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An Overview of Parasite Diversity
Published in Eric S. Loker, Bruce V. Hofkin, Parasitology, 2023
Eric S. Loker, Bruce V. Hofkin
A third major group of parasites slow to be resolved with more certainty with respect to their position in animal phylogeny is the Myxozoa. Myxozoans are an exclusively parasitic group of animals inhabiting either annelid worms or bryozoans as definitive hosts, and vertebrates, especially fish, as intermediate hosts. Some like Myxobolus cerebralis cause prominent fish diseases (Figure 2.22). Although once thought to be unicellular protists or a separate group of early diverging bilaterians, molecular study has clarified their status as unusual cnidarians, the phylum containing jellyfish and corals. This result nicely helps to explain the provocative similarity between cnidarian nematocysts and the polar capsules of myxozoan spores that had long puzzled zoologists (Figure 2.22). Myxozoans remain intriguing because at least one species, Henneguya salminicola, lacks a mitochondrial genome and functional aerobic metabolism, the first animal unequivocally shown to have this distinction. To go along with their anatomical simplification, myxozoans have among the smallest of genomes known from animals. As another striking and possibly related experiment in parasitism, the oocytes of sturgeons are often infected with a bizarre nematocyst-bearing cnidarian called Polypodium that even produces jellyfish-like forms in the freshwater stage of its life cycle.
The Discovery of the GSH Receptor in Hydra and Its Evolutionary Significance
Published in Christopher A. Shaw, Glutathione in the Nervous System, 2018
To understand how GSH acts in the hydra, one needs to know a little of the biology and natural history of the animal. A hydra is shaped like a two-ply hollow tube, about 8 by 1 mm when extended, made up of both outer (ectodermal) and inner (endodermal) epithelial layers. At the posterior end of the tube is a basal disk with which the hydra usually attaches to a surface, and at the anterior end is a mouth surrounded by a ring of tentacles (Fig. 1 A). The tentacles are armed with many nematocytes, one of the seven basic cell types of the hydra. The nematocytes contain nematocysts (stinging capsules), which start the feeding process by everting a coiled tube, which pierces and wounds the prey. The reduced glutathione (GSH) oozing out of the wounded prey initiates a specific feeding behavior in hydra.
Clinical Toxicology of Marine Coelenterate Injuries
Published in Jürg Meier, Julian White, Handbook of: Clinical Toxicology of Animal Venoms and Poisons, 2017
John Williamson, Joseph Burnett
Simultaneous discharge of thousands of nematocysts, some bearing a micro-dose of potent venom and each dose deposited into the prey (or human) where it can be rapidly absorbed (e.g. the human dermis), results in a very quickly rising blood level of venom, and the rapid onset of clinical effects33,36. In the case of serious human envenomation, massive nematocyst discharge may occur from entanglement in the tentacle material (Figure 8)36. Some of the nematocysts in every coelenterate species’ cnidom (nematocyst population) are not directly concerned with envenomation, but with grappling of the prey to the tentacle or body of the coelenterate, thus increasing the time and opportunity for the venom-bearing nematocysts to do their work32,33. (The systematic morphological classification of nematocysts has been addressed3.) Chirodropid envenomation is the most rapid envenomation process known; venom absorption may be further enhanced by the struggling of victims rendered incoherent by the immediate and savage pain26; such struggling and rubbing of the sting area and any adherent tentacle material will facilitate both further discharge of adherent, unfired nematocysts, and central venom movement from muscle contraction, hence the need in serious envenomations for both restraint of the victim’s movements by rescuers and the rapid inactivation of any unfired nematocysts on the skin1,38.
Metalloproteinases and NAD(P)H-dependent oxidoreductase within of Bay nettle (Chrysaora chesapeakei) venom
Published in Toxin Reviews, 2022
Mayra Pamela Becerra-Amezcua, Mónica Alejandra Rincón-Guevara, Irma Hernández-Calderas, Xochitl Guzmán-García, Isabel Guerrero-Legarreta, Humberto González-Márquez
Chrysaora chesapeakei jellyfish were collected in March 2014 from Mandinga Lagoon (Veracruz, Mexico). The jellyfishes were detected on the surface of the water and captured using long-handled beams with nets of 0.05 mm mesh. The collected animals were recognized as C. chesapeakei based on general morphological characters (bell diameter, lappets per octant, oral arm’s length, radial septa shape, subgenital ostium diameter, color, the number of rhopalia and tentacles per octant) and genetic identity by molecular biology as described Bayha et al. (2017). Nematocysts were separated from excised jellyfish tentacles immediately after collection and purified from tentacle debris (Bloom et al.2001) using a discontinuous gradient of Percoll as described by (Brinkman and Burnell 2008). Clean nematocysts of each type were counted with a Neubauer chamber.
Biofouling in marine aquaculture: a review of recent research and developments
Published in Biofouling, 2019
Jana Bannister, Michael Sievers, Flora Bush, Nina Bloecher
Net cleaning can also facilitate the spread of NIS by fracturing colonial species (Hopkins et al. 2011; Aldred and Clare 2014; Floerl et al. 2016) and triggering the simultaneous release of gametes, causing rapid recolonization (Carl et al. 2011; Floerl et al. 2016). Furthermore, the release of cleaning waste containing fragments of biofouling organisms and, potentially, particles of abraded copper coating, can severely impact fish health. Salmon farmers report agitated behaviour and reduced appetite during net cleaning and have observed gill and skin disorders afterwards. Upon contact, cnidarian biofoulers expel nematocysts that can penetrate fish skin and deliver poison (Helmholz et al. 2010; Cegolon et al. 2013), even after fragmentation following pressure-washing (Bloecher, Floerl, et al. 2018). For example, the hydroid Ectopleura larynx causes gill injuries in Atlantic salmon (Baxter et al. 2012; Bloecher, Powell, et al. 2018), and white-striped anemones Anthothoe albocincta are suspected to cause skin damage in Chinook salmon (Wybourne 2013). Management methods for other issues (eg parasitic sea lice) can further exacerbate these impacts. For example, lice skirts (Stien et al. 2018) can trap cleaning waste within cages, leading to greater interaction and risk of stinging by nematocysts.
Delayed deep dermal necrosis after jellyfish sting in a 4-year-old female infant
Published in Case Reports in Plastic Surgery and Hand Surgery, 2018
Diana Desax-Willer, Thomas Krebs, Samuel Christen
Jellyfish stings can result in a variety of symptoms, including pain, swelling, redness, and even severe systemic reactions. The tentacles of some jellyfish species contain undischarged nematocysts and incorporated toxins. Discharge is caused by an array of mechanical and chemical stimuli. It is postulated that immediate or delayed clinical signs are based on toxicological and immunological responses to components of jellyfish venoms and barbed tubules, including proteinaceous porins, neurotoxic peptides and bioactive peptides, collagens, and chitins [1–4].