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Intrinsic constraints on sympodial growth morphologies of azooxanthellate scleractinian coral Dendrophyllia.

Sentoku A, Ezaki Y - PLoS ONE (2013)

Bottom Line: However, little is known about the intrinsic mechanisms that control asexual reproduction and the resultant morphologies of colonies.The strict constraints on budding regularities and shifts in budding sites observed in the sympodial growth forms of corals greatly affect resulting morphologies in azooxanthellate coral colonies.A precise understanding of these intrinsic constraints leads to a fundamental comprehension of colony-forming mechanisms in modular organisms.

View Article: PubMed Central - PubMed

Affiliation: Department of Geosciences, Graduate School of Science, Osaka City University, Osaka, Japan. sentoku@sci.osaka-cu.ac.jp

ABSTRACT

Background: Asexual increase occurs in virtually all colonial organisms. However, little is known about the intrinsic mechanisms that control asexual reproduction and the resultant morphologies of colonies. Scleractinian corals, both symbiotic (zoaxanthellate) and non-symbiotic (azooxanthellate) corals are known to form elaborate colonies. To better understand the growth mechanisms that control species-specific type of colony in azooxanthellate dendrophyllid scleractinian corals, we have studied details of the budding pattern in the sympodial colonies of Dendrophyllia boschmai and Dendrophyllia cribrosa.

Principal findings: Budding exhibits the following regularities: (1) the two directive septa of offset corallites are oriented almost perpendicular to the growth direction of parent corallites; (2) offsets generally occur in either of the lateral primary septa that occur on one side of a corallite; the individuals thus show a definite polarity with respect to the directive septa, and only when branching dichotomously offsets occur in both primary septa; (3) the lateral corallites grow more-or-less diagonally upwards; and (4) the regularities and polarities are maintained throughout growth. Given these regularities, D. boschmai grows in a zigzag fashion by alternately budding on the right and left sites. In contrast, D. cribrosa grows helically by budding at a particular site.

Conclusions/significance: The strict constraints on budding regularities and shifts in budding sites observed in the sympodial growth forms of corals greatly affect resulting morphologies in azooxanthellate coral colonies. A precise understanding of these intrinsic constraints leads to a fundamental comprehension of colony-forming mechanisms in modular organisms.

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Branching area and growth direction (red triangles, directive septa; green triangles, the four lateral primary septa; red circles, budding site; arrows, growth direction; 1, parent corallites; 2, daughter corallites; 3, grandchild corallites).A–D, Dendrophyllia boschmai (OCU 6661). E–I, Dendrophyllia cribrosa (OCU 6671). Scale bars = 5 mm. A and E, Branching area of colony. B and F, Drawings of A and E, showing the branching area and budding sites. C, Front view. D, Drawing of C, showing the branching area and growth direction. G, Top view of the colony shown in the left side of E. H, A drawing of G, showing the sinistral growth direction. I, Top view of the colony shown in the right side of E. J, A drawing of I, showing the dextral growth direction.
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pone-0063790-g006: Branching area and growth direction (red triangles, directive septa; green triangles, the four lateral primary septa; red circles, budding site; arrows, growth direction; 1, parent corallites; 2, daughter corallites; 3, grandchild corallites).A–D, Dendrophyllia boschmai (OCU 6661). E–I, Dendrophyllia cribrosa (OCU 6671). Scale bars = 5 mm. A and E, Branching area of colony. B and F, Drawings of A and E, showing the branching area and budding sites. C, Front view. D, Drawing of C, showing the branching area and growth direction. G, Top view of the colony shown in the left side of E. H, A drawing of G, showing the sinistral growth direction. I, Top view of the colony shown in the right side of E. J, A drawing of I, showing the dextral growth direction.

Mentions: Figure 6A–D shows the budding sites and growth modes of D. boschmai. Ordinarily, D. boschmai buds alternately at one of the two lateral primary septa of a corallite (Figs. 4E, F, 6D). Therefore, the colony grows upwards in a zigzag fashion (Figs. 4G, 6C–D) without showing an axial corallite in a sympodial apart from monopodial form. However, when branching dichotomously, offsets occur in both of the two lateral primary septa (Fig. 6A–B), in which case the colony is bilaterally symmetrical along the directive septa of a branching corallite, with a definite polarity. After branching, individuals again grow upwards in a zigzag fashion.


Intrinsic constraints on sympodial growth morphologies of azooxanthellate scleractinian coral Dendrophyllia.

Sentoku A, Ezaki Y - PLoS ONE (2013)

Branching area and growth direction (red triangles, directive septa; green triangles, the four lateral primary septa; red circles, budding site; arrows, growth direction; 1, parent corallites; 2, daughter corallites; 3, grandchild corallites).A–D, Dendrophyllia boschmai (OCU 6661). E–I, Dendrophyllia cribrosa (OCU 6671). Scale bars = 5 mm. A and E, Branching area of colony. B and F, Drawings of A and E, showing the branching area and budding sites. C, Front view. D, Drawing of C, showing the branching area and growth direction. G, Top view of the colony shown in the left side of E. H, A drawing of G, showing the sinistral growth direction. I, Top view of the colony shown in the right side of E. J, A drawing of I, showing the dextral growth direction.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3646883&req=5

pone-0063790-g006: Branching area and growth direction (red triangles, directive septa; green triangles, the four lateral primary septa; red circles, budding site; arrows, growth direction; 1, parent corallites; 2, daughter corallites; 3, grandchild corallites).A–D, Dendrophyllia boschmai (OCU 6661). E–I, Dendrophyllia cribrosa (OCU 6671). Scale bars = 5 mm. A and E, Branching area of colony. B and F, Drawings of A and E, showing the branching area and budding sites. C, Front view. D, Drawing of C, showing the branching area and growth direction. G, Top view of the colony shown in the left side of E. H, A drawing of G, showing the sinistral growth direction. I, Top view of the colony shown in the right side of E. J, A drawing of I, showing the dextral growth direction.
Mentions: Figure 6A–D shows the budding sites and growth modes of D. boschmai. Ordinarily, D. boschmai buds alternately at one of the two lateral primary septa of a corallite (Figs. 4E, F, 6D). Therefore, the colony grows upwards in a zigzag fashion (Figs. 4G, 6C–D) without showing an axial corallite in a sympodial apart from monopodial form. However, when branching dichotomously, offsets occur in both of the two lateral primary septa (Fig. 6A–B), in which case the colony is bilaterally symmetrical along the directive septa of a branching corallite, with a definite polarity. After branching, individuals again grow upwards in a zigzag fashion.

Bottom Line: However, little is known about the intrinsic mechanisms that control asexual reproduction and the resultant morphologies of colonies.The strict constraints on budding regularities and shifts in budding sites observed in the sympodial growth forms of corals greatly affect resulting morphologies in azooxanthellate coral colonies.A precise understanding of these intrinsic constraints leads to a fundamental comprehension of colony-forming mechanisms in modular organisms.

View Article: PubMed Central - PubMed

Affiliation: Department of Geosciences, Graduate School of Science, Osaka City University, Osaka, Japan. sentoku@sci.osaka-cu.ac.jp

ABSTRACT

Background: Asexual increase occurs in virtually all colonial organisms. However, little is known about the intrinsic mechanisms that control asexual reproduction and the resultant morphologies of colonies. Scleractinian corals, both symbiotic (zoaxanthellate) and non-symbiotic (azooxanthellate) corals are known to form elaborate colonies. To better understand the growth mechanisms that control species-specific type of colony in azooxanthellate dendrophyllid scleractinian corals, we have studied details of the budding pattern in the sympodial colonies of Dendrophyllia boschmai and Dendrophyllia cribrosa.

Principal findings: Budding exhibits the following regularities: (1) the two directive septa of offset corallites are oriented almost perpendicular to the growth direction of parent corallites; (2) offsets generally occur in either of the lateral primary septa that occur on one side of a corallite; the individuals thus show a definite polarity with respect to the directive septa, and only when branching dichotomously offsets occur in both primary septa; (3) the lateral corallites grow more-or-less diagonally upwards; and (4) the regularities and polarities are maintained throughout growth. Given these regularities, D. boschmai grows in a zigzag fashion by alternately budding on the right and left sites. In contrast, D. cribrosa grows helically by budding at a particular site.

Conclusions/significance: The strict constraints on budding regularities and shifts in budding sites observed in the sympodial growth forms of corals greatly affect resulting morphologies in azooxanthellate coral colonies. A precise understanding of these intrinsic constraints leads to a fundamental comprehension of colony-forming mechanisms in modular organisms.

Show MeSH