Arthropods and Disease: Morphological Adaptations

Arthropod Characteristics

• Segmented bodies arranged into regions (tagmata)

• Have chitinous exoskeleton that must be shed

• Paired appendages are jointed

• Bilateral Segments

• Nervous system is dorsal

• Circulatory system is open and Ventral

Types of Mouthparts

1. Chewing

2. Piercing and Sucking

Blood Feeding Mouthparts:

Telemophages

Selenophages

Telemophages

Lacerate (saw) into host skin and feed on pools of blood at bite site.

Ex: Black flies, Horse flies, Deer Flies, and Biting Midges

Selenophages

Penetrate individual capillaries and feed directly on host blood

Ex: Mosquitoes, Bed bugs, Kissing bugs, Sucking lice

Sucking Lice

• Labrum highly modified to haustellum, which surrounds other mouthparts

• At the tip are teeth, which are used to anchor the mouthparts to the hosts

Flea Legs

• Hind legs modified for Jumping

• Enlarged, muscular femur

• Resilin

  • Stores energy and increases the efficiency of the hind legs

Lice Legs

• Cling tenaciously to hosts

• Modified tibia and and tarsus, tibiotarsal claw

Tick Legs

• Forelegs have enlarged claws

• Quickly grasp passing hosts and facilitate holding onto skin during feeding and mating

Rodent Mites Legs

Enlarged Legs for clasping the fur of rodent hosts

Scabies Mites

• All legs are reduced and have elongate apoteles with terminal suckers

• Move about quickly on the skin surface

Diptera Antenna

Have receptors that detect molecules emanating from the skin and in the exhaled breath of potential hosts

Diptera Antennas in Mosquitoes

• Johnston’s Organ: specialized for detecting airborne vibrations.

  • Can cue in on vibrations produced by host movements and vocalizations

Flea Antenna

• Short - flattened fits into a protective groove on the side of the head

  • Allows antenna to be retracted so its not damaged or impeding of movement.

• Compound Eye

Solenophages

• Receptors concentrated near the tip of the proboscis or rostrum

• Used to detect precise location of capillaries beneath the surface of the skin

Sensilium

• Dorsal portions of the terminal abdominal segments

• Specialized for detecting host associated cues such as vibrations and temperature gradients

Trichobothria

Common in mites and other arachnids for detecting airborne + substrate

Haller’s Organ

• Ticks

• Located on the dorsal aspect of the tarsus on first pair of legs

• Functions in detection of temperature, air movements, host odors, and other environmental cues