Paternal body size affects reproductive success in laboratory-held zebrafish (<Emphasis Type=Italic>Danio rerio</Emphasis>)

Across many fish species, large females tend to exhibit higher individual reproductive success due to elevated fecundity and the provisioning of better conditioned eggs and offspring compared to small females. By contrast, effects of paternal body size on reproductive success are less well understood. We disentangled the maternal- and paternal-size dependent effects on reproductive output and early life history in zebrafish (Danio rerio). In the laboratory, females and males from four size categories (small, medium-sized, large and very large) were allowed to spawn freely in a full factorial design with 10 replicates per size combination. As expected, larger females produced more eggs and better conditioned offspring compared to smaller females. Male body size further contributed to zebrafish reproductive success: offspring sired by large males exhibited higher hatching probability and these offspring also hatched earlier and larger than offspring fertilized by small males. However, the largest males experienced lower mating success and received fewer eggs than males of the smaller size classes. While male body size substantially affected reproductive success in zebrafish, it remained unclear whether and to what degree direct paternal effects (e.g., related to sperm quality) or indirect paternal effects stemming from differential allocation patterns by females were the mechanism behind our findings. Answering this question constitutes an important future research topic.     

The effect of rearing temperature on body shape and meristic characters in zebrafish (<Emphasis Type=Italic>Danio rerio</Emphasis>) juveniles

Considering its immediate costs of producing dispensable males, the maintenance of sexual reproduction is a major paradox in evolutionary biology. Asexual lineages that do not face such costs theoretically should replace sexuals over time. Nonetheless, several systems are known in which closely related sexual and asexual lineages stably coexist. In the present study, we studied a sexual/asexual mating complex of a sperm-dependent parthenogenetic fish (amazon molly, Poecilia formosa) and its sexual congeners, the sailfin molly P. latipinna and the Atlantic molly P. mexicana. We asked whether differences in feeding behavior could contribute to their stable coexistence. We conducted a laboratory experiment to compare feeding efficiencies and also measured the competitive abilities between the two reproductive forms. Additionally, we measured gut fullness of fishes caught in natural habitats. Contrary to our predictions, we could not find P. formosa to be less efficient in feeding. We argue that food competition in mollies plays a minor role in mediating coexistence between closely related asexual and sexual mollies.     

Sex recognition in zebrafish (<Emphasis Type="Italic">Danio rerio</Emphasis>)

We investigated sex recognition in female zebrafish (Danio rerio) to better understand the underlying sensory mechanisms and identify male secondary sexual traits. Females were simultaneously presented with two fish, a male and a female, in a flow-chamber apparatus, and females’ relative attraction towards males was observed under different conditions. With domesticated fish, females were more attracted to males when presented with both visual and chemosensory cues from stimulus fish. They still discriminated the sexes when only visual cues were provided, but not when white ambient light was changed to yellow, indicating that colour plays a role. Sex discrimination under yellow light was improved when chemosensory cues were also provided. Surprisingly, females’ attraction to males was not more pronounced in the morning when mating occurs. Domesticated females discriminated the sexes when presented with wild-derived, as well as domesticated fish, whereas wild-derived females did not show any biases for domesticated or wild-derived males. Behavioural observations indicated that the wild-derived females were distressed, which explains their lack of attraction to males. In summary, domesticated female zebrafish discriminated the sexes using both visual (body colour) and olfactory cues; however, wild-derived zebrafish were too distressed for behavioural experiments under these laboratory conditions.     

Metabolic effects of cannabinoids in zebrafish (<Emphasis Type=Italic>Danio rerio</Emphasis>) embryos determined by <Superscript>1</Superscript>H NMR metabolomics

The study of drug-driven biochemical changes is important in order to determine the biomarkers associated with a specific compound activity in an individual biological system. Rodent models have been widely used to study the metabolic changes induced by psychostimulants in a cell, tissue or whole organism. However these models are not suitable for large-scale, high-throughput screening. Here, we used zebrafish embryos to study the metabolic effects of the cannabinoid receptor type 1 (CB₁) agonist (?)-(6aR,10aR)-6,6,9-trimethyl-3-pentyl-6a,7,8,10a-tetrahydro-6H-benzo[c]chromen-1-ol (?⁹-THC) and antagonist (AM251). The zebrafish embryos were exposed to ?⁹-THC and AM251 at 24 h post fertilization (hpf) for 96 h. Proton nuclear magnetic resonance based metabolomic results show an increase in the level of choline, betaine, taurine, adenosine triphosphate and glucose upon exposure to ?⁹-THC. The levels of excitatory neurotransmitters (glutamate and glutamine) increased at lower doses of ?⁹-THC, whereas toxic dose resulted in reduction of glutamate. In contrast to ?⁹-THC, AM251 caused a dose dependent reduction of betaine, choline, taurine and also reduce the level of glutamate and glutamine. Interestingly, both compounds induce the production of the dopamine precursors, phenylalanine and tyrosine at higher doses. These findings suggest that CB₁ receptor is involved in the regulation of metabolites, which might be involved in the neurotransmission of zebrafish embryos. Furthermore, our results show that zebrafish embryo can be successfully used to provide a detailed overview of general effects of drug on the overall metabolome of an intact organism.     

Expression of peroxisome proliferator-activated receptors in zebrafish (<Emphasis Type="Italic">Danio rerio</Emphasis>)

Peroxisomes increase in size and number in responsive animals ranging from mammals to marine mussels and fish species when treated with certain compounds named peroxisome proliferators. This phenomenon, known as peroxisome proliferation, is mediated by nuclear receptors termed peroxisome proliferator-activated receptors (PPARs). Three PPAR subtypes have been described (alpha, beta, and gamma) and in mammals PPARalpha is mainly expressed in tissues that catabolize fatty acids, PPARbeta is ubiquitously distributed, and PPARgamma is mainly expressed in the adipose tissue and immune system. The aim of this study was to analyze the tissue distribution of different PPAR subtypes in zebrafish Danio rerio using commercially available antibodies against PPARalpha, PPARbeta, and PPARgamma. In western blots, specific bands were detected at about 58 kDa for PPARalpha and PPARbeta. For PPARgamma the band was detected at 56 kDa. Similar results were obtained in mouse liver homogenates used as positive control, indicating the specificity of the antibodies. Immunohistochemistry was performed in paraformaldehyde-fixed tissue using either microwave or microwave plus trypsin pretreatment for antigen retrieval. In zebrafish, PPARalpha was expressed mainly in liver parenchymal cells, proximal tubules of kidney, enterocytes, and pancreas. PPARbeta showed a widespread distribution and was expressed in the liver, proximal and distal tubules and glomeruli of the kidney, pancreas, enterocytes and smooth muscle of the intestine, skin epithelium, lymphocytes, and male and female gonads. PPARgamma expression was weak in pancreatic cells, intestine, and gonads for both pretreatments. Most of the signal detected was cytoplasmic; only in the cases of PPARalpha and PPARbeta was some nuclear labeling detected in the liver. In mouse tissues, the distribution of PPAR subtypes was similar to that described previously for rats. Our results demonstrate that all three distinct PPAR subtypes are present in zebrafish. The tissue and cellular distribution of PPAR subtypes in zebrafish resembled partly that described before in mammals. Further studies are needed to decipher the functions of PPAR subtypes in zebrafish and other aquatic organisms and particularly their role in regulation of metabolic responses to xenobiotic exposure.     

Efficient separation and purification of allophycocyanin from <Emphasis Type=Italic>Spirulina</Emphasis> (<Emphasis Type=Italic>Arthrospira</Emphasis>) <Emphasis Type=Italic>platensis</Emphasis>

Allophycocyanin (APC) is a minor component of phycobiliproteins in cyanobacteria and red algae. This paper describes a simple and inexpensive extracting method for isolating APC from Spirulina (Arthrospira) platensis with high efficiency. The crude phycobiliprotein extract was pretreated by ammonium sulfate fractionation. Then, by adding hydroxylapatite into crude phycobiliprotein extract dissolved in 20 mM phosphate buffer (pH 7.0), APC was selectively adsorbed by hydroxylapatite but C-phycocyanin (C-PC) was not. The hydroxylapatite was collected and APC was extracted from the crude phycobiliprotein extract. Then, the enriched APC was washed off from the hydroxylapatite using 100 mM phosphate buffer (pH 7.0). In this simple extracting method it was easy to remove C-PC and isolate APC in large amounts. The absorbance ratio A ₆₅₀/A ₂₈₀ of extracted APC reached 2.0. The recovery yield was 70%, representing 4.61 mg · g⁻¹ wet weight. The extracted APC could be further purified by a simple anion-exchange chromatography with a pH gradient from 5.6 to 4.0. The absorbance ratio A ₆₅₀/A ₂₈₀ of the purified APC reached 5.0, and the overall recovery yield was 43%, representing 2.83 mg · g⁻¹ wet weight. Its purity was confirmed by native polyacrylamide gel electrophoresis (PAGE) and sodium dodecyl sulfate-PAGE.     

Attenuation of fibrosis <Emphasis Type=Italic>in vitro</Emphasis> and <Emphasis Type=Italic>in vivo</Emphasis> with <Emphasis Type=Italic>SPARC</Emphasis> siRNA

Introduction  

SPARC is a matricellular protein, which, along with other extracellular matrix components including collagens, is commonly over-expressed in fibrotic diseases. The purpose of this study was to examine whether inhibition of SPARC can regulate collagen expression in vitro and in vivo, and subsequently attenuate fibrotic stimulation by bleomycin in mouse skin and lungs.     

Presence of <Emphasis Type=Italic>C. albidus</Emphasis>, <Emphasis Type=Italic>C. laurentii</Emphasis> and <Emphasis Type=Italic>C. uniguttulatus</Emphasis> in Crop and Droppings of Pigeon Lofts (<Emphasis Type=Italic>Columba livia</Emphasis>)

Columba livia is an important reservoir and carrier of Cryptococcus neoformans, Cryptococcus uniguttulatus, Cryptococcus laurentii and Cryptococcus albidus. Upper digestive tract of this species is also known as a habitat for Cryptococcus neoformans. Given the increasing clinical interest of this microorganism, 331 swabs from crop and 174 dropping samples from pigeon lofts in Grand Canary Island have been studied. The obtained results show an extensive presence samples 81 positive (24.47%) of Cryptococcus spp. in analysed crops: 32 (9.66%) for C. neoformans, 24 (7.2%) for C. uniguttulatus, 23 (6.9%) for C. albidus and 2 (0.6%) for C. laurentii. In the same way, Cryptococcus spp was also isolated in 82 (47.13%), dropping samples: C. neoformans in 59 (33.9%), C. uniguttulatus, in 9 (5.17%), C. laurentii in 8 (4.59%) and C. albidus in 6 (3.44%) of the investigated samples, respectively. The cryptococcosis produced by species of cryptococci other than C. neoformans has become more important during the last decade, supporting the study on the role of pigeon in the epidemiology of this disease.     

A shifted repertoire of endocannabinoid genes in the zebrafish (<Emphasis Type="Italic">Danio rerio</Emphasis>)

The zebrafish has served as a model organism for developmental biology. Sequencing its genome has expanded zebrafish research into physiology and drug-development testing. Several cannabinoid pharmaceuticals are in development, but expression of endocannabinoid receptors and enzymes remains unknown in this species. We conducted a bioinformatics analysis of the zebrafish genome using 17 human endocannabinoid genes as a reference set. Putative zebrafish orthologs were identified in filtered BLAST searches as reciprocal best hits. Orthology was confirmed by three in silico methods: phylogenetic testing, synteny analysis, and functional mapping. Zebrafish expressed orthologs of cannabinoid receptor 1, transient receptor potential channel vanilloid receptor 4, GPR55 receptor, fatty acid amide hydrolase 1, monoacylglycerol lipase, NAPE-selective phospholipase D, abhydrolase domain-containing protein 4, and diacylglycerol lipase alpha and beta; and paired paralogs of cannabinoid receptor 2, fatty acid amide hydrolase 2, peroxisome proliferator-activated receptor alpha, prostaglandin-endoperoxide synthase 2, and transient receptor potential cation channel subtype A1. Functional mapping suggested the orthologs of transient receptor potential vanilloid receptor 1 and peroxisome proliferator-activated receptor gamma lack specific amino acids critical for cannabinoid ligand binding. No orthologs of N-acylethanolamine acid amidase or protein tyrosine phosphatase, non-receptor type 22 were identified. In conclusion, the zebrafish genome expresses a shifted repertoire of endocannabinoid genes. In vitro analyses are warranted before using zebrafish for cannabinoid development testing.     

Interaction of <Emphasis Type=Italic>Bdellovibrio bacteriovorus</Emphasis> with bacteria <Emphasis Type=Italic>Campylobacter jejuni</Emphasis> and <Emphasis Type=Italic>Helicobacter pylori</Emphasis>

Interaction of Bdellovibrio bacteriovorus 100NCJB with bacteria Campylobacter jejuni (strains 1, 2, 3, 4, and 5) and Helicobacter pylori, strain TX30a, was confirmed. The results indicate that lytic activity of bdellovibrios both in liquid media and cells attached to a surface was observed. The potential use of the antimicrobial activity of predatory bacteria for environmental bioprotection and public health is discussed.     

Manifestation of salt tolerance of <Emphasis Type=Italic>Spirulina platensis</Emphasis> and <Emphasis Type=Italic>Spirulina maxima</Emphasis> cyanobacteria of the genus <Emphasis Type=Italic>Arthrospira (Spirulina)</Emphasis>

The salt tolerance of two representatives of genus Spirulina (Arthrospira) Spirulina platensis and Spirulina maxima has been investigated. They both are the wide-spread objects of photobiotechnology and it has been shown that the content of 5–15 % sea-water in medium has not caused the decreasing of biomass yield more than 15–20% as compared with control. The further decreasing of biomass was proportionate to sea-water content in medium. The investigation of reactivity of native (intravital) exometabolites secreted into cultural medium has showed that the sea-water content influence the oxidative activity (OA) of exometabolites and hour’s rhythmics.     

Rapid growth and out-crossing promote female development in zebrafish (<Emphasis Type="Italic">Danio rerio</Emphasis>)

Sex determination in fishes is often enigmatic, a situation that is often made even more complex by the fact that the process of sexual differentiation in many species may be influenced by environmental conditions. This situation is typified in zebrafish, a popular model organism. Despite the vast array of information available for the species, the genetic controls of sex are unknown. Further, environmental parameters, such as rearing densities, seem to exert an influence on the sex ratios of captive stocks. In an effort to dissect the genetic and environmental controls underlying the expression of sex in this species, we manipulated growth of pure-bred and out-crossed zebrafish by varying their food supply during development. Faster-growing zebrafish were more likely to be female than siblings that were fed less, and out-crossed broods had higher proportions of females than broods from pure-bred crosses. The dependence of sex ratio on feeding rate is readily understood in terms of adaptive sex allocation: zebrafish life history seems to confer the greater pay-off for large size on females. A similar male/female difference in the pay-off for hybrid vigor could similarly account for the female bias of out-crossed broods—and it could be a manifestation of Haldane’s rule.     

The larval morphology and systematics of the leaf-beetles <Emphasis Type=Italic>Altica deserticola</Emphasis> and <Emphasis Type=Italic>Altica engstroemi</Emphasis> (Coleoptera,Chrysomelidae)

The elder-instar larva of Altica deserticola is described for the first time, and the last-instar larva of A. engstroemi is re-described. The diagnostic characters are included. The former species develops on Glycyrrhiza, and the latter one, on Filipendula ulmaria. Some questions on the general morphology of the larvae of Altica are discussed.     

Habitat,density, and spatial distribution of <Emphasis Type=Italic>Rivulus giarettai</Emphasis> (<Emphasis Type=Italic>Actinopterygii</Emphasis>, <Emphasis Type=Italic>Cyprinodontiformes</Emphasis>) in southeastern Brazil

We present data on the habitat, density, and spatial distribution of Rivulus giarettai, and discuss some biotic and abiotic variables related to its abundance in Free Flowing Waters (FFW) and Dam Reservoirs (DR) in palm grove (Mauritia flexuosa) marshes (Veredas) in Uberlandia, Minas Gerais, southeastern Brazil. The mean density (individuals/plot) of R. giarettai was about 13 times higher in FFW than in DR. In FFW, the density of R. giarettai was highest at intermediate amounts of substrate (plant mass) and it was positively rank-correlated with the depth, and the number of arthropods. Individuals occurred in an aggregated distribution. The aggregated pattern could be related to a concentration of individuals in microhabitats neither too much exposed nor completely saturated by plants. R. giarettai was relatively abundant and tolerant to slight man-made habitat modifications. Damming appeared to be especially problematic by negatively affecting its density.     

<Emphasis Type=Italic>Barleria compacta</Emphasis>: a new species in <Emphasis Type=Italic>Barleria</Emphasis> sect. <Emphasis Type=Italic>Prionitis</Emphasis> (Acanthaceae) from Somalia

Following a re-examination of the material treated under Barleria brevispina (Fiori) Hedrén in the recent Flora of Somalia account of the Acanthaceae, it is concluded that two distinct species are involved and Barleria compacta Malombe & I. Darbysh. is described here from north-eastern Somalia. Its affinities and conservation status are discussed.