Why protogynous hermaphrodite males are relatively larger than females? Testing growth hypotheses in Mediterranean rainbow wrasse <Emphasis Type="Italic">Coris julis</Emphasis> (Linnaeus, 1758)

Several growth hypotheses have been tested to investigate why males of the sequential hermaphrodite, Mediterranean rainbow wrasse, Coris julis (Linnaeus, 1758), are relatively larger than females of the same age. Individual growth trajectories were estimated to test these hypotheses. A good linear relationship between otolith size and body size was observed (r ²  = 0.71, n = 609), thus, past somatic growth of any specific fish can be inferred from the longitudinal data described by the width of annual increments in the otolith. These data were successfully analyzed by a non-linear mixed-effect model (von Bertalanffy growth model) using a Bayesian approach. The results obtained suggest that Mediterranean rainbow wrasse secondary males are relatively larger than females because 1) fish that change sex are already the larger individuals in their age group (specifically those with higher growth rate, k _{secondary males}  = 0.199 and k _females  = 0.161) and 2) they experience a growth spurt after sex change. The differences in growth observed in this species and in other protogynous hermaphrodites could be related to differences in social organization, which, in turn, are related to differences in the sex change mechanisms.     

Nutrient deprivation improves field performance of woody seedlings in a degraded semi-arid shrubland

The performance of planted seedlings in drylands is affected by seedling morphological and physiological traits. Recent studies support a positive relationship between seedling size and field performance. However, exceptions to this paradigm suggest that this relationship may be dependent on species and degree of stress. To test the hypothesis that small seedlings would be favored under harsh semi-arid conditions over large seedlings, we produced seedlings of five Mediterranean woody species (Pistacia lentiscus, Quercus coccifera, Rhamnus lycioides, Rhamnus alaternus and Tetraclinis articulata) under contrasted fertilization regimes, and evaluated their performance after planting in a semi-arid area. Seedlings were cultivated under full sunlight and received either slow release fertilizer or bi-weekly applications of complete nutrient solution, diluted fertirrigation, or nutrient solutions containing no nitrogen or no phosphorus. Fertilization had a strong effect on nutrient status, above and belowground biomass accumulation, and biomass allocation patterns. Root: shoot ratio was higher in nitrogen- and phosphorus-deficient seedlings than in seedlings receiving complete nutrient solution or slow-release fertilizer. One year after planting, seedling survival was negatively correlated with plant size for all species. The effect of nutritional regime on field survival decreased over the 2 following years. Our results show that nutrient-deprived seedlings are more likely to establish under semi-arid conditions than well-fertilized seedlings, suggesting that morphological and functional characteristics associated with nutrient deficiency may outbalance the scarcity of nutrient reserves in seedling tissues.     

Facts and uncertainties about the genetic population structure of Atlantic bluefin tuna (<Emphasis Type="Italic">Thunnus thynnus</Emphasis>) in the Mediterranean. Implications for fishery management

The Atlantic bluefin tuna (Thunnus thynnus) is an extraordinary fish that has amazed humanity since ancient times. However, the continuous overexploitation of this fishery, particularly in the Mediterranean Sea, could result in a total collapse of this resource. Currently, this species is managed as two stocks: Western Atlantic and Mediterranean-Eastern Atlantic, with a recognized genetic differentiation between them. On the other hand, the population structure within the Mediterranean Sea is still unclear. The biological data supports the idea of two separate populations in the eastern and western Mediterranean basins. However, nuclear microsatellite and mitochondrial DNA (mtDNA) analyses of two samples representative of these two basins result in a lack of heterogeneity. A comparison of these results with previously published studies reveals some discrepancies. We have compared 59 genetic differentiation tests that include samples within the Mediterranean. Of these, about 60% gave significant differentiation while the remaining 40% were non-significant. But, when only nuclear-based loci were considered, genetic differentiation was detected in up to 73% of the cases with an average significant F _ST of only 0.018, whereas the average significant F _ST of the mtDNA-based studies was significantly higher (0.029). However, in some cases, it is difficult to reconcile the biology of the species with the results suggesting genetic differentiation. In conclusion, although it is not yet possible to reach a definitive conclusion about the population structure, but considering all biological and genetic data, we suggest an independent management approach for each basin to avoid the impact of a type II error that could lead to the possible loss of the regional subpopulations.     

The long summer: pre-wintering temperatures affect metabolic expenditure and winter survival in a solitary bee

The impact of climate change on insect populations depends on specific life cycle traits and physiological adaptations. The solitary bee Osmia lignaria winters as a pre-emergent adult, and requires a period of cold temperature for winter diapause completion. It is a univoltine species, and diapause induction does not depend on photoperiod. To understand the potential effects of longer summers on O. lignaria populations, we exposed individuals to three treatments simulating early, mid and late winter arrivals, and measured respiration rates, metabolic expenditure, weight loss, fat body depletion, lipid levels and winter mortality. The early-winter treatment disrupted diapause development, but had no apparent negative effects on fitness. In contrast, late-winter bees had a greater energetic expenditure (1.5-fold), weight (1.4-fold) and lipid (2-fold) loss, greater fat body depletion, and a 19% increase in mortality compared to mid-winter bees. We also monitored adult eclosion and arrival of winter temperatures under natural conditions in four years. We found a positive correlation between mean degree-day accumulation during pre-wintering (a measure of asynchrony between adult eclosion and winter arrival) and yearly winter mortality. Individually, bees experiencing greater degree-day accumulations exhibited reduced post-winter longevity. Timing of adult eclosion in O. lignaria is dependent on the duration of the prepupal period, which occurs in mid-summer, is also diapause-mediated, and is longer in populations from southerly latitudes. In a global warming scenario, we expect long summer diapause phenotypes to replace short summer diapause phenotypes, effectively maintaining short pre-wintering periods in spite of delayed winter arrivals.     

Expression,localization, and regulation of the neuregulin receptor ErbB3 in mouse heart

Neuregulins (NRG) belong to the EGF family of growth factors, which are ligands of the ErbB receptors. Their expression in the adult heart is essential, especially when the heart is submitted to cardiotoxic stress such as that produced by anthracyclines. It is considered that ErbB4 is the only NRG receptor expressed by the adult heart. Upon binding, ErbB4 may dimerize with ErbB2 to generate signals inside cells. However, here we show the presence of ErbB3 in the mouse heart from birth to adulthood by Western blotting and real‐time RT‐PCR. The expression level of ErbB3 mRNA was lower than that of ErbB2 or ErbB4, but was more stable throughout postnatal development. In isolated heart myocytes, ErbB3 localized to the Z‐lines similarly to ErbB1. Perfusion of isolated hearts with NRG‐1β induced phosphorylation of ErbB3, as well as ErbB2 and ErbB4. In adult mice, both ErbB2 and ErbB3, but not ErbB1 or ErbB4, were rapidly down‐regulated upon the induction of heart hypertrophy. In conclusion, our results demonstrate that ErbB3, in addition to ErbB4, is a receptor for neuregulin‐1β in the adult mouse heart. J. Cell. Physiol. 226: 450–455, 2011. © 2010 Wiley‐Liss, Inc.     

Molecular and functional characterization of mouse S5D-SRCRB: a new group B member of the scavenger receptor cysteine-rich superfamily

The scavenger receptor cysteine-rich superfamily (SRCR-SF) members are transmembrane and/or secreted receptors exhibiting one or several repeats of a cysteine-rich protein module of ～100 aa, named scavenger receptor cysteine-rich (SRCR). Two types of SRCR domains (A or B) have been reported, which differ in the number of coding exons and intradomain cysteines. Although no unifying function has been reported for SRCR-SF members, recognition of pathogen-associated molecular patterns (PAMPs) was recently shown for some of them. In this article, we report the structural and functional characterization of mouse S5D-SRCRB, a new group B member of the SRCR-SF. The s5d-srcrb gene maps at mouse chromosome 7 and encompasses 14 exons extending over 15 kb. The longest cDNA sequence found is 4286 bp in length and encodes a mature protein of 1371 aa, with a predicted M(r) of 144.6 kDa. Using an episomal mammalian-expression system, a glycosylated soluble recombinant form >200 kDa was obtained and used as immunogen for the generation of specific rat mAbs. Subsequent immunohistochemical and real-time PCR analysis showed significant S5D-SRCRB expression in murine genitourinary and digestive tracts. S5D-SRCRB was shown to bind endogenous extracellular matrix proteins (laminin and galectin-1), as well as PAMPs present on Gram-positive and Gram-negative bacteria and fungi. PAMP binding by S5D-SRCRB induced microbial aggregation and subsequent inhibition of PAMP-induced cytokine release. These abilities suggest that S5D-SRCRB might play a role in the innate defense and homeostasis of certain specialized epithelial surfaces.     

Carcass transport decisions in Homo antecessor subsistence strategies

Pleistocene foragers used several prey acquisition and processing strategies. These strategies and their associated decisions are elucidated by taphonomic studies that cover animal transport, modifications by different agents and archaeological remains. Interpretative models of archaeological sites are by necessity based on natural and experimental observations. Ethno-archaeological data shows that several factors influenced decisions about carcass transport from the kill site to the home site. These factors often have little archaeological visibility. Díez et al. (1999) has previously interpreted the general characteristics of the macro-mammal remains from Gran Dolina Level TD6-2 (Sierra de Atapuerca, Burgos, Spain) as the result of anthropic accumulation, in which the anatomical profiles appeared to be the result of selective transport based on the animals’ weight. Recent taphonomic analysis has shown that carcasses with different weights may be subject to similar transport strategies, suggesting that other factors influenced these choices. The hominins that occupied TD6-2 (the TD6-2 hominin group), at least sometimes, transported large carcasses to the cave in their entirety, implying participation by groups of individuals in hunting parties. These individuals delayed their consumption of large amounts of food, instead moving it to Gran Dolina, where it was shared with other group members. These decisions are evidence of social cooperation and food sharing amongst early European hominins.     

Colonization capacity and serum bactericidal activity of Haemophilus parasuis thy mutants.

The bacterial thyA gene encodes the enzyme thymidylate synthase, which is essential for dTMP synthesis and, consequently, for DNA replication. In this work, a Haemophilus parasuis thyA mutant was constructed in order to analyze its colonization characteristics and its capacity to generate serum bactericidal activity in infected guinea pigs. The data showed that colonization by the H. parasuis thyA mutant was much less than that of the wild-type strain. Nevertheless, the mutant generated a strong immunogenic response in the host, as detected by measuring serum bactericidal activity.     

Presence of opportunistic oil-degrading microorganisms operating at the initial steps of oil extraction and handling.

Hydrocarbon-degrading microorganisms from natural environments have been isolated and identified using culture-dependent or molecular techniques. However, there has been little research into the occurrence of microorganisms incorporated into crude oil in the initial steps of extraction and handling, which can reduce the quality of stored petroleum. In the present study, a packed-column reactor filled with autoclaved perlite soaked with crude oil was subjected to a continuous flow of sterile medium in order to determine the presence of potential hydrocarbon degraders. Microorganisms developed on the surface of the perlite within a period of 73 days. DNA was extracted from the biofilm and then PCR-amplified using 16S rRNA bacterial and archaeal primers and 18S rRNA eukaryotic primers. No amplification was obtained using archaeal primers. However, denaturing gradient gel electrophoresis (DGGE) revealed the presence of unique bands indicating bacterial and eukaryotic amplification. Excision of these bands, sequencing, and subsequent BLAST search showed that they corresponded to Bacillus sp. and Aspergillus versicolor. The fungus was later isolated from intact perlite in agar plates. A bacterial clone library was used to confirm the presence in the biofilm of a unique hydrocarbon-degrading bacterium closely related to Bacillus sp. Analysis of the petroleum components by gas chromatography showed that there n-alkanes, aromatic hydrocarbons, and carbazoles were degraded.     

Build-up mechanisms determining the topology of mutualistic networks

The frequency distribution of the number of interactions per species (i.e., degree distribution) within plant-animal mutualistic assemblages often decays as a power-law with an exponential truncation. Such a truncation suggests that there are ecological factors limiting the frequency of supergeneralist species. However, it is not clear whether these patterns can emerge from intrinsic features of the interacting assemblages, such as differences between plant and animal species richness (richness ratio). Here, we show that high richness ratios often characterize plant-animal mutualisms. Then, we demonstrate that exponential truncations are expected in bipartite networks generated by a simple model that incorporates build-up mechanisms that lead to a high richness ratio. Our results provide a simple interpretation for the truncations commonly observed in the degree distributions of mutualistic networks that complements previous ones based on biological effects.