Medical Zoology 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 Medic...

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 Protists Zoologyand 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! Phylum Arthropoda 1,196,521 Common name Arthropods Extant species 1,196,521 82.34 % Mollusca Mollusks / 73,000 Chordata molluscs 5.02 Platyhelmin Chordates 61,035 thes Flat worms 4.20 Nematoda Round 30,000 2.06 Annelida Cnidaria worms Segmented 27,000 1.86 Extremely diverse: 82% of all known Porifera worms Echinodermat 20,000 Cnidarians 1.38 a Bryozoa Sponges Rotifera Echinoderms 13,300 0.92 animal species! All environments Nemertea Moss animals, sea Tardigrada mats Rotifers 9,300 0.64 7,300 0.50 (sea, freshwater, Gastrotricha Ribbon Brachiopoda worms 6,300 0.43 3,350 0.23 land, air) Xenacoelomo Water bears rpha Gastrotrichs 1,300 0.09 1,300 0.09 Every ecological Nematomorp ha Lamp shells Xenacoelomor 860 0.06 440 0.03... niche and very abundant, e.g.: Kinorhyncha phs Horsehair 400 0.03 Entoprocta worms Mud 365 0.03 Onychophora dragons Chaetognath Goblet worm 300 0.02 200 0.01 ~1021 copepod a Ctenophora Velvet worms Hemichordat Arrow worms 200 0.01 crustaceans in the oceans 130 0.01 a Dicyemida Comb jellies Acorn worms, 130 0.01 ~200 million insects for 130 0.01 (=Rhombozoa) Gnathostomulida pterobranchs Dicyemids 120 0.01 every 100 0.01 Loricifera Jaw 38 0.00 human being on Earth Priapula TOT worms 1,453,162 22 0.00 AL Phoronida Brush 15 0.00 Placozoa heads 100  Animal classification Exoskeleton shed periodically to allow growth Campbell et al. (2021) Biology,  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, 'claw- ticks, etc. bearers' Arthropoda Extin (or Euarthropoda = ct ‘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  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 Formicine ants have lost the stinger and the most toxic known spray formic venom among insects, 10× more potent than honeybee, acid into a wound caused by the comparable to cobra venom. mandibles. 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 Systemic reaction allergic to beecan reactions orbe wasp venoms, measured rarely using the Müeller grading system: ants. 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, Further reading: Helbling A. and Müller U.R. (2019) 43 - Allergic angina pectoris) 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 Bed bugs (Cimex allergy arises from the faecal material of lectularius) can cause house-dust mites (Dermatophagoides an allergic reaction or a pteronyssinus). severe skin reaction.  Insects inducing blisters and urtica Cause (itch)as a defence mechanism, even injury to humans though toxins aren’t inoculated through a sting Meloidae beetles – cantharidin Staphylinid beetles of the genus Paederus – (causes blistering of the skin - pederine (causes severe blistering and long- ‘blister beetles’) 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 The Guardian, Friday 29 wall. Not linked to hygiene, but rather high Sep 2023 population density. Come out to feed at night. Cause lesions and itch, 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  Flightless blood- suckers Fleas Belong to the insect order Siphonaptera,