Lecture 7 - Arthropods PDF

ZOOL10010 Medical Zoology Protists and invertebrates of medical importance A brief tour of protists and invertebrates that have a direct impact on human health, either as pathogens or disease vectors: Protists Worms: flatworms and roundworms Arthropods Mosquitoes and malaria ZOOL10010 Medi...

ZOOL10010 Medical Zoology Protists and invertebrates of medical importance A brief tour of protists and invertebrates that have a direct impact on human health, either as pathogens or disease vectors: Protists Worms: flatworms and roundworms Arthropods Mosquitoes and malaria ZOOL10010 Medical Zoology Protists and invertebrates of medical importance Lecture content: Introduction to Arthropoda Phobias Venoms and allergens Blistering and urticating arthropods Blood-sucking insects Arthropods as vectors of other organisms  The most species-rich animal phylum, by far! 'Wormy'? Phylum Common name Extant species % Arthropoda Arthropods 1,196,521 82.34 1,196,521 Mollusca Mollusks / molluscs 73,000 5.02 73,000 Chordata Chordates 61,035 4.20 61,035 x Platyhelminthes Flat worms 30,000 2.06 30,000 x Nematoda Round worms 27,000 1.86 27,000 x Annelida Segmented worms 20,000 1.38 20,000 Cnidaria Porifera Cnidarians Sponges 13,300 0.92 9,300 0.64 Extremely diverse: 82% of 13,300 9,300 Echinodermata Echinoderms 7,300 0.50 7,300 Bryozoa Moss animals, sea mats 6,300 0.43 all known animal species! 6,300 x Rotifera Rotifers 3,350 0.23 3,350 x Nemertea Ribbon worms 1,300 0.09 All environments (sea, 1,300 Tardigrada Water bears 1,300 0.09 1,300 x Gastrotricha Gastrotrichs 860 0.06 freshwater, land, air) 860 Brachiopoda Lamp shells 440 0.03 440 x Xenacoelomorpha Xenacoelomorphs 400 0.03 Every ecological niche 400 x Nematomorpha Horsehair worms 365 0.03 365 x Kinorhyncha Mud dragons 300 0.02 300 Entoprocta Onychophora Goblet worm Velvet worms 200 0.01 200 0.01... and very abundant, e.g.: 200 200 x Chaetognatha Arrow worms 130 0.01 130 Ctenophora Comb jellies 130 0.01 ~ 1021 copepod crustaceans in the 130 x Hemichordata Acorn worms, pterobranchs 130 0.01 130 x Dicyemida (=Rhombozoa) Dicyemids 120 0.01 oceans 120 x Gnathostomulida Jaw worms 100 0.01 100 x Loricifera Brush heads 38 0.00 ~ 200 million insects for every 38 x Priapula Priapulans 22 0.00 human being on Earth 22 Phoronida Horseshoe worms 15 0.00 15 Placozoa Placozoans 4 0.00 4 Cycliophora Symbion 2 0.00 2 x Micrognathozoa Micrognathozoans 1 0.00 1 TOTAL 1,453,162 100  Animal classification Exoskeleton shed periodically to allow growth (ecdysis) Campbell et al. (2021) Biology, 12th ed.  Phylum: Arthropoda Invertebrates with jointed/articulated legs (arthron ‘joint’ + pous, pod- ‘foot’) Triploblastic, bilaterally symmetrical, coelomate, protostome Exoskeleton shed periodically to allow growth (ecdysis; unites all Ecdysozoa) Body divided into discrete segments, groups of segments specialised as tagmata (head, thorax, etc.) Hard, rigid exoskeleton: constructed from chitin, reinforced with CaCO3 in Crustacea  Arthropoda classification incl. mites, ticks, etc. 'claw-bearers' Arthropoda Extinct (or Euarthropoda = ‘proper’ arthropods) ‘six legs’ incl. mosquitos, lice, flees, etc.  Arthropod nuisance and phobia High densities of particular species, e.g. ants, silverfish Filth-frequenting insects. e.g. cockroaches, bluebottles, blowflies, etc. Biters and stingers, e.g. ants, bees, wasps Phobia: an anxiety disorder, irrational fear or aversion entomophobia: to insects arachnophobia: to spiders …  Stinging insects - venoms Insects of the taxonomic order Hymenoptera include bees, wasps and ants. They can inflict a sting, usually in defence of the nest, sometimes for predation. Social insects co-operate to sting an intruder en masse – escalates the impact of an individual attack and deters even large vertebrates. The sting is a modified ovipositor (worker bees and wasps are sterile females) The honey-bee sting has backwardly directed barbs and cannot be retracted – it is single use only, and the bee dies when the sting and venom sac are ripped out Wasp and ant stings are unbarbed, can be retracted and are capable of repeated use A comprehensive guide to yellow stripey things  Stinging insects - venoms Hymenoptera venom constituents that contribute to the toxic effect include low molecular weight substances (such as biogenic amines, phospholipids, amino acids and carbohydrates, and peptides such as melittin, apamin or kinins). Harvester ants Pogonomyrmex spp. have the most toxic known venom Formicine ants have lost the stinger and spray formic among insects, 10× more potent acid into a wound caused by the mandibles. than honeybee, comparable to cobra venom. Normal local reaction to a Hymenoptera sting consists of a painful, sometimes itchy, local wheal and flare reaction, followed by a swelling of up to 5–10 cm in diameter. Symptoms usually resolve within a few hours. Systemic toxic reaction may occur after multiple stings; 200-1,000 stings may be lethal in adults, 50 may be lethal in children.  Stinging insects - allergens Hymenopteran allergens (mostly glycoproteins) are one of the most important causes of allergic and anaphylactic reactions. Usually in reaction to bee or wasp venoms, rarely ants. Systemic allergic reactions can be measured using the Müeller grading system: Grade I. skin (generalised urticaria, itching, erythema) anxiety Grade II: as above + gastrointestinal (stomach pain, nausea, vomiting) generalised oedema Grade III: as above + respiratory (dyspnea, difficulty swallowing, hoarseness, stridor) Grade IV: as above + cardiovascular (cyanosis, collapse, arrhythmias, angina pectoris) Further reading: Helbling A. and Müller U.R. (2019) 43 - Allergic Reactions to Stinging and Biting Insects. In: Clinical Immunology, 5th edition. (eds: Rich R.R. et al.), pp: 601- 610.e1. Elsevier. https://doi.org/10.1016/B978-0-7020-6896-6.00043-0  Allergic disease Exposure to an arthropod allergen (usually a low molecular weight protein) can trigger excessive immunological reactions. Common in people with occupational exposure to insects, particularly mealworms (Tenebrio larvae), bloodworms (Chironomid larvae), locusts and blowflies. Venomous and urticating insects cause the greatest danger when sensitized (previously exposed and allergy-sensitive) individuals are affected again, with the possibility of anaphylactic shock and death. The most significant arthropod-mediated allergy Bed bugs (Cimex lectularius) arises from the faecal material of house-dust mites can cause an allergic reaction (Dermatophagoides pteronyssinus). or a severe skin reaction.  Insects inducing blisters and urtica (itch) Cause injury to humans as a defence mechanism, even though toxins aren’t inoculated through a sting Meloidae beetles – cantharidin Staphylinid beetles of the genus Paederus – pederine (causes (causes blistering of the skin - ‘blister beetles’) severe blistering and long-term ulceration; produced by endosymbiotic bacteria) Lepidopteran caterpillars are a frequent cause of skin irritation or urtication – hollow spines or setae containing toxins which are released on contact or by breaking the hairs Invasive species: Oak processionary moth (Thaumetopoea processionea) Hair present on the larger larvae contain an urticating defensive toxin, thaumetopoein. Larvae can cause skin and eye irritations, rashes, sore throats and breathing difficulties Infestation of harmful caterpillars found in oak trees at Dublin housing estate The Irish Times, Monday 12 June 2023  Flightless blood-suckers Cimex lectularius and C. hemipterus – bed bugs Belong to the insect order Hemiptera, 1-7 mm in size. Spend much of their time in dark, hidden locations like mattress seams, or cracks in a wall. Not linked to hygiene, but rather high population density. Come out to feed at night. Cause lesions and itch, The Guardian, Friday 29 Sep 2023 secondary infection may result from scratching. Can go without feeding for 100s of days, so difficult to get rid of. “France’s growing bedbug crisis has sparked a political row as Paris city hall said the invasion of bloodsucking insects must be tackled before next year’s Olympic Games and the transport minister summoned train and bus operators to prevent the bugs multiplying on seats.”  Flightless blood-suckers Fleas Belong to the insect order Siphonaptera,