Life history, biomass and production of Coronatella rectangula (Branchiopoda, Anomopoda, Chydoridae) from Minas Gerais

Species of Chydoridae provide the main diversity of the Cladocera. These organisms have been the subject of many studies; some dealing with their role in energy flow in aquatic ecosystems, since they inhabit the littoral region of water bodies which undergo the first impacts from anthropic activities. The aim of this study is to increase knowledge about the life cycle of Coronatella rectangula (Sars, 1861), a species found in several water bodies in the state of Minas Gerais, Brazil. The life cycle was determined by the culture of parthenogenetic females under controlled conditions in the laboratory. Experimental cultures were maintained in growth chambers at a constant temperature of 23.6(±0.5)ºC, through a 12 h light/12 h dark photoperiod. The organisms were fed on a suspension of Pseudokirchneriella subcapitata (Chlorophyceae) (10(5) cells.mL-1), and 0.02 mL of a mixed suspension of yeast and fish ration added per organism in equal proportions (1:1). Fifty parthenogenetic females with eggs were isolated and maintained until they produced neonates. Thirty of these neonates that had less than 24 hours were put in polypropylene bottles of 50 mL and kept in a germination chamber. These organisms were observed daily to obtain the parameters of the life cycle. Biomass and secondary production were also calculated. The embryonic development time of the specimens of C. rectangula was 1.68(±0.13) days and the time to reach primipara, was 2.48(±0.45) days. The mean fecundity of C. rectangula was two eggs/female/brood and the total number of eggs produced by the female during its life cycle was 27.8 eggs. During the whole life cycle, specimens of C. rectangula had a maximum of 14 seedlings, with two instars in the juvenile stage. Total biomass for C. rectangula was 36.66 µgDW.m-3(9.83 for the juvenile stage and 26.82 µgDW.m-3 for adults), and secondary production was 12.10 µgDW.m-3.day-1(8.34 µgDW.m-3.day-1 for egg production and 3.76 µgDW.m-3.day-1 for the juvenile stage).

The life history of Hepatozoon leptodactyli (Lesage, 1908) Pessoa, 1970: a parasite of the common laboratory animal: the frog of the genus Leptodactylus

The main object of the present paper is to furnish a brief account to the knowledgement of Protozoa parasitic in common Brazilian frog of the genus Leptodactylus for general students in Zoology and for investigators that use this frog as a laboratory animal. Hepatozoon leptodactyli (Haemogregarina leptodactyli) was found in two species of frogs - Leptodactylus ocellatus and L. pentadactylus - in which develop schizogony whereas sporogony occurs in the leech Haementeria lutzi as was obtainded in experimental conditions. Intracellular forms have been found in peripheral circulation, chiefly in erythrocytes, but we have found them in leukocytes too. Tissue stages were found in frog, liver, lungs, spleen, gut, brain and heart. The occurence of hemogregarine in the Central Nervous System was recorded by Costa & al,(13) and Ball (2). Some cytochemical methods were employed in attempt to differentiate gametocytes from trophozoites in the peripheral blood and to characterize the cystic membrane as well. The speorogonic cycle was developed in only one specie of leech. A brief description of the parasite is given.

Life history studies of heterophyid Trematodes in the neotropical region: Ascocotyle (Leighia) hadra sp.n

The life cycle of Ascocotyle (Leighia) hadra n.sp. was experimentally reproduced, starting from cercariae from naturally infected Littoridina parchappei, collected from Los Ranchos stream, near Mercedes city, Buenos Aires Province, Argentina. Metacercariae were found encysted in the liver and mesentery of experimentally and naturally infected fishes Cnesterodon decemmaculatus and Jenynsia lineata. Adults were obtained experimentally in chicks and mice. The natural host is unknown. The new species is compared with Ascocotyle (Leighia) mcintoshi Price 1936 as described by Leigh, 1974, differing in behavior and morphology of cercarial, metacercarial and adult stages

Life history of Pygidiopsis crassus n. sp. (Trematoda, Digenea, Heterophyidae) in the neotropical region

The life cycle of Pygidiopsis crassus n. sp. was experimentally reproduced, starting from cercariae from naturally infected Littoridina parchappei collected from Lujan River and different ponds in Buenos Aires Province, Argentina. Metacercariae were found encysted in the body cavity of experimentally and naturally infected fishes Cnesterodon decemmaculatus and naturally infected Jenynsia lineata. Adults were obtained experimentally in chicks and mice. The natural host is unknown. The new species is compared with Pygidiopsis macrostomum Travassos 1928, from Rattus norvegicus and from Noctilio leporinus mastivus, differing in body and egg sizes, in the size relation of oral and ventral sucker and the shape of excretory vesicle.

Life history correlates of adult size in the malaria vector Anopheles darlingi

Adult dry weights of laboratory-reared Anopheles darlingi were highly correlated with wing lengths, which were used to estimate size variation in natural populations of this species. Significant differences in mean wing lengths of females trapped at baits were detected among collections in the same week at one site, but not between three sites in Brazil and Boliva. Relatively higher variability of wing lengths, compared to collections of other Anopheles (Nyssorhynchus), and platykurtic size distributions in large, single-night collections suggested that An. darlingi females caught at baits emerged from heterogenous larval habitats. No relationship was detected between parous state and the body size of wild-caught females. Adult males and females of laboratory-reared An. darlingi did not differ in body size. This absence of sexual size dimorphism is rare among mosquitoes and has not been noted previously in the genus Anopheles.

How life history and demography promote or inhibit the evolution of helping behaviours.

In natural populations, dispersal tends to be limited so that individuals are in local competition with their neighbours. As a consequence, most behaviours tend to have a social component, e.g. they can be selfish, spiteful, cooperative or altruistic as usually considered in social evolutionary theory. How social behaviours translate into fitness costs and benefits depends considerably on life-history features, as well as on local demographic and ecological conditions. Over the last four decades, evolutionists have been able to explore many of the consequences of these factors for the evolution of social behaviours. In this paper, we first recall the main theoretical concepts required to understand social evolution. We then discuss how life history, demography and ecology promote or inhibit the evolution of helping behaviours, but the arguments developed for helping can be extended to essentially any social trait. The analysis suggests that, on a theoretical level, it is possible to contrast three critical benefit-to-cost ratios beyond which costly helping is selected for (three quantitative rules for the evolution of altruism). But comparison between theoretical results and empirical data has always been difficult in the literature, partly because of the perennial question of the scale at which relatedness should be measured under localized dispersal. We then provide three answers to this question.

Life-history traits of Fossaria cubensis (Gastropoda: Lymnaeidae) under experimental exposure to Fasciola hepatica (Trematoda: Digenea)

The effect of exposing the lymnaeid snail Fossaria cubensis to the trematode Fasciola hepatica on the snail population's life-history traits was studied under laboratory conditions. Exposed individuals showed a lower survival rate than control snails, although from week 7 onward a slower decrease of this parameter in relation to the control group was observed. There were higher values of fecundity rate for the controls compared to the exposed group except during weeks 9, 10, 11 and 12, which was the time that followed the period when almost all of the infected snails died. Both the intrinsic and finite rates of natural increase were significantly higher for the control group, but exposed snails still attained a lower mean generation time. Age-specific trade-offs were found, mainly for the weekly increase in size versus the number of eggs per mass, the weekly increase in size versus the number of viable eggs per mass, the number of masses versus the hatching probability and the number of eggs versus the hatching probability. All these negative associations were significant for juveniles of both control and exposed snails and not for adults; however, exposed young individuals exhibited much higher values of the correlation coefficient than control animals.

The effect of isolation on the life-history traits of Pseudosuccinea columella (Pulmonata: Lymnaeidae)

A population of Pseudosuccinea columella was raised under laboratory conditions and its life tables were determined in isolated and paired snails. Isolated snails were significantly larger in shell size than paired snails from five weeks of age onward. Also, statistically significant differences were found for the number of eggs per mass per individual from week 5 to 9, isolated snails exhibiting the highest values. The intrinsic and finite rates of increase were greater in isolated than in paired snails. Either an inhibition of the reproductive output between individuals or the advantage of selfing may be the cause of the differences in this species, acting as a possible mechanism that increase the fitness of isolated snails.

Breastfeeding - part of everyday life

This poster highlights how discreet breastfeeding can be part of everyday life.

Life history analysis of integrative and conjugative element activation in growing microcolonies of Pseudomonas.

Integrative and conjugative elements (ICE) are in some ways parasitic mobile DNA that propagate vertically through replication with the bacterial host chromosome but at low frequencies can excise and invade new recipient cells through conjugation and reintegration (horizontal propagation). The factors that contribute to successful horizontal propagation are not very well understood. Here, we study the influence of host cell life history on the initiation of transfer of a model ICE named ICEclc in bacteria of the genus Pseudomonas. We use time-lapse microscopy of growing and stationary-phase microcolonies of ICEclc bearing cells in combination with physiological staining and gene reporter analysis in stationary-phase suspended cells. We provide evidence that cell age and cell lineage are unlikely to play a role in the decision to initiate the ICEclc transfer program. In contrast, cells activating ICEclc show more often increased levels of reactive oxygen species and membrane damage than nonactivating cells, suggesting that some form of biochemical damage may make cells more prone to ICEclc induction. Finally, we find that ICEclc active cells appear spatially at random in a microcolony, which may have been a selective advantage for maximizing ICEclc horizontal transmission to new recipient species.

Evolution of life history traits in a natural population of the shrew Crocidura russula

Abstract Life history traits encompass all the decisions concerning fitness an individual is faced with during his life. The study of these traits is crucial to understand the factors shaping the biology of living organisms. Up until now, most of the information on the evolution of life history traits comes from laboratory studies. While these studies are interesting to test the effect of specific parameters, their conclusions are difficult to extrapolate to natural populations. Investigating the evolution of life history traits in natural populations is of great interest. This may be tricky because it requires information on reproduction, survival and morphology of individuals. Mark-recapture methods allow most of this information to be obtained. However, when direct observations of a species are not possible due to its ecology, indirect methods must be used to infer lifetime reproductive success. In this case, molecular markers are particularly helpful in assessing the genetic relationships between individuals and allow the construction of a pedigree. This thesis focuses on a natural population of a small insectivorous mammal, the greater white-toothed shrew, Crocidura russula. Because of its hidden lifestyle, the two complementary techniques mentioned above were combined to gather information on this population. The data were used to explore diverse aspects of evolutionary biology. We demonstrated that the high genetic variance displayed by the species was not maintained by its mating system because this shrew was less monogamous than previously thought. The large genetic diversity was most likely promoted by gene flow from the neighborhood. Dispersal was thus a central topic in this thesis. We showed that dispersal was not driven by inbreeding avoidance. In addition, we did not find any inbreeding depression in the population. Dispersal was promoted by a high number of vacant territories in the population for both sexes, meaning that territory acquisition played an important role in driving dispersal. Moreover, dispersal propensity was shown to have a genetic basis and, once achieved, to have no effect on individual fitness. Body mass was found to be a life history trait strongly influenced by sexual and viability selection in both sexes. Larger individuals had higher access to reproduction through territory acquisition and defense than lighter ones. By contrast, intermediate size individuals were favored by viability selection presumably because of ecological constraints and metabolic costs. Finally, we demonstrated that the majority of the life history traits in our shrew population has the potential to evolve because they maintained substantial amounts of additive genetic variance. Nonetheless, life history traits had no significant heritability due to their high level of nonadditive or environmental variance. Résumé Les traits d'histoire de vie comprennent toutes les décisions auxquelles un individu est confronté au cours de sa vie et qui concernent sa valeur adaptative. L'étude de ces traits est cruciale pour comprendre les facteurs qui façonnent la biologie des êtres vivants. Jusqu'à ce jour, la majorité des informations sur l'évolution des traits d'histoire de vie provient d'études réalisées en laboratoire. Alors que ces études sont intéressantes pour tester l'effet de paramètres spécifiques, leurs conclusions sont difficilement extrapolables aux populations naturelles. Il est particulièrement intéressant d'étudier l'évolution des traits d'histoire de vie dans des populations naturelles. Toutefois, ces études peuvent se révéler difficiles parce qu'elles requièrent des informations sur la reproduction, la survie et la morphologie des individus. Des méthodes de marquage-recapture permettent d'obtenir ces informations. Cependant, lorsque l'écologie de l'espèce rend les obervations directes impossibles, des méthodes indirectes doivent être utilisées pour obtenir le succès reproducteur des individus. Dans ce cas, les marqueurs moléculaires sont particulièrement utiles pour évaluer les relations génétiques entre individus et permettre la construction d'un pedigree. Cette thèse porte sur une population naturelle d'un petit mammifère insectivore, la musaraigne musette, Crocidura russula. Parce que cette espèce présente un mode de vie souterrain, les deux techniques complémentaires mentionnées ci-dessus ont été combinées pour acquérir les informations nécessaires. Les données ont été utilisées pour explorer divers aspects de biologie evolutive. Nous avons montré que la grande quantité de variance génétique trouvée chez cette espèce n'est pas maintenue par son système d'appariement. Celle-ci s'est en effet avérée être moins monogame que ce qui était admis jusqu'ici. Sa grande diversité génétique est plutôt entretenue par le flux de gènes provenant du voisinage. La dispersion a donc été un sujet phare dans cette thèse. Nous avons montré qu'elle n'est pas provoquée par un évitement de la consanguinité et nous n'avons pas trouvé de dépression de consanguité dans notre population. L'acquisition d'un territoire joue par contre un rôle important dans la dispersion. En outre, la dispersion possède une base génétique chez cette espèce. De plus, une fois qu'ils ont dispersé, les individus n'ont pas une valeur adaptative differente d'individus philopatriques. Le poids s'est avéré être un trait d'histoire de vie fortement influencé par la sélection sexuelle et de viabilité chez les deux sexes. Les gros individus ont accès à la reproduction parce qu'ils acquièrent et défendent un territoire plus facilement que les plus légers. Au contraire, les individus de taille intermédiaire sont favorisés par la sélection de viabilité, certainement à cause de contraintes écologiques et de coûts métaboliques. Finalement, nous avons montré que la majorité des traits d'histoire de vie dans notre population a le potentiel d'évoluer parce qu'elle maintient des quantités considérables de variance génétique additive. Néanmoins, l'héritabilité de ces traits d'histoire de vie n'est pas significative à cause de la grande quantité de variance non-additive ou environmentale associée à ces traits.

The life history of Pygidiopsis macrostomum Travassos, 1928 (Digenea: Heterophyidae)

The life history of the trematode Pygidiopsis macrostomum Travassos, 1928 is described for the first time. Rediae and cercariae were obtained from naturally infected snails Heleobia australis (d´Orbigny), a new first intermediate host. Metacercariae were found encysted in the mesenteries of three naturally infected guppies, Phalloptychus januarius (Hensel), Jenynsia multidentata (Jenyns) (new host records) and Poecilia vivipara Bloch and Schneider. Experimental infections were successfully completed in the intermediate hosts H. australis and Poe. vivipara reared in the laboratory and hamsters Mesocricetus auratus Waterhouse were utilised as a definitive host.

Genetic and environmental effects on early life-history traits in salmonids

Les changements environnementaux, tels la température ou les maladies infectieuses, peuvent influencer l'évolution en induisant de la sélection, mais ceci à la seule condition qu'il y ait assez de diversité génétique pour les traits en question ou pour l'expression plastique de ces traits. Au cours cette thèse, nous avons étudié l'effet de potentielles pressions environnementales sur différents phénotypes de trois représentants des sous familles des salmonidés: l'ombre commun (Thymallus thymallus; Thymallinae), la truite de rivière {Salmo trutta; Salmoninae) et le corégone Coregonus palaea (Coregoninae). Les salmonidés se prêtent particulièrement bien à ce type d'expériences car étant hautement sensibles aux conditions environnementales, ils montrent une large variabilité dans leurs traits morphologiques, comportementaux ainsi que d'histoire de vie, tout en bénéficiant d'un large intérêt général. Nous avons testé si le sexe de l'ombre commun pouvait être modifié par la température, ce qui pourrait ainsi expliquer un changement abrupte de sex ratio observé dans l'une des plus grandes populations de Suisse. Nous n'avons trouvé aucun indice permettant de conclure que la température puisse induire ce changement chez l'ombre commun ou chez la truite de rivière. De plus nous avons étudié la plasticité de développement ainsi que d'éclosion, et avons observé des différences entre familles ainsi qu'entre populations. Alors que ces différences comportementales entre populations suggéraient une adaptation aux conditions environnementales locales, cette prédiction n'a pas été confirmée par une expérience de transplantation réciproque d'embryons entre cinq rivières de la même région. Cette étude a montré que les embryons ne survivaient pas mieux dans leur rivière d'origine, indiquant donc une absence d'adaptation locale. Nous avons aussi montré que la mortalité embryonnaire était influencée autant par des "bons gènes" que par des "gènes compatibles", que la qualité des mâles pouvait être signalée par leur coloration, et que le fait d'élever des poissons dans une pisciculture pouvait aboutir a des relations contre-intuitives entre la coloration des mâles et la qualité de leur jeunes. Nos résultats contribuent ainsi à une meilleure compréhension de l'effet de diverses pressions environnementales sur la morphologie, le comportement ou les traits d'histoire de vie chez les salmonidés. - Environmental changes, such as changes in temperatures or infection levels, can induce selection and drive evolution if there is sufficient genetic variation for the traits or the plasticity in trait expression. In this thesis, we investigated the influence of potential environmental stressors on various phenotypes in representatives of the three salmonid subfamilies: the European grayling (Thymallus thymallus; Thymallinae), the brown trout (,Salmo trutta; Salmoninae), and the whitefish Coregonus palaea (Coregoninae). Salmonids are ideal study species, as they seem sensitive to changing environmental conditions, show considerable variability in morphological, behavioral, and life history traits, and are of broad public interest. We investigated whether temperature-induced sex reversal could explain the sex-ratio distortion found in one of Switzerland's largest grayling populations. We found no evidence of temperature-induced sex reversal in either graylings or brown trout. We also examined plasticity in embryo development and the timing of hatching. We found variation at the level of family and population. Although behavioral differences between populations suggested adaptation to local environmental conditions, no indications of local adaptation could be found in reciprocal transplant experiments carried out over five rivers in the same region. We also demonstrate that embryo development and viability is influenced by 'good genes' and 'compatible genes', that the genetic quality of sires can be signaled by their grey coloration, and that raising larvae in a hatchery environment can produce counter-intuitive relationships between male phenotypes and offspring viability. Our results contribute to the understanding of how changing environmental conditions affect the phenotypes and the heritability of early life-history traits in salmonids.