5.18 Structure of the cuticle in the larva and adult Flashcards
What is the cuticle?
The cuticle is the structure that forms the outer covering of all insects, including honeybees.
What function does the cuticle serve regarding water loss?
The cuticle provides a waterproof layer that reduces water loss from the bee, decreasing the chance of dehydration.
What internal protection does the cuticle provide?
The cuticle protects the delicate internal organs of the bee.
What are apodemes?
Apodemes are attachment points for muscles on the cuticle that allow the bee to move.
Why do some areas of the cuticle need to be harder than others?
Some areas, like the sting and mandibles, need to be harder to perform specific functions such as penetrating tissue or cutting.
What are invaginations in the cuticle?
Invaginations are depressions that form structures such as the trachea, mouth, oesophagus, crop, proventriculus, and rectum.
What is the first layer of the cuticle called?
The first layer of the cuticle is known as the epidermis, made of metabolically active epidermal cells.
What are the layers of the cuticle from inside to outside?
The layers are the epidermis, endocuticle, exocuticle, and epicuticle.
What are the main chemicals that form the cuticle?
The two main chemicals are chitin and sclerotin.
Hard
What is the role of sclerotin in the cuticle?
Sclerotin darkens and hardens during tanning, contributing to the cuticle’s hardness.
Soft
How does chitin contribute to the cuticle?
Chitin is tough but more flexible than sclerotin, providing flexibility to the cuticle.
How does the composition of the cuticle change from inside to outside?
Generally, the levels of chitin decrease and the levels of sclerotin increase from the inside to the outside.
What is contained in the epicuticle?
The epicuticle contains no chitin but does contain wax and sclerotin, making it waterproof.
How does the composition of the cuticle vary in different areas?
The composition changes; for example, hard plates have all layers, while joints lack the epi and exocuticle layers for flexibility.
What are taenidia?
Taenidia are spiral thickenings in the trachea that have thicker and more sclerotised cuticle for extra support.
What are the stomodeum and proctodeum?
They are invaginations of the epidermis lined with cuticle (intima).
What is the oesophagus?
A slender tube lined with thick cuticle and surrounded by circular muscles.
What is the crop?
An extension of the oesophagus capable of stretching to take a heavy load.
What is the proventriculus?
A structure with walls lined with dense cuticular intima.
What is the rectum?
A part with an epithelial wall lined with thin cuticular intima.
What is chitin?
Flexible chitin is the major structural part of the integument where flexibility is necessary, such as in bodily parts that must stretch to contain accumulated liquids or that form joints between rigid parts of the exoskeleton.
What is the procuticle?
The procuticle is the main chitinous layer of the cuticle, which is impregnated, thickened, and reinforced with harder materials for rigidity.
What is the epicuticle?
The epicuticle is a thin, waxy, water-resistant outer layer covering the procuticle, containing no chitin.
What are the two major layers of the chitinous procuticle?
The two major layers of the chitinous procuticle are the outer exocuticle and the inner endocuticle.
What is the structure of the endocuticle?
The endocuticle is a laminated structure of layers of interwoven fibrous chitin and protein molecules.
What occurs in the exocuticle?
The exocuticle is the layer in which any major thickening and armoring occurs.
What are sclerites?
Sclerites are hardened plates in the exoskeleton that may serve as protective armor or mechanical components.
What are tergites?
Tergites are sclerites that bear on the tergum.
What are sternites?
Sternites are sclerites that commonly bear on the sternum.
What are pleurites?
Pleurites are sclerites that bear on the pleura.
What sits on the epidermis?
The cuticle sits on the epidermis.
What substances does the cuticle secrete?
The cuticle secretes substances including chitin, arthropodin, polyphenols, cuticulin, and cuticular lipids.
What is chitin?
Chitin is a long-chain polymer of N-acetylglucosamine, which is a derivative of glucose.
What is arthropodin?
Arthropodin is a protein injected between the chitin threads.
What role do polyphenols play?
Polyphenols are used for tanning the arthropodin and eventually forming sclerotin.
What is cuticulin?
Cuticulin is a tanning protein.
What are cuticular lipids?
Cuticular lipids are paraffin hydrocarbons used for waterproofing the epicuticle.
What is the thickness of the cuticle?
The thickness of the cuticle is circa 0.2µm.
