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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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Results of regularities in budding (red triangles, directive septa; green triangles, the four lateral primary septa; red circles, budding site; 1, parent corallites; 2, daughter corallites; 3, grandchild corallites; arrows, growth direction).A–F, Dendrophyllia boschmai (OCU 6654–6658). G–L, Dendrophyllia cribrosa (OCU 6664–6668). A–D and H–J, Orientations of directive septa. A–D, The directive septa of corallites, which are apparently perpendicular to the growth direction of the branch. Scale bars = 10 mm. A, Left-side view of the colony shown in C. B, Right-side view of the colony shown in C. C, Front view of the colony shown in A and B. D, Right-side view of the colony shown in G. H, The directive septa of corallites, which are apparently parallel to the growth direction of the branch. Scale bars = 5 mm. I, J, Actual relationships between directive septa of parent and its derived corallites. Scale bars = 5 mm. E, F, J, and L, Budding sites. Scale bars = 5 mm. The offsets ordinarily occur in either of the primary septum on one side of individual corallites, excluding the directive septum. G and M, Inclinations of budding. Scale bars = 10 mm.
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pone-0063790-g004: Results of regularities in budding (red triangles, directive septa; green triangles, the four lateral primary septa; red circles, budding site; 1, parent corallites; 2, daughter corallites; 3, grandchild corallites; arrows, growth direction).A–F, Dendrophyllia boschmai (OCU 6654–6658). G–L, Dendrophyllia cribrosa (OCU 6664–6668). A–D and H–J, Orientations of directive septa. A–D, The directive septa of corallites, which are apparently perpendicular to the growth direction of the branch. Scale bars = 10 mm. A, Left-side view of the colony shown in C. B, Right-side view of the colony shown in C. C, Front view of the colony shown in A and B. D, Right-side view of the colony shown in G. H, The directive septa of corallites, which are apparently parallel to the growth direction of the branch. Scale bars = 5 mm. I, J, Actual relationships between directive septa of parent and its derived corallites. Scale bars = 5 mm. E, F, J, and L, Budding sites. Scale bars = 5 mm. The offsets ordinarily occur in either of the primary septum on one side of individual corallites, excluding the directive septum. G and M, Inclinations of budding. Scale bars = 10 mm.

Mentions: Figure 4A–D and 5A show that the orientations of the directive septa of corallites in Dendrophyllia boschmai are nearly perpendicular to the growth directions of branches. For 94 of the 110 corallites (85 %), the orientations fall within the range 0°–10° (average, 7.5°). In contrast, Figure 4H–J and 5B show that the orientations of the directive septa of corallites of D. cribrosa are apparently parallel to the growth direction of the branch (Fig. 4H). However, careful observations of the relationships between them (red triangles, Fig. 4I, J) indicate that the orientations are clearly perpendicular to the growth direction of the parent corallites (blue arrows, Fig. 4I, J). For 35 of the 69 corallites (50.7 %), the orientations fall within the range 0°–10° (average, 5.7°). The directive septa of lateral corallites are thus commonly oriented nearly perpendicular to those of the immediate parent corallites.


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

Sentoku A, Ezaki Y - PLoS ONE (2013)

Results of regularities in budding (red triangles, directive septa; green triangles, the four lateral primary septa; red circles, budding site; 1, parent corallites; 2, daughter corallites; 3, grandchild corallites; arrows, growth direction).A–F, Dendrophyllia boschmai (OCU 6654–6658). G–L, Dendrophyllia cribrosa (OCU 6664–6668). A–D and H–J, Orientations of directive septa. A–D, The directive septa of corallites, which are apparently perpendicular to the growth direction of the branch. Scale bars = 10 mm. A, Left-side view of the colony shown in C. B, Right-side view of the colony shown in C. C, Front view of the colony shown in A and B. D, Right-side view of the colony shown in G. H, The directive septa of corallites, which are apparently parallel to the growth direction of the branch. Scale bars = 5 mm. I, J, Actual relationships between directive septa of parent and its derived corallites. Scale bars = 5 mm. E, F, J, and L, Budding sites. Scale bars = 5 mm. The offsets ordinarily occur in either of the primary septum on one side of individual corallites, excluding the directive septum. G and M, Inclinations of budding. Scale bars = 10 mm.
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Related In: Results  -  Collection

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pone-0063790-g004: Results of regularities in budding (red triangles, directive septa; green triangles, the four lateral primary septa; red circles, budding site; 1, parent corallites; 2, daughter corallites; 3, grandchild corallites; arrows, growth direction).A–F, Dendrophyllia boschmai (OCU 6654–6658). G–L, Dendrophyllia cribrosa (OCU 6664–6668). A–D and H–J, Orientations of directive septa. A–D, The directive septa of corallites, which are apparently perpendicular to the growth direction of the branch. Scale bars = 10 mm. A, Left-side view of the colony shown in C. B, Right-side view of the colony shown in C. C, Front view of the colony shown in A and B. D, Right-side view of the colony shown in G. H, The directive septa of corallites, which are apparently parallel to the growth direction of the branch. Scale bars = 5 mm. I, J, Actual relationships between directive septa of parent and its derived corallites. Scale bars = 5 mm. E, F, J, and L, Budding sites. Scale bars = 5 mm. The offsets ordinarily occur in either of the primary septum on one side of individual corallites, excluding the directive septum. G and M, Inclinations of budding. Scale bars = 10 mm.
Mentions: Figure 4A–D and 5A show that the orientations of the directive septa of corallites in Dendrophyllia boschmai are nearly perpendicular to the growth directions of branches. For 94 of the 110 corallites (85 %), the orientations fall within the range 0°–10° (average, 7.5°). In contrast, Figure 4H–J and 5B show that the orientations of the directive septa of corallites of D. cribrosa are apparently parallel to the growth direction of the branch (Fig. 4H). However, careful observations of the relationships between them (red triangles, Fig. 4I, J) indicate that the orientations are clearly perpendicular to the growth direction of the parent corallites (blue arrows, Fig. 4I, J). For 35 of the 69 corallites (50.7 %), the orientations fall within the range 0°–10° (average, 5.7°). The directive septa of lateral corallites are thus commonly oriented nearly perpendicular to those of the immediate parent corallites.

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