Cicada ear geometry: species and sex effects

Many insect species rely on their sense of audition to find a mate, to localize prey or to escape from a predator. Cicadas are particularly known for their loud call and the conspicuous tympanal hearing system located in their abdomen. The vibration pattern of the tympanal membrane (TM) has been investigated recently revealing mechanical properties specific to species and sex. Although TM size and shape is likely to affect these patterns, the geometry of the cicada ear has never been examined per se. Focusing on three Mediterranean cicada species, namely Cicadatra atra, Cicada orni and Lyristes plebejus, we investigated the structure of TM shape variation at two levels, within and across species. Applying an elliptic Fourier analysis to the outlines of both male and female TMs, we estimated sexual dimorphism and species effects. Cicadatra atra showed a large TM compared with its small size, probably as a result of selective constraints related to the role of the TM in sound production. Sexual dimorphism seemed to be greater than interspecific variation, indicating that constraints operating on sex might be more selective than those acting on species identification. In addition, C. orni appeared to be significantly different from the two other species. This morphological peculiarity could be related to the unique vibrational pattern of its membrane. This would establish for the first time a direct link between the shape and mechanism of a hearing organ. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 101 , 922–934.     

Phylogeography of the mottled spinefoot Siganus fuscescens: Pleistocene divergence and limited genetic connectivity across the Philippine archipelago

Historical isolation during Pleistocene low sea level periods is thought to have contributed to divergence among marine basin populations across the Coral Triangle. In the Philippine archipelago, populations in the South China Sea, Sulu Sea–inland seas, and Philippine Sea‐Celebes Sea basins might have been partially isolated. Meanwhile, present‐day broadscale oceanographic circulation patterns suggest connectivity between these basins. To evaluate hypotheses regarding the influence of historical and contemporary factors on genetic structure, phylogeographic patterns based on mitochondrial control region sequences for a reef‐associated fish, Siganus fuscescens, were analysed. Three distinct lineages were recovered. One lineage was identified as the morphologically similar species Siganus canaliculatus, while two lineages are monophyletic with S. fuscescens. Clade divergence and demographic expansion in S. fuscescens occurred during the Pleistocene. A strong signal of latitudinal structure was detected (Φ_CT = 0.188), driven by marked differences in clade distribution: one clade is widely distributed (clade A), while a second clade (clade B) has a restricted northern distribution. Regional structure of clade A is consistent with the basin isolation hypothesis (Φ_CT = 0.040) and suggests isolation of the South China Sea (Φ_CT = 0.091). Fine‐scale structure was observed in the South China Sea and south Philippine Sea, while Sulu Sea and inland seas were unstructured. Genetic structure across multiple spatial scales (archipelagic, regional, and fine‐scale within basins) suggests the influence of vicariant barriers and contemporary limits to gene flow in S. fuscescens that may be influenced by oceanographic circulation, geographical distance between available habitats, and latitudinal temperature differences.     

Wnt signaling mediates reorientation of outer hair cell stereociliary bundles in the mammalian cochlea

In the mammalian cochlea, stereociliary bundles located on mechanosensory hair cells within the sensory epithelium are unidirectionally oriented. Development of this planar polarity is necessary for normal hearing as stereociliary bundles are only sensitive to vibrations in a single plane; however, the mechanisms governing their orientation are unknown. We report that Wnt signaling regulates the development of unidirectional stereociliary bundle orientation. In vitro application of Wnt7a protein or inhibitors of Wnt signaling, secreted Frizzled-related protein 1 or Wnt inhibitory factor 1, disrupts bundle orientation. Moreover, Wnt7a is expressed in a pattern consistent with a role in the polarization of the developing stereociliary bundles. We propose that Wnt signaling across the region of developing outer hair cells gives rise to planar polarity in the mammalian cochlea.     

Chemopreventive and renal protective effects for docosahexaenoic acid (DHA): implications of CRP and lipid peroxides

Background

The fish oil-derived ω-3 fatty acids, like docosahexanoic (DHA), claim a plethora of health benefits. We currently evaluated the antitumor effects of DHA, alone or in combination with cisplatin (CP) in the EAC solid tumor mice model, and monitored concomitant changes in serum levels of C-reactive protein (CRP), lipid peroxidation (measured as malondialdehyde; MDA) and leukocytic count (LC). Further, we verified the capacity of DHA to ameliorate the lethal, CP-induced nephrotoxicity in rats and the molecular mechanisms involved therein.

Results

EAC-bearing mice exhibited markedly elevated LC (2-fold), CRP (11-fold) and MDA levels (2.7-fold). DHA (125, 250 mg/kg) elicited significant, dose-dependent reductions in tumor size (38%, 79%; respectively), as well as in LC, CRP and MDA levels. These effects for CP were appreciably lower than those of DHA (250 mg/kg). Interestingly, DHA (125 mg/kg) markedly enhanced the chemopreventive effects of CP and boosted its ability to reduce serum CRP and MDA levels. Correlation studies revealed a high degree of positive association between tumor growth and each of CRP (r = 0.85) and leukocytosis (r = 0.89), thus attesting to a diagnostic/prognostic role for CRP. On the other hand, a single CP dose (10 mg/kg) induced nephrotoxicity in rats that was evidenced by proteinuria, deterioration of glomerular filtration rate (GFR, -4-fold), a rise in serum creatinine/urea levels (2–5-fold) after 4 days, and globally-induced animal fatalities after 7 days. Kidney-homogenates from CP-treated rats displayed significantly elevated MDA- and TNF-α-, but reduced GSH-, levels. Rats treated with DHA (250 mg/kg, but not 125 mg/kg) survived the lethal effects of CP, and showed a significant recovery of GFR; while their homogenates had markedly-reduced MDA- and TNF-α-, but -increased GSH-levels. Significant association was detected between creatinine level and those of MDA (r = 0.81), TNF-α ) r = 0.92) and GSH (r = -0.82); implying causal relationships.

Conclusion

DHA elicited prominent chemopreventive effects on its own, and appreciably augmented those of CP as well. The extent of tumor progression in various mouse groups was highly reflected by CRP levels (thus implying a diagnostic/prognostic role for CRP). Further, this study is the first to reveal that DHA can obliterate the lethal CP-induced nephrotoxicity and renal tissue injury. At the molecular level, DHA appears to act by reducing leukocytosis, systemic inflammation, and oxidative stress.     

Sampling genetic diversity in the sympatrically and allopatrically speciating Midas cichlid species complex over a 16 year time series

Background  

Speciation often occurs in complex or uncertain temporal and spatial contexts. Processes such as reinforcement, allopatric divergence, and assortative mating can proceed at different rates and with different strengths as populations diverge. The Central American Midas cichlid fish species complex is an important case study for understanding the processes of speciation. Previous analyses have demonstrated that allopatric processes led to species formation among the lakes of Nicaragua as well as sympatric speciation that is occurring within at least one crater lake. However, since speciation is an ongoing process and sampling genetic diversity of such lineages can be biased by collection scheme or random factors, it is important to evaluate the robustness of conclusions drawn on individual time samples.     

High risk of early sub-therapeutic penicillin concentrations after intramuscular benzathine penicillin G injections in Ethiopian children and adults with rheumatic heart disease

IntroductionIntramuscular benzathine penicillin G (BPG) injections are a cornerstone of secondary prophylaxis to prevent acute rheumatic fever (ARF) and rheumatic heart disease (RHD). Uncertainties regarding inter-ethnic and preparation variability, and target exposure profiles of BPG injection are key knowledge gaps for RHD control.MethodsTo evaluate BPG pharmacokinetics (PK) in patients receiving 4-weekly doses in Ethiopia, we conducted a prospective cohort study of ARF/RHD patients attending cardiology outpatient clinics. Serum samples were collected weekly for one month after injection and assayed with a liquid chromatography-mass spectroscopy assay. Concentration-time datasets for BPG were analyzed by nonlinear mixed effects modelling using NONMEM.ResultsA total of 190 penicillin concentration samples from 74 patients were included in the final PK model. The median age, weight, BMI was 21 years, 47 kg and 18 kg/m², respectively. When compared with estimates derived from Indigenous Australian patients, the estimate for median (95% confidence interval) volume of distribution (V/F) was lower (54.8 [43.9–66.3] l.70kg^-1) whilst the absorption half-life (t_1/2-abs2) was longer (12.0 [8.75–17.7] days). The median (IQR) percentage of time where the concentrations remained above 20 ng/mL and 10 ng/mL within the 28-day treatment cycle was 42.5% (27.5–60) and 73% (58.5–99), respectively.ConclusionsThe majority of Ethiopian patients receiving BPG as secondary prophylaxis to prevent RHD do not attain target concentrations for more than two weeks during each 4-weekly injection cycle, highlighting the limitations of current BPG strategies. Between-population variation, together with PK differences between different preparations may be important considerations for ARF/RHD control programs.     

A new technique for staining mast cells using ferroin

We describe here a new method for specific staining of mast cells using ferroin. Different hamster tissues were fixed in 4% formalin and processed for paraffin embedding. Sections were stained with hematoxylin followed by ferroin acidified with 2.5 N sulfuric acid to pH 4.0. Mast cells stained an intense orange color that contrasted markedly with bluish violet nuclei. High contrast was also observed when ferroin colored sections were counterstained with light green instead of hematoxylin. To evaluate the specificity of the stain, hamster cheek pouch sections were stained with toluidine blue, alcian blue-safranin O, and ferroin. Quantitative evaluation of mast cells stained with the three techniques showed no statistical difference. The simplicity and selectivity of this method is sufficient for image analysis of mast cells.     

A computational approach to characterization of bovine sperm chromatin alterations

We describe here a computational morphology-based approach to the investigation of possible causes of chromatin alterations in sperm. A comprehensive set of state-of-the-art and geometric measures are computationally extracted from toluidine blue stained images and analyzed to infer the possible processes leading to normal and abnormal chromatin formation while seeking a possible taxonomy of chromatin alterations and their influence on sperm head morphology. Using this methodology, we have identified higher chromatin fragility at some specific points of the sperm head. Despite the lack of correlation between morphologies of sperm head and chromatin structure, four main morphological types of chromatin alterations in bull spermatozoa have been identified and their possible causes discussed.     

Reproductive system,social organization,human disturbance and ecological dominance in native populations of the little fire ant,Wasmannia auropunctata

The invasive ant species Wasmannia auropunctata displays both ecologically dominant and non‐dominant populations within its native range. Three factors could theoretically explain the ecological dominance of some native populations of W. auropunctata: (i) its clonal reproductive system, through demographic and/or adaptive advantages; (ii) its unicolonial social organization, through lower intraspecific and efficient interspecific competition; (iii) the human disturbance of its native range, through the modification of biotic and abiotic environmental conditions. We used microsatellite markers and behavioural tests to uncover the reproductive modes and social organization of dominant and non‐dominant native populations in natural and human‐modified habitats. Microsatellite and mtDNA data indicated that dominant and non‐dominant native populations (supercolonies as determined by aggression tests) of W. auropunctata did not belong to different evolutionary units. We found that the reproductive system and the social organization are neither necessary nor sufficient to explain W. auropunctata ecological dominance. Dominance rather seems to be set off by unknown ecological factors altered by human activities, as all dominant populations were recorded in human‐modified habitats. The clonal reproductive system found in some populations of W. auropunctata may however indirectly contribute to its ecological dominance by allowing the species to expand its environmental niche, through the fixation over time of specific combinations of divergent male and female genotypes. Unicoloniality may rather promote the range expansion of already dominant populations than actually trigger ecological dominance. The W. auropunctata model illustrates the strong impact of human disturbance on species’ ecological features and the adaptive potential of clonal reproductive systems.