Comparative myoanatomy of cycliophoran life cycle stages

Authors

  • Ricardo C. Neves,

    1. Centro de Estudos do Ambiente e do Mar, Departamento de Biologia, Universidade de Aveiro, Campus Universitário de Santiago, 3810 – 193 Aveiro, Portugal
    2. Zoological Museum, Natural History Museum of Denmark, University of Copenhagen, Universitetsparken 15, DK-2100 Copenhagen Ø, Denmark
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  • Marina R. Cunha,

    1. Centro de Estudos do Ambiente e do Mar, Departamento de Biologia, Universidade de Aveiro, Campus Universitário de Santiago, 3810 – 193 Aveiro, Portugal
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  • Peter Funch,

    1. Ecology and Genetics, Department of Biological Sciences, Aarhus University, Aarhus, Ny Munkegade B1540, DK-8000 Århus C, Denmark
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  • Reinhardt M. Kristensen,

    1. Zoological Museum, Natural History Museum of Denmark, University of Copenhagen, Universitetsparken 15, DK-2100 Copenhagen Ø, Denmark
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  • Andreas Wanninger

    Corresponding author
    1. Research Group for Comparative Zoology, Department of Biology, University of Copenhagen, Universitetsparken 15, DK-2100 Copenhagen Ø, Denmark
    • Research Group for Comparative Zoology, Department of Biology, University of Copenhagen, Universitetsparken 15, DK-2100 Copenhagen Ø, Denmark
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  • This article was published online on 18 December 2009. An error was subsequently identified and the article was corrected on 22 December 2009. At the time of publication an amendment to the article title was not properly incorporated by the publisher. The publisher regrets the error.

Abstract

The metazoan phylum Cycliophora includes small cryptic epibionts that live attached to the mouthparts of clawed lobsters. The life cycle is complex, with alternating sexual and asexual generations, and involves several sessile and free-living stages. So far, the morphological and genetic characterization of cycliophorans has been unable to clarify the phylogenetic position of the phylum. In this study, we add new details on the muscular anatomy of the feeding stage, the attached Prometheus larva, the dwarf male, and the female of one of the two hitherto described species, Symbion pandora. The musculature of the feeding stage is composed of myofibers that run longitudinally in the buccal funnel (two fibers) and in the trunk (variable number of fibers). The mouth opening is lined by a myoepithelial ring musculature. A complex myoepithelial sphincter is situated proximal to the anus. In the attached Prometheus larva, three longitudinal sets of myofilaments run dorsally, laterally, and ventrally along the entire anterior-posterior body axis. The muscular architecture of the dwarf male is complex, especially close to the penis, in the posterior part of the body. An X-shaped muscle structure is found on the dorsal side, whereas on the ventral side, longitudinal muscles and a V-shaped muscle structure are present. These muscles are complemented by additional dorsoventral muscles. The mesodermal muscle fibers attach to the cuticle via the epidermis in all life cycle stages studied herein. The musculature of the female is similar to that of the Pandora larva of Symbion americanus and includes dorsoventral muscles and longitudinal muscles that run in the dorsal and ventral body region. Overall, our results reveal striking similarities in the muscular arrangement of the life cycle stages of both Symbion species. J. Morphol., 2010. © 2009 Wiley-Liss, Inc.

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