Abstract
Gastrotrichs are acoelomate micrometazoans common to marine interstitial environments of sublittoral sediments and exposed sandy beaches. The genus Neodasys (Chaetonotida) contains three marine species known from oceans and seas worldwide, and figures prominently in discussions of gastrotrich origins. To gain insight into the phylogenetic position of Neodasys and to understand the adaptive significance of muscle anatomy in marine interstitial gastrotrichs, a fluorescent phalloidin-linked marker was used to view the organization of muscles in two species from North America and Australia. Muscular topography of Neodasys cirritus from Florida, USA, and Neodasys cf. uchidai from Queensland, Australia, was found to be similar between species and to basal species of Macrodasyida; muscles were present in circular, longitudinal and helicoidal patterns. Musculature of the midgut region was partially reduced relative to basal macrodasyidan gastrotrichs, but well developed relative to most other chaetonotidan gastrotrichs. In general, muscle patterns in species of Neodasys closely correspond with those of other gastrotrichs of similar size and body type, and may therefore reflect a common adaptive solution to the physical demands of the interstitial environment. Results also suggest that reductions in midgut musculature may be functionally related to oviposition and, as such, are probably not homologous with similar reductions of circular muscles in other species of Chaetonotida.
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Acknowledgements
This manuscript benefited from the constructive comments of several anonymous reviewers. I thank Mr. R. Webb at the Centre for Microscopy and Microanalysis, University of Queensland, for help with the fluorescence microscope, and J. Piraino of the Smithsonian Marine Station for her gracious assistance with the SEM. Funding for this research was provided by the Sumner Gerard Foundation through a postdoctoral fellowship to the Smithsonian Marine Station at Fort Pierce, Florida. Additional funding was provided by the Australian Biological Resource Study and a NSF Doctoral Dissertation Improvement Grant (DEB 0206495). This is Smithsonian Marine Station at Fort Pierce contribution no. 594.
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Communicated by O. Kinne, Oldendorf/Luhe
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Hochberg, R. Musculature of the primitive gastrotrich Neodasys (Chaetonotida): functional adaptations to the interstitial environment and phylogenetic significance. Marine Biology 146, 315–323 (2005). https://doi.org/10.1007/s00227-004-1437-0
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DOI: https://doi.org/10.1007/s00227-004-1437-0