175 research outputs found

    Reproductive strategies of the kangaroo leech, Marsupiobdella africana (Glossiphoniidae)

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    AbstractThe Kangaroo Leech, Marsupiobdella africana, is a hermaphroditic organism, with insemination taking place by the planting of a spermatophore on another leech. Spermatophores are mostly planted on the anterior of the recipient leech, but not always. Several spermatophores may be planted by different leeches on a single recipient. The spermatophore consists of two side by side lobes. Within minutes from planting of the spermatophore, the contents are squeezed out and into the body of the recipient. Sperm are believed to find the way to the ova by following chemical cues. Kangaroo Leeches display advanced parental care by transferring fertilized eggs from the reproductive opening to a brood pouch on the ventral side. Fully developed leeches may copulate after detaching from the amphibian host Xenopus laevis, or from the Cape River Crab Potamonautes perlatus with which it maintains a phoretic association

    Developing a Methodology for Online Service Failure Prevention: Reporting on an Action Design Research Project-in-Progress

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    The increasing use of online channels for service delivery raises new challenges in service failure prevention. This work-in-progress paper reports on the first phase of an action-design research project to develop a service failure prevention methodology. In this paper we review the literature on online services, failure prevention and failure recovery and develop a theoretical framework for online service failure prevention. This provides the theoretical grounding for the artefact (the methodology) to be developed. We use this framework to develop an initial draft of our methodology. We then outline the remaining phases of the research, and offer some initial conclusions gained from the project to date

    Short Communication: The rate of release of Cry1Ab protein from Bt maize leaves into water

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    Transgenic Bt maize plants are genetically modified to contain genes of Bacillus thuringiensis that encode for δ-endotoxins (Cry1Ab protein) that have insecticidal properties. These endotoxins target certain lepidopteran pests of maize. There are several entry routes by which Cry proteins enter the aquatic ecosystem in which aquatic organisms are exposed to these proteins. The main route is through plant debris such as leaves, stalks and postharvest detritus that are transported by means of run-off, rain and wind. While several studies have been conducted on the fate of Cry1Ab protein in terrestrial ecosystems, little is known of the release rates of Cry1Ab proteins from maize plant tissues that end up in aquatic ecosystems. In this study, leaves of Bt-maize and its isoline were submerged in containers filled with deionised or borehole water for a period of 16 days, and kept at 3 different temperatures (10±1, 21±1 and 30±1°C). Samples were collected at 1, 2, 4, 8, 16, 24, 48, 96, 192 and 384 h post submersion and analysed for Cry protein content using enzyme-linked immunosorbent assay (ELISA). The release of Cry protein from submerged maize leaves was influenced by temperature, and duration of immersion. An increase in Cry protein levels in the water was observed from the first hour onwards in both water types until the end of the experiment. The highest concentration of Cry protein was found at 30°C. This study showed that temperature and time period influence the release rate of Cry proteins from dried leaf matter into the aquatic environment.Keywords: aquatic ecosystem, arthropods, GM crops, environment, risk assessmen

    Novel Information on the Morphology, Phylogeny and Distribution of Camallanid Mematodes from Marine and Freshwater Hosts in South Africa, Including the Description of \u3ci\u3eCamallanus sodwanaensis\u3c/i\u3e n. sp.

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    Four species of previously known nematodes from the family Camallanidae were found from different hosts in South Africa: Batrachocamallanus xenopodis from the frog Xenopus muelleri, Paracamallanus cyathopharynx, and Procamallanus pseudolaeviconchus from the catfish Clarias gariepinus and Spirocamallanus daleneae from the catfish Synodontis zambezensis. In the material collected from various marine fishes, several specimens of nematodes from the genus Camallanus clearly differed from all previously known species. Based on morphological differences these specimens are assigned to a new species, C. sodwanaensis. Molecular data of 18S and 28S rDNA and COI sequences are provided for the collected species and a phylogenetic analyses based on 28S gene fragments are presented

    Customised high-value document generation

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    International audienceContributions of different experts to innovation projects improve enterprise value, captured in documents. A subset of them is the centre of expert constraint convergence. Their production needs to be tailored case by case. Documents are often considered as knowledge transcription. As the base of a structured knowledge-based information environment, this paper presents a global approach that helps knowledge-integration tool deployment. An example, based on process plan in aircraft manufacturing, indicates how fundamental understanding of domain infrastructure contributes to a more coherent architecture of knowledge-based information environments. A comparison with an experiment in insurance services generalised the application of presented principles

    Revision of the systematics of the Polystomoidinae (Platyhelminthes, Monogenea, Polystomatidae) with redefinition of Polystomoides Ward, 1917 and Uteropolystomoides Tinsley, 2017

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    Polystomatids are platyhelminth parasites that infect mainly amphibians and freshwater turtles. For more than seven decades, chelonian polystomes were classified into three genera according to the number of hamuli, i.e. absent for Neopolystoma, one pair for Polystomoidella and two pairs for Polystomoides. Following re-examination of morphological characters, seven new genera were erected the past six years, namely Apaloneotrema, Aussietrema, Fornixtrema, Manotrema, Pleurodirotrema, Uropolystomoides and Uteropolystomoides. However, the polyphyly of Neopolystoma and Polystomoides on the one hand, and the nested position of Uteropolystomoides within a clade encompassing all Neopolystoma and Polystomoides spp. on the other, still raised questions about the validity of these genera. We therefore re-examined several types, paratypes and voucher specimens, and investigated the molecular phylogeny of polystomes sampled from the oral cavity of North American turtles to re-evaluate their systematic status. We show that all Polystomoides Ward, 1917, sensu Du Preez et al., 2022, Neopolystoma Price, 1939, sensu Du Preez et al., 2022 and Uteropolystomoides Tinsley, 2017 species, display vaginae that are peripheral and extend well beyond the intestine. We thus reassign all species of the clade to Polystomoides and propose nine new combinations; however, although Uteropolystomoides is nested within this clade, based on its unique morphological features, we propose to keep it as a valid taxon. Polystomoides as redefined herein groups all polystome species infecting either the oral cavity or the urinary bladder of cryptodires, with peripheral vaginae and with or without two pairs of small hamuli. Uteropolystomoides nelsoni (Du Preez & Van Rooyen 2015), originally described from Pseudemys nelsoni Carr is now regarded as Uteropolystomoides multifalx (Stunkard, 1924) n. comb. infecting three distinct Pseudemys species of North America

    Taxonomic re-evaluation of African anuran trypanosomes with the redescription and molecular diagnosis of Trypanosoma (Trypanosoma) nelspruitense Laveran, 1904 and Trypanosoma (Haematomonas) grandicolor Pienaar, 1962

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    The aquatic and terrestrial clades of species of Trypanosoma could provide insight into the evolutionary history of the genus, as well as complementary information for biomedical studies of medically and economically important species of Trypanosoma. The ecological interactions and phylogeny of aquatic trypanosomes are currently not well-understood, mostly due to their complex life cycles and a deficiency of data. The species of Trypanosoma from African anuran hosts are of the least understood taxa in the genus. Trypanosomes were collected from South African frogs and subjected to morphological and phylogenetic analyses. This study redescribes Trypanosoma (Trypanosoma) nelspruitense Laveran, 1904 and Trypanosoma (Haematomonas) grandicolor Pienaar, 1962, with morphological and molecular data. The present study aims to create a platform for further future research on African anuran trypanosomes

    A molecular survey across Madagascar does not yield positive records of the amphibian chytrid fungus Batrachochytrium dendrobatidis.

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    Madagascar harbors a rich and diverse amphibian fauna, with over 280 nominal species of native frogs, all of which are endemic to the island. Although many species are threatened predominantly by habitat destruction, so far this fauna has not experienced any enigmatic declines as amphibians have in other parts of the globe. The amphibian chytrid fungus Batrachochytrium dendrobatidis (Bd), associated with mass amphibian die offs in Europe, the Americas and Australia has so far not been detected in Madagascar, but surveys so far were based mainly on histological examination of frog samples, with molecular data from only a single site. Here, we present results from a molecular screening of altogether 300 frog specimens belonging to 53 species in 13 genera, from 12 sites throughout Madagascar spanning all of Madagascar`s major bioclimatic regions and an array of different elevations from 20 to 2400 m above sea level. All samples were analyzed using a standard quantitative real time polymerase chain reaction (qPCR) assay and yielded only negative results, suggesting the widespread absence or very localized and low prevalence of the amphibian chytrid fungus across Madagascar during the sampling years 2006 and 2007.This research was supported by Conservation International, by the Spanish Ministry of Science, by the Volkswagen Foundation, and by The US National Science Foundation (EF-0723563 and 1120283)Peer Reviewe
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