Marine Biology

, Volume 148, Issue 2, pp 307–317 | Cite as

Movements of Ilyanassa obsoleta (Gastropoda) on an intertidal sandflat

  • Lawrence A. CurtisEmail author
Research Article


The gastropod Ilyanassa obsoleta (Say) is native to the east coast of North America where it is locally abundant on sandflats, mudflats, and in saltmarsh creeks. The local disturbances created by snails and their movements affect soft-sediment community composition. Movements of individually marked snails were followed on an intertidal sandflat on Cape Henlopen, Delaware, U.S.A. In June 1991, 1,200 snails that had tested as trematode-uninfected were released and over 5 months 554 were sighted 971 times. Mean daily net distance moved was 1.7 m, but snails often moved 10–20 m day−1 and one snail was 180 m distant after 130 days. Net dispersal of the released population was attained in ≈10 days, by which time, a typical distance from release was 15–20 m. Snails were not found crossing sandbars and most moved away from shore into a tidal gully. In June 1993, 500 snails, both uninfected and trematode-infected, were released at the same position and over 6 months, 350 snails were sighted 949 times. Sandbars were again barriers to movement, but their changed positions allowed wider dispersal. Net dispersal was complete in ≈20 days by which time a typical distance from release was 30–40 m. Mean daily net distance moved was 2.2 m, but within 10 days snails had moved 50–100 m. In both years, following initial dispersal, snails (infected or not) took up random directions from move to move. Infected and uninfected snails dispersed equal distances, but had different mean final dispersal directions. Dispersal of I. obsoleta individuals was extensive and affected by shifting sandbar positions and parasitism. Recognizing this will be important in appreciating the ecological dynamics of this gastropod and in determining its effects on soft-bottom communities.


Shell Height Infected Snail Initial Dispersal Trematode Infection Dispersal Index 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.



It was difficult, particularly long after release, to find marked snails. I wish to thank especially K. Hubbard (and the Undergraduate Research Peter White Fellowships supporting her), and also C. Morrisey, for many hours spent searching and doing the other tasks involved. I am indebted to two anonymous referees for their insights.

Supplementary material

227_2005_42_MOESM1_ESM.pdf (58 kb)
Supplementary material


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Copyright information

© Springer-Verlag 2005

Authors and Affiliations

  1. 1.Department of Biological Sciences and Graduate College of Marine StudiesUniversity of DelawareNewarkUSA
  2. 2.Cape Henlopen Laboratory, College of Marine StudiesUniversity of DelawareLewesUSA

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