Sea Squirt Development

Introduction

Sea squirt - ciona intestinalis

Ascidian hox expression

Sea squirts (ascidians, Ascidiacea) are filter feeding marine animals, primitive chordates, that exist in many shapes and sizes. They reproduce by either sexual or asexual (budding) and develop through a laval (tadpole) to an adult phase. Some species have transparent eggs and embryos simplifying developmental imaging.

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Some Recent Findings

Neurula rotation determines left-right asymmetry in ascidian tadpole larvae "Tadpole larvae of the ascidian Halocynthia roretzi show morphological left-right asymmetry. ... We suggest that chemical, and not mechanical, signals from the vitelline membrane promote nodal expression. Neurula rotation is also conserved in other ascidian species." Creating 3D digital replicas of ascidian embryos from stacks of confocal images. "During embryonic development, cell behaviors that are tightly coordinated both spatially and temporally integrate at the tissue level and drive embryonic morphogenesis. Over the past 20 years, advances in imaging techniques, in particular, the development of confocal imaging, have opened a new world in biology, not only giving us access to a wealth of information, but also creating new challenges. It is sometimes difficult to make the best use of the recordings of the complex, inherently three-dimensional (3D) processes we now can observe. In particular, these data are often not directly suitable for even simple but conceptually fundamental quantifications. This article describes a process whereby image stacks gathered from live or fixed ascidian embryos are digitalized and segmented to produce 3D embryo replicas. These replicas can then be interfaced via a 3D Virtual Embryo module to a model organism database (Aniseed) that allows one to relate the geometrical properties of cells and cell contacts to additional parameters such as cell lineage, cell fates, or the underlying genetic program. Such an integrated system can serve several general purposes. First, it makes it possible to quantify and better understand the dynamics of cell behaviors during embryonic development, including, for instance, the automatic detection of asymmetric cell divisions or the evolution of cell contacts. Second, the 3D Virtual Embryo software proposes a panel of mathematical shape descriptors to precisely quantify cellular geometries and generate a 3D identity card for each embryonic cell. Such reconstructions open the door to a detailed 3D simulation of morphogenesis."

Early Development

(b) Ciona intestinalis notochord

Neural

• ascidians lack a segmented hindbrain, but have restricted expression patterns of anterior Hox genes.

Historic

Manual of Human Embryology by Franz Keibel and Franklin P. Mall (1910).

"Conklin (1895) has been able to determine in ascidian eggs, even before cleavage begins, the existence of organ-forming substances, one of which, the myoplasm, that has to do with the formation of muscle tissue, is clearly recognizable and can be followed through successive stages of development into formed muscle."

References

Reviews

Patrick Lemaire Evolutionary crossroads in developmental biology: the tunicates. Development: 2011, 138(11);2143-52 PMID:21558365

Search Pubmed

Search Pubmed: Sea Squirt Development

External Links

External Links Notice - The dynamic nature of the internet may mean that some of these listed links may no longer function. If the link no longer works search the web with the link text or name.

• Ascidian Home Page for United States Ascidian News - Published twice a year since 1975.
• The Dutch Ascidians Homepage

Animal Development: Axolotl | Bat | Cat | Chicken | Cow | Dog | Dolphin | Echidna | Fly | Frog | Grasshopper | Guinea Pig | Hamster | Kangaroo | Koala | Lizard | Medaka | Mouse | Pig | Platypus | Rabbit | Rat | Sea Squirt | Sea Urchin | Sheep | Worm | Zebrafish | Life Cycles

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Dr Mark Hill 2013, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G