Topic
Heterodonta
About: Heterodonta is a research topic. Over the lifetime, 76 publications have been published within this topic receiving 2107 citations.
Papers published on a yearly basis
Papers
1 Jan 2001
TL;DR: The key presented in this chapter, as well as many of the major keys to freshwater bivalve molluscs, relies on the integrated use of important anatomical structures and shell characters to identify unionoidean bivalves.
Abstract: North American (NA) freshwater bivalve molluscs (class Bivalvia) fall in the subclasses Paleoheterodonta (Superfamily Unionoidea) and Heterodonta (Superfamilies Corbiculoidea and Dreissenoidea). They have enlarged gills with elongated, ciliated filaments for suspension feeding on plankton, algae, bacteria, and microdetritus. The mantle tissue underlying and secreting the shell forms a pair of lateral, dorsally connected lobes. Mantle and shell are both single entities. During development, the right and left mantle lobes extend ventrally from the dorsal visceral mass to enfold the body. Each lobe secrets a calcareous shell valve which remains connected by a mid-dorsal isthmus. Like all molluscs, the shell valves consist of outer proteinaceous and inner crystalline calcium carbonate elements. The lateral mantle lobes secrete shell material marked by a high proportion of crystalline calcium carbonate making them thick, strong and inflexible, while the mantle isthmus secretes primarily protein, forming a dorsal elastic hinge ligament uniting the calcareous valves. The hinge ligament is external in all freshwater bivalves. Its elasticity opens the valves while the anterior and posterior shell adductor muscles run between the valves and close them in opposition to the hinge ligament which opens them on adductor muscle relaxation. The key presented in this chapter, as well as many of the major keys to freshwater bivalves, relies on the integrated use of important anatomical structures and shell characters to identify unionoidean bivalves. This key is artificial, and it is divided into four sections corresponding to geographical provinces to facilitate identification.
140 citations
TL;DR: Phylogenetic relationships among vesicomyid clams (Bivalvia: Vesicomyidae) and their placement within the order Heterodonta were examined using mitochondrial encoded cytochrome oxidase subunit I (COI) DNA sequences.
Abstract: Phylogenetic relationships among vesicomyid clams (Bivalvia: Vesicomyidae) and their placement within the order Heterodonta were examined using mitochondrial encoded cytochrome oxidase subunit I (COI) DNA sequences. The presently analyzed vesicomyids represent a recent monophyletic radiation that probably occurred within the Cenozoic. Nucleotide phylogenetic analyses resolved discrete clades that were consistent with currently recognized species: Calyptogena magnifica, C. ponderosa, Ectenagena extenta, C. phaseoliformis, Vesicomya cordata, Calyptogena n. sp. (Gulf of Mexico), C. kaikoi, C. nautilei, C. solidissima and C. soyoae (Type-A). However, specimens variously identified as: V. gigas, C. kilmeri, C. pacifica, and V. lepta comprised two “species complexes”, each composed of multiple evolutionary lineages. Most taxa are limited to hydrothermal-vent or cold-seep habitats, but the “vent” versus “seep” clams do not constitute separate monophyletic groups. Current applications of the generic names Calyptogena, Ectenagena, and Vesicomya are not consistent with phylogenetic inferences.
128 citations
TL;DR: These data do not provide support for a close relationship between Platyhelminthes (Turbellaria) and Mollusca, but suggest that the latter group belongs to a clade of eutrochozoan coelomates, and obtain strong preliminary support for phylogenetic inferences at more restricted taxonomic levels.
Abstract: The 18S rRNA sequences of 12 molluscs, representing the extant classes Gastropoda, Bivalvia, Polyplacophora, Scaphopoda, and Caudofoveata, were determined and compared with selected known 18S rRNA sequences of Metazoa, including other Mollusca. These data do not provide support for a close relationship between Platyhelminthes (Turbellaria) and Mollusca, but rather suggest that the latter group belongs to a clade of eutrochozoan coelomates. The 18S rRNA data fail to recover molluscan, bivalve, or gastropod monophyly. However, the branching pattern of the eutrochozoan phyla and classes is unstable, probably due to the explosive Cambrian radiation during which these groups arose. Similarly, the 18S rRNA data do not provide a reliable signal for the molluscan interclass relationships. Nevertheless, we obtained strong preliminary support for phylogenetic inferences at more restricted taxonomic levels, such as the monophyly of Polyplacophora, Caenogastropoda, Euthyneura, Heterodonta, and Arcoida.
119 citations
TL;DR: A phylogenetic reconstruction based on 506 nucleotides near the 5' end of the 18S subunit of ribosomal DNA (rDNA) in 2 gastropod, 3 chiton and 28 bivalve mollusks could not confidently establish either the monophyly or the phylogenetic relationships of the morphologically well defined subclasses Pteriomorphia, Protobranchia, and Anomalodesmata.
Abstract: A phylogenetic reconstruction based on 506 nucleotides near the 5' end of the 18S subunit of ribosomal DNA (rDNA) in 2 gastropod, 3 chiton and 28 bivalve mollusks supported the monophyly and sister group relationship of the subclasses Heterodonta and Palaeoheterodonta but could not confidently establish either the monophyly or the phylogenetic relationships of the morphologically well defined subclasses Pteriomorphia, Protobranchia, and Anomalodesmata. When both gastropods and chitons were included in the analysis, one or the other invariably emerged within Bivalvia. Some evidence indicates that this apparent polyphyly may be the consequence of unequal rates of evolution and of rapid changes in the protobranch and anomalodesmatan lineages. The taxa usually included in Pteriomorpha emerge as a grade rather than a clade, although in a sequence that differs from morphologically based phylogenies.
105 citations
TL;DR: Observations support the theories of acrosome formation by coalescence of numerous proacrosomal vesicles and of reduction in mitochondrial number by mitochondrial fusion.
Abstract: The mature sperm of three species of the subfamily Mytilinae (Choromytilus meridionalis, Mytilus galloprovincialis, Aulacomya ater) are of the primitive type. The sperm are 50–55 μm long, with a distinct head, midpiece of four to six mitochondria, and tail. In all three species the acrosome is in the form of an elongated hollow cone; yet each has its own characteristic morphology, indicating that sperm ultrastructure can be used as an aid to bivalve identification. A reexamination and comparison of the acrosomes from five subclasses of bivalve show that each subclass has an acrosome with a unique form. The process of spermatogenesis is similar in all three species; early spermatogonia are located close to the wall of the germinal follicle, and successive stages are displaced toward the center. Observations support the theories of acrosome formation by coalescence of numerous proacrosomal vesicles and of reduction in mitochondrial number by mitochondrial fusion.
100 citations
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 2021 | 1 |
| 2019 | 2 |
| 2017 | 4 |
| 2016 | 4 |
| 2015 | 2 |
| 2014 | 3 |