A food-independent maturation threshold and size at maturity in Daphnia magna

Ebert, Dieter

doi:10.4319/lo.1992.37.4.0878

Cited by 62 publications

(52 citation statements)

References 9 publications

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“…However, somatic growth of crustaceans, and thus the moulting cycle, are known to be affected by environmental conditions (e.g. food [23] and temperature [24]) and the reaction norms are different between genotypes [25]. In parallel, in the Daphnia -Pasteuria system, as in many others, environmental factors are known to affect infection outcomes differently according to the host genotype, the parasite genotype or their combination [26].…”

Section: Discussionmentioning

confidence: 99%

The role of moulting in parasite defence

Duneau

Ebert

2012

Proc. R. Soc. B.

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Parasitic infections consist of a succession of steps during which hosts and parasites interact in specific manners. At each step, hosts can use diverse defence mechanisms to counteract the parasite's attempts to invade and exploit them. Of these steps, the penetration of parasites into the host is a key step for a successful infection and the epithelium is the first line of host defence. The shedding of this protective layer (moulting) is a crucial feature in the life cycle of several invertebrate and vertebrate taxa, and is generally considered to make hosts vulnerable to parasites and predators. Here, we used the crustacean Daphnia magna to test whether moulting influences the likelihood of infection by the castrating bacterium Pasteuria ramosa. This parasite is known to attach to the host cuticula before penetrating into its body. We found that the likelihood of successful parasite infection is greatly reduced if the host moults within 12 h after parasite exposure. Thus, moulting is beneficial for the host being exposed to this parasite. We further show that exposure to the parasite does not induce hosts to moult earlier. We discuss the implications of our findings for host and parasite evolution and epidemiology.

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Section: Discussionmentioning

confidence: 99%

The role of moulting in parasite defence

Duneau

Ebert

2012

Proc. R. Soc. B.

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“…In contrast, offspring of inexperienced mothers matured later, delivered their first clutch approximately two days later than the other group, and had fewer offspring. Such a delayed maturation could arise either because of reductions in individual growth rates, and therefore time to reach the size threshold for reproduction (Ebert 1992), or because individuals exposed to toxins are often smaller than those from nontoxic environments (Nandini andRao 1998, Gustafsson andHansson 2004). Regardless of the precise mechanism, delays in maturity may leave individuals vulnerable to predation by other invertebrates (e.g., Chaoborus, Leptodora) that partly regulate overall secondary production.…”

Section: Discussionmentioning

confidence: 99%

“…In Daphnia, the production of eggs starts two instars before they are deposited in the brood chamber (Zaffagnini 1987), and is affected by both food quality and abundance (Ebert 1992), and possibly also by microcystin. Microcystin concentrations were quantified by taking a 1-mL sample from the C and M algal suspensions that were given to the experimental animals every second day.…”

Section: Methodsmentioning

confidence: 99%

Increased Consumer Fitness Following Transfer of Toxin Tolerance to Offspring via Maternal Effects

Gustafsson

Rengefors

Hansson

2005

Ecology

155

167

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Abstract. Adaptations and counteradaptations are common in coevolving predatorprey systems, but little is known of the role of maternal transfer of adaptive traits in mediating species interactions. Here, we focused on tolerance against cyanobacterial toxins and asked whether this tolerance was an induced defense developed during Daphnia's lifetime, whether it was a trait that is constantly expressed, and whether such tolerance to the toxin can be transferred to the next generation through maternal effects. These questions were addressed by feeding a single clone of Daphnia magna a diet with and without algal toxin and recording changes in fitness (as intrinsic rate of population increase). Analysis of F1, F2, and F3 generations revealed that the increased tolerance to toxic Microcystis was an inducible defense developed during an individual's lifetime, and that this trait could be transferred from mother to offspring. This maternal effect was expressed in several fitness parameters, including shorter time to maturity and first reproduction, and higher numbers of offspring compared to inexperienced individuals. In some circumstances, such maternal effects may increase population production by up to 40% and may help to stabilize material and energy transfer to higher trophic levels.

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“…However, each additional instar increases the variance strongly. This is the case for adult lengths and for age at maturity (Ebert, 1992).…”

Section: Discussionmentioning

confidence: 99%

“…The strong effect on variance components for age at maturity can be explained by the large effect of additional instars on this trait. Ebert (1992) showed that a threshold mechanism regulates length at maturity by increasing the number of juvenile instars. However, each additional instar increases the variance strongly.…”

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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A food-independent maturation threshold and size at maturity in Daphnia magna

Cited by 62 publications

References 9 publications

The role of moulting in parasite defence

The role of moulting in parasite defence

Increased Consumer Fitness Following Transfer of Toxin Tolerance to Offspring via Maternal Effects

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

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