Ecological and morphological profile of floating spherical Cladophora socialis aggregations in central Thailand - PubMed (original) (raw)

. 2015 Apr 21;10(4):e0124997.

doi: 10.1371/journal.pone.0124997. eCollection 2015.

Tatsuo Miyoshi 2, Halethichanok Sukchai 3, Piyarat Pinphoo 4, Dusit Aue-Umneoy 4, Chonlada Meeanan 3, Jaruwan Songphatkaew 4, Sirimas Klomkling 3, Iori Yamaguchi 5, Monthon Ganmanee 4, Hiroyuki Sudo 6, Kaoru Hamano 2

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Ecological and morphological profile of floating spherical Cladophora socialis aggregations in central Thailand

Isao Tsutsui et al. PLoS One. 2015.

Abstract

The unique beauty of spherical aggregation forming algae has attracted much attention from both the scientific and lay communities. Several aegagropilous seaweeds have been identified to date, including the plants of genus Cladophora and Chaetomorpha. However, this phenomenon remains poorly understood. In July 2013, a mass occurrence of spherical Cladophora aggregations was observed in a salt field reservoir in Central Thailand. The aims of the present study were to describe the habitat of the spherical aggregations and confirm the species. We performed a field survey, internal and external morphological observations, pyrenoid ultrastructure observations, and molecular sequence analysis. Floating spherical Cladophora aggregations (1-8 cm in diameter) were observed in an area ~560 m2, on the downwind side of the reservoir where there was water movement. Individual filaments in the aggregations were entangled in each other; consequently, branches growing in different directions were observed within a clump. We suggest that water movement and morphological characteristics promote the formation of spherical aggregations in this species. The molecular sequencing results revealed that the study species was highly homologous to both C. socialis and C. coelothrix. However, the diameter of the apical cells in the study species was less than that of C. coelothrix. The pyrenoid ultrastructure was more consistent with that of C. socialis. We conclude that the study species is C. socialis. This first record of spherical aggregations in this species advances our understanding of these formations. However, further detailed physical measurements are required to fully elucidate the mechanism behind these spherical formations.

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Conflict of interest statement

Competing Interests: The authors declare that they have no competing interests.

Figures

Fig 1

Fig 1. Map showing field survey location in Central Thailand.

Fig 2

Fig 2. Mass floating spherical aggregations of Cladophora socialis in a salt field reservoir in Central Thailand.

Fig 3

Fig 3. Transverse schematic diagram showing the location of several Cladophora socialis forms at the study site.

Fig 4

Fig 4. Floating spherical aggregations of Cladophora socialis in a salt field reservoir, a natural habitat.

(a) A lower hemisphere of spherical aggregations of a solid, dark green color: (b) On-land view of floating spherical aggregations: (c) Underwater view of Indeterminate turf forms.

Fig 5

Fig 5. Scattergraph showing the size of spherical Cladophora socialis (major and minor axis) aggregations.

Fig 6

Fig 6. Morphological characteristics of Cladophora socialis.

(a) A fresh individual thallus: (b) Filaments attaching to one another by rhizoids formed apically (filled-arrow) and intercalary (open-arrow): (c) Apical cell in natural individual: (d) Apical cell cultured in static water showing longer length: (e) Main axis cells: (f) Branching system: (g) Filaments showing different growing directions because of a bent obtuse angle: (h) Newly formed lateral (filled-arrow) without cross-wall at its base: (i) Multi-nuclei in a cell stained by the Wittmann method: (j) Parietal chloroplasts along the cell wall: (k) Transmission electron microscopic image of bilenticular type pyrenoid: (l) Transmission electron microscopic image of zonal type pyrenoid.

Fig 7

Fig 7. Growth of Cladophora socialis in laboratory experiments.

(a) Day 0: (b) Day 1: (c) Day 2: (d) Day 3: (e) Day 4: (f) Day 5: (g) Day 6: (h) Day 7.

Fig 8

Fig 8. Maximum likelihood phylogenetic trees for Cladophora socialis and relatives.

(a) A tree based on nearly complete 18S rDNA sequences: (b) A tree based on partial 28S rDNA sequences. Other data on Cladophorales were downloaded from GenBank for comparison. Numbers close to the nodes are ML/MP bootstrap values.

Fig 9

Fig 9. Monthly maximum velocity (m s−1) and wind direction in Central Thailand.

Graphs were drawn from raw data provided by the Thai Meteorological Department [38].

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Grants and funding

This study was funded and performed as part of the international research project “Development of aquaculture technologies for suitable and equitable production of aquatic products in tropical coastal areas” conducted by the Faculty of Agricultural Technology, KMITL and the Fisheries Division, JIRCAS. The funding bodies had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

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