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Conspecificity of two morphologically distinct calcified red algae from the northwest Pacific Ocean: Galaxaura pacifica and G. filamentosa (Galaxauraceae, Rhodophyta)

View Article: PubMed Central

ABSTRACT

Background: Members of the calcified red algal genus, Galaxaura, are distributed predominantly in warm temperate, subtropical, and tropical regions worldwide. The capacity of these algae to form calcified thalli could play a critical role in the carbon cycle of these ecosystems. Previous studies have suggested that the reported species diversity of Galaxaura may be exaggerated due to a lack of knowledge regarding external morphological differences between gametophytic and tetrasporophytic plants (or among different life stages) of a single species.

Results: To examine this issue, this study collected specimens of two morphologically distinct Galaxaura from Taiwan and the Philippines. These specimens were initially identified as two species (G. pacifica Tanaka and G. filamentosa Chou ex Taylor) based on their morphological features. Our molecular analyses, however, unexpectedly showed that these two specimens shared 100% identical rbc L sequences, indicating that they represented a single species comprising two distinct external morphologies. Furthermore, our extensive observations and molecular analyses on several specimens from different locations in southern Taiwan has revealed that these morphological differences could be due to seasonal variation.

Conclusions: This study proposes that G. “filamentosa” from the Philippines could represent the remnants of the lower villous part of older gametophytic plants of G. pacifica after senescence of the upper smooth part of the thallus. As such we propose that these two previously distinct algal species from the northwest Pacific Ocean as a single species, G. pacifica. This study shows that the biodiversity of the calcified red algae Galaxaura could be overestimated without the assistance of molecular tools. Additionally, this study provides insights into the biodiversity and unique biology of the calcified red algae Galaxaura.

Electronic supplementary material: The online version of this article (doi:10.1186/1999-3110-54-1) contains supplementary material, which is available to authorized users.

No MeSH data available.


Related in: MedlinePlus

Developmental sequence of the cystocarp ofGalaxaura pacificaTanaka from Small Port, KNP, southern Taiwan.(A) Young carpogonial branch replaces one of the dichotomous vegetative cortical (co) branches showing a trichogyne (t), a carpogonium (c), a hypogynous cell (h), and a basal cell (b); (B) Young carpogonial branch protruding between the dichotomous vegetative cortical (co) branches showing a trichogyne (t), a carpogonium (c), a hypogynous cell (h) bearing the sterile branch (arrow), and a basal cell (b); (C) Two mature carpogonial branches borne on the vegetative cortical (co) branch showing trichogyne (t), carpogonium (c), hypogynous cell bearing several sterile branches (arrowheads), and basal cell bearing several involucral filaments (arrows); (D) Mature carpogonial branch showing a trichogyne (t), a carpogonium (c), a hypogynous cell (h) bearing several sterile branches (arrowheads) with darkly stained nuclei, and a basal cell (b) bearing several involucral filaments (arrows); (E) Cross section of young cystocarp showing developing gonimoblast filaments (gf), a distinct fusion cell (fc), a hypogynous cell (h), and a basal cell (b) bearing numerous involucral filaments (arrows) surrounding the base of cystocarp; (F) Cross section of immature cystocarp showing the fusion cell (fc) incorporated with the inner three gonimoblast cells and gonimoblast initial (gi), a hypogynous cell (h) bearing several modified sterile branches (arrowheads), and a basal cell (b) producing several involucral filaments (arrows) surrounding the base of the cystocarp; (G) Further development of immature cystocarp showing the gonimoblast filaments producing terminal carposporangia (cp), the distinct fusion cell (fc) incorporated with 7-10 inner gonimoblast cells and gonimoblast initial (gi), a hypogynous cell (h) bearing several modified sterile branches (arrowheads), and a basal cell bearing numerous involucral filaments surrounding the base of the cystocarp; (H) Cross section of mature cystocarp showing gonimoblast filaments (gf) producing terminal carposporangia (cp), the distinct fusion cell (fc), a hypogynous cell (h) with its derived sterile branch (arrowhead), and a basal cell (b) producing numerous involucral filaments (arrows) surrounding the base of the cystocarp.
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Fig8: Developmental sequence of the cystocarp ofGalaxaura pacificaTanaka from Small Port, KNP, southern Taiwan.(A) Young carpogonial branch replaces one of the dichotomous vegetative cortical (co) branches showing a trichogyne (t), a carpogonium (c), a hypogynous cell (h), and a basal cell (b); (B) Young carpogonial branch protruding between the dichotomous vegetative cortical (co) branches showing a trichogyne (t), a carpogonium (c), a hypogynous cell (h) bearing the sterile branch (arrow), and a basal cell (b); (C) Two mature carpogonial branches borne on the vegetative cortical (co) branch showing trichogyne (t), carpogonium (c), hypogynous cell bearing several sterile branches (arrowheads), and basal cell bearing several involucral filaments (arrows); (D) Mature carpogonial branch showing a trichogyne (t), a carpogonium (c), a hypogynous cell (h) bearing several sterile branches (arrowheads) with darkly stained nuclei, and a basal cell (b) bearing several involucral filaments (arrows); (E) Cross section of young cystocarp showing developing gonimoblast filaments (gf), a distinct fusion cell (fc), a hypogynous cell (h), and a basal cell (b) bearing numerous involucral filaments (arrows) surrounding the base of cystocarp; (F) Cross section of immature cystocarp showing the fusion cell (fc) incorporated with the inner three gonimoblast cells and gonimoblast initial (gi), a hypogynous cell (h) bearing several modified sterile branches (arrowheads), and a basal cell (b) producing several involucral filaments (arrows) surrounding the base of the cystocarp; (G) Further development of immature cystocarp showing the gonimoblast filaments producing terminal carposporangia (cp), the distinct fusion cell (fc) incorporated with 7-10 inner gonimoblast cells and gonimoblast initial (gi), a hypogynous cell (h) bearing several modified sterile branches (arrowheads), and a basal cell bearing numerous involucral filaments surrounding the base of the cystocarp; (H) Cross section of mature cystocarp showing gonimoblast filaments (gf) producing terminal carposporangia (cp), the distinct fusion cell (fc), a hypogynous cell (h) with its derived sterile branch (arrowhead), and a basal cell (b) producing numerous involucral filaments (arrows) surrounding the base of the cystocarp.

Mentions: (FiguresĀ 5A-5N, 6A-6E, 7A-7C, 8A-8H, 9A-9E and 10A-10G).Figure 6


Conspecificity of two morphologically distinct calcified red algae from the northwest Pacific Ocean: Galaxaura pacifica and G. filamentosa (Galaxauraceae, Rhodophyta)
Developmental sequence of the cystocarp ofGalaxaura pacificaTanaka from Small Port, KNP, southern Taiwan.(A) Young carpogonial branch replaces one of the dichotomous vegetative cortical (co) branches showing a trichogyne (t), a carpogonium (c), a hypogynous cell (h), and a basal cell (b); (B) Young carpogonial branch protruding between the dichotomous vegetative cortical (co) branches showing a trichogyne (t), a carpogonium (c), a hypogynous cell (h) bearing the sterile branch (arrow), and a basal cell (b); (C) Two mature carpogonial branches borne on the vegetative cortical (co) branch showing trichogyne (t), carpogonium (c), hypogynous cell bearing several sterile branches (arrowheads), and basal cell bearing several involucral filaments (arrows); (D) Mature carpogonial branch showing a trichogyne (t), a carpogonium (c), a hypogynous cell (h) bearing several sterile branches (arrowheads) with darkly stained nuclei, and a basal cell (b) bearing several involucral filaments (arrows); (E) Cross section of young cystocarp showing developing gonimoblast filaments (gf), a distinct fusion cell (fc), a hypogynous cell (h), and a basal cell (b) bearing numerous involucral filaments (arrows) surrounding the base of cystocarp; (F) Cross section of immature cystocarp showing the fusion cell (fc) incorporated with the inner three gonimoblast cells and gonimoblast initial (gi), a hypogynous cell (h) bearing several modified sterile branches (arrowheads), and a basal cell (b) producing several involucral filaments (arrows) surrounding the base of the cystocarp; (G) Further development of immature cystocarp showing the gonimoblast filaments producing terminal carposporangia (cp), the distinct fusion cell (fc) incorporated with 7-10 inner gonimoblast cells and gonimoblast initial (gi), a hypogynous cell (h) bearing several modified sterile branches (arrowheads), and a basal cell bearing numerous involucral filaments surrounding the base of the cystocarp; (H) Cross section of mature cystocarp showing gonimoblast filaments (gf) producing terminal carposporangia (cp), the distinct fusion cell (fc), a hypogynous cell (h) with its derived sterile branch (arrowhead), and a basal cell (b) producing numerous involucral filaments (arrows) surrounding the base of the cystocarp.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5383922&req=5

Fig8: Developmental sequence of the cystocarp ofGalaxaura pacificaTanaka from Small Port, KNP, southern Taiwan.(A) Young carpogonial branch replaces one of the dichotomous vegetative cortical (co) branches showing a trichogyne (t), a carpogonium (c), a hypogynous cell (h), and a basal cell (b); (B) Young carpogonial branch protruding between the dichotomous vegetative cortical (co) branches showing a trichogyne (t), a carpogonium (c), a hypogynous cell (h) bearing the sterile branch (arrow), and a basal cell (b); (C) Two mature carpogonial branches borne on the vegetative cortical (co) branch showing trichogyne (t), carpogonium (c), hypogynous cell bearing several sterile branches (arrowheads), and basal cell bearing several involucral filaments (arrows); (D) Mature carpogonial branch showing a trichogyne (t), a carpogonium (c), a hypogynous cell (h) bearing several sterile branches (arrowheads) with darkly stained nuclei, and a basal cell (b) bearing several involucral filaments (arrows); (E) Cross section of young cystocarp showing developing gonimoblast filaments (gf), a distinct fusion cell (fc), a hypogynous cell (h), and a basal cell (b) bearing numerous involucral filaments (arrows) surrounding the base of cystocarp; (F) Cross section of immature cystocarp showing the fusion cell (fc) incorporated with the inner three gonimoblast cells and gonimoblast initial (gi), a hypogynous cell (h) bearing several modified sterile branches (arrowheads), and a basal cell (b) producing several involucral filaments (arrows) surrounding the base of the cystocarp; (G) Further development of immature cystocarp showing the gonimoblast filaments producing terminal carposporangia (cp), the distinct fusion cell (fc) incorporated with 7-10 inner gonimoblast cells and gonimoblast initial (gi), a hypogynous cell (h) bearing several modified sterile branches (arrowheads), and a basal cell bearing numerous involucral filaments surrounding the base of the cystocarp; (H) Cross section of mature cystocarp showing gonimoblast filaments (gf) producing terminal carposporangia (cp), the distinct fusion cell (fc), a hypogynous cell (h) with its derived sterile branch (arrowhead), and a basal cell (b) producing numerous involucral filaments (arrows) surrounding the base of the cystocarp.
Mentions: (FiguresĀ 5A-5N, 6A-6E, 7A-7C, 8A-8H, 9A-9E and 10A-10G).Figure 6

View Article: PubMed Central

ABSTRACT

Background: Members of the calcified red algal genus, Galaxaura, are distributed predominantly in warm temperate, subtropical, and tropical regions worldwide. The capacity of these algae to form calcified thalli could play a critical role in the carbon cycle of these ecosystems. Previous studies have suggested that the reported species diversity of Galaxaura may be exaggerated due to a lack of knowledge regarding external morphological differences between gametophytic and tetrasporophytic plants (or among different life stages) of a single species.

Results: To examine this issue, this study collected specimens of two morphologically distinct Galaxaura from Taiwan and the Philippines. These specimens were initially identified as two species (G. pacifica Tanaka and G. filamentosa Chou ex Taylor) based on their morphological features. Our molecular analyses, however, unexpectedly showed that these two specimens shared 100% identical rbc L sequences, indicating that they represented a single species comprising two distinct external morphologies. Furthermore, our extensive observations and molecular analyses on several specimens from different locations in southern Taiwan has revealed that these morphological differences could be due to seasonal variation.

Conclusions: This study proposes that G. “filamentosa” from the Philippines could represent the remnants of the lower villous part of older gametophytic plants of G. pacifica after senescence of the upper smooth part of the thallus. As such we propose that these two previously distinct algal species from the northwest Pacific Ocean as a single species, G. pacifica. This study shows that the biodiversity of the calcified red algae Galaxaura could be overestimated without the assistance of molecular tools. Additionally, this study provides insights into the biodiversity and unique biology of the calcified red algae Galaxaura.

Electronic supplementary material: The online version of this article (doi:10.1186/1999-3110-54-1) contains supplementary material, which is available to authorized users.

No MeSH data available.


Related in: MedlinePlus