Open source packages that run BGP include GNU Zebra, Quagga, OpenBGPD, BIRD, XORP, and Vyatta. The quagga mussel is a filter feeder. Chlorine dioxide may be used for control of zebra and quagga mussels in water intakes. The wreck is totally encrusted with quagga mussels. The larva form of quagga mussels were found in the water. Zebra and quagga mussels can attach to hard surfaces and build layers on underwater structures. Its design differs significantly from GNU Zebra and Quagga. In August 2007, preliminary testing was positive for zebra or quagga larvae in Lake Powell. A 2005 genetic study confirmed the quagga being the same species as the plains zebra. Zebra and quagga mussels first appeared in the United States in the 1980s. The river is part of the quagga mussel's native range. In recent centuries, two subspecies, the quagga and the tarpan, became extinct. The first subspecies to be described, the now-extinct quagga, had plain brown hindquarters. Zebras from Namibia appear to be the closest genetically to the quagga. These quagga seemed gentle and easy to domesticate.