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Experimental observations on ultrastructure of scales of red seabream (Pagrosomus major) for seawater pH monitoring Cover

Experimental observations on ultrastructure of scales of red seabream (Pagrosomus major) for seawater pH monitoring

Oceanological and Hydrobiological Studies
Volume 54 (2025): Issue 4 (December 2025)
By: Weili Hou,  Li Tian,  Xin Sun,  Xin Li,  Xiangming Chen and  Haijun Song  
Open Access
|Dec 2025

Figures & Tables

Figure 1

Overall view of sea bream (P. major) and morphology of caudal, ventral, and dorsal scales under stereomicroscopy. (A) Schematic diagram depicting three distinct anatomical regions of scale removal from the left lateral side of the red seabream (P. major). (B–D) Photomicrographs of scales from the caudal (tail), ventral (abdominal), and dorsal (back) regions, respectively, obtained via optical microscopy.
Overall view of sea bream (P. major) and morphology of caudal, ventral, and dorsal scales under stereomicroscopy. (A) Schematic diagram depicting three distinct anatomical regions of scale removal from the left lateral side of the red seabream (P. major). (B–D) Photomicrographs of scales from the caudal (tail), ventral (abdominal), and dorsal (back) regions, respectively, obtained via optical microscopy.

Figure 2

Fish scale structures at different scales under FE-SEM. (A) Morphological terminology of the scale. (B, C) Focused areas of the anterior field and posterior field under scanning electron microscopy (SEM), respectively. (D, E) Schematic diagrams of the measurement scale, illustrating the methodologies for quantifying the longitudinal and basal transverse dimensions of the microstructural components ctenii and lepidont, respectively. FE-SEM, field emission scanning electron microscopy.
Fish scale structures at different scales under FE-SEM. (A) Morphological terminology of the scale. (B, C) Focused areas of the anterior field and posterior field under scanning electron microscopy (SEM), respectively. (D, E) Schematic diagrams of the measurement scale, illustrating the methodologies for quantifying the longitudinal and basal transverse dimensions of the microstructural components ctenii and lepidont, respectively. FE-SEM, field emission scanning electron microscopy.

Figure 3

FE-SEM analysis of ctenii ultrastructures in scales from different body regions (caudal, ventral, dorsal). From left to right: FE-SEM images of the ctenii regions in scales from the caudal (tail), ventral (abdomen), and dorsal (back) regions of red seabream (P. major). (A, F, K) Untreated control scales from the three respective body regions. (B–E) FE-SEM images of caudal scales exposed to experimental aquaria with pH levels of 7.1, 7.5, 7.7, and 7.9, respectively. (G–J, L–O) Correspond to FE-SEM images of ventral scales and dorsal scales under identical pH treatments, respectively. FE-SEM, field emission scanning electron microscopy.
FE-SEM analysis of ctenii ultrastructures in scales from different body regions (caudal, ventral, dorsal). From left to right: FE-SEM images of the ctenii regions in scales from the caudal (tail), ventral (abdomen), and dorsal (back) regions of red seabream (P. major). (A, F, K) Untreated control scales from the three respective body regions. (B–E) FE-SEM images of caudal scales exposed to experimental aquaria with pH levels of 7.1, 7.5, 7.7, and 7.9, respectively. (G–J, L–O) Correspond to FE-SEM images of ventral scales and dorsal scales under identical pH treatments, respectively. FE-SEM, field emission scanning electron microscopy.

Figure 4

FE-SEM analysis of lepidont ultrastructures in scales from different body regions (caudal, ventral, dorsal). From left to right: FE-SEM images of the lepidont regions in scales from the caudal (tail), ventral (abdomen), and dorsal (back) regions of red seabream (P. major). (A, F, K) Untreated control scales from the three respective body regions. (B–E) Correspond to FE-SEM images of caudal scales subjected to experimental aquaria with pH levels of 7.1, 7.5, 7.7, and 7.9, respectively. (G–J, L–O) Also represent FE-SEM observations of ventral scales and dorsal scales under identical pH treatments, respectively. FE-SEM, field emission scanning electron microscopy.
FE-SEM analysis of lepidont ultrastructures in scales from different body regions (caudal, ventral, dorsal). From left to right: FE-SEM images of the lepidont regions in scales from the caudal (tail), ventral (abdomen), and dorsal (back) regions of red seabream (P. major). (A, F, K) Untreated control scales from the three respective body regions. (B–E) Correspond to FE-SEM images of caudal scales subjected to experimental aquaria with pH levels of 7.1, 7.5, 7.7, and 7.9, respectively. (G–J, L–O) Also represent FE-SEM observations of ventral scales and dorsal scales under identical pH treatments, respectively. FE-SEM, field emission scanning electron microscopy.

Figure 5

Box plot analysis of the aspect ratios of ctenii and lepidont ultrastructures in scales from different body regions (caudal, ventral, dorsal) under varying pH conditions. (A–C) Box plots of ctenii microstructure aspect ratios (length/width) for caudal, ventral, and dorsal scales at pH 7.1, 7.5, 7.7, and 7.9. (D–F) Box plots of lepidont microstructure aspect ratios (length/width) for caudal, ventral, and dorsal scales under the different pH conditions. Boxplot elements: Solid line = median; dashed line = mean; box limits = 1st and 3rd quartiles; whiskers = data within 1.5 × interquartile range.
Box plot analysis of the aspect ratios of ctenii and lepidont ultrastructures in scales from different body regions (caudal, ventral, dorsal) under varying pH conditions. (A–C) Box plots of ctenii microstructure aspect ratios (length/width) for caudal, ventral, and dorsal scales at pH 7.1, 7.5, 7.7, and 7.9. (D–F) Box plots of lepidont microstructure aspect ratios (length/width) for caudal, ventral, and dorsal scales under the different pH conditions. Boxplot elements: Solid line = median; dashed line = mean; box limits = 1st and 3rd quartiles; whiskers = data within 1.5 × interquartile range.

Seawater carbonate chemistry parameters at different pH levels_

MeasuredCalculated
pHNpHTTA (μmol kg–1)T (°C)S (PSU‰)pCO2 (μatm)ΩcalcΩarag
7.97.86 ± 0.052305.71 ± 255.7324.97 ± 0.4030.55 ± 0.79667.37 ± 117.963.55 ± 0.682.32 ± 0.44
7.77.67 ± 0.062269.71 ± 225.0824.96 ± 0.4430.21 ± 0.771100.05 ± 185.492.34 ± 0.51.53 ± 0.32
7.57.45 ± 0.052311.86 ± 235.1225.12 ± 0.4130.35 ± 0.761936.22 ± 307.071.5 ± 0.310.98 ± 0.2
7.37.26 ± 0.062368.09 ± 252.7424.97 ± 0.4330.71 ± 0.933075.08 ± 504.821.04 ± 0.270.68 ± 0.17
7.17.04 ± 0.102342.55 ± 411.4024.97 ± 0.4330.31 ± 1.205538.39 ± 1423.630.63 ± 0.210.41 ± 0.14
DOI: https://doi.org/10.26881/oahs-2025.1.29 | Journal eISSN: 1897-3191 | Journal ISSN: 1730-413X
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Language: English
Page range: 380 - 391
Submitted on: Jun 1, 2025
|
Accepted on: Dec 8, 2025
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Published on: Dec 31, 2025
Published by: University of Gdańsk
In partnership with: Paradigm Publishing Services
Publication frequency: 4 issues per year
Keywords:
fish scale,
bioindicator,
ocean acidification,
ultrastructure
Related subjects:
Chemistry,
Chemistry, other,
Geosciences,
Geosciences, other,
Life sciences,
Life sciences, other

© 2025 Weili Hou, Li Tian, Xin Sun, Xin Li, Xiangming Chen, Haijun Song, published by University of Gdańsk
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.

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