Limb Deformities as an Emerging Parasitic Disease in Amphibians: Evidence from Museum Specimens and Resurvey Data

Abstract:   Widespread reports of malformed amphibians are of growing conservation concern. Although accounts of mass malformations (>5%) in North American amphibian populations date back to the 1940s, they are often poorly documented and are rarely explained. We reviewed available information for nine historical accounts from California, Colorado, Idaho, Mississippi, Montana, Ohio, and Texas reported between 1946 and 1988. We then asked the following questions: (1) Which of these cases were associated with Ribeiroia (Trematoda: Digenea) infection? (2) Are malformations still occurring at these sites? And (3) if so, have the frequency or types of abnormalities changed? Each site was resurveyed between 1999 and 2002, and original voucher specimens were redescribed and examined for trematode infection. Direct identification and classification by discriminant function analysis indicated that historical malformations at six of eight sites were associated with infection by Ribeiroia , dating back as far as 1946. Malformations recorded historically at these sites were consistent with the documented effects of Ribeiroia infection, including extra limbs, cutaneous fusion, and bony triangles. Of the six sites that still supported amphibians upon resurvey, three continued to support severe limb malformations at frequencies of 7–50% in one or more species. Although no pesticides were detected, amphibians from each of these sites were infected with Ribeiroia metacercariae. Taken together, these results suggest that Ribeiroia infection has historically been an important cause of mass malformations in amphibians. We conclude that although parasite-induced malformations are not a new phenomenon, there is qualitative evidence suggesting that their prevalence has increased recently, and we highlight the need for long-term research to evaluate the impacts of malformations on amphibian population viability.     

Environmental Determinants of Recent Endemism of Batrachochytrium dendrobatidis Infections in Amphibian Assemblages in the Absence of Disease Outbreaks

The inconsistent distribution of large‐scale infection mediated die‐offs and the subsequent population declines of several animal species, urges us to understand how, when, and why species are affected by disease. It is often unclear when or under what conditions a pathogen constitutes a threat to a host. Often, variation of environmental conditions plays a role. Globally Batrachochytrium dendrobatidis (Bd) causes amphibian declines; however, host responses are inconsistent and this fungus appears equally capable of reaching a state of endemism and subsequent co‐existence with native amphibian assemblages. We sought to identify environmental and temporal factors that facilitate host–pathogen coexistence in northern Europe. To do this, we used molecular diagnostics to examine archived and wild amphibians for infection and general linear mixed models to explore relationships between environmental variables and prevalence of infection in 5 well‐sampled amphibian species. We first detected infection in archived animals collected in 1999, and infection was ubiquitous, but rare, throughout the study period (2008–2010). Prevalence of infection exhibited significant annual fluctuations. Despite extremely rare cases of lethal chytridiomycosis in A. obstetricans, Bd prevalence was uncorrelated with this species’ population growth. Our results suggest context dependent and species‐specific host susceptibility. Thus, we believe recent endemism of Bd coincides with environmentally driven Bd prevalence fluctuations that preclude the build‐up of Bd infection beyond the critical threshold for large‐scale mortality and host population crashes. Determinantes Ambientales del Endemismo Reciente de Infecciones de Batrachochytrium dendrobatidis en Conjuntos de Anfibios en Ausencia de Brotes de Enfermedades Spitzen et al.     

Batrachochytrium dendrobatidis and the Collapse of Anuran Species Richness and Abundance in the Upper Manu National Park,Southeastern Peru

Abstract: Amphibians are declining worldwide, but these declines have been particularly dramatic in tropical mountains, where high endemism and vulnerability to an introduced fungal pathogen, Batrachochytrium dendrobatidis (Bd), is associated with amphibian extinctions. We surveyed frogs in the Peruvian Andes in montane forests along a steep elevational gradient (1200–3700 m). We used visual encounter surveys to sample stream‐dwelling and arboreal species and leaf‐litter plots to sample terrestrial‐breeding species. We compared species richness and abundance among the wet seasons of 1999, 2008, and 2009. Despite similar sampling effort among years, the number of species (46 in 1999) declined by 47% between 1999 and 2008 and by 38% between 1999 and 2009. When we combined the number of species we found in 2008 and 2009, the decline from 1999 was 36%. Declines of stream‐dwelling and arboreal species (a reduction in species richness of 55%) were much greater than declines of terrestrial‐breeding species (reduction of 20% in 2008 and 24% in 2009). Similarly, abundances of stream‐dwelling and arboreal frogs were lower in the combined 2008–2009 period than in 1999, whereas densities of frogs in leaf‐litter plots did not differ among survey years. These declines may be associated with the infection of frogs with Bd. B. dendrobatidis prevalence correlated significantly with the proportion of species that were absent from the 2008 and 2009 surveys along the elevational gradient. Our results suggest Bd may have arrived at the site between 1999 and 2007, which is consistent with the hypothesis that this pathogen is spreading in epidemic waves along the Andean cordilleras. Our results also indicate a rapid decline of frog species richness and abundance in our study area, a national park that contains many endemic amphibian species and is high in amphibian species richness.     

The genetic mating system of a sex-role-reversed pipefish (Syngnathus typhle): a molecular inquiry

In the pipefish Syngnathus typhle as in other species of Syngnathidae, developing embryos are reared on the male's ventral surface. Although much laboratory research has been directed toward understanding sexual selection in this sex-role-reversed species, few studies have addressed the mating behavior of S. typhle in the wild, and none has capitalized upon the power of molecular genetic assays. Here we present the first direct assessment of the genetic mating system of S. typhle in nature. Novel microsatellite loci were cloned and characterized from this species, and employed to assay entire broods from 30 pregnant, field-captured males. Genetic analysis of 1340 embryos revealed that 1–6 females (mean = 3.1) contributed to each brooded clutch, the highest rate of multiple maternity yet documented in any pipefish. Evidence of multiple mating by females was also detected. Thus, this population of S. typhle displays a polygynandrous mating system, a finding consistent with previous field and laboratory observations. Our results, considered together with similar studies of other syngnathid species, provide preliminary support for the hypothesis that the genetic mating system is related to the evolution of sexual dimorphism in the fish family Syngnathidae. Received: 19 January 1999 / Received in revised form: 15 April 1999 / Accepted: 9 May 1999     

Prevalence of Staphylococcus aureus and Pseudomonas aeruginosa in indoor air flora of a district hospital, Mandya, Karnataka

Two year (1998 and 1999) extensive survey was carried out in Mandya district hospital, Karnataka for a period of three years to monitor the prevalence of Staphylococcus aureus, Pseudomonas aeruginosa (S. aureus and Ps. aeruginosa) from the indoor air samples of operation theater labor room, children's ward, male and female general wards postoperative wards etc. A rotary air sampler loaded with manital salt and Pseudomonas selection agar media strips were used to collect the samples from various sites. The survivallence results revealed the prevalence of S. aureus and Ps. aeruginosa in almost all sampling sites, irrespective of season indicating their long-term survival and consequent threat to hospitalized patients as well the working employees.     

Molecular phylogeny of mud crabs (Brachyura: Panopeidae) from the northwestern Atlantic and the role of morphological stasis and convergence

 Mud crabs of the family Panopeidae are common organisms in coastal soft-bottom, vegetated, rubble, and oyster-bed communities along the temperate and tropical coastlines of the American continent. Similar morphology among many species renders their distinction and classification difficult. Here, we present phylogenies of western Atlantic Panopeidae based on DNA sequences of the mitochondrial large subunit rRNA (16S; 529 basepairs) and cytochrome oxidase I (COI; 640 basepairs) genes. Results suggest that the speciose genera Panopeus and Eurypanopeus are not monophyletic and that their taxonomy does not accurately reflect evolutionary partitions. In two cases (P. herbstii complex and E. depressus and allies), the molecular findings strongly support sister-species relationships that differ from previous morphology-based assumptions. We suggest that convergence or morphological stasis are responsible for the phenotypic similarities between divergent evolutionary lineages. Received: 23 July 1999 / Accepted: 5 April 2000     

Aerobic heterotrophic bacterial diversity in sediments of Rajakkamangalam estuary, south west coast of India

The abundance of aerobic heterotrophic bacterial population in the sediment sample of six experimental stations (S1 to S6) at Rajakkamangalam estuary was studied for a period of one year from March, 1998 to February, 1999. The important bacterial genera encountered were Pseudomonas, Bacillus, Vibrio, Escherichia, Micrococcus, Enterobacter, Salmonella, Aeromonas, Shigella, Klebsiella, Proteus, Alkaligenes, Staphylococcus, Citrobacter and Flavobacterium. The bacterial population based on numerical counts showed wide fluctuations in their distribution at different stations. Among the bacterial genera Pseuaomonas was found to be the dominant genus during the experimental period. The qualitative and quantitative distribution of microflora in the sediment samples are discussed.     

Effect of different irrigation methods on yield of red hot pepper and plant mortality caused by Phytophthora capsici Leon

This experiment was conducted in 1999 and 2000 in a field naturally infected by Phytophthora capsici to determine the effects of different irrigation methods, namely, basin (B), closed-end furrow (F), drip (D) and sprinkler (S) irrigation on dry yield of chili pepper (Capsium annuum L. K. Maras Type). Water use efficiency (WUE) and plant mortality were also measured. The averages of total applied water to the B, F, D and S plots for the two years were 937.7 mm, 920.6 mm, 886.5 and 913.4 mm, respectively. Thus, the mean seasonal water use by pepper varied from 1020.7 to 1109.7 mm. The highest water use was measured in B, followed by use for S, D and F methods. The highest mean potential dry yield with 1.58 t ha(-1) was obtained using D method. This was followed by S (1.36 t ha(-1)), B (1.13 t ha(-1)), and F (0.81 t ha(-1)) methods. In terms of plant mortality, crops having B irrigation had the highest (93.9%), followed by lessen amount to the S (3.2%), F (3.1%), and D methods (1.7%). Only the B irrigation method stimulated the development of P. capsici disease. On the other hand, mean WUEs varied between 0.7 and 1.7 kg ha(-1)mnm(-1) for Irrigation methods. WUE for D method was slightly higher than S method, but considerably higher than B and F methods.     

Molecular response of the sponge Suberites domuncula to bacterial infection

The aim of this study was the documentation of the molecular immune response of Suberites domuncula upon bacterial infection. Additionally, the bacteria that are naturally present in the sponge after prolonged aquarium maintenance were characterized. After 6 months of maintenance of S. domuncula in seawater aquaria, only one bacterial 16S rDNA sequence could be recovered, which belongs to the genus Pseudomonas. Concomitantly, morphologically uniform bacteria were found encapsulated in bacteriocytes. These findings indicate that certain bacteria, possibly of the genus Pseudomonas, are able to persist for long periods in host bacteriocytes. Subsequent to performing a previously established infection assay with S. domuncula, a potentially pathogenic Vibrio sp. was isolated from the tissues. Furthermore, the host tissue disintegrated and asexual propagation bodies (gemmules) were formed. In order to gain insights into the molecular events occurring after bacterial infection, the stress-response kinases, p38 protein kinase and JNK protein kinase, were analyzed. It is demonstrated that these two kinases are activated (phosphorylated) upon incubation of the tissue with the bacterial endotoxin lipopolysaccharide (LPS). Moreover, LPS strongly inhibits protein synthesis. It is concluded that there are many functionally different interactions between S. domuncula and bacteria and that the animal possesses mechanisms to differentiate between bacteria and to respond accordingly.     

Spatiotemporal Dynamics of Endangered Species Hotspots in the United States

Abstract: Given limited resources, many researchers advocate focusing conservation efforts on hotspots, geographical areas with high numbers of species (i.e., richness), endemic species, rare or threatened species, and/or high levels of threat to species survival. The hotspot approach is an efficient and simple way to conserve species diversity, assuming that hotspots do not change over space or time. We tested whether hotspots change across space and time using a database of endangered and threatened species listed by the U.S. government from 1967 to 1999. We determined hotspots based on the cumulative set of species listed for three overlapping and successively longer time periods: 1967–1979, 1967–1989, and 1967–1999. We used minimum area complimentarity analysis, which selected the smallest set of areas (in our study, U.S. counties) needed to represent a chosen set of species. Over time, the number of endangered and threatened species in the United States increased from 76 in 1967 to 1123 in 1999. As the number of species increased over time, hotspots changed in two ways: the number of hotspots increased and the rank of hotspots shifted. Hotspots increased from 84 in 1979, to 166 in 1989, to 217 in 1999. Only 63 of these counties were designated as hotspots in all three periods. The remaining changes resulted from addition and deletion of counties as hotspots over time. Some counties were removed from the list or changed in relative rank from one time period to the next regardless of their rank. Counties added as hotspots could rank anywhere on the list, and they were not merely low-ranking counties added to represent one or a few species. Therefore, hotspots serve as a useful tool for guiding conservation efforts but, given their spatiotemporal variability, do not represent a final solution.     

Do toxicity and accumulation of copper change during size reduction in the marine pennate diatom Haslea ostrearia?

 One of the best-known features of diatom biology is the reduction in mean cell size during vegetative multiplication by binary fission. We examined changes in copper toxicity and copper accumulation during cell-size reduction in Haslea ostrearia (Simonsen), a pennate diatom responsible for greening in oyster-ponds. We selected three strains with apical axes of different lengths: 40 μm (S40), 65 μm (S65) and 85 μm (S85). Each strain was grown separately in batch culture and exposed to a range of copper overloads (0 to 1.57 μM) that were added to the culture immediately after cell inoculation. Significant differences in sensitivity to copper were observed among the three strains. S85 exhibited highest sensitivity, followed by S40, while S65 displayed the highest tolerance. After 5 to 6 d exposure to 0.47 μM copper, chlorophyll a, carbohydrate, protein and lipid content per g dry weight had not changed in any of the three strains studied, except for a decrease of 16% in chlorophyll a in S85. At the end of the growth period with 0.47 μM copper, the amount of metal per unit surface area was similar for all strains, but the quantity of intracellular copper per g dry weight was lower in S65 cells than in S40 and S85 cells. Notable differences in the kinetics of both adsorbed and intracellular copper were observed between S40 and S85. Our results suggest that tolerance mechanisms may change during the vegetative life of H. ostrearia. The differential sensitivities of the strains suggest that copper pollution may alter the cell composition of natural populations of H. ostrearia by inducing selection for smaller cell size. Since auxosporulation results in the formation of larger cells with a higher sensitivity to copper, H. ostrearia could gradually disappear from copper-contaminated environments. In addition, by inducing smaller cell size, copper contamination would have an impact on filter-feeders such as oysters, whose diet is largely composed of diatoms. Received: 26 March 1999 / Accepted: 2 December 1999     

Molecular Systematics, Ethics, and Biological Decision Making under Uncertainty

Abstract: The controversy among Karl and Bowen (1999) , Pritchard (1999) , and Grady and Quattro (1999) over scientific uncertainties and the ethical and political consequences of the black turtle's taxonomic status is caused by incomplete and uncertain scientific knowledge. When faced with cases of uncertainty, conservation biologists need to use ethical rationality, not merely scientific rationality. They should follow three general ethical principles: (1) perform and present unbiased research, (2) promote use of unbiased research by others, and (3) protect human and environmental welfare. Adhering to these principles is difficult because they can conflict, are too general to provide specific guidance in a particular situation, and are not ranked according to which ought to take priority in different situations. One way to deal with these difficulties is to employ a two-stage ethical analysis. This analysis develops general principles (first stage) and then investigates the consequences of adopting each of the principles (second stage). A two-stage ethical analysis applied to the controversy over the black turtle's taxonomic status suggests that even if there are some grounds for expanding conservation biologists' responsibilities to human and environmental welfare, they are not ethically justified in using any means whatsoever to achieve desirable consequences when the public has rights to full information. Conservation biologists do not appear to have grounds for paternalism in this case because it involves value judgments, not merely professional expertise.     

Bycatch of Marine Mammals in U.S. and Global Fisheries

Abstract:  Fisheries bycatch poses a significant threat to many populations of marine mammals, but there are few published estimates of the magnitude of these catches. We estimated marine mammal bycatch in U.S. fisheries from 1990 to 1999 with data taken from the stock assessment reports required by the U.S. Marine Mammal Protection Act. The mean annual bycatch of marine mammals during this period was 6215 ± 448 (SE). Bycatch of cetaceans and pinnipeds occurred in similar numbers. Most cetacean (84%) and pinniped (98%) bycatch occurred in gill-net fisheries. Marine mammal bycatch declined significantly over the decade, primarily because of a reduction in the bycatch of cetaceans. Total marine mammal bycatch was significantly lower after the implementation of take reduction measures in the latter half of the decade. We derived a crude first estimate of marine mammal bycatch in the world's fisheries by expanding U.S. bycatch with data on fleet composition from the Food and Agriculture Organization. The global bycatch of marine mammals is in the hundreds of thousands. Bycatch is likely to have significant demographic effects on many populations of marine mammals. Better data are urgently needed to fully understand the impact of these interactions.     

Identification of the antifungal peptide-containing symbiont of the marine sponge Theonella swinhoei as a novel δ-proteobacterium, “Candidatus Entotheonella palauensis”

 The Palauan sponge Theonella swinhoei (class Demospongiae, order Lithistida, family Theonellidae) harbors filamentous bacterial symbionts that contain theopalauamide, an antifungal, bicyclic glycopeptide. In this study, the filamentous symbionts were shown to be novel bacteria belonging to the δ-subdivision of proteobacteria. The 16S rRNA gene sequence was determined using a combination of denaturing gradient-gel electrophoresis (DGGE) and specific polymerase chain-reaction (PCR) primers, and its source was confirmed by in situ hybridization. In a series of culture experiments, the filamentous bacteria were propagated in a mixed culture on agar plates. Related 16S rRNA gene sequences were isolated from related sponges with slightly different chemistry. The taxonomic status “Candidatus Entotheonella palauensis” is proposed for the theopalauamide-containing filamentous bacteria from T. swinhoei. Received: 12 June 1999 / Accepted: 22 January 2000     

Efficient waste and pollution abatements for regions in Japan

This paper computes efficient industrial waste and air pollutants abatements for 47 regions in Japan for the period 1992–2002. The variable-returns-to-scale (VRS) data envelopment analysis (DEA) with a single output (real GDP) and seven inputs (labor, real public capital stock, real private capital stock, industrial waste, sulfur oxide, nitrogen oxide, and soot and dust) is used to compute target wastes of each region for each year. The efficient abatement ratios of each region in each year are obtained by comparing the actual to the target amount of a pollutant. Our major findings are: (1) Most regions in Japan have significant room to reduce their pollution since there is a wide gap between efficient and inefficient regions; (2) For each air pollutant, approximately 25–33% of Japan's prefectures can reduce their output by more than 50% without harming regional GDP, and approximately one-third of prefectures can reduce industrial waste more than 30%; (3) Hokkaido is the least efficient region for all years studied and for all waste and pollutants, and target abatement ratios there drastically worsened in the last two sample years; (4) Tokyo, Saitama, Yamanashi, Shiga, Nara, and Tottori are efficient with respect to each type of industrial waste and pollution throughout the study period; (5) many regions in the bottom quartile with respect to real per capita income have significant room to reduce their waste and pollution output; and (6) many regions where energy-intensive industries dominate produce excessive amounts of waste and air pollution compared to other regions.     

Influences of Egg Laying Behavior on Pathogenic Infection of Amphibian Eggs

Mass mortality of developing amphibian eggs and larvae from pathogenic infection has been recently documented in some amphibian populations. For example, the pathogenic fungus, Saprolegnia ferax, has been linked with amphibian embryo mortality in the Pacific Northwest. Continued mortality in early life history stages may ultimately contribute to a population decline. We document the prevalence of S. ferax on embryos of three anuran species (   Bufo boreas, Rana cascadae, and Hyla regilla) common to the Pacific Northwest. These species differ in key aspects of their behavior and ecology, and these differences may lead to differential susceptibility to S. ferax. R. cascadae often lays its eggs communally and B. boreas usually deposits its eggs communally. We observed embryos at natural oviposition sites. Eggs laid communally had higher mortality than those laid away from other egg masses. Field experiments that manipulated both the spatial position and timing of egg laying demonstrated that eggs laid later and in closer proximity to communal masses had higher mortality. Our results suggest that eggs in communal masses are highly susceptible to infection with S. ferax.     

Biodiversity of marine sessile epifauna at an Aegean island subject to hydrothermal activity: Milos, eastern Mediterranean Sea

Sessile macroepifauna was sampled at six rocky sites between 2 and 90 m depth with a number of different methods involving both underwater photography and collection of specimens. A total of 212 species (or varieties) were identified, belonging to seven higher taxa: poriferans (24 species), cnidarians (32), molluscs (8), serpuloidean polychaetes (33), bryozoans (90), brachiopods (4) and ascidians (21). The combined use of a varied array of sampling methods was effective in obtaining a rich faunal inventory. Deep and offshore sites tended to be richer in species than shallow and inshore sites. In all cases species richness was higher at sites closest to hydrothermal vents on the sea floor. Although there are no comparable inventories of marine sessile epifauna in the Aegean, the high number of species found, with a relatively low sampling effort in a restricted area, indicates that the marine biodiversity of this sea is not as low as traditionally believed. Received: 20 January 1999 / Accepted: 25 August 1999     

Threat-sensitive feeding strategy of immature sticklebacks (Gasterosteus aculeatus) in response to recent experimental infection with the cestode Schistocephalus solidus

Threat-sensitive decision-making might be changed in response to a parasitic infection that impairs future reproduction. Infected animals should take more risk to gain energy to speed up their growth to achieve early reproduction and/or to strengthen their immune response. To avoid correlational evidence, we experimentally infected and sham-infected randomly selected immature three-spined sticklebacks with the cestode Schistocephalus solidus. For 7 weeks we determined the threat-sensitive foraging decisions and growth of individual sticklebacks in the presence of a live pike (Esox lucius). The experimenters were blind with respect to the infection status of the fish. In contrast to previous studies, our recently infected fish should have been almost unconstrained by the parasite and thus have been able to adopt an appropriate life history strategy. We found a strong predator effect for both infected and uninfected fish: the sticklebacks’ risk-sensitive foraging strategy resulted in significantly reduced growth under predation risk. Infected fish did not grow significantly faster under predation risk than uninfected fish. Since infected fish consumed much less prey in the presence of the predator than did infected fish in its absence, they obviously did not use the opportunity to maximize their growth rate to reach reproduction before the parasite impairs it. Received: 21 June 1999 / Revised: 27 November 1999 / Accepted: 5 September 2000     

Effect of nutrient enrichment on the complementary (secondary) metabolite composition of the soft coral Sarcophyton ehrenbergi (Cnidaria: Octocorallia: Alcyonaceae) of the Great Barrier Reef

 A long-term study of the effects of nutrient enrichment on coral reefs (ENCORE Experiment) was carried out at One Tree Island (23°30′S; 152°96′E), Great Barrier Reef, between 1992 and 1996. The experiment involved the addition of water-soluble nutrients to 12 microatolls which contained a range of organisms and were situated within the larger lagoon. Three replicates of each of three nutrient treatments (nitrogen, phosphorus, nitrogen plus phosphorus) and an untreated set of three control atolls were prepared using the 12 selected microatolls. As part of the larger ENCORE experiment, changes in the chemical composition of the alcyonacean soft coral Sarcophyton ehrenbergi Marenzeller (Octocorallia: Alcyonacea), placed in the treatment microatolls, were monitored for a 1 yr period in an attempt to detect any responses attributable to nutrient enrichment. Multivariate analyses were performed to determine whether there were any patterns of response in the different nutrient treatments. At the level of individual metabolites, there were no clear treatment effects. However, the ratio of bioactive or stress metabolites (terpenes) to energy storage metabolites (lipids), referred to as the “physiological-change indicator”, revealed effects of nutrient enrichment. Nitrogen enrichment resulted in a trend towards higher physiological-change indicators than control or phosphorus treatments in the majority of cases, while phosphorus enrichment significantly decreased the ratio relative to controls. In most cases, the physiological-change indicator increased in soft soft corals relocated into contact with the scleractinian Pocillopora damicornis. The potential of soft corals to serve as indicators of a changed nutrient regime is discussed. Received: 23 November 1998 / Accepted: 23 September 1999     

Storage and display of odour by male Saccopteryx bilineata (Chiroptera, Emballonuridae)

Males of the sac-winged bat, Saccopteryx bilineata, actively fill their propatagial sacs with secretions from the genital region, the gular gland, urine and saliva. From our observations and those of Starck we deduce that propatagial sacs in S. bilineata do not have a glandular function, but are instead organs for the storage and display of odours. In addition to the already known “salting” and hovering behaviour of male S. bilineata, we describe in detail how odour is fanned to roosting individuals during the complex, stereotypic hovering displays. S. bilineata males also coat the fur of their backs with saliva using the wing tip and might scent-mark territory boundaries. “Yawning” may represent a visual as well as an olfactory cue. Odour seems to play an important role in the social communication of S. bilineata and in other emballonurids, as revealed by the broad distribution of wing sacs in this family. S. bilineata males display odour during energetically costly hovering flights in front of females. We demonstrate that the number of hovering displays increases with harem size. The mating effort of S. bilineata males comprises a multimodal signalling behaviour. Although males defend harem territories in which females gather, females seem to be able to choose the father of their progeny freely among the males of a colony. This may have led to the evolution of the complex mating displays by male S. bilineata. Received: 9 December 1998 / Received in revised form: 6 May 1999 / Accepted: 13 June 1999