The New World filarial genus Molinema Freitas & Lent, 1939 (Nematoda : Onchocercidae), with a description of four new species parasitic in the Echimyidae (Rodentia)

Four new species of Molinema (Filarioidea: Onchocercidae), parasites of ech imyid rodents in South America, are described: M. algardneri n. sp. from Pr oechimys amphichoricus, M. barbarae n. sp. from P. cayennensis, both in Ven ezuela (Rio Negro and Cerro La Neblina, respectively), M. peruviensis n. sp . from P. steerei in Peru (lower Urubamba), and M. nattereri n. sp. (= Fila ria diacantha Molin, 1858 pro parte) from Echimys? didelphoides (= Lonchere s rufa) in Brazil (Matto Grosso). They differ from each other and from the previously described species in the following characters: flat or concave h ead, cephalic ratio (distance between cephalic papillae in median view/late ral view), size and shape of the buccal capsule, length of the oesophagus, cuticular ornamentation of the female body, length of the ovijector, thick or slim female tail, area rugosa, long or short filament in the left spicul e, heel in the right spicule, respective position of postcloacal papilla pa irs 5 and 6, shape of the caudal lappets, terminal point present or absent, and the microfilariae. Molinema, which belongs to the worldwide Dipetalone ma line, is distributed in two of the ten families of the Caviomorpha (Sout h American Hystrichognathi have extended their distribution in South Americ a since the early Oligocene). Nine species are parasitic in the Echimyidae (suborder Caviida); they have a short oesophagus and a complete or reduced set of precloacal papillae (four or three pairs). Two species are parasitic in the Erethizontidae (Erethizontida) and might be more primitive in havin g a well-developed oesophagus. However, the type-species M. diacantha, of w hich a female specimen was studied, has a large buccal capsule and has evol ved concave head, while M. arbuta has a reduced buccal capsule and primitiv e flat head. This last species is a parasite of a Nearctic porcupine and pr obably represents a small line of Molinema which migrated to the north with its hosts when communications were established between the two American co ntinents 3 mya (Pleistocene). M. sprenti, the unique parasite of the Castor idae in North America, is considered to be derived from this group by captu re.