An Overview of Parasite Diversity
Eric S. Loker, Bruce V. Hofkin in Parasitology, 2023
Figure 2.18 reveals that much of the uncertainty with respect to quantifying the number of eukaryotic species in general, and of animal parasites in particular, lies within the vast phylum Arthropoda. The phylum is dominated by insects of which there are an estimated 900 thousand named species. However, there are many more insect species to be described and we do not know if this number will prove to be in the millions or thousands of new species. The variety of parasitic lifestyles among the insects alone is immense (Figure 2.20), including organisms as diverse as gall-making parasites of plants, hundreds of thousands of wasp species that are parasitoids undergoing their larval development in other insects and invertebrates, ectoparasites such as fleas and lice, and additional blood-feeding insects such as mosquitoes, black flies and kissing bugs that also are frequently implicated in the transmission of viruses or other disease-causing organisms.
Comparative Immunology
Julius P. Kreier in Infection, Resistance, and Immunity, 2022
If insects are injected with heat-killed bacteria, proteins appear in their hemolymph that can prevent bacterial growth or cause bacterial lysis. For example, following infection of tomato hornworms, their hemocytes and hemolymph plasma enzymes degrade bacterial cell walls releasing peptidogiyeans. These peptidoglycans in turn elicit increased synthesis of antibacterial proteins which accumulate in the hemolymph. In some insects toxins induce proteins that mimic antibody molecules. Among the proteins induced in this way is lysozyme. These antibacterial proteins appear about two hours after exposure to the bacteria and reach peak levels at twenty-four hours. In some insects, the activity is short-lived and disappears by four days; in others, it may last for several months. Passive immunity can be conferred on recipient insects by transfer of hemolymph from immune insects. Little is known about the mechanisms involved in the production of these antibacterial proteins.
Lice
Jerome Goddard in Public Health Entomology, 2022
Bloodsucking lice are parasites of humans and many other mammals and birds worldwide, and certain species are significant vectors of disease agents. Human body lice and head lice are almost identical in appearance; however, body lice are usually about 15–20% larger than head lice. They are tiny (2–4 mm long), elongate, soft-bodied, light-colored, wingless insects that are dorsoventrally flattened, with an angular ovoid head and a nine-segmented abdomen (Figure 12.1). The eggs are small (about 1 mm), oval, white or cream-colored objects with a distinct cap on one end. Eggs are attached to clothing in the case of body lice and to hairs in the case of head and pubic lice (Figure 12.2). The head bears a pair of simple lateral eyes and a pair of short five-segmented antennae. Pubic lice are dark gray to brown in color and are called crab lice because of their crablike shape (Figure 12.3). They are distinctly flattened, oval, and much wider than body or head lice. As with head and body lice, the head bears a pair of simple lateral eyes and a pair of short five-segmented antennae. They are 1.5–2.0 mm long; their second and third legs are enlarged and contain a modified claw with a thumblike projection, which aids them in grasping hair shafts.
Sub-lethal effects of thiamethoxam on Apis mellifera Linnaeus
Published in Toxin Reviews, 2022
Amit Choudhary, Bharathi Mohindru, Ashok Kumar Karedla, Jaspal Singh, Pardeep K. Chhuneja
Insect pollinators have a mutualistic relationship with plants. At the same time, there are many insects that have a parasitic relationship. Plant protection chemicals, especially synthetic pesticides, do play a key role in keeping these pests under check and ensuring food security. The discovery of insecticidal properties of DDT in 1939, a contact organochlorine compound acting on Na+ ion channel in the insect nervous system, opened new vistas of crop protection. Neonicotinoids, developed by taking nithiazine as the lead structure, are comparatively a newer generation of insecticides discovered at the end of the 20th century. These insecticides derived their name due to their structural similarity with nicotine. These are specific for insects because they act on nicotinic acetylcholine receptors which are present in the insect nervous system. The absence of desired receptor sites coupled with a fast depletion rate from tissues (half-life 2–6 h) makes these chemicals safe for mammals. The median lethal dose (LD50) oral for rat = 1563 mg/kg body weight (FAO 2021) in comparison to generic insecticide DDT—113–800 mg/kg body weight (NPIC 2021).
Insight into the evolutionary profile of radio-resistance among insects having intrinsically evolved defence against radiation toxicity
Published in International Journal of Radiation Biology, 2022
Jagdish Gopal Paithankar, Tanhaji Sandu Ghodke, Rajashekhar K. Patil
Insects are one of the most successful life forms throughout the history of terrestrial life on our planet. This has been supported by several observations, such as species diversity among insects, an ecological impact of insect populations, their distribution throughout the planet and their existence since beginning of the terrestrial life until today (Bradley et al. 2009). There are many factors, which are responsible for the evolution of the insects and making them a successful life form. Insects show numerous physiological and metabolic adaptations. Some insects have evolved with specialized physiological mechanisms to detoxify potent toxins and some can withstand against toxicants (Denlinger and Lee 2010). Some of the insects reported to thrive in extreme environmental conditions of cold and heat. Two species of Chironomidae family found at Antarctica are the southernmost living insects known currently (Oliver 1971). Chironomids are reported to thrive in radioactively contaminated areas of accident sites in Chernobyl, Ukraine (Williams et al. 2001), this environmental adaptation enhanced radio-resistance of these insects. Some species of chironomidae are reported to accumulate uranium in their body and these species are thriving in uranium-contaminated areas (Dias et al. 2008).
Advances in venom peptide drug discovery: where are we at and where are we heading?
Published in Expert Opinion on Drug Discovery, 2021
Taylor B. Smallwood, Richard J. Clark
Many venom-derived peptides have been discovered from a range of venomous animals for potential therapeutic treatments of human diseases. Yet, despite several venom-derived peptides approved for market, the full potential of venom as a therapeutic is still at its infancy. While FDA-approved venom-derived drugs has seen great success, there has not been a novel FDA-approved venom-derived drug since exenatide in 2005. However, the improvement in technology over the past decade will likely see the pipeline of discovery for venom-derived peptides expand in future years. In particular, toxin driven discovery techniques will allow for the identification of bioactive peptides from even the smallest venomous animals that have for years remained untapped. Among these, insects represent a diverse group of organisms that until recently have not been extensively explored. For example, ants have developed and evolved venom to hunt their prey and to defend their nest against predators, competitors and microbial pathogens. Ant venom is found to be more complex and heterogenous than initially thought. Although the extent of their venom remains largely unexplored, recent transcriptomic and proteomic studies reveal ant venoms to contain mixtures of many bioactive molecules including short linear peptides (<5 kDa) and complex peptides with disulfide bonds [101]. Some of these peptides have been shown to be antimicrobial but are also believed to possess paralytic, cytolytic, hemolytic and/or insecticidal properties [102].