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Baldomero M Olivera - One of the best experts on this subject based on the ideXlab platform.

  • Venom Insulins of Cone Snails Diversify Rapidly and Track Prey Taxa
    Molecular biology and evolution, 2016
    Co-Authors: Helena Safavi-hemami, Mark Yandell, Alexander E. Fedosov, Jason S. Biggs, Patrice Showers Corneli, Jon Seger, Baldomero M Olivera
    Abstract:

    A specialized insulin was recently found in the venom of a fish-hunting cone snail, Conus geographus Here we show that many worm-hunting and snail-hunting cones also express venom insulins, and that this novel gene family has diversified explosively. Cone snails express a highly conserved insulin in their nerve ring; presumably this conventional signaling insulin is finely tuned to the Conus insulin receptor, which also evolves very slowly. By contrast, the venom insulins diverge rapidly, apparently in response to biotic interactions with prey and also possibly the cones' own predators and competitors. Thus, the inwardly directed signaling insulins appear to experience predominantly purifying sele\ction to target an internal receptor that seldom changes, while the outwardly directed venom insulins frequently experience directional selection to target heterospecific insulin receptors in a changing mix of prey, predators and competitors. Prey insulin receptors may often be constrained in ways that prevent their evolutionary escape from targeted venom insulins, if amino-acid substitutions that result in escape also degrade the receptor's signaling functions.

  • High Conopeptide Diversity in Conus tribblei Revealed Through Analysis of Venom Duct Transcriptome Using Two High-Throughput Sequencing Platforms
    Marine Biotechnology, 2015
    Co-Authors: Neda Barghi, Baldomero M Olivera, Gisela P. Concepcion, Arturo O. Lluisma
    Abstract:

    The venom of each species of Conus contains different kinds of pharmacologically active peptides which are mostly unique to that species. Collectively, the ~500–700 species of Conus produce a large number of these peptides, perhaps exceeding 140,000 different types in total. To date, however, only a small fraction of this diversity has been characterized via transcriptome sequencing. In addition, the sampling of this chemical diversity has not been uniform across the different lineages in the genus. In this study, we used high-throughput transcriptome sequencing approach to further investigate the diversity of Conus venom peptides. We chose a species, Conus tribblei , as a representative of a poorly studied clade of Conus . Using the Roche 454 and Illumina platforms, we discovered 136 unique and novel putative conopeptides belonging to 30 known gene superfamilies and 6 new conopeptide groups, the greatest diversity so far observed from a transcriptome. Most of the identified peptides exhibited divergence from the known conopeptides, and some contained cysteine frameworks observed for the first time in cone snails. In addition, several enzymes involved in posttranslational modification of conopeptides and also some proteins involved in efficient delivery of the conopeptides to prey were identified as well. Interestingly, a number of conopeptides highly similar to the conopeptides identified in a phylogenetically distant species, the generalist feeder Conus californicus , were observed. The high diversity of conopeptides and the presence of conopeptides similar to those in C. californicus suggest that C. tribblei may have a broad range of prey preferences.

  • one four or 100 genera a new classification of the cone snails
    Journal of Molluscan Studies, 2015
    Co-Authors: Nicolas Puillandre, Baldomero M Olivera, Thomas F Duda, Christopher P Meyer, Philippe Bouchet
    Abstract:

    We present a new classification for the genus Conus sensu lato (family Conidae), based on molecular phylogenetic analyses of 329 species. This classification departs from both the traditional classification in only one genus and from a recently proposed shell- and radula-based classification scheme that separates members of this group into five families and 115 genera. Roughly 140 genus-group names are available for Recent cone snails. We propose to place all cone snails within a single family (Conidae) containing four genera—Conus, Conasprella, ProfundiConus and CaliforniConus (with Conus alone encompassing about 85% of known species)—based on the clear separation of cone snails into four distinct and well-supported groups/ lineages in molecular phylogenetic analyses. Within Conus and Conasprella, we recognize 57 and 11 subgenera, respectively, that represent well-supported subgroupings within these genera, which we interpret as evidence of intrageneric distinctiveness. We allocate the 803 Recent species of Conidae listed as valid in the World Register of Marine Species into these four genera and 71 subgenera, with an estimate of the confidence for placement of species in these taxonomic categories based on whether molecular or radula and/or shell data were used in these determinations. Our proposed classification effectively departs from previous schemes by (1) limiting the number of accepted genera, (2) retaining the majority of species within the genus Conus and (3) assigning members of these genera to species groups/subgenera to enable the effective communication of these groups, all of which we hope will encourage acceptance of this scheme.

  • modulation of conotoxin structure and function is achieved through a multienzyme complex in the venom glands of cone snails
    Journal of Biological Chemistry, 2012
    Co-Authors: Helena Safavihemami, Baldomero M Olivera, Joanna Gajewiak, Andrew M Steiner, Nicholas A Williamson, Dhana G Gorasia, John A Karas, Anthony W Purcell
    Abstract:

    The oxidative folding of large polypeptides has been investigated in detail; however, comparatively little is known about the enzyme-assisted folding of small, disulfide-containing peptide substrates. To investigate the concerted effect of multiple enzymes on the folding of small disulfide-rich peptides, we sequenced and expressed protein-disulfide isomerase (PDI), peptidyl-prolyl cis-trans isomerase, and immunoglobulin-binding protein (BiP) from Conus venom glands. Conus PDI was shown to catalyze the oxidation and reduction of disulfide bonds in two conotoxins, α-GI and α-ImI. Oxidative folding rates were further increased in the presence of Conus PPI with the maximum effect observed in the presence of both enzymes. In contrast, Conus BiP was only observed to assist folding in the presence of microsomes, suggesting that additional co-factors were involved. The identification of a complex between BiP, PDI, and nascent conotoxins further suggests that the folding and assembly of conotoxins is a highly regulated multienzyme-assisted process. Unexpectedly, all three enzymes contributed to the folding of the ribbon isomer of α-ImI. Here, we identify this alternative disulfide-linked species in the venom of Conus imperialis, providing the first evidence for the existence of a “non-native” peptide isomer in the venom of cone snails. Thus, ER-resident enzymes act in concert to accelerate the oxidative folding of conotoxins and modulate their conformation and function by reconfiguring disulfide connectivities. This study has evaluated the role of a number of ER-resident enzymes in the folding of conotoxins, providing novel insights into the enzyme-guided assembly of these small, disulfide-rich peptides.

  • modulation of conotoxin structure and function is achieved through a multienzyme complex in the venom glands of cone snails
    Journal of Biological Chemistry, 2012
    Co-Authors: Helena Safavihemami, Baldomero M Olivera, Joanna Gajewiak, Andrew M Steiner, Nicholas A Williamson, Dhana G Gorasia, John A Karas, Grzegorz Bulaj, Anthony W Purcell
    Abstract:

    The oxidative folding of large polypeptides has been investigated in detail; however, comparatively little is known about the enzyme-assisted folding of small, disulfide-containing peptide substrates. To investigate the concerted effect of multiple enzymes on the folding of small disulfide-rich peptides, we sequenced and expressed protein-disulfide isomerase (PDI), peptidyl-prolyl cis-trans isomerase, and immunoglobulin-binding protein (BiP) from Conus venom glands. Conus PDI was shown to catalyze the oxidation and reduction of disulfide bonds in two conotoxins, α-GI and α-ImI. Oxidative folding rates were further increased in the presence of Conus PPI with the maximum effect observed in the presence of both enzymes. In contrast, Conus BiP was only observed to assist folding in the presence of microsomes, suggesting that additional co-factors were involved. The identification of a complex between BiP, PDI, and nascent conotoxins further suggests that the folding and assembly of conotoxins is a highly regulated multienzyme-assisted process. Unexpectedly, all three enzymes contributed to the folding of the ribbon isomer of α-ImI. Here, we identify this alternative disulfide-linked species in the venom of Conus imperialis, providing the first evidence for the existence of a "non-native" peptide isomer in the venom of cone snails. Thus, ER-resident enzymes act in concert to accelerate the oxidative folding of conotoxins and modulate their conformation and function by reconfiguring disulfide connectivities. This study has evaluated the role of a number of ER-resident enzymes in the folding of conotoxins, providing novel insights into the enzyme-guided assembly of these small, disulfide-rich peptides.

Thomas F Duda - One of the best experts on this subject based on the ideXlab platform.

  • one four or 100 genera a new classification of the cone snails
    Journal of Molluscan Studies, 2015
    Co-Authors: Nicolas Puillandre, Baldomero M Olivera, Thomas F Duda, Christopher P Meyer, Philippe Bouchet
    Abstract:

    We present a new classification for the genus Conus sensu lato (family Conidae), based on molecular phylogenetic analyses of 329 species. This classification departs from both the traditional classification in only one genus and from a recently proposed shell- and radula-based classification scheme that separates members of this group into five families and 115 genera. Roughly 140 genus-group names are available for Recent cone snails. We propose to place all cone snails within a single family (Conidae) containing four genera—Conus, Conasprella, ProfundiConus and CaliforniConus (with Conus alone encompassing about 85% of known species)—based on the clear separation of cone snails into four distinct and well-supported groups/ lineages in molecular phylogenetic analyses. Within Conus and Conasprella, we recognize 57 and 11 subgenera, respectively, that represent well-supported subgroupings within these genera, which we interpret as evidence of intrageneric distinctiveness. We allocate the 803 Recent species of Conidae listed as valid in the World Register of Marine Species into these four genera and 71 subgenera, with an estimate of the confidence for placement of species in these taxonomic categories based on whether molecular or radula and/or shell data were used in these determinations. Our proposed classification effectively departs from previous schemes by (1) limiting the number of accepted genera, (2) retaining the majority of species within the genus Conus and (3) assigning members of these genera to species groups/subgenera to enable the effective communication of these groups, all of which we hope will encourage acceptance of this scheme.

  • extensive and continuous duplication facilitates rapid evolution and diversification of gene families
    Molecular Biology and Evolution, 2012
    Co-Authors: Dan Chang, Thomas F Duda
    Abstract:

    The origin of novel gene functions through gene duplication, mutation, and natural selection represents one of the mechanisms by which organisms diversify and one of the possible paths leading to adaptation. Nonetheless, the extent, role, and consequences of duplications in the origins of ecological adaptations, especially in the context of species interactions, remain unclear. To explore the evolution of a gene family that is likely linked to species associations, we investigated the evolutionary history of the A-superfamily of conotoxin genes of predatory marine cone snails (Conus species). Members of this gene family are expressed in the venoms of Conus species and are presumably involved in predator–prey associations because of their utility in prey capture. We recovered sequences of this gene family from genomic DNA of four closely related species of Conus and reconstructed the evolutionary history of these genes. Our study is the first to directly recover conotoxin genes from Conus genomes to investigate the evolution of conotoxin gene families. Our results revealed a phenomenon of rapid and continuous gene turnover that is coupled with heightened rates of evolution. This continuous duplication pattern has not been observed previously, and the rate of gene turnover is at least two times higher than estimates from other multigene families. Conotoxin genes are among the most rapidly evolving protein-coding genes in metazoans, a phenomenon that may be facilitated by extensive gene duplications and have driven changes in conotoxin functions through neofunctionalization. Together these mechanisms led to dramatically divergent arrangements of A-superfamily conotoxin genes among closely related species of Conus. Our findings suggest that extensive and continuous gene duplication facilitates rapid evolution and drastic divergence in venom compositions among species, processes that may be associated with evolutionary responses to predator–prey interactions.

  • geographic variation in venom allelic composition and diets of the widespread predatory marine gastropod Conus ebraeus
    PLOS ONE, 2009
    Co-Authors: Thomas F Duda, Dan Chang, Brittany D Lewis, Taehwan Lee
    Abstract:

    Background Members of the predatory gastropod genus Conus use a venom comprised of a cocktail of peptide neurotoxins, termed conotoxins or conopeptides, to paralyze prey and conotoxin gene family members diversify via strong positive selection. Because Conus venoms are used primarily to subdue prey, the evolution of venoms is likely affected by predator-prey interactions.

  • species level phylogeography and evolutionary history of the hyperdiverse marine gastropod genus Conus
    Molecular Phylogenetics and Evolution, 2005
    Co-Authors: Thomas F Duda, Alan J. Kohn
    Abstract:

    Abstract Phylogenetic and paleontological analyses are combined to reveal patterns of species origination and divergence and to define the significance of potential and actual barriers to dispersal in Conus, a species-rich genus of predatory gastropods distributed throughout the world’s tropical oceans. Species-level phylogenetic hypotheses are based on nucleotide sequences from the nuclear calmodulin and mitochondrial 16S rRNA genes of 138 Conus species from the Indo-Pacific, eastern Pacific, and Atlantic Ocean regions. Results indicate that extant species descend from two major lineages that diverged at least 33 mya. Their geographic distributions suggest that one clade originated in the Indo-Pacific and the other in the eastern Pacific + western Atlantic. Impediments to dispersal between the western Atlantic and Indian Oceans and the central and eastern Pacific Ocean may have promoted this early separation of Indo-Pacific and eastern Pacific + western Atlantic lineages of Conus. However, because both clades contain both Indo-Pacific and eastern Pacific + western Atlantic species, migrations must have occurred between these regions; at least four migration events took place between regions at different times. In at least three cases, incursions between regions appear to have crossed the East Pacific Barrier. The paleontological record illustrates that distinct sets of Conus species inhabited the Indo-Pacific, eastern Pacific + western Atlantic, and eastern Atlantic + former Tethys Realm in the Tertiary, as is the case today. The ranges of

  • explosive radiation of cape verde Conus a marine species flock
    Molecular Ecology, 2004
    Co-Authors: Thomas F Duda, Emilio Rolan
    Abstract:

    Nearly 50 species of the marine gastropod genus Conus are restricted to the Cape Verde archipelago. This unusual concentration of endemics within a single set of oceanic islands is extremely uncharacteristic of marine taxa. Here we used phylogenetic analyses of 90 Conus species, including 30 endemics from Cape Verde, to reveal the relationships and origins of the endemic Cape Verde Conus . Results show that these species group in two distinct clades and represent a marine species flock that is restricted to a very narrowly confined geographical area. Species’ originations occurred in exceptionally limited parts of the archipelago and in some cases radiations took place solely within single islands. Finally, comparison of levels of divergence between Cape Verde endemics and other Conus species suggests that the radiation of Conus in Cape Verde occurred during the last few million years.

Lizardo Inicio, Katherine Yuliana - One of the best experts on this subject based on the ideXlab platform.

  • Colonizacion bacteriana en conos de papel utilizados por los estudiantes de estomatologia en sus terapias pulpares
    Universidad Privada Antenor Orrego - UPAO, 2017
    Co-Authors: Lizardo Inicio, Katherine Yuliana
    Abstract:

    Objetive: To determine the bacterial colonizat ion on the paper cones used by stomatology students of the Universidad Privada Antenor Orrego in their endodontic therapies in 2016. Materials and Methods: A prospective, cross-curricular, descriptive and observat ional study was carried out. A total of 290 samples of paper cones collected from a total of 145 stomatology students were evaluated during their endodontic therapies in endodontics I, endodontics II, integral clinic I, integral clinical II and stomatologic internship. Students were asked to let us randomly select 2 paper cones, which were collected after the student would use them to dry their root canal in their endodontic treatment. These cones wer e placed in test tubes containing thioglycollate broth and immediately transferred to the Mult idisciplinary Research Laboratory (LABINM) of the Universidad Privada Antenor Orrego to be incubated at 37 ° C for 16 and 24 hours. An inoculum was then obtained from the medium of each test tube, which was seeded in a petri dish containing blood agar supplemented with 5% percent of human blood and on a MacConkey agar plate respectively. Both plates were then incubated at 37 ° C for 24 hours to check for bacterial growth by observation of bacterial colony forming units. The collected data were expressed in frequencies and percentages using descriptive and inferent ial statist ics, as well as the nonparametric Kruskal Wallis test for the comparison of the groups. Data processing was performed using Excel and IBM SPSS softwares. The results were presented in tables of frequencies and statist ical graphs.Objetivo: Determinar la colonización bacteriana en los conos de papel utilizados por los estudiantes de estomatología de la Universidad Privada Antenor Orrego en sus terapias endodónticas en el año 2016. Materiales y Método: Se realizó un estudio prospectivo, transversal, descriptivo y observacional. Se evaluaron 290 muestras de conos de papel recolectados de un total de 145 estudiantes de estomatología durante la realización de sus terapias endodónticas en las asignaturas de endodoncia I, endodoncia II, clínica integral I, clínica integral II e internado estomatológico. Se solicitó a los estudiantes, nos permitiera escoger al azar 2 conos de papel, los cuáles fueron recolectados en el momento que el estudiante los utilizaría para secar sus conductos radiculares en su tratamiento endodóntico. Dichos conos fueron colocados en tubos de ensayo que contenían caldo tioglicolato, inmediatamente después fueron trasladados al Laboratorio de Investigación Multidisciplinaria (LABINM) de la Universidad Privada Antenor Orrego para ser incubados a 37° C durante 16 y 24 horas. Posteriormente se obtuvo un inóculo del medio de cada tubo de ensayo, el cual se sembró en una placa petri que contenía agar BHI suplementado con 5% de sangre humana y en una placa de agar MacConkey respectivamente. Luego ambas placas se incubaron a 37°C durante 24 horas para verificar si hubo crecimiento bacteriano mediante la observación de unidades formadoras de colonias bacterianas. Los datos recolectados fueron expresados en frecuencias y porcentajes utilizando estadística descriptiva e inferencial, así como también se empleó la prueba no paramétrica Kruskal Wallis para la comparación de los grupos. El procesamiento de los datos se realizó utilizando softwares Excel e IBM SPSS. Los resultados se presentaron en tablas de frecuencias y gráficos estadísticos

  • Colonización bacteriana en conos de papel utilizados por los estudiantes de estomatología en sus terapias pulpares
    Universidad Privada Antenor Orrego - UPAO, 2017
    Co-Authors: Lizardo Inicio, Katherine Yuliana
    Abstract:

    Objetivo: Determinar la colonización bacteriana en los conos de papel utilizados por los estudiantes de estomatología de la Universidad Privada Antenor Orrego en sus terapias endodónticas en el año 2016. Materiales y Método: Se realizó un estudio prospectivo, transversal, descriptivo y observacional. Se evaluaron 290 muestras de conos de papel recolectados de un total de 145 estudiantes de estomatología durante la realización de sus terapias endodónticas en las asignaturas de endodoncia I, endodoncia II, clínica integral I, clínica integral II e internado estomatológico. Se solicitó a los estudiantes, nos permitiera escoger al azar 2 conos de papel, los cuáles fueron recolectados en el momento que el estudiante los utilizaría para secar sus conductos radiculares en su tratamiento endodóntico. Dichos conos fueron colocados en tubos de ensayo que contenían caldo tioglicolato, inmediatamente después fueron trasladados al Laboratorio de Investigación Multidisciplinaria (LABINM) de la Universidad Privada Antenor Orrego para ser incubados a 37° C durante 16 y 24 horas. Posteriormente se obtuvo un inóculo del medio de cada tubo de ensayo, el cual se sembró en una placa petri que contenía agar BHI suplementado con 5% de sangre humana y en una placa de agar MacConkey respectivamente. Luego ambas placas se incubaron a 37°C durante 24 horas para verificar si hubo crecimiento bacteriano mediante la observación de unidades formadoras de colonias bacterianas. Los datos recolectados fueron expresados en frecuencias y porcentajes utilizando estadística descriptiva e inferencial, así como también se empleó la prueba no paramétrica Kruskal Wallis para la comparación de los grupos. El procesamiento de los datos se realizó utilizando softwares Excel e IBM SPSS. Los resultados se presentaron en tablas de frecuencias y gráficos estadísticos.Objetive: To determine the bacterial colonizat ion on the paper cones used by stomatology students of the Universidad Privada Antenor Orrego in their endodontic therapies in 2016. Materials and Methods: A prospective, cross-curricular, descriptive and observat ional study was carried out. A total of 290 samples of paper cones collected from a total of 145 stomatology students were evaluated during their endodontic therapies in endodontics I, endodontics II, integral clinic I, integral clinical II and stomatologic internship. Students were asked to let us randomly select 2 paper cones, which were collected after the student would use them to dry their root canal in their endodontic treatment. These cones wer e placed in test tubes containing thioglycollate broth and immediately transferred to the Mult idisciplinary Research Laboratory (LABINM) of the Universidad Privada Antenor Orrego to be incubated at 37 ° C for 16 and 24 hours. An inoculum was then obtained from the medium of each test tube, which was seeded in a petri dish containing blood agar supplemented with 5% percent of human blood and on a MacConkey agar plate respectively. Both plates were then incubated at 37 ° C for 24 hours to check for bacterial growth by observation of bacterial colony forming units. The collected data were expressed in frequencies and percentages using descriptive and inferent ial statist ics, as well as the nonparametric Kruskal Wallis test for the comparison of the groups. Data processing was performed using Excel and IBM SPSS softwares. The results were presented in tables of frequencies and statist ical graphs.Tesi

Rafael Zardoya - One of the best experts on this subject based on the ideXlab platform.

  • beyond Conus phylogenetic relationships of conidae based on complete mitochondrial genomes
    Molecular Phylogenetics and Evolution, 2017
    Co-Authors: Juan E Uribe, Nicolas Puillandre, Rafael Zardoya
    Abstract:

    Understanding how the extraordinary taxonomic and ecological diversity of cone snails (Caenogastropoda: Conidae) evolved requires a statistically robust phylogenetic framework, which thus far is not available. While recent molecular phylogenies have been able to distinguish several deep lineages within the family Conidae, including the genera ProfundiConus, CaliforniConus, Conasprella, and Conus (and within this one, several subgenera), phylogenetic relationships among these genera remain elusive. Moreover, the possibility that additional deep lineages may exist within the family is open. Here, we reconstructed with probabilistic methods a molecular phylogeny of Conidae using the newly sequenced complete or nearly complete mitochondrial (mt) genomes of the following nine species that represent all main Conidae lineages and potentially new ones: ProfundiConus teramachii, CaliforniConus californicus, Conasprella wakayamaensis, LilliConus sagei, PseudolilliConus traillii, Conus (KalloConus) venulatus, Conus (LautoConus) ventricosus, Conus (LautoConus) hybridus, and Conus (EugeniConus) nobilis. To test the monophyly of the family, we also sequenced the nearly complete mt genomes of the following three species representing closely related conoidean families: Benthomangelia sp. (Mangeliidae), Tomopleura sp. (Borsoniidae), and Glyphostoma sp. (Clathurellidae). All newly sequenced conoidean mt genomes shared a relatively constant gene order with rearrangements limited to tRNA genes. The reconstructed phylogeny recovered with high statistical support the monophyly of Conidae and phylogenetic relationships within the family. The genus ProfundiConus was placed as sister to the remaining genera. Within these, a clade including CaliforniConus and LilliConus+PseudolilliConus was the sister group of Conasprella to the exclusion of Conus. The phylogeny included a new lineage whose relative phylogenetic position was unknown (LilliConus) and uncovered thus far hidden diversity within the family (PseudolilliConus). Moreover, reconstructed phylogenetic relationships allowed inferring that the peculiar diet of CaliforniConus based on worms, mollusks, crustaceans and fish is derived, and reinforce the hypothesis that the ancestor of Conidae was a worm hunter. A chronogram was reconstructed under an uncorrelated relaxed molecular clock, which dated the origin of the family shortly after the Cretaceous-Tertiary boundary (about 59million years ago) and the divergence among main lineages during the Paleocene and the Eocene (56-30million years ago).

  • patterns of cladogenesis in the venomous marine gastropod genus Conus from the cape verde islands
    Systematic Biology, 2005
    Co-Authors: Regina L Cunha, Rita Castilho, Lukas Ruber, Rafael Zardoya
    Abstract:

    : Isolated oceanic archipelagos are excellent model systems to study speciation, biogeography, and evolutionary factors underlying the generation of biological diversity. Despite the wealth of studies documenting insular speciation, few of them focused on marine organisms. Here, we reconstruct phylogenetic relationships among species of the marine venomous gastropod genus Conus from the Cape Verde archipelago. This small island chain located in the Central Atlantic hosts 10% of the worldwide species diversity of Conus. Analyses were based on mtDNA sequences, and a novel nuclear marker, a megalin-like protein, member of the low-density lipoprotein receptor gene family. The inferred phylogeny recovered two well-defined clades within Conus. One includes Cape Verde endemic species with larger shells, known as the "venulatus" complex together with C. pulcher from the Canary Islands. The other is composed of Cape Verde endemic and West Africa and Canary Island "small" shelled species. In both clades, nonendemic Conus were resolved as sister groups of the Cape Verde endemics, respectively. Our results indicate that the ancestors of "small" and "large" shelled lineages independently colonized Cape Verde. The resulting biogeographical pattern shows the grouping of most Cape Verde endemics in monophyletic island assemblages. Statistical tests supported a recent radiation event within the "small shell" clade. Using a molecular clock, we estimated that the colonization of the islands by the "small" shelled species occurred relatively close to the origin of the islands whereas the arrival of "large" shelled Conus is more recent. Our results suggest that the main factor responsible for species diversity in the archipelago may be allopatric speciation promoted by the reduced dispersal capacity of nonplanktonic lecithotrophic larvae.

Alan J. Kohn - One of the best experts on this subject based on the ideXlab platform.

  • Conus Envenomation of Humans: In Fact and Fiction.
    Toxins, 2018
    Co-Authors: Alan J. Kohn
    Abstract:

    Prominent hallmarks of the widely distributed, mainly tropical marine snail genus Conus are: (1) its unusually high species diversity; it is the largest genus of animals in the sea, with more than 800 recognized species; and (2) its specialized feeding behavior of overcoming prey by injection with potent neurotoxic, paralytic venoms, and swallowing the victim whole. Including the first report of a human fatality from a Conus sting nearly 350 years ago, at least 141 human envenomations have been recorded, of which 36 were fatal. Most Conus species are quite specialized predators that can be classified in one of three major feeding guilds: they prey exclusively or nearly so on worms, primarily polychaete annelids, other gastropods, sometimes including other Conus species, or fishes. These differences are shown to relate to the severity of human envenomations, with the danger increasing generally in the order listed above and a strong likelihood that all of the known human fatalities may be attributable solely to the single piscivorous species C. geographus.

  • egg size life history and tropical marine gastropod biogeography
    American Malacological Bulletin, 2012
    Co-Authors: Alan J. Kohn
    Abstract:

    Abstract: Comparative studies of egg size and larval morphological characteristics coupled with estimates of dispersal abilities enabled Kohn and Perron (1994) to predict attributes of geographic distribution patterns of Indo-West Pacific Conus species that vary widely in developmental mode. However, because at that time, no species-level phylogenetic hypothesis had ever been proposed for Conus, we were constrained to treat each species as an independent entity. During the past decade, however, molecular phylogenetics of Conus has progressed to the point where character mapping and the method of phylogenetically independent contrasts can evaluate the importance of phylogenetic relatedness to biogeographic patterns. Analyses of species in two well-supported clades with data on ranges of trait variations suggest that significant evolutionary associations remain among developmental traits that affect dispersal ability after accounting for phylogenetic relationships. These are clades of molluscivorous and pis...

  • species level phylogeography and evolutionary history of the hyperdiverse marine gastropod genus Conus
    Molecular Phylogenetics and Evolution, 2005
    Co-Authors: Thomas F Duda, Alan J. Kohn
    Abstract:

    Abstract Phylogenetic and paleontological analyses are combined to reveal patterns of species origination and divergence and to define the significance of potential and actual barriers to dispersal in Conus, a species-rich genus of predatory gastropods distributed throughout the world’s tropical oceans. Species-level phylogenetic hypotheses are based on nucleotide sequences from the nuclear calmodulin and mitochondrial 16S rRNA genes of 138 Conus species from the Indo-Pacific, eastern Pacific, and Atlantic Ocean regions. Results indicate that extant species descend from two major lineages that diverged at least 33 mya. Their geographic distributions suggest that one clade originated in the Indo-Pacific and the other in the eastern Pacific + western Atlantic. Impediments to dispersal between the western Atlantic and Indian Oceans and the central and eastern Pacific Ocean may have promoted this early separation of Indo-Pacific and eastern Pacific + western Atlantic lineages of Conus. However, because both clades contain both Indo-Pacific and eastern Pacific + western Atlantic species, migrations must have occurred between these regions; at least four migration events took place between regions at different times. In at least three cases, incursions between regions appear to have crossed the East Pacific Barrier. The paleontological record illustrates that distinct sets of Conus species inhabited the Indo-Pacific, eastern Pacific + western Atlantic, and eastern Atlantic + former Tethys Realm in the Tertiary, as is the case today. The ranges of

  • origins of diverse feeding ecologies within Conus a genus of venomous marine gastropods
    Biological Journal of The Linnean Society, 2001
    Co-Authors: J Thomas R F Duda, Alan J. Kohn, Stephen R Palumbi
    Abstract:

    Specialized predators on polychaetes, fishes, hemichordates or other molluscs, members of the predominantly tropical gastropod genus Conus diversified rapidly during the Miocene to constitute the most species-rich modern marine genus. We used DNA sequence data from mitochondrial and nuclear loci of 76 Conus species to generate species-level phylogenetic hypotheses for this genus and then mapped known diets onto the phylogenies to elucidate the origins and evolutionary histories of different feeding specializations. The results indicate that dramatically new feeding modes arose only a few times, that the most derived feeding modes likely arose in the Miocene, and that much of the known diversity of Conus that was generated during Miocene radiations has survived to the present.