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8 recordsLinked to original sources
PubMed1991

Phylogenetic characterization and in situ localization of the bacterial symbiont of shipworms (Teredinidae: Bivalvia) by using 16S rRNA sequence analysis and oligodeoxynucleotide probe hybridization.

It has been proposed that a bacterium isolated from the gills of shipworms (teredinid mollusks) is, by virtue of its ability both to degrade cellulose and to fix dinitrogen, the symbiont that enables these mollusks to utilize wood as their principal food source. The phylogenetic affiliation of four of these bacteria isolated from wood-boring bivalve mollusks was determined by 16S rRNA sequence analysis by using the reverse transcriptase method with six oligodeoxynucleotide primers. The four bacterial strains tested had indistinguishable 16S rRNA sequences, supporting the previous conclusion, based on phenotypic characterization, that these isolates represent a single species. Evolutionary distance matrix analysis of the RNA sequence indicated that the bacterial symbiont falls within the gamma-3 subdivision of the Proteobacteria and is distinct from other known bacterial genera. In situ localization of the bacterial symbiont in tissue sections of the shipworm Lyrodus pedicellatus was determined by using a 16S rRNA-directed oligodeoxynucleotide hybridization probe specific for the bacterium isolated from shipworm gill tissue. Fluorescence microscopy showed that the specific probe bound to L. pedicellatus tissue at sites coincident with the location of symbiont cells and that it did not bind to other host tissues. This technique provided direct visual evidence that the cellulolytic, nitrogen-fixing bacterial isolates were the symbionts observed within the gill of L. pedicellatus.

Animals↗
PubMed1988

Purification and characterization of an extracellular endoglucanase from the marine shipworm bacterium.

Bacterial cultures isolated from the gland of Deshayes of marine shipworm (Psiloteredo healdi) produced extracellular endoglucanase activity when cultured with 1% cellulose. An endoglucanase of subunit relative molecular mass 58,000, as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, was purified to homogeneity from cell-free culture medium. Similarly, the relative molecular mass of the native enzyme was 60,100 as determined by gel permeation chromatography. No carbohydrate appeared to be associated with the purified protein. The action of the purified enzyme on various cellodextrins was also studied. Only interior glucosyl linkages of cellodextrin chains larger than cellotriose were cleaved by the enzyme and the centermost bond of cellohexaose was preferentially cleaved. The Km values of the purified endoglucanase were 0.12 mM for cellotetraose, 0.05 mM for cellopentaose, and 0.11 mM for cellohexaose. Glucose, cellobiose, and cellotriose did not inhibit enzymatic activity.

Animals↗
PubMed1987

Extracellular endoglucanase activity by a novel bacterium isolated from marine shipworm.

An extracellular enzyme preparation from shipworm bacterium cultures dramatically increased reducing sugar content of carboxymethylcellulose (CMC3), but did not solubilize sugar from particulate cellulose. The preparation degraded cellodextrins larger than cellotriose (G3). Only interior cellodextrin chain linkages were cleaved and the center-most bond of cellohexaose (G6) was preferentially cleaved. Activity maxima were observed at 60 degrees C and between pH 5.0 and 7.0. The activity was resistant to protease treatment and little loss of activity was observed after 14 d at 25 degrees C.

Animals↗
PubMed1975

Location of glycogen in spermatids and spermatozoa of the shipworm, Bankia australis (Teredinidae, Bivalvia, Mollusca).

The periodic acid-thiocarbohydrazide-silver proteinate technique and alpha-amylase digestion were used to locate glycogen in the spermatids and sperms of the bivalve Bankia australis. Glycogen was found in the middle piece and around the acrosome in spermatozoa, apparently randomly scattered throughout the cytoplasm of young spermatids, and in a cytoplasmic bead in old spermatids.

Acrosome↗
PubMed2026

Reproduction on the Rocks: Life History of a Freshwater Macrobioeroding Bivalve.

Macrobioerosion, the excavation and removal of consolidated mineral substrates by macrofauna, is well established in marine systems, where macrobioeroders drive carbonate cycling, sediment production and habitat formation. In freshwater ecosystems, however, it has been documented in only a small number of invertebrate taxa and remains a poorly resolved ecological process. Among these, the teredinid shipworm Lithoredo abatanica represents a remarkable departure from the wood-boring ecology of its family, having evolved to excavate and ingest limestone in fresh water. Despite this remarkable ecological transition, its reproductive biology and life history remain unknown. Here, we investigate the reproductive mode and life history strategy of this species using population size structure, in&#xa0;situ observations of siphonal morphology, and sperm morphometrics. We show that L.&#x2009;abatanica reaches exceptional dimensions, with measured body lengths exceeding 100&#x2009;mm, one intact empty burrow exceeding 200&#x2009;mm and in-water observations indicating burrows possibly exceeding 500&#x2009;mm, establishing it as the largest known freshwater macrobioeroder. Its large size and dense aggregations indicate considerable capacity for local rock breakdown and habitat modification within the Abatan River system (Bohol, Philippines). Recently settled juveniles (<&#x2009;10&#x2009;mm) alongside reproductively mature individuals indicate ongoing recruitment. The morphology of the siphons and calcareous tube appears to preclude direct sperm transfer via pseudocopulation, while sperm morphometrics are consistent with external fertilisation. Together, these findings indicate that L.&#x2009;abatanica reproduces via broadcast spawning with external fertilisation and likely possesses a planktotrophic larval phase. This raises a fundamental question: how does a broadcast-spawning species with planktotrophic larvae maintain populations up to 15&#x2009;km upstream in a flowing freshwater river subject to persistent downstream advection? By resolving the life history of the largest known freshwater macrobioeroder, this study provides critical insight into the persistence, dispersal and ecological role of a globally unique riverine ecosystem engineer.

broadcast spawning↗