A putative species complex in the Sea of Japan revealed by DNA sequence data: a study on cf. (Gastropoda: Patellogastropoda).

A putative new limpet species (Patellogastropoda) from the Sea of Japan is revealed by molecular genetic analyses using the mitochondrial markers rRNA and subunit I (), as well as the DNA marker rRNA. Our data indicate that the limpet, collected in the Peter the Great Bay (Russian Federation), is not, as its morphology suggests, the Japanese species Sasaki and Okutani, 1994, and might also hint towards another putative species complex in the Sea of Japan. The different currents between the Far East Asian mainland (cold, subpolar jet running southwards) and the Japanese archipelago (warm, subtropical jet running northwards) are likely to act as a barrier that has a substantial influence on species distribution in these waters.

Neuromuscular development in Patellogastropoda (Mollusca: Gastropoda) and its importance for reconstructing ancestral gastropod bodyplan features.

Within Gastropoda, limpets (Patellogastropoda) are considered the most basal branching taxon and its representatives are thus crucial for research into evolutionary questions. Here, we describe the development of the neuromuscular system in cf. .

Neural architecture of Galathowenia oculata Zach, 1923 (Oweniidae, Annelida).

Background: Oweniids are marine tubeworms burrowing in muddy sediments that in current phylogenies form an early branching lineage within Annelida. Little is known about their general morphology, in particular the nervous system. Here we provide an immunocytochemical investigation of the nervous system of Galathowenia oculata in order to discuss putative ancestral neuronal features in Oweniidae.

Inferring muscular ground patterns in Bivalvia: Myogenesis in the scallop Nodipecten nodosus.

Background: Myogenesis is currently investigated in a number of invertebrate taxa using combined techniques, including fluorescence labeling, confocal microscopy, and 3D imaging, in order to understand anatomical and functional issues and to contribute to evolutionary questions. Although developmental studies on the gross morphology of bivalves have been extensively pursued, organogenesis including muscle development has been scarcely investigated so far.

Results: The present study describes in detail myogenesis in the scallop Nodipecten nodosus (Linnaeus, 1758) during larval and postmetamorphic stages by means of light, electron, and confocal microscopy.

Developmental dynamics of myogenesis in the shipworm Lyrodus pedicellatus (Mollusca: Bivalvia).

Background: The shipworm Lyrodus pedicellatus is a wood-boring bivalve with an unusual vermiform body. Although its larvae are brooded, they retain the general appearance of a typical bivalve veliger-type larva. Here, we describe myogenesis of L.

Posterior regeneration in Isodiametra pulchra (Acoela, Acoelomorpha).

Introduction: Regeneration is a widespread phenomenon in the animal kingdom, but the capacity to restore damaged or missing tissue varies greatly between different phyla and even within the same phylum. However, the distantly related Acoelomorpha and Platyhelminthes share a strikingly similar stem-cell system and regenerative capacity. Therefore, comparing the underlying mechanisms in these two phyla paves the way for an increased understanding of the evolution of this developmental process.

Cellular and muscular growth patterns during sipunculan development.

Sipuncula is a lophotrochozoan taxon with annelid affinities, albeit lacking segmentation of the adult body. Here, we present data on cell proliferation and myogenesis during development of three sipunculan species, Phascolosoma agassizii, Thysanocardia nigra, and Themiste pyroides. The first anlagen of the circular body wall muscles appear simultaneously and not subsequently as in the annelids.

Neuromuscular development of Aeolidiella stephanieae Valdéz, 2005 (Mollusca, Gastropoda, Nudibranchia).

Background: Studies on the development of the nervous system and the musculature of invertebrates have become more sophisticated and numerous within the last decade and have proven to provide new insights into the evolutionary history of organisms. In order to provide new morphogenetic data on opisthobranch gastropods we investigated the neuromuscular development in the nudibranch Aeolidiella stephanieae Valdéz, 2005 using immunocytochemistry as well as F-actin labelling in conjunction with confocal laser scanning microscopy (cLSM).

Results: The ontogenetic development of Aeolidiella stephanieae can be subdivided into 8 stages, each recognisable by characteristic morphological and behavioural features as well as specific characters of the nervous system and the muscular system, respectively.

Sipunculans and segmentation.

Comparative molecular, developmental and morphogenetic analyses show that the three major segmented animal groups-Lophotrochozoa, Ecdysozoa and Vertebrata-use a wide range of ontogenetic pathways to establish metameric body organization. Even in the life history of a single specimen, different mechanisms may act on the level of gene expression, cell proliferation, tissue differentiation and organ system formation in individual segments. Accordingly, in some polychaete annelids the first three pairs of segmental peripheral neurons arise synchronously, while the metameric commissures of the ventral nervous system form in anterior-posterior progression.

Segmental mode of neural patterning in sipuncula.

Recent molecular phylogenetic analyses suggest a close relationship between two worm-shaped phyla, the nonsegmented Sipuncula (peanut worms) and the segmented Annelida (e.g., earthworms and polychaetes) [1-5].