Arthropods Intro Flashcards
Arthropod
Invertebrate Hard chitinous exoskel (to support them) Segmented body Jointed limbs Air breathing Grow by ecdysis (moult through diff stages)
Insecta
3 pairs of legs in adults
Distinct abdomen thirax and head
Single pair of antennae in adults
Lifecycle has partial or complete metamorphosis
Arachnida
4 pairs of legs in nymphs and adults (3 in larvae)
Mouthparts and a fused cephalothorax and abdomen (not as obvious segmentation)
No antennae
Insecta Partial metamorphosis
Juvenile (nymph) stage broadly resembles adults
New cuticle is made and the ild one is shed in 4/5 intervals throughout dev
Size incr at each stage
Insecta Partial metamorphosis eg human head louse
Adult females attach eggs to hairs Nymphs hatch from eggs Nymphs moult 3 times before becoming sexual mature adults Sexual repro in adults Life cycle complete in 2 wks
Insecta Complete metamorphosis
Juvenile (larvae/maggot/grub) dissimilar to adult
Juvenile adapted for feeding and growth
Adults adapted for repro and dispersal
There is substantial reorganisation and reconstruction of the entire body during metamorphosis within the pupa stage
Insecta Complete metamorphosis eg cat flea
Females lay eggs continuosly which fall to the ground containing a blood drop
Larvae feed on part digested blood in adult faeces
Transition from lava to pupa to adult is complete metamorphosis
Adults of both sexes remain on host permanently and repeatedly feed
Insecta Complete metamorphosis eg house fly
Eggs laid into enviro eg in rotting dung or organic material
Go through 3 larval stages feeding on rotting organic material
Larvae pupate in the same enviro
Adults are parasitic with sponging mouthparts
Arachnida life cycle (all partial metamorphosis)
4 basic stages: Egg 6 legged larva 8 legged nymph 8 legged adult Moult between stages and parasite gets bigger with each stage
Arachnida partial metamorphosis eg 3 host tick
Adult females drop to the ground and lay eggs (usually moist humid undergrowth) Larva hatch and feed on a host (1yr) Drop off and moult to nymphs Nymphs feed on a host (1yr) Drop off and moult to adults Adults feed and mate on a host (1yr) Males die and females lay eggs then die 3 host 3 yr
Arthropod repro strategies
Life cycles and repro strategies enable them to take advantage of favourable conditions leading to rapid pop expansion (not all arthropods but most)
Can survive during adverse conditions as a moulting, pupating or pharate (adult waiting to emerge) stage
Arthropod struct and biology
Chitinous exoskel protects from dessication pathogens and predators
Most are ecto parasites
Some are endo
Most mites are succept to dessication hence adapted to be permanently parasitic as permanently protected
Ticks can survive dessication off their hists in a suitable habitat eg dense vegetation mass, hence they are temporarily parasitic
Permanent parasite eg keds
Females prod larvae that adhere to the wool and pupate immediately and emerge after 3wk as adults
Small wingless flies with flattened bodies (allow to live between wool fibres) strong legs and claws (allow to grip host and move)
Temporary parasite eg dermanyssus (poultry red mite)
Lay eggs on feathers or in enviro
Hatch into larvae that dont feed on blood
Nymphs and adults feed on blood at night by ‘attacking’ birds
Most time is spent in dark cracks or crevices
Parasitic as developing stages but not adults eg harvest mite
Eggs hatch in enviro and find a host
6 legged larvae feed on blood for several days then drop to the ground
Mature into free living nymphs and adults
Adults lay eggs
Parasitic as developing stages but not adults eg myiasis (blow flies) flies
Eggs laid on skin surf of live animal or carrion or rotting organic material
3 larval stages feed on libing subcut tissue
3rd stage larvae pupate and drop onto the ground
Adults arent adapted for parasitism
Insect larvae feeding (spec fly)
Voracious feeders to provide enough food for adults to survive until first feed or repro as some adults eg warble fly dont feed
Some larvae are parasitic and adults arent
Arachnid larvae feeding
Most mites and all ticks are parasitic at all stages
Arachnid chewing mouthparts
Adapted to chew skin scales and hair
Strong mandibles act like jaws
Eg chewing lice
Arachnid tearing mouthparts
Adapted to tear host tissue
Large strong curved hooks
Eg myiasis fly larvae
Arachnid cutting and slashing mouthparts
Adapted to blood feed
Eg midges and tabanids (horse fly/cleg)
Arachnid sucking mouthparts
Hypodermic tube
Eg mosquitoes, stable flies, sucking lice
Sponging mouthparts
Act like sponge for secr at mucous mem or blood
Eg house flies
Clegs
Head, face and horn flies
Mite and tick blood feeding mouthparts
Jaw loke chelicerae incise epidermis
Hypostone for blood feeding through which digestive enz and anaesthetic substances are secr and blood is ingested
Has backwards pointing barbs to enable it to stay in the skin
Together form a stout barbed tube
Temporary parasite adaptations
Find hosts using: wings, antennae, eyes, powerful legs
Feed rapidly, adhere strongly or secrete anaesthetic substances to avoid removal
Permanent parasite adaptations
Remain on the host using hooks, combs, body scales
Body shapes spec to their niche
Mechanical transmission
No involvement of pathogen with life cycle of the parasite vector or development within the vector
Eg summer mastitis
New forest eye
Tick pyaemia
Biological transmission
Pathogen must survive within the transmitter and move from guts to mouthparts before transmission
Survival and replication within vector important part of patjogen lifecycle
Eg bluetongue, west nile virus, african horse sickness
Bio transmission eg west nile virus
Mosquitoes infected by feeding from wild birds (reservoir host)
Rapid biral multiplication in the birds as it is the amplification host
Transmission by one female mosquito during feeds for repeated egg laying
Men and horses are dead end hosts - slow viral replication
