Hair-pencil

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Danaus chrysippus showing hair-pencil at the end of the abdomen Danaus chrysippus male 2 by kadavoor.jpg
Danaus chrysippus showing hair-pencil at the end of the abdomen

Hair-pencils and coremata are pheromone signaling structures present in lepidopteran males. Males use hair-pencils in courtship behaviors with females. The pheromones they excrete serve as both aphrodisiacs and tranquilizers to females as well as repellents to conspecific males. [1] Hair-pencil glands are stored inside the male until courtship begins, at which point they are forced out of the body by sclerotized levers present on the abdomen. [2] Coremata (the singular form being corema) are very similar structures. Their exact definition is confused by early descriptions but they are more specifically defined as the internal, glandular, eversible structures that bear the hair-pencils and can be voluntarily inflated with hemolymph or air. [3] [4]

Pheromone secreted or excreted chemical factor that triggers a social response in members of the same species

A pheromone is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting like hormones outside the body of the secreting individual, to impact the behavior of the receiving individuals. There are alarm pheromones, food trail pheromones, sex pheromones, and many others that affect behavior or physiology. Pheromones are used from basic unicellular prokaryotes to complex multicellular eukaryotes. Their use among insects has been particularly well documented. In addition, some vertebrates, plants and ciliates communicate by using pheromones.

Lepidoptera Order of insects including moths and butterflies

Lepidoptera is an order of insects that includes butterflies and moths. About 180,000 species of the Lepidoptera are described, in 126 families and 46 superfamilies, 10 per cent of the total described species of living organisms. It is one of the most widespread and widely recognizable insect orders in the world. The Lepidoptera show many variations of the basic body structure that have evolved to gain advantages in lifestyle and distribution. Recent estimates suggest the order may have more species than earlier thought, and is among the four most speciose orders, along with the Hymenoptera, Diptera, and Coleoptera.

Courtship period in a couples relationship which precedes their engagement and marriage

Courtship is the period of development towards an intimate relationship wherein a couple get to know each other and decide if there will be an engagement. A courtship may be an informal and private matter between two people or may be a public affair, or a formal arrangement with family approval. Traditionally, in the case of a formal engagement, it has been perceived that it is the role of a male to actively "court" or "woo" a female, thus encouraging her to understand him and her receptiveness to a proposal of marriage.

Contents

Behavioral use of hair-pencils

Male moths are attracted from relatively long distances by females releasing pheromones; when they are close enough to the females to begin courtship, the hair-pencils are extruded from the abdominal cavity and pheromones are fanned towards the female. [5] Fanning can occur in various ways including extruding and retracting the hair-pencils, wing or abdominal movement, or flight in front of the female. [2] When the female moth becomes receptive to the male hair-penciling, she will flick her antennas rapidly in response to his pheromone cues. [6] If the female likes the male blend of pheromones, then she will extend her abdomen and copulation begins. [2]

Hair-pencil pheromone effects

A closeup of the hair-pencil on Pterodecta felderi Pterodecta felderi 2.jpg
A closeup of the hair-pencil on Pterodecta felderi

It has been shown that the hair-pencil pheromones serve both as an aphrodisiac or tranquilizer for the female, but sometimes as a repellent to other conspecific males. In an experiment with heliothine moths, male hair-pencil compounds were extracted and tested against various male and female treatments. [1] It was found that not one specific compound triggered a response in females, but a blend was required. Additionally it is thought that the specific ratio of each of the compounds found in the male moths helps females determine a suitable male from her species. Heliothine moths use similar hair-pencil compounds in different ratios and this is enough for the female to differentiate conspecifics from other species. [1] Males are able to detect competitors through hair-pencil compounds, but extra competitors do not cause great increases in display rate. [5] This perhaps is due to the suppressing effect of hair-pencil pheromones on competitors. Pheromones have also been demonstrated to show the age of the male. As males age the pheromone chemical ratios change slightly. Females can distinguish between males by these changes and pick a more suitable mate. [6]

Heliothinae subfamily of insects

Heliothinae is a small subfamily of moths in the family Noctuidae. There are about 400 species described worldwide. They are found predominantly in semiarid subtropical habitats.

Plants and insect relations

Some of the pheromone compounds that are produced in the hair-pencils of the insects have been found to come from plants . In particular, pyrrolizidine alkaloids have been found to play a role in male pheromones. These compounds can be formed by de novo synthesis or by modifying a pre-existing pyrrolizidine alkaloid that is consumed from the plant. These base compounds can be either eaten in the larval stage or imbibed in the adult stage. They are so important that stepping on a substance containing these compounds causes immediate proboscis extension in adults. [7] Studies have also been done testing the effects of growth of the hair-pencil organs related to the ingestion of plant pyrrolizidine alkaloids. It was found that without the plant derived compounds the hair-pencil organs are smaller. The alkaloid compounds are transformed after ingestion in the hemolymph. The stimulatory effects of the alkaloid derived compounds begin in the larval stages and are displayed in adult stages. [8]

De novo synthesis refers to the synthesis of complex molecules from simple molecules such as sugars or amino acids, as opposed to recycling after partial degradation. For example, nucleotides are not needed in the diet as they can be constructed from small precursor molecules such as formate and aspartate. Methionine, on the other hand, is needed in the diet because while it can be degraded to and then regenerated from homocysteine, it cannot be synthesized de novo.

Proboscis an elongated appendage from the head of an animal, either a vertebrate or an invertebrate

A proboscis is an elongated appendage from the head of an animal, either a vertebrate or an invertebrate. In invertebrates, the term usually refers to tubular mouthparts used for feeding and sucking. In vertebrates, a proboscis is an elongated nose or snout.

Hemolymph body fluid

Hemolymph, or haemolymph, is a fluid, analogous to the blood in vertebrates, that circulates in the interior of the arthropod body remaining in direct contact with the animal's tissues. It is composed of a fluid plasma in which hemolymph cells called hemocytes are suspended. In addition to hemocytes, the plasma also contains many chemicals. It is the major tissue type of the open circulatory system characteristic of arthropods. In addition, some non-arthropods such as molluscs possess a hemolymphatic circulatory system.

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Hydroxydanaidal chemical compound

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References

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