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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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Schematic constructions of calicular features, and sympodial as well as monopodial forms of colonies.A, Calicular view, showing the two opposite directive septa, the greater calicular diameter (GCD), and the lesser calicular diameter (LCD). Numbers indicate the cycles of septa; the first cycle of septa is circled. The two directive septa are indicated by black triangles, whereas the four remaining septa are shown by white triangles. B, Sympodial form of colony. TH indicates the corallum height, and LH the lateral corallum length. Note that the colony does not possess an axial corallite. C, Monopodial form of colony. D, Budding site of monopodial colony form, where offsets generally occur in some of the lateral primary septa.
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pone-0063790-g002: Schematic constructions of calicular features, and sympodial as well as monopodial forms of colonies.A, Calicular view, showing the two opposite directive septa, the greater calicular diameter (GCD), and the lesser calicular diameter (LCD). Numbers indicate the cycles of septa; the first cycle of septa is circled. The two directive septa are indicated by black triangles, whereas the four remaining septa are shown by white triangles. B, Sympodial form of colony. TH indicates the corallum height, and LH the lateral corallum length. Note that the colony does not possess an axial corallite. C, Monopodial form of colony. D, Budding site of monopodial colony form, where offsets generally occur in some of the lateral primary septa.

Mentions: We examined 45 coralla of Dendrophyllia boschmai (Fig. 1A–D) and 43 coralla of D. cribrosa (Fig. 1E–H), collected at water depths of 7–165 m offshore of Minabe (Wakayama Prefecture), Amakusa (Nagasaki Prefecture), and Minamiise (Mie Prefecture) in southwest Japan. Of these, 20 coralla were selected for analysis and the morphometric parameters of constituent individuals were measured. The greater calicular diameter (GCD; sensu[16]) is oriented parallel to the two directive septa (Fig. 2A). The maximum GCD of D. boschmai is 11.2 mm and the maximum lesser calicular diameter (LCD; sensu[16]) is 9.3 mm (Fig. 2A). The maximum GCD of D. cribrosa is 6.0 mm and the maximum LCD is 5.1 mm. The studied specimens are registered in the Department of Geosciences, Graduate School of Science, Osaka City University, Japan (OCU 6669–6688).


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

Sentoku A, Ezaki Y - PLoS ONE (2013)

Schematic constructions of calicular features, and sympodial as well as monopodial forms of colonies.A, Calicular view, showing the two opposite directive septa, the greater calicular diameter (GCD), and the lesser calicular diameter (LCD). Numbers indicate the cycles of septa; the first cycle of septa is circled. The two directive septa are indicated by black triangles, whereas the four remaining septa are shown by white triangles. B, Sympodial form of colony. TH indicates the corallum height, and LH the lateral corallum length. Note that the colony does not possess an axial corallite. C, Monopodial form of colony. D, Budding site of monopodial colony form, where offsets generally occur in some of the lateral primary septa.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0063790-g002: Schematic constructions of calicular features, and sympodial as well as monopodial forms of colonies.A, Calicular view, showing the two opposite directive septa, the greater calicular diameter (GCD), and the lesser calicular diameter (LCD). Numbers indicate the cycles of septa; the first cycle of septa is circled. The two directive septa are indicated by black triangles, whereas the four remaining septa are shown by white triangles. B, Sympodial form of colony. TH indicates the corallum height, and LH the lateral corallum length. Note that the colony does not possess an axial corallite. C, Monopodial form of colony. D, Budding site of monopodial colony form, where offsets generally occur in some of the lateral primary septa.
Mentions: We examined 45 coralla of Dendrophyllia boschmai (Fig. 1A–D) and 43 coralla of D. cribrosa (Fig. 1E–H), collected at water depths of 7–165 m offshore of Minabe (Wakayama Prefecture), Amakusa (Nagasaki Prefecture), and Minamiise (Mie Prefecture) in southwest Japan. Of these, 20 coralla were selected for analysis and the morphometric parameters of constituent individuals were measured. The greater calicular diameter (GCD; sensu[16]) is oriented parallel to the two directive septa (Fig. 2A). The maximum GCD of D. boschmai is 11.2 mm and the maximum lesser calicular diameter (LCD; sensu[16]) is 9.3 mm (Fig. 2A). The maximum GCD of D. cribrosa is 6.0 mm and the maximum LCD is 5.1 mm. The studied specimens are registered in the Department of Geosciences, Graduate School of Science, Osaka City University, Japan (OCU 6669–6688).

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
Related in: MedlinePlus