Comparative morphology and ecology of two species of Litomosoides (Nematoda: Filarioidea) of rodents in Florida, with a key to the species of Litomosoides Chandler, 1931

Litomosoides brasiliensis (Nematoda: Onchocercidae) infecting chiropterans in the Legal Amazon region, Brazil

Chiropterans play an important role in the maintenance of the environmental balance, since they are pollinators, seed dispersers and predators. They contribute to transmission and spreading of microorganisms such as helminths, fungi, protozoa, bacteria and virus. The aim of the present study was to investigate natural filariid infection among bats in the Legal Amazon region, Brazil, by means of parasitological and molecular analyses. Blood samples were collected from 82 bats for blood smears and for DNA extraction via the polymerase chain reaction (PCR) assay. Microfilariae were observed in blood smears from Carollia perspicillata (2), Artibeus lituratus (1), Artibeus fimbriatus (2), Dermanura gnoma (2) and Glossophaga soricina (1). Five positive samples were detected through the PCR assay and four of these were also positive in blood smears. From genome sequencing and comparative analysis with sequences deposited in GenBank, one sample showed 99.31% similarity to the species Litomosoides brasiliensis. The present study expands the geographical distribution of L. brasiliensis, to include the state of Maranhão as an area of occurrence of this species and includes D. gnoma and A. fimbriatus as hosts in Brazil.

HOST-SWITCHING EVENTS IN LITOMOSOIDES CHANDLER, 1931 (FILARIOIDEA: ONCHOCERCIDAE) ARE NOT RAMPANT BUT CLADE DEPENDENT

The genus Litomosoides Chandler, 1931, includes species that as adults occur in the thoracic and abdominal cavity of mammalian hosts and are presumably vectored by mites. The vertebrate hosts include a variety of Neotropical mammals such as phyllostomid and mormoopid bats; cricetid, sciurid, and hystricognath rodents; and didelphid marsupials. It has been suggested that Litomosoides is not a monophyletic group and that rampant horizontal transfer explains their presence in disparate groups of mammals. Herein we present a phylogenetic reconstruction including mitochondrial genes of 13 vouchered species. This phylogeny is used to reconstruct the evolutionary history of these parasites and the ancestral states of key characters used in species classification, namely, the configuration of the spicules. The historical association of these filarioids with 6 groups of mammals, as well as their ancestral geographic distributions, were reconstructed using Bayesian statistical approaches comparing alternative models of biogeography and evolution and fossil states in selected nodes of the phylogeny. The optimal reconstruction suggests a model of dispersal, extinction, and cladogenesis (DEC) driving the evolution of Litomosoides; the results suggest an origin of Litomosoides in South America and association of ancestors with phyllostomids, and strong evidence of at least 2 host-switching events: 1 of these involving cricetid rodents and the other mormoopid bats. The latter event included a simultaneous geographic expansion of the parasite lineage across South and North America. The host-switching event from phyllostomid bats into cricetid rodents occurred once these rodents diversified across South America; subsequent diversification of the latter clade resulted in 2 branches, each showing expansion of the parasites back into North America. This result suggests that both parasites and cricetid rodents established an association in South America, underwent diversification, and then dispersed into North America. Further, this clade of cricetid-dwelling species includes parasites featuring the "sigmodontis" spicule type. The identification of a single host-switching event involving the disparate lineages of Chiroptera and Rodentia offers a framework to reconstruct the gene evolution and diversification of this lineage after the host-switching event. This will help in predicting the ability of these parasites to infect sympatric mammals.

A new species, Litomosoides odilae n. sp (Nematoda: Onchocercidae) from Oligoryzomys nigripes (Rodentia: Muridae) in the rainforest of Misiones, Argentina

A new species of Litomosoides was collected from the abdominal cavity of Oligoryzomys nigripes (Rodentia: Muridae) in a semideciduous secondary rainforest of Misiones, Argentina. Litomosoides odilae n. sp. belongs to the carinii group and is characterized by the amphids displaced dorsally; buccal capsule with an anterior segment transparent and an annular asymmetrical thickening; esophagus divided, with the posterior glandular portion slightly wider than the muscular; male cloacal aperture strongly protruded; and microfilaria sheathed with an attenuated tail. The morphology of the new species, which is similar to that of L petteri, a parasite of marsupials in Brazil, suggests that host-switching events may have occurred in the diversification of this genus.

Two new species of Litomosoides (Nematoda: Filarioidea) in Sigmodontines (Rodentia: Muridae) from Rio de La Plata marshland, Argentina

Two new species of coelomic filarioid belonging to Litomosoides are described from sigmodontine murids from the Rio de La Plata marshland, Argentina. Litomosoides bonaerensis n. sp., a parasite of Oligoryzomys delticola, belongs to the carinii group and is close to L. silvai, which differs by the head and tail papillae, buccal capsule and cavity, area rugosa, and morphology of the microfilaria. Litomosoides oxymycteri n. sp., from Oxymycterus rufus, belongs to the sigmodontis group. Differential diagnosis is based on the morphology of the buccal capsule, the head and tail papillae, and microfilaria. The ectoparasitic gamasid Ornithonyssus bacoti, in which several Litomosoides species develop, has been recovered from sigmodontines trapped in the study.

Phylogeny of species of the genus Litomosoides (Nemata [corrected]: Onchocercidae): evidence of rampant host switching

Filarioid nematodes of the genus Litomosoides occur in the abdominal and (or) thoracic cavities of marsupials, rodents, and bats of the Nearctic and Neotropical regions. In this study, the phylogenetic relationships among these nematodes were estimated with a parsimony analysis of morphological characters derived from species descriptions. This nonweighted analysis produced 20 shortest trees. The monophyly of the genus was not supported in that Litomosoides thomomydis and Litomosoides westi failed to group with the other members of the genus. When these 2 taxa (parasites of pocket gophers) were excluded, monophyly of Litomosoides was supported by 2 synapomorphies (structure of the walls and general shape of the stoma); however, ancestor-descendant relationships among the species in the genus were not well resolved. A posteriori reweighting of the characters produced a single tree, different from all 20 most parsimonious trees. Alternative host-parasite evolutionary models were tested against these results supporting the process of host switching as being most important in forming the patterns of mammal-nematode associations that have been detected in this group of nematodes.