Cyclic AMP concentration and protein kinase A (PKA) gene expression at different developmental stages of the polychaete Hydroides elegans
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Abstract The phosphodiesterase inhibitor 3‐isobutyl‐1‐methylxanthine (IBMX) showed inductive effect on larval settlement of the polychaete Hydroides elegans . It has been suggested that IBMX triggers larval settlement by elevating the cellular adenosine 3′,5′‐cyclic monophosphate (cAMP) level in this species. To test this hypothesis, we first examined cAMP‐level changes in both the competent (CL) and attached larvae (AL) and then characterized the cAMP‐dependent protein kinase in H. elegans , which is the major mediator of cAMP action. Tissue extracts of the larvae were assayed for cAMP by enzyme immunoassay; the results showed that IBMX increased cAMP production up to approximately two‐folds in the CL. However, there was no significant difference in the cAMP concentration between the CL and AL that were not treated with IBMX. The catalytic subunit of protein kinase A gene from H. elegans (designated HePKAc ) was cloned, and its expression in different developmental stages of H. elegans was examined using quantitative real‐time polymerase chain reaction. The gene expression level in the pre‐competent trochophore larvae was the lowest, increased in the CL, reached the highest in the larvae undergoing normal and IBMX‐induced metamorphosis, and then decreased in the adult stage. In situ hybridization results showed that HePKAc expressed mainly around eye regions and along body fragments of the CL and AL. Our results indicated that the IBMX‐induced cAMP changes and the cAMP‐dependent protein kinase gene may mediate larval development and settlement of H. elegans . J. Exp. Zool. (Mol. Dev. Evol.) 310B:417–427, 2008 . © 2008 Wiley‐Liss, Inc.Keywords:
IBMX
Sponge
Developmental Biology
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There is a growing realization that events during one portion of an organism's life cycle can have both subtle and dramatic effects on other stages in the life history. Lethal and sublethal effects associated with the duration of larval swimming in marine invertebrates were examined for the bryozoan Bugula neritina. Larvae were kept swimming up to a maximum of 28 h at 20°C by exposure to continuous bright fluorescent illumination. At 4-h intervals, samples of 20-40 larvae were removed from bright illumination and were exposed to seawater containing 10 mM excess KCI, an inducer of metamorphosis in this species. Over the first 12 h of larval swimming, an average of about 90% of the larvae initiated and completed metamorphosis; at 16 h, the percentage of larvae initiating and completing metamorphosis dropped significantly. By 28 h, about half of the larvae were initiating metamorphosis, whereas only one-fifth were completing metamorphosis. Larval swimming duration also significantly affected the duration of metamorphosis. By 30 h of larval swimming, individuals were taking about 25% longer to complete metamorphosis. Compared to ancestrulae that developed from larvae that were induced to metamorphose shortly after the onset of swimming, those that swam for greater than 8 h had significantly smaller lophophores. For example, by 28 h of larval swimming the ancestrular lophophore decreased in height, surface area, and volume by about 25%, 40% and 55%, respectively. This marked decrease in lophophore size may ultimately affect the ability of juveniles to sequester food, compete for space, and attain reproductive maturity. Thus, increasing the duration of larval swimming affects both metamorphosis and the development of postlarval structures, which may ultimately influence colony fitness.
Bryozoa
Marine invertebrates
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The settlement and metamorphosis of the larval of Coelomactra antiquata treated with Ca2+ and K+.The results indicated that the hightest settlement and metamorphosis rates of was carried out.Component larval were observered in Ca2+ concentration of 20 mmol/L,the settlement rate was 86.1% and the metamorphosis rate was 42.8%.The hightest settlement and metamorphosis rates of component larval were observered in K+ concentrations of 10 mmol/L,the settlement rate was 83.7%,the metamorphosis rate was 33.5%.Ca2+ can induce the larval settlement and metamorphosis of Coelomactra antiquata more effectively than K+.
Settlement (finance)
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Metamorphosis is both an ecological and a developmental genetic transition that an organism undergoes as a normal part of ontogeny. Many organisms have the ability to delay metamorphosis when conditions are unsuitable. This strategy carries obvious benefits, but may also result in severe consequences for older larvae that run low on energy. In the marine environment, some lecithotrophic larvae that have prolonged periods in the plankton may begin forming postlarval and juvenile structures that normally do not appear until after settlement and the initiation of metamorphosis. This precocious activation of the postlarval developmental program may reflect an adaptation to increase the survival of older, energy-depleted larvae by allowing them to metamorphose more quickly. In the present study, we investigate morphological and genetic consequences of delay of metamorphosis in larvae of Herdmania momus (a solitary stolidobranch ascidian). We observe significant morphological and genetic changes during prolonged larval life, with older larvae displaying significant changes in RNA levels, precocious migration of mesenchyme cells, and changes in larval shape including shortening of the tail. While these observations suggest that the older H. momus larvae are functionally different from younger larvae and possibly becoming more predisposed to undergo metamorphosis, we did not find any significant differences in gene expression levels between postlarvae arising from larvae that metamorphosed as soon as they were competent and postlarvae developing from larvae that postponed metamorphosis. This recalibration, or convergence, of transcript levels in the early postlarva suggests that changes that occur during prolonged larval life of H. momus are not necessarily associated with early activation of adult organ differentiation. Instead, it suggests that an autonomous developmental program is activated in H. momus upon the induction of metamorphosis regardless of the history of the larva.
Marine larval ecology
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Growth, metamorphosis, and gape-limited cannibalism and predation 'On tadpoles (Rana pirica) in larvae of salamanders (Hynobius retardatus) were investigated in laboratory. Larval period and the size at metamorphosis were correlated positively to one another in the salamanders. When embryos were exposed to low temperature, larval period were prolonged and the size at metamorphosis increased in the salamanders while larval period were extended and the size at metamorphosis decreased in the frogs. Salamander larvae reared in group had shorter larval period and smaller size at metamorphosis than those reared individually. Small salamander larvae were more vulnerable to cannibalism and mutilation than large ones. Tadpoles incurred high probability of predation a\,ld mutilation by salamander larvae even when the head widths of tadpoles attained the maximum sizes.
Cannibalism
Tadpole (physics)
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Paracentrotus lividus
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The effects of 20-hydroxyecdysone (20-HE) on cyprid larval attachment and metamorphosis of the barnacle Balanus amphitrite were examined. When exposed to 10-100 μM 20-HE, cyprids failed to metamorphose, but attached to substrata. However, 0.001-0.1 μM 20-HE promoted attachment and metamorphosis. Moreover, effects of a combination of 20-HE and methyl farnesoate (MF) on cyprids were examined. The metamorphosis-inducing effect of MF was suppressed by pretreatment with 100 μM 20-HE. In contrast, after pretreatment with 10 μM MF, 100 μM 20-HE inhibited metamorphosis. High performance capillary electrophoresis (HPCE) revealed the presence of 20-HE in the extract from cyprid larvae of B. amphitrite, suggesting the intrinsic hormonal role of 20-HE in larval metamorphosis process.
Balanus
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Tadpole (physics)
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