Quagga mussel

The quagga mussel, scientific name Dreissena bugensis, and also known as Dreissena rostriformis bugensis, is a species (or subspecies) of freshwater mussel, an aquatic bivalve mollusk in the family Dreissenidae. It has an average life span of 3 to 5 years. It is indigenous to the Dnieper River drainage of Ukraine. The species is named after the quagga, an extinct subspecies of African zebra, possibly because, like the quagga, its stripes fade out towards the ventral side. The quagga mussel is currently of major concern in the Great Lakes of North America as an invasive species brought by overseas shippers that use the St. Lawrence Seaway. The quagga mussel shell is generally black, yellow, and/or zig-zagged. However, there is a large range of shell morphologies, including a distinct morph in Lake Erie that is pale or completely white. The shell has a rounded carina and a convex ventral side. The quagga mussel resembles the zebra mussel, just as its namesake (quagga) resembles the zebra. The quagga mussel shell can be distinguished from the zebra mussel shell because it is paler toward the end of the hinge. It is also slightly larger than the zebra mussel, about 20 millimetres (0.8 in) wide, roughly about the size of an adult human's thumbnail. The quagga mussel is a filter feeder. It uses its cilia to pull water into its shell cavity through an incurrent siphon and it is here that desirable particulate matter is removed. Each adult mussel is capable of filtering one or more liters of water each day, where they remove phytoplankton, zooplankton, algae, and even their own veligers. Any undesirable particulate matter is bound with mucus, known as pseudofeces, and ejected out the incurrent siphon. The particle-free water is then discharged out the excurrent siphon. The quagga mussel is a prolific breeder, possibly contributing to its spread and abundance. Dreissena are dioecious (either male or female) with external fertilization. A fully mature female mussel is capable of producing up to one million eggs per year. After fertilization, pelagic microscopic larvae, or veligers, develop within a few days and these veligers soon acquire minute bivalve shells. Free-swimming veligers drift with the currents for three to four weeks feeding by their hair-like cilia while trying to locate suitable substrata to settle and secure byssal threads. Mortality in this transitional stage from planktonic veliger to settled juveniles may exceed 99%. Zebra mussels, the first dreissenid mussel introduced in North America, rapidly spread throughout many major river systems and the Great Lakes, causing substantial ecological and environmental impacts. The quagga mussel was first observed in North America in September 1989 when it was discovered in Lake Erie near Port Colborne, Ontario. It was not identified as a distinct species until 1991.