Development of the musculature in the limpet Patella (Mollusca, Patellogastropoda) |
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Authors: | A Wanninger Bernhard Ruthensteiner Susanne Lobenwein Willibald Salvenmoser Wim J A G Dictus Gerhard Haszprunar |
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Institution: | Zoologische Staatssammlung, Münchhausenstrasse 21, D-81247 München, Germany. kld1129@mail.lrz-muenchen.de |
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Abstract: | Whole-mount technique using fluorescent-labelled phalloidin for actin staining and confocal laser scanning microscopy as
well as semi-thin serial sectioning, scanning and transmission electron microscopy were applied to investigate the ontogeny
of the various muscular systems during larval development in the limpets Patella vulgata L. and P. caerulea L. In contrast to earlier studies, which described a single or two larval shell muscles, the pretorsional trochophore-like
larva shows no less than four different muscle systems, namely the asymmetrical main head/foot larval retractor muscle, an
accessory larval retractor with distinct insertion area, a circular prototroch/velar system, and a plexus-like pedal muscle
system. In both Patella species only posttorsional larvae are able to retract into the shell and to close the aperture by means of the operculum.
Shortly after torsion the two adult shell muscles originate independently in lateral positions, starting with two fine muscle
fibres which insert at the operculum and laterally at the shell. During late larval development the main larval retractor
and the accessory larval retractor become reduced and the velar muscle system is shed. In contrast, the paired adult shell
muscles and the pedal muscle plexus increase in volume, and a new mantle musculature, the tentacular muscle system, and the
buccal musculature arise. Because the adult shell muscles are entirely independent from the various larval muscular systems,
several current hypotheses on the ontogeny and phylogeny of the early gastropod muscle system have to be reconsidered.
Received: 23 June 1998 / Accepted: 25 November 1998 |
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Keywords: | Gastropoda Patella Ontogeny Larval and adult muscle systems |
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