Cotesia congregata
Encyclopedia
Cotesia congregata is a parasitic wasp
of the genus Cotesia.
larva
e (2nd or 3rd instar [each instar is between moltings, i.e. the second instar
is the life stage after the first molt and before the second molting) and at the same time injects symbiotic viruses into the hemocoel of the host. The viruses knock down the internal defensive responses of the hornworm (Buron and Beckage, 1992; Beckage, 1997). The eggs hatch in the host hemocoel within two to three days and simultaneously release special cells from the egg chorion
(Buron and Beckage, 1997). These special cells, called teratocytes, grow to become giant cells visible to the naked eye. The function of teratocytes is not yet known but several roles have been hypothesized, such as inhibiting pupa
tion or being involved in the depression of the host’s defensive system (see in Buron and Beckage, 1997). Following hatching in the caterpillar, the wasp larvae will undergo 2 molts inside the host caterpillar’s hemocoel and, after 12 to 16 days post oviposition, the 3rd
instar wasp larvae will emerge out of the caterpillar and spin cocoons from which the adult wasps fly about 4 to 8 days later.
---From: http://72.14.253.104/search?q=cache:qR6zds5sMQsJ:www.zoo.utoronto.ca/able/volumes/vol-22/10-deburon.pdf+life+cycle+of+cotesia+congregata&hl=en&ct=clnk&cd=1&gl=us
C. congregata manipulates its host hemolymph ecdysteroid levels by interfering with the normal inhibitory mechanisms that prevent PTG (prothoracic gland) production and release of ecdysteroid at inappropriate periods of insect growth and development. However, the mechanism by which this action occurs is unknown. Perhaps, parasitoid-produced proteins are involved, because parasitoids have been observed to release proteins under both in vivo and in vitro conditions.
The PDVs of larval-larval parasitoids are known to interfere with host's development. The symptoms of this phenomenon include either the induction or suppression of metamorphic changes in the host, both of which are due to endocrine disruption. Particularly in Manduca sexta larvae that are infected by C. congregata, the endocrine effects become obvious in the host's last instar, when metamorphic symptoms are suppressed regardless of the size of the host caterpillar. The host's weight may exceed 5 g (the weight that normally triggers the onset of metamorphosis). Thus, any further life stage development in the host is arrested as a larva. It then lives for several days in a nonfeeding state before death occurs two to three weeks following egression of the wasps from the host. Nonparasitized fourth-instar M. sexta caterpillars that are injected with C. congregata PDV attain abnormally high weights (up to 18 g) as fifth instars and then die as premetamorphic larvae or larval-pupal intermediates, which suggests that their hemolymph JH levels remain high enough to suppress metamorphosis. In this system, venom is not required to induce endocrine disruption of the host.
Wasp
The term wasp is typically defined as any insect of the order Hymenoptera and suborder Apocrita that is neither a bee nor an ant. Almost every pest insect species has at least one wasp species that preys upon it or parasitizes it, making wasps critically important in natural control of their...
of the genus Cotesia.
Life cycle
Adult wasps lay their eggs in tobacco hornwormTobacco hornworm
Manduca sexta is a moth of the family Sphingidae present through much of the American continent. Commonly known as the tobacco hornworm, it is closely related to and often confused with the very similar tomato hornworm ; the larvae of both feed on the foliage of various plants from the family...
larva
Larva
A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...
e (2nd or 3rd instar [each instar is between moltings, i.e. the second instar
Instar
An instar is a developmental stage of arthropods, such as insects, between each molt , until sexual maturity is reached. Arthropods must shed the exoskeleton in order to grow or assume a new form. Differences between instars can often be seen in altered body proportions, colors, patterns, or...
is the life stage after the first molt and before the second molting) and at the same time injects symbiotic viruses into the hemocoel of the host. The viruses knock down the internal defensive responses of the hornworm (Buron and Beckage, 1992; Beckage, 1997). The eggs hatch in the host hemocoel within two to three days and simultaneously release special cells from the egg chorion
Chorion
The chorion is one of the membranes that exist during pregnancy between the developing fetus and mother. It is formed by extraembryonic mesoderm and the two layers of trophoblast and surrounds the embryo and other membranes...
(Buron and Beckage, 1997). These special cells, called teratocytes, grow to become giant cells visible to the naked eye. The function of teratocytes is not yet known but several roles have been hypothesized, such as inhibiting pupa
Pupa
A pupa is the life stage of some insects undergoing transformation. The pupal stage is found only in holometabolous insects, those that undergo a complete metamorphosis, going through four life stages; embryo, larva, pupa and imago...
tion or being involved in the depression of the host’s defensive system (see in Buron and Beckage, 1997). Following hatching in the caterpillar, the wasp larvae will undergo 2 molts inside the host caterpillar’s hemocoel and, after 12 to 16 days post oviposition, the 3rd
instar wasp larvae will emerge out of the caterpillar and spin cocoons from which the adult wasps fly about 4 to 8 days later.
---From: http://72.14.253.104/search?q=cache:qR6zds5sMQsJ:www.zoo.utoronto.ca/able/volumes/vol-22/10-deburon.pdf+life+cycle+of+cotesia+congregata&hl=en&ct=clnk&cd=1&gl=us
C. congregata manipulates its host hemolymph ecdysteroid levels by interfering with the normal inhibitory mechanisms that prevent PTG (prothoracic gland) production and release of ecdysteroid at inappropriate periods of insect growth and development. However, the mechanism by which this action occurs is unknown. Perhaps, parasitoid-produced proteins are involved, because parasitoids have been observed to release proteins under both in vivo and in vitro conditions.
The PDVs of larval-larval parasitoids are known to interfere with host's development. The symptoms of this phenomenon include either the induction or suppression of metamorphic changes in the host, both of which are due to endocrine disruption. Particularly in Manduca sexta larvae that are infected by C. congregata, the endocrine effects become obvious in the host's last instar, when metamorphic symptoms are suppressed regardless of the size of the host caterpillar. The host's weight may exceed 5 g (the weight that normally triggers the onset of metamorphosis). Thus, any further life stage development in the host is arrested as a larva. It then lives for several days in a nonfeeding state before death occurs two to three weeks following egression of the wasps from the host. Nonparasitized fourth-instar M. sexta caterpillars that are injected with C. congregata PDV attain abnormally high weights (up to 18 g) as fifth instars and then die as premetamorphic larvae or larval-pupal intermediates, which suggests that their hemolymph JH levels remain high enough to suppress metamorphosis. In this system, venom is not required to induce endocrine disruption of the host.