Practical information to identify and manage non-native, invasive plants and animals
The Quiet Invasion:A Guide to Invasive Species of the Galveston Bay Area
Didemnum perlucidum
| ITIS TSN: | 159048 |
| Presence: | Current Invaders |
| Habitat: | Aquatic |
| Native Range: | Wide tropical and subtropical distribution in the Atlantic and Pacific |
Human Health
This species poses no known human health impacts.Prohibited Lists
As of 2010, this species is not prohibited by the TPWD.Introduction Pathways
Introduction of the white crust tunicate was most likely through ship hull fouling or transportation of larvae in ballast water. This species is dispersed locally and regionally through transportation of larvae via currents (Perry 2006a).Geographic Distribution
This species has been documented in the northern Gulf of Mexico and off the coasts of Florida, Texas and Hawaii (Perry 2006a).Specific Primary Habitats
The white crust tunicate attaches to artificial structures in shallower waters such as oil rigs and sunken vessels, and can colonize them quite heavily. This species typically does not reach such densities on natural reef habitats (Kremer et al. 2010). However, degraded coral reefs may be susceptible to invasion (ISSG 2007a). Didemnum spp. are strong spatial competitors and rapid colonizers. Many Didemnum species deter predators via chemical defenses that cause toxicity or reduced palatability.Ecological, Economic, or Social Impact
Dense populations reduce the abundance of previously established benthic species. The species is also known to foul ship hulls, and infrastructure in marinas, ports, and shellfish farms (Perry 2006a). White crust tunicate exhibits high recruitment rates on bare substrates (Kremer et al. 2010).Physical Description
This species is part of a group of organisms known as ascidians, or sea squirts. These filter feeding animals have a simple sac-like body form. The white crust tunicate is a colonial tunicate and is most often white, but sometimes yellow or reddish. It forms a thin sheet-like crust usually about 8 cm long and 5 mm thick. This species occasionally appears bushy (Kott 2004; Perry 2006a).Reproduction Characteristics
The white crust tunicate is sexually mature within a few weeks, is highly fecund, and capable of breeding year round. The species can produce up to 300 larvae per square centimeter of colony. Each zooid (reproductive individual) in the colony is hermaphroditic, reproducing sexually via external fertilization or asexually via budding; new colonies form when planktonic larvae eventually settles onto a substrate as a sessile filter feeder (Kremer et al. 2010).Feeding
The white crust tunicate is a suspension filter feeder. It feeds on suspended particulate matter by pumping large amounts of water through its siphon and trapping fine particles in a mucous membrane.Control
Early detection is key to preventing the spread and establishment of this species and regional/local monitoring or surveillance is essential. If found in local waters, note the location and notify the TPWD.Lists
This species belongs to the following lists:
Images
To view a larger version of an image, click on the thumbnail. White crust tunicate (Didemnum perlucidum). Photo courtesy of Gustav Paulay, The Marine Biodiversity of Guam and the Mariana Islands Image Collection, Florida Museum of Natural History. |