Life Cycle of Uncinaria lucasi Stiles, 1901 (Nematoda : Ancylostomatidae) of Fur Seals, Callorhinus ursinus Linn., on the Pribilof Islands, Alaska

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Abstract
The life cycle of Uncinaria lucasi in fur seals consists of three basic parts: (1) the freeliving phase with eggs and free-living third-stage larvae in the soil; (2) the tissue phase wherein parasitic third-stage larvae occur in all age groups of seals, particularly in the blubber of the belly region, and in the case of females, also in the mammary glands and milk cisterns; and (3) the intestinal phase consisting of fourth-stage larvae, adolescent, and adult worms occurring in the intestine of young pups. Eggs passed in the feces of pups during the summer do not hatch until fall and the larvae may or may not overwinter, depending on unknown microclimatological factors. Infection of all seals with the tissue phase is primarily percutaneous, entry being mainly through the flippers, but it may take place per os. Infection of young pups with the intestinal phase is through the parasitic third-stage larvae which are passed postpartum in the milk for only a short time. The worms reach adulthood in 13 to 15 days and are lost from all pups when the latter are about 3 months old. Seals do not become reinfected and all adults are free of hookworms.

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