Real-time PCR detection and quantification of fish probiotic Phaeobacter strain 27-4 and fish pathogenic Vibrio in microalgae, rotifer, Artemia and first feeding turbot (Psetta maxima) larvae

Aims:  To develop a SYBR Green quantitative real-time PCR protocol enabling detection and quantification of a fish probiotic and two turbot pathogenic Vibrio spp. in microcosms.
Methods and Results:  Phaeobacter 27-4, Vibrio anguillarum 90-11-287 and Vibrio splendidus DMC-1 were quantified as pure and mixed cultures and in presence of microalgae ( Isochrysis galbana ), rotifers ( Brachionus plicatilis ), Artemia nauplii or turbot ( Psetta maxima ) larvae by real-time PCR based on primers directed at genetic loci coding for antagonistic and virulence-related functions respectively. The optimized protocol was used to study bioencapsulation and maintenance of the probiont and pathogens in rotifers and for the detection and quantification of Phaeobacter and V. anguillarum in turbot larvae fed rotifers loaded with the different bacteria in a challenge trial.
Conclusions:  Our real-time PCR protocol is reproducible and specific. The method requires separate standard curve for each host organism and can be used to detect and quantify probiotic Phaeobacter and pathogenic Vibrio bioencapsulated in rotifers and in turbot larvae.
Significance and Impact of the Study:  Our method allows monitoring and quantification of a turbot larvae probiotic bacteria and turbot pathogenic vibrios in in vivo trials and will be useful tools for detecting the bacteria in industrial rearing units.     

Consequences of variable larval dispersal pathways and resulting phenotypic mixtures to the dynamics of marine metapopulations

Larval dispersal can connect distant subpopulations, with important implications for marine population dynamics and persistence, biodiversity conservation and fisheries management. However, different dispersal pathways may affect the final phenotypes, and thus the performance and fitness of individuals that settle into subpopulations. Using otolith microchemical signatures that are indicative of ‘dispersive’ larvae (oceanic signatures) and ‘non-dispersive’ larvae (coastal signatures), we explore the population-level consequences of dispersal-induced variability in phenotypic mixtures for the common triplefin (a small reef fish). We evaluate lipid concentration and otolith microstructure and find that ‘non-dispersive’ larvae (i) have greater and less variable lipid reserves at settlement (and this variability attenuates at a slower rate), (ii) grow faster after settlement, and (iii) experience similar carry-over benefits of lipid reserves on post-settlement growth relative to ‘dispersive’ larvae. We then explore the consequences of phenotypic mixtures in a metapopulation model with two identical subpopulations replenished by variable contributions of ‘dispersive’ and ‘non-dispersive’ larvae and find that the resulting phenotypic mixtures can have profound effects on the size of the metapopulation. We show that, depending upon the patterns of connectivity, phenotypic mixtures can lead to larger metapopulations, suggesting dispersal-induced demographic heterogeneity may facilitate metapopulation persistence.     

American pika in a low‐elevation lava landscape: expanding the known distribution of a temperature‐sensitive species

In 2010, the American pika (Ochotona princeps fenisex) was denied federal protection based on limited evidence of persistence in low‐elevation environments. Studies in nonalpine areas have been limited to relatively few environments, and it is unclear whether patterns observed elsewhere (e.g., Bodie, CA) represent other nonalpine habitats. This study was designed to establish pika presence in a new location, determine distribution within the surveyed area, and evaluate influences of elevation, vegetation, lava complexity, and distance to habitat edge on pika site occupancy. In 2011 and 2012, we conducted surveys for American pika on four distinct subalpine lava flows of Newberry National Volcanic Monument, Oregon, USA. Field surveys were conducted at predetermined locations within lava flows via silent observation and active searching for pika sign. Site habitat characteristics were included as predictors of occupancy in multinomial regression models. Above and belowground temperatures were recorded at a subsample of pika detection sites. Pika were detected in 26% (2011) and 19% (2012) of survey plots. Seventy‐four pika were detected outside survey plot boundaries. Lava complexity was the strongest predictor of pika occurrence, where pika were up to seven times more likely to occur in the most complicated lava formations. Pika were two times more likely to occur with increasing elevation, although they were found at all elevations in the study area. This study expands the known distribution of the species and provides additional evidence for persistence in nonalpine habitats. Results partially support the predictive occupancy model developed for pika at Craters of the Moon National Monument, another lava environment. Characteristics of the lava environment clearly influence pika site occupancy, but habitat variables reported as important in other studies were inconclusive here. Further work is needed to gain a better understanding of the species’ current distribution and ability to persist under future climate conditions.     

Oviposition,larval preference,and larval performance in two polyphagous species: does the larva know best?

It is expected that females preferentially oviposit on plant hosts that allow for optimal larval performance. However, this expectation contradicts empirical evidence where adults do not always choose the best host for their descendants. Recent evidence suggests that females’ host selection depends on the number of potential hosts. Females from oligophagous species seem to be able to choose an appropriate host in terms of larval performance, whereas in polyphagous species, adult oviposition preference is not related with larval performance. This suggests that larvae in polyphagous species could be taking a more active role in host selection than their mothers. Here, we evaluated the oviposition preference and the larval preference and performance of two polyphagous species of economic importance, Copitarsia decolora (Guenée) (Lepidoptera: Noctuidae: Cuculliinae) and Peridroma saucia (Hübner) (Lepidoptera: Noctuidae: Noctuinae), on eight species of cultivated plants. In laboratory and greenhouse choice assays, we tested adult preference for oviposition and larval preference at 1 and 24 h. Larval performance was measured in terms of survival to adulthood, length of larval period, and pupal weight. We found that both adult females and larvae actively choose their hosts and that the larval preference toward the hosts is related to the females’ preference in both herbivore species. However, the females and larvae did not preferentially select the host with the best larval performance, indicating that larval performance is not related to female or larval preference and that other selective pressures are influencing the choice of the host plant in these two species.     

Exploitation of auxotrophies and metabolic defects in Toxoplasma as therapeutic approaches

Like any obligate intracellular pathogen, the parasite Toxoplasma gondii has lost its capacity for living independently of another organism. Toxoplasma lacks many genes that encode for entire metabolic pathways and has, in return, expanded genes that promote nutrient scavenging to meet its basic metabolic requirements. Although sequestrated in a parasitophorous vacuole and thus insulated from the nutrient-rich host cytosol and organelles by a membrane, T. gondii has evolved efficient strategies to acquire essential metabolites from mammalian cells. This review explores the natural auxotrophies and nutrient scavenging activities of the parasite, emphasising unique transport systems and salvage pathways. We describe the mechanisms deployed by Toxoplasma to modify its parasitophorous vacuole to gain access to host cytosolic molecules and to hijack host organelles to retrieve their nutrient content. From a therapeutic perspective, we survey the different possibilities to starve T. gondii by nutrient depletion or disruption of salvage pathways.     

Reproductive cycle of the coral-excavating sponge Thoosa mismalolli (Clionaidae) from Mexican Pacific coral reefs

Abstract. Individuals of the recently described demosponge Thoosa mismalolli are common on Mexican Pacific coral reefs, excavating burrows in living corals and in other calcareous substrata. To better understand the propagative abilities of this sponge, we conducted a histological study over an 18-month period (May 2007–November 2008) to identify sexual and asexual reproductive structures. Members of the species are viviparous and hermaphroditic, with various developmental stages of oocytes, spermatic cysts, and embryos co-occurring in the mesohyl for most of the year. This nearly continuous reproductive activity intensified during the warm season. Fertilization was internal, and embryos developed inside the parental sponge to produce an unciliated hoplitomella larva, characterized by a peculiar siliceous skeleton. In addition to the sexually generated larvae, adults of T. mismalolli formed gemmules for asexual reproduction. Gemmules occurred within the mesohyl during all months of the year, but were most abundant in the coldest months. This combination of sexual and asexual processes enables individuals of T. mismalolli to reproduce almost continuously. This strategy may facilitate both long-term persistence within reefs and effective dispersal between distant reefs.     

Divergence genetics analysis reveals historical population genetic processes leading to contrasting phylogeographic patterns in co-distributed species

Coalescent samplers are computational time machines for inferring the historical demographic genetic processes that have given rise to observable patterns of spatial genetic variation among contemporary populations. We have used traditional characterizations of population structure and coalescent‐based inferences about demographic processes to reconstruct the population histories of two co‐distributed marine species, the frilled dog whelk, Nucella lamellosa, and the bat star, Patiria miniata. Analyses of population structure were consistent with previous work in both species except that additional samples of N. lamellosa showed a larger regional genetic break on Vancouver Island (VI) rather than between the southern Alexander Archipelago as in P. miniata. Our understanding of the causes, rather than just the patterns, of spatial genetic variation was dramatically improved by coalescent analyses that emphasized variation in population divergence times. Overall, gene flow was greater in bat stars (planktonic development) than snails (benthic development) but spatially homogeneous within species. In both species, these large phylogeographic breaks corresponded to relatively ancient divergence times between populations rather than regionally restricted gene flow. Although only N. lamellosa shows a large break on VI, population separation times on VI are congruent between species, suggesting a similar response to late Pleistocene ice sheet expansion. The absence of a phylogeographic break in P. miniata on VI can be attributed to greater gene flow and larger effective population size in this species. Such insights put the relative significance of gene flow into a more comprehensive historical biogeographic context and have important implications for conservation and landscape genetic studies that emphasize the role of contemporary gene flow and connectivity in shaping patterns of population differentiation.     

Hidden diversity and endemism on seamounts: focus on poorly dispersive neogastropods

The seamounts chain offers a set of fragmented habitats in which species with poor dispersive ability may undergo divergence in allopatry. Such a scenario may explain the endemism often described on seamounts. In gastropods, it is possible to infer the mode of development of a species from the morphology of its larval shell. Accordingly, we examine the population genetics of several caenogastropods from the Norfolk and Lord Howe seamounts (south‐west Pacific) with contrasting modes of larval development. A prerequisite to our study was to clarify the taxonomic framework. The species delimitation was ruled using an integrative approach, based on both morphological and molecular evidence. Molecular data indicate an unexpected taxonomic diversity within the existing species names. Both the clarification of the taxonomic framework and the importance of the sampling effort allow us to confidently detect cryptic diversity and micro‐endemism. These results are discussed in relation to the dispersive capacities of the organisms. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100 , 420–438.     

Diptera of forensic importance in the Iberian Peninsula: larval identification key

A revision of the species and families of sarcosaprophagous flies (Diptera: Calliphoridae, Sarcophagidae, Muscidae, Fanniidae, Drosophilidae, Phoridae, Piophilidae and Stratiomyidae) suitable for forensic purposes in the Iberian Peninsula is presented. Morphological characteristics that allow the accurate identification of third instars of the species present in the Iberian Peninsula are described and presented in the form of a diagnostic key. For larval Calliphoridae, characteristics such as the spines of the body segments were useful for the genus Calliphora whereas features of the anal segment and the cephalopharyngeal skeleton were useful for larvae of Lucilia. Identification of three Chrysominae species present in the Iberian Peninsula is included. For larval Sarcophagidae, characters such as the arrangement and shape of spiracular openings, structures of the anal segment and the cephalopharyngeal skeleton were used for the first time. A new record of Sarcophaga cultellata Pandellé, from a human corpse, is also included as well as recent incursions into the European cadaveric entomofauna such as Synthesiomyia nudiseta (van der Wulp) and Hermetia illucens (Linnaeus). This work provides useful new information that could be applied to forensic investigations in the Iberian Peninsula and in southern Europe.     

Seasonal adaptations of different geographical populations of the sunflower moth, Homoeosoma electellum

A photothermogram constructed for a central Missouri population (ca. 39°N latitude) of the sunflower moth, Homoeosoma electellum (Hulst) predicted that this population has a seasonal life cycle of 2 complete and a partial third generation per year, and that daylengths of less than 13 h 30 min light/day and mean temperatures of less than 20°C induce the mature larval diapause. A test of the predicted life cycle revealed that larvae entered diapause when they were exposed from their first instar onwards to natural conditions in central Missouri beginning September 15, 1982. Sunflower moths obtained from northwest Texas (ca. 35°N latitude) and northeast South Dakota (ca. 45°N latitude) displayed shorter critical photoperiods for diapause induction at 20°C (12 h 30 min light/day and 12 h 15 min light/day, respectively) than did those from Missouri. The population of the sunflower moth obtained from South Dakota does not, therefore, appear to be adapted to local conditions, and moths might disperse from lower latitudes to establish transiet populations each year.