INVERTEBRATEINVADERS

Established and Potential ExoticsGulf of Mexico Region

Funded by the Coastal Impact Assistance Program through the Mississippi Department of Environmental Quality

For additional copies: marine.education@usm.edu or 228.818.8890

Writers: Harriet Perry and David Yeager Editors: Tom Van Devender, Lisa Hendon

and Linda Skupien

INVERTEBRATEINVADERS

Established and Potential ExoticsGulf of Mexico Region

AA/EOE/ADAI 12/06

703 East Beach Drive • Ocean Springs, MS 39564228.872.4200 • www.usm.edu/gcrl

PARTNER INSTITUTIONS AND AGENCIESThe University of Southern Mississippi

Center for Fisheries Research and Development

Mobile Bay National Estuary Program

NOAA National Marine Fisheries Service

Mississippi Department of Environmental Quality

Coastal Impact Assistance Program

Mississippi Department of Marine Resources

Mississippi-Alabama Sea Grant Consortium

Cover photo: David Knott, Southeastern Regional Taxonomic Center, South Carolina Marine Resources Research Institute

Seven of the top ten ports, by tonnage, are located in the Gulf of Mexico, increasing the risk of introduction

of invasive invertebrates by ship fouling or ballast water. Species of jellyfish, sea anemones, starfish, crabs, polychaetes and mollusks have been introduced through vessel traffic. Invasive-species expert J.T. Carlton estimates that 7,000 dif-ferent species of marine life are transported daily around the world’s oceans and seas. Successful invaders have a short

life span, rapid growth, rapid sexual maturity, high reproductive capacity, can colonize a variety of

habitat types and are physiologically tolerant. The zebra mussel is one example of an

extremely successful invader.

ZEBRA MUSSELS are thought to

have invaded 1/3 of all freshwater aquatic

environments in the United States. These

invasive mussels can produce over one million

eggs in a spawning season, so they multiply

rapidly. Millions of dollars are spent annually to

repair damages and to control their populations.

Initially limited to freshwater, there is recent

evidence that they are becoming salt tolerant

and can invade upper estuarine waters.

InvertebratesPhoto: U. S. Geological Survey Archives

Zebra mussels

Invertebrates

Photo: Alvaro Migotto

Photo: Jason Steckler

Spotted jelly, Phyllorhiza punctataVulnerable Locations: Marine waters, Gulf of

Mexico. Native Range: Native to the tropical western Pacific Ocean, wide distribution in Australian coastal and lagoonal waters. Suspected Vector: Most likely arrived via ship ballast or hull fouling to the Caribbean Sea through the Panama Canal. A small population of P. punctata has existed in Terrebonne Bay, La., for several years; vector unknown. Origin of medusae, adult spotted jellies, that invaded northern Gulf of Mexico in summer of 2000 is attributed to circulation processes associated with the Gulf of Mexico Loop Current and spin-off eddies, although transport from the Terrebonne Bay population must be considered. Description: Basketball-sized jellyfish with a white-spotted, opaque bell; mild to no sting. Negative Impacts: Direct economic impact on the trawl fisheries. Jellyfish clog nets, damage boat intakes and fishing gear, and can cause closure of pro-ductive areas to fishing activities. Indirect effects include predation on the eggs of important forage species and consumption of bivalve larvae. Fish larvae and mature

filter-feeding fish must compete with these jellies for the same food source. Status: First reported in Gulf of Mex-ico in 1993 when a single specimen was collected from waters 70 km south of Louisiana by the National Marine Fisheries Service vessel R/V Oregon II. Populations are established east and west of the Mississippi River.

Drymonema dalmatinum - No official common nameVulnerable Locations: Marine waters, northern Gulf

of Mexico. Native Range: Native to the Pacific and At-lantic oceans. Reported from the Adriatic Sea, Mediter-ranean Sea, Caribbean Sea and the Atlantic Ocean off Gibraltar. Also recorded from Argentina, Brazil and Co-lombia. Suspected Vector: Natural transport via circula-tion processes associated with the Loop Current and its spin-off eddies or through vessel fouling. Description: The umbrella is flatly rounded and shield shaped. Color ranges from reddish-white to yellow-white; specimens in the northern Gulf of Mexico are pink. More than 150 long stinging tentacles; dense ribbon-like gonadal and mouth exten-sions that are shorter than the tentacles also extend beneath the bell. Can exceed 700 mm in bell diameter with tentacles in excess of 30 m long. Resembles the lion’s mane jellyfish, Cyanea capillata. Negative Impacts: More than 25 million jellyfish were estimated in a bloom of D. dalmatinum in 1999 off Puerto Rico. If such a bloom occurred in the northern gulf, there would be a direct economic impact on the shrimp fishery including clogged nets, damage to boat intakes and fishing gear, and closure of areas to fishing activities. Status: Un-

known, reported from Alabama and Mississippi.

Spotted jelly

Drymonema dalmatinum

Brown mussel, Perna pernaGreen mussel, Perna viridis

Vulnerable Locations: High salinity (27-33 ppt) estuaries and marine waters, Gulf of Mexico. Native Range: Green mussels (Perna viridis) are natu-rally distributed throughout the Indo-Pacific. Brown mus-sels (Perna perna) are native to tropical and subtropical regions of the African coastline. Suspected Vector: Vector for both mussel species is thought to be international shipping via ballast water release or hull fouling. Description: The genus can be distinguished from other North American members of the family by the absence of one of two muscles used to close the shell. The two Perna species are difficult to separate using external characteristics; shells are similar and can be highly variable. Reliable separation of the two species requires examination of internal anatomy. The brown mussel has enlarged sensory papillae along mantle margins. Color of P. perna varies from reddish to dark brown to black with marginal areas of yellow and green. Perna viridis adults are usually various shades of brown in central portion of shell; juveniles typically green to blue-green. Occasionally both adults and juve-niles are brown, making them difficult to separate from P. perna. Negative Impacts: Both mussels are biofoulers that can alter community structure and create fouling problems in industries that use seawater as coolant. Brown mussels first appeared in Texas in 1990 on the Port Aransas jetty and within four years had colonized 1,300 km from Matagorda Bay to Vera Cruz, Mexico. They are also found on offshore petroleum platforms in the Gulf of Mexico. Presence of Texas populations varies; water temperatures at or above 30º C limit

population growth. Green mussels were first discovered in 1999 in Tampa Bay, Fla. Current range extends from Venice, La., to St. Petersburg, Fla. The green mussel’s greater thermal tolerance will allow it to disperse throughout the Gulf of Mexico. Status: Green mussels are currently established only in Florida. The brown mussel is currently confined to Texas waters with populations limited by summer temperatures.

Spiny hands swimming crab, Charybdis hellerii Vulnerable Locations: Lower estuarine, marine

waters of the Gulf of Mexico. Native Range: Japan, Philippines, New Caledonia, Australia, Hawaii and throughout the Indian Ocean, including the Red Sea. Suspected Vector: Both ballast water and drift of juveniles from Cuba have been suggested as a means of introduction to American wa-ters. Descrip-tion: Fifth legs flattened; side frontal margin has six sharp,

Brown mussel

Photo: Southeastern Regional

Taxonomic Center

CRUSTACEANS AND MOLLUSKS ACCOUNT FOR MOST OF THE INVERTEBRATE INTRODUCTIONS IN THE GULF OF MEXICO.

Photo: David Knott, Southeastern Regional Taxonomic Center, South Carolina Marine Resources Research Institute

Spiny hands swimming crab

Photo: Amy Benson, USGS

Green mussel

black-tipped teeth; frontal region has six prominent teeth. Overall color is dark green with dark purple on walking and swimming legs. Fingers of chelipeds (claws) are dark purple. Negative Impacts: Unknown. Status: Reported in Gulf of Mexico from Anna Maria Island, Fla., (mouth of Tampa Bay). Species has the potential to successfully colonize marine ecosystems of South Florida and the Gulf of Mexico.

Bocourt swimming crab, Callinectes bocourtiVulnerable Locations: Estuarine waters, Gulf of

Mexico. Native Range: Jamaica, Belize to Brazil; cen-ter of abundance in coastal waters of northern South America. Suspected Vector: Ballast water and drift of juveniles and adults from Caribbean. Description: Flat-tened fifth legs; frontal margin has six triangular frontal teeth with tips reaching a nearly common level; color highly variable, but generally olive green to brown with reddish markings; chelipeds red to dark reddish brown

above and whitish below with a tinge of blue. Negative Impacts: May compete with the blue crab, Callinectes sapidus, for food and refuge. Although C. bocourti is commercially exploited in Central and South America, it is a smaller crab and less desirable for pro-cessing in the United States. Competition among C. bocourti, C. sapidus and C. similis in northern gulf estuaries may limit populations of one or more of these species. Status: Reported from Mississippi and Ala-bama; extraterritorial occurrences in the northern Gulf of Mexico are sporadic and suggest that the species is not currently reproducing.

Green crab, Carcinus maenasVulnerable Locations: Estuarine and shallow coastal

waters of the Gulf of Mexico. Native Range: Atlantic coasts of Europe and northern Africa from Norway and the British Isles south to Mauritania. Suspected Vec-tors: Dispersed as adults by a variety of anthropogenic and natural mechanisms including: 1) ballast, 2) ships’ hulls, 3) packing materials (seaweeds) used to ship live marine organisms, 4) bivalves moved for aquaculture, 5) rafting, 6) migration on surface currents and 7) move-ment of submerged aquatic vegetation for coastal zone management initiatives. Once established in an area, green crabs can spread by planktonic transport of larvae. Description: Surface of carapace finely granular, about ¾ as long as wide with five yellow-tipped side frontal teeth; frontal area between eyes has three rounded teeth. Carapace color is variable, usually mottled, dark brown to dark green, with granules for the most part yellow. Females have orange background color and whitish granules. Walking legs are green, speckled with black; fourth pair of legs is shorter than the first; last pair is somewhat flattened and with hairs (setae). Negative Impacts: Implicated in the destruction of the soft-shell

Bocourt swimming crab

Photo: David Knott, Southeastern Regional Taxonomic Cen-

ter, South Carolina Marine Resources Research Institute

Successful Invader

clam (Mya arenaria) fisheries in New England and the reduction of populations of other commercially important bivalves including the scallop, Argopecten irradians, and the northern quahog, Mercenaria mercenaria. Ability to outcompete native species for food resources, a high reproductive capacity and wide environmental tolerances give green crabs the capacity to fundamentally alter community structure. They are voracious predators on other crab species. Status: Dispersed globally, U.S. reports include Atlantic and Pacific coast estuaries. It is one of the most successful invaders in coastal ecosystems. Temperature may limit southward expansion of northeast populations. Green crab

Photo: Kathlyn Smith

THE FRESHWATER ZEBRA MUSSEL IS BECOMING SALT TOLERANT.

Photo: U. S. Geological Survey Archives

Zebra mussel, Dreissena polymorpha Vulnerable Locations: Fresh and estuarine waters of the Gulf of Mexico.

Native Range: Black, Caspian and Azov seas. Suspected Vector: Original U.S. introduction into the Great Lakes through ballast water; further dispersal through larval transport and hull fouling. Description:

Small bivalve, usually striped (hence the name zebra). Some speci-mens dark or light colored with no stripes. Can grow to two inches

long, most under one inch; generally found in clusters. Only fresh-water mollusc able to attach to underwater objects and surfaces.

Negative Impacts: Zebra mussels pose a multibillion-dollar threat to U.S. industrial, agricultural and municipal water supplies

and are a costly nuisance for freshwater shipping, boating and fishing. Large infestations disrupt aquatic food chains, causing

shifts in native species populations. Status: Established in the Great Lakes and most of the large navigable rivers in the eastern U.S. Found in the Gulf of Mexico in coastal Louisi-

ana with a single occurrence in Mississippi Sound.

Did You Know?Whiteleg shrimp, Litopenaeus vannamei

Vulnerable Locations: Estuarine and shallow coastal waters of the Gulf of Mexico. Native Range: Eastern Pacific from Sonora, Mexico, to Tumbes in northern

Peru. Suspected Vector: Aqua-culture release. Description: The rostrum, the spinelike projec-tion of the front of the carapace, is moderately long

and armed with upper and lower teeth; lower teeth num-ber two to four, occasionally five to eight. Closely resem-bles the common gulf white shrimp, but is a lighter color, especially the legs, and is sometimes called the “white-legged” shrimp. Negative Impacts: Exotic shrimp viruses associated with L. vannamei may pose a risk to Gulf of Mexico and southeastern U.S. Atlantic wild penaeid shrimp fisheries. Other crustacean fisheries may also be at risk from introduced viruses. Status: Aquaculture of the Pacific white shrimp in the United States began in Texas and in Florida. Although collected periodically in commercial shrimp trawls off Texas, there is currently no evidence that populations have established themselves in the wild in the northern Gulf of Mexico.

Giant river prawn, Macrobrachium rosenbergii Vulnerable Locations: Wide range of freshwater and

estuarine ecosystems including swamps, lakes, ponds, ditches, bays and bayous. Requires brackish water to com-plete early life stages. Native Range: South and Southeast Asia, Oceania and the western Pacific. Suspected Vector: Aquaculture release. In some areas this species is sold in the aquarium trade. Description: Large shrimp; rostrum

long with 11-14 upper teeth and eight to 10 lower teeth. First and second legs have pincers; pincers in adult males are blue or orange. Orange spots may be visible on tail. Negative Impacts: Unknown at pres-ent; winter low temperatures in the northern Gulf of Mexico may prevent establishment of populations in the wild. Status: Reported from a single bayou in Mississippi.

Photo: Southeastern Regional Taxonomic Center, South Carolina Marine Resources Research Institute

Whiteleg shrimpPhoto: Robert Adami, Texas Parks & Wildlife Department

Giant river prawn

Channeled apple snail, Pomacea canaliculataVulnerable Locations: Wide range of freshwa-

ter ecosystems including swamps, lakes, ponds and ditches. Native Range: South America. Suspected Vec-tor: Aquarium and aquaculture releases. Description: Shell is round and, in older snails heavy. Deep sutures (grooves) separate five to six whorls. Shell opening is large and round to oval. All apple snails have a tubelike siphon. There are several species of introduced apple snails, and an expert may be needed to identify speci-mens from the wild. Channeled apple snails lay up to 1,000 small pink eggs on hard surfaces such as docks, plant stems, rocks and seawalls. Negative Impacts: The channeled apple snail is an agricultural pest that is a destructive plant eater. This species will eat all types of aquatic vegetation and has few natural enemies. Mississippi has banned importation of all members of the apple snail family. Louisiana has identified the channeled apple snail as a threat to rice production. Channeled apple snails are salinity tolerant and can withstand temperatures found in the northern Gulf of Mexico. Status: Established in Florida and Texas; reported from Alabama.

Did You Know?Photo: Juliana Harding

Rapa whelk

Did You Know? FLORIDA HAS THE HIGHEST NUMBER OF INTRODUCED INVERTEBRATES. MISSISSIPPI HAS THE LOWEST.

Photo: Florida Department of Environmental Protection

Channeled apple snail

Rapa whelk, Rapana venosa

Vulnerable Locations: Estuarine waters of the Gulf of Mexico. Native Range: Marine and estuarine waters of the western Pacific, the Sea of Japan, Yellow and East China seas, the Bohai Sea. Suspected Vector: Release of larvae from ballast water or transport of egg masses from one area to another. Description: Shell heavy, round and with a short spire. Body whorl is large and inflat-ed. Shell opening is large, deep orange and ringed with small teeth. Background color of shell varies from gray to reddish-brown; most specimens have black veins that run throughout the shell. Shell length of specimens from Virginia is four to six inches. Negative Impacts: Rapa whelks are preda-tory snails that feed on a variety of bivalves. In the Chesapeake Bay their preferred prey is the hard clam, but they will attack other mollusks. Their occurrence in estuaries in the Gulf of Mexico may impact oyster populations. Status: Currently established in Chesapeake Bay in U.S. waters.