Molecular and morphological characterization of Pristionchus pacificus (Nematoda: Rhabditida: Neodiplogastridae), a new record of an entomophilic nematode from Iran

The Caenorhabditis elegans cuticle and precuticle: a model for studying dynamic apical extracellular matrices in vivo

Apical extracellular matrices (aECMs) coat the exposed surfaces of animal bodies to shape tissues, influence social interactions, and protect against pathogens and other environmental challenges. In the nematode Caenorhabditis elegans, collagenous cuticle and zona pellucida protein-rich precuticle aECMs alternately coat external epithelia across the molt cycle and play many important roles in the worm's development, behavior, and physiology. Both these types of aECMs contain many matrix proteins related to those in vertebrates, as well as some that are nematode-specific. Extensive differences observed among tissues and life stages demonstrate that aECMs are a major feature of epithelial cell identity. In addition to forming discrete layers, some cuticle components assemble into complex substructures such as ridges, furrows, and nanoscale pillars. The epidermis and cuticle are mechanically linked, allowing the epidermis to sense cuticle damage and induce protective innate immune and stress responses. The C. elegans model, with its optical transparency, facilitates the study of aECM cell biology and structure/function relationships and all the myriad ways by which aECM can influence an organism.

Multidimensional competition of nematodes affects plastic traits in a beetle ecosystem

Resource competition has driven the evolution of novel polyphenisms in numerous organisms, enhancing fitness in constantly changing environmental conditions. In natural communities, the myriad interactions among diverse species are difficult to disentangle, but the multidimensional microscopic environment of a decaying insect teeming with bacteria and fighting nematodes provides pliable systems to investigate. Necromenic nematodes of the family Diplogastridae live on beetles worldwide, innocuously waiting for their hosts’ deaths to feast on the blooming bacteria. Often, more than one worm species either affiliates with the insect or joins the microbial meal; thus, competition over limited food ensues, and phenotypic plasticity provides perks for species capable of employing polyphenisms. The recently established system of cockchafer Gymnogaster bupthalma and its occasional co-infestation of Pristionchus mayeri and Acrostichus spp. has revealed that these worms will simultaneously utilize two polyphenisms to thrive in a competitive environment. While both genera maintain plastic capacities in mouth form (strictly bacterial-feeding and omnivorous predation) and developmental pathway (direct and arrested development, dauer), P. mayeri employs both when faced with competition from Acrostichus. Here, we took advantage of the malleable system and added a third competitor, model nematode Pristionchus pacificus. Intriguingly, with a third competitor, P. mayeri is quicker to exit dauer and devour available food, while Acrostichus hides in dauer, waiting for the two Pristionchus species to leave the immediate environment before resuming development. Thus, experimental manipulation of short-lived ecosystems can be used to study the roles of polyphenisms in organismal interactions and their potential significance for evolution.

Molecular Identification and Phylogenetic Analysis of Heterakis dispar Isolated from Geese

Purpose

Heterakidosis is a common parasitic infection caused in domestic birds by Heterakis species: Heterakis gallinarum, H. isolonche, and H. dispar. Among them, the best described species is H. gallinarum, noted mainly in gallinaceous birds. In waterfowl, H. dispar is the predominant species. The variations in morphology and host specificity qualify H. dispar as a different species, but the phylogenetic relationships between heterakids were unclear for a long time, because of a lack of H. dispar sequences.

Methods

The authors provided the molecular data for H. dispar and analyzed the obtained sequences of the partial 18S rRNA gene and region ITS1-5.8SrRNA-ITS2 with the homological sequences.

Results

The 18S rRNA PCR product of H. dispar was about 800 bp, and the ITS-5.8S-ITS2 PCR product was about 920 bp, noticeably smaller size compared to H. gallinarum product. The BLAST analysis of H. dispar 18S sequence showed a 99% similarity with the sequences of Heterakis gallinarum and Ascaridia galli, 98% with A. nymphii, but only 94% with the sequence of Heterakis sp. Our ITS sequence of H. dispar was almost identical to the H. isolonche isolate, there is only one nucleotide of difference among the 943 sites analyzed. It also showed a lower similarity to the ITS sequences of H. gallinarum (88%), H. spumosa (87%), and H. dahomensis (87%).

Conclusions

In our phylogenetic analysis, it is the first attempt at the reconstruction of relationships within this superfamily Heterakoidea based on 18S rDNA and ITS region.