Download REGRESSIVE MOLT

REGRESSIVE MOLT
By Alan Soffan
Regressive molt means a molting of a nymph that undergo a reduction of their
wings rudiments or lose their wing buds, thereby reverting back to the worker stage.
These workers then called as pseudergates (Roisin, 1990 and Suiter, 2002).
This phenomenon obtained indirectly relying upon these observation 1).
Nymph can go through a regressive molt and have their wing pads reduced, 2).
individuals taken from the field and resembling the regressed nymph obtained in the
laboratory can grow wing pads to acquire normal nymphs (Roisin, 1990 and Suiter,
2002).
Regressive molt also happened in laboratory when they are transferred from
large to small laboratory colonies at the wrong time, probably because of a lower
level nutrition, that subsequently influence the response of corpora allata also Juvenile
hormone (JH) produced (Fage, and Nutting, 1978).
Related to JH production, If JH titers is high it will associated with soldier
caste differentiation, but if JH titers low , it will associated with the changing from
nymph to alate. In regressive molt case, it is suggested that the termite suddenly
increase their JH titer, then this resultant of JH profile would mimic the pattern for a
stationary molt, thus inducing regressive molting into pseudergates (Cornette, et al.,
2008)
Some species of termites conduct this regressive molt, such as in
(dampwood termites),
Termopsidae
Kalotermes flavicollis and K. rufinotum, Neotermes papua, (Roisin,
1990; Korb and Katrantzis, 2004), Hodotermopsis sjostedti (Cornette, et al., 2008)
Reference
Cornette, Richard, Hiroki Gotoh, Shigeyuki Koshikawa, Toru Miura. 2008. Juvenile
hormone titers and caste differentiation in the damp-wood termite
Hodotermopsis sjostedti (Isoptera, Termopsidae).Journal of Insect
Physiology 54 (2008) 922– 930
Korb, Judith and Stephania Katrantzis.2004. Influence of environmental condition on
the expression of the sexual dispersal phenotype in a lower
termite:implications for the evolution of workers in termite. Evolution and
development 6:5, 342–352 (2004)
Suiter, Daniel R.,
Susan C. Jones and Brian T.Forschler.2002.Biology of
Subterranean termites in the Eastern United States. The University of
Georgia and The Ohio State Unviersity.
Fage, L.P. La and W.L. Nutting. 1978. Producition ecology of ants and termites.CUP
Archieve.409p
Roisin, Y. 1990. Reversibility of regressive molts in the termite Neotermes papua.
Naturwissenschaffen 77,246- 247 (1990) © Springer-Verlag 1990
By Arya Widyawan
Regressive molt is unique process which can be observed in termite. This
phenomena may be observed in the nymphal stage of termite. Nymphal termites that
undergoes regressive molt, lose their wing buds and thereby reverting back to the
worker stage. These workers are called pseudergates (Suiter et al. 2002). In some
species of termites such as N. papua, pseudergates may molt back to the wing padded
form and ultimetly develop into winged adult (Roisin 1990). Regressive molt is
happen because the reproductive castes secrete sex-specific pheromones that directly
inhibit the metamorphosis of immature individuals into reproductive form (Wilson
1971).
Regressive molt may take place when the environmental condition is poor. In
some species of insect, regressive molts may occur when larvae are deprived of food,
reared on the poor-quality diet or on the crowded situation. The tenebrionid beetle
Zophobas atratus (F.)may have an undetermined number of instars, and they are not
able to pupate when reared in crowded conditions. Although these larvae may achieve
body masses of twice of that of normal larvae, they often go through stationary and/or
regressive molts (Esperk et al. 2007).
Usually, stationary and regressive molt are involved in species that exhibit an
extremely high variability in the number of larval instars. Many of species that
important economically has variability in the number of instars. For example, instar
number is reported to be variable in such serious pest species such as Locusta
migratoria (L.), Schistocerca gregaria (Forskal), Tenebrio molitor (L.), Lymantria
dispar (L.), Pieris brassicae (L.), and Tineola biselliella (Hummel) (Esperk et al
2007).
In the histological point of view, Phenomena of regressive molt (loosing wing
bud) may be observed in female Eumeta variegate. According to histological study on
seventh, eight, and last larval instar of female E. variegate, the wings disc transform
into a plain, thick epidermis in the prepupal period. This transformation is due to the
hemopoietic organ (Niitsu, 2003).
References
ESPERK, T., T. TAMMARU and S. NYLIN. 2007. Intraspecific Variability in
Number of Larval Instars in Insects. Entomological Society of America (100): 627645
Niitsu, S. 2003. Postembryonic development of the wing imaginal discs in the
female wingless bagworm moth Eumeta variegata (Lepidoptera, Psychidae). J.
Morphol. (257):164-170
Roisin, Y. 1990. Reversibility of Regressive Molts in the Termite Neotermes papua .
Naturwissenschaffen (77): 246- 247.
Suiter, D.R. S.C. Jones., and B.T. Forschler. 2002. Biology of subterranean termite in
the eastern united states. University of Georgia.
By Boy Valenza Damiri
Regressive moult is a term for a type of postembryonic development in which
some of the imaginal parts of the body which develop during the larval / instar period,
such as the imaginal parts of wings, lose their ability for growth and are partly or
completely histolysed during the metamorphosis (Novak, 1966). Grasse and Noirot
(1947) in Richards and Davies (1977) found that regressive moults naturally occur in
isoptera to control caste differentation of pseudergates. In general speaking, termite
queen produces a pheromone that inhibit the differentation of pseudergates into
replacement reproductives. In the case of Pheidole sp, soldier termites produce a
pheromone that inhibits differentation of pseudergates into new soldiers (Luscher,
1972 in Wigglesworth, 1984 ; Miller, 1969 in Wigglesworth, 1984). The sensitive
period during which
pseudergates are most sensitive to the soldier inhibiting
pheromone occurs during the last part of the instar, while the sensitive period for the
induction of the supplementary reproductive caste is during the early portion of the
instar (Luscher, 1953 in Wigglesworth, 1984 ; Springhetti, 1972 in Wigglesworth,
1984).
Generally, the process of regressive moulting in termite has a correlation with
the inhibitory pheromones (which are described in the above paragraph) and with
Juvenile Hormone (JH) concentration in the pseudergates (Wigglesworth, 1984).
These inhibitory pheromones work by altering the pattern of JH secretion
(Wigglesworth, 1984). Nijhout and Wheeler (1982) have proposed a general model to
explain this process. They proposed that during the pseudergate instar, there are three
JH-sensitive periods (Nijhout and Wheeler, 1982 in Wigglesworth, 1984). The first
period controls the development of sexual characters, the second one controls the non
sexual characters (wings, pigmentation), and the third control characters typical of the
soldier (head, mandibles, pigmentation) (Nijhout and Wheeler, 1982 in Wigglesworth,
1984). The inhibitory pheromones will maintain the concentration of JH titer depend
on the need of the termite colony itself. A high JH titer during the first and second
period will inhibit imaginal determination (inhibiting to become adult) while during
the third JH-sensitive period a high JH titer serves to induce development of soldier
characteristics (Wigglesworth, 1984). To remain a pseudergate, JH titer has to be high
during the first two sensitive periods to inhibit imaginal determination and low during
the last one to prevent induction of soldier characters (Wigglesworth, 1984).
The correlation between JH and regressive moult can also be seen in Rhodnius
and Oncopeltus. If the adults is supplied with abundant JH, the new cuticle may show
a partial reversal of metamorphosis with partial development of larval characters
again (Wigglesworth, 1984). This phenomena also happens in earwigs, when is
induced to moult in the presence of JH, the ecdysal line of weakness in the dorsum of
the thorax re-appears, that show us a purely larval character (Wigglesworth, 1984).
Regressive moult also happens in wingless females of Geometridae (Order
Lepidoptera) where the imaginal discs grow until pupal period and almost reach the
size of the normal pupal wing before losing the ability for further growth and
becoming histolysed (Fedotov, 1955 in Novak, 1966). In Psychidae (Order
Lepidoptera), the regressive moult happens by the reduction of wings which start in
the first instar larva (Novak, 1966).
The environmental factors may also show the effect which is similar with
regressive molt phenomena. Pruthi (1924) found that Tenebrio larvae which were
exposured to high temperature (29-5°C) will result Tenebrio larvae with wing
rudiments (Wigglesworth, 1952).
References:
Novak, V. J. A. 1966. Insect hormones. Methuen and Co Ltd. London.□
Richards, O. W. and Davies, R. G. 1977. IMMS' General Textbook of Entomology.
Tenth Edition. Volume 2. Chapman and Hall. London.□
Wigglesworth, V. B. 1952. Hormone balance and the control of metamorphosis in
Rhodnius prolixus (hemiptera). Paper of Department of Zoology. University of
Cambridge.Δ
Wigglesworth, V. B. 1984. Insect Physiology. Springer Publisher.□
By Haris Setyaningrum
Regressive molt is the molting that happened in some insect, where result of
the molting l the individu revert to the stage before molt, some time reduce the wings
and morphometric size. Example of species that have regressive molt are some
species from termites, like Cryptotermes secundus Calotermes flavicollis,
Skatititermes and Speculitermes. Especially in case of worker molting. A worker can
molt twice (first to become a pre soldier ) to become soldier; the soldier cast is a
terminal caste. Workers that pass through the nymph stage can develop into winged
reproductive. Nymph have external wings buds as they progress toward the winged
adults stage, they gradually develop eyes, full size wings and functional reproductive
organ. Nymph undergo a regressive molt, lose their wings buds and revert to the
worker stage ( Korb, 2005; Robinson, 2005;Suiter, et.al. 2002). Regressive molt also
may influence by the food. Luscher (1960) had note that larvae of Calotermes
flavicollis develop into nymph in nature at about the time of swarming, when the
pseudergates have fewer mouths to feed and nutritional condition are probably good.
Conversely nymph undergo regressive molts if they are transferred from large to
small laboratory colonies at wrong time, probably because of a lower level nutrition.
He has reasoned that nutrition may in some way be responsible for activation or
inhibition of the corpora allata, and hence the juvenile hormone titer in which in turn,
determines the path of differentiation toward the next molt (Brian, 1978).
In this
species the regressive molt are reverisible, with some fact nymph can go through a
regressive molt and have their wings pads reduced and individual taken from the field
and resembling the regressed nymph obtained in the laboratory can grow wings pads
to acquire the appearance of normal nymphs (Roisin, 1990).
References :
Korb, Judith.2005. Termites . Current biology. Volume 17, Issue 23, 4 December
2007, Pages R995-R999.
Robinson, William H. 2005. Handbook of Urban Insects and Arachnids: A Handbook
of Urban Entomology. Cambridge University Press. Cambridge.
Brian, Michael Vaughan. 1978. Production Ecology of Ants and Termites. CUP
Archive press.
Suiter, Daniel R. et.al. May 2002. Biology of subterranean termites in the eastern
Unites states . the university of Georgia cooperative extension service Bulletin no
1209. University of Georgia.
Roisin, Y. 1990. Reversibility of regressive molts in termites Neotermes papua.
Naturwissenchaften 77, 246-247 (1990).