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PubMed2000

A molecular analysis of ground sloth diet through the last glaciation.

DNA was extracted from five coprolites, excavated in Gypsum Cave, Nevada and radiocarbon dated to approximately 11 000, 20 000 and 28 500 years BP. All coprolites contained mitochondrial DNA sequences identical to a DNA sequence determined from a bone of the extinct ground sloth Nothrotheriops shastensis. A 157-bp fragment of the chloroplast gene for the large subunit of the ribulosebisphosphate carboxylase (rbcL) was amplified from the boluses and several hundred clones were sequenced. In addition, the same DNA fragment was sequenced from 99 plant species that occur in the vicinity of Gypsum Cave today. When these were compared to the DNA sequences in GenBank, 69 were correctly (two incorrectly) assigned to taxonomic orders. The plant sequences from the five coprolites as well as from one previously studied coprolite were compared to rbcL sequences in GenBank and the contemporary plant species. Thirteen families or orders of plants that formed part of the diet of the Shasta ground sloth could be identified, showing that the ground sloth was feeding on trees as well as herbs and grasses. The plants in the boluses further indicate that the climate 11 000 years BP was dryer than 20 000 and 28 500 years BP. However, the sloths seem to have visited water sources more frequently at 11 000 BP than at earlier times.

Animals↗

PubMed2005

Asynchronous extinction of late Quaternary sloths on continents and islands.

Whatever the cause, it is extraordinary that dozens of genera of large mammals became extinct during the late Quaternary throughout the Western Hemisphere, including 90% of the genera of the xenarthran suborder Phyllophaga (sloths). Radiocarbon dates directly on dung, bones, or other tissue of extinct sloths place their "last appearance" datum at approximately 11,000 radiocarbon years before present (yr BP) or slightly less in North America, approximately 10,500 yr BP in South America, and approximately 4,400 yr BP on West Indian islands. This asynchronous situation is not compatible with glacial-interglacial climate change forcing these extinctions, especially given the great elevational, latitudinal, and longitudinal variation of the sloth-bearing continental sites. Instead, the chronology of last appearance of extinct sloths, whether on continents or islands, more closely tracks the first arrival of people.

Animals↗

PubMed2001

Sloth biology: an update on their physiological ecology, behavior and role as vectors of arthropods and arboviruses.

This is a review of the research undertaken since 1971 on the behavior and physiological ecology of sloths. The animals exhibit numerous fascinating features. Sloth hair is extremely specialized for a wet tropical environment and contains symbiotic algae. Activity shows circadian and seasonal variation. Nutrients derived from the food, particularly in Bradypus, only barely match the requirements for energy expenditure. Sloths are hosts to a fascinating array of commensal and parasitic arthropods and are carriers of various arthropod-borne viruses. Sloths are known reservoirs of the flagellate protozoan which causes leishmaniasis in humans, and may also carry trypanosomes and the protozoan Pneumocystis carinii.

Animal Nutritional Physiological Phenomena↗

PubMed1983

Viruses isolated from Panamanian sloths.

Seven virus strains were isolated in Vero cells from whole blood samples from 80 wild-caught sloths, Bradypus variegatus and Choloepus hoffmanni, from Central Panamá. Four strains of at least two different serotypes are related to Changuinola virus; two of these were associated with prolonged or recrudescent viremias. One strain is an antigenic subtype of Punta Toro virus, and another, described here as Bradypus-4 virus, is a new, antigenically ungrouped virus. A second new virus from sloths, Utive virus, forms an antigenic complex within the Simbu serogroup with Utinga and Pintupo viruses. Tests on sequential plasma samples from radio-marked free-ranging sloths and from recently captured animals maintained in captivity showed that both species develop neutralizing antibodies following naturally acquired virus infections. Antibodies against the Changuinola and Simbu serogroup viruses are widespread in both sloth species and are especially prevalent in Choloepus, but are virtually absent in all other wild vertebrate species tested.

Animals↗

PubMed1998

Comparison of injectable anesthetic combinations in free-ranging two-toed sloths in French guiana.

Immobilization was studied in 202 free-ranging two-toed sloths (Choloepus didactylus). All the sloths were in good condition with a body weight > 2 kg, and were anesthetized for a variety of minor clinical procedures. Intramuscular anesthetic combinations included 0.1 mg/kg acepromazine + 10 mg/kg ketamine (A/K, n = 30), 1 mg/kg xylazine + 10 mg/kg ketamine (X/K, n = 89), 10 mg/kg tiletamine/zolazepam (T/Z, n = 37), and 0.04 mg/kg medetomidine + 3 mg/kg ketamine (M/K, n = 46) antagonized by 0.2 mg/kg atipamezole. The animals were quiet during the induction stage and complete recumbency was reached in (mean +/- SD) 2.5 +/- 2.0 min with A/K, 2.7 +/- 1.7 min with X/K, 1.8 +/- 0.6 min with T/Z, and 2.5 +/- 5 with M/K. Utilization of A/K was not satisfactory because of poor anesthetic level and lack of muscle relaxation. T/Z induced immobilization was characterized by deep anesthesia and good myorelaxation, but often was associated with irregular respiration and low relative oxyhemoglobin saturation values (SpO2). Ketamine in combination with alpha2-agonists, xylazine or medetomidine, provided suitable anesthesia, with good to excellent muscular relaxation, good analgesia, high SpO2 values, moderate bradycardia, but strong bradypnea with medetomidine. Anesthesia with M/K was reversed after 41.6 min of immobilization with atipamezole. Calm recoveries were obtained and the animals were able to hang up after 10.0 +/- 7.9 min. The first signs of arousal were observed within an average of 43 to 51 min after the injection of the three other combinations. Recoveries from X/K immobilization were quiet; sloths held on after 34 min. With T/Z, recovery duration was long and very irregular at 76.7 +/- 31.3 min, some animals required 3 hr before being able to hang up. Finally, ketamine in association with an alpha2-agonist appeared to give the best chemical immobilization in wild two-toed sloths for 40 min procedures including minor surgery.

Acepromazine↗

PubMed1999

Hematological and serum chemistry profiles of free-ranging southern two-toed sloths in French Guiana.

Free-ranging southern two-toed sloths (Choloepus didactylus) were translocated during the flooding of a forest at a hydroelectric dam site in French Guiana. Over an 11 mo period blood samples were collected from 90 sloths (38 males, 52 females) in order to determine hematological and serum chemistry reference values. Mean values and range of values were calculated for 13 hematological and 21 serum chemistry parameters. Variations associated with sex, age and reproductive status were identified. Males had a significantly lower red blood cell count than females. Immature animals had more monocytes while adults had more neutrophils and higher mean corpuscular hemoglobin concentration. Aspartate aminotransferase and triglyceride values were higher in young than in adult sloths but uric acid was lower. Lactating females showed lower red blood cells count and iron levels than non-lactating females. These profiles will help to provide reliable baseline data for medical evaluation of sloths.

Animals↗

PubMed1986

Morphology of hair of two- and three- toed sloths (Edentata: Bradypodidae).

Micromorphological differences between hairs of the two-toed sloth (Choloepus hoffmanni) and of the three-toed sloth (Bradypus variegatus) were observed by means of scanning electron microscopy. Hairs of the two-toed had longitudinal grooves which exposed a uniform cortex when viewed in cross section. Hairs of the three-toed sloth have irregular transverse fissures and a cortex that contains scattered fusi. These morphological differences support the placement of the two sloth genera into separate families. Hairs of four other xenarthran species are also illustrated.

Animals↗

PubMed1987

Unusual distribution of ganglion cells in the retina of the three-toed sloth (Bradypus variegatus).

1. The distribution and size of retinal ganglion cells labelled with horseradish peroxidase (HRP) were studied in flat-mounted retinas of three-toed sloths. 2. Massive injections of HRP solution were made throughout the thalamus and midbrain in anesthetized sloths in order to retrogradely label the retinal ganglion cell population. Twenty to thirty h later the eyes were excised and the retinas flat-mounted and reacted with phenylenediamine-HCl and H2O2 to label ganglion cells, thus distinguishing them from other cells in the same retinal layer. 3. Ganglion cell density gradually increased from about 500 cells/mm2 at the far periphery to a peak of about 1,500 cells/mm2 in an area, termed the area centralis, deep in the inferior temporal retina. The presence of a vertical visual streak was also noted. 4. The area centralis contained a higher frequency of small ganglion cells than the peripheral retina where large cells predominated. 5. The unusual position of the area centralis and visual streak in the retina can be explained by the sloth's unique ability to rotate its head 180 degrees while climbing upside-down along horizontal branches so that the head is right-side-up. If it is assumed that the branch directly above the sloth's head needs to be visualized for accurate claw placement then the branch would be imaged on the inferior temporal retina in an area corresponding to the maximum density region.

Animals↗

PubMed1997

Phalangeal curvature and positional behavior in extinct sloth lemurs (Primates, Palaeopropithecidae).

Recent paleontological discoveries in Madagascar document the existence of a diverse clade of palaeopropithecids or "sloth lemurs": Mesopropithecus (three species), Babakotia (one species), Palaeopropithecus (three species), and Archaeoindris (one species). This mini-radiation of now extinct ("subfossil") lemurs is most closely related to the living indrids (Indri, Propithecus, and Avahi). Whereas the extant indrids are known for their leaping acrobatics, the palaeopropithecids (except perhaps for the poorly known giant Archaeoindris) exhibit numerous skeletal design features for antipronograde or suspensory positional behaviors (e.g., high intermembral indices and mobile joints). Here we analyze the curvature of the proximal phalanges of the hands and feet. Computed as the included angle (theta), phalangeal curvature develops in response to mechanical use and is known to be correlated in primates with hand and foot function in different habitats; terrestrial species have straighter phalanges than their arboreal counterparts, and highly suspensory forms such as the orangutan possess the most curved phalanges. Sloth lemurs as a group are characterized by very curved proximal phalanges, exceeding those seen in spider monkeys and siamangs, and approaching that of orangutans. Indrids have curvatures roughly half that of sloth lemurs, and the more terrestrial, subfossil Archaeolemur possesses the least curved phalanges of all the indroids. Taken together with many other derived aspects of their postcranial anatomy, phalangeal curvature indicates that the sloth lemurs are one of the most suspensory clades of mammals ever to evolve.

Journal Article↗

PubMed2001

The evolution of armadillos, anteaters and sloths depicted by nuclear and mitochondrial phylogenies: implications for the status of the enigmatic fossil Eurotamandua.

The mammalian order Xenarthra (armadillos, anteaters and sloths) is one of the four major clades of placentals, but it remains poorly studied from the molecular phylogenetics perspective. We present here a study encompassing most of the order's diversity in order to establish xenarthrans' intra-ordinal relationships, discuss the evolution of their morphological characters, search for their extant sister group and specify the timing of their radiation with special emphasis on the status of the controversial fossil Eurotamandua. Sequences of three genes (nuclear exon 28 of the Von Willebrand factor and mitochondrial 12S and 16S rRNAs) are compared for eight of the 13 living genera. Phylogenetic analyses confirm the order's monophyly and that of its three major lineages: armadillos (Cingulata), anteaters (Vermilingua) and sloths ('Tardigrada', renamed in 'Folivora'), and our results strongly support the grouping of hairy xenarthrans (anteaters and sloths) into Pilosa. Within placentals, Afrotheria might be the first lineage to branch off, followed by Xenarthra. The morphological adaptative convergence between New World xenarthrans and Old World pangolins is confirmed. Molecular datings place the early emergence of armadillos around the Cretaceous/Tertiary boundary, followed by the divergence between anteaters and sloths in the Early Eocene era. These Tertiary dates contradict the concept of a very ancient origin of modern xenarthran lineages. They also question the placement of the purported fossil anteater (Eurotamandua) from the Middle Eocene period of Europe with the Vermilingua and instead suggest the independent and convergent evolution of this enigmatic taxon.

Animals↗

PubMed2003

Nuclear gene sequences from a late pleistocene sloth coprolite.

The determination of nuclear DNA sequences from ancient remains would open many novel opportunities such as the resolution of phylogenies, the sexing of hominid and animal remains, and the characterization of genes involved in phenotypic traits. However, to date, single-copy nuclear DNA sequences from fossils have been determined only from bones and teeth of woolly mammoths preserved in the permafrost. Since the best preserved ancient nucleic acids tend to stem from cold environments, this has led to the assumption that nuclear DNA would be retrievable only from frozen remains. We have previously shown that Pleistocene coprolites stemming from the extinct Shasta sloth (Nothrotheriops shastensis, Megatheriidae) contain mitochondrial (mt) DNA from the animal that produced them as well as chloroplast (cp) DNA from the ingested plants. Recent attempts to resolve the phylogeny of two families of extinct sloths by using strictly mitochondrial DNA has been inconclusive. We have prepared DNA extracts from a ground sloth coprolite from Gypsum Cave, Nevada, and quantitated the number of mtDNA copies for three different fragment lengths by using real-time PCR. We amplified one multicopy and three single-copy nuclear gene fragments and used the concatenated sequence to resolve the phylogeny. These results show that ancient single-copy nuclear DNA can be recovered from warm, arid climates. Thus, nuclear DNA preservation is not restricted to cold climates.

Animals↗

PubMed1998

Molecular coproscopy: dung and diet of the extinct ground sloth Nothrotheriops shastensis.

DNA from excrements can be amplified by means of the polymerase chain reaction. However, this has not been possible with ancient feces. Cross-links between reducing sugars and amino groups were shown to exist in a Pleistocene coprolite from Gypsum Cave, Nevada. A chemical agent, N-phenacylthiazolium bromide, that cleaves such cross-links made it possible to amplify DNA sequences. Analyses of these DNA sequences showed that the coprolite is derived from an extinct sloth, presumably the Shasta ground sloth Nothrotheriops shastensis. Plant DNA sequences from seven groups of plants were identified in the coprolite. The plant assemblage that formed part of the sloth's diet exists today at elevations about 800 meters higher than the cave.

Animals↗

PubMed1979

Glucose metabolism by isolated fat cells from sloth.

Glucose metabolism by sloth fat cells with and without addition of insulin was investigated. The data were compared to the results obtained with rat fat cells incubated under the same experimental conditions. Sloth fat cells showed a very low glucose oxidation to 14CO2 and incorporation into total lipids. The glucose incorporated into lipids is mainly in the glyceride-glycerol moiety. Addition of insulin did not produce an increase on glucose oxidation and a slight increase in the incorporation into total lipids was observed. Since it has been reported that sloths have a very low rate on thyroxine secretion, the results are discussed in relation to data in the literature on carbohydrate and lipid metabolism in hypothyroid animals.

Adipose Tissue↗

PubMed1978

Dirofilaria macrodemos and D. panamensis spp. n. (Nematoda: Filarioidea) from Central and South Americal sloths.

Two new species of Diorfilaria, Dirofilaria macrodemos and Dirofilaria panamensis, are described from the subserosa of Central and South American sloths. Dirofilaria macrodemos, described from the three-toed sloth, Bradypus tridactylus, in Guyana, is characterized and differentiated from other dirofilarias by its length (female 214mm, male 64mm), relatively long tail (female 140 micron, male 110 micron), and the number and distribution of the caudal papillae (7 pairs) in the male. Dirofilaria panamensis, parasite of the two-toed sloth, Cholopeus hoffmanni, in Panama, was previously described as Dirofilaria incrassata by Caballero (1947), but can be distinguished from both D. macrodemos and D. incrassata on the basis of body size (female 66 mm long by 360 micron wide, male 34 mm long by 250 micron wide), tail length (female 80 micron, male 80 micron), and number (6 pairs) of caudal papillae in the male.

Animals↗

PubMed1969

Leishmania braziliensis isolated from sloths in Panama.

Two edentates, the twotoed sloth Choloepus hoffmanni and the three-toed sloth Bradypus infuscatus, infected with Leishmania were found in Panama. The rates of infection were 14.1 and 1.3 percent in Choloepus and Bradypus, respectively. Leishmania braziliensis sensu lato was cultured from skin, blood, spleen, liver, or bone marrow of 13 sloths often from two or more tissues from the same animal. This strain is indistinguishable from Leishmania strains isolated from hunmanis in Panama.

Animals↗

PubMed1982

The fine structure of the placental labyrinth in the sloth, Bradypus tridactylus.

The placental labyrinth of the three-toed sloth (Bradypus tridactylus) was examined by electron microscopy. The material available was from two fetuses of 55 mm and 150 mm crown-rump length (CRL). The placenta of the younger specimen was a transition form between the syndesmochorial type and the endotheliochorial type. The interhemal membrane of the 55 mm CRL specimen consisted of the following components: 1) hypertrophied maternal endothelial cells surrounding the maternal vessels; 2) a small amount of extracellular material and spindle-shaped cells, both presumed to be of maternal origin; 3) a layer of syncytial trophoblast that had an unusual, reticulated or sponge-like appearance; and 4) the fetal capillary endothelium. In addition, the fetal connective tissue contained hypertrophied mesenchymal cells that were characterized by abundant granular endoplasmic reticulum. The placenta of the 150 mm CRL fetus was poorly preserved, but it was possible to determine that the placenta was of the endotheliochorial type. There was a close apposition of maternal endothelium and trophoblast. The results confirmed virtually all of lhe light microscopic observations of Wislocki (1927; 1928b). The ultrastructure of the sloth interhemal membrane is compared to that of other endotheliochorial placentas, particularly that of the shrew, with which it shows many cytological similarities.

Animals↗

PubMed1981

Autonomic innervation of salivary glands in the armadillo, anteater, and sloth (Edentata).

The intraglandular distribution of adrenergic and cholinergic nerve fibers was studied histochemically in the parotid, mandibular, and sublingual glands of six species of edentates belonging to the three families that comprise the order; namely the Dasypodidae (armadillos), the Myrmecophagidae (anteaters), and the Bradipodidae (sloths). The following histochemical techniques were used: (a) acetylcholinesterase reaction for the demonstration of cholinergic fibers; (b) formaldehyde- and glyoxylic acid-induced fluorescence for the demonstration of adrenergic fibers. In addition, norepinephrine (NE) was assayed fluorimetrically in the mandibular and parotid glands of the armadillo. A network of acetylcholinesterase-positive nerve fibers surrounds the intra- and interlobular ducts and endpieces of all glands; it is of low density in the mandibular and sublingual gland of the sloth, of high density in the sublingual gland of the anteater and of moderate density in the remaining glands. A vascular cholinergic innervation occurs in all salivary glands. Although present around the vessels, adrenergic new fibers were virtually absent from the parenchyma of all glands, even after in vitro incubation of glandular tissue with NE or after administration of NE to armadillos previously treated with a monoamine oxidase (MAO) inhibitor. Consistent with this fact, the amount of NE present in the parotid and mandibular gland of the armadillo was extremely low. These findings may indicate that the salivary secretion in the edentates is regulated by the parasympathetic rather than by the sympathetic nervous system.

Adrenergic Fibers↗

PubMed1975

Sensory and motor representation in the cerebral cortex of the three-toed sloth (Bradypus tridactylus).

Cortical sensory receiving areas were studied in 32 specimens of the three-toed sloth, Bradypus tridactylus, using the evoked response technique and barbiturate anaesthesia. Somatotopic organization in the somesthetic first area (S-I) was shown to be similar to that reported in higher mammals. The area devoted to the representation of the forelimb was considerably larger than that for the remaining body parts. The second somatosensory area (S-II), showing bilateral representation without a precise topographical organization, was identified in the rostral portion of the ectosylvian gyrus. Visual and auditory projections, occupying restricted areas, were found along the caudal banks of the ectosylvian fissure. Electrically excitable cortical motor area was explored in 8 animals anesthetized with diallyl barbituric acid in urethane. The motor representation of the various body parts was shown to coincide with the sensory projections, demonstrating the existence in a Eutherian mammal of a sensorimotor amalgam, identical to that described in marsupials. These findings suggest that sloths display a primitive pattern of neural organization, and that the sensory motor amalgam is a generalized form of cortical organization of primitive Therian mammals.

Acoustic Stimulation↗