Chesapeake Bay Introduced Species Database

Myosotella myosotis

Common name(s):
salt marsh snail
Myosotella myosotis is a small brown salt marsh snail, native to Europe (British Isles, Mediterranean, etc.), that is sometimes called the mouse-ear marsh snail. It has been introduced into several locations including the East Coast of North America from Nova Scotia to the West Indies, the US west coast from Washington to California, South Africa, Australia, and New Zealand. Introduction of this snail could have occurred by several means including, dry ballast (rocks and dirt used for weight on old sailing vessels), the oyster trade, and discarded packing material. Once these snails have been introduced to a new location their local range expansion is limited, thus their distribution remains spotty for years after introduction. These snails were first reported in Chesapeake Bay in 1900 in St. Leonard?s Creek, a Patuxent River tributary. But over the years they have shown up in several other locations including Fisherman's Island (Northampton Co), VA, at the mouth of the Bay, Norfolk, VA marshes, Crisfield, MD, and the Little Annemessex River in Maryland. Along the Atlantic Coast they have been reported in Chincoteague, Watt's Bay, Willis Wharf, and Hog Island Bay, VA. No negative impacts have been reported.
Image courtesy of Auguste Le Roux.

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Environmental Tolerances

For Survival
For Reproduction
Temperature (ºC)
null null null null
Salinity (‰)
0 55 5 50
null null    
Salinity Range

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Age and Growth

Minimum Adult Size (mm)
4 4
Typical Adult Size (mm)
null null
Maximum Adult Size (mm)
7 7
Typical Longevity (yrs)
null null
Maximum Longevity (yrs)
null null

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Reproductive Season
April --- September
Typical Number of Young
per Reproductive Event
Sexuality Mode(s)
Mode(s) of Asexual Reproduction
Fertilization Type(s)
More than One Reproductive
Event per Year
Reproductive Strategy
Egg/Seed Form

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Minimum Typical Maximum
Egg/Seed Development Time (days)
null 22 null
Larval/Seed Development Period (days)
null null null
Male Maturation Age (yrs)
null null  
Female Maturation Age (yrs)
null null  
Larval/Seed Form  
direct develop

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Locomotion and Abundance in Chesapeake

mobile common
mobile common

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Habitat Preferences

Primary Horizontal Habitats
salt/brackish marsh; coarse woody debris; unstructured; marinas and docks; rocky salt/brackish marsh; coarse woody debris; unstructured; marinas and docks; rocky
Secondary Horizontal Habitats
Reproductive Horizontal Habitats
n/a n/a salt/brackish marsh; coarse woody debris; unstructured; marinas and docks; rocky
Vertical Habitats
epibenthic epibenthic
Substrate Type
mud; sand; silt; wood; vegetation; piers; rock mud; sand; silt; wood; vegetation; piers; rock
Tidal Height Location
high intertidal; supratidal high intertidal; supratidal
Wave Exposure
low; protected
Water Flow

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Trophic Interactions

Trophic Status
non-feeding herbivore herbivore
Common Food/Prey Items
non-feeding bacteria; blue-green algae; diatoms; macroalgae; vascular plants (epithelial cells) bacteria; blue-green algae; diatoms; macroalgae; vascular plants (epithelial cells)
Common Competitors
Common Consumers
birds [Catotrophorus semipalmatus (Willets)] birds [Catotrophorus semipalmatus (Willets)]

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Life History: Environmental Tolerances: Salinity- These experiments were run on water-saturated substrate with Baltic specimens; there was no mortality over this range. Mediteranean M. myosotis tolerate substrate salinities up to 90 ppt. Tolerances are reduced during prolonged submergence. Baltic snails (20 ppt acclimated) had ~50% survival in ~4 days at 0 ppt and ~60% survival over 25 days at 35 ppt (Seelemann 1968).

Reproduction: Reproductive Season- These dates come from Germany (Meyer 1955). Typical Number of Young per Reproductive Event- The range is 15-80, and the average is 25-30, for German specimens (Meyer 1955).

Development Maturation Size- Maturation was inferred from shell characters (Phorson 1991).
Community Ecology: Habitat Preferences: Primary Horizontal Habitats- Myosotella myosotis was found: 'under boards, drift material, and debris at the high-tide line of Salicornia (Glasswort, Pickleweed) salt marshes, and along protected beaches of lagoons and bays' (Carlton 1979); 'from a boat slip where they were embedded in the wooden bulwark, and on an algae covered area immediately above the high tide line. In an area bounded by Jenkin's Creek, they were present in large numbers on the ground under wood and debris and inside decomposed driftwood well above the normal high-tide level' (Allen 1954); 'on stones above the high-water mark' (Balch 1899); 'on stone foundations of the bridge' (Perkins 1869).

This data was last modified on Wednesday, September 21st, 2005.
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