Marine Biology

, Volume 156, Issue 12, pp 2613–2619 | Cite as

High natural fusion rates in a botryllid ascidian

  • Erica L. WestermanEmail author
  • Jennifer A. Dijkstra
  • Larry G. Harris
Original Paper


Many benthic colonial invertebrates have the ability to fuse and form chimeras with compatible colonies. Botryllid ascidians are model organisms for the study of the evolution of and molecular basis for allorecognition, and fusion rates have been determined for different populations and species by random sampling and fusion testing between individuals. However, natural fusion rates over time have not been documented. Nine settlement panels were deployed in Salem Harbor, Massachusetts, USA and Botrylloides violaceus settlement, growth, and fusion monitored from July to mid-August 2007. Seventy-three percent of the recruits observed fused with at least one other colony, while 4% neither fused nor were overgrown. Multifused colonies were not observed to grow faster than single colonies when growth was calculated as increase in size beyond the summation of fused entities; however, they were significantly larger. These results suggest that larvae settle in clumps of compatible individuals, and that large subtidal colonies may be the result of high numbers of fusions between compatible colonies.


Fusion Rate Average Growth Rate Natural Coloni High Fusion Rate Colonial Ascidian 



We would like to thank A. H. Powell and two anonymous reviewers for their comments on this manuscript. E. L. Westerman was funded by a National Estuarine Research Reserve Grant from the National Oceanographic and Atmospheric Administration’s Office of Ocean and Coastal Resource Management.


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Copyright information

© Springer-Verlag 2009

Authors and Affiliations

  • Erica L. Westerman
    • 1
    Email author
  • Jennifer A. Dijkstra
    • 2
  • Larry G. Harris
    • 3
  1. 1.Department of Ecology and Evolutionary BiologyYale UniversityNew HavenUSA
  2. 2.Wells National Estuarine Research ReserveWellsUSA
  3. 3.Department of ZoologyUniversity of New HampshireDurhamUSA

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