The warty comb jellyfish, Mnemiopsis leidyi, is a marine invertebrate known as a ctenophore or comb jelly. Unlike true jellyfish (phylum Cnidaria), comb jellies are classified in the phylum Ctenophora and do not possess stinging cells. M. leidyi is notable for its biological characteristics and its impact on marine ecosystems.
Distinguishing Features and Appearance
It has a transparent, gelatinous body that is oval or walnut-shaped, typically reaching a length of about 10 to 12 centimeters and a diameter of 2.5 centimeters. Its body is composed of about 97% water, contributing to its delicate and translucent appearance. The “warty” part of its name refers to small bumps or papillae present on its body surface.
M. leidyi has eight rows of comb plates, or ctenes, which run vertically along its body. These comb plates are made of fused cilia and are used for locomotion, propelling the animal through the water. As light reflects off these moving cilia, it creates a shimmering, iridescent effect, often described as a rainbow. It lacks stinging tentacles, instead employing sticky cells called colloblasts on its feeding tentacles to capture prey.
Habitat and Feeding Habits
This species is native to the Atlantic coastal waters of North and South America. It tolerates a broad range of environmental conditions, including temperatures from 2 to 32 degrees Celsius and salinities from 2 to 38 parts per thousand, which allows it to thrive in diverse coastal and estuarine environments.
As a carnivorous predator, Mnemiopsis leidyi primarily consumes zooplankton, such as copepods, cladocerans, and bivalve larvae. It also preys on fish eggs and larvae. The comb jelly captures prey using large oral lobes that extend from its mouth. These lobes and smaller auricles create a low-velocity current, drawing small prey into the mouth where adhesive colloblast cells secure them. Copepods are a frequent food source, with calanoid and cyclopoid nauplii making up a significant portion of its diet.
Reproduction and Life Cycle
Mnemiopsis leidyi is a hermaphroditic species, allowing for self-fertilization. This contributes to its rapid population growth and successful colonization of new areas. Eggs and sperm are released into the water column, where fertilization occurs.
The life cycle progresses from an egg to a free-swimming cydippid larva, which resembles a smaller version of the adult, hatching within 20 to 24 hours. These larvae begin reproducing at a small size and continue to spawn continuously under adequate environmental conditions. A single large specimen can produce as many as 10,000 eggs in areas with abundant prey, with egg production starting when the animals reach 15 millimeters in length. This quick maturation and continuous reproduction contribute significantly to its success as an invasive species.
Ecological Role
The warty comb jellyfish has a significant impact on marine ecosystems, particularly as an invasive species outside its native range. It was accidentally introduced to the Black Sea in the early 1980s, likely through ship ballast water, and subsequently spread to the Caspian Sea, Sea of Azov, Sea of Marmara, and later the North and Baltic Seas.
Its appetite for zooplankton and fish larvae can disrupt local food webs. In the Black Sea, for instance, the invasion of M. leidyi was associated with a decline in fish populations, including commercially important species like anchovy, due to competition for food and direct predation on fish eggs and young. This disruption can lead to significant changes in the pelagic ecosystem, affecting biodiversity and the abundance of various marine organisms.