Mating behavior in the black hamlet — gamete trading or egg trading?

Synopsis The black hamlet (Hypoplectrus nigricans, Serranidae) is a simultaneous hermaphrodite, like many other serranines. It has external fertilization and planktonic eggs and engages in a kind of reciprocal spawning consisting of three components: (1) The clutch is divided into sequentially spawned parcels. (2) Partners regularly alternate release of parcels in a spawning bout. (3) Courtship is associated with the female spawning role. Two hypotheses have been proposed to account for this pattern. The egg trading hypothesis states that the pattern results from competition for fertilizations and assumes that reproductive success (RS) as a male is limited by access to eggs and that female RS is not limited by access to sperm. The gamete trading hypothesis states that the pattern results from eggs being at substantial risk of not being fertilized — i.e. female RS is limited by access to sperm. An analysis was performed of data from the black hamlet and three other serranines to determine whether significant sperm limitation occurs. The evidence fails to support the hypothesis that access to sperm limits female RS. Unspawned eggs were not found in fish collected outside the spawning period, but fish without eggs always had milt (sperm). The percentage of eggs fertilized did not decrease over the course of a spawning bout. There was also a slight positive correlation between the number of eggs released in a spawning and the percentage that were fertilized, and serranines that divide the clutch into parcels do not tend to have higher fecundities than those that do not. The gamete trading hypothesis can therefore be rejected for H. nigricans.     

Do well-connected landscapes promote road-related mortality?

Cost surface (CS) models have emerged as a useful tool to examine the interactions between landscapes patterns and wildlife at large-scale extents. This approach is particularly relevant to guide conservation planning for species that show vulnerability to road networks in human-dominated landscapes. In this study, we measured the functional connectivity of the landscape in southern Portugal and examined how it may be related to stone marten road mortality risk. We addressed three questions: (1) How different levels of landscape connectivity influence stone marten occurrence in montado patches? (2) Is there any relation between montado patches connectivity and stone marten road mortality risk? (3) If so, which road-related features might be responsible for the species’ high road mortality? We developed a series of connectivity models using CS scenarios with different resistance values given to each vegetation cover type to reflect different resistance to species movement. Our models showed that the likelihood of occurrence of stone marten decreased with distance to source areas, meaning continuous montado. Open areas and riparian areas within open area matrices entailed increased costs. We found higher stone marten mortality on roads in well-connected areas. Road sinuosity was an important factor influencing the mortality in those areas. This result challenges the way that connectivity and its relation to mortality has been generally regarded. Clearly, landscape connectivity and road-related mortality are not independent.     

Do female newts modify thermoregulatory behavior to manipulate egg size?

Reproductive females manipulate offspring phenotypes by modifying conditions during embryogenesis. In ectotherms, the environmental control over embryogenesis is often realized by changes in maternal thermoregulation during gravidity. To determine if reproduction influences thermoregulatory behavior in species where females lay eggs shortly after fertilization (strict oviparity), we compared preferred body temperatures (T_p) between reproductive (egg-laying) and non-reproductive female newts, Ichthyosaura alpestris. Next, we exposed reproductive females to temperatures mimicking T_p ranges of reproductive and non-reproductive individuals to find out whether the maternally modified thermal regime influences ovum and jelly coat volume, and early cleavage rates at the time of oviposition. In the thermal gradient, reproductive females maintained their body temperatures within a narrower range than non-reproductive individuals. The exposure of ovipositing females to temperatures preferred during their reproductive and non-reproductive period had a negligible influence on egg size and early cleavage rates. We conclude that the modification of maternal thermoregulatory behavior provides a limited opportunity to manipulate egg traits in newts.     

Do novel weapons that degrade mycorrhizal mutualisms promote species invasion?

Non-native plants often dominate novel habitats where they did not co-evolve with the local species. The novel weapons hypothesis suggests that non-native plants bring competitive traits against which native species have not adapted defenses. Novel weapons may directly affect plant competitors by inhibiting germination or growth, or indirectly by attacking competitor plant mutualists (degraded mutualisms hypothesis). Japanese knotweed (Fallopia japonica) and European buckthorn (Rhamnus cathartica) are widespread plant invaders that produce potent secondary compounds that negatively impact plant competitors. We tested whether their impacts were consistent with a direct effect on the tree seedlings (novel weapons) or an indirect attack via degradation of seedling mutualists (degraded mutualism). We compared recruitment and performance using three Ulmus congeners and three Betula congeners treated with allelopathic root macerations from allopatric and sympatric ranges. Moreover, given that the allelopathic species would be less likely to degrade their own fungal symbiont types, we used arbuscular mycorrhizal (AMF) and ectomycorrhizal (ECM) tree species to investigate the effects of F. japonica (no mycorrhizal association) and Rhamnus cathartica (ECM association) on the different fungal types. We also investigated the effects of F. japonica and R. cathartica exudates on AMF root colonization. Our results suggest that the allelopathic plant exudates impact seedlings directly by inhibiting germination and indirectly by degrading fungal mutualists. Novel weapons inhibited allopatric seedling germination but sympatric species were unaffected. However, seedling survivorship and growth appeared more dependent on mycorrhizal fungi, and mycorrhizal fungi were inhibited by allopatric species. These results suggest that novel weapons promote plant invasion by directly inhibiting allopatric competitor germination and indirectly by inhibiting mutualist fungi necessary for growth and survival.     

Do DEAD-box proteins promote group II intron splicing without unwinding RNA?

The DEAD-box protein Mss116p promotes group II intron splicing in vivo and in vitro. Here we explore two hypotheses for how Mss116p promotes group II intron splicing: by using its RNA unwinding activity to act as an RNA chaperone or by stabilizing RNA folding intermediates. We show that an Mss116p mutant in helicase motif III (SAT/AAA), which was reported to stimulate splicing without unwinding RNA, retains ATP-dependent unwinding activity and promotes unfolding of a structured RNA. Its unwinding activity increases sharply with decreasing duplex length and correlates with group II intron splicing activity in quantitative assays. Additionally, we show that Mss116p can promote ATP-independent RNA unwinding, presumably via single-strand capture, also potentially contributing to DEAD-box protein RNA chaperone activity. Our findings favor the hypothesis that DEAD-box proteins function in group II intron splicing as in other processes by using their unwinding activity to act as RNA chaperones.     

Do type 1 fimbriae promote inflammation in the human urinary tract?

Type 1 fimbriae have been implicated as virulence factors in animal models of urinary tract infection (UTI), but the function in human disease remains unclear. This study used a human challenge model to examine if type 1 fimbriae trigger inflammation in the urinary tract. The asymptomatic bacteriuria strain Escherichia coli 83972, which fails to express type 1 fimbriae, due to a 4.25 kb fimB-fimD deletion, was reconstituted with a functional fim gene cluster and fimbrial expression was monitored through a gfp reporter. Each patient was inoculated with the fim+ or fim- variants on separate occasions, and the host response to type 1 fimbriae was quantified by intraindividual comparisons of the responses to the fim+ or fim- isogens, using cytokines and neutrophils as end-points. Type 1 fimbriae did not promote inflammation and adherence was poor, as examined on exfoliated cells in urine. This was unexpected, as type 1 fimbriae enhanced the inflammatory response to the same strain in the murine urinary tract and as P fimbrial expression by E. coli 83972 enhances adherence and inflammation in challenged patients. We conclude that type 1 fimbriae do not contribute to the mucosal inflammatory response in the human urinary tract.     

Do metal ions promote the re-activation of the 2,3-bisphosphoglycerate-independent phosphoglycerate mutases?

It has been reported [Smith, McWilliams & Hass (1986) Biochem. Biophys. Res. Commun. 136, 336-340] that addition of certain metal ions, notably Co2+ and Mn2+, promoted the refolding of denatured phosphoglycerate mutase from wheat germ. We have re-investigated these experiments and have shown that, when precautions are taken to avoid artefacts in the assay system, the metal ions do not promote any re-activation of the denatured wheat-germ or Aspergillus nidulans enzymes. An alternative explanation is offered for the observations of Smith et al. (1986).     

How do serine proteases really work?

Recent advances in genetic engineering have led to a growing acceptance of the fact that enzymes work like other catalysts by reducing the activation barriers of the corresponding reactions. However, the key question about the action of enzymes is not related to the fact that they stabilize transition states but to the question to how they accomplish this task. This work considers the catalytic reaction of serine proteases and demonstrates how one can use a combination of calculations and experimental information to elucidate the key contributions to the catalytic free energy. Recent reports about genetic modifications of the buried aspartic group in serine proteases, which established the large effect of this group (but could not determine its origin), are analyzed. Two independent methods indicate that the buried aspartic group in serine proteases stabilizes the transition state by electrostatic interactions rather than by alternative mechanisms. Simple free energy considerations are used to eliminate the double proton-transfer mechanism (which is depicted in many textbooks as the key catalytic factor in serine proteases). The electrostatic stabilization of the oxyanion side of the transition state is also considered. It is argued that serine proteases and other enzymes work by providing electrostatic complementarity to the changes in charge distribution occurring during the reactions they catalyze.     

Do fast increasing food conditions promote the midsummer decline of Daphnia galeata?

Ovaries from mature giant red shrimp Aristaeomorpha foliacea were investigated histochemically and ultrastructurally. Four growing stages of the oocytes were distinguished: premeiosis stage, previtellogenetic stage, early vitellogenic stage and late vitellogenic stage. In addition, occasional resorptive oocytes were found. Oogonia and premeiotic oocytes were found in germinative zones. Previtellogenic and vitellogenic oocytes were localized in maturative zones. As vitellogenesis proceeded, oocytes showed a progressive development in the number of lipid droplets as well as in the extension of RER, constituted of dilated cisternae, uniformely scattered throughout the cytoplasm. The RER produced yolk granules and a lampbrush-like substance. The latter was released under the oolemma and constituted a characteristic cortical zone. The oolemma did not develop microvilli or micropinocytotic vesicles to incorporate yolk precursors. Thus, the protein yolk appeared to be of endogenous origin. Few somatic cells were found around the oocytes, but they never gave place to a continuous epithelial layer around oocytes, thus it is not possible to speak of ovarian follicle. The cytoplasm of these mesodermal-oocyte associated cells (MOAC) was characterized by a typical steroidogenic apparatus. Few resorptive immature oocytes were found inside late vitellogenic oocytes. Since the ovaries were packed with late vitellogenic oocytes and the few immature oocytes were hardly detectable, oocyte maturation occurred in a synchronous way.     

Do male golden egg bugs carry eggs they have fertilized? A microsatellite analysis

In the golden egg bug, Phyllomorpha laciniata (Heteroptera,Coreidae), both males and females carry eggs on their back.Although females cannot carry their own eggs, males may carryeggs that they have fertilized. If males carry eggs they havefertilized, their behavior may be interpreted as paternal care.In this article, we provide genetic data for paternity assignmentof eggs carried by 40 males collected from the field. The malesand the eggs were typed by using four highly polymorphic microsatelliteDNA markers. Out of the 247 eggs typed, 87% were excluded fromthe father-offspring relationship based on single-locus (leastconservative exclusion) mismatches. Under the more conservative(exclusion by at least two single locus mismatches) method,78% of the eggs were nonpaternal. Relatedness estimates furthersupported our paternity analyses. The average relatedness ofthe eggs to the carrying males was low (b_em = -0.052 ±0.024 SE). Within the population, males were unrelated to eachother (b_mm = -0.004 ± 0.0002 SE), as were the eggs carriedby individual males (b_eggs = -0.004 ± 0.0001 SE). Thisfirst genetic study on the breeding system of the golden eggbugs did not find any support for the claim that egg carryingfunctioned as paternal care, nor did it support kin selectionas explanation for conspecific egg carrying.     

Do sequence neighbours of intrinsically disordered regions promote structural flexibility in intrinsically disordered proteins?

Intrinsically disordered proteins (IDPs) are crucial players in various cellular activities. Several experimental and computational analyses have been conducted to study structural pliability and functional potential of IDPs. In spite of active research in past few decades, what induces structural disorder in IDPs and how is still elusive. Many studies testify that sequential and spatial neighbours often play important roles in determining structural and functional behaviour of proteins. Considering this fact, we assessed sequence neighbours of intrinsically disordered regions (IDRs) to understand if they have any role to play in inducing structural flexibility in IDPs. Our analysis includes 97% eukaryotic IDPs and 3% from bacteria and viruses. Physicochemical and structural parameters including amino acid propensity, hydrophobicity, secondary structure propensity, relative solvent accessibility, B-factor and atomic packing density are used to characterise the neighbouring residues of IDRs (NRIs). We show that NRIs exhibit a unique nature, which makes them stand out from both ordered and disordered residues. They show correlative occurrences of residue pairs like Ser-Thr and Gln-Asn, indicating their tendency to avoid strong biases of order or disorder promoting amino acids. We also find differential preferences of amino acids between N- and C-terminal neighbours, which might indicate a plausible directional effect on the dynamics of adjacent IDRs. We designed an efficient prediction tool using Random Forest to distinguish the NRIs from the ordered residues. Our findings will contribute to understand the behaviour of IDPs, and may provide potential lead in deciphering the role of IDRs in protein folding and assembly.     

Do specialized flowers promote reproductive isolation? Realized pollination accuracy of three sympatric Pedicularis species

Background and Aims

Interest in pollinator-mediated evolutionary divergence of flower phenotype and speciation in plants has been at the core of plant evolutionary studies since Darwin. Specialized pollination is predicted to lead to reproductive isolation and promote speciation among sympatric species by promoting partitioning of (1) the species of pollinators used, (2) when pollinators are used, or (3) the sites of pollen placement. Here this last mechanism is investigated by observing the pollination accuracy of sympatric Pedicularis species (Orobanchacae).

Methods

Pollinator behaviour was observed on three species of Pedicularis (P. densispica, P. tricolor and P. dichotoma) in the Hengduan Mountains, south-west China. Using fluorescent powder and dyed pollen, the accuracy was assessed of stigma contact with, and pollen deposition on, pollinating bumble-bees, respectively.

Key Results

All three species of Pedicularis were pollinated by bumble-bees. It was found that the adaptive accuracy of female function was much higher than that of male function in all three flower species. Although peak pollen deposition corresponded to the optimal location on the pollinator (i.e. the site of stigma contact) for each species, substantial amounts of pollen were scattered over much of the bees'' bodies.

Conclusions

The Pedicularis species studied in the eastern Himalayan region did not conform with Grant''s ‘Pedicularis Model’ of mechanical reproductive isolation. The specialized flowers of this diverse group of plants seem unlikely to have increased the potential for reproductive isolation or influenced rates of speciation. It is suggested instead that the extreme species richness of the Pedicularis clade was generated in other ways and that specialized flowers and substantial pollination accuracy evolved as a response to selection generated by the diversity of co-occurring congeners.     

Do cuckoos choose nests of great reed warblers on the basis of host egg appearance?

Prevailing theory assumes cuckoos lay at random among host nests within a population, although it has been suggested that cuckoos could choose large nests and relatively active pairs within host populations. We tested the hypothesis that egg matching could be improved by cuckoos choosing nests in which host eggs more closely match their own, by assessing matching and monitoring nest fate in great reed warblers naturally or experimentally parasitized by eggs of European cuckoos. A positive correlation between cuckoo and host egg visual features suggests that cuckoos do not lay at random within a population, but choose nests and this improves egg matching: naturally parasitized cuckoo eggs were more similar to host eggs as perceived by humans and as measured by spectrophotometry. Our results suggest a hitherto overlooked step in cuckoo-host evolutionary arms races, and have nontrivial implications for the common experimental practice of artificially parasitizing clutches.     

Chloroplast proteases: possible regulators of gene expression?

A wide range of proteolytic processes in the chloroplast are well recognized. These include processing of precursor proteins, removal of oxidatively damaged proteins, degradation of proteins missing their prosthetic groups or their partner subunit in a protein complex, and adjustment of the quantity of certain chloroplast proteins in response to changing environmental conditions. To date, several chloroplast proteases have been identified and cloned. The chloroplast processing enzyme is responsible for removing the transit peptides of newly imported proteins. The thylakoid processing peptidase removes the thylakoid-transfer domain from proteins translocated into the thylakoid lumen. Within the lumen, Tsp removes the carboxy-terminal tail of the precursor of the PSII D1 protein. In contrast to these processing peptidases which perform a single endo-proteolytic cut, processive proteases that can completely degrade substrate proteins also exist in chloroplasts. The serine ATP-dependent Clp protease, composed of the proteolytic subunit ClpP and the regulatory subunit ClpC, is located in the stroma, and is involved in the degradation of abnormal soluble and membrane-bound proteins. The ATP-dependent metalloprotease FtsH is bound to the thylakoid membrane, facing the stroma. It degrades unassembled proteins and is involved in the degradation of the D1 protein of PSII following photoinhibition. DegP is a serine protease bound to the lumenal side of the thylakoid membrane that might be involved in the chloroplast response to heat. All these peptidases and proteases are homologues of known bacterial enzymes. Since ATP-dependent bacterial proteases and their mitochondrial homologues are also involved in the regulation of gene expression, via their determining the levels of key regulatory proteins, chloroplast proteases are expected to play a similar role.     

When does coevolution promote diversification?

Coevolutionary interactions between species are thought to be an important cause of evolutionary diversification. Despite this general belief, little theoretical basis exists for distinguishing between the types of interactions that promote diversification and those types that have no effect or that even restrict it. Using analytical models and simulations of phenotypic evolution across a metapopulation, we show that coevolutionary interactions promote diversification when they impose a cost of phenotype matching, as is the case for competition or host-parasite antagonism. In contrast, classical coevolutionary arms races have no tendency to promote or inhibit diversification, and mutualistic interactions actually restrict diversification. Together with the results of recent phylogenetic and ecological studies, these results suggest that the causes of diversification in many coevolutionary systems may require reassessment.     

Does mercury promote lipid peroxidation?

In order to explore the observed association among mercury, atherosclerosis, and coronary heart disease, the effects of mercury, copper, and iron on the peroxidation of low-density lipoprotein (LDL) and on the enzymatic activities of glutathione peroxidase and myeloperoxidase were investigated in vitro. On the basis of our nuclear magnetic resonance (NMR) experiments, we conclude that mercury does not promote the direct nonenzymatic peroxidation of LDL, like copper and iron. In our enzyme measurements, mercury inhibited slightly myeloperoxidase, although not significantly in presence of LDL. Instead, inorganic mercury, but not methylmercury chloride, inhibited glutathione peroxidase effectively and copper event at 10 μmol/L, below physiological concentrations, doubled the inhibition rate. Copper and iron had no direct effect on glutathione peroxidase, but they both seem to activate production of HOCl by myeloperoxidase. We conclude here that, first, mercury and methylmercury do not promote direct lipid peroxidation, but that, second, a simultaneous exposure to high inorganic mercury, copper, and iron and low selenium concentrations can lead to a condition in which mercury promotes lipid peroxidations. This mechanism provides a plausible molecular-level explanation for the observed association between high body mercury content and atherosclerosis.     

Do nest boxes in restored woodlands promote the conservation of hollow‐dependent fauna?

Vegetation restoration is considered as an important strategy for reversing biodiversity decline in agricultural areas. However, revegetated areas often lack key vegetation attributes like large old hollow‐bearing trees. As these trees take a long time to develop, artificial cavities such as nest boxes are sometimes provided to address lag effects. We conducted a 3‐year experiment using 150 nest boxes with 4 designs to quantify patterns of occupancy within 16 replanted areas and 14 patches of remnant old‐growth eucalypt woodland. We quantified patterns of occupancy of nest boxes in physically connected versus isolated remnants and plantings, and multiple covariate effects on nest box occupancy at the nest box, tree, patch, and landscape levels. Our analyses revealed a lower probability of nest box occupancy within remnants (vs. plantings) for 2 of the 6 response variables examined: any species and the Feral Honeybee. Nest boxes in connected remnants and plantings were more likely to be occupied than those in isolated plantings and remnants by any mammal and the Common Brushtail Possum. Nest boxes in restored woodlands are used by some hollow‐dependent fauna but principally already common species and not taxa of conservation concern. Nest boxes were also used by pest species. A key management consideration must be to create connected habitat to facilitate colonization of nest boxes by mammals. Approximately 15% of the cavity‐dependent vertebrates within the study area used next boxes, possibly because the diverse requirements of the array of other species were not met by the range of nest boxes deployed.