Olfactory cue use by three-spined sticklebacks foraging in turbid water: prey detection or prey location?

Foraging, when senses are limited to olfaction, is composed of two distinct stages: the detection of prey and the location of prey. While specialist olfactory foragers are able to locate prey using olfactory cues alone, this may not be the case for foragers that rely primarily on vision. Visual predators in aquatic systems may be faced with poor visual conditions such as natural or human-induced turbidity. The ability of visual predators to compensate for poor visual conditions by using other senses is not well understood, although it is widely accepted that primarily visual fish, such as three-spined sticklebacks, Gasterosteus aculeatus, can detect and use olfactory cues for a range of purposes. We investigated the ability of sticklebacks to detect the presence of prey and to locate prey precisely, using olfaction, in clear and turbid (two levels) water. When provided with only a visual cue, or only an olfactory cue, sticklebacks showed a similar ability to detect prey, but a combination of these cues improved their performance. In open-arena foraging trials, a dispersed olfactory cue added to the water (masking cues from the prey) improved foraging success, contrary to our expectations, whereas activity levels and swimming speed did not change as a result of olfactory cue availability. We suggest that olfaction functions to allow visual predators to detect rather than locate prey and that olfactory cues have an appetitive effect, enhancing motivation to forage

Prey aggregation is an effective olfactory predator avoidance strategy

Predator–prey interactions have a major effect on species abundance and diversity, and aggregation is a well-known anti-predator behaviour. For immobile prey, the effectiveness of aggregation depends on two conditions: (a) the inability of the predator to consume all prey in a group and (b) detection of a single large group not being proportionally easier than that of several small groups. How prey aggregation influences predation rates when visual cues are restricted, such as in turbid water, has not been thoroughly investigated. We carried out foraging (predation) experiments using a fish predator and (dead) chironomid larvae as prey in both laboratory and field settings. In the laboratory, a reduction in visual cue availability (in turbid water) led to a delay in the location of aggregated prey compared to when visual cues were available. Aggregated prey suffered high mortality once discovered, leading to better survival of dispersed prey in the longer term. We attribute this to the inability of the dead prey to take evasive action. In the field (where prey were placed in feeding stations that allowed transmission of olfactory but not visual cues), aggregated (large groups) and semi-dispersed prey survived for longer than dispersed prey—including long termsurvival. Together, our results indicate that similar to systems where predators hunt using vision, aggregation is an effective anti-predator behaviour for prey avoiding olfactory predators

Generation of a poor prognostic chronic lymphocytic leukemia-like disease model: PKC subversion induces up-regulation of PKC II expression in B lymphocytes

Overwhelming evidence identifies the microenvironment as a critical factor in the development and progression of chronic lymphocytic leukemia, underlining the importance of developing suitable translational models to study the pathogenesis of the disease. We previously established that stable expression of kinase dead protein kinase C alpha in hematopoietic progenitor cells resulted in the development of a chronic lymphocytic leukemia-like disease in mice. Here we demonstrate that this chronic lymphocytic leukemia model resembles the more aggressive subset of chronic lymphocytic leukemia, expressing predominantly unmutated immunoglobulin heavy chain genes, with upregulated tyrosine kinase ZAP-70 expression and elevated ERK-MAPK-mTor signaling, resulting in enhanced proliferation and increased tumor load in lymphoid organs. Reduced function of PKCα leads to an up-regulation of PKCβII expression, which is also associated with a poor prognostic subset of human chronic lymphocytic leukemia samples. Treatment of chronic lymphocytic leukemia-like cells with the selective PKCβ inhibitor enzastaurin caused cell cycle arrest and apoptosis both in vitro and in vivo, and a reduction in the leukemic burden in vivo. These results demonstrate the importance of PKCβII in chronic lymphocytic leukemia-like disease progression and suggest a role for PKCα subversion in creating permissive conditions for leukemogenesis

Influence of Self-Reported Standards on Romantic Mate Choice

Past research on mate standards has generally focused on identifying people’s reported standards, with the assumption that these reports accurately predict later partnering behavior. However, only a handful of studies have examined this assumption directly, most of which have involved either speed-dating contexts where stated preferences do not appear to predict initial mating judgments (e.g., Eastwick & Finkel, 2008), or relational contexts where standard-partner consistency is assessed in already established relationships (e.g., Fletcher, Simpson, & Thomas, 2000). The goal of our research was to assess unmarried individuals’ previously reported (i.e., a priori) standards and investigate the conditions under which these standards predict the characteristics of the partners people choose in subsequently formed relationships. We used a sample of 79 unmarried adults to test our hypotheses that people would choose a mate who more closely matched their a priori standards when they had higher mate value and mate availability, reported being in a committed rather than casual relationship, and indicated higher current desire for marriage (i.e., marriage imminence) and standard salience. Our results indicated found that higher minimum standards for physical attractiveness and vitality did predict becoming involved with a partner who was higher in these traits. Also, as predicted, participants with higher standard salience were more likely than participants with a lower standard salience to enter a relationship with someone who more closely matched their a priori standards on status/resources, trustworthiness, and total mate standards. Contrary to our hypothesis, we found that people with lower mate availability were actually partnered with people who more closely reflected their standards for physical attractiveness. Mate value, relationship type, and marital imminence did not moderate any of the associations examined

Secretory vesicles are preferentially targeted to areas of low molecular SNARE density

Intercellular communication is commonly mediated by the regulated fusion, or exocytosis, of vesicles with the cell surface. SNARE (soluble N-ethymaleimide sensitive factor attachment protein receptor) proteins are the catalytic core of the secretory machinery, driving vesicle and plasma membrane merger. Plasma membrane SNAREs (tSNAREs) are proposed to reside in dense clusters containing many molecules, thus providing a concentrated reservoir to promote membrane fusion. However, biophysical experiments suggest that a small number of SNAREs are sufficient to drive a single fusion event. Here we show, using molecular imaging, that the majority of tSNARE molecules are spatially separated from secretory vesicles. Furthermore, the motilities of the individual tSNAREs are constrained in membrane micro-domains, maintaining a non-random molecular distribution and limiting the maximum number of molecules encountered by secretory vesicles. Together our results provide a new model for the molecular mechanism of regulated exocytosis and demonstrate the exquisite organization of the plasma membrane at the level of individual molecular machines

Should sex ratio distorting parasites abandon horizontal transmission?

BACKGROUND: Sex-ratio distorting parasites are of interest due to their effects upon host population dynamics and their potential to influence the evolution of host sex determination systems. In theory, the ability to distort host sex-ratios allows a parasite with efficient vertical (hereditary) transmission to dispense completely with horizontal (infectious) transmission. However, recent empirical studies indicate that some sex-ratio distorting parasites have retained the capability for horizontal transmission. RESULTS: Numerical simulations using biologically realistic parameters suggest that a feminising parasite is only likely to lose the capability for horizontal transmission if its host occurs at low density and/or has a male-biased primary sex ratio. It is also demonstrated that even a small amount of horizontal transmission can allow multiple feminising parasites to coexist within a single host population. Finally it is shown that, by boosting its host's rate of population growth, a feminising parasite can increase its own horizontal transmission and allow the invasion of other, more virulent parasites. CONCLUSIONS: The prediction that sex-ratio distorting parasites are likely to retain a degree of horizontal transmission has important implications for the epidemiology and host-parasite interactions of these organisms. It may also explain the frequent co-occurrence of several sex-ratio distorting parasite species in nature

Risk factors for fatality in HIV-infected patients with dideoxynucleoside-induced severe hyperlactataemia or lactic acidosis.

BACKGROUND: Lactic acidosis (LA) and severe hyperlactataemia (HL) are infrequent but serious complications of antiretroviral therapy that have been associated with a high fatality rate. METHODS: In a multinational retrospective cohort study, LA was defined as arterial blood pH5 mmol/l. Logistic regression was used to identify factors associated with fatality. Sensitivity and specificity of different case definitions as predictors of death were compared. RESULTS: The overall case-fatality rate was 19/110 (17.3%), but among acidotic patients it was 33% (16/49 cases). There were 10 asymptomatic patients and none of them died as a consequence of the event. The median lactate for fatal, non-fatal and all patients was 8.3 mmol/l (IQR 7.2-13.1), 6.4 mmol/l (IQR 5.4-7.8) and 6.7 mmol/l (IQR 5.5-8.1), respectively. After adjusting for age and current CD4(+) T-cell count, lactate >7 mmol/l (OR 6.27, 95% CI 1.13-34.93), blood bicarbonate 18 mmol/l, 95% CI 1.33-75.65) and concurrent opportunistic infections (OR 8.69, 95% CI 1.45-52.22) were independently associated with case fatality. Blood lactate >7 mmol/l showed a sensitivity of 84% for fatality with a specificity of 60%, whereas bicarbonate 7 mmol/l and blood bicarbonate <18 mmol/l appear to predict death and might help clinicians in selecting patients who may benefit from more intense monitoring

Parahepatospora carcini n. gen., n. sp., a parasite of invasive Carcinus maenas with intermediate features of sporogony between the Enterocytozoon clade and other microsporidia

Parahepatospora carcini n. gen. n. sp., is a novel microsporidian parasite discovered infecting the cytoplasm of epithelial cells of the hepatopancreas of a single Carcinus maenas specimen. The crab was sampled from within its invasive range in Atlantic Canada (Nova Scotia). Histopathology and transmission electron microscopy were used to show the development of the parasite within a simple interfacial membrane, culminating in the formation of unikaryotic spores with 5-6 turns of an isofilar polar filament. Formation of a multinucleate meront (>12 nuclei observed) preceded thickening and invagination of the plasmodial membrane, and in many cases, formation of spore extrusion precursors (polar filaments, anchoring disk) prior to complete separation of pre-sporoblasts from the sporogonial plasmodium. This developmental feature is intermediate between the Enterocytozoonidae (formation of spore extrusion precursors within the sporont plasmodium) and all other Microsporidia (formation of spore extrusion precursors after separation of sporont from the sporont plasmodium). SSU rRNA-based gene phylogenies place P. carcini within microsporidian Clade IV, between the Enterocytozoonidae and the so-called Enterocytospora-clade, which includes Enterocytospora artemiae and Globulispora mitoportans. Both of these groups contain gut-infecting microsporidians of aquatic invertebrates, fish and humans. According to morphological and phylogenetic characters, we propose that P. carcini occupies a basal position to the Enterocytozoonidae. We discuss the discovery of this parasite from a taxonomic perspective and consider its origins and presence within a high profile invasive host on the Atlantic Canadian coastline