Leptodora kindti

Leptodora is a genus containing two species of large, nearly transparent predatory water fleas. They grow up to 21 mm (0.83 in) long, with two large antennae used for swimming and a single compound eye. The legs are used to catch copepods that it comes into contact with by chance. Leptodora kindtii is found in temperate lakes across the Northern Hemisphere and is probably the only cladoceran ever described in a newspaper; L. richardi is only known from eastern Russia. For most of the year, Leptodora reproduces parthenogenetically, with males only appearing late in the season, to produce winter eggs which hatch the following spring. Leptodora is the only genus in its family, the Leptodoridae, and suborder, Haplopoda. Adults of Leptodora are the largest planktonic cladocerans native to North America; reports vary concerning the largest size, but adult females typically grow to 12 mm (0.47 in) long, but with some reports of females up to 21 mm (0.83 in). They are about 98% transparent, as a defense against predation by fish. Lilljeborg notes: The male is similarly transparent. The abdomen is elongated, but the carapace is small and only covers the brood pouch. The five pairs of thoracic appendages form a 'feeding basket' which is used to capture prey. The second antennae are used for swimming, while the first antennae are rudimentary in females but elongated in males, where they are used in sexual reproduction. There is a single large compound eye which takes up much of the animal's head. It comprises around 500 facets, which are spherically arranged, and the whole eye is movable by up to 10° in any direction. Leptodora kindtii is widespread in northern temperate lakes. In North America, it occurs as far south as Texas and Oklahoma. It is also found across Europe, in parts of North Africa, northern Arabia, and in Asia (north of the Himalaya). Leptodora kindtii is a voracious predator and is capable of controlling numbers of its preferred prey items, which are generally juveniles of Daphnia, Bosmina, Ceriodaphnia, Diaphanosoma, Diaptomus, Polyphemus and Cyclops. It seems to encounter its prey by chance, with contact initiating a reflex, in which the abdomen is brought forward to close the feeding basket. In many cases, the prey escapes this haphazard response. Juvenile Daphnia are slower than adults to respond to the predator's attack, and are therefore more likely to be caught. The most important predators of Leptodora are fishes, including whitefish, perch, ziege and bleak. In Lake Biwa, Japan, L. kindtii is parasitised by the nematode Raphidascaris biwakoensis, a parasite of fish.