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We redescribe Andrya octodonensis based on new material from Phyllotis xanthopygus from Argentina. Andrya vesicula n. sp. from Phyllotis xanthopygus and Andrya boliviensis n. sp. from Phyllotis osliae are also described and illustrated. The occurrence of these species in South America suggests that cestodes of the genus Andrya were introduced on that continent by sigmodontine rodents from the Nearctic, probably after the formation of the Isthmus of Panama.

Anoplocephalid cestodes have a worldwide distribution, but relatively few species are known from South American rodents. By examining the collections of the Harold W. Manter Laboratory of Parasitology and the United States National Parasite Collection, 6 new species of Monoecocestus Beddard, 1914, are described, along with a redescription of Monoecocestus mackiewiczi Schmidt and Martin, 1978, based on the type specimens. The discussion includes commentary about uterine development, an important taxonomic character of the family, the vaginal dilation in immature segments (a character of potential taxonomic importance), and the implication of host usage to the evolutionary history and biogeography of species in this genus.

Currently, there are 6 recognized species in the genus Rhopalias. These parasites are found in the small intestines of numerous species of marsupials throughout North and South America. Small mistakes in various classical taxonomic works have given rise to recent and numerous misidentifications of these species. In this work, we examine a total of 99 specimens across all species from museum collections in an attempt to determine informative taxonomic characters to distinguish these species. Despite confusion in the literature, accurate identification of these species can be achieved by observing the presence or absence of oral and flanking spines anterior to the oral sucker.

The ecological niche of a parasite exists only at the nexus of certain abiotic and biotic conditions suitable for both the definitive and intermediate hosts. However, the life cycles of most parasites are not known , or are poorly known, and using known ranges of hosts to find endemic parasitic infections has been difficult. However, with ecological niche modeling, we can create potential range maps using known localities of infection. Testing the validity of such maps requires knowledge of the localities of other parasites with common history. Here, we find that the ecological niche of a tapeworm parasite of voles, Paranoplocephala macrocephala (Cestoda: Anoplocephalidae), allows prediction of the presence (in ecological and geographic space) of 19 related parasite species from 3 genera in 23 different hosts throughout the Nearctic. These results give credence to the idea that this group shares similar life cycle requirements despite phylogenetic distance. This work further validates ecological niche modeling as a means by which to predict occurrence of parasites when not all facets of the life cycle are confirmed. Such inductive methods create the opportunity for deducing potential reservoir or intermediate hosts, and complementing studies of parasite biodiversity and community ecology.

Because we have new and detailed data on species in the genus, herein we redescribe both Monoecocestus macrobursatus and M. minor based on existing museum specimens. We also redescribe M. threlkeldi (Parra, 1952) using material collected in Bolivia. Based on the specimens representing M. thelkeldi, we affirm that Perutaenia Parra, 1953 should remain a junior synonym of Monoecocestus.

COMO PARTE DEL MONITOREO DE LA BIODIVERSIDAD DE BOLIVIA, VARIAS RATAS ESPINOSAS (PROECHIMYS SIMONSI THOMAS, 1900) FUERON EXAMINADAS EN BUSCA DE PARASITOS DURANTE EL VERANO BOREAL DEL ANO 2000. EN EL PRESENTE TRABAJO SE DESCRIBEEL CESTODO LENTIELLA LAMOTHEI N. SP. RECOLECTADO EN ESTOS HOSPEDEROS. ESTA ESPECIE PUEDE DISTINGUIRSE DE L. MACHADOIRUGO, 1964 POR TENER UNA MAYOR LONGITUD TOTAL PERO MENOR ANCHO MAXIMO, MAYOR NUMERO DE PROGLOTIDOS, BOLSA DEL CIRRO MAS PEQUENA, ESCOLEX DE MENOR DIAMETRO, Y UN MAYOR APARATO PIRIFORME EN LOS HUEVOS. ADEMAS, SE REVALIDA FORMALMENTE AL GENERO LENTIELLA RUGO, 1964, ANTERIORMENTE SINONIMIZADO CON MONOECOCESTUS BEDDARD, 1914.

Helaeomyia petrolei (oil fly) larvae inhabit the asphalt seeps of Rancho La Brea in Los Angeles, Calif. The culturable microbial gut contents of larvae collected from the viscous oil were recently examined, and the majority (9 of 14) of the strains were identified as Providencia spp. Subsequently, 12 of the bacterial strains isolated were tested for their resistance or sensitivity to 23 commonly used antibiotics. All nine strains classified as Providencia rettgeri exhibited dramatic resistance to tetracycline, vancomycin, bacitracin, erythromycin, novobiocin, polymyxin, colistin, and nitrofurantoin. Eight of nine Providencia strains showed resistance to spectinomycin, six of nine showed resistance to chloramphenicol, and five of nine showed resistance to neomycin. All 12 isolates were sensitive to nalidixic acid, streptomycin, norfloxacin, aztreonam, cipericillin, pipericillin, and cefotaxime, and all but OF008 ( Morganella morganii ) were sensitive to ampicillin and cefoxitin. The oil fly bacteria were not resistant to multiple antibiotics due to an elevated mutation rate. For each bacterium, the number of resistant mutants per 10 8 cells was determined separately on rifampin, nalidixic acid, and spectinomycin. In each case, the average frequencies of resistant colonies were at least 50-fold lower than those established for known mutator strain ECOR 48. In addition, the oil fly bacteria do not appear to excrete antimicrobial agents. When tested, none of the oil fly bacteria produced detectable zones of inhibition on Pseudomonas aeruginosa , Escherichia coli , Staphylococcus aureus , or Candida albicans cultures. Furthermore, the resistance properties of oil fly bacteria extended to organic solvents as well as antibiotics. When pre-exposed to 20 μg of tetracycline per ml, seven of nine oil fly bacteria tolerated overlays of 100% cyclohexane, six of nine tolerated 10% xylene, benzene, or toluene (10:90 in cyclohexane), and three of nine (OF007, OF010, and OF011) tolerated overlays of 50% xylene–50% cyclohexane. The observed correlation between antibiotic resistance and organic solvent tolerance is likely explained by an active efflux pump that is maintained in oil fly bacteria by the constant selective pressure of La Brea's solvent-rich environment. We suggest that the oil fly bacteria and their genes for solvent tolerance may provide a microbial reservoir of antibiotic resistance genes.