Molting and Eyes Flashcards
What is Ecdyses?
It is another term for moulting and is important as it divides the life cycle of hexapods and other anthropods into a series of instars or stages.
Moulting is taxon specific and can look very different for different groups, what can this process depend on and when does it stop?
It can depend on availability of food, temperature, and humidity.
Moulting stops after maturity
How is moulting induced?
Through the increased production of ecdysteroids which function as moulting hormones
What is the first step of molting?
Apolysis: the separation of the old cuticle from the epidermis
What is the second step of molting?
Epidermal cells begin to secrete the new cuticle, starting with the outer layers and working inward
What is the third step of molting?
Epidermal cells produce enzymes responsible for the degredation of the old cuticle. Up to 90% of the old cuticle is digested by chitinases and protease enzymes that recycle the old cuticle.
What is the fourth step of molting?
After all of the wax layers are in place the insect produces wax that is secreted through pore canals
What is the fifth step of molting?
The insect sheds its old cuticle
What is the sixth step of molting?
The insect first escapes from the old cuticle, it is very white/pale and the insects are known to be teneral
What is the seventh step of molting?
The insect must expand its body size while the new cuticle hardens and dries.
Within insect eyes we have sensory cells, what are they called?
Rhabdomere
What forms a rhabdom?
Usually two or more cells that are united to form an optic rod or rhabdom
Rhabdoms are enclosed in single eye units called…
ommatidia (singular is ommatidium)
What forms the eyes?
grouped together ommatidia
In adults we have two types of eyes, what are they?
- Simple eyes
- Compound eyes
Where are the simple eyes usually found in adults?
They are found dorsally (on top of the head) and are usually 3 in a triangle formation
Where are the simple eyes usually found in larvae?
Usually are found more laterally and can be called stemmata or lateral ocelli.
Simple eye function
Usually to discern night and day (light and dark)
Make up of the simple eye?
Usually a large cornea that is transparent in order to admit light rays) it is made up of very few rhabdoms
Compound eyes can have how many ommatidia?
Thousands, however the number can vary as dragonflies can have more than 25,000
What can insects perceive with their eyes and what is this type of sight called?
They can perceive form, color, and movement. Their sight is compromised by the design of their eye which tends to portray objects as broken into smaller pieces (mosaic vision)
Among compound-eyed insects the majority are… while some are…
- Bichromatic
- Trichromatic
Can some insects detect ultraviolet light?
Yes, insects may have photoreceptors that detect ultraviolet light as many flowers reflect ultraviolet light
