http://www.frontiersinzoology.com The latest research articles published by Frontiers in Zoology 2013-05-23T00:00:00Z IntroductionNemertea is one of the least studied lophotrochozoan phyla concerning neurogenesis. The sparse data available do not unambiguously allow for answering questions with respect to the neural groundplan of the phylum or the fate of larval neural structures during metamorphosis. In order to contribute to this issue, we studied neurotransmitter distribution during development of the pilidiophoran Lineus albocinctus Verrill, 1900. Results: Two serotonin-like immunoreactive (lir) neurons are present in the anterior part of the apical plate. They send numerous processes into the four lobes of the pilidium larva, where they form a complex subepithelial nerve net. All four larval lobes are underlain by a marginal neurite bundle, which is associated with numerous serotonin-lir monociliated perikarya. A serotonin-lir oral nerve ring encircles the stomach sphincter and is associated with few serotonin-lir conical cells. Two suboral neurites descend from the oral nerve ring and merge with the marginal neurite bundle. The oral nerve ring and the suboral neurites contain the mollusk-specific VD1/RPD2 alpha-neuropeptide. The lateral lobes of the larva have three and the anterior and the posterior lobes two VD1/RPD2-lir marginal neurite bundles. The lobar FMRFamide-lir plexus of Lineus albocinctus is much more complex than previously described for any pilidium larva. It includes a circumesophageal neurite that descends along each side of the larval esophagus and together with the inner marginal neurite bundle gives rise to the lobar plexus of the lateral lobes. An outer FMRFamide-lir marginal neurite bundle with numerous associated FMRFamide-lir marginal sensory cells surrounds all four lobes. FMRFamide-lir structures are absent in the larval apical region. The oral nerve ring and the two suboral serotonin-lir neurites are incorporated into the juvenile nervous system. Conclusion: Our study confirms the presence of serotonin-lir components in the apical region of the pilidium larva of Lineus albocinctus and thus contradicts an earlier study on the same species. We show that the nervous system of pilidium larvae, especially the FMRFamide-lir components, is much more complex than previously assumed. The presence of the VD1/RPD2-alpha-neuropeptide indicates that this compound may have been part of the lophotrochozoan neural groundplan. http://www.frontiersinzoology.com/content/10/1/31 Sabine Hindinger Thomas Schwaha Andreas Wanninger Frontiers in Zoology 2013, null:31 2013-05-23T00:00:00Z doi:10.1186/1742-9994-10-31 /content/figures/1742-9994-10-31-toc.gif Frontiers in Zoology 1742-9994 ${item.volume} 31 2013-05-23T00:00:00Z PDF IntroductionRisk assessment occurs over different temporal and spatial scales and is selected for when individuals show an adaptive response to a threat. Here, we test if birds respond to the threat of brood parasitism using the acoustical cues of brood parasites in the absence of visual stimuli. We broadcast the playback of song of three brood parasites (Chalcites cuckoo species) and a sympatric non-parasite (striated thornbill, Acanthiza lineata) in the territories of superb fairy-wrens (Malurus cyaneus) during the peak breeding period and opportunistic breeding period. The three cuckoo species differ in brood parasite prevalence and the probability of detection by the host, which we used to rank the risk of parasitism (high risk, moderate risk, low risk). Results: Host birds showed the strongest response to the threat of cuckoo parasitism in accordance with the risk of parasitism. Resident wrens had many alarm calls and close and rapid approach to the playback speaker that was broadcasting song of the high risk brood parasite (Horsfield's bronze-cuckoo, C. basalis) across the year (peak and opportunistic breeding period), some response to the moderate risk brood parasite (shining bronze-cuckoo, C. lucidus) during the peak breeding period, and the weakest response to the low risk brood parasite (little bronze-cuckoo, C. minutillus). Playback of the familiar control stimulus in wren territories evoked the least response. Conclusion: Host response to the threat of cuckoo parasitism was assessed using vocal cues of the cuckoo and was predicted by the risk of future parasitism. http://www.frontiersinzoology.com/content/10/1/30 Sonia Kleindorfer Christine Evans Diane Colombelli-Négrel Jeremy Robertson Matteo Griggio Herbert Hoi Frontiers in Zoology 2013, null:30 2013-05-22T00:00:00Z doi:10.1186/1742-9994-10-30 /content/figures/1742-9994-10-30-toc.gif Frontiers in Zoology 1742-9994 ${item.volume} 30 2013-05-22T00:00:00Z PDF Background: Females have often been shown to exhibit preferences for certain male traits. However, little is known about behavioural rules females use when searching for mates in their natural habitat. We investigated mate sampling tactics and related costs in the territorial strawberry poison frog (Oophaga pumilio) possessing a lek-like mating system, where both sequential and simultaneous sampling might occur. We continuously monitored the sampling pattern and behaviour of females during the complete period between two successive matings. Results: We found no evidence that females compared males by visiting them. Instead females mated with the closest calling male irrespective of his acoustic and physical traits, and territory size. Playback experiments in the natural home ranges of receptive females revealed that tested females preferred the nearest speaker and did not discriminate between low and high call rates or dominant frequencies. Conclusions: Our results suggest that females of O. pumilio prefer the closest calling male in the studied population. We hypothesize that the sampling tactic in this population is affected by 1) a strongly female biased sex ratio and 2) a low variance in traits of available males due to strong male-male competition, preventing low quality males from defending a territory and mating. http://www.frontiersinzoology.com/content/10/1/29 Ivonne Meuche Oscar Brusa K Linsenmair Alexander Keller Heike Pröhl Frontiers in Zoology 2013, null:29 2013-05-20T00:00:00Z doi:10.1186/1742-9994-10-29 Non-choosy female poison dart frogs pick the nearest male <p>Females in a studied population of strawberry poison dart frogs select mates purely based on distance. In a lek-based mating system, males compete for females attention through vocalizations. However, in the studied population, females are not attracted by the quality of the call, instead they opt for the closest male regardless of presumed heritable traits or parenting skills.</p> /content/figures/1742-9994-10-29-toc.gif Frontiers in Zoology 1742-9994 ${item.volume} 29 2013-05-20T00:00:00Z PDF Background: Ancient DNA has revolutionized conservation genetic studies as it allows monitoring of the genetic variability of species through time and predicting the impact of ecosystems’ threats on future population dynamics and viability. Meanwhile, the consequences of anthropogenic activities and climate change to island faunas, particularly seabirds, remain largely unknown. In this study, we examined temporal changes in the genetic diversity of a threatened seabird, the Cory’s shearwater (Calonectris borealis).FindingsWe analysed the mitochondrial DNA control region of ancient bone samples from the late-Holocene retrieved from the Canary archipelago (NE Atlantic) together with modern DNA sequences representative of the entire breeding range of the species. Our results show high levels of ancient genetic diversity in the Canaries comparable to that of the extant population. The temporal haplotype network further revealed rare but recurrent long-distance dispersal between ocean basins. The Bayesian demographic analyses reveal both regional and local population size expansion events, and this is in spite of the demographic decline experienced by the species over the last millennia. Conclusions: Our findings suggest that population connectivity of the species has acted as a buffer of genetic losses and illustrate the use of ancient DNA to uncover such cryptic genetic events. http://www.frontiersinzoology.com/content/10/1/28 Oscar Ramírez Elena Gómez-Díaz Iñigo Olalde Juan Illera Juan Rando Jacob González-Solís Carles Lalueza-Fox Frontiers in Zoology 2013, null:28 2013-05-20T00:00:00Z doi:10.1186/1742-9994-10-28 /content/figures/1742-9994-10-28-toc.gif Frontiers in Zoology 1742-9994 ${item.volume} 28 2013-05-20T00:00:00Z XML IntroductionSexual size dimorphism (SSD) is a widespread phenomenon in animals including mammals. It has been demonstrated that across species, the direction and magnitude of sexual dimorphism in body size often corresponds to social systems. Moreover, many animal lineages conform to "Rensch's rule", which states that male-biased SSD increases with body size. We tested whether considerable differences in sociality and large variation in body size were connected with the evolution of SSD in the structural body size of ground squirrels, an otherwise ecologically relatively homogenous group of terrestrial rodents. Results: We found the general trend of male-biased SSD in ground squirrels, however, male size increases nearly perfectly isometrically with female size among species and sociality does not explain departures from this relationship. Species with different sociality grades significantly differ in body size, with the most social species tending to be the largest. Conclusions: We suggest that lack of conformity with Rensch s rule in ground squirrels may be attributed to their low variation in SSD, and briefly discuss three potential causes of small magnitude of SSD in the structural size in rodents: low selection on SSD in structural dimensions, ontogenetic and genetic constraints and the existence of ecological/selection factors preventing the evolution of extensive SSD. http://www.frontiersinzoology.com/content/10/1/27 Jan Mat¿j¿ Luká¿ Kratochvíl Frontiers in Zoology 2013, null:27 2013-05-14T00:00:00Z doi:10.1186/1742-9994-10-27 /content/figures/1742-9994-10-27-toc.gif Frontiers in Zoology 1742-9994 ${item.volume} 27 2013-05-14T00:00:00Z PDF IntroductionIn long-distance migrants, a considerably higher proportion of time and energy is allocated to stopovers rather than to flights. Stopover duration and departure decisions affect consequently subsequent flight stages and overall speed of migration. In Arctic nocturnal songbird migrants the trade-off between a relatively long migration distance and short nights available for travelling may impose a significant time pressure on migrants. Therefore, we hypothesize that Alaskan northern wheatears (Oenanthe oenanthe) use a time-minimizing migration strategy to reach their African wintering area 15,000 km away. Results: We estimated the factors influencing the birds' daily departure probability from an Arctic stopover before crossing the Bering Strait by using a Cormack-Jolly-Seber model. To identify in which direction and when migration was resumed departing birds were radio-tracked. Here we show that Alaskan northern wheatears did not behave as strict time minimizers, because their departure fuel load was unrelated to fuel deposition rate. All birds departed with more fuel load than necessary for the sea crossing. Departure probability increased with stopover duration, evening fuel load and decreasing temperature. Birds took-off towards southwest and hence, followed in general the constant magnetic and geographic course but not the alternative great circle route. Nocturnal departure times were concentrated immediately after sunset. Conclusion: Although birds did not behave like time-minimizers in respect of the optimal migration strategies their surplus of fuel load clearly contradicted an energy saving strategy in terms of the minimization of overall energy cost of transport. The observed low variation in nocturnal take-off time in relation to local night length compared to similar studies in the temperate zone revealed that migrants have an innate ability to respond to changes in the external cue of night length. Likely, birds maximized their potential nightly flight range by taking off early in the night which in turn maximizes their overall migration speed. Hence, nocturnal departure time may be a crucial parameter shaping the speed of migration indicating the significance of its integration in future migration models. http://www.frontiersinzoology.com/content/10/1/26 Heiko Schmaljohann Fränzi Korner-Nievergelt Beat Naef-Daenzer Rolf Nagel Ivan Maggini Marc Bulte Franz Bairlein Frontiers in Zoology 2013, null:26 2013-05-12T00:00:00Z doi:10.1186/1742-9994-10-26 /content/figures/1742-9994-10-26-toc.gif Frontiers in Zoology 1742-9994 ${item.volume} 26 2013-05-12T00:00:00Z PDF Background: Plumage polymorphism may evolve during coevolution between brood parasites and their hosts if rare morph(s), by contravening host search image, evade host recognition systems better than common variant(s). Females of the parasitic common cuckoo (Cuculus canorus) are a classic example of discrete color polymorphism: gray females supposedly mimic the sparrowhawk (Accipiter nisus), while rufous females are believed to mimic the kestrel (Falco tinnunculus). Despite many studies on host responses to adult cuckoos comprehensive tests of the “hawk mimicry” and “kestrel mimicry” hypotheses are lacking so far. Results: We tested these hypotheses by examining host responses to stuffed dummies of the sparrowhawk, kestrel, cuckoo and the innocuous turtle dove (Streptopelia turtur) as a control at the nest. Our experimental data from an aggressive cuckoo host, the great reed warbler (Acrocephalus arundinaceus), showed low effectiveness of cuckoo-predator mimicry against more aggressive hosts regardless of the type of model and the degree of perfection of the mimic. Specifically, warblers discriminated gray cuckoos from sparrowhawks but did not discriminate rufous cuckoos from kestrels. However, both gray and rufous cuckoos were attacked vigorously and much more than control doves. The ratio of aggression to gray vs. rufous cuckoo was very similar to the ratio between frequencies of gray vs. rufous cuckoo morphs in our study population. Conclusions: Overall, our data combined with previous results from other localities suggest polymorphism dynamics are not strongly affected by local predator model frequencies. Instead, hosts responses and discrimination abilities are proportional, other things being equal, to the frequency with which hosts encounter various cuckoo morphs near their nests. This suggests that female cuckoo polymorphism is a counter-adaptation to thwart a specific host adaptation, namely an ability to not be fooled by predator mimicry. We hypothesize the dangerousness of a particular model predator (sparrowhawks are more dangerous to adult birds than kestrels) may be another important factor responsible for better discrimination between the gray cuckoo and its model rather than between the rufous cuckoo and its model. We also provide a review of relevant existing literature, detailed discussion of plumage polymorphism in cuckoos, methodological recommendations and new ideas for future work. http://www.frontiersinzoology.com/content/10/1/25 Alfréd Trnka Tomá¿ Grim Frontiers in Zoology 2013, null:25 2013-05-10T00:00:00Z doi:10.1186/1742-9994-10-25 /content/figures/1742-9994-10-25-toc.gif Frontiers in Zoology 1742-9994 ${item.volume} 25 2013-05-10T00:00:00Z XML Background: The metacestode larva of Echinococcus multilocularis (Cestoda: Taeniidae) develops in the liver of intermediate hosts (typically rodents, or accidentally in humans) as a labyrinth of interconnected cysts that infiltrate the host tissue, causing the disease alveolar echinococcosis. Within the cysts, protoscoleces (the infective stage for the definitive canid host) arise by asexual multiplication. These consist of a scolex similar to that of the adult, invaginated within a small posterior body. Despite the importance of alveolar echinococcosis for human health, relatively little is known about the basic biology, anatomy and development of E. multilocularis larvae, particularly with regard to their nervous system. Results: We describe the existence of a subtegumental nerve net in the metacestode cysts, which is immunoreactive for acetylated tubulin-α and contains small populations of nerve cells that are labeled by antibodies raised against several invertebrate neuropeptides. However, no evidence was found for the existence of cholinergic or serotoninergic elements in the cyst wall. Muscle fibers occur without any specific arrangement in the subtegumental layer, and accumulate during the invaginations of the cyst wall that form brood capsules, where protoscoleces develop. The nervous system of the protoscolex develops independently of that of the metacestode cyst, with an antero-posterior developmental gradient. The combination of antibodies against several nervous system markers resulted in a detailed description of the protoscolex nervous system, which is remarkably complex and already similar to that of the adult worm. Conclusions: We provide evidence for the first time of the existence of a nervous system in the metacestode cyst wall, which is remarkable given the lack of motility of this larval stage, and the lack of serotoninergic and cholinergic elements. We propose that it could function as a neuroendocrine system, derived from the nervous system present in the bladder tissue of other taeniids. The detailed description of the development and anatomy of the protoscolex neuromuscular system is a necessary first step toward the understanding of the developmental mechanisms operating in these peculiar larval stages. http://www.frontiersinzoology.com/content/10/1/24 Uriel Koziol Georg Krohne Klaus Brehm Frontiers in Zoology 2013, null:24 2013-05-04T00:00:00Z doi:10.1186/1742-9994-10-24 /content/figures/1742-9994-10-24-toc.gif Frontiers in Zoology 1742-9994 ${item.volume} 24 2013-05-04T00:00:00Z XML IntroductionImmune function is a vital physiological process that is often suppressed during times of resource scarcity due to investments in other physiological systems. While energy is the typical currency that has been examined in such trade-offs, limitations of other resources may similarly lead to trade-offs that affect immune function. Specifically, water is a critical resource with profound implications for organismal ecology, yet its availability can fluctuate at local, regional, and even global levels. Despite this, the effect of osmotic state on immune function has received little attention. Results: Using agglutination and lysis assays as measures of an organism’s plasma concentration of natural antibodies and capacity for foreign cell destruction, respectively, we tested the independent effects of osmotic state, digestive state, and energy balance on innate immune function in free-ranging and laboratory populations of the Gila monster, Heloderma suspectum. This desert-dwelling lizard experiences dehydration and energy resource fluctuations on a seasonal basis. Dehydration was expected to decrease innate immune function, yet we found that dehydration increased lysis and agglutination abilities in both lab and field studies, a relationship that was not simply an effect of an increased concentration of immune molecules. Laboratory-based differences in digestive state were not associated with lysis or agglutination metrics, although in our field population, a loss of fat stores was correlated with an increase in lysis. Conclusions: Depending on the life history of an organism, osmotic state may have a greater influence on immune function than energy availability. Thus, consideration of osmotic state as a factor influencing immune function will likely improve our understanding of ecoimmunology and the disease dynamics of a wide range of species. http://www.frontiersinzoology.com/content/10/1/23 Karla Moeller Michael Butler Dale DeNardo Frontiers in Zoology 2013, null:23 2013-05-04T00:00:00Z doi:10.1186/1742-9994-10-23 /content/figures/1742-9994-10-23-toc.gif Frontiers in Zoology 1742-9994 ${item.volume} 23 2013-05-04T00:00:00Z XML IntroductionHybridization is a common phenomenon in fish and is considered to be a major source of diversification. Deciphering the remoulding of genomic regions and phenotypes in zones where hybrid specimens occur is of particular interest to elucidate the emergence of evolutionary novelties. This approach is particularly challenging because the first step of hybridization seems to be the most important stage in the emergence of hybrid lineages. However, the signal can be significantly altered after only a few generations. Results: We studied 41 microsatellites and partial cytochrome b gene sequences in 970 specimens belonging to two fish species (Chondrostoma nasus and Parachondrostoma toxostoma) in allopatric/parapatric zones, hybrids between them in a natural sympatric zone: the Ardeche basin. We showed that the genomic architecture in hybrids presented pattern heterogeneity of selection for the different loci. Indeed, the upstream part of the river (Rosieres and Labeaume) presented an overdominant fitness of heterozygotes (12.20%) corresponding to a genomic compatibility, and underselection was observed for 4.88%-7.32% of the loci tested indicating a genomic incompatibility. Moreover the upstream station (Rosieres) presented a positive selection of invasive C. nasus homozygotes (17.07% to 21.95%) indicating that hybridization may increase the fitness of admixed individuals.We showed that hybrid morphology (body shape based on 21 landmarks) correlated with genomic dilution indicating a species fingerprint. However, we demonstrated that the hybrid morphology was not a linear modification between the two parental species but a trade-off between several correlated traits. Conclusions: Hybrid specimens present a mosaic of genomic combination, showing regions with genomic compatibility and others with genomic incompatibility between the two species. Positive selection (invasive advantage ranging from 9.76% to 21.95% of the loci) was evidenced in the upstream part of the Ardeche indicating that environmental selection makes a substantial contribution. Although the presence of a dam is known to impose heterogeneous hybrid zones between these two species, we demonstrated in this study that a natural environment can also generate a hybrid zone with a large number (and diversity) of hybrids. The combination of the two genomes in the hybrids results in complex ontogenetic trajectories (with different morphological traits evolving at different rates) that correspond to novel developmental pathways. http://www.frontiersinzoology.com/content/10/1/22 Melthide Sinama André Gilles Caroline Costedoat Emmanuel Corse Jean-Michel Olivier Rémi Chappaz Nicolas Pech Frontiers in Zoology 2013, null:22 2013-05-01T00:00:00Z doi:10.1186/1742-9994-10-22 /content/figures/1742-9994-10-22-toc.gif Frontiers in Zoology 1742-9994 ${item.volume} 22 2013-05-01T00:00:00Z PDF