Noctilio Albiventris Research Articles

Unusual aspects of inner cell mass formation, endoderm differentiation, Reichert's membrane development, and amniogenesis in the lesser bulldog bat, Noctilio albiventris

Background and Methods The early embryogenesis of the lesser bulldog bat, Noctilio albiventris (family Noctilionidae), was examined histologically in 59 pregnant females collected from a reproductively synchronized population in Colombia. Results Early blastocysts of Noctilio are unusual in lacking a typical inner cell mass. Instead, cells inside of the trophoblast are dispersed for a period as a monolayer. A typical inner cell mass (ICM) only forms and becomes properly oriented after the initiation of implantation. Several features of Reichert's membrane in this species are also noteworthy: it develops between the ICM and trophoblast and between the parietal endoderm and trophoblast; it becomes linked to a meshwork of basal laminalike material that extends into the ICM; and it appears to be continuous, or fused, with prominent basal laminae that develop within the cytotrophoblastic villi that radiate throughout the preplacenta. Amniogenesis occurs by cavitation and converts the ICM into a hollow epiblastic vesicle. Gastrulation commences before this vesicle exhibits obvious differentiation into an embryonic shield and amniotic ectoderm. Conclusions Because development and proper orientation of a typical ICM in Noctilio occur after the initiation of implantation, these may involve the migration of cells on the interior of the blastocyst and/or an unusual method of early endoderm differentiation. The possibility exists that epiblast, endoderm, and cytotrophoblast may all contribute to the secretion of Reichert's membrane in this bat. Although the early embryogenesis of Noctilio exhibits many similarities to that in phyllostomid bats, substantial differences also exist between these closely related species. © 1996 Wiley-Liss, Inc.

Complex sound analysis in the lesser bulldog bat: evidence for a mechanism for processing frequency elements of frequency modulated signals over restricted time intervals.

A stereotypical approach phase vocalization response of the lesser bulldog bat, Noctilio albiventris, to artificial echoes simulating a virtual approaching object was used to assess the ability of the bat to analyze and extract distance information from the artificial echoes. The performance of the bat was not significantly different when presented with naturally structured CF/FM echoes containing FM elements that sweep continuously from about 75-55 kHz in 4 ms or with CF/FM echoes containing FM components constructed from a series of 98 pure tone frequency steps, each with a duration of 0.04 ms. The performance of the bat remained unchanged when the duration of the tone steps was increased up to 0.08 ms but declined sharply to a level that was significantly below that seen with a naturally structured echo when the steps were 0.09 ms or longer. The performance of the bat depended on the duration of the individual tone steps, which could not exceed a specific upper limit of about 0.08 ms. The study suggests that the bats have adaptations for processing individual narrow band segments of FM signals over specific time intervals.

Energetic and Thermoregulatory Aspects of Clustering Behavior in the Neotropical Bat Noctilio albiventris

Communal roosting has been proposed as a mechanism for facilitating thermoregulation in bats. We examined the effects of cluster size on body temperature Tb and metabolism (measured as O₂ consumption, V̇o2) in Noctilio albiventris, a colonial insectivorous Neotropical bat with an adult body mass of 33-45 g. Measurements were made for group sizes of one, two, three, four, eight, and sixteen individuals at ambient temperatures Ta of 10°, 20°, and 30° C. At 30° C, V̇o2 is minimal (0.016 mL/[g · min]) and is not significantly affected by group size. At 10° and 20° C, V̇o2 is considerably higher than at 30° C, but it declines rapidly as group size increases from one to four. Increasing the group size beyond four individuals has little additional effect on V̇o2. By switching from solitary roosting to a cluster offour or more, individual bats can reduce their V̇o2 from 0.082 to 0.051 mL/(g min) at a Ta of 10°C (a 38% savings) and from 0.048 to 0.025 mL/(g · min) at a Ta of 20° C (a 47% savings). Mean body temperature was lowest for groups of four at all Ta's. At Ta's of 10° and 20° C there was more variance in Tb and a greater tendency for low Tb in groups of four or more than in smaller groups. The minimum Tb in groups of one to three was 32.3° C, but we measured Tb's as low as 27.4° C in larger groups. We conclude that clustering lowers the energy cost of roosting in N. albiventris because (1) heat loss rates are reduced in groups and (2) individuals in groups are more likely than solitary bats to further decrease metabolism by becoming hypothermic. Noctilio albiventris may be selected to avoid hypothermia when solitary because low Tb probably increases their vulnerability to predation (the minimum Tb for flight is 35° C). Presumably, risks of predation are lower for bats roosting in groups.

Animal Sonar: Processes and Performance

<i>Animal Sonar: Processes and Performance</i>

Temperature effects on metabolism, ventilation, and oxygen extraction in a neotropical bat

We examined the relationship between ambient temperature (Ta), body temperature (Tb), oxygen consumption (V̇ O 2 ), carbon dioxide production (V̇ CO 2 ), evaporative water loss (ṁH 2O), respiratory frequency (f), tidal volume (V t, minute volume (V̇ i), and oxygen extraction (E O 2 ) in the Neotropical bat Noctilio albiventris (mean mass 40 g). The factorial aerobic scope was 7.2 between Ta of 1–35°C ( V ̇ O 2 =0.119 and 0.0165 ml/( g· min), respectively ). The respiratory exchange ratio (V̇ CO 2 /V̇ O 2 ) did not change with T and ṁH 2O was constant between Ta of 10–35°C. Thermal conductance was minimal at 30°C and constant and low at Ta < 30° C. Between 10 and 35°C, Noctilio accomodated changing V̇ O 2 with parallel and roughly equivalent changes in f, V t, and E O 2 . The change in V̇ O 2 between 10 and 1 °C was accomodated mainly through changing f. Ventilation parameters in resting thermoneutral Noctilio are intermediate between allometric values for birds and mammals. Maximal E O 2 in Noctilio (35–40%) is higher than for other mammals but considerably less than maximal E O 2 in some birds.

Echolocation sound features processed to provide distance information in the CF/FM bat,Noctilio albiventris: evidence for a gated time window utilizing both CF and FM components

Bats of the speciesNoctilio albiventris, trained to discriminate differences in target distance, emitted pairs of pulses at a rate of 7–10/s, the first a constant frequency (CF) pulse of about 8 ms duration and 75 kHz frequency, followed after about 28 ms by a CF/FM pulse having a 6 ms, 75 kHz CF component that terminates in a 2 ms FM sweep to about 57 kHz.

Frequency tracking and Doppler shift compensation in response to an artificial CF/FM echolocation sound in the CF/FM bat,Noctilio albiventris

Bats of the speciesNoctilio albiventris emit short-constant frequency/frequency modulated (short-CF/FM) pulses with a CF component frequency at about 75 kHz. Bats sitting on a stationary platform were trained to discriminate target distance by means of echolocation. Loud, free-running artificial pulses, simulating the bat's natural CF/FM echolocation sounds or with systematic modifications in the frequency of the sounds, were presented to the bats during the discrimination trials. When the CF component of the artificial CF/FM sound was between 72 and 77 kHz, the bats shifted the frequency of the CF component of their own echolocation sounds toward that of the artificial pulse, tracking the frequency of the artificial CF component.

Discrimination performance and echolocation signal integration requirements for target detection and distance determination in the CF/FM bat,Noctilio albiventris

Bats of the speciesNoctilio albiventris were trained to detect the presence of a target or to discriminate differences in target distance by means of echolocation. During the discrimination trials, the bats emitted pairs of pulses at a rate of 7–10/s. The first was an 8 ms constant frequency (CF) signal at about 75 kHz. This was followed after about 28 ms by a short-constant frequency/ frequency modulated (short-CF/FM) signal composed of a 6 ms CF component at about 75 kHz terminating in a 2 ms FM component sweeping downward to about 57 kHz. There was no apparent difference in the pulse structure or emission pattern used for any of the tasks. The orientation sounds of bats flying in the laboratory and hunting prey under natural conditions follow the same general pattern but differ in interesting ways.

Reproductive failure due to the entrapment of oocytes in luteinized follicles of the little bulldog bat (Noctilio albiventris).

The reproductive tracts of 112 female little bulldog bats collected around the onset of a breeding season in the Cauca Valley of Colombia were examined histologically. Of the 88 females with luteinizing/luteinized follicles or new CL, 72 carried tubal ova or uterine blastocysts and 16 were non-pregnant. In 14 of the latter follicle rupture had apparently failed to occur, and the oocyte or a collapsed zona pellucida was found within a luteinizing or luteinized follicle. These structures appeared to be functional because most of the affected bats demonstrated preferential stimulation of the ipsilateral oviduct and/or uterine horn. Two of these animals also had a second, older luteinized follicle which contained the remnants of an oocyte. None of these 14 bats exhibited the uterine modifications thought to be associated with a previous pregnancy or had prominent mammary glands. Such reproductive features were, in contrast, frequently demonstrated by other females in the population. These observations suggest that the luteinization of unruptured follicles may have occurred in prepubertal members of the population and reflect immaturity of the hypothalamo-pituitary -ovarian axis in these individuals.

Echolocation, development, and vocal communication in the lesser bulldog bat, Noctilio albiventris

Foraging and echolocation behavior and its ontogeny in the lesser bulldog bat, Noctilio albiventris, were studied in Panama under field and captive conditions. The vocalizations utilized for echolocation and communication were monitored. Adult N. albiventris captured insect prey from the water surface employing various combinations of CF/FM (constant frequency and frequency modulated) signals. The proportions of CF/FM and the repetition rate were a function of the bat's activity. Most adults exhibited post-sunset and pre-dawn foraging activity, although several telemetered lactating females foraged for only the half hour after dusk, spending the rest of the night with their babies in the roost. When the juveniles began to leave the roost at the age of two months, they appeared to accompany their mothers on initial flights. Captive infant Noctilio developed slowly, and did not fly until about 5–6 weeks postnatally. They continued to nurse for almost 3 months, even though they were capable of eating solid food at about 6 weeks. Previous to weaning, mothers fed their infants with masticated food from their cheekpouches. At birth, Noctilio emit a combination of long FM isolation calls and shorter CF/FM pulses. Mothers nurse only their own babies which they appear to recognize by a vocal signature contained in the infants' isolation calls. The individual isolation calls, as well as the mother's communication sounds, appear to be variations of an FM sinusoidal wave. The periodicity and amplitude change, and different portions including harmonics are added or deleted. The short CF/FM signals of the infant evolve into the adult orientation type signals as the CF component increases in frequency and the repetition rate increases. These sounds appear to serve a dual function in communication and echolocation. Mother-young pairs were observed to call antiphonally, utilizing CF/short FM signals in retrieval situations. This duetting was also observed in bats flying over the Chagras River after the time the juveniles began to fly, and may function to maintain vocal contact during initial foraging flights.

Unilateral oviductal and uterine reactions in the little bulldog bat, Noctilio albiventris.

The reproductive tracts of 112 female Noctillio albiventris were collected around the time of a synchronized peak in conceptions in a wild population and examined histologically. The bats were generally found to be monovular. Ovulation could occur from either ovary with embryonic development taking place in the ipsilateral oviduct and uterine horn. Prior to the development of a mature follicle, the ampullary and isthmic secretory cells of 1 oviduct frequently contained more glycogen and exhibited greater cytoplasmic vacuolation than did those in comparable regions of the other oviduct. When a mature follicle, a newly ruptured follicle or a new corpus luteum (CL) was present, the more developed oviduct was consistently ipsilateral. Local dilation of just this oviduct with fluid was noted in a preovulatory and several recently postovulatory bats. With the exception of some mitotic activity in the uterine epithelium, little endometrial development was observed prior to ovulation and both uterine horns appeared similar in most preovulatory bats. However, higher glycogen levels were detected in the epithelium of the horn ipsilateral to the mature preovulatory follicle or newly ruptured follicle in 4 bats. During tubal passage of the embryo epithelial cell size and glycogen levels were often greater in the horn ipsilateral to the CL than in the contralateral horn. In some of these animalsstromal development also differed between the 2 horns. These observations suggest that an efficient, local pathway exists for ovarian stimulation of the ipsilateral oviduct and uterine horn in N. albiventris. The cranial end of each uterine horn, where the unilateral endometrial reactions were most pronounced, was found to be vascularized by a branch of the ipsilateral ovarian artery. This is consistent with the hypothesis that the unilateral effects may be attributable to a local countercurrent exchange of hormones between the ovarian venous and/or lymphatic drainage and the arterial supply of the ipsilateral oviduct and uterine horn. A direct effect of hormones diffusing out of the ovarian venous and/or lymphatic vessels upon arteries supplying these accessory organs also seems conceivable.

Preimplantation development, fate of the zona pellucida, and observations on the glycogen-rich oviduct of the little bulldog bat, Noctilio albiventris.

The reproductive biology of Noctilio albiventris was investigated histologically in 112 females collected at the start of their synchronized breeding season during two different sampling years in the Cauca Valley of Colombia. Both ovaries were functional, but the animals were generally observed to be monovular. Embryonic development in the oviduct was found to proceed to blastocyst formation and loss of the zona pellucida. In 22 animals the discarded zona had been left behind in the oviduct upon passage of the embryo into the uterus and was still undissolved at the time of amniogenesis, the latest stage examined. The zonae which had passed into the uterus with the embryos often exhibited signs of dissolution. Most of the early blastocyts were morphologically distinctive, lacking a typical inner cell mass and being instead largely bilaminar. Degenerating ova from previous ovulations were found in the oviducts of two pregnant bats, suggesting that Noctilio may be another species in which the embryo stimulates its own escape from the oviduct. During tubal passage of the embryo the secretory cells of the oviductal ampulla and isthmus exhibited a transient engorgement with glycogen, particularly on the side ipsilateral to the new corpus luteum.

Geographic Variation in the Lesser Noctilio, Noctilio albiventris (Chiroptera)

Based on the study of 537 specimens of the lesser noctilio, Noctilio alhiventris Desmarest, from throughout the geographic range of the species, four geographical areas of differentiation are here recognized. One comprises the region from Honduras southward to central Colombia and western Venezuela. There the bats are medium in size for the species and normally the brightest in color. For this taxon the appropriate name is Noctilio albiventris minor Osgood. The second area comprises the Upper Amazon Basin, the eastern versant of the Cordillera Oriental northward to the vicinity of Caracas, Venezuela, thence southward along the coast at least to Suriname. In this region the bats are the largest and darkest for the species. The valid name for this taxon appears to be Noctilio albiventris affinis D'Orbigny. The third area comprises the southern parts of Venezuela, Guyana and Suriname, the Lower Amazon Basin and the coastal areas of eastern Brazil as far as the Rio São Francisco. There the bats are the smallest of the species and usually dark in color, but in some individuals the venter is pale buff. For this taxon the earliest available name is Noctilio albiventris albiventris Desmarest. The fourth area comprises the drainage basin of the Río Paraná in southern Brazil, Paraguay, and Argentina. There the bats are again medium in size for the species and normally greyish brown above and buff to orange-buff below. This taxon appears to be without a name and herein is described as a new subspecies and named in honor of the late South American mammalogist Dr. Angel Cabrera LaTorre.