The ascaridoid nematodes of rodents with a redescription of Porrocaecum ratti

Two ascaridoid nematodes occurring in rodents in South–East Asia, namely Porrocaecum ratti and Toxocara mackerrasae, were compared; the former was redescribed. These and other ascaridoid species occurring in rodents were classified and it was suggested that relative to the other mammalian orders, the rodents are well endowed with ascaridoids. There is, as yet, insufficient evidence for conjecture as to whether species occurring in rodents represent primitive forms from which the species occurring in predatory animals may have been evolved through host–succession–extension, or whether they have been secondarily derived through loss of a predatory definitive host through host–succession–reduction