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Mark S. Springer - One of the best experts on this subject based on the ideXlab platform.
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Phylogenomics and the Genetic Architecture of the Placental Mammal Radiation.
Annual review of animal biosciences, 2020Co-Authors: William J Murphy, Nicole M. Foley, Kevin R. Bredemeyer, John Gatesy, Mark S. SpringerAbstract:The genomes of Placental Mammals are being sequenced at an unprecedented rate. Alignments of hundreds, and one day thousands, of genomes spanning the rich living and extinct diversity of species offer unparalleled power to resolve phylogenetic controversies, identify genomic innovations of adaptation, and dissect the genetic architecture of reproductive isolation. We highlight outstanding questions about the earliest phases of Placental Mammal diversification and the promise of newer methods, as well as remaining challenges, toward using whole-genome data to resolve Placental Mammal phylogeny. The next phase of Mammalian comparative genomics will see the completion and application of finished-quality, gapless genome assemblies from many ordinal lineages and closely related species. Interspecific comparisons between the most hypervariable genomic loci will likely reveal large, but heretofore mostly underappreciated, effects on population divergence, morphological innovation, and the origin of new species. Expected final online publication date for the Annual Review of Animal Biosciences, Volume 9 is February 16, 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
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inactivation of thermogenic ucp1 as a historical contingency in multiple Placental Mammal clades
bioRxiv, 2016Co-Authors: Michael J Gaudry, Mark S. Springer, Martin Jastroch, Jason R Treberg, Michael Hofreiter, Johanna L A Paijmans, James Starrett, Nathan Wales, Anthony V Signore, Kevin L CampbellAbstract:Mitochondrial uncoupling protein 1 (UCP1) is essential for non-shivering thermogenesis in brown adipose tissue and is widely accepted to have played a key thermoregulatory role in small-bodied and neonatal Placental Mammals that enabled the exploitation of cold environments. Here we map ucp1 sequences from 133 Mammals onto a species tree constructed from a ~51-kb sequence alignment and show that inactivating mutations have occurred in at least eight of the 18 traditional Placental orders, thereby challenging the physiological importance of UCP1 across Placentalia. Selection and timetree analyses further reveal that ucp1 inactivations temporally correspond with strong secondary reductions in metabolic intensity in xenarthrans and pangolins, or in six other lineages coincided with a ~30 million year episode of global cooling in the Paleogene that promoted sharp increases in body mass and cladogenesis evident in the fossil record. Our findings also demonstrate that members of various lineages ( e.g. , cetaceans, horses, woolly mammoths, Steller9s sea cows) evolved extreme cold hardiness in the absence of UCP1-mediated thermogenesis. Finally, we identify ucp1 inactivation as a historical contingency that is linked to the current low species diversity of clades lacking functional UCP1, thus providing the first evidence for species selection related to the presence or absence of a single gene product.
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Waking the undead: Implications of a soft explosive model for the timing of Placental Mammal diversification
Molecular phylogenetics and evolution, 2016Co-Authors: Mark S. Springer, Eduardo Eizirik, Robert W. Meredith, Christopher A. Emerling, Jan E. Janecka, William J MurphyAbstract:The explosive, long fuse, and short fuse models represent competing hypotheses for the timing of Placental Mammal diversification. Support for the explosive model, which posits both interordinal and intraordinal diversification after the KPg mass extinction, derives from morphological cladistic studies that place Cretaceous eutherians outside of crown Placentalia. By contrast, most molecular studies favor the long fuse model wherein interordinal cladogenesis occurred in the Cretaceous followed by intraordinal cladogenesis after the KPg boundary. Phillips (2016) proposed a soft explosive model that allows for the emergence of a few lineages (Xenarthra, Afrotheria, Euarchontoglires, Laurasiatheria) in the Cretaceous, but otherwise agrees with the explosive model in positing the majority of interordinal diversification after the KPg mass extinction. Phillips (2016) argues that rate transference errors associated with large body size and long lifespan have inflated previous estimates of interordinal divergence times, and further suggests that most interordinal divergences are positioned after the KPg boundary when rate transference errors are avoided through the elimination of calibrations in large-bodied and/or long lifespan clades. Here, we show that rate transference errors can also occur in the opposite direction and drag forward estimated divergence dates when calibrations in large-bodied/long lifespan clades are omitted. This dragging forward effect results in the occurrence of more than half a billion years of 'zombie lineages' on Phillips' preferred timetree. By contrast with ghost lineages, which are a logical byproduct of an incomplete fossil record, zombie lineages occur when estimated divergence dates are younger than the minimum age of the oldest crown fossils. We also present the results of new timetree analyses that address the rate transference problem highlighted by Phillips (2016) by deleting taxa that exceed thresholds for body size and lifespan. These analyses recover all interordinal divergence times in the Cretaceous and are consistent with the long fuse model of Placental diversification. Finally, we outline potential problems with morphological cladistic analyses of higher-level relationships among Placental Mammals that may account for the perceived discrepancies between molecular and paleontological estimates of Placental divergence times.
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technical comment on the Placental Mammal ancestor and the post k pg radiation of Placentals
Science, 2013Co-Authors: Mark S. Springer, Robert W. Meredith, Emma C. Teeling, William J MurphyAbstract:O’Leary et al . (Research Article, 8 February 2013, p. 662) examined Mammalian relationships and divergence times and concluded that a single Placental ancestor crossed the Cretaceous-Paleogene (K-Pg) boundary. This conclusion relies on phylogenetic analyses that fail to discriminate between homology and homoplasy and further implies virus-like rates of nucleotide substitution in early Paleocene Placentals.
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Morphology and Placental Mammal phylogeny.
Systematic biology, 2008Co-Authors: Mark S. Springer, Eduardo Eizirik, Robert W. Meredith, Emma C. Teeling, William J MurphyAbstract:In a recent article on Placental Mammal phylogeny (Springer et al, 2007), we discussed evidence for correlated character evolution among morphological characters. We also performed pseudoextinction analy ses that assessed whether Placental orders remained in the expected superordinal group (Afrotheria, Xenarthra, Euarchontoglires, Laurasiatheria) when molecular and soft-tissue data were coded as missing and only oste ological data from Asher et al. (2003) remained for the pseudoextinct taxa. Finally, we examined congruence among 21 molecular data partitions and Asher et al/s (2003) morphological data. Our results demonstrated that most Placental orders moved to a different superor dinal group when treated as pseudoextinct and also that Asher et al/s (2003) morphological data consistently emerged as the most incongruent data partition. Based on these results, we questioned the ability of current morphological data sets and phylogenetic methods to reconstruct higher level relationships among Placental Mammals. In their response to our paper, Asher et al. (2008) raise several objections including (1) continued debate over our "preferred 4-clade topology" (p. 311) that renders our conclusions on morphology "premature" (p. 311); (2) basing our conclusions "on a single morpho logical data set" (p. 312); (3) our use of pseudoextinction techniques "to make broad generalizations about the quality of data for Mammal phylogeny reconstruction" (p. 313); and (4) our conditional acknowledgement of the primacy "of morphological data to infer phylogeny of fossil taxa" (p. 313). Asher et al. (2008) make a number of useful points, but as discussed below these do not diminish the main conclusions of our earlier paper.
William J Murphy - One of the best experts on this subject based on the ideXlab platform.
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Phylogenomics and the Genetic Architecture of the Placental Mammal Radiation.
Annual review of animal biosciences, 2020Co-Authors: William J Murphy, Nicole M. Foley, Kevin R. Bredemeyer, John Gatesy, Mark S. SpringerAbstract:The genomes of Placental Mammals are being sequenced at an unprecedented rate. Alignments of hundreds, and one day thousands, of genomes spanning the rich living and extinct diversity of species offer unparalleled power to resolve phylogenetic controversies, identify genomic innovations of adaptation, and dissect the genetic architecture of reproductive isolation. We highlight outstanding questions about the earliest phases of Placental Mammal diversification and the promise of newer methods, as well as remaining challenges, toward using whole-genome data to resolve Placental Mammal phylogeny. The next phase of Mammalian comparative genomics will see the completion and application of finished-quality, gapless genome assemblies from many ordinal lineages and closely related species. Interspecific comparisons between the most hypervariable genomic loci will likely reveal large, but heretofore mostly underappreciated, effects on population divergence, morphological innovation, and the origin of new species. Expected final online publication date for the Annual Review of Animal Biosciences, Volume 9 is February 16, 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
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Waking the undead: Implications of a soft explosive model for the timing of Placental Mammal diversification
Molecular phylogenetics and evolution, 2016Co-Authors: Mark S. Springer, Eduardo Eizirik, Robert W. Meredith, Christopher A. Emerling, Jan E. Janecka, William J MurphyAbstract:The explosive, long fuse, and short fuse models represent competing hypotheses for the timing of Placental Mammal diversification. Support for the explosive model, which posits both interordinal and intraordinal diversification after the KPg mass extinction, derives from morphological cladistic studies that place Cretaceous eutherians outside of crown Placentalia. By contrast, most molecular studies favor the long fuse model wherein interordinal cladogenesis occurred in the Cretaceous followed by intraordinal cladogenesis after the KPg boundary. Phillips (2016) proposed a soft explosive model that allows for the emergence of a few lineages (Xenarthra, Afrotheria, Euarchontoglires, Laurasiatheria) in the Cretaceous, but otherwise agrees with the explosive model in positing the majority of interordinal diversification after the KPg mass extinction. Phillips (2016) argues that rate transference errors associated with large body size and long lifespan have inflated previous estimates of interordinal divergence times, and further suggests that most interordinal divergences are positioned after the KPg boundary when rate transference errors are avoided through the elimination of calibrations in large-bodied and/or long lifespan clades. Here, we show that rate transference errors can also occur in the opposite direction and drag forward estimated divergence dates when calibrations in large-bodied/long lifespan clades are omitted. This dragging forward effect results in the occurrence of more than half a billion years of 'zombie lineages' on Phillips' preferred timetree. By contrast with ghost lineages, which are a logical byproduct of an incomplete fossil record, zombie lineages occur when estimated divergence dates are younger than the minimum age of the oldest crown fossils. We also present the results of new timetree analyses that address the rate transference problem highlighted by Phillips (2016) by deleting taxa that exceed thresholds for body size and lifespan. These analyses recover all interordinal divergence times in the Cretaceous and are consistent with the long fuse model of Placental diversification. Finally, we outline potential problems with morphological cladistic analyses of higher-level relationships among Placental Mammals that may account for the perceived discrepancies between molecular and paleontological estimates of Placental divergence times.
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technical comment on the Placental Mammal ancestor and the post k pg radiation of Placentals
Science, 2013Co-Authors: Mark S. Springer, Robert W. Meredith, Emma C. Teeling, William J MurphyAbstract:O’Leary et al . (Research Article, 8 February 2013, p. 662) examined Mammalian relationships and divergence times and concluded that a single Placental ancestor crossed the Cretaceous-Paleogene (K-Pg) boundary. This conclusion relies on phylogenetic analyses that fail to discriminate between homology and homoplasy and further implies virus-like rates of nucleotide substitution in early Paleocene Placentals.
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Morphology and Placental Mammal phylogeny.
Systematic biology, 2008Co-Authors: Mark S. Springer, Eduardo Eizirik, Robert W. Meredith, Emma C. Teeling, William J MurphyAbstract:In a recent article on Placental Mammal phylogeny (Springer et al, 2007), we discussed evidence for correlated character evolution among morphological characters. We also performed pseudoextinction analy ses that assessed whether Placental orders remained in the expected superordinal group (Afrotheria, Xenarthra, Euarchontoglires, Laurasiatheria) when molecular and soft-tissue data were coded as missing and only oste ological data from Asher et al. (2003) remained for the pseudoextinct taxa. Finally, we examined congruence among 21 molecular data partitions and Asher et al/s (2003) morphological data. Our results demonstrated that most Placental orders moved to a different superor dinal group when treated as pseudoextinct and also that Asher et al/s (2003) morphological data consistently emerged as the most incongruent data partition. Based on these results, we questioned the ability of current morphological data sets and phylogenetic methods to reconstruct higher level relationships among Placental Mammals. In their response to our paper, Asher et al. (2008) raise several objections including (1) continued debate over our "preferred 4-clade topology" (p. 311) that renders our conclusions on morphology "premature" (p. 311); (2) basing our conclusions "on a single morpho logical data set" (p. 312); (3) our use of pseudoextinction techniques "to make broad generalizations about the quality of data for Mammal phylogeny reconstruction" (p. 313); and (4) our conditional acknowledgement of the primacy "of morphological data to infer phylogeny of fossil taxa" (p. 313). Asher et al. (2008) make a number of useful points, but as discussed below these do not diminish the main conclusions of our earlier paper.
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using genomic data to unravel the root of the Placental Mammal phylogeny
Genome Research, 2007Co-Authors: William J Murphy, Mark S. Springer, Thomas H Pringle, Tess A Crider, Webb MillerAbstract:The phylogeny of Placental Mammals is a critical framework for choosing future genome sequencing targets and for resolving the ancestral Mammalian genome at the nucleotide level. Despite considerable recent progress defining superordinal relationships, several branches remain poorly resolved, including the root of the Placental tree. Here we analyzed the genome sequence assemblies of human, armadillo, elephant, and opossum to identify informative coding indels that would serve as rare genomic changes to infer early events in Placental Mammal phylogeny. We also expanded our species sampling by including sequence data from >30 ongoing genome projects, followed by PCR and sequencing validation of each indel in additional taxa. Our data provide support for a sister-group relationship between Afrotheria and Xenarthra (the Atlantogenata hypothesis), which is in turn the sister-taxon to Boreoeutheria. We failed to recover any indels in support of a basal position for Xenarthra (Epitheria), which is suggested by morphology and a recent retroposon analysis, or a hypothesis with Afrotheria basal (ExafricoPlacentalia), which is favored by phylogenetic analysis of large nuclear gene data sets. In addition, we identified two retroposon insertions that also support Atlantogenata and none for the alternative hypotheses. A revised molecular timescale based on these phylogenetic inferences suggests Afrotheria and Xenarthra diverged from other Placental Mammals ∼103 (95–114) million years ago. We discuss the impacts of this topology on earlier phylogenetic reconstructions and repeat-based inferences of phylogeny.
Hirotaka Sakamoto - One of the best experts on this subject based on the ideXlab platform.
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identification of the sexually dimorphic gastrin releasing peptide system in the lumbosacral spinal cord that controls male reproductive function in the mouse and asian house musk shrew suncus murinus
The Journal of Comparative Neurology, 2017Co-Authors: Kei Tamura, Takamichi Jogahara, Yasuhisa Kobayashi, Asuka Hirooka, Keiko Takanami, Tatsuya Sakamoto, Hirotaka SakamotoAbstract:Several regions of the brain and spinal cord control male reproductive function. We previously demonstrated that the gastrin-releasing peptide (GRP) system, located in the lumbosacral spinal cord of rats, controls spinal centers to promote penile reflexes during male copulatory behavior. However, little information exists on the male-specific spinal GRP system in animals other than rats. The objective of this study was to examine the functional generality of the spinal GRP system in Mammals using the Asian house musk shrew (Suncus murinus; suncus named as the laboratory strain), a specialized Placental Mammal model. Mice are also used for a representative model of small laboratory animals. We first isolated complementary DNA encoding GRP in suncus. Phylogenetic analysis revealed that suncus preproGRP was clustered to an independent branch. Reverse transcription-PCR showed that GRP and its receptor mRNAs were both expressed in the lumbar spinal cord of suncus and mice. Immunohistochemistry for GRP demonstrated that the sexually dimorphic GRP system and male-specific expression/distribution patterns of GRP in the lumbosacral spinal cord in suncus are similar to those of mice. In suncus, we further found that most GRP-expressing neurons in males also express androgen receptors, suggesting that this male-dominant system in suncus is also androgen-dependent. Taken together, these results indicate that the sexually dimorphic spinal GRP system exists not only in mice but also in suncus, suggesting that this system is a conserved property in Mammals. This article is protected by copyright. All rights reserved.
Eduardo Eizirik - One of the best experts on this subject based on the ideXlab platform.
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Waking the undead: Implications of a soft explosive model for the timing of Placental Mammal diversification
Molecular phylogenetics and evolution, 2016Co-Authors: Mark S. Springer, Eduardo Eizirik, Robert W. Meredith, Christopher A. Emerling, Jan E. Janecka, William J MurphyAbstract:The explosive, long fuse, and short fuse models represent competing hypotheses for the timing of Placental Mammal diversification. Support for the explosive model, which posits both interordinal and intraordinal diversification after the KPg mass extinction, derives from morphological cladistic studies that place Cretaceous eutherians outside of crown Placentalia. By contrast, most molecular studies favor the long fuse model wherein interordinal cladogenesis occurred in the Cretaceous followed by intraordinal cladogenesis after the KPg boundary. Phillips (2016) proposed a soft explosive model that allows for the emergence of a few lineages (Xenarthra, Afrotheria, Euarchontoglires, Laurasiatheria) in the Cretaceous, but otherwise agrees with the explosive model in positing the majority of interordinal diversification after the KPg mass extinction. Phillips (2016) argues that rate transference errors associated with large body size and long lifespan have inflated previous estimates of interordinal divergence times, and further suggests that most interordinal divergences are positioned after the KPg boundary when rate transference errors are avoided through the elimination of calibrations in large-bodied and/or long lifespan clades. Here, we show that rate transference errors can also occur in the opposite direction and drag forward estimated divergence dates when calibrations in large-bodied/long lifespan clades are omitted. This dragging forward effect results in the occurrence of more than half a billion years of 'zombie lineages' on Phillips' preferred timetree. By contrast with ghost lineages, which are a logical byproduct of an incomplete fossil record, zombie lineages occur when estimated divergence dates are younger than the minimum age of the oldest crown fossils. We also present the results of new timetree analyses that address the rate transference problem highlighted by Phillips (2016) by deleting taxa that exceed thresholds for body size and lifespan. These analyses recover all interordinal divergence times in the Cretaceous and are consistent with the long fuse model of Placental diversification. Finally, we outline potential problems with morphological cladistic analyses of higher-level relationships among Placental Mammals that may account for the perceived discrepancies between molecular and paleontological estimates of Placental divergence times.
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Morphology and Placental Mammal phylogeny.
Systematic biology, 2008Co-Authors: Mark S. Springer, Eduardo Eizirik, Robert W. Meredith, Emma C. Teeling, William J MurphyAbstract:In a recent article on Placental Mammal phylogeny (Springer et al, 2007), we discussed evidence for correlated character evolution among morphological characters. We also performed pseudoextinction analy ses that assessed whether Placental orders remained in the expected superordinal group (Afrotheria, Xenarthra, Euarchontoglires, Laurasiatheria) when molecular and soft-tissue data were coded as missing and only oste ological data from Asher et al. (2003) remained for the pseudoextinct taxa. Finally, we examined congruence among 21 molecular data partitions and Asher et al/s (2003) morphological data. Our results demonstrated that most Placental orders moved to a different superor dinal group when treated as pseudoextinct and also that Asher et al/s (2003) morphological data consistently emerged as the most incongruent data partition. Based on these results, we questioned the ability of current morphological data sets and phylogenetic methods to reconstruct higher level relationships among Placental Mammals. In their response to our paper, Asher et al. (2008) raise several objections including (1) continued debate over our "preferred 4-clade topology" (p. 311) that renders our conclusions on morphology "premature" (p. 311); (2) basing our conclusions "on a single morpho logical data set" (p. 312); (3) our use of pseudoextinction techniques "to make broad generalizations about the quality of data for Mammal phylogeny reconstruction" (p. 313); and (4) our conditional acknowledgement of the primacy "of morphological data to infer phylogeny of fossil taxa" (p. 313). Asher et al. (2008) make a number of useful points, but as discussed below these do not diminish the main conclusions of our earlier paper.
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Placental Mammal diversification and the cretaceous tertiary boundary
Proceedings of the National Academy of Sciences of the United States of America, 2003Co-Authors: Mark S. Springer, William J Murphy, Eduardo Eizirik, Stephen J ObrienAbstract:Competing hypotheses for the timing of the Placental Mammal radiation focus on whether extant Placental orders originated and diversified before or after the Cretaceous-Tertiary (K/T) boundary. Molecular studies that have addressed this issue suffer from single calibration points, unwarranted assumptions about the molecular clock, and/or taxon sampling that lacks representatives of all Placental orders. We investigated this problem using the largest available molecular data set for Placental Mammals, which includes segments of 19 nuclear and three mitochondrial genes for representatives of all extant Placental orders. We used the Thorne/Kishino method, which permits simultaneous constraints from the fossil record and allows rates of molecular evolution to vary on different branches of a phylogenetic tree. Analyses that used different sets of fossil constraints, different priors for the base of Placentalia, and different data partitions all support interordinal divergences in the Cretaceous followed by intraordinal diversification mostly after the K/T boundary. Four Placental orders show intraordinal diversification that predates the K/T boundary, but only by an average of 10 million years. In contrast to some molecular studies that date the rat–mouse split as old as 46 million years, our results show improved agreement with the fossil record and place this split at 16–23 million years. To test the hypothesis that molecular estimates of Cretaceous divergence times are an artifact of increased body size subsequent to the K/T boundary, we also performed analyses with a “K/T body size” taxon set. In these analyses, interordinal splits remained in the Cretaceous.
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Placental Mammal diversification and the Cretaceous–Tertiary boundary
Proceedings of the National Academy of Sciences of the United States of America, 2003Co-Authors: Mark S. Springer, William J Murphy, Eduardo Eizirik, Stephen J. O'brienAbstract:Competing hypotheses for the timing of the Placental Mammal radiation focus on whether extant Placental orders originated and diversified before or after the Cretaceous-Tertiary (K/T) boundary. Molecular studies that have addressed this issue suffer from single calibration points, unwarranted assumptions about the molecular clock, and/or taxon sampling that lacks representatives of all Placental orders. We investigated this problem using the largest available molecular data set for Placental Mammals, which includes segments of 19 nuclear and three mitochondrial genes for representatives of all extant Placental orders. We used the Thorne/Kishino method, which permits simultaneous constraints from the fossil record and allows rates of molecular evolution to vary on different branches of a phylogenetic tree. Analyses that used different sets of fossil constraints, different priors for the base of Placentalia, and different data partitions all support interordinal divergences in the Cretaceous followed by intraordinal diversification mostly after the K/T boundary. Four Placental orders show intraordinal diversification that predates the K/T boundary, but only by an average of 10 million years. In contrast to some molecular studies that date the rat–mouse split as old as 46 million years, our results show improved agreement with the fossil record and place this split at 16–23 million years. To test the hypothesis that molecular estimates of Cretaceous divergence times are an artifact of increased body size subsequent to the K/T boundary, we also performed analyses with a “K/T body size” taxon set. In these analyses, interordinal splits remained in the Cretaceous.
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Resolution of the early Placental Mammal radiation using Bayesian phylogenetics
Science (New York N.Y.), 2001Co-Authors: William J Murphy, Eduardo Eizirik, Stephen J. O'brien, Emma C. Teeling, Michael J. Stanhope, Ole Madsen, Mark Scally, Christophe J. Douady, Oliver A. Ryder, Wilfried W. De JongAbstract:Molecular phylogenetic studies have resolved Placental Mammals into four major groups, but have not established the full hierarchy of interordinal relationships, including the position of the root. The latter is critical for understanding the early biogeographic history of Placentals. We investigated Placental phylogeny using Bayesian and maximum-likelihood methods and a 16.4-kilobase molecular data set. Interordinal relationships are almost entirely resolved. The basal split is between Afrotheria and other Placentals, at about 103 million years, and may be accounted for by the separation of South America and Africa in the Cretaceous. Crown-group Eutheria may have their most recent common ancestry in the Southern Hemisphere (Gondwana).
Malcolm W. Kennedy - One of the best experts on this subject based on the ideXlab platform.
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Rapid changes in Atlantic grey seal milk from birth to weaning – immune factors and indicators of metabolic strain
Scientific Reports, 2017Co-Authors: Amanda D. Lowe, Sami Bawazeer, David G. Watson, Suzanne Mcgill, Richard J. S. Burchmore, P. P (paddy) Pomeroy, Malcolm W. KennedyAbstract:True seals have the shortest lactation periods of any group of Placental Mammal. Most are capital breeders that undergo short, intense lactations, during which they fast while transferring substantial proportions of their body reserves to their pups, which they then abruptly wean. Milk was collected from Atlantic grey seals ( Halichoerus grypus ) periodically from birth until near weaning. Milk protein profiles matured within 24 hours or less, indicating the most rapid transition from colostrum to mature phase lactation yet observed. There was an unexpected persistence of immunoglobulin G almost until weaning, potentially indicating prolonged trans-intestinal transfer of IgG. Among components of innate immune protection were found fucosyllactose and siallylactose that are thought to impede colonisation by pathogens and encourage an appropriate milk-digestive and protective gut microbiome. These oligosaccharides decreased from early lactation to almost undetectable levels by weaning. Taurine levels were initially high, then fell, possibly indicative of taurine dependency in seals, and progressive depletion of maternal reserves. Metabolites that signal changes in the mother’s metabolism of fats, such as nicotinamide and derivatives, rose from virtual absence, and acetylcarnitines fell. It is therefore possible that indicators of maternal metabolic strain exist that signal the imminence of weaning.
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prolonged transition time between colostrum and mature milk in a bear the giant panda ailuropoda melanoleuca
Royal Society Open Science, 2015Co-Authors: Kate Griffiths, David G. Watson, Hairui Wang, Zhihe Zhang, L Zhang, Tong Zhang, Richard Burchmore, Kati I Loeffler, Malcolm W. KennedyAbstract:Bears produce the most altricial neonates of any Placental Mammal. We hypothesized that the transition from colostrum to mature milk in bears reflects a temporal and biochemical adaptation for altricial development and immune protection. Comparison of bear milks with milks of other eutherians yielded distinctive protein profiles. Proteomic and metabolomic analysis of serial milk samples collected from six giant pandas showed a prolonged transition from colostrum to main-phase lactation over approximately 30 days. Particularly striking are the persistence or sequential appearance of adaptive and innate immune factors. The endurance of immunoglobulin G suggests an unusual duration of trans-intestinal absorption of maternal antibodies, and is potentially relevant to the underdeveloped lymphoid system of giant panda neonates. Levels of certain milk oligosaccharides known to exert anti-microbial activities and/or that are conducive to the development of neonatal gut microbiomes underwent an almost complete changeover around days 20–30 postpartum, coincident with the maturation of the protein profile. A potential metabolic marker of starvation was detected, the prominence of which may reflect the natural postpartum period of anorexia in giant panda mothers. Early lactation in giant pandas, and possibly in other ursids, appears to be adapted for the unique requirements of unusually altricial eutherian neonates.