Bryophyte dispersal by flying foxes: a novel discovery

This research provides the first evidence of dispersal of bryophytes and associated microorganisms through ingestion by a highly mobile vertebrate vector, the spectacled flying fox (Pteropus conspicillatus). Bryophyte fragments were found in faeces collected at four P. conspicillatus’ camps in the Wet Tropics bioregion, northeastern Australia. These fragments were viable when grown in culture; live invertebrates and other organisms were also present. Our study has significantly increased understanding of the role of flying foxes as dispersal vectors in tropical forests.     

狐蝠对森林生态系统的作用

翼手目 (Chiroptera)为真正能飞翔的哺乳动物 ,现存 19科 110 7种 ,分别属于小蝙蝠亚目 (Microchiroptera)和大蝙蝠亚目 (Megachiroptera) ;其中大蝙蝠又称旧大陆狐蝠或果蝠 (flyingfox) ,分布在热带和亚热带地区 ,仅狐蝠科 188种 ,我国自然分布有 9种。部分地区因栖息地丧失和过度捕杀导致狐蝠种群数量全球性或地区性下降或灭绝 ;狐蝠通过传播种子或传粉 ,促进森林生态系统的更新和基因交流。因此 ,狐蝠对森林生态系统的稳定、扩散、生物多样性以及衰退森林的恢复有重要作用     

The role of temperature on clustering behavior and mating opportunity in Bonin flying foxes

Social thermoregulation is an important adaptation for animals living in cold environments, especially for those with high surface area-to-volume ratios. Huddling behavior can influence animal dispersion patterns. However, little attention has been paid to the relationship between huddling behavior and social organization, including mating systems. We studied aggregations of Bonin flying foxes Pteropus pselaphon on Chichijima Island in Japan, which is located at one of the northern limits of their geographical range. Bonin flying foxes aggregate in arboreal roosts, where they form temporary clusters within the colony during winter months. Specifically, we hypothesized that the occurrence and intensity of clustering behavior are affected by ambient temperature; therefore, we examined the relationship between cluster size and ambient temperature. We also investigated the age and sex compositions of clusters and mating behavior to gain insight into the mating system of this species. Field observations showed that P. pselaphon clusters were roughly separated into three groups: males, females, and subadults. Statistical analyses showed that ambient temperature had significant negative effects on the proportion of individuals that formed clusters for all groups. Cluster size decreased significantly with increasing ambient temperature in female and subadult groups. Some female clusters were composed of a single male and multiple females. Marked males were observed excluding other males from the periphery of female clusters, and they monopolized copulations with clustering females. Our findings suggest that clustering plays an important warming role in the species, and that this behavior is exploited by males resulting in a social system that is best described as a form of female-defense polygyny.     

Mating-associated peak in plasma testosterone concentration in wild male grey-headed flying foxes (Pteropus poliocephalus)

Plasma testosterone (T) concentrations, measured in wild bats of P. poliocephalus in Queensland in 1983-87, showed a peak during the mating season in March. Plasma androstenedione (A) concentrations changed less dramatically with season. Mean testicular concentration and total content of T and A was substantially greater in March than in regressed testes in July-October. Paired adrenal glands were heavier during February to April than during September to November. In the same wild population, throughout a single breeding season (1987), plasma T concentrations were significantly higher in mid-March than 3 weeks previously or 3 weeks later. Testicular T content rose as the breeding season progressed, being greatest during March, coinciding with the large rise in plasma T concentrations. Testicular T concentration and content were correlated significantly with plasma T concentrations. Adrenal glands contained T, but the absolute concentrations were much lower than in the testis. No significant changes in plasma, testicular or adrenal A concentrations were found as the breeding season progressed. The large increase in plasma T during the mating season appears to be due to increased testicular production.     

Thermoregulation and heterothermy in some of the smaller flying foxes (Megachiroptera) of New Guinea

Summary Body temperature, heterothermy, oxygen consumption, heart rate, and evaporative water loss were studied in four species of flying foxes (Megachiroptera), Dobsonia minor, Nyctimene major, Nyctimene albiventer, and Paranyctimene raptor, from the vicinity of Madang on the north coast of New Guinea.The thermoregulatory response of D. minor resembled that of most other placental mammals weighing 80 to 100 g. Body temperatures were relatively stable at ambient temperatures between 5 and 34°. The mean oxygen consumption at rest between 30 and 35° was 1.26 cc O₂ (g·hr)^–1. At ambient temperatures between 5 and 35° evaporative water loss averaged 4.5 mg (g·hr)^–1 and increased sharply at higher temperatures. When subjected to heat stress the animals panted, salivated, and licked the wings, belly, and uropatagium. At temperatures above 38° the ratio of heat lost through evaporation to heat production exceeded 1. Minimal heart rates in resting animals near thermal neutrality were approximately 275/min.In those parameters measured, N. major which weighed about 80 g resembled D. minor.Nyctimene albiventer and P. raptor weigh less than 30 g and are among the smallest of the flying foxes. Each shows both homeothermic and heterothermic patterns of response. At an ambient temperature of 35° the minimal oxygen consumption of homeothermic N. albiventer and P. raptor were 1.43 and 1.38 cc O₂ (g·hr)^–1, respectively. Oxygen consumption of homeothermic N. albiventer at 25°, 2.59 cc O₂ (g.hr)^–1, was almost quadruple that of torpid animals at the same temperature. During the daytime both N. albiventer and P. raptor characteristically allowed their body temperatures to fall to near 25°. Both readily aroused from the hypothermic state through physiological means. Heart rates of homeothermic N. albiventer resting at 35° ranged from 312 to 326/min while those of animals torpid at 25° were 88 to 96/min.The capacity for heterothermy has not previously been demonstrated in any members of the Megachiroptera, but our data indicate that it can occur on a daily basis in N. albiventer and P. raptor. This capacity appears to be related to size since it occurs in none of the larger flying foxes so far studied.The data presently available indicate that the relation of body weight to standard metabolism in the Megachiroptera is similar to that of the other placental mammals. In the species we studied, thermal conductances were higher, and heart rates, lower than predicted for mammals of their sizes.These studies were carried out during the 1969 Alpha Helix Expedition to New Guinea and were supported in part by grants GB-5139, GB-3656, and GB-8445 from the U. S. National Science Foundation.     

Evaluation of medetomidine/ketamine for short-term immobilization of variable flying foxes (Pteropus hypomelanus)

Four medetomidine/ketamine (M/K) doses (30 microg/kg/3 mg/kg; 40/4; 50/5; 60/6), administered by intramuscular injection, were evaluated for short-term immobilization of adult male variable flying foxes (Pteropus hypomelanus). The highest dose (60 microg/kg/6 mg/kg) produced a significantly faster induction (31 +/- 46 sec) than the lowest dose (30/3) (125 +/- 62 sec). The highest dose levels (50/5, 60/6) produced significantly longer immobilization times (52.5 +/- 25.7 min and 60.6 +/- 20.8 min, respectively) than did the lower doses (30/3, 40/4) (18.8 +/- 8.7 min and 31.0 +/- 14.3 min, respectively). The dose at which 50% of the bats were immobilized for > or = 30 min (ED(50)) was approximately 40 microg/kg/4 mg/kg. This dose produced a mean immobilization time of 31 +/- 14 min, bradypnea and bradycardia. In conclusion, a M/K dose of 50 microg/kg/5 mg/kg is recommended for greater than 30 min of relaxed immobilization in free-living variable flying foxes and is sufficient for safe collection of samples.     

Prevalence of antibodies against canine distemper virus among red foxes in Luxembourg

Canine distemper virus (CDV) has a wide host spectrum, and during the past years, distemper has been observed in species that were previously not considered to be susceptible. In this study, we investigated the prevalence of CDV-specific antibodies in red foxes (Vulpes vulpes) sampled between May and November 1997. About 9 to 13% of the Luxembourg red fox population is positive for antibodies against CDV. Thus a sizeable proportion of red foxes has been exposed to CDV in the wild. The significance of CDV in red foxes is discussed.     

Volatile compounds in shoulder gland secretions of male flying foxes, genus Pteropus (Pteropodidae, Chiroptera)

The shoulder gland secretions of captive males of the Indian flying fox (Pteropus giganteus), the little golden-mantled flying fox (P. pumilus), the island flying fox (P. hypomelanus), and the large flying fox (P. vampyrus) were examined by gas chromatography-mass spectrometry. Sixty-five compounds, including hydrocarbons, carboxylic acids, alcohols, aldehydes, ketones, esters, and amides, were identified among the four species. Many of these compounds, such as squalene, cholesterol, and C5-C16 straight- and branched-chain carboxylic acids, are typical of tetrapod epidermal products. Aldehydes, which were detected in all four Pteropus species, and some straight- and branched-chain ketones, which were detected in P. hypomelanus and P. pumilus, are known from other mammalian skin glands. Acetophenone, 4-acetoxyacetophenone, and 4-hydroxyacetophenone were observed in P. pumilus; the last compound comprised 37.1% of the total ion current. 2,3-Butanediol, a prominent component (5.2-19.3%) in the secretions of P. giganteus, P. hypomelanus, and P. pumilus, and C10 and C12 isopropyl esters and C10-C14 1-methylbutyl esters, observed in P. hypomelanus and P. vampyrus, have not previously been reported from vertebrates. alpha-Methyl-4-methoxybenzyl alcohol and dihydro-5-phenyl-2(3H)-furanone, from P. giganteus and P. pumilus, are new natural products. 1-Chloro-3-methyl-2-butene, another new natural product, and five C5 compounds exhibiting a similar isoprenoid structure were observed in P. giganteus. Striking contrasts were observed in the chemical profiles of the species we examined, with even general chemical classes differentially represented among them.     

Detection of Hepatocystis sp. in southeast Asian flying foxes (Pteropodidae) using microscopic and molecular methods

Three species of flying fox (Pteropus hypomelanus, P. vampyrus, and P. lylei) from Malaysia and Vietnam were screened for apicomplexan parasites by thin blood smears and polymerase chain reaction. Only 1 of 16 bats sampled from 3 localities in southeast Asia was found to be infected (P. hypomelanus from Pulau Pangkor, Malaysia). We observed micro- and macrogametocytes, with morphology consistent with Hepatocystis sp. parasites, using light microscopy. Phylogenetic analysis of the cytochrome b gene showed that the parasite from P. hypomelanus groups with 2 published sequences from Hepatocystis spp., including one from Cynopterus brachyotis, another fruit bat in the Pteropodidae.     

Structural modifications involved in the fore- and hind limb grip of some flying foxes (Chiroptera: Pteropodidae)

A mechanism which enables flying foxes to lock their hind limb digits and thumbs in flexion is described. The deep digital tendons of the hind limbs have roughened fibrocartilage surfaces. The adjacent flexor tendon sheath supports ridges which interact with the rough tendon surface, temporarily 'locking' the two structures together. This tendon locking mechanism is of importance as it enables bats to reduce the energetic cost of hanging from branches. It does this by reducing, or eliminating, the need for digital flexor muscle activity.     

Evolutionary relationships of flying foxes (genus Pteropus) in the Philippines inferred from DNA sequences of cytochrome b gene

Six flying fox species, genus Pteropus (four from the Philippines) were investigated using complete cytochrome b gene sequences (1140 bp) to infer their evolutionary relationships. The DNA sequences generated via polymerase chain reaction were analyzed using the neighbor-joining, parsimony, and maximum likelihood methods. We estimated that the first evolutionary event among these Pteropus species occurred approximately 13.90 ± 1.49 MYA. Within this short period of evolutionary time we further hypothesized that the ancestors of the flying foxes found in the Philippines experienced a subsequent diversification forming two clusters in the topology. The first cluster is composed of P. pumilus (Philippine endemic), P. speciosus (restricted in western Mindanao) with P. scapulatus, while the second one comprised P. vampyrus and P. dasymallus species based on the analysis from first and second codon positions. Consistently, all phylogenetic analyses divulged close association of P. dasymallus with P. vampyrus contradicting the previous report categorizing P. dasymallus under subniger species group with P. pumilus, P. speciosus, and P. hypomelanus. The Philippine endemic species (P. pumilus) is closely linked with P. speciosus. The representative samples of P. vampyrus showed a large genetic distance of 1.87%. The large genetic distance between P. dasymallus and P. hypomelanus, P. pumilus and P. speciosus denotes a distinct species group.     

Reproduction and nutritional stress are risk factors for Hendra virus infection in little red flying foxes (Pteropus scapulatus)

Hendra virus (HeV) is a lethal paramyxovirus which emerged in humans in 1994. Poor understanding of HeV dynamics in Pteropus spp. (flying fox or fruit bat) reservoir hosts has limited our ability to determine factors driving its emergence. We initiated a longitudinal field study of HeV in little red flying foxes (LRFF; Pteropus scapulatus) and examined individual and population risk factors for infection, to determine probable modes of intraspecific transmission. We also investigated whether seasonal changes in host behaviour, physiology and demography affect host-pathogen dynamics. Data showed that pregnant and lactating females had significantly higher risk of infection, which may explain previously observed temporal associations between HeV outbreaks and flying fox birthing periods. Age-specific seroprevalence curves generated from field data imply that HeV is transmitted horizontally via faeces, urine or saliva. Rapidly declining seroprevalence between two field seasons suggests that immunity wanes faster in LRFF than in other flying fox species, and highlights the potentially critical role of this species in interspecific viral persistence. The highest seroprevalence was observed when animals showed evidence of nutritional stress, suggesting that environmental processes that alter flying fox food sources, such as habitat loss and climate change, may increase HeV infection and transmission. These insights into the ecology of HeV in flying fox populations suggest causal links between anthropogenic environmental change and HeV emergence.     

Comparison of intravenous medetomidine and medetomidine/ketamine for immobilization of free-ranging variable flying foxes (Pteropus hypomelanus)

Medetomidine (0.03 mg/kg) and medetomidine/ketamine (0.05/5.0 and 0.025/2.5 mg/kg), administered by intravenous injection, were evaluated for short-term immobilization of wild-caught variable flying foxes (Pteropus hypomelanus). Medetomidine alone produced incomplete chemical restraint and a stressful, prolonged induction. Both ketamine/medetomidine doses produced a smooth induction and complete immobilization. The combined medetomidine/ketamine dose of 0.025/2.5 mg/kg produced a rapid induction (232±224 sec) with minimal struggling and vocalization, a complete and effective immobilization period, and tended to lead to a faster and better quality recovery than medetomidine alone or a higher dose of medetomidine and ketamine (0.05/5.0 mg/kg), thus reducing holding time and permitting an earlier release of the bat back into the wild.     

Catecholamine innervation of the intestine of flying foxes (Pteropus spp.): a substantial supply from enteric neurons

The distribution of catecholamines in the small and large intestine of flying foxes (Pteropus spp.) was investigated using glyoxylic-acid-induced fluorescence and immunohistochemical staining of tyrosine hydroxylase and dopamine--hydroxylase. Dense networks of varicose axons stained by each of these methods supplied blood vessels, the mucosa and both submucous and myenteric ganglia, but were scarce in the circular and longitudinal muscle. The majority (>90%) of submucous neuronal perikarya contained both enzymes and most of these also exhibited catecholamine fluorescence. Somata of similar staining characteristics were less common in the myenteric plexus, where single cells were found in only the minority of ganglia. All of the stained submucosal somata and mucosal axons contained vasoactive intestinal peptide, whereas catecholamine-containing axons that supplied the ganglia, external muscle and blood vessels did not. It is concluded that (1) there is dense catecholamine innervation of most tissues in the flyingfox intestine, similar to many other mammals, (2) mucosal axons originate from enteric catecholamine neurons, not found in other mammals, and (3) axons supplying the blood vessels and enteric ganglia are probably of sympathetic origin and can be distinguished from the intrinsic catecholamine-containing axons by their lack of vasoactive intestinal peptide. The roles and interactions of these two types of catecholamine innervation in the control of secretion and motility remain to be identified.     

Biological Effects of Leptospiral Lipids

Lipids were extracted from virulent Leptospira pomona and were purified. These lipids fixed complement in the presence of antiserum to L. pomona but did not stimulate the production of homologous agglutinins in rabbits, mice, or hamsters. When subsequently challenged, all of the mice and hamsters were fully susceptible to L. pomona. The lipid material was neither dermonecrotic nor lethal for mice or hamsters, but 382 mug of lipid from virulent or avirulent leptospires inhibited the growth of normal mice. Leptospiral lipids were toxic for peritoneal macrophages maintained in vitro, and when administered simultaneously with a million lethal doses of L. pomona, the lipids hastened death of the hamsters, presumably by inhibiting phagocytosis early in the course of the infection.     

Serological Investigations of Leptospiral Deoxyribonucleases

Enzymoserological comparison of a selection of leptospira strains tested with sera from rabbits immunized with unpurified DNase of Leptospira interrogans, serotype canicola, indicates the production of DNase of serologically very similar properties by the serotypes canicola, autumnalis, icterohemorrhagiae and pomona. The DNase produced by serotype hyos was serologically different from the others, while the serotypes grippotyphosa and bataviae did not produce DNases at all. The method used made it possible to differentiate between leptospiral DNase and normally occurring DNases in the serum samples. Neither leptospira DNase nor specific leptospira-DNase-antibodies could be detected in dog sera with high agglutinationlysis titres after natural infection.