The effect of larval age on morphology and gene expression during ascidian metamorphosis

Jacobs, Molly, Degnan, Sandie M., Woods, Rick, Williams, Elizabeth, Roper, Kathrein E., Green, Kathryn and Degnan, Bernard M. (2006) The effect of larval age on morphology and gene expression during ascidian metamorphosis. Integrative and Comparative Biology, 46 6: 760-776. doi:10.1093/icb/icl015


Author Jacobs, Molly
Degnan, Sandie M.
Woods, Rick
Williams, Elizabeth
Roper, Kathrein E.
Green, Kathryn
Degnan, Bernard M.
Title The effect of larval age on morphology and gene expression during ascidian metamorphosis
Journal name Integrative and Comparative Biology   Check publisher's open access policy
ISSN 1540-7063
Publication date 2006-12-01
Sub-type Article (original research)
DOI 10.1093/icb/icl015
Volume 46
Issue 6
Start page 760
End page 776
Total pages 17
Place of publication New York
Publisher Society for Integrative and Comparative Biology
Language eng
Subject C1
270201 Gene Expression
770302 Living resources (incl. impacts of fishing on non-target species)
Abstract 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.
Keyword Gastropod Crepidula-fornicata
Marine-invertebrate Larvae
Hydroids-elegans-haswell
Egf-like Protein
Delayed Metamorphosis
Haliotis-rufescens
Ciona-intestinalis
Herdmania-momus
Competence
Growth
Q-Index Code C1
Additional Notes Not a 2007 publication.

 
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Created: Wed, 15 Aug 2007, 19:48:08 EST