A stable ultrastructural pattern despite variable cell size in <i>Lithothamnion corallioides</i>
<p>Recent advances on the mechanism and pattern of calcification in coralline algae led to contradictory conclusions. The evidence of a biologically controlled calcification process, resulting in distinctive patterns at the scale of family, was observed. However, the coralline calcification pr...
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| Autores principales: | , , |
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| Formato: | article |
| Lenguaje: | EN |
| Publicado: |
Copernicus Publications
2021
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| Materias: | |
| Acceso en línea: | https://doaj.org/article/7200ce741df245a69a507c5227d9f443 |
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| Sumario: | <p>Recent advances on the mechanism and pattern of calcification in
coralline algae led to contradictory conclusions. The evidence of a
biologically controlled calcification process, resulting in distinctive
patterns at the scale of family, was observed. However, the coralline
calcification process has been also interpreted as biologically induced
because of the dependency of its elemental composition on environmental
variables. To clarify the matter, five collections of <i>Lithothamnion corallioides</i> from the Atlantic
Ocean and the Mediterranean Sea, across a wide depth range (12–66 m), have
been analyzed for morphology, anatomy and cell wall crystal patterns in
both perithallial and epithallial cells to detect possible ultrastructural
changes. <i>L. corallioides</i> shows the alternation of tiers of short-squared and
long-ovoid/rectangular cells along the perithallus, forming a typical
banding. The perithallial cell length decreases according to water depth and
growth rate, whereas the diameter remains constant. Our observations confirm
that both epithallial and perithallial cells show primary (PW) and secondary
(SW) calcite walls. Rectangular tiles, with the long axis parallel to the
cell membrane forming a multi-layered structure, characterize the PW.
Flattened squared bricks characterize the SW, with roundish outlines
enveloping the cell and showing a zigzag and cross orientation. Long and
short cells have different thicknesses of PW and SW, increasing in short
cells. Epithallial cells are one to three flared cells with the same
shape of the PW and SW crystals. Despite the diverse seafloor environments
and the variable <i>L. corallioides</i> growth rate, the cell walls maintain a consistent
ultrastructural pattern with unaffected crystal shape and arrangement. A
comparison with two congeneric species, <i>L. minervae</i> and <i>L. valens</i>, showed similar
ultrastructural patterns in the SW but evident differences in the PW crystal
shape. Our observations point to a biologically control rather than an
induction of the calcification process in coralline algae and suggest a
possible new morphological diagnostic tool for species identification, with
relevant importance for paleontological applications. Finally, secondary
calcite, in the form of dogtooth crystals that fill the cell lumen, has been
observed. It represents a form of early alteration in living collections
which can have implications in the reliability of climate and paleoclimate
studies based on geochemical techniques.</p> |
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