Origin and Diversification of the Mollusca

Wilbur, Karl M.; Runnegar, Bruce; Pojeta, John; Trueman, E. R.; Clarcke, M. R.

doi:10.1016/b978-0-12-751410-9.50009-5

Cited by 56 publications

(58 citation statements)

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“…Learning and memory formation has been localized to a particular central circuit, the procerebral lobe, in which selective gene activation occurs through odor learning. Since the isolated Limax brain can perform odor learning in vitro, the circuits and synapses causally linked to learning and memory formation are assessable for further detailed analysis.Although mollusks and mammals diverged from their common ancestor some 600 million years ago (Runnegar and Pojeta 1985), there is ample evidence for a commonality of solutions used to solve analogous problems between the two taxa. This is evident in several aspects of learning and memory mechanisms, including conserved genes (Nakaya et al…”

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confidence: 99%

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confidence: 99%

“…Although mollusks and mammals diverged from their common ancestor some 600 million years ago (Runnegar and Pojeta 1985), there is ample evidence for a commonality of solutions used to solve analogous problems between the two taxa. This is evident in several aspects of learning and memory mechanisms, including conserved genes (Nakaya et al 2001;Fukunaga et al 2006), cellular signaling processes (Bailey et al 1996;Hatakeyama et al 2000Hatakeyama et al , 2004aBukanova et al 2005;Grinkevich et al 2008), mechanisms of neural integration (Gelperin 1999(Gelperin , 2006Antonov et al 2003;Apfelbach et al 2005), synaptic plasticity (Frank and Greenberg 1994;Kandel 2001;Pittenger and Kandel 2003;Glanzman 2006), and forms of learning (Delaney and Gelperin 1986;McComb et al 2005;Lorenzetti et al 2006).…”

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Neural and molecular mechanisms of microcognition inLimax

2008

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Various non-mammalian model systems are being explored in the search for mechanisms of learning and memory storage of sufficient generality to contribute to the understanding of mammalian learning mechanisms. The terrestrial mollusk Limax maximus is one such model system in which mammalian-quality learning has been documented using odors as conditioned stimuli. The Limax odor information-processing circuits incorporate several system design features also found in mammalian odor-processing circuits, such as the use of cellular and network oscillations for making odor computations and the use of nitric oxide to control network oscillations. Learning and memory formation has been localized to a particular central circuit, the procerebral lobe, in which selective gene activation occurs through odor learning. Since the isolated Limax brain can perform odor learning in vitro, the circuits and synapses causally linked to learning and memory formation are assessable for further detailed analysis.Although mollusks and mammals diverged from their common ancestor some 600 million years ago (Runnegar and Pojeta 1985), there is ample evidence for a commonality of solutions used to solve analogous problems between the two taxa. This is evident in several aspects of learning and memory mechanisms, including conserved genes (Nakaya et al.

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Neural and molecular mechanisms of microcognition inLimax

2008

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“…Distel et al (12) suggested that the symbiosis has evolved separately in many host lineages, because the symbiont trees do not parallel the host classifications which are, unfortunately, not based on explicit phylogenies. The evolutionary separation between the bivalve subclasses Lamellibranchia and Protobranchia, which are considered to be closest to the ancestral bivalve condition, is well characterized morphologically and in the fossil record (2,27). If lamellibranchs truly arose from protobranchs, then the topology of this tree placing the symbionts of a protobranch between two branches of lamellibranchs (Fig.…”

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Phylogenetic relationships of chemoautotrophic bacterial symbionts of Solemya velum say (Mollusca: Bivalvia) determined by 16S rRNA gene sequence analysis

1992

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The protobranch bivalve Solemya velum Say (Mollusca: Bivalvia) houses chemoautotrophic symbionts intracellularly within its gills. These symbionts were characterized through sequencing of polymerase chain reaction-amplified 16S rRNA coding regions and hybridization of an Escherichia coli gene probe to S. velum genomic DNA restriction fragments. The symbionts appeared to have only one copy of the 16S rRNA gene. The lack of variability in the 16S sequence and hybridization patterns within and between individual S. velum organisms suggested that one species of symbiont is dominant within and specific for this host species. Phylogenetic analysis of the 16S sequences of the symbionts indicates that they lie within the chemoautotrophic cluster of the gamma subdivision of the eubacterial group Proteobacteria.Procaryote-eucaryote associations in which marine invertebrates harbor chemoautotrophic bacteria as endosymbionts appear to be widespread in marine habitats such as deep-sea hydrothermal vents and coastal sediments (8,15). In such symbioses, the procaryotes utilize the energy released by the oxidation of reduced inorganic substrates, such as hydrogen sulfide, to fix carbon dioxide via the CalvinBenson cycle (7, 13). The hosts appear to derive nutrition from their endosymbionts and in turn provide the symbionts simultaneous access to the substrates from anoxic and oxic environments which are necessary for energy generation. Maintenance of such intracellular symbionts presents a novel metazoan acquisition of procaryotic energy generation and autotrophic carbon fixation.While the existence of chemoautotroph-invertebrate symbioses is now generally accepted, little is actually known about the symbionts observed in the tissues of any of the hosts because none have been cultured. Comparison of rRNA sequences has greatly facilitated the identification of bacteria, including unculturable microorganisms, and the elucidation of their natural relationships (38). Phylogenetic analysis of 16S rRNA sequences enabled Distel et al. (12) to establish that the chemoautotrophic symbionts of the hydrothermal vent tubeworm and five species of bivalves of the subclass Lamellibranchia are related and cluster in the gamma subdivision of the Proteobacteria (formerly purple photosynthetic bacteria), one of the 11 major groups of eubacteria (30).In this investigation we sought to establish the phylogenetic relationships and the species specificities of the symbionts of the protobranch bivalve Solemya velum Say, an Atlantic coast clam which has been studied as a shallowwater model of invertebrate-chemoautotroph associations (7, 9, 10). The phylogenetic placement of the S. velum symbionts, to date limited to sequence analysis of the 5S rRNA, indicates that these symbionts also fall in the Proteobacteria gamma subdivision (31). However, the small size of * Corresponding author. t Present address:

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“…The very small size (about 1-2 mm) of the Early Cambrian molluscs has been discussed in detail by many scholars (Runnegar and Jell, 1976;Runnegar and Pojeta, 1985;Chaffee and Lindberg 1986;Salvini-Plawen, 1990;Dzik, 1991;Peel, 1991;Haszprunar, 1992). The holotype of A. polytremata is 1.500 mm in length, with seven tremata on the dorsal ridge.…”

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Very old patelliform gastropods from the Early Cambrian of China: Reconsideration of the systematic position of Archaeotremaria

Wen¹

2002

Rec West Aust Mus

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-Archaeotremaria polytremata Yu from the Lower Cambrian Maidiping Member of the Hongchunping Formation of Sichuan, China, was originally described as a primitive monoplacophoran. A restudy of the holotype and paratype has led to a reconsideration of its systematic position. A. polytremata has a patelliform shell with a series of median-dorsal tremata extending from the apex to the anterior margin and periodic rugae. The species is now reassigned to the Gastropoda, rather than Monoplacophora.

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Origin and Diversification of the Mollusca

Cited by 56 publications

References 58 publications

Neural and molecular mechanisms of microcognition inLimax

Neural and molecular mechanisms of microcognition inLimax

Phylogenetic relationships of chemoautotrophic bacterial symbionts of Solemya velum say (Mollusca: Bivalvia) determined by 16S rRNA gene sequence analysis

Very old patelliform gastropods from the Early Cambrian of China: Reconsideration of the systematic position of Archaeotremaria

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