Lecture 18: Ecdysozoans - Arthropods

Summary (4)

– found in all major environments

– Major role in food chains: predator, prey, parasite, and symbiont

– Pollinators

– Decomposers and scavengers

Why are arthropods so successful? (6)

– High number of species and habitat diversity

– Adaptable body plan

– Thrive in a range of environments

– Segmented body

– Have been fused to allow greater control of body regions and specialization

– Exoskeleton with jointed appendages

What does the name arthropod mean?

Jointed feet

Adaptable body plan

– Early forms: pronounced segmentation, little specialization

– Fusion of segments to produce super segments

– Allow specialization of body and function

– Allow specialization of appendages away from wormlike organisms

Definition:

tagmatisation/tagmosis

-fusion of segments

Definition:

Tagmata

Super segments

Arthropod features (6)

– Exoskeleton

– Segmentation

– Tagmata

– Appendages

– Circulatory system

– Respiratory structures

Arthropod features:

Tagmata (4)

– Amalgamation of segments

– Head, thorax, abdomen

– Head, trunk

– Cephalothorax, abdomen

Arthropod features:

Appendages (2)

– tool for every purpose

– For mobility, sensing, feeding, reproduction

Arthropod features:

Respiratory structures (3)

– Gills

– Spiracles tracheae

– Book lungs

Arthropod features:

Circulatory system (4)

– Open (haemocoel)

– Ventral nervous system

– Complex expiratory system

– Sexual reproduction

What is the purpose of the exoskeleton?

– Physical and physiological protection

– Muscle attachment

– Body support

Exoskeleton

– Protein and chitin

– Must molt to grow

ecdysis (2)

– Temporary vulnerability

– Energetically expensive

Arthropod lineages (5)

-trilobites

-chelicerates

-hexapods

-crustaceans

-myriapods

Which of the arthropod lineages are extinct?

Trilobites

To which arthropod lineage do insects and six legged relatives belong?

Hexapods

How are living arthropods organized?

Based on mouthparts

What are the two groups of arthropod mouthpart organization?

-Chelicerate

-Mandibulate

chelicerate mouthparts

-chelicerae for grasping food

-fanglike or pincers

mandibulate mouthparts

-mandibles for chewing

chelicerae in spiders (2)

-hollow

-venomous

summary:

chelicerates

-simple body plan: chephalothorax, abdomen

-no true antennae

-chelicerae, pedipalps

-eyes: up to 8 single lens eyes

-adults: 4 pairs of legs

-parasitic chelicerates can reside on other chelicerates

chelicerates:

chelicerae

-paired feeding appendages

-modified into fangs (spiders) or pincers

chelicerates:

pedipalps

-palps: feeding or sensory

Arachnids are chelicerae’s. Who are the arachnids? (4)

-spiders

-scorpions

-ticks

-mites

-chelicerae

vet importance:

ticks (acarines) (7)

-external parasites: mammals, birds, reptiles

-1-3 host individuals can be used in each life cycle

-heavy blood feeders: female ticks engorge (up to 100x)

-saliva assists feeding

-are vectors for disease spread

-secretes neurotoxins (paralysis tick)

-can cause: blood loss, skin damage

ticks (acarines)

vectors for…

Babesia (tick fever); (canine erlichiosis - in northern Australia)

what is an example of a 1-host tick?

cattle tick

Rhipicephalus (Boophilus) australis

Rhipicephalus (Boophilus) australis

cattle tick lifecycle

Female drops of host and lays up to 3000 eggs. Then she dies and the eggs becomes larvae. The larva does questing which is search for a new host. Once on the new host they complete their growing stages on the host until the female is ready to lay eggs.

definition:

hypostome

tooth denticulate. These are backwards facing teeth that make it really difficult to remove a tick from its host

are mites free-living or parasitic?

free living

what is an example of an ectoparasitic species?

scabies mite

summary:

Scabies mites (3)

-live in burrows in the skin

-egg to adult on one host transmits via contact

-causes mange

what arthropod causes mange?

-scabies mite

definition:

mange

-hair loss

-scabs

-keratinised skin with mites

-found by skin scraping

mange

-scabies mite