Variation in intensity of a parasitic mite (Spinturnix myoti) in relation to the reproductive cycle and immunocompetence of its bat host (Myotis myotis)

Given the intimate association in host-parasite systems, parasites are expected to initiate their own reproduction when vulnerable hosts become abundant and/or when adult hosts are less resistant. In this study, we examined the variation in the intensities of a blood-sucking mite (Spinturnix myoti, Acarina) with respect to the reproductive cycle and immunocompetence of its host, the greater mouse-eared bat Myotis myotis. Reproductive, pregnant females were less immunocompetent and harboured more parasites than nonreproductive females, whilst, during lactation, immunocompetence was positively associated with female body mass. There was a dramatic increase in the T-cell response of gravid females with the advancement of gestation, which coincided with a diminution of individual parasite loads and a progressive switch of parasites from adults to juveniles. The latter not only harboured greater numbers of mites than adult female bats, but they also exhibited gravid parasites in higher proportions, indicating that juvenile hosts are more attractive for parasite reproduction than adult females.

Relationship of mating systems and metabolic rate with cycle length of spermatogenesis and sperm production rate in shrews

SUMMARY : The shrews are among the most ancient of living eutherian mammals. They represent an interesting comparative model because of their extreme divergent species. The two shrew subfamilies, Soricinae and Crocidurinae are characterized by fundamental differences concerning their metabolic rates, litter size, period of gestation and different mating pattern. In this study we established and compared the sperm characteristics in four species of different genera of shrews (Sorex araneus, Neomys fodiens, Crocidura russula and Suncus murinus) in the context of the sperm competition hypothesis. The sperm competition concerns the competition between ejaculates of different males for fertilization of ova of a female within a single estrus period. As expected, a greater relative testis size (indicating the importance of polyandry) was associated with a higher number of cauda epididymal spermatozoa, higher level of circulating testosterone and a higher percentage of progressive sperm motility. In addition, we investigated if the basal metabolic rate (BMR) and relative testis size (RTS) may be correlated with the cycle length of spermatogenesis. In this purpose, we determined and compared the cycle length of spermatogenesis in six species of shrews belonging to two subfamilies: Soiricinae (Sorex araneus, Sorex coronatus, Sorex minutus, Neomys fodiens) and Crocidurinae (Crocidura russula, Sunctes murinus). Our results indicate that sperm competition and metabolic rate may act independently or together reducing cycle length of spermatogenesis and thus increase sperm production. We finally investigated this correlation across 32 mammalian species. After testing the data for phylogenetic independence, our results showed that BMR explained only 21 % of the variation, while the RTS explained 44% of the variation of the cycle length of spermatogenesis. The level of the sperm competition, indicated by RTS, is thus to our knowledge the most important factor influencing the speed of spermatogenesis in mammals. RESUME : Les musaraignes sont parmi les plus anciens mammifères vivants. Grâce à leurs extrêmes divergences, ils sont souvent utilisés comme modèles dans des études comparatives. Les deux sous-familles Soricinae et Crocidurinae sont caractérisées par des différences fondamentales, notamment en termes d'intensité du métabolisme, des stratégies de reproduction et du comportement social. Dans la première partie de cette étude, nous avons établi et comparé certaines "caractéristiques des spermatozoïdes chez quatre espèces de musaraignes appartenant à des genres différents (Sorex araneus, Neomys fodiens, Crocidura russula et Suncus murinus). Les résultats ont été interprétés dans le contexte de la théorie de la compétition spermatique, c'est-à-dire la compétition entre le sperme de deux ou plusieurs mâles pour féconder un maximum d'ovules de la même femelle. Cette compétition spermatique peut amener à certaines adaptations biologiques afin de produire plus de sperme. Comme attendu, une grande taille relative des testicules est associée à un nombre élevé de spermatozoïdes, dont la majorité présente une mobilité progressive. Un taux élévé de testostérone a également été observé. De plus, nous avons étudié l'influence du métabolisme basal ainsi que l'intensité de la compétition spermatique sur la durée du cycle de la spermatogenèse. Dans ce but, nous avons déterminé et comparé les durées de la spermatogenèse chez six espèces de musaraignes appartenant à deux sous-familles : Soricinae (Sorex araneus, Sorex coronatus, Sorex minutus, Neomys fodiens) et Crocidurinae (Crocidura russula, Suncus murinus). Les résultats obtenus indiquent que ces deux facteurs (l'intensité du métabolisme basal et de la compétition spermatique) agissent d'une manière dépendante ou indépendante dans le même sens. La conséquence de ces actions est une diminution de la durée de la spermatogenèse entraînant une augmentation de la production de spermatozoïdes. Nous avons finalement étudié ce phénomène dans l'ensemble des mammifères. Après avoir testé l'indépendance phylogénétique, nos résultats montrent que l'intensité de la compétition spermatique indiquée par le RTS est mieux corrélée avec la régulation de la durée de la spermatogenèse qu'avec l'intensité du métabolisme.

False phylogenies on wood mice due to cryptic cytochrome-b pseudogene.

The phylogeny and phylogeography of the Old World wood mice (subgenus Sylvaemus, genus Apodemus, Muridae) are well-documented. Nevertheless, the distributions of species, such as A. fulvipectus and A. ponticus remain dubious, as well as their phylogenetic relationships with A. sylvaticus. We analysed samples of Apodemus spp. across Europe using the mitochondrial cytochrome-b gene (cyt-b) and compared the DNA and amino-acid compositions of previously published sequences. The main result stemming from this study is the presence of a well-differentiated lineage of Sylvaemus including samples of various species (A. sylvaticus, A. fulvipectus, A. ponticus) from distant locations, which were revealed to be nuclear copies of the mitochondrial cyt-b. The presence of this cryptic pseudogene in published sequences is supported by different pathways. This has led to important errors in previous molecular trees and hence to partial misinterpretations in the phylogeny of Apodemus.

Risk assessment of recurrence in sporadic retinoblastoma using a molecular-based algorithm

Le rétinoblastome (Rb) est une tumeur provenant des cellules rétiniennes progénitrices des photorécepteurs. C'est la tumeur pédiatrique maligne la plus fréquente avec une incidence par naissance évaluée entre 1/15Ό00 et 1/20Ό00. Les enfants atteints de Rb sont diagnostiqué dans leur grande majorité avant l'âge de 4 ans, soit le temps nécessaire à la différentiation et à la maturation des photorécepteurs et donc à la disparition de la cellule d'origine du Rb. La survie du patient, la sauvegarde oculaire et le pronostic visuel restent excellents pour autant que le traitement ne soit pas différé. Dans sa variante non héréditaire (60%) le Rb est toujours unilatéral et sporadique. Le Rb héréditaire de transmission dominante autosomique (40%), se décline sous toutes les formes, familiale (10%) ou sporadique (30%), que l'atteinte soit unilatérale ou bilatérale. La majorité des mutations causales sont uniques et distribuées de façon aléatoire sur la totalité du gène RB1 sans région prédisposante. La détection de ces mutations est couteuse et chronophage, tout en présentant un taux de détection relativement bas; surtout dans les cas de Rb sporadiques unilatéraux. Dans le but d'identifier les patients présentant un risque réel de développer un Rb, et de réduire le nombre d'examens sous narcose requis pour le dépistage de la maladie chez les sujets à risque, nous avons développé une stratégie sensible, rapide, efficace et peu couteuse basée sur une analyse de l'haplotype intragénique. Cet algorithme prend en compte a) la perte d'hétérozygotie intratumorale du gène RB1, b) l'origine paternelle préférentielle des nouvelles mutations germinales et c) un risque a priori dérivé des données empiriques de Vogel. Pendant la période allant de janvier 1994 à décembre 2006, nous avons comparé l'apparition de nouveau Rb parmi la fratrie et la descendance de patient atteints au nombre de nouveaux cas attendus calculé par notre algorithme. 134 familles ont été étudiées. L'analyse moléculaire a été effectuée chez 570 personnes dont 99 patients âgés de moins de 4 ans et donc à risque de développer un Rb. Parmi cette cohorte, nous avons observé l'apparition d'un cas de Rb, alors que les risques cumulés a posteriori calculé par notre algorithme prédisait l'apparition de 1.77 nouveau cas. Dans cette étude, nous avons pu valider notre algorithme prédisant la récurrence de Rb chez les parents de 1er degré de patients atteints. Cet outil devrait grandement faciliter le conseil génétique ainsi que le suivi des patients à risque de développer un Rb, surtout dans les cas ou le séquençage direct du gène RB1 n'est pas disponible ou est resté non informatif. - Purpose: Most RBI mutations are unique and distributed throughout the RBI gene. Their detection can be time-consuming and the yield especially low in cases of conservatively-treated sporadic unilateral retinoblas-toma (Rb) patients. In order to identify patients with true risk of developing Rb, and to reduce the number of unnecessary examinations under anesthesia in all other cases, we developed a universal sensitive, efficient and cost-effective strategy based on intragenic haplotype analysis. Methods: This algorithm allows the calculation of the a posteriori risk of developing Rb and takes into account (a) RBI loss of heterozygosity in tumors, (b) preferential paternal origin of new germline mutations, (c) a priori risk derived from empirical data by Vogel, and (d) disease penetrance of 90% in most cases. We report the occurrence of Rb in first degree relatives of patients with sporadic Rb who visited the Jules Gonin Eye Hospital, Lausanne, Switzerland, from January 1994 to December 2006 compared to expected new cases of Rb using our algorithm. Results: A total of 134 families with sporadic Rb were enrolled; testing was performed in 570 individuals and 99 patients younger than 4 years old were identified. We observed one new case of Rb. Using our algorithm, the cumulated total a posteriori risk of recurrence was 1.77. Conclusions: This is the first time that linkage analysis has been validated to monitor the risk of recurrence in sporadic Rb. This should be a useful tool in genetic counseling, especially when direct RBI screening for mutations leaves a negative result or is unavailable.

Causal mechanisms underlying host specificity in bat ectoparasites.

In parasites, host specificity may result either from restricted dispersal capacity or from fixed coevolutionary host-parasite adaptations. Knowledge of those proximal mechanisms leading to particular host specificity is fundamental to understand host-parasite interactions and potential coevolution of parasites and hosts. The relative importance of these two mechanisms was quantified through infection and cross-infection experiments using mites and bats as a model. Monospecific pools of parasitic mites (Spinturnix myoti and S. andegavinus) were subjected either to individual bats belonging to their traditional, native bat host species, or to another substitute host species within the same bat genus (Myotis). The two parasite species reacted differently to these treatments. S. myoti exhibited a clear preference for, and had a higher fitness on, its native host, Myotis myotis. In contrast, S. andegavinus showed no host choice, although its fitness was higher on its native host M. daubentoni. The causal mechanisms mediating host specificity can apparently differ within closely related host-parasite systems.

The energetic grooming costs imposed by a parasitic mite (Spinturnix myoti) upon its bat host (Myotis myotis).

Parasites often exert severe negative effects upon their host's fitness. Natural selection has therefore prompted the evolution of anti-parasite mechanisms such as grooming. Grooming is efficient at reducing parasitic loads in both birds and mammals, but the energetic costs it entails have not been properly quantified. We measured both the energetic metabolism and behaviour of greater mouse-eared bats submitted to three different parasite loads (no, 20 and 40 mites) during whole daily cycles. Mites greatly affected their time and energy budgets. They caused increased grooming activity, reduced the overall time devoted to resting and provoked a dramatic shortening of resting bout duration. Correspondingly, the bats' overall metabolism (oxygen consumption) increased drastically with parasite intensity and, during the course of experiments, the bats lost more weight when infested with 40 rather than 20 or no parasites. The short-term energetic constraints induced by anti-parasite grooming are probably associated with long-term detrimental effects such as a decrease in survival and overall reproductive value.

Habitat, morphology and karyotype of the Saharan shrew Crocidura tarfayaensis (Mammalia : Soricidae)

The Saharan shrew Crocidura tarfayaensis Vesmanis and Vesmanis, 1980, has a limited disribution along the Atlantic coast of Sahara, south of Agadir (Morocco) through Western Sahara into Mauritania and is only known from few captures and some owl pellets. Here we report field data from the successful trapping of five specimens of C. tarfayaensis in the Guelmim region. The habitat was characterized by sand dunes along a river, with dense shrubberies of Tamarix sp., the huge grass Erianthus ravennae (Poaceae) and flat bushes of Atriplex glauca var. ifniensis (Chenopodiaceae). Morphological discrimination with C. whitakeri were examined. The chromosomes of C. tarfayaensis revealed a karyotype of 2n = 36, similar to that of the Canary shrew C. canariensis and the Sicilian shrew C. sicula. In conclusion, C. tarfayaensis seems to be a descendant of the presumed continental ancestor of the two island species.

Formule chromosomique de Micropotamogale lamottei (Mammalia, Tenrecidae)

Le caryotype d'un mâle de Micropotamogale lamottei est décrit. La formule chromosomique est de 2N = 38, le nombre fondamental (NF) s'élève à 76. Ce caryotype diverge considérablement de celui des Microgales malgaches, considérés généralement comme les parents les plus proches des Potamogalinae.

Anti-cancer activity of 5-O-alkyl 1,4-imino-1,4-dideoxyribitols.

New derivatives of 1,4-dideoxy-1,4-imino-D-ribitol have been prepared and evaluated for their cytotoxicity on solid and haematological malignancies. 1,4-Dideoxy-5-O-[(9Z)-octadec-9-en-1-yl]-1,4-imino-D-ribitol (13, IC(50) ∼2 μM) and its C(18)-analogues (IC(50) <10 μM) are cytotoxic toward SKBR3 (breast cancer) cells. 13 also inhibits (IC(50) ∼8 μM) growth of JURKAT cells.

The fetal membranes of the otter shrews and a synapomorphy for afrotheria.

The otter shrews of mainland Africa are the closest relatives of the Madagascar tenrecs. We sought for similarities in placentation between the two groups and, in a wider context, with other mammals of the Afrotheria clade. Specimens of the Nimba otter shrew (Micropotamogale lamottei) were obtained from the Ivory Coast and examples of the giant otter shrew (Potamogale velox) from the Hill Collection. The Nimba otter shrew has a central haemophagous organ similar to that in tenrecs. The labyrinth of the Nimba otter shrew, however, is endotheliochorial with syncytial trophoblast enclosing the maternal vessels. On the other hand tenrecs have cellular haemomonochorial placentae and an associated spongy zone, which is not present in the Nimba otter shrew. The placenta of the giant otter shrew is also endotheliochorial. The central region of its placenta is particularly interesting, since the juxtafetal portion is clearly a haemophagous region whereas the labyrinth feeding this region is endotheliochorial. Thus there is considerable variation in placental morphology within Tenrecidae. Importantly, however, both otter shrews have a large allantoic sac divided into four intercommunicating lobes by two pairs of septal folds. A similar arrangement has been described for representatives of each of the remaining five orders within Afrotheria. This is significant because previous anatomical studies have failed to establish a single synapomorphy in support of Afrotheria.

Systematics of snow voles (Chionomys, Arvicolinae) revisited.

To elucidate the evolutionary history of snow voles, genus Chionomys, we studied the phylogeography of Chionomysnivalis across its range and investigated its relationships with two congeneric species, Chionomysgud and Chionomysroberti, using independent molecular markers. Analyses were based on mitochondrial (~940 bp cyt b) and Y-chromosomal (~2020 bp from three introns) genetic variation. Our data provide conclusive evidence for a Caucasian and Middle Eastern origin for the three species and a subsequent westward expansion of C.nivalis. In addition, we discuss the taxonomic status of the genus Chionomys in relation to the genus Microtus.

Risk assessment of recurrence in sporadic retinoblastoma using a molecular-based algorithm.

PURPOSE: Most RB1 mutations are unique and distributed throughout the RB1 gene. Their detection can be time-consuming and the yield especially low in cases of conservatively-treated sporadic unilateral retinoblastoma (Rb) patients. In order to identify patients with true risk of developing Rb, and to reduce the number of unnecessary examinations under anesthesia in all other cases, we developed a universal sensitive, efficient and cost-effective strategy based on intragenic haplotype analysis. METHODS: This algorithm allows the calculation of the a posteriori risk of developing Rb and takes into account (a) RB1 loss of heterozygosity in tumors, (b) preferential paternal origin of new germline mutations, (c) a priori risk derived from empirical data by Vogel, and (d) disease penetrance of 90% in most cases. We report the occurrence of Rb in first degree relatives of patients with sporadic Rb who visited the Jules Gonin Eye Hospital, Lausanne, Switzerland, from January 1994 to December 2006 compared to expected new cases of Rb using our algorithm. RESULTS: A total of 134 families with sporadic Rb were enrolled; testing was performed in 570 individuals and 99 patients younger than 4 years old were identified. We observed one new case of Rb. Using our algorithm, the cumulated total a posteriori risk of recurrence was 1.77. CONCLUSIONS: This is the first time that linkage analysis has been validated to monitor the risk of recurrence in sporadic Rb. This should be a useful tool in genetic counseling, especially when direct RB1 screening for mutations leaves a negative result or is unavailable.

Comparative winter thermoregulation and body temperature in three sympatric Apodemus species (A-alpicola, A-flavicollis, and A-sylvaticus)

When living in sympatry with Apodemus sylvaticus and A. flavicollis, A. alpicola dominates numerically at higher altitudes. A more efficient winter thermal isolation or a higher winter thermogenic capacity procuring a physiological advantage could explain at least part of this domination. We therefore measured body temperature (Tb), oxygen consumption (VO2), wet minimal thermal conductance (C) and non shivering thermogenesis (NST) at different ambient temperatures (Ta) on winter acclimated mice of the three species, and this for the first time in A. alpicola. NST was high and C low in the three species. No significant difference could be noticed either in Tb between 5 and -10 degrees C, in VO2 measurements at a Ta of -10 degrees C or in C. The NST measurements represent, respectively, 135.2% for A. sylvaticus, 142.8% for A. flavicollis and 140.5% for A. alpicola of the expected values, the values for A. sylvaticus being significantly lower than for the other two species. The basal metabolic rates (BMR) represent 169.4% for A. sylvaticus, 161.6% for A. flavicollis and 138.3% for A. alpicola of the expected values. Having removed the effect of body weight, the BMR value was significantly lower in A. alpicola than in A. flavicollis, but no difference could be noticed between A. sylvaticus and the other two species. In conclusion, the three species of mice have very similar acclimated thermoregulatory characteristics, well adapted to cold ambient conditions. One discriminating and advantageous factor could be the lower basal metabolic rate measured in A. alpicola compared to the other two species.