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How do arthropods use separate taste and smell systems to detect chemicals?

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A pine grosbeak with pink and gray plumage perches on a branch, eating red berries among autumn foliage. — Chemoreception Animals, such as this pine grosbeak, use chemoreception to respond to chemicals that can be tasted and smelled in their environments. Many of these chemicals affect behaviors such as food preference and defense.

Arthropods are unique among invertebrates for possessing distinct senses of taste and olfaction, which are facilitated by specialized structures called sensilla that penetrate the protective cuticle covering their bodies.1

Structural Differences

The two systems are distinguished by the morphology of the pores in these sensilla:
* Taste: These sensilla are typically uniporous, featuring a single pore (0.15–2 μm in diameter) at the tip of the hair. They are primarily located on feeding appendages, the ventral surfaces of the tarsi (feet), and sometimes on the body or egg-laying apparatus.1
* Smell: These sensilla are multiporous, containing many small pores (about 10 nm in diameter) scattered across the hair surface. They are generally restricted to feelerlike structures at the front of the animal, such as antennae in insects or antennules in crustaceans.1

Physiological Function

In the taste system, receptor cells often respond to specific food-related chemicals, such as sugars or salts, and their axons project directly to the central nervous system without intermediate synapses. Conversely, olfactory receptor cells express specific receptor proteins and their axons converge onto structures called glomeruli in the brain or posterior nervous system, similar to the organization found in vertebrates.1