Search results for "Sipunculus nudus"
showing 3 items of 3 documents
Respiratory proteins in Sipunculus nudus--implications for phylogeny and evolution of the hemerythrin family.
2009
Three major classes of respiratory proteins are known, hemoglobin, molluscan and arthropod hemocyanin, and hemerythrin (Hr). Similar to hemoglobin, respiratory Hr is packed into erythrocytes floating in the coelomic fluid and is only known from sipunculids, brachiopods, and priapulids. Owing to this scattered distribution, the presence of Hr is generally assumed to be the plesiomorphic condition without phylogenetic importance. By sequencing 2000 Expressed Sequence Tags (ESTs) from Sipunculus nudus, we found 75 Hr-coding ESTs assembled to 20 cDNA contigs classified as four distinct Hr isoforms: three polymeric Hrs (subunit A, A', and B) and the monomeric myo-hemerythrin (myoHr). Phylogeneti…
Defence Mechanisms and Stem Cells in Holothuria polii and Sipunculus nudus
2009
Holothuria polii (Phylum Echinodermata) and Sipunculus nudus (Phylum Sipuncula) have been used as model systems for studying invertebrate immunity. In the coelomic fluid of Holothuria polii, coelomocytes (i.e. amoebocytes, Type I, Type II, Type III spherule cells) and stem cells are present. After an injection of formalin-fixed sheep erythrocytes into the coelomic cavity, structural modifications in the animal’s, such as the coelomic cavity, stone canal and periesophageal ring were observed. Cellular events observed within the coelomic cavity include the recruitment of a large number of coelomocytes from the haemopoietic areas, phagocytosis carried out by amoebocytes and the formation of br…
Mitochondrial genome sequence and gene order of Sipunculus nudus give additional support for an inclusion of Sipuncula into Annelida.
2010
Abstract Background Mitochondrial genomes are a valuable source of data for analysing phylogenetic relationships. Besides sequence information, mitochondrial gene order may add phylogenetically useful information, too. Sipuncula are unsegmented marine worms, traditionally placed in their own phylum. Recent molecular and morphological findings suggest a close affinity to the segmented Annelida. Results The first complete mitochondrial genome of a member of Sipuncula, Sipunculus nudus, is presented. All 37 genes characteristic for metazoan mtDNA were detected and are encoded on the same strand. The mitochondrial gene order (protein-coding and ribosomal RNA genes) resembles that of annelids, b…