian languages) share certain typological features with Caucasian languages . We analyzed patterns of mtDNA and Y chromosome variation in the Gilaki and Mazandarani. Based on mtDNA HV1 sequences, the Gilaki and Mazandarani most closely resemble their geographic and linguistic neighbors, namely other Iranian groups. However, their Y chromosome types most closely resemble those found in groups from the South Caucasus. A scenario that explains these differences is a south Caucasian origin for the ancestors of the Gilaki and Mazandarani, followed by introgression of women (but not men) from local Iranian groups, possibly because of patrilocality. Given that both mtDNA and language are maternally transmitted, the incorporation of local Iranian women would have resulted in the concomitant replacement of the ancestral Caucasian language and mtDNA types of the Gilaki and Mazandarani with their current Iranian language and mtDNA types. Concomitant replacement of language and mtDNA may be a more general phenomenon than previously recognized.     

Association patterns and shoal fidelity in the three-spined stickleback

We investigated pairwise association patterns and shoal fidelity in free-ranging, individual three-spine sticklebacks (Gasterosteus aculeatus) by capturing entire shoals of sticklebacks and tagging each shoal member with a unique individual mark before releasing the shoal at the point of capture. We recaptured tagged fishes in the study area on five subsequent days, noting their identity, their location and the individuals with which they were associated. Stable partner associations between fishes were observed which might provide the basis for shoal fidelity via social networks. These results suggest the potential for the kinds of inter-individual association patterns assumed by models of predator inspection and 'tit-for-tat' behaviours in free-ranging fishes.     

Distribution and evolution of Carboniferous reefs in South China

Reefs are sensitive proxies for palaeontological, palaeoenvironmental, and palaeogeographical changes during geological history. In South China, after the collapse of the reef ecosystem during the Frasnian-Famennian and Hangenberg mass extinction events, Carboniferous reefs underwent evolutionary episodes of recovery, decline, and turnover, which were controlled by changes of reef-builders abundance, sedimentary facies, relative sea level, and even global climate. In Tournaisian times, only a few Waulsortian-like banks have been found in Liuzhou, Guangxi without metazoan reefs, which were caused by the lack of reef-builders, such as colonial rugose corals and bryozoans, and the dominant non-carbonate facies (shale, mud stone and sandstone) driven by low relative sea level. The absence of mud mounds in the early Viséan was attributed to the regression event during the Tournaisian-Viséan boundary. During Viséan times, bryozoan-coral reefs in Huishui, Guizhou and Tianlin, Guangxi occurred during a time of increasing biodiversity and carbonate facies resulting from relative sea-level rise. The number of potential reef-builders as colonial rugose coral and bryozoan genera significantly increased in Viséan times in South China. The reef abundance declined during Serpukhovian times in South China and the controlling factors were decreasing abundance of potential reef-builders and developing non-carbonate facies due to a relative sea-level fall. The sedimentary facies were characterized by shale, mud stone, sandstone, and dolostone during this time. A distinct change in reef types occurred after the Mississippian-Pennsylvanian boundary, when phylloid algae and red algae reefs (distributed in Ziyun, Guizhou and Beibuwan, Guangxi) replaced metazoan reefs and became the dominant role in reef ecosystem. This reef turnover event may be triggered by the dramatic relative sea-level fall during the mid-Carboniferous, and continued low relative sea level in South China and global flourish of phylloid and red algae during Pennsylvanian times. Grainstone and dolomitic limestone were the main composition of the platform sedimentary facies in South China during Pennsylvanian times. In addition, global climate cooling and warming, resulted from the waxing and waning of Gondwana glaciation, may also influence the reef evolution in South China, as evidenced from the consistent transgression and regression events and reef evolutionary pattern between South China and globe during the Carboniferous.