Nematodes ultrastructure: complex systems and processes

Abstract

Nematode worms are among the most ubiquitous organisms on earth. They include free-living forms as well as parasites of plants, insects, humans and other animals. Recently, there has been an explosion of interest in nematode biology, including the area of nematode ultrastructure. Nematodes are round with a body cavity. They have one way guts with a mouth at one end and an anus at the other. They have a pseudocoelom that is lined on one side with mesoderm and on the other side with endoderm. It appears that the cuticle is a very complex and evolutionarily plastic feature with important functions involving protection, body movement and maintaining shape. They only have longitudinal muscles so; they seem to thrash back and forth. While nematodes have digestive, reproductive, nervous and excretory systems, they do not have discrete circulatory or respiratory systems. Nematodes use chemosensory and mechanosensory neurons embedded in the cuticle to orient and respond to a wide range of environmental stimuli. Adults are made up of roughly 1000 somatic cells and hundreds of those cells are typically associated with the reproductive systems. Nematodes ultrastructure seeks to provide studies which enable their use as models for diverse biological processes including; human diseases, immunity, host-parasitic interactions and the expression of phylogenomics. The latter has, however, not been brought into a single inclusive entity. Consequently, in the current review we tried to provide a comprehensive approach to the current knowledge available for nematodes ultrastructures.

Multiple origins of nematode-Wolbachiasymbiosis in supergroup F and convergent loss of bacterioferritin in filarialWolbachia

“…In the M. ozzardi sample (Moz2), the median coverage of contigs classified as Mansonella was observed to be 360X, while that of the Wolbachia contigs was found to be 13X. Assuming 1000 nematode cells per microfilaria 59 indicating that the lack of Wolbachia contigs is not due to insufficient depth of coverage and is rather most likely due to a very low titer of Wolbachia in this sample. Since both isolates were collected in Cameroon, these observations point to variation in Wolbachia titers within the same species in a geographical area and could explain the conflicting reports on detection of Wolbachia in M. perstans [25][26][27][31][32][33] .…”

Morphological adjustment in free-living Steinernema feltiae infective juveniles to increasing concentration of Nemafric-BL phytonematicide

“…The cuticle comprises a set of six layers [28], with the outermost thin layer of glycoproteins and lipids, with annuli and furrows [30]. Cucurbitacins are lipophilic and therefore, the cuticle is predisposed to cucurbitacin attack and damage [31]. Generally, cucurbitacins interfere with the integrity of cell membranes, which are further away in the innermost basal layer.…”

Scanning Electron Microscopic Study of the Anthelmintic Effects of Some Anthelmintic Drugs on Poultry Nematode, Ascaridia galli

“…It acts not only as a protective layer but also as the structural framework of the body (Maizels et al, 1993;Decraemer et al, 2003). Thus, it is in a truest sense a durable and anisometric exoskeleton that maintains the rigid contour of the body while allowing flexibility for movement (Basyoni and Rizk, 2016). It is highly resistant to most chemicals including the digestive enzymes of the host.…”