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An organismal perspective on C. intestinalis development, origins and diversification.

Kourakis MJ, Smith WC - Elife (2015)

Bottom Line: The ascidian Ciona intestinalis, commonly known as a 'sea squirt', has become an important model for embryological studies, offering a simple blueprint for chordate development.Moreover, recent phylogenies reveal that C. intestinalis occupies a privileged branch in the tree of life: it is our nearest invertebrate relative.Here, we provide an organismal perspective of C. intestinalis, highlighting aspects of its life history and habitat-from its brief journey as a larva to its radical metamorphosis into adult form-and relate these features to its utility as a laboratory model.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, United States.

ABSTRACT
The ascidian Ciona intestinalis, commonly known as a 'sea squirt', has become an important model for embryological studies, offering a simple blueprint for chordate development. As a model organism, it offers the following: a small, compact genome; a free swimming larva with only about 2600 cells; and an embryogenesis that unfolds according to a predictable program of cell division. Moreover, recent phylogenies reveal that C. intestinalis occupies a privileged branch in the tree of life: it is our nearest invertebrate relative. Here, we provide an organismal perspective of C. intestinalis, highlighting aspects of its life history and habitat-from its brief journey as a larva to its radical metamorphosis into adult form-and relate these features to its utility as a laboratory model.

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Ciona intestinalis, from swimming larva to filter-feeding adult.(A) During a brief larval phase, C. intestinalis (dorsal is top) finds and attaches to a substrate via its anterior adhesive palps (two of three are shown), where it initiates metamorphosis. The larva swims using a muscular tail, aided by the rigidity and stiffness of the notochord, a hollow tube within the tail. The pigmented brain organs, the ocellus and otolith, which sense light and gravity, help to guide the animal. (B) A C. intestinalis adult has two siphons, oral and atrial, positioned opposite the attachment point (arrowheads); the flow of water in and out is indicated (blue arrows). C. intestinalis are hermaphrodites, and here the egg and sperm ducts are visible; both sperm and eggs exit via the atrial siphon cavity. (C) Clusters of C. intestinalis attached to the underside of a kayak in Santa Barbara, California. These marine invaders often line vessel hulls and crowd submerged ropes, buoys and other surfaces. (D) A confocal projection of the brain and spinal cord of C. intestinalis near hatching stage; anterior is right. C. intestinalis is ideal for imaging and, unlike its larger chordate cousins, large portions of the animal can be imaged within a single field of view. Cell membranes are in green (etr>ArcLight) and nuclei in red (etr>RFP). Image credits: (A, B, D), M Kourakis; (C), S Abdul-Wajid.DOI:http://dx.doi.org/10.7554/eLife.06024.002
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fig1: Ciona intestinalis, from swimming larva to filter-feeding adult.(A) During a brief larval phase, C. intestinalis (dorsal is top) finds and attaches to a substrate via its anterior adhesive palps (two of three are shown), where it initiates metamorphosis. The larva swims using a muscular tail, aided by the rigidity and stiffness of the notochord, a hollow tube within the tail. The pigmented brain organs, the ocellus and otolith, which sense light and gravity, help to guide the animal. (B) A C. intestinalis adult has two siphons, oral and atrial, positioned opposite the attachment point (arrowheads); the flow of water in and out is indicated (blue arrows). C. intestinalis are hermaphrodites, and here the egg and sperm ducts are visible; both sperm and eggs exit via the atrial siphon cavity. (C) Clusters of C. intestinalis attached to the underside of a kayak in Santa Barbara, California. These marine invaders often line vessel hulls and crowd submerged ropes, buoys and other surfaces. (D) A confocal projection of the brain and spinal cord of C. intestinalis near hatching stage; anterior is right. C. intestinalis is ideal for imaging and, unlike its larger chordate cousins, large portions of the animal can be imaged within a single field of view. Cell membranes are in green (etr>ArcLight) and nuclei in red (etr>RFP). Image credits: (A, B, D), M Kourakis; (C), S Abdul-Wajid.DOI:http://dx.doi.org/10.7554/eLife.06024.002

Mentions: The tunicate (sea squirt) Ciona intestinalis spends its adult life anchored to a hard substrate, filter feeding and releasing gametes (eggs and sperm) into the surrounding sea water. For a fleeting day or two of its life, however, the larva of C. intestinalis adopts a tadpole morphology (Figure 1A). This morphology provides hints as to the origins of the chordates (see Box 1 for a glossary of specialist terms used in this article), including that of the most successful chordate clade, the vertebrates. In 1866, the Russian biologist Alexander Kowalevsky observed the ascidian tadpole and noted the presence of a dorsal nervous system and prominent notochord, two defining features of chordates (Kowalevsky, 1866). Prior to this, the chordate features of tunicates had not been described and, in fact, a century earlier the taxonomy of Carl Linnaeus placed C. intestinalis and other ascidians (see Glossary) within the molluscs, based on their adult form (Linné, 1767).10.7554/eLife.06024.002Figure 1.Ciona intestinalis, from swimming larva to filter-feeding adult.


An organismal perspective on C. intestinalis development, origins and diversification.

Kourakis MJ, Smith WC - Elife (2015)

Ciona intestinalis, from swimming larva to filter-feeding adult.(A) During a brief larval phase, C. intestinalis (dorsal is top) finds and attaches to a substrate via its anterior adhesive palps (two of three are shown), where it initiates metamorphosis. The larva swims using a muscular tail, aided by the rigidity and stiffness of the notochord, a hollow tube within the tail. The pigmented brain organs, the ocellus and otolith, which sense light and gravity, help to guide the animal. (B) A C. intestinalis adult has two siphons, oral and atrial, positioned opposite the attachment point (arrowheads); the flow of water in and out is indicated (blue arrows). C. intestinalis are hermaphrodites, and here the egg and sperm ducts are visible; both sperm and eggs exit via the atrial siphon cavity. (C) Clusters of C. intestinalis attached to the underside of a kayak in Santa Barbara, California. These marine invaders often line vessel hulls and crowd submerged ropes, buoys and other surfaces. (D) A confocal projection of the brain and spinal cord of C. intestinalis near hatching stage; anterior is right. C. intestinalis is ideal for imaging and, unlike its larger chordate cousins, large portions of the animal can be imaged within a single field of view. Cell membranes are in green (etr>ArcLight) and nuclei in red (etr>RFP). Image credits: (A, B, D), M Kourakis; (C), S Abdul-Wajid.DOI:http://dx.doi.org/10.7554/eLife.06024.002
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4373457&req=5

fig1: Ciona intestinalis, from swimming larva to filter-feeding adult.(A) During a brief larval phase, C. intestinalis (dorsal is top) finds and attaches to a substrate via its anterior adhesive palps (two of three are shown), where it initiates metamorphosis. The larva swims using a muscular tail, aided by the rigidity and stiffness of the notochord, a hollow tube within the tail. The pigmented brain organs, the ocellus and otolith, which sense light and gravity, help to guide the animal. (B) A C. intestinalis adult has two siphons, oral and atrial, positioned opposite the attachment point (arrowheads); the flow of water in and out is indicated (blue arrows). C. intestinalis are hermaphrodites, and here the egg and sperm ducts are visible; both sperm and eggs exit via the atrial siphon cavity. (C) Clusters of C. intestinalis attached to the underside of a kayak in Santa Barbara, California. These marine invaders often line vessel hulls and crowd submerged ropes, buoys and other surfaces. (D) A confocal projection of the brain and spinal cord of C. intestinalis near hatching stage; anterior is right. C. intestinalis is ideal for imaging and, unlike its larger chordate cousins, large portions of the animal can be imaged within a single field of view. Cell membranes are in green (etr>ArcLight) and nuclei in red (etr>RFP). Image credits: (A, B, D), M Kourakis; (C), S Abdul-Wajid.DOI:http://dx.doi.org/10.7554/eLife.06024.002
Mentions: The tunicate (sea squirt) Ciona intestinalis spends its adult life anchored to a hard substrate, filter feeding and releasing gametes (eggs and sperm) into the surrounding sea water. For a fleeting day or two of its life, however, the larva of C. intestinalis adopts a tadpole morphology (Figure 1A). This morphology provides hints as to the origins of the chordates (see Box 1 for a glossary of specialist terms used in this article), including that of the most successful chordate clade, the vertebrates. In 1866, the Russian biologist Alexander Kowalevsky observed the ascidian tadpole and noted the presence of a dorsal nervous system and prominent notochord, two defining features of chordates (Kowalevsky, 1866). Prior to this, the chordate features of tunicates had not been described and, in fact, a century earlier the taxonomy of Carl Linnaeus placed C. intestinalis and other ascidians (see Glossary) within the molluscs, based on their adult form (Linné, 1767).10.7554/eLife.06024.002Figure 1.Ciona intestinalis, from swimming larva to filter-feeding adult.

Bottom Line: The ascidian Ciona intestinalis, commonly known as a 'sea squirt', has become an important model for embryological studies, offering a simple blueprint for chordate development.Moreover, recent phylogenies reveal that C. intestinalis occupies a privileged branch in the tree of life: it is our nearest invertebrate relative.Here, we provide an organismal perspective of C. intestinalis, highlighting aspects of its life history and habitat-from its brief journey as a larva to its radical metamorphosis into adult form-and relate these features to its utility as a laboratory model.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, United States.

ABSTRACT
The ascidian Ciona intestinalis, commonly known as a 'sea squirt', has become an important model for embryological studies, offering a simple blueprint for chordate development. As a model organism, it offers the following: a small, compact genome; a free swimming larva with only about 2600 cells; and an embryogenesis that unfolds according to a predictable program of cell division. Moreover, recent phylogenies reveal that C. intestinalis occupies a privileged branch in the tree of life: it is our nearest invertebrate relative. Here, we provide an organismal perspective of C. intestinalis, highlighting aspects of its life history and habitat-from its brief journey as a larva to its radical metamorphosis into adult form-and relate these features to its utility as a laboratory model.

Show MeSH
Related in: MedlinePlus