Animal antennae

Many animals, insects, and crustaceans have antennae, which serve as feelers or communication tools. Together with the morphologies of the eyes, head, wings, legs, and body, antennae also serve as a criterion to distinguish between families.

Antennae have many forms in different species. All flies have antennae, which can be of two types. The first, found in the members of the suborder Nematocera, such as crane flies, midges, and gnats, are whiplike, with two basal segments called the scape and the pedicel, as well as a flagellum of many similar segments. The second type, encountered in all members of the Brachycera group, has a flagellum contracted into a compound third segment. Crayfish tend to shed the oldest, most distal parts of their antennule once their carapace reaches about seven millimeters in length, and new growth occurs from the proximal end of the flagellum. The antennal flagellum also serves as the multimodal sensory organ that contains mechanoreceptors and chemoreceptors in crickets.

Cockroaches use their antennae to locate a wall and retain a constant distance from it as they move along it. While running, they may make up to twenty-five body turns per second to avoid collisions with outward projections. It is believed that exceptionally efficient sensory input from the flagellum of the antenna reports the exact distance from the wall to evoke those turns.

The trap-jaw ant, found in the warmer parts of the western hemisphere, has a jaw that moves one thousand times faster than the human eye can blink. These ants use their hair antennae to detect prey; the touch of the antenna against the prey triggers the jaws to snap shut immediately. Antennal contact appears to be prevalent also in the organization of ant colonies, especially when ants from another colony are nearby. The contact increase is proportional to the number of ants present, in agreement with the increased density of nest mates.

Antennae, Pheromones, and Sexual Selection

Pheromones appear to play a vital role in insect survival and in communication between members of the same species. The selection and transportation of these lipophilic messengers are achieved by carrier proteins moving through the hydrophilic sensillum lymph in the antennae toward the membrane receptors. Wing fanning appears to enhance the air penetration of silkworm moth pheromones, as well as their interception by antennae. Odor recognition and resultant behavior are achieved among the members of the Drosophila genus, sometimes called small fruit flies or wine flies, through sensory neurons that exist in either the antennae or the maxillary palp. A study using locusts has indicated, however, that insects fed for the final two stadia (the period of time between molts) on nutritionally adequate synthetic foods have fewer sensilla on the maxillary palps and antennae than insects fed on the normal diet of seeding wheat.

Experiments on Drosophila species indicated that hemothorax homeobox genes are antennal selector genes. Biological clocks that monitor daily cyclical activity appear to exist in fruit fly tissues of the antennae and other organs. These genes showed an increasing intensity of the reporter protein as a function of adult age.

The relationship between antenna morphology and sexual selection in the cerambycid or long horned beetle (Stenurella melanura) indicates that males with antennal symmetry appear to win more battles with other males for a female, while females with more symmetrical antennae were much more desirable to males. Researchers have also discovered that the mating behavior in a male sphinx moth is the result of the reaction of nerve cells in his antennae to a pheromone that is emitted by a female moth’s abdomen. The same scientists found out that once female moths absorb male nerve cells through the implantation of the males’ antennae in their heads, these female moths exhibit male mating habits. This shows that transsexually grafted antennae alter the pheromone-affected behavior in a moth.

The olfactory blocking ability of the honeybee is severely hampered when input from one antenna is removed, resulting in the bee’s inability to neutralize one odor through the effect of another odor. This indicates that, although antennae sensory neurons are important, more central processing regions of the brain must be involved in this blocking phenomenon. Other studies have proposed that the chemical L-glutamate activates antennular grooming behavior (AGB) in spiny lobsters through a mechanistic pathway that is nonolfactory. AGB is an important behavior in insects that live in groups, like cockroaches, in keeping the antennae's olfactory neurons functioning properly by removing environmental contaminations and removing female pheromones from male insects' antennae. It also serves an important role in strengthening social structures, bonding, and conflict resolution.

Scientists continued to make new discoveries regarding antennae into the twenty-first century. In 2018, researchers discovered a juvenile Magnusantenna wuae from the Coreidae family preserved in amber. This Cretaceous-era insect is believed to have used its wide and bizarre antenna to confuse predators as it looked for food and in sexual selection behaviors. The Protoliotapaleus was also found preserved in amber. Its antennae were around 8 millimeters (one-third inch) long, more than triple its body length, which is believed to have been used during fights between males.

Principal Terms

Lipophilic: fat soluble or water insoluble

Master Control Gene: a gene that single-handedly triggers the formation of an organ or structure

Maxillary: pertaining to the upper jawbone

Olfactory: pertaining to the sense of smell

Bibliography

Bacon, Jonathan. “Insect Pheromones: Beauty Is in the Antennae of the Beholder.” Nature, vol. 323, no. 6091, 1986, pp. 758–59, doi.org/10.1038/323758a0.

Baraniuk, Chris. “Cretaceous Insect Discovered with Extremely Weird Antennae.” New Scientist, 19 Feb. 2020, www.newscientist.com/article/2234646-cretaceous-insect-discovered-with-extremely-weird-antennae. Accessed 1 July 2023.

Camhi, J. M., and E. N. Johnson. “High-Frequency Steering Maneuvers Mediated by Tactile Cues: Antennal Wall Following in the Cockroach.” The Journal of Experimental Biology, vol. 202, no. 5, 5 Mar. 1999, pp. 631-643.

Copley, Jon. “Artful Dodgers.” New Scientist 161, no. 2174, 20 Feb. 1999, 16.

Kim, Jaeseob, Angela Sebring, and Jeffrey J. Esch. “Integration of Positional Signals and Regulation of Wing Formation and Identity by Drosophila Vestigial Gene.” Nature 382, 11 July 1996, 133-138.

Miller, Julie Ann. “It’s All in the Antennae.” Science News 126, 3 Nov. 1984, 281.

Moller, Anders Pape, and Carmen Zamore Munoz. “Antennal Symmetry and Sexual Selection in a Cerambysic Beetle.” Animal Behaviour, no. 54, Dec. 1997, pp. 1509-1515. doi: 10.1006/anbe.1997.0565.

"Types of Antennae." American Museum of Natural History, www.amnh.org/learn-teach/curriculum-collections/biodiversity-counts/arthropod-identification/arthropod-morphology/types-of-antennae. Accessed 20 Sept. 2024.

Wada-Katsumata, Ayako, and Coby Schal. “Antennal Grooming Facilitates Courtship Performance in a Group-living Insect, the German Cockroach Blattella germanica.” Scientific Reports, vol. 9, 27 Feb. 2019: doi:10.1038/s41598-019-39868-x.