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At least 19 recordsLinked to original sources
PubMed2000

Phylogenetic relationships among mytilidae (Bivalvia): 18S rRNA data suggest convergence in mytilid body plans.

Nearly complete sequences were determined for small-subunit (18S) rRNA genes from seven species representative of four subfamilies of Mytilidae: Modiolus modiolus and M. auriculatus (Modiolinae); Lithophaga lithophaga and L. nigra (Lithophaginae); Musculus senhousie and M. discors (Crenellinae); and Hormomya domingensis (Mytilinae). Small-subunit rRNA gene sequences were also determined for Solemya reidi (Subclass Protobranchia), Mya arenaria (Subclass Heterodonta), and Elliptio complanata (Subclass Paleoheterodonta) as outgroup taxa. Phylogenetic analyses including these and other nearly complete bivalve small-subunit rRNA sequences demonstrate support for the monophyly of the family Mytilidae and the subfamilies Crenellinae and Lithophaginae. However, the subfamilies Mytilinae and Modiolinae appear polyphyletic. Likelihood, parsimony, and distance analyses support the placement of H. domingensis (Mytilinae) in a clade with G. demissa (Modiolinae). This clade is distinct from those containing other species traditionally assigned to these two subfamilies. Kishino-Hasegawa tests support these nontraditional relationships, suggesting that the mytiliform and/or modioliform body plans have evolved independently in at least two mytilid lineages.

Animals↗
PubMed2000

[Genetic connections between some species of Mytilidae (Mollusca: Bivalvia) from the northern part of the Pacific Ocean].

In 1978 and 1999, seven and eight species of Mytilidae (Mollusca: Bivalvia) were analyzed using gel electrophoresis. Mean heterozygosity per individual (Hobs and Hexp) and genetic distances (Rogers' DR, Nei's DN, and others) were estimated for 21 and 24 allozyme loci. Mytilus modiolus had the highest variation among the species examined. Genetic distances were lowest for the M. trossulus-M. galloprovincialis species pair: DR = 0.147, DN = 0.078. Overall, five species of the genera Mytilus and Crenomytilus were genetically closer to each other (DR = 0.147, DN = 0.078) than to the remaining three species of this group (DR = 0.807, DN = 2.243). The relationships among the species were examined using cluster analysis and parsimony methods. The densest clusters in the dendrograms consisted of (1) M. trossulus and M. galloprovincialis and (2) M. coruscus, M. californianus, and M. grayanus. These two clusters form a larger cluster (3), which comprises all representatives of the nominal genus Mutilus and C. grayanus. The Mytilus-Crenomytilus cluster is consecutively joined by Adula falcatoides, Mytilus modiolus, and Septifer keenae. According to Nei's genetic distances DN, the time of divergence between M. trossulus and M. galloprovincialis is 0.8-1.6 Myr; between M. californianus and C. grayanus, it is approximately 9 Myr; and between M. coruscus and the latter pair, it is 13 Myr before present. Two representatives of the Mytilus ex gr. edulis complex diverged from the Mytilus-Crenomytilus group of large-size Pacific species about 20 Myr ago. These results are in good agreement with paleontological data and indicate a relatively recent origin of the Mytilus ex gr. edulis complex. The results obtained can be used in systematics and phylogeny of modern Mytilidae.

Animals↗
PubMed2006

Larval development of Brachidontes solisianus (Bivalvia, Mytilidae), with notes on differences between its hinge system and that of the mollusk Perna perna.

This work, which is part of a study program on meroplankton larvae, aims to gain more in-depth knowledge about planktonic larvae. This study began with the mollusk Brachidontes solisianus (Bivalvia-Mytilidae), which is abundant on the rocky shores of the Cabo Frio region (state of Rio de Janeiro, Brazil). Brachidontes solisianus larvae were grown under controlled conditions for a period of 26 days and were fed with Isochrysis galbana and Tetraselmis chui. The temperature was kept at 26 degrees C and the saltiness at 28. Images of the larvae were taken daily with a light camera and measured with a micrometric lens until settlement occurred. The average size of the first D-shaped veliger stage was 90 microm in length and 70 microm in height, while the size in the last stage before settlement (pediveliger) was 273 microm in length and 257 microm in height. The comparative study of the hinge system involved the most abundant intertidal species of the study area: Brachidontes solisianus and Perna perna. The B. solisianus species were found to have more visible denticles at the extremities of the provinculum, whereas the denticles of the P. perna species occur along the entire provinculum.

Animals↗
PubMed2004

Do organisms living around hydrothermal vent sites contain specific metallothioneins? The case of the genus Bathymodiolus (Bivalvia, Mytilidae).

The unusual characteristics of the hydrothermal vent environment (high pressure and metal concentrations, low pH, etc.) leads us to wonder how species living in this particular biotope have adjusted to these severe living conditions. To investigate the consequences of high metal concentrations, filter-feeding organisms are commonly used in ecotoxicological studies. Metallothioneins (MTs) are proteins conserved throughout the animal kingdom and involved in intracellular metal regulation. Therefore, we tried here to find out whether the metallothioneins of hydrothermal bivalves are different from those of coastal bivalves. The characterization of DNA sequences coding MTs from some of the most common hydrothermal bivalves, belonging to the genus Bathymodiolus (Mytilidae) was performed by reverse transcription polymerase chain reactions (RT-PCRs). The complementary DNAs (cDNAs) of MT-10 and MT-20 isoforms were obtained for the Atlantic and Pacific hydrothermal mussels (Bathymodiolus azoricus and Bathymodiolus thermophilus). The MT-10 transcripts were 222 nucleotides long and the MT-20 transcripts, 207 nucleotides. The polymorphism of the MT cDNAs in these two hydrothermal species is discussed. The comparison between metallothionein cDNA sequences of the Mytilus and the Bathymodiolus genera shows strong homologies among metallothioneins of coastal and hydrothermal mussels.

Adaptation, Physiological↗
PubMed2001

A hybrid zone between hydrothermal vent mussels (Bivalvia: Mytilidae) from the Mid-Atlantic Ridge.

This study provides the first example of a hybrid zone between animal taxa distributed along the mid-ocean ridge system. We examined the distribution and genetic structure of deep-sea hydrothermal vent mussels (Bivalvia: Mytilidae) along a 2888-km portion of the Mid-Atlantic Ridge between 37 degrees 50' N and 14 degrees 45' N latitude. Mitochondrial DNA (mtDNA), allozymes and multivariate-morphometric evidence discriminated between individuals of a northern species, Bathymodiolus azoricus, and a southern species, B. puteoserpentis, that were separated by an intermediate ridge segment almost devoid of mussels. A small sample of mussels from Broken Spur, a vent locality along this intermediate zone, revealed a mixed population with gene frequencies and morphology that were broadly intermediate to those of the northern and southern species. Multilocus clines in mtDNA and allozyme frequencies were centred over the intermediate zone. We consider intrinsic and extrinsic processes that might limit genetic exchange across this hybrid zone.

Animals↗
PubMed1997

Phylogenetic evidence for role-reversals of gender-associated mitochondrial DNA in Mytilus (Bivalvia: Mytilidae).

Distinct gender-associated mitochondrial DNA (mtDNA) lineages (i.e., lineages which are transmitted either through males or through females) have been demonstrated in two families of bivalves, the Mytilidae (marine mussels) and the Unionidae (freshwater mussels), which have been separated for more than 400 Myr. The mode of transmission of these M (for male-transmitted) and F (for female-transmitted) molecules has been referred to as doubly uniparental inheritance (DUI), in contrast to standard maternal inheritance (SMI), which is the norm in animals. A previous study suggested that at least three origins of DUI are required to explain the phylogenetic pattern of M and F lineages in freshwater and marine mussels. Here we present phylogenetic evidence based on partial sequences of the cytochrome c oxidase subunit I gene and the 16S RNA gene that indicates the DUI is a dynamic phenomenon. Specifically, we demonstrate that F lineages in three species of Mytilus mussels, M. edulis, M. trossulus, and M. californianus, have spawned separate lineages which are now associated only with males. This process is referred to as "masculinization" of F mtDNA. By extension, we propose that DUI may be a primitive bivalve character and that periodic masculinization events combined with extinction of previously existing M types effectively reset the time of divergence between conspecific gender-associated mtDNA lineages.

Amino Acid Sequence↗
PubMed2000

The exceptional mitochondrial DNA system of the mussel family Mytilidae.

Species of the families Mytilidae (sea mussels) and Unionidae (fresh water mussels) contain two types of mitochondrial DNA (mtDNA), the F that behaves as the standard animal mtDNA and the M that is transmitted through the sperm and establishes itself only in the male gonad. The two molecules have, therefore, separate transmission routes, one through the female and the other through the male lineage. The system has been named doubly uniparental inheritance (DUI). Another important feature of sea mussels is that the sex ratio among offspring of a pair mating is determined by the female parent only. The mechanism of DUI remains unknown. One hypothesis that is consistent with all observations is that the standard maternal inheritance was modified in mussels via the evolution of a suppressor gene that is expressed during oogenesis and has two alleles, the inactive and the active allele. In the presence of the active allele in the mother's genotype the egg is supplied with a substance that interferes and the normal mechanism of elimination of sperm mitochondria. This will explain why half of mussels have the father's mtDNA and half do not, but would not explain why presence/absence of paternal mtDNA is linked with the male and female gender, respectively. To provide an explanation for this linkage, one would have to assume that there is a causal relationship between retention of paternal mtDNA and sex determination.

Animals↗
PubMed2006

Symbioses of methanotrophs and deep-sea mussels (Mytilidae: Bathymodiolinae).

The symbioses between invertebrates and chemosynthetic bacteria allow both host and symbiont to colonize and thrive in otherwise inhospitable deep-sea habitats. Given the global distribution of the bathymodioline symbioses, this association is an excellent model for evaluating co-speciation and evolution of symbioses. Thus far, the methanotroph and chemoautotroph endosymbionts of mussels are tightly clustered within two independent clades of gamma Proteobacteria, respectively. Further physiological and genomic studies will elucidate the ecological and evolutionary roles that these bacterial clades play in the symbiosis and chemosynthetic community. Due to the overall abundance of the methanotrophic symbioses at hydrothermal vents and hydrocarbon seeps, they likely play a significant, but as of yet unquantified, role in the biogeochemical cycling of methane. With this in mind, the search for methanotrophic symbioses should not be restricted to these known deep-sea habitats, but rather should be expanded to include methane-rich coastal marine and freshwater environments inhabited by methanotrophs and bivalves. Our current understanding of the bathymodioline symbioses provides a strong foundation for future explorations into the origin, ecology, and evolution of methanotroph symbioses, which are now becoming possible through a combination of classical and advanced molecular techniques.

Animals↗
PubMed2006

A dual symbiosis shared by two mussel species, Bathymodiolus azoricus and Bathymodiolus puteoserpentis (Bivalvia: Mytilidae), from hydrothermal vents along the northern Mid-Atlantic Ridge.

Bathymodiolus azoricus and Bathymodiolus puteoserpentis are symbiont-bearing mussels that dominate hydrothermal vent sites along the northern Mid-Atlantic Ridge (MAR). Both species live in symbiosis with two physiologically and phylogenetically distinct Gammaproteobacteria: a sulfur-oxidizing chemoautotroph and a methane-oxidizer. A detailed analysis of mussels collected from four MAR vent sites (Menez Gwen, Lucky Strike, Rainbow, and Logatchev) using comparative 16S rRNA sequence analysis and fluorescence in situ hybridization (FISH) showed that the two mussel species share highly similar to identical symbiont phylotypes. FISH observations of symbiont distribution and relative abundances showed no obvious differences between the two host species. In contrast, distinct differences in relative symbiont abundances were observed between mussels from different sites, indicating that vent chemistry may influence the relative abundance of thiotrophs and methanotrophs in these dual symbioses.

Animals↗
PubMed2004

Mitochondrial DNA polymorphisms and sperm motility in Mytilus edulis (Bivalvia: Mytilidae).

The system of mitochondrial DNA (mtDNA) inheritance in Mytilus and other bivalves, termed doubly uniparental inheritance (DUI), is novel among animals. Males pass on their male transmitted (M-type) mtDNA from fathers to their sons whereas females pass on their female transmitted (F-type) mtDNA from mothers to both sons and daughters. Thus, Mytilus males contain two distinct types of mtDNA. Interestingly, sperm contains only the paternal mtDNA. Phylogenetic analysis has shown that some female types have been able to switch their route of inheritance. These "recently masculinized" mitochondrial genomes behave as a typical M-type in that they are transmitted from generation to generation through sperm. Because the "recently masculinized" and "standard" male mitotypes in M. edulis exhibit approximately 8.7% amino acid sequence divergence, we hypothesized that these differences could affect mitochondrial, and hence sperm, functions. Furthermore, since recently masculinized mitotypes have been shown to replace standard male types periodically over evolutionary timescales, we tested the hypothesis that sperm swimming speeds would be greater for males with recently masculinized M-type genomes. Sperm activity was videotaped, digitized and tracked. A linear mixed effects model found no significant difference in linear velocities or curvilinear speeds between the mitotypes suggesting that swimming speeds are similar for both in the period shortly after spawning.

Animals↗
PubMed2005

Pollution monitoring in Southeast Asia using biomarkers in the mytilid mussel Perna viridis (Mytilidae: Bivalvia).

Mytilid mussels have been extensively used in marine pollution monitoring programmes in temperate regions of the world although widespread subtropical representatives such as Perna viridis have only comparatively recently been utilised to monitor the sublethal effects of pollution in Southeast Asia. P. viridis is considered a subtropical equivalent of the temperate Mytilus sp. and has considerable potential for pollution monitoring throughout its geographical range. This paper reviews the current status of biomarkers in P. viridis and provides some recommendations on biological-effects monitoring to facilitate the assessment of coastal pollution in Southeast Asia.

Animals↗
PubMed2001

Feeding rhythms of the green-lipped mussel, Perna viridis (Linnaeus, 1758) (Bivalvia: Mytilidae) during spring and neap tidal cycles.

Food availability and feeding responses of the green mussel Perna viridis were investigated for two complete tidal cycles during both spring and neap tides. Temporal changes in total particulate matter (TPM), particulate inorganic matter (PIM) and particulate organic matter (POM), were smaller during neap than spring tides. Seston characteristics at different times of a tidal cycle were compared for both spring and neap tides. Only during spring tides were TPM and PIM significantly higher at high tides while POM remained relatively constant (P>0.05). The clearance rate of the mussels underwent temporal variations with tides, and was a negative power function of TPM and a positive linear function of f (organic content), during both spring and neap tides. f was the key factor influencing filtration rate, organic ingestion rate, absorption rate and absorption efficiency. All feeding rates increased linearly with increases in organic content. Pseudofaeces were produced only during spring but not neap tides. Feeding rates and absorption efficiency were highest at low and lowest at high tides (P<0.01). There was no significant temporal change in the wet weight and protein content of the crystalline style with the tidal regime. For the digestive gland, alpha-amylase activity was higher at spring than at neap tides, and higher during high tides in a tidal cycle. The digestive gland cellulase activity did not change significantly with the tides. For the crystalline style, both the activity of cellulase and alpha-amylase were not significantly different (P>0.05) between spring and neap tides. Tidal rhythms in feeding and digestion in this species were likely controlled by temporal variations in food availability in the seawater. By adjusting feeding rates and enzymatic activities, absorption in Perna viridis remained constant, irrespective of the changes in food availability.

Journal Article↗
PubMed2001

Ecocytological and toxicological responses to copper in Perna viridis (L.) (Bivalvia: Mytilidae) haemocyte lysosomal membranes.

Bivalve lysosomes are sites of intense intracellular digestion. Lysosomes accumulate many pollutants to high concentrations resulting in membrane destabilisation. Consequently, the elucidation of lysosomal membrane integrity utilising the neutral red assay has been used to good effect in pollution monitoring. Naturally occurring environmental stressors also have the potential to destabilise the membrane. Exposure to elevated copper concentrations and extremes of temperature, salinity, hypoxia, emersion and inadequate ration were investigated in haemocyte lysosomes from the tropical bivalve, Perna viridis. Elevated copper concentrations destabilised the membrane although responses were not entirely related to the exposure-concentration. Environmental stressors induced through higher thermal regimes (29 degrees C and 35 degrees C), hyposalinity (10-25/1000) and prolonged emersion elicited significant lysosomal membrane destabilisation. Hypoxia and inadequate ration did not significantly effect membrane stability. The haemocyte lysosomal membranes were generally resistant to exogenous alterations within normal ranges and only showed significant labilisation at environmental extremes. P. viridis haemocyte lysosomal membrane biomarkers should, therefore, prove robust to natural stressors when deployed in marine monitoring programmes and thus prove a valuable, rapid, cost-effective cytological marker of pollution.

Animals↗