Resumption of oestrous behaviour and cyclic ovarian activity in suckling and non-suckling ewes

In Préalpes de Sud ewes after an autumn lambing, the mean post-partum interval to first LH surge was 10 +/- 1 days and 17 +/- 1 days for non-suckling and suckling ewes, respectively. Post-partum interval to first luteal phase, estimated from plasma progesterone concentrations, was similar in non-suckling and suckling ewes (27 +/- 1 days and 28 +/- 5 days, respectively). Interval to first oestrus was shorter in non-suckling (22 +/- 2 days) than in suckling ewes (35 +/- 2 days) but these first oestrous periods were followed by short luteal phases in 60% (12/20) of non-suckling ewes and in only 7% (2/29) of suckling ewes. Finally, suckling slightly postponed the resumption of the first oestrus followed by a normal oestrous cycle (37 +/- 1 days versus 31 +/- 2 days) because progesterone, essential for oestrus expression, was secreted mainly during normal luteal phases in 70% (21/30) of suckling ewes and during short cycles in 95% (21/22) of non-suckling ewes. Therefore, the primary consequence of suckling is to regulate the conditions of resumption of cyclic ovarian activity after parturition.     

Successful use of oviduct epithelial cell coculture for in vitro production of viable red deer (Cervus elaphus) embryos

Techniques for in vitro production (IVP) of viable embryos have been thoroughly developed in several domestic species in view to improve breeding efficiency. When applied to wild life, these techniques may also help the maintenance of biodiversity through amplification of sparse animals offspring and facilitation of genetic material exchange. During the successive steps of IVP, i.e. oocyte in vitro maturation (IVM), fertilization (IVF) and early embryo development (IVD) to the blastocyst stage, gametes and embryos are faced with unusual environment, including oxidative stress, known to be detrimental to their survival. In the present study, starting from methods developed in domestic species, we have adapted IVP to produce viable red deer embryos. In a first experiment, cumulus cells were removed from in vitro matured oocytes either before or after IVF. The presence of cumulus cells during IVF did not affect final cleavage or development rates. In a second experiment, in vitro matured oocytes were fertilized in the presence of cumulus cells and cultured in SOFaaBSA medium alone or in the presence of ovine oviduct epithelial cell (oOEC) monolayer. Whereas, oviduct cells did not improve the cleavage rate, they significantly increased the rate of embryos reaching the blastocyst stage (from 3 to 25% of total oocytes). Ten blastocysts from oOEC coculture were transferred after freezing and thawing to five recipient hinds and gave rise to three pregnancies. The three pregnant hinds gave birth to three live and normal calves.     

Have chondracanthid copepods co-speciated with their teleost hosts?

Chondracanthid copepods parasitise many teleost species and have a mobile larval stage. It has been suggested that copepod parasites, with free-living infective stages that infect hosts by attaching to their external surfaces, will have co-evolved with their hosts. We examined copepods from the genus Chondracanthus and their teleost hosts for evidence of a close co-evolutionary association by comparing host and parasite phylogenies using TreeMap analysis. In general, significant co-speciation was observed and instances of host switching were rare. The prevalence of intra-host speciation events was high relative to other such studies and may relate to the large geographical distances over which hosts are spread.     

Spatial and temporal predictability of the parasite community structure of a benthic marine fish along its distributional range

The search for consistent patterns of organisation in parasite communities remains a central theme in parasite community ecology. However, to date, much evidence comes from studies without replication in both space and time; when replicate communities are examined, repeatable patterns are rarely observed. Here we determine, using nested subset analyses, whether the infracommunities of ectoparasites and endoparasites of a benthic marine fish (Sebastes capensis) show non-random structure. Then we examine the spatial repeatability of parasite community structure across the host's distribution in the southern Pacific, and the temporal repeatability of ectoparasite community structure from one locality. In total, 537 fish were captured from different latitudes (between 11 degrees S and 52 degrees S) along the Pacific coast of South America; a further 122 specimens were captured in two other years from one of the sampling localities, Valdivia (40 degrees S). In spite of variation in fish sizes among samples, fish size generally did not correlate with either ecto- or endoparasite species richness. The ecto- and endoparasite species richness of the component communities were also not correlated with fish sample size across the nine localities. Significant nested patterns were found in the ectoparasite communities of S. capensis at all eight localities, except at latitude 52 degrees S. Significant nested patterns were also found in the endoparasite infracommunities of S. capensis at seven of the nine localities, the exceptions being those from latitudes 11 degrees S and 20 degrees S. On a temporal scale, significant nestedness was observed in the ectoparasite infracommunities of S. capensis during each of the 3 years of sampling at Valdivia. In general, the same parasite species are responsible for the repeatability of nested patterns, though their importance varies among localities. The spatial and temporal predictability of the parasite community structure in S. capensis may be associated with the fish's benthic habitat and territorial behavior, suggesting that host biology may be a key determinant of the structure of parasite communities.     

Genetic structure in remnant populations of an endangered cyprinodontid fish, <Emphasis Type="Italic">Orestias ascotanensis</Emphasis>, endemic to the Ascotán salt pan of the Altiplano

The impact of recent habitat fragmentation on population genetic diversity and structure has often been studied, mainly related to anthropogenic causes; however its long-term effect has been much less evaluated. In this study we analyzed the genetic variability of Orestias ascotanensis, a fish endemic to the Ascotán salt pan of Chile. This species, which formed a single and large population during the last wet period that ended 10,000 years ago, is currently represented by small populations inhabiting freshwater springs on the eastern border of the salt pan. Therefore, this species represents a unique model to evaluate the consequences of a drastic habitat fragmentation process that initiated thousands of years ago. Analysis of the control region of the mitochondrial DNA revealed high genetic diversity (haplotipic diversity ranged between 0.78 and 0.94) and marked differences among populations (Φ_ST = 0.46). Estimated effective population sizes greatly surpassed the real sizes, particularly among springs that remained connected. These results reflect the long-term consequences of habitat fragmentation on natural populations: structuring of the populations and loss of genetic diversity of the isolated fragments.     

Distribution of transfer RNA genes in thePisum sativum chloroplast DNA

Purified chloroplast tRNAs were isolated fromPisum sativum leaves and radioactively labeled at their 3′ end using tRNA nucleotidyl transferase and α³²P-labeled CTP. Pea ctDNA was fragmented using a number of restriction endonucleases and hybridized with thein vitro labeled chloroplast tRNAs by DNA transfer method. Genes for tRNAs have been found to be dispersed throughout the chloroplast genome. A closer analysis of the several hybrid regions using recombinant DNA plasmids have shown that tRNA genes are localized in the chloroplast genome in both single and multiple arrangements. Two dimensional gel electrophoresis of total ct tRNA have identified 36 spots. All of them have been found to hybridize withPisum sativum ctDNA. Using recombinant clones, 30 of the tRNA spots have been mapped inPisum sativum ctDNA.     

Latitudinal gradient in the taxonomic composition of parasite communities

Although latitudinal gradients in diversity have been well studied, latitudinal variation in the taxonomic composition of communities has received less attention. Here, we use a large dataset including 950 surveys of helminth endoparasite communities in 650 species of vertebrate hosts to test for latitudinal changes in the relative contributions of trematodes, cestodes, nematodes and acanthocephalans to parasite assemblages. Although the species richness of helminth communities showed no consistent latitudinal variation, their taxonomic composition varied as a function of both host type and latitude. First, trematodes and acanthocephalans accounted for a higher proportion of species in helminth communities of fish, whereas nematodes achieved a higher proportion of the species in communities of bird and especially mammal hosts. Second, the proportion of trematodes in helminth communities of birds and mammals increased toward higher latitudes. Finally, the proportion of nematodes per community increased toward lower latitudes regardless of the type of host. We present tentative explanations for these patterns, and argue that new insights in parasite community ecology can be gained by searching for latitudinal gradients not only in parasite species richness, but also in the taxonomic composition of parasite assemblages.     

The <Emphasis Type="Italic">Caenorhabditis elegans</Emphasis>CDT-2 ubiquitin ligase is required for attenuation of EGFR signalling in vulva precursor cells

Background  

Attenuation of the EGFR (Epidermal Growth Factor Receptor) signalling cascade is crucial to control cell fate during development. A candidate-based RNAi approach in C. elegans identified CDT-2 as an attenuator of LET-23 (EGFR) signalling. Human CDT2 is a component of the conserved CDT2/CUL4/DDB1 ubiquitin ligase complex that plays a critical role in DNA replication and G2/M checkpoint. Within this complex, CDT2 is responsible for substrate recognition. This ubiquitin ligase complex has been shown in various organisms, including C. elegans, to target the replication-licensing factor CDT1, and the CDK inhibitor p21. However, no previous link to EGFR signalling has been identified.     

Thaumamermis zealandica n sp (Mermithidae: Nematoda) parasitising the intertidal marine amphipod Talorchestia quoyana (Talitridae: Amphipoda) in New Zealand,with a summary of mermithids infecting amphipods

A new nematode, Thaumamermis zealandica n. sp. (Mermithidae; Nematoda), is described parasitising the intertidal marine amphipod Talorchestia quoyana Milne-Edwards (Talitridae) from the coast of South Island, New Zealand. The new species is characterised by the degree of dimorphism of the spicules, the arrangement of the genital papillae, the shape and length of the vagina and the anteriorly-placed amphids. This is the first known marine host of a member of the family Mermithidae. Published records of mermithid nematodes from amphipods are presented.