This is an RSS newsfeed from BioMed Central It is intended to be used with an RSS reader. For more information about RSS newsfeeds from BioMed Central, visit http://www.biomedcentral.com/info/about/rss/ http://www.frontiersinzoology.com The latest articles from Frontiers in Zoology (ISSN 1742-9994) published by BioMed Central Background: Identification of DNA sequence diversity is a powerful means for assessing the species present in environmental samples. The most common molecular strategies for estimating taxonomic composition depend upon PCR with universal primers that amplify an orthologous DNA region from a range of species. The diversity of sequences within a sample that can be detected by universal primers is often compromised by high concentrations of some DNA templates. If the DNA within the sample contains a small number of sequences in relatively high concentrations, then less concentrated sequences are often not amplified because the PCR favours the dominant DNA types. This is a particular problem in molecular diet studies, where predator DNA is often present in great excess of food-derived DNA. Results: We have developed a strategy where a universal PCR simultaneously amplifies DNA from food items present in DNA purified from stomach samples, while the predator's own DNA is blocked from amplification by the addition of a modified predator-specific blocking primer. Three different types of modified primers were tested out; one annealing inhibiting primer overlapping with the 3' end of one of the universal primers, another annealing inhibiting primer also having an internal modification of five dI molecules making it a dual priming oligo, and a third elongation arrest primer located between the two universal primers. All blocking primers were modified with a C3 spacer. In artificial PCR mixtures, annealing inhibiting primers proved to be the most efficient ones and this method reduced predator amplicons to undetectable levels even when predator template was present in 1000 fold excess of the prey template. The prey template then showed strong PCR amplification where none was detectable without the addition of blocking primer. Our method was applied to identifying the winter food of one of the most abundant animals in the world, the Antarctic krill, Euphausia superba. Dietary item DNA was PCR amplified from a range of species in krill stomachs for which we had no prior sequence knowledge. Conclusions: We present a simple, robust and cheap method that is easily adaptable to many situations where a rare DNA template is to be PCR amplified in the presence of a higher concentration template with identical PCR primer binding sites. http://www.frontiersinzoology.com/content/5/1/12 Hege Vestheim and Simon N. Jarman Frontiers in Zoology 2008, 5:12 2008-07-20 doi:10.1186/1742-9994-5-12 Frontiers in Zoology 1742-9994 5 12 2008-07-20 Background: Eicosanoids are biologically active, oxygenated metabolites of three C20 polyunsaturated fatty acids. They act as signalling molecules within the autocrine or paracrine system in both vertebrates and invertebrates mainly functioning as important mediators in reproduction, the immune system and ion transport. The biosynthesis of eicosanoids has been intensively studied in mammals and it is known that they are synthesised from the fatty acid, arachidonic acid, through either the cyclooxygenase (COX) pathway; the lipoxygenase (LOX) pathway; or the cytochrome P450 epoxygenase pathway. However, little is still known about the synthesis and structure of the pathway in invertebrates. Results: Here, we show transcriptomic evidence from Daphnia magna (Crustacea: Branchiopoda) together with a bioinformatic analysis of the D. pulex genome providing insight on the role of eicosanoids in these crustaceans as well as outlining a putative pathway of eicosanoid biosynthesis. Daphnia appear only to have one copy of the gene encoding the key enzyme COX, and phylogenetic analysis reveals that the predicted protein sequence of Daphnia COX clusters with other invertebrates. There is no current evidence of an epoxygenase pathway in Daphnia; however, LOX products are most certainly synthesised in daphnids. Conclusion: We have outlined the structure of eicosanoid biosynthesis in Daphnia, a key genus in freshwater ecosystems. Improved knowledge of the function and synthesis of eicosanoids in Daphnia and other invertebrates could have important implications for several areas within ecology. This provisional overview of daphnid eicosanoid biosynthesis provides a guide on where to focus future research activities in this area. http://www.frontiersinzoology.com/content/5/1/11 Lars-Henrik Heckmann, Richard M Sibly, Martijn JTN Timmermans and Amanda Callaghan Frontiers in Zoology 2008, 5:11 2008-07-14 doi:10.1186/1742-9994-5-11 Frontiers in Zoology 1742-9994 5 11 2008-07-14 Background: In the Lepidoptera it was historically believed that adult butterflies rely primarily on larval-derived nutrients for reproduction and somatic maintenance. However, recent studies highlight the complex interactions between storage reserves and adult income, and that the latter may contribute significantly to reproduction. Effects of adult diet were commonly assessed by determining the number and/or size of the eggs produced, whilst its consequences for egg composition and offspring viability were largely neglected (as is generally true for insects). We here specifically focus on these latter issues by using the fruit-feeding tropical butterfly Bicyclus anynana, which is highly dependent on adult-derived carbohydrates for reproduction. Results: Adult diet of female B. anynana had pronounced effects on fecundity, egg composition and egg hatching success, with butterflies feeding on the complex nutrition of banana fruit performing best. Adding vitamins and minerals to a sucrose-based diet increased fecundity, but not offspring viability. All other groups (plain sucrose solution, sucrose solution enriched with lipids or yeast) had a substantially lower fecundity and egg hatching success compared to the banana group. Differences were particularly pronounced later in life, presumably indicating the depletion of essential nutrients in sucrose-fed females. Effects of adult diet on egg composition were not straightforward, indicating complex interactions among specific compounds. There was some evidence that total egg energy and water content were related to hatching success, while egg protein, lipid, glycogen and free carbohydrate content did not seem to limit successful development. Conclusion: The patterns shown here exemplify the complexity of reproductive resource allocation in B. anynana, and the need to consider egg composition and offspring viability when trying to estimate the effects of adult nutrition on fitness in this butterfly and other insects. http://www.frontiersinzoology.com/content/5/1/10 Thorin L Geister, Matthias W Lorenz, Klaus H Hoffmann and Klaus Fischer Frontiers in Zoology 2008, 5:10 2008-07-10 doi:10.1186/1742-9994-5-10 Frontiers in Zoology 1742-9994 5 10 2008-07-10 Background: Frogs primitively have a biphasic life history with an aquatic larva (tadpole) and a usually terrestrial adult. However, direct developing frogs of the genus Eleutherodactylus have lost a free living larval stage. Many larval structures never form during development of Eleutherodactylus, while limbs, spinal cord, and an adult-like cranial musculoskeletal system develop precociously. Results: Here, I compare growth and differentiation of the retina and tectum and development of early axon tracts in the brain between Eleutherodactylus coqui and the biphasically developing frogs Discoglossus pictus, Physalaemus pustulosus, and Xenopus laevis using morphometry, immunohistochemical detection of proliferating cell nuclear antigen (PCNA) and acetylated tubulin, biocytin tracing, and in situ hybridization for NeuroD. Findings of the present study indicate that retinotectal development was greatly altered during evolution of Eleutherodactlyus mostly due to acceleration of cell proliferation and growth in retina and tectum. However, differentiation of retina, tectum, and fiber tracts in the embryonic brain proceed along a conserved slower schedule and remain temporally coordinated with each other in E. coqui. Conclusion: These findings reveal a mosaic pattern of changes in the development of the central nervous system (CNS) during evolution of the direct developing genus Eleutherodactylus. Whereas differentiation events in directly interconnected parts of the CNS such as retina, tectum, and brain tracts remained coordinated presumably due to their interdependent development, they were dissociated from proliferation control and from differentiation events in other parts of the CNS such as the spinal cord. This suggests that mosaic evolutionary changes reflect the modular character of CNS development. http://www.frontiersinzoology.com/content/5/1/9 Gerhard Schlosser Frontiers in Zoology 2008, 5:9 2008-06-23 doi:10.1186/1742-9994-5-9 Frontiers in Zoology 1742-9994 5 9 2008-06-23 Background: During long-distance foraging in almost featureless habitats desert ants of the genus Cataglyphis employ path-integrating mechanisms (vector navigation). This navigational strategy requires an egocentric monitoring of the foraging path by incrementally integrating direction, distance, and inclination of the path. Monitoring the latter two parameters involves idiothetic cues and hence is tightly coupled to the ant's locomotor behavior. Results: In a kinematic study of desert ant locomotion performed on differently inclined surfaces we aimed at pinpointing the relevant mechanisms of estimating step length and inclination. In a behavioral experiment with ants foraging on slippery surfaces we broke the otherwise tightly coupled relationship between stepping frequency and step length and examined the animals' ability to monitor distances covered even under those adverse conditions. We show that the ants' locomotor system is not influenced by inclined paths. After removing the effect of speed, slope had only marginal influence on kinematic parameters. Conclusion: From the obtained data we infer that the previously proposed monitoring of angles of the thorax-coxa joint is not involved in inclinometry. Due to the tiny variations in cycle period, we also argue that an efference copy of the central pattern generator coding the step length in its output frequency will most likely not suffice for estimating step length and complementing the pedometer. Finally we propose that sensing forces acting on the ant's legs could provide the desired neuronal correlate employed in monitoring inclination and step length. http://www.frontiersinzoology.com/content/5/1/8 Tobias Seidl and Rüdiger Wehner Frontiers in Zoology 2008, 5:8 2008-06-02 doi:10.1186/1742-9994-5-8 Frontiers in Zoology 1742-9994 5 8 2008-06-02 Background: In adult male Marcusenius pongolensis the duration of their Electric Organ Discharge (EOD) pulses increases with body size over lifetime (267 to 818 μs, field-measured). Spawning males have been observed to exhibit an additional, temporary pulse duration increase which probably betters their mating success but increases predation risk by electroreceptive catfish. We here study the question of how the additional pulse duration increase is triggered and for how long it persists, in an attempt to understand the compromise between opposing selective forces. Results: Here, we demonstrate short-term plasticity in male EOD waveform in 10 captive M. pongolensis. An increase in EOD duration was experimentally evoked in two different ways: by exchanging the familiar neighbours of experimental subjects for stranger males that were separated by plastic mesh partitions, or by separating familiar fish by plastic mesh partitions introduced into their common tank. Both treatments evoked an increase of male EOD duration. Values exceeded those found in the non-reproductive season in nature. In one male the increase of EOD duration was 5.7 fold, from 356 μs to 2029 μs. An increase in EOD duration was accompanied by a high level of aggression directed against the neighbours through the plastic mesh. With conditions remaining constant, EOD duration receded to 38 – 50% of the maximum EOD duration after 10 weeks, or, more rapidly, when sensory contact between the fish was severely restricted by the introduction of a solid plastic wall. Conclusion: The short-term increase of EOD duration evoked by experimental manipulation of sensory contact with conspecifics through the plastic mesh, as reported here, resembled the changes in EOD waveform that accompanied reproduction in two captive males. Plasticity of the male EOD in pulse duration seems to be an adaptation for (1) securing a higher fitness by a sexually "attractive" long-duration EOD, while (2) limiting the risk of detection by electroreceptive predators, such as the sharptooth catfish, by receding to a shorter EOD as soon as reproduction is over. http://www.frontiersinzoology.com/content/5/1/7 Susanne Hanika and Bernd Kramer Frontiers in Zoology 2008, 5:7 2008-05-20 doi:10.1186/1742-9994-5-7 Frontiers in Zoology 1742-9994 5 7 2008-05-20 Background: The planarian Schmidtea mediterranea and the cnidarian Hydra vulgaris have emerged as valuable model organisms in regeneration and stem cell research because of their prominent ability to regenerate a complete organism from any small body fragment. Under natural conditions wounding may result from predator attacks. These injuries open their innermost to a wide array of microbes present in the environment. Therefore, we established the hypothesis that regeneration processes may be linked to or at least accompanied by innate immune responses. In order to screen for septic wounding inducible genes we dissected individuals using a scalpel in the presence of a crude bacterial lipopolysaccharide preparation that is commonly used to elicit innate immune responses in animals and applied the suppression subtractive hybridization technique that selectively amplifies cDNAs of differentially expressed genes. Results: This analysis revealed the induced expression of 27 genes in immune challenged Schmidtea and 35 genes in immune challenged Hydra. Identified genes from both animals encode proteins that share sequence similarities with potential homologues from other organisms known to be involved in signaling (e.g. calreticulin in Schmidtea and major vault protein in Hydra), stress responses (e.g. Hsp20 in Schmidtea and a PRP19/PSO4 DNA repair protein in Hydra), or to represent potential antimicrobial effectors (e.g. perforin-like protein in Schmidtea and PR-1-like protein and neutrophil cytosolic factor 1 in Hydra). As expected, septic wounding also induces expression of genes in Schmidtea and Hydra potentially involved in tissue remodeling associated with regeneration processes (e.g. matrix metalloproteinase in Schmidtea and a potential von Willebrand factor in Hydra). Conclusion: We identified numerous immune-inducible genes in Hydra and Schmidtea that show a similar distribution corresponding to their physiological roles, although lineages of both animals split from their common ancestor for more than five hundred millions of years. The present study is the first analysis of immune-inducible genes of these two phylogenetically distant model organisms of regeneration and provide numerous candidate genes that we can use as a starting point for comparative examination of interrelationships between immunity and homeostasis. http://www.frontiersinzoology.com/content/5/1/6 Boran Altincicek and Andreas Vilcinskas Frontiers in Zoology 2008, 5:6 2008-04-27 doi:10.1186/1742-9994-5-6 Frontiers in Zoology 1742-9994 5 6 2008-04-27 Background: The development of specialized appendages involved in sperm transfer in the males of julid millipedes is an extreme case of specialized, complex structures differentiating in a very advanced phase of post-embryonic development. Here, a non-systemic metamorphosis affects the external morphology and the internal anatomy of a trunk double segment only.Presentation of the hypothesisWe hypothesize that during early (possibly embryonic) development a segmental marker is produced that remains unexploited throughout late embryonic and early post-embryonic development, until, activated by a systemic signal, it finally determines the release of a segmentally localized but anatomically major change.Testing the hypothesisKey to testing the hypothesis are (1) the identification of both the putative segmental marker involved in the localization of the legs to be eventually metamorphosed into gonopods and the systemic signal activating it, (2) the identification of the cell population from which the gonopods are built, and (3) a longitudinal study of the marker's expression throughout late embryonic and, possibly, post-embryonic development.Implications of the hypothesisProving the validity of this hypothesis would demonstrate the existence of a cryptic developmental module that will be activated only months, or years, after it has been first laid down during early development. This study also opens a window onto the very poorly explored domain of late expression of developmental genes and molecular control of late developmental events. http://www.frontiersinzoology.com/content/5/1/5 Leandro Drago, Giuseppe Fusco and Alessandro Minelli Frontiers in Zoology 2008, 5:5 2008-04-08 doi:10.1186/1742-9994-5-5 Frontiers in Zoology 1742-9994 5 5 2008-04-08 Background: Foraging behaviour is an essential ecological process linking different trophic levels. A central assumption of foraging theory is that food selection maximises the fitness of the consumer. It remains unknown, however, whether animals use innate or learned behaviour to discriminate food rewards. While many studies demonstrated that previous experience is a strong determinant of complex food choices such as diet mixing, the response to simple nutritional stimuli, such as sugar concentrations, is often believed to be innate. Results: Here we show that previous experience determines the ability to track changes in sugar composition in same-aged individuals of a short-lived migratory songbird, the garden warbler (Sylvia borin). Although birds received identical foods for seven months prior to the experiment, wild-caught birds achieved higher sugar intake rates than hand-raised birds when confronted with alternative, differently coloured, novel food types. Hand-raised and wild birds did not differ in their initial colour selection or overall food intake, but wild birds were quicker to adjust food choice to varying sugar intake. Conclusion: Over a period of at least seven months, broader previous experience translates into a higher plasticity of food choice leading to higher nutrient intake. Our results thus highlight the need to address previous long-term experience in foraging experiments. Furthermore, they show that hand-raised animals are often poor surrogates for testing the foraging behaviour of wild animals. http://www.frontiersinzoology.com/content/5/1/4 H Martin Schaefer, Kathrin Spitzer and Franz Bairlein Frontiers in Zoology 2008, 5:4 2008-02-22 doi:10.1186/1742-9994-5-4 Frontiers in Zoology 1742-9994 5 4 2008-02-22 Background: The evolution of reproductive traits, such as hybrid incompatibility (postzygotic isolation) and species recognition (prezygotic isolation), have shown their key role in speciation. Theoretical modeling has recently predicted that close linkage between genes controlling pre- and postzygotic reproductive isolation could accelerate the conditions for speciation. Postzygotic isolation could develop during the sympatric speciation process contributing to the divergence of populations. Using hybrid fitness as a measure of postzygotic reproductive isolation, we empirically studied population divergence in perch (Perca fluviatilis L.) from two genetically divergent populations within a lake. Results: During spawning time of perch we artificially created parental offspring and F1 hybrids of the two populations and studied fertilization rate and hatching success under laboratory conditions. The combined fitness measure (product of fertilization rate and hatching success) of F1 hybrids was significantly reduced compared to offspring from within population crosses. Conclusion: Our results suggest intrinsic genetic incompatibility between the two populations and indicate that population divergence between two populations of perch inhabiting the same lake may indeed be promoted by postzygotic isolation. http://www.frontiersinzoology.com/content/5/1/3 Jasminca Behrmann-Godel and Gabriele Gerlach Frontiers in Zoology 2008, 5:3 2008-01-24 doi:10.1186/1742-9994-5-3 Frontiers in Zoology 1742-9994 5 3 2008-01-24