Arthropod Sensory Systems

Question 0

How does the cuticle help with sensing stuff

Answer 0

Detect mechanical, chemical and visual stimuli through sensillae in or on the cuticle

Question 1

Why are insects so successful.

Answer 1

Can detect micro habitats in an area and detect fine scale variation in the habitat

Question 2

Describe five arthropod senses

Answer 2

Touch (mechanoreception)
Sound reception
Temperature reception
Chemo reception
Vision

Question 3

Describe the mechanoreception

Answer 3

Three types of bristles all connect via a sensory neuron to a nerve cell. The larger ones are trichoid sensillae. The whole exoskeleton can feel things.
Position mechanoreception: often at neck or form a disc where body plates meet. Provide feedback about the position of the limb/wing- convey a sense of position in the body and respond to a bending of joint

Question 4

Describe sound reception

Answer 4

Can detect a far wider range of frequencies than humans. Organs involved are tympanal receptors and tympanum organs. Usually found between legs or on abdomen. Because they are found in diff positions on diff insects, we knoŵ they evolved many times.
The tympanum is sensitive to airborne vibrations. Best developed on katydids

Question 5

Why is the burrow of mole cricket shaped like a horn

Answer 5

To amplify sound- focuses the emitted sound into a pure frequency

Question 6

Describe chemo reception

Answer 6

Taste, smell. Receptors are located on palps, antennae, ovipositor and tarsi. Receptor leads to recognition site which depolarises membrane and sends a nerve impulse.
Receptors are sensillae with one or more pores on their walls.
Multiporous sensillae are hair/peg like. The pores lead to a chamber- pore kettle that has many pore tubules that meet up wth nerve dendrites for airborne molecules.
Uniporous sensillae have a viscous fluid internally and are thought to respond to contact chemo reception.
Antennae of silkworm moth has about 17000 sensillae and respon to sex pheromones of the female (which is emitted through a hair pencil- specially flattened hairs)

Question 7

Describe vision

Answer 7

Light is focused by a lens onto a small organ that has cells containing light sensitive pigments which convey impulses to a nervous system that integrates the image
Have four light detecting organs:
1) dermal detection- light sensitive cells on body surface- simple detection of light and dark.
2) stemmata of caterpillars- the most simple focusing eye. Corneal lens is cuticular in origin. A cluster of light sensitive cells. The rhabdom is a central meeting of pigment in the surrounding retinula cells . Light is focused here.
3) ocelli (simple eyes)- similar to stemmata but have groups of retinula cells with a region containing photosensitive pigment. The clear corneal lens overlies clear epidermal cells.
4) compound eyes- found in most adult insects and nymphs
Made of individual units (ommatidia) which resemble a single stemma. The visual spectrum is fairly poor in long wavelengths but good in short wavelengths. Can also detect polarised light.
The image detected is poor in detail but the pattern, shape and contrast can be detected. Also accurate in distance perception