Antenna (biology)

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Antenna (biology)

Antennae (singular: antenna) are paired appendage

Appendage

An appendage in the broadest sense is an additional or subsidiary part existing on, or added to, something which can generally still function if the appendage has never existed or is later provided or grown, or will still perform a primary function if the appendage is removed....
s connected to the front-most segments

Morphogenesis

Morphogenesis , is the physical process that gives rise to the shape of an organism. It is one of three fundamental aspects of developmental biology along with the control of cell growth and cellular differentiation....
of arthropod

Arthropod

Arthropods are animals belonging to the Scientific classification Arthropoda , and include the insects, arachnids, crustaceans, and others....
s. In crustacean

Crustacean

Crustaceans are a large group of arthropods, comprising almost 52,000 described species , and are usually treated as a subphylum . They include various familiar animals, such as crabs, lobsters, crayfish, shrimp, krill and barnacles....
s, they are biramous and present on the first two segments of the head, with the smaller pair known as antennules. All other arthropod groups, except chelicerates

Chelicerata

The subphylum Chelicerata constitutes one of the major subdivisions of the phylum Arthropoda, and includes horseshoe crabs, scorpions, spiders and mites....
and proturans which have none, have a single, uniramous pair of antennae.

Antennae are jointed, at least at the base, and generally extend forward from the head.

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Antennae (singular: antenna) are paired appendage

Appendage

Morphogenesis

Arthropod

Arthropods are animals belonging to the Scientific classification Arthropoda , and include the insects, arachnids, crustaceans, and others....
s. In crustacean

Crustacean

Chelicerata

Sensory system

A sensory system is a part of the nervous system responsible for processing sense information. A sensory system consists of sensory receptors, neural pathways, and parts of the brain involved in sensory perception....
s, although the exact nature of what they sense and how they sense it is not the same in all groups, nor always clear. Functions may variously include sensing touch, air motion, heat, vibration (sound), and especially olfaction

Olfaction

Olfaction refers to the sense of smell. This sense is mediated by specialized sensory cells of the nasal cavity of vertebrates, and, by analogy, sensory cells of the antennae of invertebrates....
(smell) or gustation (taste).

Insects

In insect

Insect

Insects are the biggest class of arthropods and the only ones with wings. They are the most diverse group of animals on the planet. They are most diverse at the equator and their diversity declines toward the poles....
s, olfactory receptor

Olfactory receptor

Olfactory receptors expressed in the cell membranes of olfactory receptor neurons are responsible for the detection of odor molecules. Activated olfactory receptors are the initial player in a signal transduction cascade which ultimately produces a nerve impulse which is transmitted to the brain....
s on the antennae bind to odour

Odor

An odor or odour is a volatilized chemical compound, generally at a very low concentration, that humans or other animals perceive by the sense of olfaction....
molecules, including pheromone

Pheromone

A pheromone is a chemical that triggers a natural behavioral response in another member of the opposite gender of the same species. There are alarm signal pheromones, food trail pheromones, sex pheromones, and many others that affect behavior or physiology....
s. The neuron

Neuron

Neurons are responsive cell in the nervous system that process and transmit information by electrochemical Signal . They are the core components of the brain, the vertebrate spinal cord, the invertebrate ventral nerve cord, and the peripheral nerves....
s that possess these receptors signal this binding by sending action potential

Action potential

An action potential is a self-regenerating wave of electrochemical activity that allows nerve cells to carry a signal over a distance. It is the primary electrical signal generated by nerve cells, and arises from changes in the permeability of the nerve cell's axonal Cell membranes to specific ions....
s down their axon

Axon

An axon or nerve fiber is a long, slender projectionof a nerve cell, or neuron, that conducts action potentialaway from the neuron's cell body or soma....
s to the antennal lobe

Antennal lobe

Antennal lobe is the deutocerebral neuropil of the insect which receives the input from the olfactory sensory neurons on the antenna . Functionally, it shares some similarities with the olfactory bulb in vertebrates....
in the brain

Brain

The brain is the center of the nervous system in all vertebrate, and most invertebrate, animals. Some primitive animals such as cnidarian and echinoderm have a decentralized nervous system without a brain, while sponges lack any nervous system at all....
. From there, neurons in the antennal lobes connect to mushroom bodies

Mushroom bodies

The mushroom bodies or corpora pedunculata are a pair of structures in the brain of insects and other arthropods. They are usually described as neuropils, i.e....
that identify the odour. The sum of the electrical potentials of the antenna to a given odor can be measured using an electroantenogram.

The three basic segments of the typical insect antenna are the scape (base), the pedicel (stem), and finally the flagellum, which often comprises many units known as flagellomeres. Muscles are only present in the two first segments, the scape and pedicel. The scape is surrounded by a membranous region of the head. It pivots on a single marginal point called the antennifer, allowing it to move in any direction. The number of flagellomeres can vary greatly, and is often of diagnostic importance. True flagellomeres have a membranous articulation between them, but in many insects, especially the more primitive groups, the flagellum is entirely or partially composed of a flexible series of small annuli, which are not true flagellomeres. In many beetle

Beetle

Beetles are the group of insects with the largest number of known species. They are placed in the order Coleoptera , which contains more described species than in any other order in the animal, constituting about 25% of all known life-forms....
s and in the chalcidoid wasps, the apical flagellomeres form a club, and the collective term for the segments between the club and the antennal base is the funicle (or anteniar); for traditional reasons, in beetles it is the segments between the club and the scape, but in wasps, it is the segments between the club and the pedicel. In the groups with more uniform antennae (for example: Diplopoda), all segments are called antennomeres. Some groups have a simple or variously modified apical or subapical bristle called an arista
Arista (biology)

In insect anatomy. The arista is a simple or variously modified Wiktionary:apex or subapical bristle, arising from the third Antenna segment. It is the Evolution remains of antennal segments, and may sometimes show signs of segmentation....
(this may be especially well-developed in various Diptera).