Variation in the number of larval instars of the brownheaded leafroller,<i>Ctenopseustis obliquana</i>(Lepidoptera: Tortricidae) at constant laboratory temperatures

Clare, Graeme K.; Singh, Pritam

doi:10.1080/03014223.1990.10422590

Cited by 8 publications

(5 citation statements)

References 5 publications

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“…The number of juvenile instars varies with the environment in many arthropods, including spiders (Deevey, 1949), locusts (Uvarov, 1966), lepidopterans (Clare & Singh, 1991) and decapods (Hartnoll, 1985).…”

Section: Discussionmentioning

confidence: 99%

Genetics of life history in Daphnia magna. I. Heritabilities at two food levels

Ebert

Yampolsky

Stearns³

1993

Heredity

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Broad-and narrow-sense heritabilities for several life-history traits were estimated from 23 mother-daughter pairs of Daphnia magna at two food levels. Sexually produced daughter clones were obtained from a field collection of ephippial females (mothers) and the subsequent hatching of their ephippial eggs (daughters). Mother and daughter clones were maintained by parthenogenetic reproduction. Heritabilities of adult body-length of eight successive instars were the highest estimates of all in good food, but the lowest of all in poor food. For clutch size and body-length of offspring from the first six clutches, narrow-and broad-sense heritabilities were about equal and lower in poor food than in good food. The amount of genetic variation present would allow a response to selection on clutch size and offspring length in both environments but adult length only in good food. For age at maturity we found no additive genetic variance. We found no difference in broad-sense heritabilities between mother clones, representing the last generation after a period of asexual reproduction, and their sexually produced offspring. This suggests that genetic variance does not increase after one sexual generation or that it was not reduced before. Differences in heritabilities between environments are discussed with reference to the enlarged phenotypic variances that result from variation in juvenile instar number. Targeted growth could explain the pronounced differences in the heritabilities of adult length between environments.

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Section: Discussionmentioning

confidence: 99%

Genetics of life history in Daphnia magna. I. Heritabilities at two food levels

Ebert

Yampolsky

Stearns³

1993

Heredity

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“…Possibly, it is the number of instars rather than body size as such that is the proper variable to be studied in the adaptionistic context in at least some insects. In contrast to a fixed number of instars in Epirrita, there are reports on plasticity in instar number in some other Lepidoptera (Nijhout, 1975;Schmidt & Lauer, 1977;Tauber et al, 1986;Clare & Singh, 1990). Perhaps the best known example is the gypsy moth (Lymantria dispar L.), where females have six larval instars but males have five.…”

Section: The Role Of Larval Instars: Locating the Constraintsmentioning

confidence: 99%

Determination of adult size in a folivorous moth: constraints at instar level?

Tammaru

1998

Ecological Entomology

111

150

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1. Reaction norms for size and age at maturity were studied in Epirrita autumnata (Lepidoptera, Geometridae). Growth rates were manipulated by rearing larvae on different levels of food quality and quantity, and instar‐specific final weights and development times were recorded. 2. Food level and initial weight of an instar accounted for most of the variance in final weights. Sexual dimorphism in pupal weights could be entirely ascribed to sex differences in initial weights of the last instar. 3. There were problems with considering the reaction norms optimal within the conventional demographic explanatory framework. Because fecundity increases linearly with body size and no costs of large adult size are known, one should expect female larvae to grow larger to increase their individual fitness. It is therefore likely that constraints play a major role in the determination, and evolution, of size in this species. 4. A focus on individual instars may be the best way to reveal the constraints on, and space for, adaptive evolution of insect growth. Some limit to the initial:final weight ratio of an instar, and the fixed number of instars, may represent important constraints. 5. Reaction norms like the ones described in this study lead to strong environmental determination rather than canalization of body size. Food quality throughout larval development may thus be very important for individual fitness and population dynamics in E. autumnata.

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“…As in other arthropods, the growth of lepidopteran larvae is discontinuous and retarded by moults between instars. There may be remarkable intraspecific variation in the number of instars that may depend on, for example, sex, morph or population, and may be controlled by environmental conditions such as temperature, day length and nutritional quality of diet (Daly, 1985; Sehnal, 1985; Wipking, 1988; Clare & Singh, 1990; Gadenne et al., 1997; Esperk et al., 2007a,b; see also Reavey & Lawton, 1991). As moulting from one instar to another incurs time cost and increases predation risk during moulting, the optimal growth strategy of larvae should minimize the number of instars (Hutchinson et al., 1997).…”

Section: Introductionmentioning

confidence: 99%

To grow fast or to grow big? Time‐limited larvae of Eilema depressum speed up their growth and reduce number of instars

Pöykkö¹,

Hyvärinen²

2012

Entomologia Exp Applicata

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According to life‐history theory, longer development time may result in bigger adults. However, reaction norms describing age and size at maturity often follow an L‐shaped form. This relationship is attributable to the simple notion that slowly growing individuals may not lengthen their development excessively after the maturation decision has been made, for example, when development is time limited in seasonal environments. In arthropods, growth occurs within instars, and thus the optimal growth strategy might be mediated by the phenotypic adjustment of instar numbers. We studied the relationship between age and size at maturity of a lichen‐feeding moth, Eilema depressum (Esper) (Lepidoptera: Arctiidae: Lithosiinae), and the variability of instar numbers in relation to achieved adult body mass and time used for maturation. A positive relationship between age and size at maturity was found across developmental pathways and a negative one within the developmental pathways. Directly developing larvae had higher growth rates, attained smaller pupal mass, and passed fewer instars than larvae maturing after overwintering. Host quality did not affect whether larvae matured during the remaining or the next season. High variation in the number of instars together with variable growth rates indicates high plasticity in adaptation to varying environmental conditions. Our results also confirm previous results that instar number variability may be a key characteristic mediating age and size at maturity in insects.

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Variation in the number of larval instars of the brownheaded leafroller,Ctenopseustis obliquana(Lepidoptera: Tortricidae) at constant laboratory temperatures

Cited by 8 publications

References 5 publications

Genetics of life history in Daphnia magna. I. Heritabilities at two food levels

Genetics of life history in Daphnia magna. I. Heritabilities at two food levels

Determination of adult size in a folivorous moth: constraints at instar level?

To grow fast or to grow big? Time‐limited larvae of Eilema depressum speed up their growth and reduce number of instars

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