Characterization of photoreceptor cell types in the little brown bat Myotis lucifugus (Vespertilionidae)

We report the expression of three visual opsins in the retina of the little brown bat (Myotis lucifugus, Vespertilionidae). Gene sequences for a rod-specific opsin and two cone-specific opsins were cloned from cDNA derived from bat eyes. Comparative sequence analyses indicate that the two cone opsins correspond to an ultraviolet short-wavelength opsin (SWS1) and a long-wavelength opsin (LWS). Immunocytochemistry using antisera to visual opsins revealed that the little brown bat retina contains two types of cone photoreceptors within a rod-dominated background. However, unlike other mammalian photoreceptors, M. lucifugus cones and rods are morphologically indistinguishable by light microscopy. Both photoreceptor types have a thin, elongated outer segment. Using microspectrophotometry we classified the absorption spectrum for the ubiquitous rods. Similar to other mammals, bat rhodopsin has an absorption peak near 500 nm. Although we were unable to confirm a spectral range, cellular and molecular analyses indicate that M. lucifugus expresses two types of cone visual pigments located within the photoreceptor layer. This study provides important insights into the visual capacity of a nocturnal microchiropteran species.     

Histochemical and biochemical properties of flight muscle fibers in the little brown bat,Myotis lucifugus

Summary The purpose of this investigation was (1) to determine the fiber composition of pectoralis muscle of the little brown bat,Myotis lucifugus; (2) to compare the fiber composition of this muscle with two of the animal's accessory flight muscles; and (3) to study the effect of hibernation on pectoralis muscle fiber composition. Bat skeletal muscle fibers were also compared with those of white laboratory rats (Rattus norvegicus). Bat pectoralis muscles possessed exceptionally high oxidative capacities as indicated by their succinate dehydrogenase activities, but relatively low glycolytic potentials (phosphofructokinase activities). Muscle histochemistry demonstrated that fiber composition of bat pectorlis muscle was homogeneous; all fibers possessed high aerobic and low glycolytic potentials, and high myofibrillar ATPase activities indicating fast contractile properties. In contrast, accessory flight muscles possessed three distinguishable fiber types. During hibernation there was a significant decline in oxidative potential, no change in glycolytic potential, and no alteration in basic fiber composition of bat pectoralis muscle. The findings of this study suggest that pectoralis muscles ofM. lucifugus may approach the ultimate adaptation of a mammalian locomotory muscle for aerobic generation of muscular power.Abbreviations FG fast-twich glycolytic - FOG fast-twitch-oxydative-glycolytic - -GPDH -glycerophosphate dehydrogenase - LDH lactate dehydrogenase - NADH-D reduced nicotinamide adenine dinucleotide diaphorase - PFK phosphofructokinase - SDH succinate dehydrogenase - SO slowtwich-oxidative     

The orientation behaviour of the lesser spearnosed bat, Phyllostomus discolor (Chiroptera) in a model roost

The orientation behaviour of bats (Phyllostomus discolor, Phyllostomidae), flying inside an octagonal roost-like chamber (ø: 100cm; h: 150cm) was examined.It has been shown that the bats begin turning manoeuvres during flight by turning their head towards the direction they intend to proceed to. During early phases of the flights, cumulative navigation errors were evident, indicating that endogenous spatial information plays a major role in the orientation of the bats. During later phases of the flight this error is diminished again. So it can be concluded that the bats start to use exogenous spatial information for orientation while approaching the target.In order to investigate the relative importance of vision, echolocation and endogenous spatial information for approaching the roost, the landing lattices inside the test arena were changed for non-grid dummies. We found that: 1. combined visual and endogenous information are more important than echoacoustical cues, 2. the bats learned quickly to switch their orientation behaviour in order to get a better performance in avoiding the dummies, 3. the learning performance was influenced by the visual similarity of dummies and the real landing lattice.     

Going, going, gone: the impact of white-nose syndrome on the summer activity of the little brown bat (Myotis lucifugus)

Since its discovery in the winter of 2005-2006, white-nose syndrome (WNS) has killed over one million little brown bats (Myotis lucifugus) in the American northeast. Although many studies have reported die-offs of bats at winter hibernacula, it is important to understand how bat mortality linked to WNS at winter hibernacula affects bat activity levels in their summer ranges. In the summer (May-August) of 2007, 2008 and 2009, we recorded echolocation calls to determine bat activity at sites along the Hudson River, NY (within approx. 100 km of where WNS was first reported). We documented a 78 per cent decline in the summer activity of M. lucifugus, coinciding with the arrival and spread of WNS. We suggest that mortality of M. lucifugus in winter hibernacula is reflected by reduced levels of activity in the summer and that WNS affects the entire bat population of an area, and not only individual hibernacula.     

Habitat selection of breeding brown eared-pheasants (Crossoptilon mantchuricum) in Xiaowutaishan National Nature Reserve, Hebei Province, China

From April to July of 2003–2005, we investigated habitat selection of breeding brown eared-pheasants (Crossoptilon mantchuricum) in the Xiaowutaishan National Nature Reserve, Hebei Province. Our results show that brown eared-pheasants preferred deciduous-coniferous mixed or deciduous forests with altitudes ranging from 1600 to 2200 m, steep gradients of slopes and medium or high positions on slopes. Moreover, they preferred habitats with more tree species, larger diameters at the breast height, more density and cover of trees and habitats with more types of grasses, high density and cover of grasses, but with fewer types of shrubs and lower density and cover of shrubs. They had larger territories in the early breeding stage than in the late breeding stage. There were significant differences in diameters at the breast height of trees, average height of trees, cover of trees, density of shrubs, cover of shrubs, aspect, distance to path, distance to water, distance to forest edge (P < 0.01, respectively), density of trees, type of shrubs, height of shrubs, type of grasses, density of grasses and proportion of bareness (P < 0.05, respectively). The result of the principal component analysis suggested that the principal components among the 23 habitat factors were the average height of trees, density of trees, diameters at the breast height of trees, density of shrubs, cover of shrubs and density of grasses. The differences in habitat selection of brown eared-pheasants between early breeding and late breeding stages may correlate with the dynamics of ambient environmental conditions, the reproductive behavior and energy requirements in their sub-stages of breeding.     

The role of olfaction and vision in the foraging behaviour of an echolocating megachiropteran fruit bat,Rousettus leschenaulti (Pteropodidae)

Many mammals use multimodal sensory information to find their food in complex environments. We studied the roles of olfactory and visual cues in the foraging behaviour of Rousettus leschenaulti, a tongue-clicking megachiropteran bat. We conducted experiments by offering a whole fruit, mashed fruit without shape and an artificial fruit to R. leschenaulti in dim light as well as in total darkness. R. leschenaulti responded to whole guava fruit and mashed guava fruit even in total darkness, whereas, artificial fruit similar to real fruit in size, shape and structure was ignored even when illuminated. These results reveal that odour may act as the primary cue for R. leschenaulti in finding fruit.     

Histochemical and biochemical plasticity of muscle fibers in the little brown bat (Myotis lucifugus)

Summary Fiber composition, and glycolytic and oxidative capacities of the pectoralis, gastrocnemius, and cardiac muscles from active and hibernating little brown bats (Myotis lucifugus) was studied. The data were used to test two hypotheses: First, since hibernating bats maintain the capability of flight and make use of leg muscles to maintain a roosting position all winter, the fiber composition of the pectoralis and gastrocnemius muscles should not change with season. Second, we tested the hypothesis of Ianuzzo et al. (in press), who propose that the oxidative potential of mammalian cardiac muscle should increase with increasing heart rate while glycolytic potential should not. Our results indicate that the fiber composition of the pectoralis muscle was uniformly fast-twitch oxidative (FO)_ regardless of the time of year, as predicted. However, the gastrocnemius muscle exhibited a change in FO composition from 83% in active to 61% in hibernating animals. Contrary to the variable change in histochemical properties with metabolic state, a trend of reduced maximal oxidative (CS) and glycolytic (PFK) potential during hibernation in both flight and leg muscles was apparent. The oxidative potential of flight and leg muscles decreased by 15.2% and 56.5%, respectively, while the glycolytic potential of the same muscles decreased by 23.5% and 60.5%, respectively. As predicted, the glycolytic potential of cardiac muscle remained constant between active and hibernating bats, although there was a significant decrease (22.0%) in oxidative potential during hibernation.Abbreviations FO fast-twitch oxidative - FG fast-twitch glycolytic - SO slow-twitch oxidative - Vmax maximal enzyme activity - PFK phosphofructokinase - CS citrate synthase     

Activity and shelter selection by Myotis myotis and Rhinolophus hipposideros hibernating in the Kateřinská cave (Czech Republic)

In 1992–1993, the bat species Myotis myotis and Rhinolophus hipposideros hibernating in the Kateřinská cave were investigated by means of regular censuses without any handling and marking of the animals. Three basic parameters of their shelters were recorded (position in cave, type and relative height). In total, during 26 checks we registered 1141 findings of nine bat species. Movement activity, expressed as percentage of new findings during a particular visit, was registered during the whole winter season. Its level fluctuated in different ways and the hibernation period of R. hipposideros could be divided into three different parts, while the level of M. myotis movement activity was relatively high during all season. The shelter selection of R. hipposideros was not dependent on the part of cave where the bats were hibernating, and it did not change during the season. Hibernating specimens of R. hipposideros most frequently used exposed places, in which they were always hanging free. Myotis myotis was registered in all types of shelter with one exception. Rhinolophus hipposideros used mainly the middle part of the cave at a distance between 121 and 180 m from the entrance. The most preferred part of the cave by M. myotis was a small segment of Corridor (between 21 and 30 m), i.e., the entrance part of the cave. Rhinolophus hipposideros is a highly specialized species which prefers parts of the cave with very stable microclimatic conditions and, on the contrary, M. myotis appears to be indifferent to all parameters studied, and it uses the shelters indiscriminately.     

Differences in food delivered to chicks by males and females of little auks ( Alle alle ) on South Spitsbergen

Sex differences in the quality and quantity of food loads brought to little auk (Alle alle) chicks were investigated in a large colony in Hornsund (South Spitsbergen). Adults returning to the colony were caught in mist-nets and food loads were taken from their gular pouch. The sex of each bird was determined by means of molecular methods. Females brought significantly more food per single load than males in terms of wet weight (30% more on average), number of prey items (46%) and energy contents (39%). However, there was no difference between the sexes in the size of prey taken. Energy-rich Calanus glacialis, originating from cold Arctic waters, was the most frequent prey item and made up the majority of food loads brought by both males and females (75 and 72%, respectively). This indicates that both sexes forage mainly in Arctic waters. However, differences in the proportion of cold water Calanus species (C. glacialis and C. hyperboreus), warm water Calanus species (C. finmarchicus), as well as other taxa, between males and females may suggest different ways of exploiting the feeding area.     

Spatial patterns in at-sea behaviour during spring migration by little gulls ( Larus minutus ) in the southeastern North Sea

At-sea distribution of seabirds has been studied on different scales and with different focus in many parts of the world. However, factors and/or processes causing certain patterns are often not easily explained. This also holds true for fast migrating species of international conservation concern, such as the little gull (Larus minutus) in the German Bight (southeastern North Sea). In this study, we used multiyear distributional data in combination with behavioural observations and food sampling to investigate spatial and temporal patterns and their possible causes during spring migration. The results show a highly focussed migration pattern during the last week of April and the first week of May. The river Eider seemed to play an important role as main migration route. Highest numbers were found either close to the mainland or close to the offshore islands. Little gulls used certain subareas for intense feeding (i.e. the region near Helgoland and the outlet of river Elbe) and others for migration. Hydrographic phenomena such as fronts and foam lines play an important role within the feeding sites and strongly influence behaviour and distribution. Feeding behaviour as well as samples of probable prey revealed different quality of feeding sites according to the energy density of the most abundant probable food items (drowned insects versus zooplankton and fish). In conclusion, the area utilisation of L. minutus during spring migration in the German Bight showed a clear pattern, and sites with main feeding action should be regarded as sensitive for little gulls, at least during spring migration.     

Signatures of functional constraint at aye-aye opsin genes: the potential of adaptive color vision in a nocturnal primate

While color vision perception is thought to be adaptively correlated with foraging efficiency for diurnal mammals, those that forage exclusively at night may not need color vision nor have the capacity for it. Indeed, although the basic condition for mammals is dichromacy, diverse nocturnal mammals have only monochromatic vision, resulting from functional loss of the short-wavelength sensitive opsin gene. However, many nocturnal primates maintain intact two opsin genes and thus have dichromatic capacity. The evolutionary significance of this surprising observation has not yet been elucidated. We used a molecular population genetics approach to test evolutionary hypotheses for the two intact opsin genes of the fully nocturnal aye-aye (Daubentonia madagascariensis), a highly unusual and endangered Madagascar primate. No evidence of gene degradation in either opsin gene was observed for any of 8 aye-aye individuals examined. Furthermore, levels of nucleotide diversity for opsin gene functional sites were lower than those for 15 neutrally evolving intergenic regions (>25 kb in total), which is consistent with a history of purifying selection on aye-aye opsin genes. The most likely explanation for these findings is that dichromacy is advantageous for aye-ayes despite their nocturnal activity pattern. We speculate that dichromatic nocturnal primates may be able to perceive color while foraging under moonlight conditions, and suggest that behavioral and ecological comparisons among dichromatic and monochromatic nocturnal primates will help to elucidate the specific activities for which color vision perception is advantageous.     

Mechanisms of resistance to the brown planthopperNilaparvata lugens in wild rice (Oryza spp.) cultivars

Three wild rice species and six cultivated rice varieties were evaluated to determine their mechanisms of resistance toNilaparvata lugens (Stal.). Wild rice species,Oryza officinalis, O. punctata, andO. latifolia and cultivated rices Rathu Heenati (Bph 3), Babawee (bph 4), ARC 10 550 (bph 5), Swarnalata (Bph 6), Ptb 33 (bph 2+Bph 3) and the susceptible Taichung Native (TN 1) (no resistance gene) were included in the study. In a free choice seedbox screening test, wild rice species maintained their high level of resistance through the 48 h exposure toN. lugens nymphs while plant damage ratings of cultivated rice varieties increased with time. Wild rices were non preferred and significantly more individuals settled on susceptible TN 1 followed by cultivated rices. The quantity of food ingested and assimilated byN. lugens on wild rices was less than on cultivated resistant varieties.N. lugens caged on resistant wild rices had slow nymphal development, reduced longevity, low fecundity, and low egg hatchability as compared toN. lugens on cultivated resistant varieties.     

Population dynamics of little brown bats (Myotis lucifugus) at summer roosts: Apparent survival,fidelity, abundance,and the influence of winter conditions

1. White‐nose syndrome (WNS) has caused the death of millions of bats, but the impacts have been more difficult to identify in western North America. Understanding how WNS, or other threats, impacts western bats may require monitoring other roosts, such as maternity roosts and night roosts, where bats aggregate in large numbers.
2. Little brown bats (Myotis lucifugus) are experiencing some of the greatest declines from WNS. Estimating survival and understanding population dynamics can provide valuable data for assessing population declines and informing conservation efforts.
3. We conducted a 5‐year mark–recapture study of two M. lucifugus roosts in Colorado. We used the robust design model to estimate apparent survival, fidelity, and abundance to understand population dynamics, and environmental covariates to understand how summer and winter weather conditions impact adult female survival. We compared the fidelity and capture probability of M. lucifugus between colonies to understand how bats use such roosts.
4. Overwinter survival increased with the number of days with temperatures below freezing (β > 0.100, SE = 0.003) and decreased with the number of days with snow cover (β < −0.40, SE < 0.13). Adult female fidelity was higher at one maternity roost than the other. Overwinter and oversummer adult female survival was high (>0.90), and based on survival estimates and fungal‐swabbing results, we believe these populations have yet to experience WNS.
5. Recapture of M. lucifugus using antennas that continuously read passive integrated transponder tags allows rigorous estimation of bat population parameters that can elucidate trends in abundance and changes in survival. Monitoring populations at summer roosts can provide unique population ecology data that monitoring hibernacula alone may not. Because few adult males are captured at maternity colonies, and juvenile males have low fidelity, additional effort should focus on understanding male M. lucifugus population dynamics.

     

Post-Pleistocene range expansion of the recently imperiled eastern little brown bat (Myotis lucifugus lucifugus) from a single southern refugium

Myotis lucifugus, once among the most widespread and common bats in North America, has been forecast to be extirpated east of the Rockies in as few as 16 years by the spread of white-nose syndrome. Recent genetic research has demonstrated that this species is paraphyletic and part of a broader species complex; however, only one lineage (Myotis lucifugus lucifugus [M. l. lucifugus]) is present in eastern North America. I used molecular tools and niche modeling to validate this and investigate the role that historical biogeography has played in the phylogenetic and population genetic structure of this species to determine if the eastern subspecies represents an evolutionarily distinct population.To establish the genetic structure within M. l. lucifugus, I densely sampled maternity colonies in Minnesota and sequenced 182 individuals for a portion of cytochrome b. Phylogenetic reconstruction and a haplotype network were used to infer the relationships among mitochondrial haplotypes. Population growth statistics were calculated to determine if there was evidence of significant expansion, and an environmental niche model (ENM) was constructed based on conditions during the last glacial maximum (LGM) to illustrate potential glacial refugia. All individuals derived from a single mitochondrial lineage. Genetic evidence points to population growth starting approximately 18 kya. ENM results show that there was likely a single large southern refugium extending across the southeastern United States and possibly several isolated refugia in western North America. Myotis lucifugus lucifugus likely maintained both a large range and a large population during the peaks of the glacial cycles, and its population appears to have expanded following the retreat of the Laurentide ice sheet. This imperiled lineage likely diverged in isolation from other members of the M. lucifugus/western long-eared Myotis during the Pleistocene.     

Identification of Several Cytoplasmic HSP70 Genes from the Mediterranean Mussel (Mytilus galloprovincialis) and Their Long-Term Evolution in Mollusca and Metazoa

The HSP70 protein family consists one of the most conserved and important systems for cellular homeostasis under both stress and physiological conditions. The genes of this family are poorly studied in Mollusca, which is the second largest metazoan phylum. To study these genes in Mollusca, we have isolated and identified five HSP70 genes from Mytilus galloprovincialis (Mediterranean mussel) and investigated their short-term evolution within Mollusca and their long-term evolution within Metazoa. Both sequence and phylogenetic analyses suggested that the isolated genes belong to the cytoplasmic (CYT) group of the HSP70 genes. Two of these genes probably represent cognates, whereas the remaining probably represent heat-inducible genes. Phylogenetic analysis including several molluscan CYT HSP70s reveals that the cognate genes in two species have very similar sequences and form intraspecies phylogenetic clades, differently from most metazoan cognate genes studied thus far, implying either recent gene duplications or concerted evolution. The M. galloprovincialis heat-inducible genes show intraspecies phylogenetic clustering, which in combination with the higher amino acid than nucleotide identity suggests that both gene conversion and purifying selection should be responsible for their sequence homogenization. Phylogenetic analysis including several metazoan HSP70s suggests that at least two types of CYT genes were present in the common ancestor of vertebrates and invertebrates, the first giving birth to the heat-inducible genes of invertebrates, whereas the other to both the heat-inducible genes of vertebrates and the cognate genes of all metazoans. These analyses also suggest that inducible and cognate genes seem to undergo divergent evolution. Electronic Supplementary Material Electronic Supplementary material is available for this article at and accessible for authorised users. [Reviewing Editor: Dr. Yves Van de Peer] Elena Drosopoulou and Nikolas Nikolaidis contributed equally to the present report.     

Evolution of the alcohol dehydrogenase (ADH) genes in yeast: characterization of a fourth ADH in Kluyveromyces lactis

Summary Three alcohol dehydrogenase (ADH) genes have recently been characterized in the yeast Kluyveromyces lactis. We report on a fourth ADH in K. lactis (KADH II: KADH2 gene) which is highly similar to other ADHs in K. lactis and Saccharomyces cerevisiae. KADH II appears to be a cytoplasmic enzyme, and after expression of KADH2 in S. cerevisiae enzyme activity comigrated with a K. lactis ADH present in cells grown in glucose or in ethanol. KADH I was also expressed in S. cerevisiae and it comigrated with a major ADH species expressed under glucose growth conditions in K. lactis. The substrate specificities for KADH I and KADH II were shown to be more similar to that of SADH II than to SADH I. SADH I cannot efficiently utilize long chain alcohols, in contrast to other cytoplasmic yeast ADHs, presumably because of the presence of a methionine (residue 271) in its substrate binding cleft. A comparison of the DNA sequences of ADHs among K. lactis, S. cerevisiae and Schizosaccharomyces pombe suggests that the ancestral yeast species contained one cytoplasmic ADH. After divergence from S. pombe, the ADH in the ancestor to K. lactis and S. cerevisiae was duplicated, and one ADH became localized to the mitochondrion, presumably for the oxidative use of ethanol. Following the speciation of S. cerevisiae and K. lactis, the gene encoding the cytoplasmic ADH in S. cerevisiae duplicated, which resulted in the development of the SADH II protein as the primary oxidative enzyme in place of SADH III. In contrast, the K. lactis mitochondrial ADH duplicated to give rise to the highly expressed KADH3 and KADH4 genes, both of which may still play primary roles in oxidative metabolism. These data suggest that K. lactis and S. cerevisiae use different compartments for their metabolism of ethanol. Our results also indicate that the complex regulatory circuits controlling the glucose-repressible SADH2 in S. cerevisiae are a recent acquisition from regulatory networks used for the control of genes other than SADH2.

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RT-qPCR reveals opsin gene upregulation associated with age and sex in guppies (Poecilia reticulata) - a species with color-based sexual selection and 11 visual-opsin genes

Background  

PCR-based surveys have shown that guppies (Poecilia reticulata) have an unusually large visual-opsin gene repertoire. This has led to speculation that opsin duplication and divergence has enhanced the evolution of elaborate male coloration because it improves spectral sensitivity and/or discrimination in females. However, this conjecture on evolutionary connections between opsin repertoire, vision, mate choice, and male coloration was generated with little data on gene expression. Here, we used RT-qPCR to survey visual-opsin gene expression in the eyes of males, females, and juveniles in order to further understand color-based sexual selection from the perspective of the visual system.