Best Invasive

The warty comb jelly, Mnemiopsis leidyi, is a transparent marine ctenophore native to Atlantic coastal waters of the Americas. It moves using rows of beating cilia and feeds on zooplankton, fish eggs, and larvae; despite its jellylike body, it is not a true jellyfish. Introduced into the Black Sea b...

The long-spined sea urchin (Centrostephanus rodgersii) is a large diadematid echinoid found on rocky reefs along southeastern Australia, including New South Wales, Tasmania, and the eastern Bass Strait. Where urchin densities rise, grazing can remove kelp and other macroalgae, forming barrens that r...

Caulerpa taxifolia is a species of green algae belonging to the Chlorophyta group. It’s notable for its rapid growth and aggressive spread when introduced into new environments, particularly becoming an invasive problem in coastal ecosystems like the Mediterranean Sea. Originally cultivated as an aq...

The Chinese mitten crab is a medium-sized freshwater crustacean native to the coastal rivers and estuaries of East Asia, including China and Korea. It is easily distinguished by the dense patches of dark hair on its claws, which resemble mittens. The species is catadromous, meaning it migrates from...

Craspedacusta sowerbii is a small freshwater hydrozoan commonly called the freshwater jellyfish. Native to the Yangtze River basin in China, it has been introduced widely and recorded on every inhabited continent, often in lakes, reservoirs, ponds, and slow-moving water. Its life cycle includes a ti...

Rhopilema nomadica, commonly called the nomad jellyfish, is a large rhizostome jellyfish native to tropical waters of the Indian Ocean. It entered the Mediterranean through the Suez Canal and was recorded off Israel in the 1970s, subsequently spreading through parts of the eastern Mediterranean. Sea...

"Caulerpa racemosa" is a species of green seaweed in the family Caulerpaceae, recognizable by its distinct grape-like clusters of spherical branchlets. Native to shallow tropical and subtropical regions worldwide, it has become a notable invasive species in the Mediterranean Sea since the 1990s. The...

The spotted jellyfish, Phyllorhiza punctata, is a large scyphozoan jellyfish native to the western Pacific, recognizable by the pale spots scattered across its rounded bell. It contains symbiotic algae in its tissues and also filter-feeds on zooplankton, using multiple oral arms rather than long mar...

Zoropsis spinimana is the false wolf spider, a Mediterranean species notable for its expansion into North America after being discovered in California in 1992.

The Brown Widow is a venomous spider native to Africa but now found globally, notable for its neurotoxic venom and the distinctive orange hourglass marking on its dark abdomen.

The greenhouse frog (*Eleutherodactylus planirostris*) is a small terrestrial amphibian native to Cuba, the Cayman Islands, and the Bahamas. It has become a prominent invasive species in other regions, notably Florida, Hawaii, and Central America, frequently spreading through the commercial plant tr...

Asparagopsis armata is a red alga (Rhodophyta) native to Australia and the Southern Hemisphere that became established as an invasive species along European Atlantic coastlines by the early 20th century and is now widely naturalized there. It is commonly known as 'harpoon weed' due to the barbed, ho...

A small hydrozoan of the North Pacific and North Atlantic that clings to seagrass using adhesive pads and delivers a sting disproportionately potent for its centimeter-scale size.

Colpomenia peregrina is a species of brown macroalgae belonging to the order Scytosiphonales. It is widely distributed and commonly found in intertidal zones around the world, where it grows attached to rocks or other algae. The species is characterized by its small, hollow, and globular thallus, wh...

Muggiaea atlantica is a calycophoran siphonophore of the eastern Atlantic that forms dense blooms in European coastal waters, causing significant mortality in farmed salmon.

Caulerpa prolifera is a species of siphonous green marine alga native to the Mediterranean Sea and the eastern Atlantic Ocean. It features creeping stolons that anchor to the seafloor, from which emerge upright, flat, oval-shaped fronds resembling seagrass leaves. The organism is a single multinucle...

The harlequin ladybird, Harmonia axyridis, is a highly variable ladybird species native to eastern Asia. It was introduced elsewhere as a biological control agent because both adults and larvae consume aphids, but it subsequently became invasive across parts of Europe, North America, and other regio...

Codium fragile is a marine green alga with dark green, forked, cylindrical branches whose soft, spongy texture results from its siphonous internal structure. Native to parts of the Pacific, several subspecies have spread widely beyond their original ranges and can colonize rocky shores, shellfish be...

The giant resin bee, Megachile sculpturalis, is a large solitary bee native to eastern Asia and a member of the family Megachilidae. Females use existing cavities, including holes in dead wood and artificial nesting blocks, and construct brood cells with resin and other plant material. The species h...

Euglandina rosea, the Rosy Wolf Snail, is a fast-moving predatory land snail native to the southeastern United States, particularly Florida and the Gulf Coast. It hunts other snail species by following their slime trails, using an elongated body adapted for pursuing prey. It was deliberately introdu...

Achatina fulica, the Giant African Land Snail, is a large terrestrial pulmonate gastropod native to East Africa, capable of reaching lengths of up to 20 centimeters. It is a highly prolific breeder and an opportunistic feeder, consuming a wide variety of plant material. Listed among the world's most...

A small leptomedusa native to the Black and Caspian seas, now invasive in numerous estuaries worldwide, including San Francisco Bay and Chesapeake Bay.

Marivagia stellata is a scyphozoan first formally described in 2010 from Israel's Mediterranean coast, establishing a distinct new genus of uncertain biogeographic origin.

The Asian paddle crab (Charybdis japonica) is a swimming crab native to coastal waters of East Asia and other parts of the western Pacific. Like other members of the family Portunidae, it has a flattened final pair of legs that function as paddles, allowing it to swim efficiently. It inhabits marine...

Orange Hawkweed (Hieracium aurantiacum) is a European native introduced to North America that is considered an invasive weed in many regions, recognizable by its vivid orange-red flower heads.

A brackish-water hydromedusa native to the Caspian–Black Sea region, recorded as an invasive species in San Francisco Bay, California, since the 1990s.

A freshwater gastropod native to South America that became a major invasive agricultural pest in rice-growing regions across Asia and Hawaii during the late 20th century.

A small hydromedusa first described from the brackish Lake Manzala in Egypt, since recorded in coastal lagoons and estuaries across multiple continents.

The Cuban Tree Frog (Osteopilus septentrionalis) is the largest tree frog in North America and an invasive species established in Florida since the 1930s.