ENTO 306 Insect Structure Function EXAM 1

what do leps eat

nectar, pollen, blood, sweat

What are insect mouthparts used for besides eating?

Contain sensory receptors that allow insects to taste, touch, and detect chemical cues. These help insects determine whether food is suitable to eat.

What senses can insect mouthparts detect?

Taste, touch, mechanical, and chemical cues

What nutrients does pollen provide?

Protein and lipids

What nutrient does nectar primarily provide?

Carbohydrates and sugars

What does monocondylic mean?

One articulation point on the insect's head or body for joint movement.

What does dicondylic mean?

Two articulation points with the head capsule providing greater stability and control during chewing.

What does entognathous mean?

Mouthparts are enclosed or recessed within the head capsule

What does ectognathous mean?

Mouthparts that are externally exposed and visible outside the head capsule

What is the hypopharynx?

Tongue-like structure in the insect mouth that helps manipulate food and mix it with saliva.

What is the tentorium?

Internal framework of the insect head formed by infoldings of the head capsule. It provides structural support and attachment sites for muscles, including feeding muscles.

What are mechanoreceptors?

Sensory receptors that detect mechanical stimuli such as pressure, touch, movement, vibration, and stretching.

How does crop expansion affect feeding?

Mechanoreceptors detect the stretching and signal the nervous system that the insect has consumed food, helping regulate and eventually stop feeding.

What happens to feeding behavior after an insect feeds?

Insects generally experience decreased motivation or interest in feeding because internal signals indicate that their nutritional needs have been satisfied.

How can defecation affect feeding in grasshoppers?

Can stimulate feeding behavior in grasshoppers. Emptying the digestive tract reduces gut fullness and can contribute to renewed feeding.

Why do insects often prefer younger leaves?

Generally softer and easier to consume. Also contain higher amounts of nutrients and water.

Why are older leaves harder for insects to consume?

Typically develop thicker and more rigid cell walls and increased structural tissue, making them tougher and less digestible.

Why do grasshoppers generally need less water than caterpillars?

Adaptations that help conserve water and obtain much of their water from their food, while caterpillars generally have higher water requirements.

What are the three major regions of the insect alimentary canal?

Foregut, midgut, and hindgut.

What is the function of the pharynx?

Helps pull food into the digestive tract. Strong muscles contract to create suction and move food from the mouth toward the esophagus.

What is the function of the esophagus?

A tube that transports food from the pharynx to the crop. It is primarily a passageway rather than a major site of digestion or absorption.

What is the crop?

An enlarged portion of the foregut used primarily for temporary food storage.

How is the crop different from the esophagus?

The ___ is a relatively narrow passageway, while the ___ is enlarged and can store a larger quantity of food.

What is the main function of the midgut?

The primary region for digestion and nutrient absorption in the insect alimentary canal.

What are gastric ceca?

Finger-like pouches associated with the midgut that increase the digestive and absorptive surface area. Main role is absorption

What are Malpighian tubules?

The insect's primary excretory organs. They remove nitrogenous wastes from the hemolymph and help regulate water and ion balance. Compared to kidneys.

What is the function of the ileum?

Part of the hindgut and is involved in moving digestive material and absorbing water, ions, and other substances.

What is the main function of the rectum?

Reabsorbs water and important ions from waste before defecation, helping insects conserve water.

Why is water reabsorption important to insects?

Insects can lose water rapidly. Reabsorbing water from feces helps prevent dehydration.

What are the major functions of the hindgut?

Involved in water and ion reabsorption, movement of waste, and formation of feces.

What is necrophagy?

Feeding on dead or decaying animal tissue.

What are the grape-like structures in an insect digestive system diagram?

They are the salivary glands, which produce saliva and digestive substances that are released into the mouth.

What does insect saliva do?

Can lubricate food, begin digestion, and help insects manipulate or process food. Its composition varies depending on the insect and its diet.

What are the functions of the foregut?

Involved in ingestion, food transport, temporary storage, and mechanical processing. It includes the pharynx, esophagus, crop, and often the proventriculus.

What is the pathway of food through the insect alimentary canal?

Mouth → pharynx → esophagus → crop → proventriculus → midgut → hindgut → rectum → anus.

What does amylase break down?

Breaks down starch and other complex carbohydrates into smaller sugars.

What does invertase break down?

Breaks down sucrose into the simpler sugars glucose and fructose.

What does proteinase break down?

Breaks down proteins into smaller peptides and amino acids.

What does lipase break down?

Breaks down lipids and fats into fatty acids and other smaller components.

What does nectar provide?

Carbohydrates, primarily sugars.

What is the main role of the gastric ceca?

They increase surface area and contribute to digestion and absorption.

What is the main role of the rectum?

Reabsorption of water and ions to conserve water.

Mono vs. di in monocondylic and dicondylic

Mono means one mandibular articulation, while di means two mandibular articulations.

Ento vs. ecto in entognathous and ectognathous

Ento means inside, so mouthparts are enclosed; ecto means outside, so mouthparts are externally exposed.

Difference between illeum and rectum:

___ is involved in the movement of food and absorption.

The ___ helps with the reabsorption of water. Hopes to recycle that water that may be lost.

What is the midgut epithelium and what does it do?

Single layer of absorptive and secretory cells lines the middle section of the digestive tract. Makes enzymes for digestion.

peritrophic envelope

Only in the ventriculus

A thin, protective, semi-permeable layer that surrounds food in the midgut. It separates the food from the midgut epithelium while still allowing digestive enzymes and small digested nutrients to pass through.

peritrophic envelope formed by

proteins, glycoproteins, Chitin microfibrils

two types of peritrophic envelope

Type I - Delaminated from the entire midgut

The envelope is secreted throughout the midgut in pieces/chunks that come together to surround the food

Type II - Secreted as a sleeve in anterior midgut (cardia)

The envelope is secreted continuously as a sleeve from the anterior midgut (cardia), surrounding the food as it moves through the gut.

endopeptidases

Link amino acids together, attack peptide bonds within the protein molecule.

Breaks large proteins into smaller pieces so the insect can absorb the amino acids.

Exopeptidases

remove terminal amino acids from the protein molecule

Carboxypeptidases

Aminopeptidases

amylases

Enzymes that break down starch.

Endo-amylase vs. Exo-amylase

___ cuts α-1,4 bonds within the middle of the starch chain.

Breaks a large starch molecule into smaller pieces.

____ works from the ends of the starch chain, removing glucose units or small sugar units from the ends.

Glucosidases

Take the smaller carbohydrates/disaccharides produced during digestion and break them down into monosaccharides.

The pathways of absorption

Passive absorption depends on the relative concentration of a compound inside and outside the gut, with diffusion taking place from a higher to a lower concentration.

Active absorption depends on some metabolic process to move a substance against its concentration gradient.

Amino acids occurring at low concentrations may be actively absorbed,

via __________, coupled with __________

symports, potassium

Key inorganic ions

Sodium (Na+)

Potassium (K+)

Chloride (Cl-)

Calcium (Ca2+)

Ions move via diffusion, but sometimes they must also overcome an electrochemical gradient (EcG).

Sodium (Na+) needs help (via a Na+/K+ pump) to move from the gut lumen into midgut cells

Protein → peptides → amino acids → insect uses

Protein = food source

Proteins are large molecules, so the insect can't efficiently absorb them as-is.

Peptides = partially digested protein

Proteinases/peptidases cut the large protein into smaller chains called peptides.

Peptides are easier to digest further.

Amino acids = the usable building blocks

Peptides are broken down into individual amino acids.

These can be absorbed through the midgut and used by the insect.

amino acids are required for the production of proteins,

which are used...

for structural purposes

as enzymes

for transport and storage

as receptor molecules

what are the branched chain amino acids

valine

Isoleucine

leucine

essential amino acid

Cannot be created by the insect, must be consumed

Transamination

the transfer of an amino acid group from a pre-existing amino acid

Simple carbs include

glucose

fructose

sucrose

maltose

complex carbs

glycogen

starch

cellulose

Fatty acids are stored & transported as

glycerids

Phospholipids

contains 2 fatty acids, a glycerol backbone, a phosphate head, and a choline head

20 OH ecdysone

molting hormone

Needs cholesterol to activate

Predator insect nutrient intake

proteins and lipids

herbivore insect nutrient intake

Carbohydrates (starch, pectin, simple sugars),

fat soluble vitamins examples

β-carotene (vitamin A; in visual pigments); vitamin E (reproduction; spermatogenesis and egg maturation)

water soluble vitamins

B vitamins and vitamin C

inorganic compounds (essential elements in cell function)

sodium, potassium, calcium, magnesium, chloride and phosphate

lipogenic compounds

Myo-inositol

choline (found in phospholipids)

Trehalose

Insect blood sugar

heart in insect

Ventrally located

Where does the dorsal vessel run in an insect, and how does it terminate anteriorly?

Runs along the dorsal midline and opens anteriorly and abruptly in most insects into the body cavity (head/thoracic region).

What are the two distinct regions of the insect dorsal vessel?

Posterior heart

Anterior aorta

What is the function of the insect's posterior heart?

It is the contractile, pumping portion of the dorsal vessel equipped with incurrent openings (ostia) and excurrent openings to pull in and pump hemolymph forward.

What is the function of the insect's anterior aorta?

An unperforated tube that conducts hemolymph forward from the heart directly into the open head cavity.

What are hemopoietic organs in insects?

Specialized tissue structures containing stem/progenitor cells where hemocytes are formed, differentiated, and released into circulation

Why is insect circulation considered an "open" system relative to the dorsal vessel?

Hemolymph is pumped forward through the dorsal vessel and empties freely into the body cavity (hemocoel) to directly bathe the organs, rather than staying contained inside closed capillaries.

Nutritional amino acids come from

proteins and peptides (via peptidases)

When an insect has extra fatty acids that it doesn't immediately need, it stores them as

Triacylglycerols (TAG)

A triacylglycerol has:

1 glycerol + 3 fatty acids

Storage

When the insect needs energy, triacylglycerols TAG can be broken down and converted into

diacylglycerol.

A diacylglycerol has:

1 glycerol + 2 fatty acids

Transport

insect blood cells are called

hemocytes

two major areas of insect immunity

Hemocytic (cellular) immunity - very rapid

Humoral (cell-free; involves proteins & peptides) immunity - much slower,

hours later