ACE Animal Anatomy & Physiology 3 — Questions and Answers
Question 1: Which type of insect sensillum is specialized for detecting contact chemicals (taste)?
- Trichoid sensillum
- Basiconic sensillum (Correct answer)
- Coeloconic sensillum
- Ampullaceal sensillum
Correct answer: Basiconic sensillum
Basiconic sensilla are short, peg-like structures found on mouthparts and tarsi that house contact chemoreceptors for taste.
Question 2: The corpora allata produce which hormone critical for maintaining larval characteristics in insects?
- Ecdysone
- Juvenile hormone (Correct answer)
- Prothoracicotropic hormone
- Bursicon
Correct answer: Juvenile hormone
Juvenile hormone (JH) produced by the corpora allata suppresses metamorphic changes, keeping the insect in its larval form through successive molts.
Question 3: In a cockroach, the cercal system is primarily used for:
- Detecting pheromones in the environment
- Sensing airborne vibrations and triggering escape responses (Correct answer)
- Thermoregulation via convective heat loss
- Orienting toward light sources
Correct answer: Sensing airborne vibrations and triggering escape responses
Cerci bear mechanoreceptive hairs that detect low-frequency air currents caused by approaching predators, triggering rapid escape.
Question 4: Oenocytes in insects are primarily associated with:
- Digestion of proteins in the midgut
- Synthesis of cuticular hydrocarbons and lipid processing (Correct answer)
- Phagocytosis of pathogens in hemolymph
- Production of silk proteins
Correct answer: Synthesis of cuticular hydrocarbons and lipid processing
Oenocytes, found in clusters near the epidermis, synthesize cuticular hydrocarbons critical for waterproofing and chemical communication.
Question 5: The peritrophic matrix in insect midguts functions mainly to:
- Neutralize stomach acid produced during digestion
- Protect midgut epithelium from abrasion and pathogens while allowing enzyme passage (Correct answer)
- Store ingested food between meals
- Produce antimicrobial peptides for immune defense
Correct answer: Protect midgut epithelium from abrasion and pathogens while allowing enzyme passage
The peritrophic matrix is a semipermeable chitin-protein membrane that shields midgut cells from damage and pathogens while permitting digestive enzymes to access food.
Question 6: Which muscle type dominates insect flight in species such as bees and flies that beat their wings at very high frequencies?
- Tubular synchronous muscle
- Asynchronous (fibrillar) flight muscle (Correct answer)
- Cardiac muscle
- Visceral smooth muscle
Correct answer: Asynchronous (fibrillar) flight muscle
Asynchronous flight muscles contract in response to mechanical stretch rather than each nerve impulse, enabling wing-beat frequencies far exceeding neural firing rates.
Question 7: In holometabolous insects, which stage is primarily responsible for energy storage to support metamorphosis?
- Egg
- Late larval instars (Correct answer)
- Pupa
- First adult teneral stage
Correct answer: Late larval instars
Late larval instars (especially the last instar) feed voraciously to accumulate lipids and proteins in the fat body that fuel pupal development.
ACE Animal Anatomy & Physiology 3
Which type of insect sensillum is specialized for detecting contact chemicals (taste)?