Defensive Strategies 2024 Lecture 1 PDF

DEFENSIVE STRATEGIES-1 2024 (Dr Tom Kelly) Dr Neil Coughlan  DEFENSIVE STRATEGIES-1 Primary principle: Animals, plants – even bacteria, must defend themselves in order to complete their lives and produce young. Biodiversity and Communities Chapter 54 - Concept 54.1 (Campbe...

DEFENSIVE STRATEGIES-1 2024 (Dr Tom Kelly) Dr Neil Coughlan  DEFENSIVE STRATEGIES-1 Primary principle: Animals, plants – even bacteria, must defend themselves in order to complete their lives and produce young. Biodiversity and Communities Chapter 54 - Concept 54.1 (Campbell 12th Edition) Gaboon Viper Bitis japonica Camouflage Highly venomous bite These Lectures Basic defences of plants and animals Poisons and venoms Mimicry Camouflage Immune defences – The Immune System (enormously complex) Innate immunity; External Defences The Adaptive Immune Response Epidemiology, R0, Herd Immunity, Novel Pathogen OUTLINE OF ISSUES Evolutionary context Meaning of Biological Fitness (relative ability of an individual to survive and reproduce within a population) Survival emphasised by Darwin Reproductive output equally –if not more important- Neo-darwinism or “Modern Synthesis” – 1930 onwards “Necessity” of getting genes into the next generation; Lifetime Reproductive Success = LRS  Animals, Plants – even Bacteria have to defence themselves against attack from predators, herbivores and parasites (pathogens) Parasite is an organism that lives on or in another organism of another species...for at least part of its life cycle. Pathogen is an organism that causes diseases to the host after infection. Defence can be physical, chemical, behavioural and be based on highly complicated cellular and soluble factor responses These lectures summarise in outline some of these strategies Clutch size (Photo Richard Duff) Lifetime Reproductive Success = LRS Marked bird: count eggs, track eggs to juvenile to adult. PREDATORS AND PARASITES ARE A MAJOR INFLUENCE ON LRS AND FITNESS Lifetime Reproductive Success = LRS Marked bird: count eggs, track eggs to juvenile to adult. Impact of predators/parasites CREDIT – istockphoto.com Parasites and Predators Parasites much smaller than their Predators much larger than their prey hosts Life expectancy much greater than Life expectancy much shorter than most prey their hosts Attack many different prey in their Infect one or a few hosts in their life life time time Always kill their prey Rarely kill the host Insect predators of other insects aka Parasites = Micro and Macro forms ‘Parasitoids’ always kill their ‘hosts’ Definitions – in part -based on or prey immune response Pine martin photo Richard Duff  MOSQUITO Malaria parasite - Protozoa RED BLOOD CELLS Aedes aegypti Vector of numerous diseases e.g. Yellow Fever Intermittent ectoparasites, Proboscis Transmit Malaria - malaria parasite, kills 0.5M people/yr MICRO-PATHOGENS aka MICRO-PARASITES Very small in size Can cause severe morbidity and mass mortalities Replicate very quickly >6.5 M people re Covid-19 And undergo direct replication in the host HIV: 40M; Spanish Flu (1918): 40-50M. Are easily transmitted directly Adaptive immune response is robust and long lasting Viruses, bacteria and protozoa (single celled eukaryote organisms: e.g. malaria)  VIRUSES FROM COOPER (1995) Viruses and the Environment. “Bad news in a protein envelope” Peter Medawar Influenza virus taxonomy and Virus Naming System: antigenic variation https://www.youtube.com/watch?v=nVbgByJNLOo&ab_chann el=khanacademymedicine 18 different HA subtypes and 11 different NA subtypes. MACROPARASITES GENERALLY DO NOT CAUSE SEVERE LARGE AND MACROSCOPIC IN SIZE MORBIDITY TO THE HOST AND MASS DO NOT REPRODUCE QUICKLY MORTALITIES ARE RARE GENERALLY DO NOT REPLICATE MORBIDITY RELATED TO BURDEN I.E. DIRECTLY IN HOST NUMBER OF PARASITES CARRIED BY HOST (dose dependent) NOT TRANSMITTED DIRECTLY IMMUNE RESPONSE IS WEAK AND COMPLEX LIFE CYCLES OFTEN WITH SHORT LIVED AT LEAST TWO INTERMEDIATE HOSTS WORMS, TICKS, LICE MOSQUITOES, FLEAS, TAPEWORMS ROUNDWORMS AND FLUKES  TICKS LYME Disease H5N1 nematode micrograph RABIES VIRUS Roundworm Tapeworm Points to note: Both attack and defence can be expensive in terms of energy allocation As will be shown some defences can be used in attack and vice versa But the ‘benefits’ must outweigh the ‘costs’ Both plants and animals have ‘invested’ in defences Defences can be both physical and ‘chemical’ (and cellular). Basic defences-1 (Bacteria) Even bacteria have ‘immune’ defences Recently discovered CRISPR-Cas9 Clustered regularly inter-spaced short palindromic repeats Cas9, an enzyme which acts by snipping out part of the invading viral Nucleic acid Acts against Phages i.e. viruses invading bacteria Basic Defences-1 (Animals and Plants) Structural – spines, thorns, trichomes, modified skin (Thickening); Horn, spurs etc. e.g. Hedgehog, Porcupine, Spiny Anteater = Echnida Skunk (Foul smell) Fulmar petrel (Foul, oily projectile regurgitate) Salamander (Poison)  Long Thorn Kiawe Euphorbia milii Blackberry Rubus fruticosus Acacia  Hedgehog African Buffalo Syncerus caffer Porcupine Echnida – Indian Pangolin Manis craccicaudata also has poison gland Rhinoceros Diceros bicornis Skunk Fulmar Petrel PLANT DEFENCES Plants are immobile - attacked by herbivores Most are insects and the interaction dominates the terrestrial ecology of Earth Above ground and below ground attack Defences – broadly two kinds – CONSTITUTIVE and INDUCTIVE Plant Defences Constitutive = preformed, permanently present {physical and chemical} Inductive = Induced by attack Volatile Organic Compounds (VOC) +BVOC Primarily chemical Very complex Allelopathic Secondary metabolite - based But insects also attracted – e.g., pollinators So conflicting ‘signals’ from plant Constitutive compounds Include well known alkaloids: Curare Atropine Cocaine Strychnine Nicotene All have negative effect on insect grazers Many other compounds have a similar effect All important in insect herbivore population dynamics Inductive compounds VOC = Volatile organic compounds BVOC = Biogenic VOC’s HIPV = Herbivore Induced Plant Volatiles Biogenic Allelopathic = Chemicals released by one organism that affects growth and reproduction (positive or negative) in another organism Secondary metabolites (not part of maintenance, growth or reproduction) Summon natural enemies of insect herbivores Exert effect on nearby plants Controversial topic  Parasitoid wasp –summoned by plant - released volatiles in response to attack of caterpillar Ichneumon wasps Bullhorn Acacia Vachellia cornigera (Mexico) Ant symbiont (Pseudomyrmex ferruginea) of Bullhorn Acacia (mutualism) POISONS Compounds that either are a) produced or b) sequestered by animals (consumed and stored) Cane Toad Rhinella marinus (introduced to Australia) Bufotoxin from gland near eye Poisonous to predators Poisons have to consumed or – more rarely – sprayed or squirted on to exposed skin, eyes etc.) Amphibian skin, Fugu or Puffer fish – extremely toxic This newt hosts a distinct colony of bacteria that produce the poison *Science 1st May 2020. Tetrododoxin produced in the skin microbiome Elife9.e53898 (2020) Rough- Skinned Newt VENOMS A venom is a toxic substance introduced by a bite i.e. resulting in mechanical damage e.g. snake fangs, Spider Bite, Bee or Wasp sting; Tick Bite; Cone Shell Result is often fatal Sometimes exclusively defensive – bees and wasps Or both defensive and offensive (i.e. in the capture of prey) e.g. Snakes Convergent evolution in chemical structure and toxic action Cobra – Elapid - Neurotoxic Pit Viper – Viperidae - Haemotoxic Brown Recluse Spider American Dog Tick – PARALYSIS Severe tissue damage MULGA or KING BROWN SNAKE (Pseudechis australis) – Most venomous of all? Underestimated, no antivenom for some snake species. Australia  Black mamba Dendroapsis polylepis Sea Snake –highly venomous Sub Saharan Africa : Very aggressive – will ‘bite’ repeatedly Rattlesnake Snake Venoms Only 300 of 2000 snake Venoms primarily attack but also species are venomous ( mild defence (Rattle snake) venoms in others) 95% of dry weight is Protein - At least 1,000,000 snake polypeptide (so, proteins and bites per year? At least peptides) 100,000 fatal Long and short chain Venomous families are : Some species have both Colubridae (Boomslang); Elapidae; Cobra, Mamba, Non venomous bites as well; but Taipan, Coral Snake; fatal bites may not show ill effects Hydrophidae (Sea Snakes); for 10+hours Viperidae (Puff Adders) Neuro-toxic and haemorrhagic Crotalidae: Pit Vipers (but also cytotoxic and myotoxic). Synapse: neuronal junction Right back to the earliest stages of evolution SNAKE BITE MORTALITY The World Health Organization says snakebites are a neglected issue that needs more attention and investment. Each year, an estimated five million people worldwide are bitten by snakes, out of whom 100,000 die and 400,000 are permanently disabled or disfigured. In Sub-Saharan Africa alone, 30,000 people die from snakebite every year and an estimated 8,000 undergo amputations - BBC  FROM the BBC SNAKEBITE ANTIDOTE IS RUNNING OUT The world is running out of one of the most effective snakebite treatments, putting tens of thousands of lives at risk, warn experts. https://www.bbc.com/news/health-34176581 Medicines Sans Frontiers says new stocks of Fav-Afrique, which neutralises 10 different snakebites that can occur in Sub-Saharan Africa, are desperately needed. The last batch will expire in June 2016 and there is no comparable replacement. Manufacturer Sanofi Pasteur says it has been priced out of the market. Alternatives are available but MSF says they are not as good. Fav-Afrique is the only anti-venom that has been proven safe and effective to treat envenoming from different types of snakes across Sub-Saharan Africa, it says.  Sequestration of toxins Cinnabar moth (Tyria Aposematic jacobaeae) Colouration Aposematic Colouration Aposematism Warning Colouration Usually yellow and Red Yellow and Black Orange and Red Yellow and Red Blue or green with black stripes (females of some snakes may not be aposematic –but still venomous) Indicates unpalatability Universal code ensuring protection of ‘owners’ Used by humans on safety and security vehicles etc. Mimicry Believed to be of two basic kinds: 1) Mullerian Mimicry = Imitative similarity – typically based on warning colouration – amongst a number of mimic species all of which are unpalatable or otherwise offensive to a predator. 2) Batesian: Close resemblance of palatable i.e. harmless species (the mimic) to an unpalatable or poisonous/venomous species (the model) to deceive the predator (Operator) Lincoln et al.(1998) A Dictionary of Ecology, Evolution and Systematics MIMICRY Complex and controversial subject Some overlap between Mullerian and Batesian Mimicry But overall mimicry is an important evolutionary strategy Both forms confer adaptive advantage Sometimes difficult to see the advantage and to separate from camouflage Mullerian Mimicry Honest signal Viceroy Monarch Heliconius butterflys All unpalatable  BATESIAN MIMICRY Dishonest signal Honest signal ? Batesian mimicry in coral snakes and similar form: (left) the venomous Eastern coral snake Micrurus fulvius; (right) the harmless king snake Lampropeltis polyzone; and (bottom MULLERIAN?) the moderately venomous rear-fanged false coral snake (Oxyrhopus). Credit: Painting by C. Olsen BATESIAN -examples Dishonest signal Hover Fly harmless non-stinging Bee - Stinging  BATESIAN MIMIC Moth HORNET Mimic  ANT MIMICS Beetle Ant Mimic ANT ANT SPIDER ANT MIMIC Access to prey  All Batesian mimics –most are hover flies Diptera Syrphidae Camouflage and Crypsis Widely seen in nature Both defensive – i.e. remains undetectable to predators And offensive – prey does not detect presence of predator until it is too late Some overlap with Batesian mimicry but also with mimicry in general Peppered Moth Biston bitularia-Famous controversy INDUSTRIAL MELANISM Camouflage, also called cryptic coloration, is a defense mechanism or tactic that organisms use to disguise their appearance, usually to blend in with their surroundings. Organisms use camouflage to mask their location, identity, and movement  Crab Spiders Gaboon Viper – Venomous Summary-1 Arms Race Poisons – Consumed Different strategies Venoms by way of bite Plants –Constitutive (e.g. Snakes cause alkaloids and Inductive e.g. haemorrhaging and/or Terpenes) paralysis Volatile compounds Ticks – Paralysis Parasitoids VIP to counteract Spiders – tissue damage herbivore insects Some hypersensitive