Arthropods and Their Life Cycles

Study Notes

Characterized by an exoskeleton, segmented bodies, and paired sets of legs.
Take in oxygen via holes in their outer covering.
Have a tube-like alimentary system running through their body.
Sensory hairs on their body detect changes in light, temperature, and movement.
Reproduction is typically sexual, with separate sexes and most species laying eggs.

Can be simple (incomplete metamorphosis) or complex (complete metamorphosis).
Simple life cycle: arthropod moults through nymphal stages while growing in size.
Complex life cycle involves distinct egg, larva, and pupa stages before becoming an adult.
Molting (ecdysis) is where arthropods periodically shed their exoskeleton while growing.

Include insects such as fleas and lice.
Adults have a distinct head, thorax, and abdomen, with jointed antennae on the head, complex mouthparts, and 3 pairs of jointed legs.
Also include arachnids such as ticks and mites.
Spider related.
Four pairs of legs, head and thorax fused, no antennae, no distinct mandibles

Small, dark brown, wingless insects with a laterally flattened body.
Possess a segmented body structure with a distinct head, thorax, and abdomen, equipped with complex mouthparts for blood feeding.
The third pair of legs is enlarged to jump up to 8 feet for host-to-host transmission.
Both sexes are blood feeders.
Only adults are parasitic.
Undergo complete metamorphosis.
Two main species are Ctenocephalides felis (cat flea) and Ctenocephalides canis (dog flea).
Not host specific but are host preferential.
Ctenocephalides felis is the most common flea found on cats and dogs, but its preferred host is cats.
Can survive on other carnivores and rabbits.

Mostly through indirect contact where immature stages mature in the environment and jump onto a host when hatched.
Can also be through direct contact with an infested animal but is less common.

Eggs laid on the host dry out and fall into the environment where they hatch into L1 larvae.
Larvae feed on flea dirt and undergo two moults to become L3 larvae and soon spin into a cocoon, entering the pupal stage.
The pupal stage varies in length as adult will emerge in correct conditions such as warm weather or when it perceives signs of a host.
Adult will then jump onto the host.

Mild Pruritis: Mainly in the dorsolumbar region on non-hypersensitive adult animals.
Anaemia and death: Occurs in kittens as fleas can consume large amounts of blood per day.
Flea Bite Dermatitis (FBD): An allergic reaction to flea saliva, causing severe pruritis and alopecia.

Fleas can be vectors for certain diseases such as feline infectious anaemia, feline leukemia, and Dipyldium caninum.
Also transmit zoonotic diseases.

Can be made through direct visualization of fleas and their faeces (dirt).
Coat brushing and the wet paper test can help identify flea dirt, which consists of digested blood.

Fleas can bite humans, causing localized irritation, but cannot complete their life cycle on human hosts.
They are vectors for zoonotic diseases, including plague (Yersinia pestis) and murine typhus (Rickettsia typhi).