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
