Ecological Correlates of Roost Fidelity in the Tent-Making Bat Artibeus watsoni

Roost switching is a common occurrence in bats, yet the causes and consequences of such behavior are poorly understood. In this study we explore the ecological correlates of roost fidelity in the tent‐making bat Artibeus watsoni, particularly focusing on the effect of sex, reproductive status, and roost availability using a three‐factor general linear model (GLM). We estimated roost fidelity of radio‐tracked individuals and found that the GLM was significant (R² = 0.72, F_10,34 = 8.91, p < 0.001). Significant interaction terms were observed for relative roost availability and sex (F_4,34 = 16.96, p < 0.001), and relative roost availability and reproductive status (F_6,34 = 7.62, p < 0.001), indicating that variation in roost fidelity among males and females, and among individuals under different breeding conditions, depended on relative roost availability at the site where they were radio‐tracked. Individuals in areas of high roost availability exhibited lower roost fidelity than those sampled in areas of lower roost availability. Females exhibited less roost fidelity than males for all roost availability categories, but the difference between males and females was only significant at high roost availability. The general pattern of decreased roost fidelity as roost availability increased was also prevalent among individuals in different breeding conditions. Additionally, satellite males exhibited higher roost fidelity than resident males in areas of low roost availability, and lactating females had higher roost fidelity than non‐breeding females in areas of medium roost availability. Our study thus demonstrates that sex, reproductive status, and roost availability all affect roost fidelity in the tent‐making bat A. watsoni, and also suggests that roost availability is the most important factor influencing roost fidelity in this bat, providing the first quantitative evidence that roost fidelity is correlated with roost abundance in a single species.     

Aerobic bacterial flora from the digestive tract of the common vampire bat, Desmodus rotundus (Chiroptera: Phyllostomidae)

This study addresses the composition of microbial flora in the vampire bat (Desmodus rotundus) primarily because all available data are outdated, and because of the economical significance of this bat species. Twenty-one bats were collected and their aerobic bacteria documented separately for stomach and intestine. Bacteria were identified through the Analytical Profile Index (API), and results analyzed with the APILAB software. A total of thirty bacterial species were isolated from sixteen females and five males. The most common species were Escherichia coli and Staphylococcus aureus, although other bacteria, such as Acinetobacterjohnsonii, Enterobacter sakazakii, Staphylococcus chromogenes, S. hyicus and S. xylosus were also common. The number of species found in the stomach and intestine was significantly different, and the intestine presented a higher diversity compared to the stomach. This has previously been found in other mammals and it is attributed to a reduction of acidity. Most of the species found in this study are considered normal components of the digestive tract of mammals, although other bacteria common in the skin of mammals and from aquatic environments were found. Bacteria from the skin may invade the vampire's stomach and/or intestine when the bat has contact with its prey, and may suggest that the vampire's feeding habit facilitates the invasion of other microbes not common in its digestive tract. The fact that bacteria from aquatic environments were also found suggests that D. rotundus, as previously found by other researchers, drinks free water when available, and water may be another source of microbial invasion.     

A Ubiquitin E2 Variant Protein Acts in Axon Termination and Synaptogenesis in Caenorhabditis elegans

In the developing nervous system, cohorts of events regulate the precise patterning of axons and formation of synapses between presynaptic neurons and their targets. The conserved PHR proteins play important roles in many aspects of axon and synapse development from C. elegans to mammals. The PHR proteins act as E3 ubiquitin ligases for the dual-leucine-zipper-bearing MAP kinase kinase kinase (DLK MAPKKK) to regulate the signal transduction cascade. In C. elegans, loss-of-function of the PHR protein RPM-1 (Regulator of Presynaptic Morphology-1) results in fewer synapses, disorganized presynaptic architecture, and axon overextension. Inactivation of the DLK-1 pathway suppresses these defects. By characterizing additional genetic suppressors of rpm-1, we present here a new member of the DLK-1 pathway, UEV-3, an E2 ubiquitin-conjugating enzyme variant. We show that uev-3 acts cell autonomously in neurons, despite its ubiquitous expression. Our genetic epistasis analysis supports a conclusion that uev-3 acts downstream of the MAPKK mkk-4 and upstream of the MAPKAPK mak-2. UEV-3 can interact with the p38 MAPK PMK-3. We postulate that UEV-3 may provide additional specificity in the DLK-1 pathway by contributing to activation of PMK-3 or limiting the substrates accessible to PMK-3.CHEMICAL synapses are specialized cellular junctions that enable neurons to communicate with their targets. An electrical impulse causes calcium channel opening and consequently stimulates synaptic vesicles in the presynaptic terminals to fuse at the plasma membrane. Neurotransmitter activates receptors on the postsynaptic membrane and triggers signal transduction in the target cell. For this communication to occur efficiently, the organization of the proteins within these juxtaposed pre- and postsynaptic terminals must be tightly regulated (Jin and Garner 2008). Previous studies in Caenorhabditis elegans have identified RPM-1, a member of the conserved PHR (Pam/Highwire/RPM-1) family of proteins, as an important regulator for the synapse (Schaefer et al. 2000; Zhen et al. 2000). Recent functional studies of other PHR proteins have shown that they are also required for a number of steps during nervous system development including axon guidance, growth, and termination (Wan et al. 2000; D''souza; et al. 2005; Bloom et al. 2007; Grill et al. 2007; Lewcock et al. 2007; Li et al. 2008).The signaling cascades regulated by the PHR proteins have been identified using genetic modifier screens (Diantonio et al. 2001; Liao et al. 2004; Nakata et al. 2005; Collins et al. 2006) and biochemical approaches (Grill et al. 2007; Wu et al. 2007). These studies reveal that a major function of PHR proteins is to act as ubiquitin E3 ligases (Jin and Garner 2008). In C. elegans, RPM-1 (Regulator of Presynaptic Morphology-1) regulates the abundance of its substrate, the dual-leucine-zipper-bearing MAP kinase kinase kinase (DLK MAPKKK), and controls the activity of the MAP kinase cascade composed of three additional kinases, MAPKK MKK-4, p38 MAPK PMK-3, and MAPKAPK MAK-2 (Nakata et al. 2005; Yan et al. 2009). This signaling cascade further regulates the activity of the CCAAT/enhancer binding protein (C/EBP), CEBP-1, via a mechanism involving 3′-UTR-mediated mRNA decay.Signal transduction involving MAP kinases can be fine tuned using multiple mechanisms to ensure optimal signaling outputs (Raman et al. 2007). For example, scaffold proteins for MAP kinases can provide spatial regulation of kinase activation in response to different stimuli (Remy and Michnick 2004; Whitmarsh 2006). Small protein tags such as ubiquitin have also been shown to control the activation of kinases. Specifically, in the IKK pathway ubiquitination via Lys63 chain formation catalyzed by the Ubc13/Uev1a E2 complex and TRAF6 E3 ligase is required for TAK1 kinase activation (Skaug et al. 2009).To further the understanding of the DLK-1 pathway in the development of the nervous system, we characterized a new complementation group of rpm-1(lf) suppressors. These mutations affect the gene uev-3, a ubiquitin E2 conjugating (UBC) enzyme variant (UEV). UEV proteins belong to the UBC family, but lack the catalytic active cysteine necessary for conjugating ubiquitin (Sancho et al. 1998). The best characterized UEV proteins are yeast Mms2 and mammalian Uev1A, both of which act as the obligatory partner for the active E2 Ubc13 and function in DNA repair and IKB pathways, respectively (Deng et al. 2000; Hurley et al. 2006). In addition, UEV proteins, such as Tsg101, can also regulate endosomal trafficking (Babst et al. 2000). We find that similar to other members of the DLK-1 pathway, uev-3 functions cell autonomously in neurons. uev-3 genetically acts downstream of mkk-4 and upstream of mak-2. UEV-3 can bind PMK-3 in heterologous protein interaction assays. We hypothesize that UEV-3 may add specificity to the DLK-1 pathway by binding to PMK-3 for its activation or for selecting specific downstream targets.     

The cyclic GMP-dependent protein kinase EGL-4 regulates olfactory adaptation in C. elegans

Prolonged odor exposure causes a specific, reversible adaptation of olfactory responses. A genetic screen for negative regulators of olfaction uncovered mutations in the cGMP-dependent protein kinase EGL-4 that disrupt olfactory adaptation in C. elegans. G protein-coupled olfactory receptors within the AWC olfactory neuron signal through cGMP and a cGMP-gated channel. The cGMP-dependent kinase functions in AWC neurons during odor exposure to direct adaptation to AWC-sensed odors, suggesting that adaptation is a cell intrinsic process initiated by cGMP. A predicted phosphorylation site on the beta subunit of the cGMP-gated channel is required for adaptation after short odor exposure, suggesting that phosphorylation of signaling molecules generates adaptation at early time points. A predicted nuclear localization signal within EGL-4 is required for adaptation after longer odor exposure, suggesting that nuclear translocation of EGL-4 triggers late forms of adaptation.     

Sound amplification by means of a horn-like roosting structure in Spix's disc-winged bat

While sound is a signal modality widely used by many animals, it is very susceptible to attenuation, hampering effective long-distance communication. A strategy to minimize sound attenuation that has been historically used by humans is to use acoustic horns; to date, no other animal is known to use a similar structure to increase sound intensity. Here, we describe how the use of a roosting structure that resembles an acoustic horn (the tapered tubes that form when new leaves of plants such as Heliconia or Calathea species start to unfurl) increases sound amplification of the incoming and outgoing social calls used by Spix''s disc-winged bat (Thyroptera tricolor) to locate roosts and group members. Our results indicate that incoming calls are significantly amplified as a result of sound waves being increasingly compressed as they move into the narrow end of the leaf. Outgoing calls were faintly amplified, probably as a result of increased sound directionality. Both types of call, however, experienced significant sound distortion, which might explain the patterns of signal recognition previously observed in behavioural experiments. Our study provides the first evidence of the potential role that a roost can play in facilitating acoustic communication in bats.     

Response of a specialist bat to the loss of a critical resource

Human activities have negatively impacted many species, particularly those with unique traits that restrict their use of resources and conditions to specific habitats. Unfortunately, few studies have been able to isolate the individual and combined effects of different threats on population persistence in a natural setting, since not all organisms can be associated with discrete habitat features occurring over limited spatial scales. We present the results of a field study that examines the short-term effects of roost loss in a specialist bat using a conspicuous, easily modified resource. We mimicked roost loss in the natural habitat and monitored individuals before and after the perturbation to determine patterns of resource use, spatial movements, and group stability. Our study focused on the disc-winged bat Thyroptera tricolor, a species highly morphologically specialized for roosting in the developing furled leaves of members of the order Zingiberales. We found that the number of species used for roosting increased, that home range size increased (before: mean 0.14±SD 0.08 ha; after: 0.73±0.68 ha), and that mean association indices decreased (before: 0.95±0.10; after: 0.77±0.18) once the roosting habitat was removed. These results demonstrate that the removal of roosting resources is associated with a decrease in roost-site preferences or selectivity, an increase in mobility of individuals, and a decrease in social cohesion. These responses may reduce fitness by potentially increasing energetic expenditure, predator exposure, and a decrease in cooperative interactions. Despite these potential risks, individuals never used roost-sites other than developing furled leaves, suggesting an extreme specialization that could ultimately jeopardize the long-term persistence of this species' local populations.