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Carleton J. Phillips - One of the best experts on this subject based on the ideXlab platform.
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Cranial differentiation of fruit-eating bats (genus Artibeus) based on size-standardized data
Acta Chiropterologica, 2010Co-Authors: María R. Marchán-rivadeneira, Richard E. Strauss, José Antonio Guerrero, Carlos A. Mancina, Robert J. Baker, Carleton J. Phillips, Carretera De VaronaAbstract:Size-standardized craniometric variation was investigated among species of the genus Artibeus. Eleven extant and one extinct species were examined using geometric and linear morphometric analyses to evaluate morphological differences among species. Based on 19 landmarks located in the ventral side of the cranium, 29 size-standardized linear measurements were calculated and used for statistical multivariate analyses. Discriminant Function Analysis showed major interspecific differences in shape between A. anthonyi and A. concolor with respect to the remaining extant species of Artibeus. These two species are described as morphologically unique morphotypes with a broader rostrum, enlarged squamosal region, and wider basicranium. Specifically, a broader premaxilla is the character that better discriminates A. anthonyi from all other species, whereas a broader squamosal region (particularly the deep mandibular fossa, and elongated squamosal) and wider braincase are the main characters differentiating A. concolor. All other species of the genus overlap to varying extents in their morphology showing high shape similarities. The least variant shape features include the pterygoid fossa, the glenoid (mandibular) fossa, the maxillae, and the occipital region; these regions in all cases contribute to mechanical aspects of jaw function and bite. The fact that the least variant aspects of skull shape all involve feeding is consistent with the hypothesis that selection has favored a specific diet-associated morphology rather than divergence or character displacement in Artibeus.
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megamitochondria in the serous acinar cells of the submandibular gland of the neotropical fruit bat Artibeus obscurus
Anatomical Record-advances in Integrative Anatomy and Evolutionary Biology, 1997Co-Authors: Bernard Tandler, Toshikazu Nagato, Carleton J. PhillipsAbstract:Background As part of a continuing investigation of the comparative ultrastructure of chiropteran salivary glands, we examined the submandibular glands of eight species of neotropical fruit bats in the genus Artibeus. We previously described secretory granules of unusual substructure in the seromucous demilunar cells of this organ in some species in this genus. In the present study, we turned our attention to the serous acinar cells in the same glands. Methods Specimens of seven species of Artibeus were collected in neotropical localities. Salivary glands were extirpated in the field and thin slices were fixed by immersion in triple aldehyde-DMSO or in modified half-strength Karnovsky's fixative. Tissues were further processed for electron microscopy by conventional means. Results In contrast to seromucous cells, which exhibit species-specific diversification in bats of this genus, the secretory apparatus and secretory granules in the serous acinar cells are highly conserved across all seven species. The single exception involves the mitochondria in one species. In this instance, some of the serous cell mitochondria in Artibeus obscurus are modified into megamitochondria. Such organelles usually have short, peripheral cristae; a laminar inclusion is present in the matrix compartment of every outsized organelle. Inclusions of this nature never are present in normal-size mitochondria in the serous cells. None of the megamitochondria were observed in the process of degeneration. Conclusions The giant mitochondria in A. obscurus have a matrical structure that is radically different from that of the only other megamitochondria reported to occur in bat salivary glands. The factors that lead to variation in megamitochondrial substructure in different species, as well as the functional capacities of such giant organelles, are unknown. Anat. Rec. 248:13–17, 1997. © 1997 Wiley-Liss, Inc.
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Ultrastructure of the parotid salivary glands in seven species of fruit bats in the genus Artibeus
The Anatomical record, 1997Co-Authors: Bernard Tandler, Toshikazu Nagato, Carleton J. PhillipsAbstract:ABSTRACT Background: In previous studies, we determined that the submandibular glands of five species of Neotropical fruit bats in the genus Artibeus had seromucous granules in their demilune cells with substructures that varied interspecifically in accordance with systematic relationships. Moreover, the striated ducts in these frugivores exhibited structural modifications that apparently are related to the consumption of a diet rich in potassium, but deficient in sodium. We now turn our attention to the parotid gland in a large number of species in this genus to determine if it follows the same structural pattern as does the submandibular gland. Methods Members of seven different species of Artibeus were live-trapped in various Neotropical locations. The parotid glands were extirpated from euthanized bats, fixed in the field, and prepared for electron microscopic examination by conventional means. Results The parotid glands in all seven species were virtually identical in morphology. The acinar cells (determined to be seromucous on the basis of ultrastructural criteria) contain large numbers of what appear to be vacuoles, but which are a type of secretory granule. These granules have an electron-lucent matrix and may contain one or several circular membranous profiles arranged either concentrically or in a random array. These granules appear to form by progressive dilatation of the termini of Golgi saccules, with the nascent granules finally severing their connection with the Golgi apparatus. Many of the internal membranous profiles are formed simply by invaginations of the limiting membrane of the granule; others may result from indentation of the limiting membrane by protrusions from adjacent granules; the source of multiple internal membranes in certain granules is unclear. The exocytosis of these granules results in the acinar and intercalated duct lumina being filled with an abundance of membranous material. Such extruded membranes are present in some striated ducts, but not in others, suggesting that they are degraded during passage through the duct system. The striated ducts are of conventional appearance, lacking the frondose processes that are prominent in the submandibular glands of Artibeus. Conclusions The parotid gland in Artibeus shows none of the interspecific ultrastructural variability that characterizes the submandibular gland in bats of this genus. The seromucous acinar cells secrete granules that release phospholipids as well as glycoconjugates into the saliva. Based on the lack of frondose processes with their sodium-transporting portasomes, the striated ducts of the parotid gland are less concerned with electrolyte homeostasis than are those in the submandibular gland. Anat. Rec. 248:176–188, 1997. © 1997 Wiley-Liss, Inc.
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MOLECULAR SYSTEMATICS OF THE FRUIT BAT, Artibeus JAMAICENSIS : ORIGIN OF AN UNUSUAL ISLAND POPULATION
Journal of Mammalogy, 1996Co-Authors: Dorothy E. Pumo, Carleton J. Phillips, Iksoo Kim, James Remsen, Hugh H. GenowaysAbstract:DNA sequences from mitochondrial tRNA genes, the light strand replication site, and a region of the 12S rRNA gene were used to test the hypothesis that the unusual Antillean island subspecies, Artibeus jamaicensis schwartzi , was derived from a South American origin. Parsimony and bootstraping analyses allied the mitochondrial genome in these bats with mitochondrial DNA (mtDNA) isolated from Artibeus planirostris living in French Guiana rather than with mtDNA isolated from Artibeus jamaicensis from the Antilles or Mexico. Although the tRNA sequences differed slightly, the 12S rRNA sequences were identical in mtDNA isolated from A. j. schwartzi on St. Vincent and A. planirostris from French Guiana. It is proposed that A. planirostris was an early arrival to the Antilles, and that it possibly reached the Greater Antilles. Genetic analyses of these island populations may shed light on gene flow, speciation, and even extinction processes in bats. In broader interspecific comparisons, it was noted that the 12S rRNA and cytochrome- b genes might evolve somewhat differently among different stenodermatine species, and it was hypothesized that this could affect systematic analyses. None of the mtDNA sequence data supported the utility of the proposed genera Dermanura and Koopmania .
Robert J. Baker - One of the best experts on this subject based on the ideXlab platform.
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Speciation Dynamics of the Fruit-Eating Bats (Genus Artibeus): With Evidence of Ecological Divergence in Central American Populations
Bat Evolution Ecology and Conservation, 2013Co-Authors: Peter A Larsen, María R. Marchán-rivadeneira, Robert J. BakerAbstract:An increasing number of studies have identified complex diversification patterns of Neotropical faunal groups. One example of such complexity is found in bats of the widely distributed and locally abundant Neotropical genus Artibeus, wherein both allopatric and hybrid speciation events have been hypothesized. However, conflicting hypotheses regarding the timescale of diversification for Artibeus exist, and therefore, temporal inferences of the speciation events within the genus remain in doubt. We examine hypotheses regarding the chronology of diversification events within Artibeus. Our results indicate the most parsimonious time of origin for the genus was during the late Miocene to early Pliocene, with multiple speciation events during the early Pleistocene. Considering this evolutionary timescale, we revisit a century-old systematic debate regarding the status of Central American populations known as Artibeus lituratus intermedius. We present nuclear genetic data that indicate intermedius is distinct from lituratus and hypothesize that this distinction was ecologically driven, likely involved sympatry and reinforcement, and occurred during the late Pleistocene or early Holocene. Collectively, the data from Artibeus indicate that multiple speciation processes underlie extant levels of diversity within the genus. Our analyses provide further evidence for complex origins of the Neotropical fauna and contribute to a greater understanding of the natural processes underlying the origin of species.
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Distribution, abundance and roosts of the fruit bat Artibeus fraterculus (Chiroptera: Phyllostomidae)
Acta Chiropterologica, 2013Co-Authors: C. Miguel Pinto, María R. Marchán-rivadeneira, Elicio Tapia, Juan P. Carrera, Robert J. BakerAbstract:Where does a species live? How common is it? Where does it spend its inactive periods? These are basic questions about the biology of a species, which bring key information for application in conservation and management. Unfortunately, this information is available for only a minimum fraction of all animal species. Using 1) ecological niche modeling with maximum entropy (Maxent), 2) relative abundance estimates using museum records, and 3) field surveys of roosting sites, we report the fraternal fruit-eating bat, Artibeus fraterculus, as having a distribution limited to the Tumbesian ecoregion in Ecuador and west central Peru, being the relatively most abundant bat species throughout its range, with healthy populations which are primarily sustained by cultivated and introduced plants, and using human-made constructions as roost sites. Additionally, we described a large congregation of individuals of this species in a single roost, representing the largest colony reported for the genus Artibeus. These results may indicate resilience of A. fraterculus to human disturbance.
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Taxonomic status of Andersen’s fruit-eating bat ( Artibeus jamaicensis aequatorialis ) and revised classification of Artibeus (Chiroptera: Phyllostomidae)
Zootaxa, 2010Co-Authors: Peter A Larsen, María R. Marchán-rivadeneira, Robert J. BakerAbstract:Fruit-eating bats of the genus Artibeus are widely distributed across the Neotropics and are one of the most recently evolved assemblages of the family Phyllostomidae. Although the taxonomy and systematics of species of Artibeus has been the subject of an intense historical debate, the most current taxonomic arrangements recognize approximately eleven species within the genus. However, recent phylogenetic studies indicate that species diversity within South and Middle American populations of Artibeus is underestimated. South American populations referable to A. jamaicensis aequatorialis are of considerable interest because previous studies of mitochondrial DNA variation identified potential species level variation west of the Andes Mountains. In this study we use morphometric and genetic data (nuclear AFLPs) to investigate the taxonomic status of A. j. aequatorialis. Our results indicate that elevating aequatorialis to species level is appropriate based on statistically supported reciprocal monophyly in mitochondrial and nuclear datasets and diagnostic morphological characters. In light of our results, and of those presented elsewhere, we provide a revised classification of the genus.
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taxonomic status of andersen s fruit eating bat Artibeus jamaicensis aequatorialis and revised classification of Artibeus chiroptera phyllostomidae
Zootaxa, 2010Co-Authors: Peter A Larsen, Maria R Marchanrivadeneira, Robert J. BakerAbstract:Fruit-eating bats of the genus Artibeus are widely distributed across the Neotropics and are one of the most recently evolved assemblages of the family Phyllostomidae. Although the taxonomy and systematics of species of Artibeus has been the subject of an intense historical debate, the most current taxonomic arrangements recognize approximately eleven species within the genus. However, recent phylogenetic studies indicate that species diversity within South and Middle American populations of Artibeus is underestimated. South American populations referable to A. jamaicensis aequatorialis are of considerable interest because previous studies of mitochondrial DNA variation identified potential species level variation west of the Andes Mountains. In this study we use morphometric and genetic data (nuclear AFLPs) to investigate the taxonomic status of A. j. aequatorialis. Our results indicate that elevating aequatorialis to species level is appropriate based on statistically supported reciprocal monophyly in mitochondrial and nuclear datasets and diagnostic morphological characters. In light of our results, and of those presented elsewhere, we provide a revised classification of the genus.
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natural hybridization generates mammalian lineage with species characteristics
Proceedings of the National Academy of Sciences of the United States of America, 2010Co-Authors: Peter A Larsen, Maria R Marchanrivadeneira, Robert J. BakerAbstract:Most diploid species arise from single-species ancestors. Hybrid origins of new species are uncommon (except among polyploids) and are documented infrequently in animals. Examples of natural hybridization leading to speciation in mammals are exceedingly rare. Here, we show a Caribbean species of bat (Artibeus schwartzi) has a nuclear genome derived from two nonsister but congeneric species (A. jamaicensis and A. planirostris) and a mitochondrial genome that is from a third extinct or uncharacterized congener. Artibeus schwartzi is self-sustaining, morphologically distinct, and exists in near geographic isolation of its known parent species. Island effects (i.e., area, reduced habitat variability, and geographic isolation) likely have restricted gene flow from parental species into the Caribbean populations of this hybrid lineage, thus contributing to local adaptation and isolation of this newly produced taxon. We hypothesize differential rates of the development of reproductive isolation within the genus and estimate that 2.5 million years was an insufficient amount of time for the development of postzygotic isolation among the three species that hybridized to produce A. schwartzi. Reticulated evolution thus has resulted in a genomic combination from three evolutionary lineages and a transgressive phenotype that is distinct from all other known species of Artibeus. The data herein further demonstrate the phenomenon of speciation by hybridization in mammals is possible in nature.
Bernard Tandler - One of the best experts on this subject based on the ideXlab platform.
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megamitochondria in the serous acinar cells of the submandibular gland of the neotropical fruit bat Artibeus obscurus
Anatomical Record-advances in Integrative Anatomy and Evolutionary Biology, 1997Co-Authors: Bernard Tandler, Toshikazu Nagato, Carleton J. PhillipsAbstract:Background As part of a continuing investigation of the comparative ultrastructure of chiropteran salivary glands, we examined the submandibular glands of eight species of neotropical fruit bats in the genus Artibeus. We previously described secretory granules of unusual substructure in the seromucous demilunar cells of this organ in some species in this genus. In the present study, we turned our attention to the serous acinar cells in the same glands. Methods Specimens of seven species of Artibeus were collected in neotropical localities. Salivary glands were extirpated in the field and thin slices were fixed by immersion in triple aldehyde-DMSO or in modified half-strength Karnovsky's fixative. Tissues were further processed for electron microscopy by conventional means. Results In contrast to seromucous cells, which exhibit species-specific diversification in bats of this genus, the secretory apparatus and secretory granules in the serous acinar cells are highly conserved across all seven species. The single exception involves the mitochondria in one species. In this instance, some of the serous cell mitochondria in Artibeus obscurus are modified into megamitochondria. Such organelles usually have short, peripheral cristae; a laminar inclusion is present in the matrix compartment of every outsized organelle. Inclusions of this nature never are present in normal-size mitochondria in the serous cells. None of the megamitochondria were observed in the process of degeneration. Conclusions The giant mitochondria in A. obscurus have a matrical structure that is radically different from that of the only other megamitochondria reported to occur in bat salivary glands. The factors that lead to variation in megamitochondrial substructure in different species, as well as the functional capacities of such giant organelles, are unknown. Anat. Rec. 248:13–17, 1997. © 1997 Wiley-Liss, Inc.
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Ultrastructure of the parotid salivary glands in seven species of fruit bats in the genus Artibeus
The Anatomical record, 1997Co-Authors: Bernard Tandler, Toshikazu Nagato, Carleton J. PhillipsAbstract:ABSTRACT Background: In previous studies, we determined that the submandibular glands of five species of Neotropical fruit bats in the genus Artibeus had seromucous granules in their demilune cells with substructures that varied interspecifically in accordance with systematic relationships. Moreover, the striated ducts in these frugivores exhibited structural modifications that apparently are related to the consumption of a diet rich in potassium, but deficient in sodium. We now turn our attention to the parotid gland in a large number of species in this genus to determine if it follows the same structural pattern as does the submandibular gland. Methods Members of seven different species of Artibeus were live-trapped in various Neotropical locations. The parotid glands were extirpated from euthanized bats, fixed in the field, and prepared for electron microscopic examination by conventional means. Results The parotid glands in all seven species were virtually identical in morphology. The acinar cells (determined to be seromucous on the basis of ultrastructural criteria) contain large numbers of what appear to be vacuoles, but which are a type of secretory granule. These granules have an electron-lucent matrix and may contain one or several circular membranous profiles arranged either concentrically or in a random array. These granules appear to form by progressive dilatation of the termini of Golgi saccules, with the nascent granules finally severing their connection with the Golgi apparatus. Many of the internal membranous profiles are formed simply by invaginations of the limiting membrane of the granule; others may result from indentation of the limiting membrane by protrusions from adjacent granules; the source of multiple internal membranes in certain granules is unclear. The exocytosis of these granules results in the acinar and intercalated duct lumina being filled with an abundance of membranous material. Such extruded membranes are present in some striated ducts, but not in others, suggesting that they are degraded during passage through the duct system. The striated ducts are of conventional appearance, lacking the frondose processes that are prominent in the submandibular glands of Artibeus. Conclusions The parotid gland in Artibeus shows none of the interspecific ultrastructural variability that characterizes the submandibular gland in bats of this genus. The seromucous acinar cells secrete granules that release phospholipids as well as glycoconjugates into the saliva. Based on the lack of frondose processes with their sodium-transporting portasomes, the striated ducts of the parotid gland are less concerned with electrolyte homeostasis than are those in the submandibular gland. Anat. Rec. 248:176–188, 1997. © 1997 Wiley-Liss, Inc.
Peter A Larsen - One of the best experts on this subject based on the ideXlab platform.
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Speciation Dynamics of the Fruit-Eating Bats (Genus Artibeus): With Evidence of Ecological Divergence in Central American Populations
Bat Evolution Ecology and Conservation, 2013Co-Authors: Peter A Larsen, María R. Marchán-rivadeneira, Robert J. BakerAbstract:An increasing number of studies have identified complex diversification patterns of Neotropical faunal groups. One example of such complexity is found in bats of the widely distributed and locally abundant Neotropical genus Artibeus, wherein both allopatric and hybrid speciation events have been hypothesized. However, conflicting hypotheses regarding the timescale of diversification for Artibeus exist, and therefore, temporal inferences of the speciation events within the genus remain in doubt. We examine hypotheses regarding the chronology of diversification events within Artibeus. Our results indicate the most parsimonious time of origin for the genus was during the late Miocene to early Pliocene, with multiple speciation events during the early Pleistocene. Considering this evolutionary timescale, we revisit a century-old systematic debate regarding the status of Central American populations known as Artibeus lituratus intermedius. We present nuclear genetic data that indicate intermedius is distinct from lituratus and hypothesize that this distinction was ecologically driven, likely involved sympatry and reinforcement, and occurred during the late Pleistocene or early Holocene. Collectively, the data from Artibeus indicate that multiple speciation processes underlie extant levels of diversity within the genus. Our analyses provide further evidence for complex origins of the Neotropical fauna and contribute to a greater understanding of the natural processes underlying the origin of species.
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Taxonomic status of Andersen’s fruit-eating bat ( Artibeus jamaicensis aequatorialis ) and revised classification of Artibeus (Chiroptera: Phyllostomidae)
Zootaxa, 2010Co-Authors: Peter A Larsen, María R. Marchán-rivadeneira, Robert J. BakerAbstract:Fruit-eating bats of the genus Artibeus are widely distributed across the Neotropics and are one of the most recently evolved assemblages of the family Phyllostomidae. Although the taxonomy and systematics of species of Artibeus has been the subject of an intense historical debate, the most current taxonomic arrangements recognize approximately eleven species within the genus. However, recent phylogenetic studies indicate that species diversity within South and Middle American populations of Artibeus is underestimated. South American populations referable to A. jamaicensis aequatorialis are of considerable interest because previous studies of mitochondrial DNA variation identified potential species level variation west of the Andes Mountains. In this study we use morphometric and genetic data (nuclear AFLPs) to investigate the taxonomic status of A. j. aequatorialis. Our results indicate that elevating aequatorialis to species level is appropriate based on statistically supported reciprocal monophyly in mitochondrial and nuclear datasets and diagnostic morphological characters. In light of our results, and of those presented elsewhere, we provide a revised classification of the genus.
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taxonomic status of andersen s fruit eating bat Artibeus jamaicensis aequatorialis and revised classification of Artibeus chiroptera phyllostomidae
Zootaxa, 2010Co-Authors: Peter A Larsen, Maria R Marchanrivadeneira, Robert J. BakerAbstract:Fruit-eating bats of the genus Artibeus are widely distributed across the Neotropics and are one of the most recently evolved assemblages of the family Phyllostomidae. Although the taxonomy and systematics of species of Artibeus has been the subject of an intense historical debate, the most current taxonomic arrangements recognize approximately eleven species within the genus. However, recent phylogenetic studies indicate that species diversity within South and Middle American populations of Artibeus is underestimated. South American populations referable to A. jamaicensis aequatorialis are of considerable interest because previous studies of mitochondrial DNA variation identified potential species level variation west of the Andes Mountains. In this study we use morphometric and genetic data (nuclear AFLPs) to investigate the taxonomic status of A. j. aequatorialis. Our results indicate that elevating aequatorialis to species level is appropriate based on statistically supported reciprocal monophyly in mitochondrial and nuclear datasets and diagnostic morphological characters. In light of our results, and of those presented elsewhere, we provide a revised classification of the genus.
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natural hybridization generates mammalian lineage with species characteristics
Proceedings of the National Academy of Sciences of the United States of America, 2010Co-Authors: Peter A Larsen, Maria R Marchanrivadeneira, Robert J. BakerAbstract:Most diploid species arise from single-species ancestors. Hybrid origins of new species are uncommon (except among polyploids) and are documented infrequently in animals. Examples of natural hybridization leading to speciation in mammals are exceedingly rare. Here, we show a Caribbean species of bat (Artibeus schwartzi) has a nuclear genome derived from two nonsister but congeneric species (A. jamaicensis and A. planirostris) and a mitochondrial genome that is from a third extinct or uncharacterized congener. Artibeus schwartzi is self-sustaining, morphologically distinct, and exists in near geographic isolation of its known parent species. Island effects (i.e., area, reduced habitat variability, and geographic isolation) likely have restricted gene flow from parental species into the Caribbean populations of this hybrid lineage, thus contributing to local adaptation and isolation of this newly produced taxon. We hypothesize differential rates of the development of reproductive isolation within the genus and estimate that 2.5 million years was an insufficient amount of time for the development of postzygotic isolation among the three species that hybridized to produce A. schwartzi. Reticulated evolution thus has resulted in a genomic combination from three evolutionary lineages and a transgressive phenotype that is distinct from all other known species of Artibeus. The data herein further demonstrate the phenomenon of speciation by hybridization in mammals is possible in nature.
Toshikazu Nagato - One of the best experts on this subject based on the ideXlab platform.
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megamitochondria in the serous acinar cells of the submandibular gland of the neotropical fruit bat Artibeus obscurus
Anatomical Record-advances in Integrative Anatomy and Evolutionary Biology, 1997Co-Authors: Bernard Tandler, Toshikazu Nagato, Carleton J. PhillipsAbstract:Background As part of a continuing investigation of the comparative ultrastructure of chiropteran salivary glands, we examined the submandibular glands of eight species of neotropical fruit bats in the genus Artibeus. We previously described secretory granules of unusual substructure in the seromucous demilunar cells of this organ in some species in this genus. In the present study, we turned our attention to the serous acinar cells in the same glands. Methods Specimens of seven species of Artibeus were collected in neotropical localities. Salivary glands were extirpated in the field and thin slices were fixed by immersion in triple aldehyde-DMSO or in modified half-strength Karnovsky's fixative. Tissues were further processed for electron microscopy by conventional means. Results In contrast to seromucous cells, which exhibit species-specific diversification in bats of this genus, the secretory apparatus and secretory granules in the serous acinar cells are highly conserved across all seven species. The single exception involves the mitochondria in one species. In this instance, some of the serous cell mitochondria in Artibeus obscurus are modified into megamitochondria. Such organelles usually have short, peripheral cristae; a laminar inclusion is present in the matrix compartment of every outsized organelle. Inclusions of this nature never are present in normal-size mitochondria in the serous cells. None of the megamitochondria were observed in the process of degeneration. Conclusions The giant mitochondria in A. obscurus have a matrical structure that is radically different from that of the only other megamitochondria reported to occur in bat salivary glands. The factors that lead to variation in megamitochondrial substructure in different species, as well as the functional capacities of such giant organelles, are unknown. Anat. Rec. 248:13–17, 1997. © 1997 Wiley-Liss, Inc.
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Ultrastructure of the parotid salivary glands in seven species of fruit bats in the genus Artibeus
The Anatomical record, 1997Co-Authors: Bernard Tandler, Toshikazu Nagato, Carleton J. PhillipsAbstract:ABSTRACT Background: In previous studies, we determined that the submandibular glands of five species of Neotropical fruit bats in the genus Artibeus had seromucous granules in their demilune cells with substructures that varied interspecifically in accordance with systematic relationships. Moreover, the striated ducts in these frugivores exhibited structural modifications that apparently are related to the consumption of a diet rich in potassium, but deficient in sodium. We now turn our attention to the parotid gland in a large number of species in this genus to determine if it follows the same structural pattern as does the submandibular gland. Methods Members of seven different species of Artibeus were live-trapped in various Neotropical locations. The parotid glands were extirpated from euthanized bats, fixed in the field, and prepared for electron microscopic examination by conventional means. Results The parotid glands in all seven species were virtually identical in morphology. The acinar cells (determined to be seromucous on the basis of ultrastructural criteria) contain large numbers of what appear to be vacuoles, but which are a type of secretory granule. These granules have an electron-lucent matrix and may contain one or several circular membranous profiles arranged either concentrically or in a random array. These granules appear to form by progressive dilatation of the termini of Golgi saccules, with the nascent granules finally severing their connection with the Golgi apparatus. Many of the internal membranous profiles are formed simply by invaginations of the limiting membrane of the granule; others may result from indentation of the limiting membrane by protrusions from adjacent granules; the source of multiple internal membranes in certain granules is unclear. The exocytosis of these granules results in the acinar and intercalated duct lumina being filled with an abundance of membranous material. Such extruded membranes are present in some striated ducts, but not in others, suggesting that they are degraded during passage through the duct system. The striated ducts are of conventional appearance, lacking the frondose processes that are prominent in the submandibular glands of Artibeus. Conclusions The parotid gland in Artibeus shows none of the interspecific ultrastructural variability that characterizes the submandibular gland in bats of this genus. The seromucous acinar cells secrete granules that release phospholipids as well as glycoconjugates into the saliva. Based on the lack of frondose processes with their sodium-transporting portasomes, the striated ducts of the parotid gland are less concerned with electrolyte homeostasis than are those in the submandibular gland. Anat. Rec. 248:176–188, 1997. © 1997 Wiley-Liss, Inc.
