Evolution of Feeding Structures in the Marine Nematode Order Enoplida.

Marine nematodes of the order Enoplida may represent the earliest lineage of nematodes and have a variety of fixed and movable feeding structures in their stomas. This study used an 18S ribosomal RNA phylogeny of the orders Enoplida and Triplonchida (subclass Enoplia) to explore the evolution of these feeding structures in light of previous hypotheses based solely on morphology. The Enoplida and Triplonchida were found to be paraphyletic, as several taxa currently classified as Triplonchida, such as Rhabdodemania, were found to be part of the Enoplida clade. The position of Rhabdodemania within Enoplida was unclear, but a close relation to Enoplidae and Thoracostomopsidae was not supported, making it unlikely that its movable odontia are homologous with the mandibles of these families. A member of Anticomidae was well-supported as the base of the clade containing Phanodermatidae, Enoplidae, and Thoracostomopsidae, suggesting that taxa with buccal rods and mandibles evolved from nematodes with unarmed stomas. The Phanodermatidae were shown to be more closely related to the Enoplidae and Thoracostomopsidae than were the Leptosomatidae, suggesting that the buccal rods of the phanoderms (rather than the mandibular ridge/odontia complex of the Leptosomatidae), may be the origin of the mandibles.

Molecular phylogeny of Pseudocapillaroides xenopi (Moravec et Cosgrov 1982) and development of a quantitative PCR assay for its detection in aquarium sediment.

We used high-fidelity PCR to amplify a portion of the small ribosomal subunit (18S rRNA) of Pseudocapillaroides xenopi, a nematode that parasitizes the skin of Xenopus laevis. The 1113-bp amplicon was cloned, sequenced, and aligned with sequences from 22 other nematodes in the order Trichocephalida; Caenorhabditis elegans was used as the outgroup. Maximum-likelihood and Bayesian inference phylogenetic analyses clustered P. xenopi in a clade containing only members of the genus Capillaria. Our analyses support the following taxonomic relationships: 1) members of the family Trichuridae form a clade distinct from those in the family Trichocephalida; 2) members of the genera Trichuris and Capillaria form 2 distinct clades within the family Trichuridae; and 3) the genus Trichuris includes 2 distinct clades, one representing parasites that infect herbivores and the other representing parasites that infect omnivores and carnivores. Using 18S rRNA sequence unique to P. xenopi, we developed a Taq Man quantitative PCR assay to detect this P. xenopi sequence in total DNA isolated from aquarium sediment. The assay's lower limit of detection is 3 copies of target sequence in a reaction. The specificity of our assay was validated by using negative control DNA from 9 other pathogens of Xenopus. Our quantitative PCR assay detected P. xenopi DNA in the sediment of 2 of 12 aquaria from the source institution of the specimen used to develop the assay; these aquaria had been treated with ivermectin 6 mo previously.

A new species of the genus Tripylina Brzeski, 1963 (Nematoda: Enoplida: Trischistomatidae) from Zhejiang Province, eastern China.

Tripylina zhejiangensis n. sp. is described and illustrated from Zhejiang province, eastern China. It has a robust body, smooth cuticle with numerous pores, two small subventral teeth in the posterior part of the large triangular dorsal tooth, one ventral-median seta in the cervical region and a pair of setae on the tail. Females are characterized by a body length of 1325-1573 µm, a = 23.3-31.2, b = 5.5-6.6, c = 13.6-19.4, c'= 2.7-3.6 and V = 61.1-68.1%. Small subunit (SSU) and D2/D3 expansion segments of large subunit (LSU) of ribosomal DNA were used to analyze the phylogenetic relationships of sequenced species in the genus Tripylina. Tripylina zhejiangensis n. sp. varied significantly from other related nematodes both in morphological characterizations and phylogenetic analyses.

Development of Trichosomoides nasalis (Nematoda: Trichinelloidea) in the murid host: evidence for larval growth in striated muscle fibres.

Trichosomoides nasalis (Trichinelloidea) is a parasite of Arvicanthis niloticus (Muridae) in Senegal. Female worms that harbour dwarf males in their uteri, occur in the epithelium of the nasal mucosa. Young laboratory-bred A. niloticus were either fed females containing larvated eggs or intraperitoneally injected with motile first-stage larvae recovered from female uteri. Both resulted in successful infection. Organs examined during rodent necropsy were blood and lymphatic circulatory systems (heart, large vessels, lymphnodes), lungs, liver, kidneys, thoracic and abdominal cavities, thoracic and abdominal muscular walls, diaphragm, tongue, and nasal mucosa. Development to adult nasal stages took three weeks. Recovery of newly hatched larvae from the peritoneal fluid at four-eight hours after oral infection suggests a direct passage from the stomach or intestinal wall to the musculature. However, dissemination through the blood, as observed with Trichinella spiralis, cannot be excluded even though newly hatched larvae of T. nasalis are twice as thick (15 µm). Developing larvae were found in histological sections of the striated muscle of the abdominal and thoracic walls, and larvae in fourth moult were dissected from these sites. Adult females were found in the deep nasal mucosa where mating occurred prior to worms settling in the nasal epithelium. The present study shows a remarkable similarity between T. nasalis and Trichinella species regarding muscle tropism, but the development of T. nasalis is not arrested at the late first-larval stage and does not induce transformation of infected fibres into nurse cells. T. nasalis seems a potential model to study molecular relations between trichinelloid larvae and infected muscle fibres.

Chaunus ictericus (Spix, 1824) as paratenic host of the giant kidney worm Dioctophyme renale (Goeze, 1782) (Nematoda: Enoplida) in São Cristóvão district, Três Barras county, Santa Catarina state, Brazil.

Dioctophyme renale larvae have been found in cysts in the gastric wall of 5.17% (3/58) Chaunus ictericus specimens from São Cristóvão district, Três Barras municipality, Santa Catarina state, Brazil. However, larvae of this nematode were not found in sympatric Chaunus schneideri. The larvae caused a mild granulomatous reaction. This is the first report of paratenic hosts for D. renale in Brazil, and probably is also the first in the Neotropical region.

Parasite-induced fruit mimicry in a tropical canopy ant.

Some parasites modify characteristics of intermediate hosts to facilitate their consumption by subsequent hosts, but examples of parasite-mediated mimicry are rare. Here we report dramatic changes in the appearance and behavior of nematode-parasitized ants such that they resemble ripe fruits in the tropical rain forest canopy. Unlike healthy ants, which are completely black, infected ants have bright red, berry-like gasters full of parasite eggs. The infected gasters are held in a conspicuous elevated position as the ants are walking, and they are easily detached from living ants, which also exhibit reduced defensive responses. This combination of changes presumably makes the infected ants attractive to frugivorous birds, which ingest the red gasters and pass the parasite eggs in their feces. The feces are collected by ants and fed to the developing brood, thus completing the cycle. This is the first documentation of parasites causing apparent fruit mimicry in an animal host to complete their life cycle.