Yeasts in amphibians are common: isolation and the first molecular characterization from Thailand

A survey of the presence of yeasts in frogs and toads in Thailand was conducted using standard mycological examination techniques. The results, which were confirmed with molecular techniques, revealed the presence of five yeast species-Cryptococcus liquefaciens, C. heveanensis, Pseudozyma hubeiensis, Rhodotorula mucilaginosa and R. minuta-in the bile of these amphibians. Although previous works have isolated yeasts from amphibian gastrointestinal tracts and skin, it is questionable whether these yeasts were acquired by ingestion or were commensals on adult individuals. Frog farms, an urban area and protected natural areas were surveyed and all tested positive for yeasts, which shows their ubiquity in both wild and farm-reared frogs. Additionally, the finding of yeasts in five different species of frogs and toads shows that there is a wide spectrum of hosts in this vertebrate group. Our results thus suggest that yeasts are likely to be widespread among amphibians in different habitat types and in a wide range of host species

Spermatological characteristics of the family Glypthelminthidae (Digenea, Plagiorchioidea) inferred from the ultrastructural study of Glypthelmins staffordi Tubangui, 1928

The present study describes the ultrastructural organization of the mature spermatozoon of the digenean Glypthelmins staffordi (Glypthelminthidae) by means of transmission electron microscopy. Live digeneans were collected from the Chinese edible frog (Hoplobatrachus rugulosus) in Udon Thani Province (Thailand). The ultrastructural study reveals that the mature spermatozoon of G. staffordi is a filiform cell, which is tapered at both extremities. It exhibits the Bakhoum et al.'s type IV of spermatozoon of digeneans characterized by the 9+'1' axonemes of trepaxonematan Platyhelminthes, the presence of the association 'external ornamentation-cortical microtubules', the external ornamentation located in the posterior part of the anterior region, the arrangement of parallel cortical microtubules in two bundles and with its maximum number located in the anterior part of the sperm cell, and the presence of two mitochondria. Other characteristics are the presence of spine-like bodies, a posterior extremity containing only the nucleus, and the presence of a large amount of glycogen granules. Results of the present study are particularly compared with the existing data in other families of the Plagiorchioidea, namely the Brachycoeliidae, the Haematoloechidae, the Omphalometridae and the Plagiorchiidae

Sperm characteristics in the digenean Diplodiscus amphichrus (Paramphistomoidea, Diplodiscidae), a parasite of the Chinese edible frog Hoplobatrachus rugulosus

The ultrastructural characteristics of the mature spermatozoon of Diplodiscus amphichrus (Digenea, Paramphistomoidea, Diplodiscidae) and their ultrastructural organisation were examined by means of transmission electron microscopy. Live digeneans were collected from the Chinese edible frog Hoplobatrachus rugulosus in Thailand. The male gamete of D. amphichrus is a fliform cell with two axonemes of the 9+'1' trepaxonematan pattern, nucleus, one mitochondrion, parallel cortical microtubules, a well-developed lateral expansion, external ornamentation of the plasma membrane, spine-like bodies, and granules of glycogen. These ultrastructural characteristics have already been described in other paramphistomoids studied so far except for the cladorchiids, which present some diferences. Two characteristics of the male gamete of D. amphichrus were found for the frst time in a digenean: (i) the appearance of the initial part of the lateral expansion before the axonemes in the anterior extremity and (ii) the separation between the second axoneme and the nucleus in the posterior tip. Our results are compared with the available data in the Digenea and particularly with other paramphistomoids

Search and characterisation of genes expressed in the gonads and brain of Oreochromis niloticus to be used as putative sex-linked markers to produce male monosex populations by environmentally-friendly approaches

La connaissance et la maîtrise du déterminisme du sexe et de la différenciation sont des défis majeurs pour la production de tilapia. L'élevage de populations monosexes mâles évite les effets négatifs d'une reproduction continue et profite de la meilleure croissance des mâles. Dans le contexte d'une aquaculture durable, le développement de stratégies alternatives et écologiques est nécessaire pour le contrôle du sexe du tilapia sans avoir recours aux approches hormonales. Ces alternatives reposent sur des approches génétiques ou environnementales, en utilisant l'effet masculinisant des températures élevées appliquées au cours de la différenciation sexuelle. Dans cette thèse la recherche de gènes impliqués dans la différenciation sexuelle a été réalisée dans les gonades et le cerveau en utilisant l'analyse de certains gènes candidats. L'objectif était de développer des marqueurs putatifs pour produire des populations monosexes mâles par des approches respectueuses des consommateurs et de l'environnement. Les expressions temporelles et spatiales de cyp19a1a, cyp19a1b, FOXL2, dmrt1, SOX9, DAX1 et amh ont été analysées dans plusieurs descendances de mâles ou des femelles génétiques ainsi que dans des femelles traitées à fortes températures. Leur lien avec les masculinisations par la températ ure a également été recherché sur des lignées thermosensibles de tilapia. L'un des gènes qui présente un dimorphisme sexuel important est l'amh qui est exprimé aussi bien dans les gonades que dans le cerveau pendant les premiers stades de la différenciation sexuelle. Le niveau d'expression de l'amh dans le cerveau est élevé chez les mâles quand les gonades sont toujours indifférenciées et probablement même avant la synthèse des stéroïdes gonadique. Une procédure de sexage moléculaire précoce a été développée en utilisant ce gène chez le tilapia. Cette procédure sera d'un grand intérêt pour les éleveurs et les scientifiques pour identifier rapidement des individus YY mâles avec un gain en temps et en argent, et pourra être utilisée également pour rechercher d'autres approches fiables de production de populations monosexes mâles sans l'utilisation des hormones.Knowledge and the control of sex determination and differentiation are major challenges for tilapia production. Farming of male monosex populations avoids the negative effects of a continuous reproduction and benefits from males' fast growth. In the context of a sustainable aquaculture, alternative and ecological strategies have to be developed to control sex in tilapia without hormonal treatment. These approaches will rely on genetic and environmental treatments, such as the use of masculinising high temperatures applied during sex differentiation. The search for genes implicated in sex differentiation has been performed in both gonads and brains using the analysis of candidate genes. The objective was to develop putative markers to produce male monosex populations through consumer and environmentally friendly approaches. Temporal and organ expressions of cyp19a1a, cyp19a1b, foxl2, dmrt1, sox9, dax1 and amh were analysed in several progenies o f genetic males or females as well as in temperature-treated individuals. Their link with temperature masculinisation was also performed on the thermosensitive tilapia lines. One of the sexual dimorphic genes was amh which was found expressed in both gonads and brains during early stages of sex-differentiation. Brain amh was elevated in males when the gonads were still undifferentiated and probably before steroid synthesis took place. A precocious molecular sexing procedure was developed in tilapia using this gene. This procedure will be of great advantage for both farmers and scientists in identifying quickly male individuals and in finding reliable male monosex approaches not using hormones

Yeasts in amphibians are common: isolation and the first molecular characterization from Thailand

<p>A survey of the presence of yeasts in frogs and toads in Thailand was conducted using standard mycological examination techniques. The results, which were confirmed with molecular techniques, revealed the presence of five yeast species – <em>Cryptococcus liquefaciens, C. heveanensis</em>, <em>Pseudozyma hubeiensis, Rhodotorula mucilaginosa</em> and<em> R. minuta</em> – in the bile of these amphibians. Although previous works have isolated yeasts from amphibian gastrointestinal tracts and skin, it is questionable whether these yeasts were acquired by ingestion or were commensals on adult individuals. Frog farms, an urban area and protected natural areas were surveyed and all tested positive for yeasts, which shows their ubiquity in both wild and farm-reared frogs. Additionally, the finding of yeasts in five different species of frogs and toads shows that there is a wide spectrum of hosts in this vertebrate group. Our results thus suggest that yeasts are likely to be widespread among amphibians in different habitat types and in a wide range of host species.</p

Yeasts in amphibians are common: isolation and the first molecular characterization from Thailand

A survey of the presence of yeasts in frogs and toads in Thailand was conducted using standard mycological examination techniques. The results, which were confirmed with molecular techniques, revealed the presence of five yeast species – Cryptococcus liquefaciens, C. heveanensis, Pseudozyma hubeiensis, Rhodotorula mucilaginosa and R. minuta – in the bile of these amphibians. Although previous works have isolated yeasts from amphibian gastrointestinal tracts and skin, it is questionable whether these yeasts were acquired by ingestion or were commensals on adult individuals. Frog farms, an urban area and protected natural areas were surveyed and all tested positive for yeasts, which shows their ubiquity in both wild and farm-reared frogs. Additionally, the finding of yeasts in five different species of frogs and toads shows that there is a wide spectrum of hosts in this vertebrate group. Our results thus suggest that yeasts are likely to be widespread among amphibians in different habitat types and in a wide range of host species

Whipworm diversity in West African rodents: a molecular approach and the description of Trichuris duplantieri n. sp (Nematoda: Trichuridae)

Whipworms were collected from rodents (Muridae) from six West African countries: Burkina-Faso, the Islamic Republic of Mauritania, and the Republics of Benin, Guinea, Mali and Senegal. Molecular sequences (ITS-1, 5.8S and ITS-2 of the ribosomal DNA gene) and morphometric characters were analysed in Trichuris (Nematoda: Trichuridae) specimens found in seven host species: Arvicanthis niloticus, Gerbilliscus gambianus, Gerbillus gerbillus, G. tarabuli, Mastomys erythroleucus, M. huberti and M. natalensis. Phylogenetic analyses revealed three clades, one recognised as Trichuris mastomysi, previously recorded in M. natalensis from Tanzania, and the other two previously undescribed. A new species named Trichuris duplantieri n. sp., found in Gerbillus spp. from Mauritania, was characterised using molecular and morphometric methods

Temperature induced-masculinisation in the Nile tilapia causes rapid up-regulation of both dmrt1 and amh expressions

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