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Chris T Amemiya - One of the best experts on this subject based on the ideXlab platform.
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SCPP genes in the Coelacanth: tissue mineralization genes shared by sarcopterygians.
Journal of experimental zoology. Part B Molecular and developmental evolution, 2013Co-Authors: Kazuhiko Kawasaki, Chris T AmemiyaAbstract:The Coelacanth is the basal-most extant sarcopterygian that has teeth and tooth-like structures, comprising bone, dentin, and enamel or enameloid. Formation of these tissues involves many members of the secretory calcium-binding protein (SCPP) family. In tetrapods, acidic-residue-rich SCPPs are used in mineralization of bone and dentin, whereas Pro/Gln-rich SCPPs participate in enamel formation. Teleosts also employ many SCPPs for tissue mineralization. Nevertheless, the repertoire of SCPPs is largely different in teleosts and tetrapods; hence, filling this gap would be critical to elucidate early evolution of mineralized tissues in osteichthyans. In the present study, we searched for SCPP genes in the Coelacanth genome and identified 11, of which two have clear orthologs in both tetrapods and teleosts, seven only in tetrapods, and two in neither of them. Given the divergence times of these vertebrate lineages, our discovery of this many SCPP genes shared between the Coelacanth and tetrapods, but not with teleosts, suggests a complicated evolutionary scheme of SCPP genes in early osteichthyans. Our investigation also revealed both conserved and derived characteristics of SCPPs in the Coelacanth and other vertebrates. Notably, acidic SCPPs independently evolved various acidic repeats in different lineages, while maintaining high acidity, presumably important for interactions with calcium. Furthermore, the three Pro/Gln-rich SCPP genes, required for mineralizing enamel matrix and confirmed only in tetrapods, were all identified in the Coelacanth, strongly suggesting that enamel is equivalent in the Coelacanth and tetrapods. This finding corroborates the previous proposition that true enamel evolved much earlier than the origin of tetrapods. J. Exp. Zool. (Mol. Dev. Evol.) 322B: 390–402, 2014. © 2013 Wiley Periodicals, Inc.
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The African Coelacanth genome provides insights into tetrapod evolution
Nature, 2013Co-Authors: Chris T Amemiya, Jessica Alföldi, Alison P. Lee, Shaohua Fan, Hervé Philippe, Iain Maccallum, Ingo Braasch, Tereza Manousaki, Igor Schneider, Nicolas RohnerAbstract:The discovery of a living Coelacanth specimen in 1938 was remarkable, as this lineage of lobe-finned fish was thought to have become extinct 70 million years ago. The modern Coelacanth looks remarkably similar to many of its ancient relatives, and its evolutionary proximity to our own fish ancestors provides a glimpse of the fish that first walked on land. Here we report the genome sequence of the African Coelacanth, Latimeria chalumnae. Through a phylogenomic analysis, we conclude that the lungfish, and not the Coelacanth, is the closest living relative of tetrapods. Coelacanth protein-coding genes are significantly more slowly evolving than those of tetrapods, unlike other genomic features. Analyses of changes in genes and regulatory elements during the vertebrate adaptation to land highlight genes involved in immunity, nitrogen excretion and the development of fins, tail, ear, eye, brain and olfaction. Functional assays of enhancers involved in the fin-to-limb transition and in the emergence of extra-embryonic tissues show the importance of the Coelacanth genome as a blueprint for understanding tetrapod evolution.
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a living fossil in the genome of a living fossil harbinger transposons in the Coelacanth genome
Molecular Biology and Evolution, 2012Co-Authors: Joshua J Smith, Kenta Sumiyama, Chris T AmemiyaAbstract:Emerging data from the Coelacanth genome are beginning to shed light on the origin and evolution of tetrapod genes and noncoding elements. Of particular relevance is the realization that Coelacanth retains active copies of transposable elements that once served as raw material for the evolution of new functional sequences in the vertebrate lineage. Recognizing the evolutionary significance of Coelacanth genome in this regard, we employed an ab initio search strategy to further classify its repetitive complement. This analysis uncovered a class of interspersed elements (Latimeria Harbinger 1-LatiHarb1) that is a major contributor to Coelacanth genome structure and gene content (∼1% to 4% or the genome). Sequence analyses indicate that 1) each ∼8.7 kb LatiHarb1 element contains two coding regions, a transposase gene and a gene whose function is as yet unknown (MYB-like) and 2) copies of LatiHarb1 retain biological activity in the Coelacanth genome. Functional analyses verify transcriptional and enhancer activities of LatiHarb1 in vivo and reveal transcriptional decoupling that could permit MYB-like genes to play functional roles not directly linked to transposition. Thus, LatiHarb1 represents the first known instance of a harbinger-superfamily transposon with contemporary activity in a vertebrate genome. Analyses of LatiHarb1 further corroborate the notion that exaptation of anciently active harbinger elements gave rise to at least two vertebrate genes (harbi1 and naif1) and indicate that the vertebrate gene tsnare1 also traces its ancestry to this transposon superfamily. Based on our analyses of LatiHarb1, we speculate that several functional features of harbinger elements may predispose the transposon superfamily toward recurrent exaptive evolution of cellular coding genes. In addition, these analyses further reinforce the broad utility of the Coelacanth genome and other "outgroup" genomes in understanding the ancestry and evolution of vertebrate genes and genomes.
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Complete HOX cluster characterization of the Coelacanth provides further evidence for slow evolution of its genome
Proceedings of the National Academy of Sciences of the United States of America, 2010Co-Authors: Chris T Amemiya, Thomas P. Powers, Sonja J. Prohaska, Jane Grimwood, Jeremy Schmutz, Mark Dickson, Tsutomu Miyake, Michael A. Schoenborn, Richard M. Myers, Francis H. RuddleAbstract:The living Coelacanth is a lobe-finned fish that represents an early evolutionary departure from the lineage that led to land vertebrates, and is of extreme interest scientifically. It has changed very little in appearance from fossilized Coelacanths of the Cretaceous (150 to 65 million years ago), and is often referred to as a “living fossil.” An important general question is whether long-term stasis in morphological evolution is associated with stasis in genome evolution. To this end we have used targeted genome sequencing for acquiring 1,612,752 bp of high quality finished sequence encompassing the four HOX clusters of the Indonesian Coelacanth Latimeria menadoensis. Detailed analyses were carried out on genomic structure, gene and repeat contents, conserved noncoding regions, and relative rates of sequence evolution in both coding and noncoding tracts. Our results demonstrate conclusively that the Coelacanth HOX clusters are evolving comparatively slowly and that this taxon should serve as a viable outgroup for interpretation of the genomes of tetrapod species.
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sequence and organization of Coelacanth neurohypophysial hormone genes evolutionary history of the vertebrate neurohypophysial hormone gene locus
BMC Evolutionary Biology, 2008Co-Authors: Paichung Gwee, Chris T Amemiya, Sydney Brenner, Byrappa VenkateshAbstract:The mammalian neurohypophysial hormones, vasopressin and oxytocin are involved in osmoregulation and uterine smooth muscle contraction respectively. All jawed vertebrates contain at least one homolog each of vasopressin and oxytocin whereas jawless vertebrates contain a single neurohypophysial hormone called vasotocin. The vasopressin homolog in non-mammalian vertebrates is vasotocin; and the oxytocin homolog is mesotocin in non-eutherian tetrapods, mesotocin and [Phe2]mesotocin in lungfishes, and isotocin in ray-finned fishes. The genes encoding vasopressin and oxytocin genes are closely linked in the human and rodent genomes in a tail-to-tail orientation. In contrast, their pufferfish homologs (vasotocin and isotocin) are located on the same strand of DNA with isotocin gene located upstream of vasotocin gene separated by five genes, suggesting that this locus has experienced rearrangements in either mammalian or ray-finned fish lineage, or in both lineages. The Coelacanths occupy a unique phylogenetic position close to the divergence of the mammalian and ray-finned fish lineages. We have sequenced a Coelacanth (Latimeria menadoensis) BAC clone encompassing the neurohypophysial hormone genes and investigated the evolutionary history of the vertebrate neurohypophysial hormone gene locus within a comparative genomics framework. The Coelacanth contains vasotocin and mesotocin genes like non-mammalian tetrapods. The Coelacanth genes are present on the same strand of DNA with no intervening genes, with the vasotocin gene located upstream of the mesotocin gene. Nucleotide sequences of the second exons of the two genes are under purifying selection implying a regulatory function. We have also analyzed the neurohypophysial hormone gene locus in the genomes of opossum, chicken and Xenopus tropicalis. The opossum contains two tandem copies of vasopressin and mesotocin genes. The vasotocin and mesotocin genes in chicken and Xenopus, and the vasopressin and mesotocin genes in opossum are linked tail-to-head similar to their orthologs in Coelacanth and unlike their homologs in human and rodents. Our results indicate that the neurohypophysial hormone gene locus has experienced independent rearrangements in both placental mammals and teleost fishes. The Coelacanth genome appears to be more stable than mammalian and teleost fish genomes. As such, it serves as a valuable outgroup for studying the evolution of mammalian and teleost fish genomes.
Jean-nicolas Volff - One of the best experts on this subject based on the ideXlab platform.
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The Coelacanth: Can a “living fossil” have active transposable elements in its genome?
Mobile genetic elements, 2015Co-Authors: Magali Naville, Domitille Chalopin, Didier Casane, Patrick Laurenti, Jean-nicolas VolffAbstract:The Coelacanth has long been regarded as a "living fossil," with extant specimens looking very similar to fossils dating back to the Cretaceous period. The hypothesis of a slowly or even not evolving genome has been proposed to account for this apparent morphological stasis. While this assumption seems to be sustained by different evolutionary analyses on protein-coding genes, recent studies on transposable elements have provided more conflicting results. Indeed, the Coelacanth genome contains many transposable elements and has been shaped by several major bursts of transposition during evolution. In addition, comparison of orthologous genomic regions from the genomes of the 2 extant Coelacanth species L. chalumnae and L. menadoensis revealed multiple species-specific insertions, indicating transposable element recent activity and contribution to post-speciation genome divergence. These observations, which do not support the genome stasis hypothesis, challenge either the impact of transposable elements on organismal evolution or the status of the Coelacanth as a "living fossil." Closer inspection of fossil and molecular data indicate that, even if Coelacanths might evolve more slowly than some other lineages due to demographic and/or ecological factors, this variation is still in the range of a "non-fossil" vertebrate species.
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the Coelacanth can a living fossil have active transposable elements in its genome
Mobile genetic elements, 2015Co-Authors: Magali Naville, Domitille Chalopin, Didier Casane, Patrick Laurenti, Jean-nicolas VolffAbstract:The Coelacanth has long been regarded as a "living fossil," with extant specimens looking very similar to fossils dating back to the Cretaceous period. The hypothesis of a slowly or even not evolving genome has been proposed to account for this apparent morphological stasis. While this assumption seems to be sustained by different evolutionary analyses on protein-coding genes, recent studies on transposable elements have provided more conflicting results. Indeed, the Coelacanth genome contains many transposable elements and has been shaped by several major bursts of transposition during evolution. In addition, comparison of orthologous genomic regions from the genomes of the 2 extant Coelacanth species L. chalumnae and L. menadoensis revealed multiple species-specific insertions, indicating transposable element recent activity and contribution to post-speciation genome divergence. These observations, which do not support the genome stasis hypothesis, challenge either the impact of transposable elements on organismal evolution or the status of the Coelacanth as a "living fossil." Closer inspection of fossil and molecular data indicate that, even if Coelacanths might evolve more slowly than some other lineages due to demographic and/or ecological factors, this variation is still in the range of a "non-fossil" vertebrate species.
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Interspecies insertion polymorphism analysis reveals recent activity of transposable elements in extant Coelacanths.
PloS one, 2014Co-Authors: Magali Naville, Domitille Chalopin, Jean-nicolas VolffAbstract:Coelacanths are lobe-finned fish represented by two extant species, Latimeria chalumnae in South Africa and Comoros and L. menadoensis in Indonesia. Due to their intermediate phylogenetic position between ray-finned fish and tetrapods in the vertebrate lineage, they are of great interest from an evolutionary point of view. In addition, extant specimens look similar to 300 million-year-old fossils; because of their apparent slowly evolving morphology, Coelacanths have been often described as « living fossils ». As an underlying cause of such a morphological stasis, several authors have proposed a slow evolution of the Coelacanth genome. Accordingly, sequencing of the L. chalumnae genome has revealed a globally low substitution rate for protein-coding regions compared to other vertebrates. However, genome and gene evolution can also be influenced by transposable elements, which form a major and dynamic part of vertebrate genomes through their ability to move, duplicate and recombine. In this work, we have searched for evidence of transposition activity in Coelacanth genomes through the comparative analysis of orthologous genomic regions from both Latimeria species. Comparison of 5.7 Mb (0.2%) of the L. chalumnae genome with orthologous Bacterial Artificial Chromosome clones from L. menadoensis allowed the identification of 27 species-specific transposable element insertions, with a strong relative contribution of CR1 non-LTR retrotransposons. Species-specific homologous recombination between the long terminal repeats of a new Coelacanth endogenous retrovirus was also detected. Our analysis suggests that transposon activity is responsible for at least 0.6% of genome divergence between both Latimeria species. Taken together, this study demonstrates that Coelacanth genomes are not evolutionary inert: they contain recently active transposable elements, which have significantly contributed to post-speciation genome divergence in Latimeria.
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Evolutionary active transposable elements in the genome of the Coelacanth.
Journal of experimental zoology. Part B Molecular and developmental evolution, 2013Co-Authors: Domitille Chalopin, Axel Meyer, Manfred Schartl, Shaohua Fan, Oleg Simakov, Jean-nicolas VolffAbstract:The apparent morphological stasis in the lineage of the Coelacanth, which has been called a “living fossil” by many, has been suggested to be causally related to a slow evolution of its genome, with strongly reduced activity of transposable elements (TEs). Analysis of the African Coelacanth showed thatatleast25%ofitsgenomeisconstitutedoftransposable elementsincludingretrotransposons, endogenous retroviruses and DNA transposons, with a strong predominance of non‐Long Terminal Repeat (non‐LTR) retrotransposons. The Coelacanth genome has been shaped by four major general bursts of transposition during evolution, with major contributions of LINE1, LINE2, CR1, and Deu non‐LTR retrotransposons. Many transposable elements are expressed in different tissues and might be active. The number of TE families in Coelacanth, but also in lungfish, is lower than in teleost fish, but is higher than in chicken and human. This observation is in agreement with the hypothesis of a sequential elimination of many TE families in the sarcopterygian lineage during evolution.Takentogether,ouranalysisindicatesthattheCoelacanthcontainsmoreTEfamiliesthan birds and mammals, and that these elements have been active during the evolution of the Coelacanth lineage. Hence, at the level of transposable element activity, the Coelacanth genome does not appear to evolve particularly slowly.
Gael Clement - One of the best experts on this subject based on the ideXlab platform.
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A microanatomical and histological study of the scales of the Devonian sarcopterygian Miguashaia bureaui and the evolution of the squamation in Coelacanths.
Journal of anatomy, 2021Co-Authors: Jorge Mondéjar-fernández, Gael Clement, Richard Cloutier, François J. Meunier, Michel LaurinAbstract:Coelacanths have traditionally been described as morphologically conservative throughout their long evolutionary history, which spans more than 400 million years. After an initial burst during the Devonian, a morphological stasis was long thought to have prevailed since the Carboniferous, as shown by the extant Latimeria. New fossil discoveries have challenged this view, with punctual and sometimes unusual departures from the general Coelacanth Bauplan. The dermal skeleton is considered to represent one, if not the main, example of morphological stasis in Coelacanth evolution and as a consequence, has remained poorly surveyed. The lack of palaeohistological data on the dermoskeleton has resulted in a poor understanding of the early establishment and evolution of the Coelacanth squamation. Here we describe the scales of Miguashaia bureaui from the Upper Devonian of Miguasha, Québec (Canada), revealing histological data for a Palaeozoic Coelacanth in great detail and adding to our knowledge on the dermal skeleton of sarcopterygians. Miguashaia displays rounded scales ornamented by tubercules and narrow ridges made of dentine and capped with enamel. At least two generations of superimposed odontodes occur, which is reminiscent of the primitive condition of stem osteichthyans like Andreolepis or Lophosteus, and onychodonts like Selenodus. The middle vascular layer is well developed and shows traces of osteonal remodelling. The basal plate consists of a fully mineralised lamellar bone with a repetitive rotation pattern every five layers indicating a twisted plywood-like arrangement of the collagen plies. Comparisons with the extant Latimeria and other extinct taxa show that these features are consistently conserved across Coelacanth evolution with only minute changes in certain taxa. The morphological and histological features displayed in the scales of Miguashaia enable us to draw a comprehensive picture of the onset of the Coelacanth squamation and to propose and discuss evolutionary scenarios for the Coelacanth dermoskeleton.
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Development and growth of the pectoral girdle and fin skeleton in the extant Coelacanth Latimeria chalumnae
Journal of Anatomy, 2019Co-Authors: Rohan Mansuit, Hugo Dutel, Gael Clement, Marc Herbin, Anthony Herrel, Paul Tafforeau, Mathieu SantinAbstract:The monobasal pectoral fins of living Coelacanths and lungfishes are homologous to the forelimbs of tetrapods and are thus critical to investigate the origin thereof. However, it remains unclear whether the similarity in the asymmetrical endoskeletal arrangement of the pectoral fins of Coelacanths reflects the evolution of the pectoral appendages in sarcopterygians. Here, we describe for the first time the development of the pectoral fin and shoulder girdle in the extant Coelacanth Latimeria chalumnae, based on the tomographic acquisition of a growth series. The pectoral girdle and pectoral fin endoskeleton are formed early in development with a radially outward growth of the endoskeletal elements. The visualization of the pectoral girdle during development shows a reorientation of the girdle between the fetus and pup 1 stages, creating a contact between the scapulocoracoids and the clavicles in the ventro‐medial region. Moreover, we observed a splitting of the pre‐ and post‐axial cartilaginous plates in respectively pre‐axial radials and accessory elements on one hand, and in post‐axial accessory elements on the other hand. However, the mechanisms involved in the splitting of the cartilaginous plates appear different from those involved in the formation of radials in actinopterygians. Our results show a proportional reduction of the proximal pre‐axial radial of the fin, rendering the external morphology of the fin more lobe‐shaped, and a spatial reorganization of elements resulting from the fragmentation of the two cartilaginous plates. Latimeria development hence supports previous interpretations of the asymmetrical pectoral fin skeleton as being plesiomorphic for Coelacanths and sarcopterygians.
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The homology and function of the lung plates in extant and fossil Coelacanths
Scientific reports, 2017Co-Authors: Camila Cupello, Philippe Janvier, Gael Clement, Marc Herbin, François J. Meunier, Paulo M. BritoAbstract:The presence of a pulmonary organ that is entirely covered by true bone tissue and fills most of the abdominal cavity is hitherto unique to fossil actinistians. Although small hard plates have been recently reported in the lung of the extant Coelacanth Latimeria chalumnae, the homology between these hard structures in fossil and extant forms remained to be demonstrated. Here, we resolve this question by reporting the presence of a similar histological pattern–true cellular bone with star-shaped osteocytes, and a globular mineralisation with radiating arrangement–in the lung plates of two fossil Coelacanths (Swenzia latimerae and Axelrodichthys araripensis) and the plates that surround the lung of the most extensively studied extant Coelacanth species, L. chalumnae. The point-for-point structural similarity of the plates in extant and fossil Coelacanths supports their probable homology and, consequently, that of the organ they surround. Thus, this evidence questions the previous interpretations of the fatty organ as a component of the pulmonary complex of Latimeria.
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Allometric growth in the extant Coelacanth lung during ontogenetic development
Nature communications, 2015Co-Authors: Camila Cupello, Philippe Janvier, Hugo Dutel, Marc Herbin, Paulo M. Brito, François J. Meunier, Gael ClementAbstract:Coelacanths are lobe-finned fishes known from the Devonian to Recent that were long considered extinct, until the discovery of two living species in deep marine waters of the Mozambique Channel and Sulawesi. Despite extensive studies, the pulmonary system of extant Coelacanths has not been fully investigated. Here we confirm the presence of a lung and discuss its allometric growth in Latimeria chalumnae, based on a unique ontogenetic series. Our results demonstrate the presence of a potentially functional, well-developed lung in the earliest known Coelacanth embryo, and its arrested growth at later ontogenetic stages, when the lung is clearly vestigial. The parallel development of a fatty organ for buoyancy control suggests a unique adaptation to deep-water environments. Furthermore, we provide the first evidence for the presence of small, hard, flexible plates around the lung in L. chalumnae, and consider them homologous to the plates of the ‘calcified lung' of fossil Coelacanths.
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First occurrence of a mawsoniid Coelacanth in the Early Jurassic of Europe
Journal of Vertebrate Paleontology, 2015Co-Authors: Hugo Dutel, Marc Herbin, Gael ClementAbstract:ABSTRACT—Coelacanths form a clade of sarcopterygian fishes (lobe-finned vertebrates) that today is represented by a single genus, Latimeria. This genus belongs to a lineage of marine Coelacanths, the latimeriids, whose fossils are common in the Jurassic and the Cretaceous deposits of Europe and North America. During the same periods, another lineage of fresh/brackish water Coelacanths, the mawsoniids, occurred in South America, Africa, and Madagascar. Mawsoniids are supposed to have originated during the Triassic in North America and were assumed to have subsequently dispersed to South America during the Jurassic, before reaching western Africa during the Early Cretaceous. Previous hypotheses advocated that mawsoniid Coelacanths reached Europe during the Late Cretaceous, suggesting the dispersal of freshwater organisms from Africa to Europe during this period. We here reevaluate this scenario based on the reexamination of the Coelacanth Trachymetopon from the Early Jurassic of Germany. Although this genus...
Benjamin P. Ngatunga - One of the best experts on this subject based on the ideXlab platform.
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Coelacanth genomes reveal signatures for evolutionary transition from water to land
Genome Research, 2013Co-Authors: Masato Nikaido, Hideki Noguchi, Miki Okuno, Mitsuto Aibara, Hidenori Nishihara, Hikoyu Suzuki, Rei Kajitani, Yutaka Suzuki, Atsushi Toyoda, Benjamin P. NgatungaAbstract:Coelacanths are known as ‘‘living fossils,’’ as they show remarkable morphological resemblance to the fossil record and belong to the most primitive lineage of living Sarcopterygii (lobe-finned fishes and tetrapods). Coelacanths may be key to elucidating the tempo and mode of evolution from fish to tetrapods. Here, we report the genome sequences of five Coelacanths, including four Latimeria chalumnaeindividuals (three specimens from Tanzania and onefrom Comoros) andone L. menadoensis individual from Indonesia. These sequences cover two African breeding populations and two known extant Coelacanth species. The genome is ~2.74 Gbp and contains a high proportion (~60%) of repetitive elements. The genetic diversity among the individuals was extremely low, suggesting a small population size and/or a slow rate of evolution. We found a substantial number of genes that encode olfactory and pheromone receptors with features characteristic of tetrapod receptors for the detection of airborne ligands. We also found that limb enhancers of bmp7 and gli3, both of which areessentialforlimbformation,areconservedbetweenCoelacanthandtetrapods,butnotray-finnedfishes.Weexpectthat some tetrapod-like genes may have existed early in the evolution of primitive Sarcopterygii and were later co-opted to adapt to terrestrial environments. These Coelacanth genomes will provide a cornerstone for studies to elucidate how ancestral aquatic vertebrates evolved into terrestrial animals.
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Extremely slow rate of evolution in the HOX cluster revealed by comparison between Tanzanian and Indonesian Coelacanths
Gene, 2012Co-Authors: Koichiro Higasa, Mitsuto Aibara, Hidenori Nishihara, Benjamin P. Ngatunga, Hikoyu Suzuki, Yutaka Suzuki, Masato Nikaido, Taro Saito, Jun Yoshimura, Hassan KalomboAbstract:Abstract Coelacanths are known as “living fossils” because their morphology has changed very little from that in the fossil record. To elucidate why Coelacanths have evolved so slowly is thus of primary importance in evolutionary biology. In the present study, we determined the entire sequence of the HOX cluster of the Tanzanian Coelacanth (Latimeria chalumnae) and compared it with that of the Indonesian Coelacanth (L. menadoensis), which was available in the literature. The most intriguing result was the extremely small genetic divergence between the two Coelacanths. The synonymous divergence of the HOX coding region between the two Coelacanths was estimated to be 0.07%, which is ~ 11-fold smaller than that of human–chimp. When we applied the estimated divergence time of the two Coelacanths of 6 million years ago (MYA) and 30 MYA, which were proposed in independent mitochondrial DNA analyses, the synonymous substitution rate of the Coelacanth HOX cluster was estimated to be ~ 11-fold and 56-fold smaller than that of human–chimp, respectively. Thus, the present study implies that the reduction of the nucleotide substitution rate in Coelacanth HOX genes may account for the conservation of Coelacanth morphology during evolution.
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Population divergence in East African Coelacanths
Current biology : CB, 2012Co-Authors: Kathrin P. Lampert, Benjamin P. Ngatunga, Hans Fricke, Karen Hissmann, Jürgen Schauer, Katrin Blassmann, Manfred SchartlAbstract:The Coelacanth, Latimeria chalumnae, occurs at the Eastern coast of Africa from South Africa up to Kenya. It is often referred to as a living fossil mainly because of its nearly unchanged morphology since the Middle Devonian. As it is a close relative to the last common ancestor of fish and tetrapods, molecular studies mostly focussed on their phylogenetic relationships. We now present a population genetic study based on 71 adults from the whole known range of the species. Despite an overall low genetic diversity, there is evidence for divergence of local populations. We assume that originally the Coelacanths at the East African Coast derived from the Comoros population, but have since then diversified into additional independent populations: one in South Africa and another in Tanzania. Unexpectedly, we find a split of the Comoran Coelacanths into two sympatric subpopulations. Despite its undeniably slow evolutionary rate, the Coelacanth still diversifies and is therefore able to adapt to new environmental conditions.
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Genetically distinct Coelacanth population off the northern Tanzanian coast
Proceedings of the National Academy of Sciences of the United States of America, 2011Co-Authors: Masato Nikaido, Mitsuto Aibara, Benjamin P. Ngatunga, Takeshi Sasaki, J.j. Emerson, Semvua I. Mzighani, Yohana L. Budeba, Masamitsu Iwata, Yoshitaka AbeAbstract:Since the sensational discovery of a living Coelacanth off the east coast of South Africa, the geographic distribution of viable Coelacanth populations has been a subject of debate. In the past, the Coelacanths off the African mainland were thought to be strays from the Comoros because most Coelacanths captured were caught in the waters surrounding the Comoros archipelagos. However, in recent years, a large number of Coelacanths were captured off the coast of Tanzania, including nine living specimens observed in a remotely operated vehicles survey. Thus, it is possible that there is a reproducing population inhabiting waters off the Tanzania coast. We have sequenced the complete mitochondrial genomes of 21 Tanzanian and 2 Comoran Coelacanths and analyzed these sequences together with two additional full mitochondrial genomes and 47 d-loop sequences from the literature. We found that the Coelacanth population off the northern Tanzanian coast is genetically differentiated from those of the southern Tanzania coast and the Comoros, whereas no significant genetic differentiation occurs between the latter two localities. The differentiation between the northern and southern Tanzanian coast populations is consistent with the hypothesis that the existence of northward-flowing ocean current along the Tanzanian coast may reduce or prevent gene flow from the northern to the southern population. Finally, we estimated that the population localized to the southern Tanzanian coast and the Comoros diverged from other Coelacanths at least 200,000 y ago. These results indicate that the Coelacanths off the northern Tanzania coast are not strays but a genetically distinct group. Our study provides important information for the conservation of this threatened “living fossil.”
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Mitogenomic analysis for Coelacanths (Latimeria chalumnae) caught in Tanzania.
Gene, 2006Co-Authors: Takeshi Sasaki, Benjamin P. Ngatunga, Tetsu Sato, Seiko Miura, Philip O.j. Bwathondi, Norihiro OkadaAbstract:In recent years, a large number of individuals of the species Latimeria chalumnae, one of the living fossil Coelacanths, have been landed off the coast of Tanzania. Although L. chalumnae specimens have also been landed at other localities in the western Indian Ocean, so far, viable populations of this species have been identified only at two localities, Comoros and South Africa. Therefore, the recent active catch off Tanzania suggests a new habitat for L. chalumnae. To examine the genetic background of the Tanzanian fish, we analyzed complete mtDNA sequences of two Tanzanian individuals (Kigombe-9 and Songo Mnara-1) collected from the north and south coasts of Tanzania. Using the recently reported criteria for six haplotypes established in a population genetic study for Coelacanths living in the western Indian Ocean [Schartl, M., Hornung, U., Hissman, K., Schauer, J., Fricke, H., 2005. Relatedness among east African Coelacanths. Nature 435, 901.], we characterized Songo Mnara-1 as haplotype 1 and Kigombe-9 as haplotype 5. We suggest that the Songo Mnara specimen is a member of the Comoran group, but was swept away by the South Equatorial current. The individual from Kigombe may be a member of an undiscovered population that exists near the boundary between Tanzania and Kenya. Further analysis using more than 19 individuals recently captured off the north coast of Tanzania will reveal whether a new population exists there. Our sequence data suggest additional variable sites in the mtDNA sequence that may define the population structure of Coelacanths in the western Indian Ocean and also raise the possibility that the previously published Comoran Coelacanth mtDNA sequence contains several critical errors including base changes and indels.
Hans Fricke - One of the best experts on this subject based on the ideXlab platform.
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Population divergence in East African Coelacanths
Current biology : CB, 2012Co-Authors: Kathrin P. Lampert, Benjamin P. Ngatunga, Hans Fricke, Karen Hissmann, Jürgen Schauer, Katrin Blassmann, Manfred SchartlAbstract:The Coelacanth, Latimeria chalumnae, occurs at the Eastern coast of Africa from South Africa up to Kenya. It is often referred to as a living fossil mainly because of its nearly unchanged morphology since the Middle Devonian. As it is a close relative to the last common ancestor of fish and tetrapods, molecular studies mostly focussed on their phylogenetic relationships. We now present a population genetic study based on 71 adults from the whole known range of the species. Despite an overall low genetic diversity, there is evidence for divergence of local populations. We assume that originally the Coelacanths at the East African Coast derived from the Comoros population, but have since then diversified into additional independent populations: one in South Africa and another in Tanzania. Unexpectedly, we find a split of the Comoran Coelacanths into two sympatric subpopulations. Despite its undeniably slow evolutionary rate, the Coelacanth still diversifies and is therefore able to adapt to new environmental conditions.
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the population biology of the living Coelacanth studied over 21 years
Marine Biology, 2011Co-Authors: Hans Fricke, Raphael Plante, Karen Hissmann, Rainer Froese, Jiirgen Schauer, Sebastian FrickeAbstract:Between 1986 and 2009 nine submersible and remote-operated vehicle expeditions were carried out to study the population biology of the Coelacanth Latimeria chalumnae in the Comoro Islands, located in the western Indian Ocean. Latimeria live in large overlapping home ranges that can be occupied for as long as 21 years. Most individuals are confined to relatively small home ranges, resting in the same caves during the day. One hundred and forty five Coelacanths are individually known, and we estimate the total population size of Grande Comore as approximately 300–400 adult individuals. The local population inhabiting a census area along an 8-km section of coastline remained stable for at least 18 years. Using LASER-assisted observations, we recorded length frequencies between 100 and 200 cm total length and did not encounter smaller-bodied individuals (<100 cm total length). It appears that Coelacanth recruitment in the observation areas occur mainly by immigrating adults. We estimate that the mean numbers of deaths and newcomers are 3–4 individuals per year, suggesting that longevity may exceed 100 years. The domestic fishery represents a threat to the long-term survival of Coelacanths in the study area. Recent changes in the local fishery include a decrease in the abundance of the un-motorized canoes associated with exploitation of Coelacanths and an increase in motorized canoes. Exploitation rates have fallen in recent years, and by 2000, had fallen to lowest ever reported. Finally, future fishery developments are discussed.
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The population biology of the living Coelacanth studied over 21 years
Marine Biology, 2011Co-Authors: Hans Fricke, Raphael Plante, Karen Hissmann, Rainer Froese, Jiirgen Schauer, Sebastian FrickeAbstract:Between 1986 and 2009 nine submersible and remote-operated vehicle expeditions were carried out to study the population biology of the Coelacanth Latimeria chalumnae in the Comoro Islands, located in the western Indian Ocean. Latimeria live in large overlapping home ranges that can be occupied for as long as 21 years. Most individuals are confined to relatively small home ranges, resting in the same caves during the day. One hundred and forty five Coelacanths are individually known, and we estimate the total population size of Grande Comore as approximately 300–400 adult individuals. The local population inhabiting a census area along an 8-km section of coastline remained stable for at least 18 years. Using LASER-assisted observations, we recorded length frequencies between 100 and 200 cm total length and did not encounter smaller-bodied individuals (
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Population Monitoring of the Coelacanth (Latimeria chalumnae)
Conservation Biology, 2008Co-Authors: Karen Hissmann, Hans Fricke, Jürgen SchauerAbstract:In 1991 the population size of the Coelacanth ( Latimeria chalumnae) on Grande Comore Island, Western Indian Ocean, was estimated at 230–650 individuals, based on counts of individually recognized fish in an 8-km stretch of coastline. This census area represents about 9% of the total suitable habitat at the island. Counts in the same area in 1994 indicated a reduction of sighted Coelacanths of about 30%. Additional surveys in 1995 suggested a total Coelacanth population of less than 300 individuals. The local artisanal fishery is probably responsible for the observed decline. The survival of the Coelacanth seems to be severely threatened if fishing pressure is not reduced. Conservation measures should focus on providing local fishermen with fishing alternatives. Monitoreo Poblacional del Celacanto (Latimeria chalumnae) En 1991 el tamano poblacional del celacanto, Latimeria chalumnae en Grande Comore, al Oeste del Oceano Indico, fue estimada de 230 a 650 individuos, en base a conteos de individuos reconocidos en un estrecho costero de 8 km de longitud. Esta area de censo representa cerca de un 9% del total de habitat adecuado en la isla. Los conteos en la zona en 1994 indicaron una reduccion de celacantos de aproximadamnete un 30%. Estudios adicionales en 1995 sugirieron una poblacion total de menos de 300 individuos. Probablemente la pesqueria artesanal local es responsable de la declinacion observada. La sobrevivencia del celacanto aparenta estar amenazada si la presion por pesca no disminuye. Las medidas de conservacion se deberan enfocar en proveer a los pescadores locales de alternataivas de pesca.
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Coelacanths: a human responsibility
Journal of Fish Biology, 2001Co-Authors: Hans FrickeAbstract:The living Coelacanth Latimeria chalumnae has a unique position in world biodiversity which raises important questions about conservation and ethics. Some relevant details of Coelacanth biology are summarized, including those obtained by direct observation from submersibles. The importance of the Coelacanth for evolutionary theory and palaeontology is shown to be paralleled in cultural, literary and artistic areas of human heritage. Threats to the Comoran Coelacanths from artisanal fishing are described and conservation measures discussed in relation to local customs and economies as well as the promotion of tourism to spread a new awareness and concern for Coelacanths worldwide.