Urnatella gracilis
Leidy, 1851
Common Name:
Freshwater goblet worm
Synonyms and Other Names:
Identification:
Urnatella gracilis is a freshwater colonial Entoproct (small sessile aquatic animal) that grows in a single stalk or in groups of up to six stalks (zooids) connected at the base by a stolon (basal plate) (Davenport 1893, Dana et al. 1854). The stalks are segmented with upwards of 16-18 segments, and can have curved, semi-erect branches that attach at the base by the lowest segment (Dana et al. 1854). The top segment, or active polyp (calyx) is bell-shaped, and the rim is lined with 12-14 cylindrical, ciliated tentacles that encircle the upward-facing mouth (Dana 1854, Davenport 1893). Segments are translucent and white to yellow in color and segments narrow in size as they approach the calyx (Dana et al. 1854, Davenport 1893). Urnatella gracilis is the only freshwater kamptozon in North America. There is only one other known species of freshwater Entoproct, Loxosomatoides sirindhornae, which is native to Thailand (Wood et al. 2006).
Size:
From 500 µm up to 3 mm in height (McCullough and Smith 1975).
Native Range:
Native to freshwaters of the northeastern United States in Pennsylvania, Illinois, Michigan, Indiana, Virginia, Tennessee, Kentucky, Ohio and in Lake Erie (Edmondson 1959, McCullough and Smith 1975), the Trinity River basin in Lake Dallas, Texas and in Oklahoma (Weise 1961).
Great Lakes Nonindigenous Occurrences:
The first non-native record of Urnatella gracilis for the Great-Lakes St. Lawrence system was on shells of Corbicula fluminea in 2011 near a nuclear power plant near Becancour, Quebec. This is the northernmost record for this species (Hamelin et al. 2016), but is suspected would not persist outside the thermal plume. In 2023, U. gracilis was found in ponds behind Erie Pier, Duluth, MN. This pier serves direct shipping traffic to Lake Erie (where the species is native).
Table 1. Great Lakes region nonindigenous occurrences, the earliest and latest observations in each state/province, and the tally and names of HUCs with observations†. Names and dates are hyperlinked to their relevant specimen records. The list of references for all nonindigenous occurrences of Urnatella gracilis are found here.
Full list of USGS occurrences
Table last updated 5/1/2024
† Populations may not be currently present.
Ecology:
Urnatella gracilis is the only species of freshwater Entoproct native to North America and can be found in lakes and rivers growing as a single stock or in colonies on twigs, bark, stones, and mussel shells (McCullough and Smith 1975, Pennak 1953, Weise 1961). This species is somewhat salt tolerant and can withstand brackish water and moderate pollution, sometimes being found in waters with high nitrogen, phosphate, chloride, and ammonia levels (McCullough and Smith 1975, Weise 1961). It is a suspension feeder and passively feeds on phytoplankton and algae, using ciliated tentacles to capture food and move it toward the mouth (McCullough and Smith 1975, Weise 1961). Urnatella gracilis reproduces both sexually and asexually. During asexual reproduction, new stocks are formed via budding, which occur either as a linear series of segments (or a “branch”) off the main stock, or where a calyx arises from a single-segmented stock at the stolen (basal plate) (Dana et al. 1854). It is thought that U. gracilis is a protandrous hermaphrodite (meaning it changes sex from male to female during growth but does not have male and female gonads simultaneously) (Nielsen 1983). During sexual reproduction, spermatozoa are expelled into the water column and fertilize eggs in the ovary of the adult, eventually developing into planktonic larvae that are then capable of producing new colonies (Nielsen 1983).
Means of Introduction:
Most nonindigenous occurrences of Urnatella gracilis are likely attributed to ballast water discharge from ships (Hamelin et al. 2016). The occurrence in the lower Snake River, WA was likely due to hitch-hiking on fishing or boating equipment.
Great Lakes Status:
Range expansion. Native in Lake Erie with reports in Duluth Superior Harbor and Quebec.
Great Lakes Impacts:
References
(click for full reference list)
Author:
Reaver, K.M.
Contributing Agencies:
Revision Date:
4/15/2024
Citation for this information:
Reaver, K.M., 2024, Urnatella gracilis Leidy, 1851: U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL, and NOAA Great Lakes Aquatic Nonindigenous Species Information System, Ann Arbor, MI, https://nas.er.usgs.gov/queries/greatLakes/FactSheet.aspx?Species_ID=285&Potential=N&Type=0&HUCNumber=DGreatLakes, Revision Date: 4/15/2024, Access Date: 5/1/2024
This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.