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PubMed2005

Embryonic staging system for the short-tailed fruit bat, Carollia perspicillata, a model organism for the mammalian order Chiroptera, based upon timed pregnancies in captive-bred animals.

There are approximately 4,800 extant species of mammals that exhibit tremendous morphological, physiological, and developmental diversity. Yet embryonic development has been studied in only a few mammalian species. Among mammals, bats are second only to rodents with regard to species number and habitat range and are the most abundant mammals in undisturbed tropical regions. Bat development, though, remains relatively unstudied. Here, we describe and illustrate a staging series of embryonic development for the short-tailed fruit bat, Carollia perspicillata, based on embryos collected at timed intervals after captive matings. As Carollia can be readily maintained and propagated in captivity and is extremely abundant in the wild, it offers an attractive choice as a chiropteran model organism. This staging system provides a framework for studying Carollia embryogenesis and should prove useful as a guide for embryological studies of other bat species and for comparisons with other orders of mammals.

Animals↗
PubMed1993

Pregnancy in chiroptera.

As with other aspects of their biology, bats exhibit considerable diversity in their reproductive characteristics. While early embryonic development in many species generally adheres to the pattern shown by more commonly studied eutherian mammals, others demonstrate advanced development in the oviduct (to the zona-free blastocyst stage) and a prolonged tubal journey of the embryo in a temporal sense. In some bats, the process for transporting ova through the oviducts can distinguish between living embryos and the remnants of dead ova. Implantation in bats is unusually diverse with respect to localization of the nidation sites (which in most species seem to be predetermined), orientation of the inner cell mass during implantation, depth of implantation, and trophoblastic invasiveness. Some species which can be bred in captivity would appear to be promising experimental models for studies of implantation because both this process and their endometrial biology in general exhibit many similarities to those of humans. Depending upon the species, bats develop either endotheliochorial or hemochorial placentas. Studies on black mastiff bats (Molossus ater) indicate that maternal endometrial endothelial cells probably play a very important morphogenetic role during placental development in this species. Similarities in placental structure suggest that this may also be the case in a number of other eutherian mammals.

Animals↗
PubMed2004

Baseline and stress-induced glucocorticoids during reproduction in the variable flying fox, Pteropus hypomelanus (Chiroptera: Pteropodidae).

Baseline and stress-responsive glucocorticoid (GC) levels were assessed during early pregnancy, late pregnancy, and lactation in female variable flying foxes (Pteropus hypomelanus) and in males over the same time period. Animals were maintained in a breeding colony in captivity. High levels of both cortisol and corticosterone were detected, with total plasma GC levels being among the highest documented in vertebrates (up to 3000 ng/ml in individual animals, with cortisol being the primary GC, accounting for approximately 78% of total GCs), and significantly greater in males than in females. Plasma levels of cortisol and corticosterone showed nearly identical profiles within each sex, with the exception of females in late pregnancy, in which corticosterone, but not cortisol, increased significantly. Baseline levels of plasma cortisol were highest in September (when pups were between 1 and 2 months of age) in both sexes, which may be related to the approaching onset of the mating period. There was a continuum in the magnitude of the response to stress (handling and sampling) over time in females, with the greatest stress response in early pregnancy, a dampened response during late pregnancy, and no significant stress response during lactation. Surprisingly, males failed to exhibit elevated GCs after this stress, but did have significant stress-induced hyperglycemia and suppression of plasma testosterone levels. This may be due to their high (perhaps maximal) baseline levels, which suggests that being in a breeding group was chronically stressful for males.

Analysis of Variance↗
PubMed1989

Ultrastructural changes in the seminiferous epithelium of two seasonally reproducing bats (Mammalia: Chiroptera).

The Sertoli cells of the Cape horseshoe bat (Rhinolophus capensis) and Schreiber's long-fingered bat (Miniopterus schreibersii) undergo marked changes in ultrastructure related to stages in the spermatogenic cycle. The amount of lipid stored in the Sertoli cells varies annually and is at a maximum from just after spermiation to early in the following spermatogenic cycle. During spermatogenesis, the diameter of the lipid droplets decreases, reaching a minimum prior to spermiation. Sertoli cells exhibit a marked apicobasal differentiation, particularly in the vicinity of developing late spermatids, where the cytoplasm of the Sertoli cell is packed with smooth endoplasmic reticulum. The possible roles of lipid droplets and smooth endoplasmic reticulum. The possible roles of lipid droplets and smooth endoplasmic reticulum in steroidogenesis by Sertoli cells are discussed. Junctional complexes occur between Sertoli cells and spermatogonia, are apparently absent from between Sertoli cells and spermatocytes, and are restricted to the region of the developing acrosome in the spermatids. Annulate lamellae, which occur commonly in the developing germinal cells and less frequently in the Sertoli cells, may be associated with the production of microtubules, which are present in both spermatids and Sertoli cells.

Animals↗
PubMed1993

Cephalometric correlates of echolocation in the chiroptera.

This study suggests that the evolution of head posture in bats is constrained by the demands of vocalization during echolocation. Nasal-emitting microchiropteran taxa are easily identified by their characteristic rotation of the basicranium ventrally about the cervical axis, the depression of the rostrum below the basicranial axis, and by the rotation of the lateral semicircular canals so as to maintain their horizontal orientation during flight. The converse is true for oral-emitting Microchiroptera. The general form of the microchiropteran skull has been canalized along two distinct evolutionary paths, respectively, towards oral-emitting or nasal-emitting forms.

Animals↗
PubMed1988

The acrosome reaction in spermatozoa of the grey-headed flying fox (Pteropus poliocephalus: Chiroptera) exposes barbed subacrosomal material.

Acrosome reactions were induced in seminal spermatozoa of the megachiropteran Pteropus poliocephalus, the grey-headed flying fox, using the ionophore A23187 (10 microM in Tyrodes solution with 1% w/v BSA). Samples were taken at 0, 10, and 120 minutes and fixed for electron microscopy. Initial motility of approximately 70% decreased to approximately 10% over 2 hours. The first motile spermatozoa without acrosomal caps were seen after 6 minutes, and by 90 minutes approximately 60% of motile spermatozoa had completed the acrosome reaction. The first sign of the reaction (by TEM) appears to be swelling and cavitation of the acrosomal matrix within the apical and principal segments, followed or possibly accompanied by fusion and fenestration of the outer acrosomal and plasma membranes and dispersion of the matrix except from the equatorial segment. The end-product of the reaction thus conforms to that seen in other eutherian mammals. However, the reaction exposes a uniquely moulded organization of subacrosomal material ("pseudoperforatorium"), shaped like an anvil over the rostral rim of the flattened nucleus and encased by the remaining inner acrosomal membrane. This has two "lateral" spikes on each side that extend approximately to the same width as the head in the region of the equatorial segment. While these barbs could serve to stabilize or anchor the apical segment of the acrosome, their exposure following the acrosome reaction suggests some specific mechanical role in penetration of the zona pellucida or in protecting more caudal structures from abrasive damage.

Acrosome↗
PubMed1988

Fine structure of the neck of epididymal spermatozoa of Schreiber's long-fingered bat (Chiroptera: Mammalia).

The structure of the spermatozoon of the long-fingered bat (Miniopterus schreibersii) was studied using transmission electron microscopy. The neck is characterized by two asymmetrically arranged features that allow the orientation of sections in different planes and therefore aid the interpretation of the structure. There are six segmented columns, two major and four minor, in the anterior 79% of the neck, and it is only posterior to this that the major columns split. One major column is associated with doublets 9, 1, and 2, and the other major column, with doublets 5 and 6. The proximal centriole is surrounded by the capitulum and segmented columns, and the distal centriole persists and is apparent in both longitudinal and transverse sections. The central pair of microtubules pass through the distal centriole and terminate at the proximal centriole. A line drawn through the two central microtubules divides the head into left and right halves. Development of the neck begins during early spermiogenesis at which time the two centrioles are associated with the production of the capitulum, segmented columns, and axoneme complex.

Animals↗
PubMed2001

Molecular systematics of the family Mormoopidae (Chiroptera) based on cytochrome b and recombination activating gene 2 sequences.

We examined 1140 bp of the mitochondrial cytochrome b gene and 1398 bp of the nuclear RAG2 gene to investigate the systematics of the eight species of bats within the family Mormoopidae. It was concluded that within the genus Pteronotus there were four valid subgenera: Phyllodia, Chilonycteris, Pteronotus, and an undescribed subgenus. Within Pteronotus, P. parnellii either was part of an unresolved tetratomy with the other three subgenera (cytochrome b data) or was basal (RAG2 and combined data). For three species, P. gymnonotus, P. macleayii, and P. quadridens, our sample revealed little geographic variation. In P. davyi and P. parnellii, the magnitude of genetic distance suggests the possibility of two biological species existing within the currently recognized taxa. Within P. personatus, there was substantial geographic variation partitioned in a step-like fashion among our specimens. Neither of the species within the genus Mormoops showed the deep distance nodes present in P. davyi, P. parnellii, and P. personatus. Cytochrome b and RAG2 data indicated that M. megalophylla evolved recently from its common ancestor. Although there was considerable agreement among the branching patterns for the nuclear and mitochondrial genes, both genes failed to provide robust data concerning the evolutionary relationships among the subgenera.

Animals↗
PubMed2004

Novel viral encephalitides associated with bats (Chiroptera)--host management strategies.

Several novel viruses recently described in bats of the genus Pteropus (sub-order Megachiroptera) in Australia and southeast Asia cause encephalitic disease in animals and humans. These viruses include Hendra virus and Nipah virus (genus Henipavirus, family Paramyxoviridae) and Australian bat lyssavirus (ABLV; genus Lyssavirus, family Rhabdoviridae). Broadly, strategies for disease prevention and control in the spillover host are directed at minimising direct or indirect contact with the natural host, improving farm-gate and on-farm biosecurity, and better disease recognition and diagnosis. Additional strategies for ABLV include the use of rabies vaccine for effective pre- and post-exposure prophylaxis in humans. Effective management strategies in the natural host are predicated on an understanding of the ecology of the disease in the natural host, and the identification and avoidance of factors putatively associated with emergence, such as habitat loss, land use change and demographic shifts. A possible future management strategy for ABLV in reservoir populations is immunisation using bait or plant-derived vaccination.

Animals↗
PubMed1988

Distribution and origin of vasoactive intestinal polypeptide (VIP)-immunoreactive, acetylcholinesterase-positive and adrenergic nerves of the cerebral arteries in the bent-winged bat (Mammalia: Chiroptera).

The overall distribution and origins of vasoactive intestinal polypeptide (VIP)-immunoreactive (IR), acetylcholinesterase (AChE)-positive and adrenergic nerves in the walls of the cerebral arteries were investigated in the bent-winged bat. VIP-IR and AChE-positive nerves innervating the bat cerebral vasculature appear to arise mainly from VIP-IR and AChE-positive cell bodies within microganglia found in the nerve bundle accompanying the sympathetic nerve bundle within the tympanic cavity. These microganglia, as well as the nerve bundle containing them, do not emit catecholamine fluorescence, suggesting that they are of the cranial parasympathetic outflow, probably the facial or glossopharyngeal one. The axons from VIP-IR and AChE-positive microganglia run intermingled with sympathetic adrenergic nerves in the same thick fiber bundles, and reach the cranial cavity through the carotid canal. In addition, some of the VIP-IR fibers innervating the vertebro-basilar system, at least the basilar artery, originate from VIP-IR nerve cells located in the wall of this artery. The supply of VIP-IR fibers to the bat major cerebral arteries is the richest among mammals in that it is much greater in the vertebro-basilar system than in the internal carotid system: plexuses of VIP-IR nerves are particularly dense along the walls from the posterior ramus to posterior cerebral and basilar arteries. Small pial and intracerebral arteries of the vertebro-basilar system, especially those of the posterior cerebral artery which supply most parts of the diencephalon and cerebrum, are also richly innervated by peripheral VIP-IR fibers. This pattern corresponds well with the innervation pattern of adrenergic and AChE-positive nerves.

Acetylcholinesterase↗
PubMed1996

The orientation behaviour of the lesser spearnosed bat, Phyllostomus discolor (Chiroptera) in a model roost. Concurrence of visual, echoacoustical and endogenous spatial information.

The orientation behaviour of bats (Phyllostomus discolor, Phyllostomidae), flying inside an octagonal "roost-like" chamber (phi: 100 cm; h: 150 cm) 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.

Animals↗
PubMed1989

The status of the corpus luteum during pregnancy in Miniopterus schreibersii (Chiroptera: Vespertilionidae) with emphasis on its role in developmental delay.

Developmental delay is correlated with torpor in the temperate zone bent-winged bat, Miniopterus schreibersii (latitude 37 degrees S) as a period of pre-implantation delay (delayed implantation) followed by a short post-implantation delay (delayed development). During this time, the number of steroidogenic organelles in luteal cytoplasm is greatly reduced compared with normal embryogenesis, and granular endoplasmic reticulum is prominent. Nidation, which occurs while the animals are hibernating, is not accompanied by marked changes in luteal ultrastructure, although the number of lipid droplets decreases somewhat. Progesterone rises slightly but not significantly; however, a pre-nidation decrease in high 17 beta-estradiol levels may play a role in implantation. Following implantation, the conceptus remains delayed at the blastocyst stage for several weeks. During this time the bats remain torpid and the only change in luteal cell ultrastructure is an increase in smooth endoplasmic reticulum as differentiation begins toward the trilaminar stage. At the end of developmental delay hypertrophy of the luteal cell begins and mitochondria and lipid droplets increase, markedly. By this time arousal from hibernation has occurred, placentation takes place and normal development is underway. At placentation, smooth endoplasmic reticulum reaches its maximum in luteal cytoplasm; estrogen and progesterone levels peak about 6 weeks later. For the remaining 2 months of gestation, signs of luteolysis appear. These observations suggest that the corpus luteum of developmental delay, though sub-optimally functional, is prolonged in its luteinization by the arrival of winter when the bats enter torpor. The capacity for maximal steroidogenesis is acquired at the end of winter, some weeks after implantation, when arousal occurs and normal development ensues.

Analysis of Variance↗
PubMed1990

Cellular composition and steroidogenic capacity of the ovary of Macrotus californicus (Chiroptera: Phyllostomatidae) during and after delayed embryonic development.

In the leaf-nosed bat, Macrotus californicus, a 4.5-month period of delayed early embryogenesis (October-March) precedes a 3.5-month period of normal embryogenesis (March-June). This prolonged gestation provides a unique opportunity to correlate ovarian changes with the events following implantation. The present study investigated luteal cell development and follicular biology during gestation. Circulating progesterone (P) levels following implantation were unchanged before transition to normal development, and were maximal at the start of active gestation. Luteal cell diameters increased during this period. Serum P levels declined prior to parturition, when cells staining positive for 3 beta-hydroxy-5-steroid dehydrogenase-5,4-isomerase (3 beta-HSD) activity were reduced in number and diameter, and enzyme staining was less intense in tissue slices. Subcellular steroidogenic organelles were present during delayed development, but smooth endoplasmic reticulum (SER) was markedly increased after the resumption of normal development at which time also luteal cells reacted positively to staining for 17 beta-HSD. Before parturition, lipid droplet accumulation and reduced SER suggested a reduction in steroid secretion. Large multilaminar follicles stained positive for 3 beta-HSD activity throughout gestation and for 17 beta-HSD except in late delayed development. Thus, the delay in embryogenesis may be due to an inadequately developed corpus luteum or to the steroidogenic activity of the multilaminar follicles.

17-Hydroxysteroid Dehydrogenases↗