arthropods as vectors & parasites Flashcards
1
Q
morphological characteristics of arthropods
A
- jointed appendages
- segmented body
- external skeleton
- open circulation
- nervous system
- bilateral symmetry
2
Q
metamerism
A
- = having a segmented body
- serial repetition of homologous organs in each segment that function in coordination with the others
- in arthropods, fusion of adjacent metameres forming larger functional units
- tagma
3
Q
tagma
A
- each responsible for performing a specialised task
- head - sensory perception, neural integration, food gathering
- thorax - locomotion
- abdomen - housing of visceral organs
- digestion, excretion, reproduction
4
Q
jointed appendages
A
- allow them to inhabit any space
- limbs - walking
- wings - flying
- antenna - sensory perception
- mouthparts - food gathering
- muscles allow their attachment to skeleton so that limbs can move
5
Q
antennae
A
- olfactory receptors and mechanosensory receptors
- covered in sensilla
6
Q
sensilla
A
- hold receptors and neurons
- complex structures allowing for sensitivity
- free-floating molecules bind receptors
- AP fired down to antennal lobe in brain
7
Q
mouthparts
A
- define food source
- labrum = upper lip
- mandibles - biting, chewing, severing food
- maxillae
- paired structures for tasting/manipulating food
- labium - lower lip, pair of segmented palps
8
Q
male vs female mouthparts
A
- very different
- females have a sting
- for feeding on animals
- egg production
- males have a brush
9
Q
chelicerata
A
- e.g. ticks
- no antenna
- sensilla on pedipalps
- sit between mouth and legs
- use chelicerae mouth part structure to pierce host skin and open it up
- acts like hook
- allows attachment to host for a long time
10
Q
exoskeleton
A
- thin waxy lipoprotein layer
- impermeable to water
- prevents water loss
- procuticle
- polysaccharide chitin and cross-linked proteins
- sclerotization
- much more protective than endoskeleton
- better leverage because muscles attach better
11
Q
metamorphosis
A
- most species have distinct life cycle stages that can be structurally distinguished from the adult
- larva must undergo metamorphosis before becoming an adult
- some species have similar-looking stages = incomplete metamorphosis
12
Q
open circulatory system
A
- no closed blood vessels
- haemolymph
- flushes over organs via sinuses
- moved through chambers by muscle contractions
- pumped through ostia (valve openings) to heart and back
- no oxygen transport → no haemoglobin
- deliver nutrients to organs
- collection of excretory waste
- transport to malphigian tubules for excretion
13
Q
respiratory systems
A
- vary between groups depending on habitat
- crustaceans → underwater → feathery gills
- chelicerata → underwater/land → book lungs or book gills
- series of plates with thin respiratory epithelium
- hexapoda, miriapoda, some chelicerata
- trachea system
- branched tubules → air diffuses into body
- limits size
14
Q
digestive system
A
- entry point for parasites
- ingestion in bloodmeal
- entry through midgut epithelium
- multiplication in other structures
- foregut, midgut, hindgut
- salivary gland compounds prevent coagulation during blood feeding
15
Q
Malphigian tubules
A
- filter haemolymph
- removes compounds to be excreted
- filtrate secreted into hindgut for ion reabsorption
- then into intestine
16
Q
nervous system
A
- segmented nerve cord
- ganglia across whole body
- ventral nerve cord
- 3 ganglia fuse at head
- different receptors all over body
- e.g. auditory - legs and antenna
- well adapted to perceiving environment
17
Q
compound eyes
A
- majority of insects and crustaceans
- many independent optical units (ommatidia)
- each ommatidia has a lens and photoreceptor apparatus
- limited resolution as pixels from each ommatidia overlap
18
Q
simple eyes
A
- camera-like eye with no lens but a cornea
- high resolution
- can’t see all around with one eye
- multiple eyes
- arachnids
19
Q
photoreceptors
A
- up to 16 types in arthropods
- 3 in humans
- can perceive UV light
20
Q
arthropod parasites
A
- ectoparasites
- ticks, fleas, mites
- endoparasites
- chigoe flea, myiasis
- mechanical pain associated with alrval invasion and establishment in tissues
- intermediate host and vectors of other parasitic microorganisms
- e.g. malaria
21
Q
disease transmission by arthropods
A
- mechanical
- causative agent lodged in arthropod vector without altering development or mutliplication
- e.g. in mouthparts
- myiasis by house fly
- biological
- certain stages in life cycle of parasite takes place in body of arthropod
22
Q
biological transmission
A
- propagative
- multiplication of parasite but no developmental change
- yellow fever in aedes
- cyclo-propagative
- multiplication and developmental change
- plasmodium in anopheles, leishmaniasis
- cyclo-developmental
- developmental change but no multiplication
- microfilariae, L1 to L3 larva
23
Q
parasitic fleas
A
- ectoparasites
- live outside host for significant part of life cycle
- obligatory blood feeders
- larvae feed on debris assoicated with bedding and nest material
- attachment time varies
- e.g. rodent flea - transient feeders
- e.g. burrowing chigoes - permanent feeders
24
Q
yersinia pestis
A
- route of entry determines type of plague
- bubonic - lymph node infection
- plenumonic plague - infects lungs
- septicaemic plague - infects blood
- 100% mortality
25
Q
leishmaniasis
A
- phlebotamine sandfly
- 30 of 500 species transmit disease
- linked to environmental changes e.g. deforestation
26
Q
lyme disease
A
- bacterial infection - Borrelia burgdorferi
- infected ticks spread to humans
- 2-year life cycle
- tick attachment to host for 36 hours for infection
- change of hosts during spring/autumn
- increased risk of infection
