''Manduca sexta'' is a

moth Moths are a group of insects that includes all members of the order Lepidoptera that are not Butterfly, butterflies. They were previously classified as suborder Heterocera, but the group is Paraphyly, paraphyletic with respect to butterflies (s ...

of the family

Sphingidae The Sphingidae are a family of moths commonly called sphinx moths, also colloquially known as hawk moths, with many of their caterpillars known as hornworms. It includes about 1,450 species. It is best represented in the tropics, but species ar ...

present through much of the

Americas The Americas, sometimes collectively called America, are a landmass comprising the totality of North America and South America.''Webster's New World College Dictionary'', 2010 by Wiley Publishing, Inc., Cleveland, Ohio. When viewed as a sing ...

. The species was first described by

Carl Linnaeus Carl Linnaeus (23 May 1707 – 10 January 1778), also known after ennoblement in 1761 as Carl von Linné,#Blunt, Blunt (2004), p. 171. was a Swedish biologist and physician who formalised binomial nomenclature, the modern system of naming o ...

in his 1763 ''

Centuria Insectorum file:Centuria Insectorum.png, The first page of ''Centuria Insectorum'', as included in ''Amoenitates Academicæ'' ' (Latin, "one hundred insects") is a 1763 Taxonomy (biology), taxonomic work by Carl Linnaeus, and defended as a thesis by Boas Jo ...

''. Commonly known as the Carolina sphinx moth and the tobacco hawk moth (as adults) and the tobacco hornworm and the Goliath worm (as larvae), it is closely related to and often confused with the very similar tomato hornworm (''Manduca quinquemaculata''); the

larva A larva (; : larvae ) is a distinct juvenile form many animals undergo before metamorphosis into their next life stage. Animals with indirect development such as insects, some arachnids, amphibians, or cnidarians typically have a larval phase ...

e of both feed on the foliage of various plants of the family

Solanaceae Solanaceae (), commonly known as the nightshades, is a family of flowering plants in the order Solanales. It contains approximately 2,700 species, several of which are used as agricultural crops, medicinal plants, and ornamental plants. Many me ...

. The larvae of these species can be distinguished by their lateral markings: Tomato hornworms have eight V-shaped white markings with no borders; tobacco hornworms have seven white diagonal lines with a black border. Additionally, tobacco hornworms have red horns, while tomato hornworms have dark blue or black horns. A

mnemonic A mnemonic device ( ), memory trick or memory device is any learning technique that aids information retention or retrieval in the human memory, often by associating the information with something that is easier to remember. It makes use of e ...

to remember the markings is tobacco hornworms have straight white lines like cigarettes, while tomato hornworms have V-shaped markings (as in "vine-ripened" tomatoes). ''M. sexta'' has mechanisms for selectively sequestering and secreting the

neurotoxin Neurotoxins are toxins that are destructive to nervous tissue, nerve tissue (causing neurotoxicity). Neurotoxins are an extensive class of exogenous chemical neurological insult (medical), insultsSpencer 2000 that can adversely affect function ...

nicotine Nicotine is a natural product, naturally produced alkaloid in the nightshade family of plants (most predominantly in tobacco and ''Duboisia hopwoodii'') and is widely used recreational drug use, recreationally as a stimulant and anxiolytic. As ...

present in tobacco. ''M. sexta'' is a common

model organism A model organism is a non-human species that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the model organism will provide insight into the workings of other organisms. Mo ...

, especially in

neurobiology Neuroscience is the scientific study of the nervous system (the brain, spinal cord, and peripheral nervous system), its functions, and its disorders. It is a multidisciplinary science that combines physiology, anatomy, molecular biology, ...

, due to its easily accessible

nervous system In biology, the nervous system is the complex system, highly complex part of an animal that coordinates its behavior, actions and sense, sensory information by transmitting action potential, signals to and from different parts of its body. Th ...

and short life cycle. Due to its immense size ''M. sexta'' is big enough for medical imaging modalities (like CT,

MRI Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to generate pictures of the anatomy and the physiological processes inside the body. MRI scanners use strong magnetic fields, magnetic field gradients, and rad ...

, or

PET A pet, or companion animal, is an animal kept primarily for a person's company or entertainment rather than as a working animal, livestock, or a laboratory animal. Popular pets are often considered to have attractive/ cute appearances, inte ...

) and used as a model in imaging and gut inflammation. It is used in a variety of biomedical and biological scientific experiments. It can be easily raised on a wheat-germ-based diet. The larva is large, and thus it is relatively easy to dissect it and isolate its organs.

Life cycle

''M. sexta'' has a short life cycle, lasting about 30 to 50 days. In most areas, ''M. sexta'' has about two generations per year, but can have three or four generations per year in Florida.

Eggs

''M. sexta'' eggs are spherical, approximately 1.5 millimeters in diameter, and translucent green. They typically hatch two to four days after they are laid. Eggs are normally found on the underside of foliage, but can also be found on the upper surface.

Larva

''M. sexta'' larvae are bright green in color and grow up to 100 millimeters in length. The posterior

abdominal The abdomen (colloquially called the gut, belly, tummy, midriff, tucky, or stomach) is the front part of the torso between the thorax (chest) and pelvis in humans and in other vertebrates. The area occupied by the abdomen is called the abdominal ...

segment is tipped with a dorsocaudal horn that earns them the name "hornworm". The final

instar An instar (, from the Latin '' īnstar'' 'form, likeness') is a developmental stage of arthropods, such as insects, which occurs between each moult (''ecdysis'') until sexual maturity is reached. Arthropods must shed the exoskeleton in order to ...

consists of a cylindrical body covered with fine hairlike

seta In biology, setae (; seta ; ) are any of a number of different bristle- or hair-like structures on living organisms. Animal setae Protostomes Depending partly on their form and function, protostome setae may be called macrotrichia, chaetae, ...

e. The head is equipped with a pair of

ocelli A simple eye or ocellus (sometimes called a pigment pit) is a form of eye or an optical arrangement which has a single lens without the sort of elaborate retina that occurs in most vertebrates. These eyes are called "simple" to distinguish the ...

and chewing mouthparts. Each of the three

thoracic The thorax (: thoraces or thoraxes) or chest is a part of the anatomy of mammals and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main ...

segments bears a pair of true legs, and there is a pair of

proleg A proleg is a small, fleshy, stub structure found on the ventral surface of the abdomen of most larval forms of insects of the Order (biology), order Lepidoptera, though they can also be found on larvae of insects such as symphyta, sawflies. In ...

s on the third, fourth, fifth, sixth, and last abdominal segments in all larval instars. The prothoracic segment bears one pair of spiracles, and additional pairs occur on each of the eight abdominal segments. The

hemolymph Hemolymph, or haemolymph, is a fluid, similar to the blood in invertebrates, that circulates in the inside of the arthropod's body, remaining in direct contact with the animal's tissues. It is composed of a fluid plasma in which hemolymph c ...

(blood) of this species contains insecticyanin, a blue-colored biliprotein. When the larva feeds on its normal diet of plant foliage, it ingests pigmentacious

carotenoid Carotenoids () are yellow, orange, and red organic pigments that are produced by plants and algae, as well as several bacteria, archaea, and fungi. Carotenoids give the characteristic color to pumpkins, carrots, parsnips, corn, tomatoes, cana ...

s, which are primarily yellow in hue. The resulting combination is green. Under laboratory conditions—when fed a wheat-germ-based diet—larvae are turquoise in color due to the lack of carotenoids in their diet. The

caterpillar Caterpillars ( ) are the larval stage of members of the order Lepidoptera (the insect order comprising butterflies and moths). As with most common names, the application of the word is arbitrary, since the larvae of sawflies (suborder ...

stage of the tobacco hornworm is quite similar in appearance to that of the closely related tomato hornworm. The larvae of these two species can however be readily distinguished by their lateral markings. Specifically, the ''M. sexta'' caterpillar has seven white diagonal lines with a black border at the first seven abdominal segments, and the horn is red or green with a red tip. The ''M. quinquemaculata''caterpillar has V-shaped white markings with no borders at all eight of its abdominal segments, and the horn is dark blue or black in color. During the larval stage, ''M. sexta'' caterpillars feed on plants of the family

, principally tobacco, tomatoes and members of the genus ''

Datura ''Datura'' is a genus of nine species of highly poisonous, Vespertine (biology), vespertine-flowering plants belonging to the nightshade family (Solanaceae). They are commonly known as thornapples or jimsonweeds, but are also known as devil's t ...

''. ''M. sexta'' has five larval instars, which are separated by

ecdysis Ecdysis is the moulting of the cuticle in many invertebrates of the clade Ecdysozoa. Since the cuticle of these animals typically forms a largely inelastic exoskeleton, it is shed during growth and a new, larger covering is formed. The remnant ...

(molting), but may add larval instars when nutrient conditions are poor. Near the end of this stage, the caterpillar seeks a location for

pupa A pupa (; : pupae) is the life stage of some insects undergoing transformation between immature and mature stages. Insects that go through a pupal stage are holometabolous: they go through four distinct stages in their life cycle, the stages th ...

tion, burrows underground, and pupates. This searching behavior is known as "wandering". The imminence of pupation—suggested behaviorally by the wandering—can be anatomically confirmed by spotting the

heart The heart is a muscular Organ (biology), organ found in humans and other animals. This organ pumps blood through the blood vessels. The heart and blood vessels together make the circulatory system. The pumped blood carries oxygen and nutrie ...

(aorta), which is a long, pulsating vessel running along the length of the caterpillar's dorsal side. The heart becomes visible through the skin just as the caterpillar is reaching the end of the final instar. A common

biological control Biological control or biocontrol is a method of controlling pests, whether pest animals such as insects and mites, weeds, or pathogens affecting animals or plants by using other organisms. It relies on predation, parasitism, herbivory, or o ...

for hornworms is the

parasitic Parasitism is a close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The ent ...

braconid wasp The Braconidae are a family of parasitoid wasps. After the closely related Ichneumonidae, braconids make up the second-largest family in the order Hymenoptera, with about 17,000 recognized species and many thousands more undescribed. One analysis ...

'' Cotesia congregata'', which lays its eggs in the bodies of the hornworms. The wasp larvae feed internally and emerge from the body to spin their cocoons. Parasitized hornworms are often seen covered with multiple white, cottony wasp cocoons, which are often mistaken for large eggs. A

wasp A wasp is any insect of the narrow-waisted suborder Apocrita of the order Hymenoptera which is neither a bee nor an ant; this excludes the broad-waisted sawflies (Symphyta), which look somewhat like wasps, but are in a separate suborder ...

species, '' Polistes erythrocephalus,'' feeds on hornworm larvae. Manduca sexta droppings

Tobacco Hornworm 1.jpg Manduca sexta larval stage.jpeg, In the larval state its back end might be confused as its head. Tobacco Hornworm 1 by Max Wahrhaftig.jpg, With parasitic wasp cocoons Manduca Pupae.jpg, Pupa

Pre-pupa

Before the larva pupates, it goes through a stage called the pre-pupa, where it shrinks considerably and prepares to pupate. Often people mistake this stage for a dead or dying caterpillar.

Pupa

The pupal stage lasts approximately 14–18 days under laboratory conditions (17 hours light, 7 hours dark, 27 °C). When reared on a short-day photoperiod (12 hours light, 12 hours dark), pupae enter a state of

diapause In animal dormancy, diapause is the delay in development in response to regular and recurring periods of adverse environmental conditions.Tauber, M.J., Tauber, C.A., Masaki, S. (1986) ''Seasonal Adaptations of Insects''. Oxford University Press It ...

that can last several months. During the pupal stage, structures of the adult moth form within the pupal case, which is shed during

eclosion A pupa (; : pupae) is the life stage of some insects undergoing transformation between immature and mature stages. Insects that go through a pupal stage are holometabolous: they go through four distinct stages in their life cycle, the stages th ...

(adult emergence).

Adult

Adult ''M. sexta'' have narrow wings with a wing span of approximately 100 mm. ''M. sexta'' moths are nectarivorous and feed on flowers, demonstrating a remarkable ability to hover. Adults are

sexually dimorphic Sexual dimorphism is the condition where sexes of the same species exhibit different Morphology (biology), morphological characteristics, including characteristics not directly involved in reproduction. The condition occurs in most dioecy, di ...

. Males are identifiable by their broader antennae and the presence of claspers at the end of the abdomen. Female moths are typically ready to mate one week after

, and do so only once. Males may mate many times. Mating generally occurs on a vertical surface at night, and can last several hours, with the male and female facing in opposite positions, their posterior ends touching. After mating, females deposit their fertilized eggs on foliage, usually on the underside of leaves. Manduca sexta MHNT CUT 2010 0 104 Caranavi, La Paz Bolivia male dorsal.jpg, Male Manduca sexta MHNT CUT 2010 0 104 Caranavi, La Paz Bolivia male ventral.jpg, Male underside Manduca sexta MHNT CUT 2010 0 104 Dos Amates Catemaco VeraCruz Mexico female dorsal.jpg, Female Manduca sexta MHNT CUT 2010 0 104 Dos Amates Catemaco VeraCruz Mexico female ventral.jpg, Female underside

Laboratory rearing

Like ''

Drosophila melanogaster ''Drosophila melanogaster'' is a species of fly (an insect of the Order (biology), order Diptera) in the family Drosophilidae. The species is often referred to as the fruit fly or lesser fruit fly, or less commonly the "vinegar fly", "pomace fly" ...

'', ''M. sexta'' is commonly used as a

for experiments. They are frequently studied in the laboratory due to their large size and relative ease of rearing. They may be reared on host plants, such as tobacco and tobacco relatives, tomato plants, or wheat-germ-based artificial diet. Their rearing is straightforward, provided they receive a long daylight cycle (e.g., 14 hours) during development to prevent

. Eggs are rinsed for one to five minutes in dilute household bleach for disinfection. Eggs are placed on diet cubes or host plants. The eggs hatch and develop at different speeds depending on temperature. The larvae are moved to a fresh diet or leaves as their food spoils or is consumed. When they start to "wander", they are about to pupate, so are placed in a pupation chamber. Pupation chambers are holes drilled into a wood board. The ''Manduca'' larvae are sealed in the chamber using a stopper and allowed to pupate. After pupation, the pupae are placed in a breeding or colony chamber to eclose. Providing a cup of sugar water and a tobacco (or related) plant will allow mated females to oviposit fertile eggs, which can then be reared. When fed an artificial diet, ''Manduca'' larvae do not consume the

xanthophyll Xanthophylls (originally phylloxanthins) are yellow pigments that occur widely in nature and form one of two major divisions of the carotenoid group; the other division is formed by the carotenes. The name is from Greek: (), meaning "yellow", an ...

-which is a yellow pigment- needed to produce their green coloration; instead they appear blue. On some diets, they have very little pigment and pigment precursors, so are a very pale blue-white. As vitamin A and other

s are necessary for the visual pigments (

rhodopsin Rhodopsin, also known as visual purple, is a protein encoded by the ''RHO'' gene and a G-protein-coupled receptor (GPCR). It is a light-sensitive receptor protein that triggers visual phototransduction in rod cells. Rhodopsin mediates dim ...

), an artificial-diet-reared hornworm may have poor vision due to lack of carotenoids in the diet.

As pet food

Captive-bred hornworms fed on an artificial diet are often given to insectivorous exotic animals, such as certain reptiles, fish and small mammals. They are preferred over wild-collected hornworms, which may bioaccumulate poisonous substances found in dietary plants. Hornworms, though originally bred for laboratories, are also farmed for this purpose. They are often sold already packed into pods that include everything the larvae need, including food. Care is relatively easy, and animals seem to relish their bright color and flavor.

Animal model

''M. sexta'' larvae grow up to 100 millimeters in length, reaching up to 20 grams. Due to their large size, they are used as alternative animal models for medical imaging modalities like

computed tomography A computed tomography scan (CT scan), formerly called computed axial tomography scan (CAT scan), is a medical imaging technique used to obtain detailed internal images of the body. The personnel that perform CT scans are called radiographers or ...

magnetic resonance imaging Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to generate pictures of the anatomy and the physiological processes inside the body. MRI scanners use strong magnetic fields, magnetic field gradients, and ...

, or

positron emission tomography Positron emission tomography (PET) is a functional imaging technique that uses radioactive substances known as radiotracers to visualize and measure changes in metabolic processes, and in other physiological activities including blood flow, r ...

. Researchers around Anton Windfelder have established the larvae of ''M. sexta'' as an alternative

animal model An animal model (short for animal disease model) is a living, non-human, often genetic-engineered animal used during the research and investigation of human disease, for the purpose of better understanding the disease process without the risk of ha ...

for chronic inflammatory bowel diseases or as an animal model for testing new

contrast agent A contrast agent (or contrast medium) is a substance used to increase the contrast of structures or fluids within the body in medical imaging. Contrast agents absorb or alter external electromagnetism or ultrasound, which is different from radiop ...

s for

radiology Radiology ( ) is the medical specialty that uses medical imaging to diagnose diseases and guide treatment within the bodies of humans and other animals. It began with radiography (which is why its name has a root referring to radiation), but tod ...

Subspecies

*''Manduca sexta sexta'' (North and Central America) *''M. s. caestri'' (Blanchard, 1854) (Chile) *''M. s. jamaicensis'' (Butler, 1875) (Caribbean) *''M. s. leucoptera'' (Rothschild & Jordan, 1903) (Galápagos Islands) *''M. s. paphus'' (Cramer, 1779) (South America) *''M. s. saliensis'' (Kernbach, 1964) (Argentina) *''M. s. garapa'' (Pixley, 2016) (Saipan) Manduca sexta jamaicensis MHNT CUT 2010 0 366 Montvert Martinique France male dorsal.jpg, ''Manduca sexta jamaicensis''
Male dorsal Manduca sexta jamaicensis MHNT CUT 2010 0 366 Montvert Martinique France male ventral.jpg, ''Manduca sexta jamaicensis''
Male ventral Manduca sexta jamaicensis MHNT CUT 2010 0 366 Montvert Martinique France female dorsal.jpg, ''Manduca sexta jamaicensis''
Female dorsal Manduca sexta jamaicensis MHNT CUT 2010 0 366 Montvert Martinique France female ventral.jpg, ''Manduca sexta jamaicensis''
Female ventral Manduca sexta leucoptera MHNT CUT 2010 0 366 Galapagos Isla Santa Cruz (AcademyBay) female dorsal.jpg, ''Manduca sexta leucoptera''
Female dorsal Manduca sexta leucoptera MHNT CUT 2010 0 366 Galapagos Isla Santa Cruz (AcademyBay) female dorsal.jpg, ''Manduca sexta leucoptera''
Female ventral Manduca sexta paphus MHNT CUT 2010 0 366 Planaltino Bahia Brazil male dorsal.jpg, ''Manduca sexta paphus''
Male dorsal Manduca sexta paphus MHNT CUT 2010 0 366 Planaltino Bahia Brazil male ventral.jpg, ''Manduca sexta paphus''
Male ventral

Behavior

Feeding

Tobacco hornworms are facultative specialists; the larvae can grow and develop on any host plants. However, the larvae prefer solanaceous plants, such as tobacco and tomato plants. On these types of plants, larvae grow and develop faster. The lateral and medial sensilla styloconia (sensory receptors) on their mouthparts help them to identify solanaceous plants by recognizing indioside D, a steroidal glycoside found in those particular plants (del Campo et al., 2001).

Salicin Salicin is an alcoholic β-glucoside. Salicin is produced in (and named after) willow (''Salix'') bark. It is a biosynthetic precursor to salicylaldehyde. Salicin hydrolyses into Glucose, β-d-glucose and salicyl alcohol (saligenin). Salicyl al ...

is a distasteful phagodeterrent, found only in ''

Salix Willows, also called sallows and osiers, of the genus ''Salix'', comprise around 350 species (plus numerous hybrids) of typically deciduous trees and shrubs, found primarily on moist soils in cold and temperate regions. Most species are known ...

'' spp. while

caffeine Caffeine is a central nervous system (CNS) stimulant of the methylxanthine chemical classification, class and is the most commonly consumed Psychoactive drug, psychoactive substance globally. It is mainly used for its eugeroic (wakefulness pr ...

is a phagodeterrent that is actually toxic. Schoonhoven 1969 found that ''M. sexta''

habituation Habituation is a form of non-associative learning in which an organism’s non-reinforced response to an inconsequential stimulus decreases after repeated or prolonged presentations of that stimulus. For example, organisms may habituate to re ...

to salicin is mediated by desensitization of the deterrence associated peripheral neurons and Glendinning et al. 1999 the same for caffeine. However Glendinning et al. 2001 find only a small peripheral desensitization for salicin, concluding that Schoonhoven erred, and that habituation in this case is centrally mediated. Tobacco hornworms are considered pests because they feed on the upper leaves of tobacco plants and leave green or black droppings on the plants. As adults, they do not damage plants since they feed on nectar. Tobacco hornworm larvae prefer humid environments. When dehydrated, tobacco hornworm larvae will move towards a source of water or to an area with a high relative level of humidity. They use their antennae to locate water to drink .

Defense

Nicotine is poisonous to most animals that use muscles to move because nicotine targets the

acetylcholine receptor An acetylcholine receptor (abbreviated AChR) or a cholinergic receptor is an integral membrane protein that responds to the binding of acetylcholine, a neurotransmitter. Classification Like other transmembrane receptors, acetylcholine receptor ...

at the

neuromuscular junction A neuromuscular junction (or myoneural junction) is a chemical synapse between a motor neuron and a muscle fiber. It allows the motor neuron to transmit a signal to the muscle fiber, causing muscle contraction. Muscles require innervation to ...

. However, the tobacco hornworm is capable of metabolizing nicotine from the tobacco plant and using nicotine as a defense against predators. It possesses a gene called cytochrome P450 6B46 (CYP6B46) that converts nicotine into a metabolite. About 0.65% of nicotine metabolites are transported from the gut to the

, where they are reconverted to nicotine and released into the air from the tobacco hornworm's spiracles. The emitted nicotine is used as a way to deter spiders, a practice known as “toxic halitosis.” In one study, tobacco hornworms that fed from nicotine-deficient plants or expressed low levels of CYP6B46 were more susceptible to wolf spider predation. Tobacco hornworm caterpillars emit short clicking sounds from their mandibles when they are being attacked. This sound production is believed to be a type of acoustic

aposematism Aposematism is the Advertising in biology, advertising by an animal, whether terrestrial or marine, to potential predation, predators that it is not worth attacking or eating. This unprofitability may consist of any defenses which make the pr ...

, or warning sounds that let predators know that trying to eat them will be troublesome; tobacco hornworms have been observed to thrash and bite predators after producing those clicking sounds. These clicks can be heard at a close distance with a frequency range of 5 to 50 kHz. The intensity of clicks increases with the number of attacks (Bura et al., 2012).

Gallery

File:Britishentomologyvolume5Plate195.jpg, Illustration from John Curtis's '' British Entomology'' Volume 5, possibly the only British record for this species File:Manduca sexta on tomato.JPG, Feeding on tomato plant File:Tobacco Hornworm Parasitized by Braconid Wasp.jpg, ''Manduca sexta'' parasitized by '' Cotesia congregata'' wasp larvae File:Tobacco Hornworm with cocoons.jpg, A tobacco hornworm with wasp cocoons

References

External links

Fact sheet.
Colorado State University.
''Manduca sexta''.
Butterflies and Moths of North America.

Modelling insect wings using the finite element method''Manduca sexta'': A Model Organism for Imaging and Immunology
{{Taxonbar, from=Q1366539 S Moths of North America Moths of Central America Moths of the Caribbean Sphingidae of South America Animal models Animal models in neuroscience Agricultural pest insects Tomato diseases Pet foods Moths described in 1763 Taxa named by Carl Linnaeus