Evidence for echolocation in the oldest known bats

The earliest-known bats are represented by excellent fossil material, including virtually complete skeletons of Icaronycteris index from the early Eocene (50 Myr BP) of western Wyoming and Palaeochiropteryx tupaiodon from the middle Eocene (45 Myr BP) 'Grube Messel' of western Germany. These taxa have been closely allied with Recent Microchiroptera, a suborder of diverse bats noted for their powers of ultrasonic echolocation. A problem with this relationship is the alleged absence in the Eocene forms of specializations in the auditory region and other aspects of the skeletal system. It has been proposed, therefore, that the oldest bats are members of a group more primitive and possibly ancestral to the Microchiroptera and the visually oriented Megachiroptera. Previously undescribed specimens now show, however, that Icaronycteris and Palaeochiropteryx share special basicranial features with microchiropterans which suggest comparable refinement of ultrasonic echolocation. These results support the theory that a sophisticated sonar system was present in the earliest records of microchiropteran history.     

No cost of echolocation for bats in flight

Echolocation has evolved in relatively few animal species. One constraint may be the high cost of producing pulses, the echoes of which can be detected over useful distances. The energy cost of echolocation in a small (6 g) insectivorous bat, when hanging at rest, was recently measured at 0.067 Joules per pulse, implying a mean cost for echolocation in flight of 9.5 x basal metabolic rate (range 7 to 12x). Because flight is very costly, whether the costs of echolocation and flying are additive is an important question. We measured the energy costs of flight in two species of small echolocating Microchiroptera using a novel combination of respirometry and doubly-labelled water. Flight energy expenditure (adjusted for body mass) was not significantly different between echolocating bats and non-echolocating bats and birds. The low cost of echolocation for flying vertebrates may have been a significant factor favouring its evolution in these groups.     

Biomechanics: independent evolution of running in vampire bats

Most tetrapods have retained terrestrial locomotion since it evolved in the Palaeozoic era, but bats have become so specialized for flight that they have almost lost the ability to manoeuvre on land at all. Vampire bats, which sneak up on their prey along the ground, are an important exception. Here we show that common vampire bats can also run by using a unique bounding gait, in which the forelimbs instead of the hindlimbs are recruited for force production as the wings are much more powerful than the legs. This ability to run seems to have evolved independently within the bat lineage.     

Mate fidelity and intra-lineage polygyny in greater horseshoe bats

Mating strategies that lead to increased kinship within socially cooperative groups may offer inclusive fitness benefits to individuals, but can also result in higher levels of inbreeding. Here we show in a sexually segregated bat species that females avoid this conflict through two mating behaviours. First, most females revisit and breed with specific, individual males across years, so that their single offspring born in different years are full siblings. Second, relatives in the maternal line, including mothers and daughters, share breeding partners (intra-lineage polygyny) more often than expected by chance. Although these behaviours increased levels of co-ancestry among colony members, there was no concomitant rise in inbreeding. We suggest that when females engage in mate fidelity and intra-lineage polygyny, kin ties among female roost mates will be strengthened, thereby potentially contributing to social group cohesiveness. Our findings reveal the hidden complexity that can underlie polygynous breeding, and highlight a new potential route by which female mate choice could influence social evolution.     

Fruit bats as reservoirs of Ebola virus

The first recorded human outbreak of Ebola virus was in 1976, but the wild reservoir of this virus is still unknown. Here we test for Ebola in more than a thousand small vertebrates that were collected during Ebola outbreaks in humans and great apes between 2001 and 2003 in Gabon and the Republic of the Congo. We find evidence of asymptomatic infection by Ebola virus in three species of fruit bat, indicating that these animals may be acting as a reservoir for this deadly virus.     

中国蝙蝠核型研究的现状

对中国蝙蝠核型研究的现状进行了分析和研究,在已发表的22篇研究论文中,报道了39种蝙蝠的核型,中国尚有约60％以上的蝙蝠种类未进行核型分析．针对已发表研究论文中存在部分种类鉴定有误、图表欠准确合理和研究方法待改进等问题,提出了改进研究方法等建议,对提高我国蝙蝠研究水平和核型研究论文的质量有较重要的意义。     

Grid cells without theta oscillations in the entorhinal cortex of bats

Grid cells provide a neural representation of space, by discharging when an animal traverses through the vertices of a periodic hexagonal grid spanning the environment. Although grid cells have been characterized in detail in rats, the fundamental question of what neural dynamics give rise to the grid structure remains unresolved. Two competing classes of models were proposed: network models, based on attractor dynamics, and oscillatory interference models, which propose that interference between somatic and dendritic theta-band oscillations (4-10?Hz) in single neurons transforms a temporal oscillation into a spatially periodic grid. So far, these models could not be dissociated experimentally, because rodent grid cells always co-exist with continuous theta oscillations. Here we used a novel animal model, the Egyptian fruit bat, to refute the proposed causal link between grids and theta oscillations. On the basis of our previous finding from bat hippocampus, of spatially tuned place cells in the absence of continuous theta oscillations, we hypothesized that grid cells in bat medial entorhinal cortex might also exist without theta oscillations. Indeed, we found grid cells in bat medial entorhinal cortex that shared remarkable similarities to rodent grid cells. Notably, the grids existed in the absence of continuous theta-band oscillations, and with almost no theta modulation of grid-cell spiking--both of which are essential prerequisites of the oscillatory interference models. Our results provide a direct demonstration of grid cells in a non-rodent species. Furthermore, they strongly argue against a major class of computational models of grid cells.     

Vocalization during copulation behavior in greater horseshoe bats, Rhinolophus ferrumequinum

Vocal communication plays an important role for individual recognition and male-female interaction during mating in greater horseshoe bats,especially in respect to mate fidelity,which ensures that the bats can maintain a stable social organization.Few studies,however,have addressed the calling behavior during copulating in bats.Here,we initially report the copulation vocalizations and behaviors of both male and female greater horseshoe bats.During copulation,the male assumed a dorsal position and arched his back,arming around the female using his feet and thumbs.The male repeatedly produced very short constant frequency(SCF) syllables with high intensity and repetition rate(male 1:16.48±4.8 ms,male 2:17.79±4.03 ms) when he tried to insert the penis into the female,and then long syllables(male 1:42.08±12.67 ms,male 2:43.02±11.44 ms) after penile insertion.The female bats sometime refused the male bats in the early phase of copulations as emitting noise bursts and broad-band vocalizations,but kept silence during actual copulation.We also found that the SCF copulation calls of one male remained stable peak frequencies on different copulation days although its echolocation call frequency varied each day.Moreover,different male individuals maintained their own "private frequency" in the SCF copulation calls.Therefore,we predicted that the SCF copulation calls may serve as an indicator for female greater horseshoe bats to recognize the mating males in order to maintain mate fidelity because horseshoe bats exhibit sexual segregation before mating.Our results stipulate further studies on mating system and copulation strategies in polygynous bats.Such work may also aid in promoting the preservation of greater horseshoe bats.     

A possible neuronal basis for Doppler-shift compensation in echo-locating horseshoe bats

The auditory system of the horseshoe bat is finely tuned to the bat's individual vocalization frequency. To compensate for flight-induced Doppler shifts in the echo frequency, the horseshoe bat adjusts the frequency of its echo-location call to maintain the echo frequency within the narrow range to which its auditory system is best tuned. In this report I describe neurons in the midbrain tegmentum of the horseshoe bat, with properties that strongly indicate their involvement in this Doppler-shift compensation. The activity of these neurons was influenced by both sound emission and auditory stimuli. Neuronal discharges in response to vocalization, however, differed from those in response to purely auditory stimuli that mimicked the bat call. When an auditory stimulus was temporally locked to a preceding vocalization, the response was dependent on the time delay between the two. This delay-sensitivity completely disappeared when vocalizations were simulated acoustically. Only those vocalization and 'echo' parameters were encoded that occur in Doppler-shift compensation. In conclusion, I suggest a model for the regulation of the vocalization frequency through auditory feedback.     

Molecular evidence regarding the origin of echolocation and flight in bats

Bats (order Chiroptera) are one of the few orders of mammals that echolocate and the only group with the capacity for powered flight. The order is subdivided into Microchiroptera and Megachiroptera, with an array of characteristics defining each group, including complex laryngeal echolocation systems in microbats and enhanced visual acuity in megabats. The respective monophylies of the two suborders have been tacitly assumed, although microbat monophyly is uncorroborated by molecular data. Here we present a phylogenetic analysis of bat relationships using DNA sequence data from four nuclear genes and three mitochondrial genes (total of 8,230 base pairs), indicating that microbat families in the superfamily Rhinolophoidea are more closely related to megabats than they are to other microbats. This implies that echolocation systems either evolved independently in rhinolophoids and other microbats or were lost in the evolution of megabats. Our data also reject flying lemur (order Dermoptera) as the bat sister group, indicating that presumed shared derived characters for flying lemurs and bats are convergent features that evolved in association with gliding and flight, respectively.     

我国蝙蝠保护研究现状及对策

蝙蝠是世界上分布最广、进化最成功的哺乳动物类群之一,它们在生态系统中具有重要作用。对于节肢动物而言,它们是捕食者;对于某些脊椎动物而言,它们是被捕食者;而且它们还是种子的传播者和花粉的传授者。在一定生态系统是蝙蝠可能起到关键种的作用。我国对蝙蝠的研究与保护现状令人担忧。文中提出了5项主要研究和保护对策：种类编目;栖息地周围自然环境的保护;觅食地以见觅食路线的保护;冬眠区的保护;通过立法和宣传教育促进社全社会对蝙蝠进行保护。