Highlights in BioScience
ISSN:2682-4043
DOI:10.36462/H.BioSci.202504

Research Article
Open Access

1 Laboratory of Ecology, Biology and Physiology

of Aquatic organisms, Department of biology,

Faculty of Science of Tunis, University of Tunis

El Manar, 2092 Tunis, Tunisia.
2 Basic Sciences departement, Physiology and

functional explorations section, Faculty of

Medicine of Tunis, Tunisia.

* To whom correspondence should be
addressed: safa.BEJAOUI@fst.utm.tn

Editor: Muhammad M. Adeel Arthritis Clinical
Immunology program Oklahoma Medical Research
Foundation, Oklahoma City, United States.

Reviewer(s): Sami Mili University of Carthage,
Higher Institute of Fisheries and Aquaculture of
Bizerte (ISPAB), Tunisia.

Chetoui Imene Laboratory of Ecology, Biology and
Physiology of Aquatic Organisms, Tunis Faculty
of Science, University of Tunis El Manar, Tunis-,
Tunisia.

Received: March 13, 2025

Accepted: July 02, 2025

Published: July 20, 2025

Citation: Bejaoui S, Ghribi F, Belhassen D, Trabelsi
W, Baati R, Soudani N. Projected climate change
scenarios and their effects on the nutritional quality
of P. segnis muscle: Macromolecular and fatty acid
transformations. 2025 July 20;8:bs202504

Copyright: © 2025 Bejaoui S et al.. This is an
open access article distributed under the terms of
the Creative Commons Attribution License, which
permits unrestricted use, distribution, and reproduc-
tion in any medium, provided the original author and
source are credited.
Data Availability Statement: All relevant data are
within the paper and supplementary materials.
Funding: This work was supported by the labora-
tory of Ecology, Biology and Physiology of Aquatic
organisms (UR18ES41), Faculty of Sciences, Uni-
versity of Tunis El Manar.
Competing interests: The authors declare that they
have no competing interests.

Projected climate change scenarios and their effects on the nutritional
quality of P. segnis muscle: Macromolecular and fatty acid
transformations

Safa Bejaoui*1
><�, Feriel Ghribi1

><�, Dalya Belhassen1
><�, Wafa Trabelsi1

>< �,
Rym Baati 2

><�, Nejla Soudani1,2
><�

Abstract

This work presents the effects of increasing temperature on the physiological changes
of Portunus segnis in natural environments (in situ) and under controlled conditions
(in vivo). Following the increase in temperature from 19oC to 30oC and 40oC,
physicochemical analyses showed that the percentages of oxygen consumption
increased and the quantities of dissolved oxygen decreased. Under the effect of natural
and controlled thermal stresses (19oC, 30oC and 40oC), the water and ash contents in
the muscles of blue crabs decreased with increasing temperature. For protein, glycogen
and lipid contents, a decrease was observed with increasing water temperature.
Saturated fatty acids (SFAs) significantly increased compared to polyunsaturated
fatty acids (PUFAs), mainly eicosapentaenoic acid (EPA) and docosahexaenoic acid
(DHA), which gradually decreased with increasing temperature. These results highlight
the need to closely monitor climate change, particularly temperature increases, due
to their potential impact on the structure and stability of biological macromolecules.
Such alteration can compromise essential physiological functions of aquatic organisms.
These findings open new avenues for future research aimed at better understanding
adaptation and resilience mechanisms to thermal stress in a warming climate.

Keywords: Portunus segnis, globl warming, temperature, macro-molecules, fatty acids

Introduction
The world’s oceans, representing nearly 71% of the Earth’s surface, are experiencing the effects

of pollution, eutrophication, and over-exploitation of their resources [1]. Moreover, this marine

environment plays a significant role in human society, as over 50% of the global population lives

within 60 km of the coast. On the other hand, oceans and seas constitute the largest source of

biodiversity on the planet [2]. Many human activities such as fishing, tourism, and aquaculture

depend on marine biodiversity and the overall health of seas and oceans, but these activities alter the

chemical composition of aquatic ecosystems [3]. It is highly probable, according to the commonly

accepted understanding by the intergovernmental panel on climate change, that the accelerating global

temperature rise since the late 1970s is a result of the increased concentration of greenhouse gases in

the atmosphere, such as carbon dioxide and methane, which have continued to rise [4]. The global

CO2 emissions level increased from 30.4 gigatonnes in 2010 to 33.3 gigatonnes in 2019. The increase

in emissions has led to a widespread reduction of the cryosphere (areas of the planet where water is

frozen), a continuous rise in ocean temperatures, a decrease in ocean pH and oxygen levels, changes

in currents, and an increase in extreme events such as heatwaves [5].

In addition to direct issues related to pollution, eutrophication, over-exploitation, and the invasion

of exotic species, the rise in carbon dioxide concentration and temperature poses a risk of causing

major modifications to biodiversity, structure, and functioning of marine ecosystems [6]. Climate

change poses a growing threat to marine ecosystems, directly affecting species distribution, physiology,

and population dynamics. Rising seawater temperatures disrupt the thermal tolerance limits of many

species, leading to geographical shifts toward the poles or to greater depths. The gradual rise in

Highlights in BioScience Page 1 of 8 July 2025|Volume 8

https://doi.org/10.36462/H.BioSci.202504
https://creativecommons.org/licenses/by/4.0/
mailto:safa.BEJAOUI@fst.utm.tn
https://orcid.org/0000-0002-7946-2763
mailto:feriel.ghribi@fst.utm.tn
https://orcid.org/0000-0001-9350-7510
mailto:dalyabelhassen@gmail.com
https://orcid.org/0009-0003-5518-1435
mailto:wafatrabelsi@gmail.com
https://orcid.org/0000-0002-1114-4080
mailto:Rym.baati@fmt.utm.tn
https://orcid.org/0000-0003-0138-1434
mailto:nejlasoudani@gmail.com
https://orcid.org/0000-0002-7652-9678
http://bioscience.highlightsin.org/


Bejaoui S et al., 2025 Change in P.segnis quality under warming conditions

ocean temperature is altering the environmental conditions
essential for the survival of marine organisms, causing range
shifts toward colder areas, mainly toward the poles or at depth
[7; 8]. Climate change is also influencing the physiology of ec-
tothermic species, reducing their metabolic performance, growth,
reproduction, and survival [9]. Increasingly frequent extreme
marine heat events, such as ocean heatwaves, are leading to mass
mortalities and local population collapses [10; 11]. These rapid
thermal changes often exceed the adaptive capacities of species,
particularly those with low mobility or a narrow ecological niche,
increasing the risk of local or global extinction.

It is urgent to place these systems under surveillance in order
to detect, better understand, and anticipate changes in biologi-
cal and ecological systems in the face of global climate change.
Climate warming is detected in numerous functional units of the
Earth’s system. The signature of warming is identified in the
ocean and the terrestrial and aquatic biosphere. Global tempera-
tures have risen by 0.76oC between the periods 1850-1899 and
2001-2005 [4]. This temperature increase has mainly affected the
oceans, which have absorbed 84% of the heat added to the climate
system over the last four decades [12]. The increase in heat stored
by the ocean has contributed to thermal expansion by 25% since
the 1950s [13]. The warming projected by ocean-atmosphere
general circulation models varies between 1.1oC (Scenario B1,
rapid introduction of efficient and clean technologies) and 6.4oC
(Scenario A1FI, intensive consumption of fossil carbon) by the
end of this century [4]. Indeed, the exposure of aquatic organ-
isms to higher temperatures could also reduce the metabolic rate,
decreasing physiological energy costs and providing short-term
tolerance above the critical temperature. Among the numerous
species affected by this phenomenon, crustaceans are consid-
ered significant fisheries in many countries, and the influence
of climate change poses a serious environmental and economic
threat.

Global climate change is perhaps the most concerning anthro-
pogenic impact currently, not only for the ocean but also for the
entire planet. These manifestations will directly act through the
effects of temperature on marine organisms. However, this distur-
bance will also indirectly influence marine ecosystems through
its impact on regional climate and hydrology (atmospheric oscil-
lation and ocean currents). Organisms’ responses will be differen-
tial, and abrupt and unexpected ecosystem balance changes are to
be feared. Despite existing uncertainties, our level of knowledge
is sufficient to urge policies to reduce greenhouse gas emissions
into the atmosphere and also to consider the other consequences
of human activities that go against sustainable development. Fur-
thermore, temperature and climate changes are considered the
most important abiotic factors for the biogeographical distribu-
tion, abundance, and communities of marine fish. In aquatic
environments, several studies also show a change in fish commu-
nities in response to climate changes. In fact, an increase in the
temperature of the living environment, beyond a tolerance limit
that varies by species, leads to the onset of physiological stress,

Figure 1. Experimental design for P. segnis exposure to increased temperature

especially pronounced when the exposure duration to this tem-
perature is long, and the species are already closer to their upper
thermal tolerance limit. If these stresses occur regularly, they can
lead either to changes in geographical distribution, modifications
in the life cycle, and in situ adaptations to new conditions, or, in
sessile or less mobile forms, to significant mortality accompanied
by epizootics and the substitution of affected species by others
more resistant [14]

Therefore, the set of physico-chemical changes induced by
climate change leads to the evolution of distribution areas, phe-
nology, migratory movements, abundance, and interspecific in-
teractions for many marine, freshwater, and terrestrial species
[7]. These modifications, of course, have repercussions on biodi-
versity and can significantly alter the appearance of underwater
landscapes. For this reason, we designed our study to determine
the effect of temperature on the physiology of blue crabs (Por-
tunus segnis). This current work focuses on the effect of increased
temperature on the biochemical composition of P. segnis. The
main objective is to analyze macromolecules (proteins, lipids,
and glycogens) as well as the fatty acid composition and the
nutritional quality of blue crab meat under controlled conditions.

Materials and methods
Samples and Experimental design

The individuals of blue crabs were collected from the Ghar
el Melh lagoon during the summer season. Once collected, the
specimens were immediately transported to the laboratory of the
Higher Institute of Fisheries and Aquaculture of Bizerte (ISPAB)
in a ventilated cooler. The specimens were acclimatized for three
days in a 200 L cylindro-conical basin, in a closed circuit, con-
taining filtered natural seawater, under continuous aeration and
under strictly controlled physicochemical conditions: tempera-
ture (19oC), oxygen content (62 µ g/L), salinity (35 psu), and
photoperiod (12 h/12 h), reproducing those of the sampling area.

After three days of acclimatization, the crabs were divided

Highlights in BioScience Page 2 of 8 July 2025|Volume 8

http://bioscience.highlightsin.org/


Bejaoui S et al., 2025 Change in P.segnis quality under warming conditions

into three tanks and subjected to different temperatures. For
the control group, specimens were exposed to an ambient tem-
perature of 19.81 ±0.14oC. In the second tank, the temperature
was raised to 30.18 ±0.36oC using a thermostat. Regarding the
third tank, two thermostats were installed to increase the tem-
perature to 40.03 ±0.56oC. The temperature gradually increased
to reach the desired values after approximately 2 hours of ther-
mostat installation. During the one week of the experiment, the
physicochemical parameters of the water, such as temperature
and dissolved oxygen levels, were measured daily (every 24
hours) using a multimeter Figure 1.

Crabs dissection and muscles preparation
After exposure to increasing temperature, each individual

from the crabs sampled from the natural environment and the
controlled condition was weighed (170.04 ±16.51 g), measured
using a caliper (60.44 ±6.51 mm), and subsequently dissected
with a scalpel. The muscles from each batch were carefully
extracted using forceps and weighed with a precision electronic
balance. The choice of the organ taken from individuals is based
on the fact that muscles are the edible tissues for living beings.

Table 1. Proximate composition of P. segnis muscle under increasing tempera-
ture

Parameter 19oC 30oC 40oC

Ash (%) 20.23 ±1.25a 19.98 ±1.45a 19.52 ±1.00a

Moisture (%) 80.00 ±2.82a 82.66 ±3.26a 80.66 ±3.26a

Protein (mg/g) 66.08 ±6.62a 62.49 ±7.90a 10.75 ±1.46c

Lipid (mg/g) 11.14 ±2.35a 11.82 ±2.56a 1.97 ±0.48c

Glycogen (mg/g) 2.03 ±0.25a 1.77 ±0.22b 0.37 ±0.07c

Note: Values are expressed as mean ±standard deviation. Different

superscript letters (a, b, c) in the same row indicate significant

differences between temperature conditions at the 0.5% level.

Determination of water, ash, and proximate composition content
Using an electronic balance, 0.5 g of crab muscle was weighed

to determine the initial wet weight. After drying in an oven at a
temperature of 105°C for 24 hours, the samples were weighed
again to determine the dry weight. To determine the ash content
in crab muscles, the AOAC method was employed [15]. In brief,
approximately 0.5 g of muscles were weighed and then dried at a
temperature of 400°C for 24 hours. Lipid analysis was performed
according to the method of [16], using vanillin solution. Glyco-
gen extraction was performed according to the enzymatic method
of [17], with glucose solution (100 mg/L). Protein determination

Figure 2. Temperature measurement in aquariums subjected to different

temperatures Note: The difference between C1 and C2, C3 is significant at

0.5%.

Figure 3. Measurement of dissolved oxygen in aquariums subjected to different

temperatures

was carried out according to the method of [18], using bovine
serum albumin as a standard.

Fatty acid composition analysis
Lipid extraction is a method for isolating these compounds

using organic solvents, including a mixture of chloroform and
methanol, according to the technique described by [19]. This
process consists of grinding 0.5 g of flesh in a mortar with 15 mL
of this mixture (2:1, v/v). In order to facilitate phase separa-
tion, 1 mL of sodium chloride (NaCl 15%) is then added to each
sample. The homogenate obtained is subjected to centrifuga-
tion at 4000 rpm for 15 minutes, thus allowing the separation of
the chloroform phase (containing the lipids) from the aqueous
phase. The lower phase, containing the lipid extract, is then
carefully recovered using a Pasteur pipette. From this extract,
20 µL are collected and placed in test tubes, to which 1 mL of
hexane, 500 µL of an internal standard (C19:0), 500 µL of sodium
methylate, 200 µL of sulfuric acid and 1.5 mL of sodium chloride
are added. After methylation, the tubes are centrifuged under the
same conditions, then the upper phase is recovered and stored

Highlights in BioScience Page 3 of 8 July 2025|Volume 8

http://bioscience.highlightsin.org/


Bejaoui S et al., 2025 Change in P.segnis quality under warming conditions

Figure 4. Oxygen consumption by P.segnis in aquariums subjected to different

temperatures

at −30 ◦C, according to the method of [20]. The identification
of fatty acids is based on the comparison of their retention times
with those of a reference mixture of methyl esters (SUPELCO
PUFA-3). The analysis of the chromatographic peaks is carried
out using HP ChemStation software, and the relative amount of
each fatty acid is expressed as a percentage of total fatty acids.
The calculation of the percentage of each group of fatty acids
(FA) was carried out according to the method of [21], using the
following formula: %FA = (FAA × 100) / (total FA), where %FA
corresponds to the relative surface area of a fatty acid (FAA)
expressed as a percentage of the total surface area of the fatty
acids detected.

Statistical analysis
The results of the biochemical parameters are expressed as

means ± standard error (SD). Statistical analysis of the data was
performed using R software (version 4.2.2), which was also used
to generate the illustrative graphs. The normality of the distribu-
tion was checked by the Shapiro–Wilk test. A one-way analysis
of variance (ANOVA) was then performed, followed by the Tukey
test to identify significant differences between the means of the
control and experimental groups. The significance threshold was
set at 0.05. Finally, a correlation matrix was established to assess
the significance of the Pearson correlation coefficients.

Results
Temperature and oxygen variation during the experiment

During the experiment, the temperature of the ponds was
measured every 24 hours Figure 2. The control pond maintained
a stable temperature of 19.81 ± 0.14 oC, whereas the ponds
exposed to elevated temperatures reached significantly higher
values of 30.18 ± 0.36 oC and 40.03 ± 0.56 oC, respectively
(p < 0.001). Dissolved oxygen levels followed a similar pattern
Figure 3, with the control pond showing 10.8 mg/L, while the

Figure 5. Correlation matrix illustrates the relationships between essential

fatty acids and the biochemical composition of P. segnis subjected to different

temperatures

ponds at 30 oC and 40 oC recorded 10.18 mg/L and 9.8 mg/L,
respectively. Furthermore, oxygen consumption increased with
prolonged exposure to higher temperatures Figure 4. A signif-
icant rise in oxygen consumption was observed in the tanks at
30 oC and 40 oC compared to the control at 19 oC, with consump-
tion doubling in all tanks within the first 24 hours.

Water, ash, protein, lipid, and glycogen content
As shown in Table 1, water and ash contents exhibited sim-

ilar trends across all temperature groups, with no statistically
significant differences detected. In contrast, protein content
varied significantly, with higher values observed in crabs ex-
posed to 19 oC (66.08 mg/g) and 30 oC (62.49 mg/g), while
a markedly lower protein concentration was recorded at 40 oC
(10.75 mg/g) (p < 0.001). Lipid analysis revealed that crabs
exposed to 40 oC had the lowest lipid levels (1.9 mg/g), whereas
significantly higher concentrations were measured in crabs from
the 19 oC and 30 oC groups (p < 0.001). Similarly, glycogen
content was highest in the control group at 19 oC (2.03 mg/g),
followed by the 30 oC group (1.77 mg/g), and was significantly
reduced in crabs exposed to 40 oC (0.37 mg/g) (p < 0.001).

Fatty acid composition
Table 2 presents the fatty acid composition of P. segnis mus-

cles exposed to temperatures of 19 oC, 30 oC, and 40 oC. Our
results show that crabs exposed to 30 oC and 40 oC had signif-
icantly higher contents of saturated fatty acids (SFA), reaching
43.64 ± 2.64% and 75.50 ± 1.15%, respectively, compared to
the control group at 19 oC (p < 0.001). This increase is mainly
attributed to the rise in the major fatty acids C16:0 and C18:0,
which reached 33.71 ± 0.007% and 5.843 ± 0.013% at 30 oC,
and 63.82 ± 1.28% and 9.66 ± 0.02% at 40 oC, respectively.

Highlights in BioScience Page 4 of 8 July 2025|Volume 8

http://bioscience.highlightsin.org/


Bejaoui S et al., 2025 Change in P.segnis quality under warming conditions

Figure 6. Principal component analysis (PCA), performed using two factors (F1

= 57.4% and F2 = 24.4%), allowed us to examine the variations of biochemical

parameters (ash, humidity, lipids, proteins, carbohydrates) and essential fatty

acids in the muscle of P. segnis subjected to different temperatures

Exposure to higher temperatures also resulted in a significant
reduction in monounsaturated fatty acids (MUFAs) in crabs ex-
posed to 30 oC compared to those maintained at 19 oC and 40 oC
(p < 0.01). Crabs exposed to 40 oC showed the lowest concentra-
tions of C16:1 and C20:1 and the highest concentration of C18:1
compared to the 19 oC and 30 oC groups (p < 0.05).

Polyunsaturated fatty acids (PUFAs) varied significantly be-
tween temperature groups. The control group (19 oC) exhibited
a high PUFA content (80.53%), which was significantly greater
than those observed at 30 oC and 40 oC (p < 0.001). A simi-
lar trend was found for omega-3 and omega-6 fatty acids, with
higher percentages in the muscles of crabs maintained at 19 oC
compared to those exposed to 30 oC and 40 oC (p < 0.05). This
was confirmed by the high concentrations of docosahexaenoic
acid (DHA, 39.99%) and eicosapentaenoic acid (EPA, 31.65%)
in the 19 oC group, which significantly decreased in the muscles
of crabs at higher temperatures (p < 0.01). Finally, arachidonic
acid (ARA) showed an opposite trend, with significantly lower
concentrations in crabs exposed to 19 oC compared to those at
30 oC and 40 oC (p < 0.001).

Correlation and Principal Component Analysis
The Pearson correlation coefficient matrix highlights the re-

lationships between the levels of biochemical composition and
the main fatty acids present in P. segnis muscle under differ-
ent temperature exposures. A significant positive correlation
(p < 0.05) was observed between essential fatty acids, proteins,
and glycogen, with coefficients greater than 0.62. Conversely,
monounsaturated fatty acids (MUFAs) showed a negative correla-

tion with glycogen (r = −0.54), lipids (r = −0.66), water content
(r = −0.36), and ash content (r = −0.46). Furthermore, an in-
crease in arachidonic acid (ARA) and saturated fatty acid (SFA)
levels appeared to be associated with a reduction in essential fatty
acids, as evidenced by a strong negative correlation (r < −0.85),
also illustrated in Figure 5.

Each cell of the matrix represents the Pearson correlation
coefficient (r) for a pair of parameters. Positive correlations
(0 < r < 1.0) are shown in blue, while negative correlations
(−1.0 < r < 0) are shown in red. The intensity of the colors
corresponds to the absolute values of the correlation coefficients.
Statistical significance is indicated as follows: *p < 0.05, **p <
0.01, ***p < 0.001; values not statistically significant (p > 0.05)
are represented by a checkbox symbol.

Principal component analysis (PCA) biplot was employed to
analyze the variation in measured parameters in P. segnis muscle
samples exposed to different temperatures Figure 6. The first
two principal components explained 81.8% of the total variance,
with PC1 contributing 53.6% and PC2 26.6%. This analysis
revealed a clear separation between the groups of crabs subjected
to 30 oC and 40 oC compared to those exposed to 19 oC. The
19 oC group was associated with high levels of lipids, glycogen,
DHA, PUFA omega-3, and EPA. In contrast, the 30 oC and 40 oC
groups showed strong associations with elevated SFA, ARA, ash,
omega-6, and moisture contents.

Discussions
Climate change, which occurs over time through natural vari-

ability, is also exacerbated by human activity. These activities,
responsible for the increase of greenhouse gases in the atmo-
sphere, have led to an increase in water temperatures. The impact
of climate change represents a serious environmental threat to
fisheries, especially to economically exploited species, such as
crabs. Indeed, temperature, as a major abiotic factor, signifi-
cantly influences the biochemical, metabolic and physiological
processes of these species [22]. Studies have shown that natural
temperature variation can induce alterations in the fish Carassius
auratus [23], indicating that the increase in temperature generates
molecular stress and increased energy demand, probably explain-
ing the decrease in the organism’s energy reserves. In addition, it
has been reported that increased temperature causes molecular
disruptions in proteins, lipids, and fatty acids in fish [24].

With this knowledge, an in vivo study was conducted to as-
sess the effects of increased temperature on the physiology and
biochemical composition of ectothermic organisms. Analyses
of the biochemical composition of muscles, after exposure to
elevated temperatures, revealed a decrease in protein and lipid
contents compared to the control group. Similar results were
reported for the blue swimmer crab, P. pelagicus, where an el-
evated temperature of 30 °C affected the protein content [25].
Similarly, it was shown that increased temperature alters lipids
in Carassius auratus [26]. These decreases can be explained by
the energy production resulting from the complete oxidation of

Highlights in BioScience Page 5 of 8 July 2025|Volume 8

http://bioscience.highlightsin.org/


Bejaoui S et al., 2025 Change in P.segnis quality under warming conditions

Table 2. Fatty acid composition of P. segnis muscle under increasing temperature

Fatty Acid 19oC 30oC 40oC

C16:0 5.760 ±0.106 33.712 ±0.007*** 63.829 ±1.287***###

C18:0 1.001 ±0.044 5.843 ±0.013*** 9.661 ±0.022*##

C20:0 3.136 ±0.069 4.090 ±0.000** 1.019 ±0.148***###

SFA 9.898 ±0.220 43.645 ±2.639*** 74.509 ±1.159***#

C16:1 4.649 ±0.052 0.239 ±0.004*** 1.198 ±0.154***##

C18:1 0.073 ±0.014 2.380 ±0.002*** 9.661 ±0.022***###

C20:1 4.841 ±0.059 3.860 ±0.001*** 1.019 ±0.148***#

MUFA 9.563 ±0.126 6.479 ±0.768** 11.878 ±0.279**##

C18:3n3 0.759 ±0.046 0.796 ±0.001 2.186 ±0.156**##

C20:5n3 31.657 ±0.180 26.800 ±0.003*** 5.456 ±0.056***###

C22:6n3 39.995 ±0.362 15.810 ±0.003*** 0.993 ±0.162***#

Omega-3 72.411 ±0.496 43.406 ±2.031*** 8.635 ±0.375***#

C18:2n6 5.472 ±0.052 4.510 ±0.002*** 1.688 ±0.161***##

C18:3n6 1.994 ±0.101 0.492 ±0.002*** 0.241 ±0.197**

C20:4n6 0.658 ±0.004 1.462 ±0.000*** 2.972 ±0.144**##

Omega-6 8.125 ±0.149 6.464 ±1.009** 4.901 ±0.503**

PUFA 80.537 ś 0.346 49.871 ś 2.756*** 12.938 ś 0.879***#

Note: Results are presented as means ±standard deviation. Significant differences in saturated fatty acids between: 19 oC vs 30 oC and

19 oC vs 40 oC are denoted by: p < 0.001 ***, and between 30 oC vs 40 oC by: p < 0.05. For monounsaturated fatty acids, significant

differences between: 19 oC vs 30 oC and 19 oC vs 40 oC are denoted by: p < 0.01 **, and the difference between 30 oC vs 40 oC is indicated

by: p < 0.05 #. Regarding polyunsaturated fatty acids, significant differences between: 19 oC vs 30 oC and 19 oC vs 40 oC are noted by: p <

0.001 ***, and between 30 oC vs 40 oC by: p < 0.05 #.

macromolecules in response to temperature variations. Concern-
ing glycogen contents, a highly significant decrease was observed
with increasing water temperature. The study by [27], on glyco-
gen concentrations and agonistic behavior of swimming crab
(Portunus trituberculatus) subjected to temperatures of 16 °C,
24 °C and 32 °C, shows that glycogen concentrations decrease as
temperature increases.

Higher temperatures enhance ROS production and conse-
quently increase the risk of lipid peroxidation [28]. This hypoth-
esis was observed in our work through the alteration of fatty
acid composition of P. segnis subjected to different temperatures.
Fatty acid analyses revealed that in response to heat stress, sat-
urated and monounsaturated fatty acids significantly increase,
while polyunsaturated fatty acids decrease in the muscles of
crabs exposed to high temperatures. Heat stress is well estab-
lished as a factor with physiological repercussions on poikilother-
mic organisms, eliciting a series of adaptive cellular responses.
Among these, one of the most notable is the modification of
membrane lipid composition, particularly through FA remodel-

ing. This process involves changes in the proportions of SFA
and UFA fatty acids, as well as changes in carbon chain length,
with an increased predominance of SFA, or longer chains, in
response to temperature elevation, to counterbalance the increase
in membrane fluidity. For example, alterations in polyunsatu-
rated fatty acids, mainly DHA and EPA, were observed in the
gastropod Lymnaea [29]. Similarly, in Trematomus bernacchii,
increased temperature induced lipid remodeling, with a decrease
in C18:3n-3 and C22:6n-3 fatty acids [30]. Similar results have
been reported in different bivalves where warming caused marked
modifications in their fatty acid profiles illustrated by the deple-
tion of essential FA such as DHA and EPA [31]. In our study, the
observed changes in fatty acid profiles indicate an adjustment in
lipid metabolism. Although significant changes were noted in the
proportions of some fatty acids, the strong alterations observed in
our analysis suggest that P. segnis is relatively affected by an in-
crease in temperature of 30 and 40 °C and manages to deteriorate
its lipid composition, indicating its high thermal sensitivity.

In general, the multivariate analysis, particularly the Princi-

Highlights in BioScience Page 6 of 8 July 2025|Volume 8

http://bioscience.highlightsin.org/


Bejaoui S et al., 2025 Change in P.segnis quality under warming conditions

pal Component Analysis (PCA) performed on the entire dataset,
clearly highlighted distinct patterns associated with increasing
thermal stress. The PCA revealed a clear clustering of the physi-
ological responses of Portunus segnis across different tempera-
ture treatments in vivo, consistently separating the effects of low
(19 °C), moderate (30 °C), and high (40 °C) temperatures. This
separation underscores the substantial impact of temperature on
key biochemical parameters such as protein, lipid, glycogen, and
fatty acid profiles. The discriminative power of PCA not only
confirms the robustness of the observed trends but also empha-
sizes the high sensitivity of this species to thermal fluctuations.
The results obtained clearly indicate that proteins and lipids play
a crucial role in the metabolic mechanisms that enable organisms
to cope with thermal stress, while changes in fatty acid com-
positionparticularly the decrease in polyunsaturated fatty acids
such as EPA and DHAcan be considered reliable indicators of
thermal variation in aquatic organisms. This study confirms that
global warming significantly affects the physiological state and
biochemical composition of P. segnis under both natural and ex-
perimental temperature conditions. From a practical perspective,
these findings provide valuable insights for aquaculture stake-
holders, including breeders and shellfish farmers, by identifying
physiological thresholds and stress markers essential for moni-
toring the health and viability of crustacean stocks. Furthermore,
this work supports the development of adaptive and sustainable
management strategies in response to climate-induced thermal
stress, thus contributing to the long-term resilience and produc-
tivity of benthic resources.

Conclusions
This study investigates the effects of elevated temperatures

on the physiological and biochemical responses of the blue crab
(Portunus segnis) under in vivo conditions, following a three-day
exposure to thermal stress. The analysis focused on key bio-
chemical parameters in muscle tissue, including moisture, ash,
protein, lipid, glycogen, and fatty acid composition. The results
yielded several noteworthy findings. After 72 hours of exposure
to high temperatures, no significant differences in water and ash
content were observed compared to the control group. However,
a marked decrease in glycogen, protein, and lipid levels was
recorded with increasing temperature, indicating altered energy
metabolism. In terms of fatty acid composition, a significant
rise in saturated and monounsaturated fatty acids was detected,
while polyunsaturated fatty acids, particularly those essential for
maintaining membrane fluidity, decreased substantially. Physic-
ochemical measurements also showed a reduction in dissolved
oxygen levels in the rearing tanks, alongside an increase in oxy-
gen consumption, pointing to elevated metabolic demand and
thermal stress. Overall, these findings enhance our understanding
of the physiological and biochemical responses of P. segnis to
thermal variation and underscore the potential impacts of global
warming on aquatic organisms, particularly regarding biochemi-
cal degradation and metabolic disruption.

Reference
1. Halpern B, Frazier M, Potapenko J, Casey K, Koenig K,

Longo C, et al. Spatial and temporal changes in cumulative
human impacts on the worlds ocean. Nature Communica-
tions. 2015;6(7615):1000-38.

2. Palmer CP. Marine Biodiversity and Ecosystems Underpin a
Healthy Planet and Social Well-Being; 2017.

3. Weatherdon LV, Magnan AK, Rogers AD, Sumaila UR, Che-
ung WWL. Observed and Projected Impacts of Climate
Change on Marine Fisheries, Aquaculture, Coastal Tourism,
and Human Health: An Update. Frontiers in Marine Science.
2016;3:48.

4. Masson-Delmotte V, Zhai P, Pörtner H, Roberts D, Skea J,
Shukla P, et al. GIEC Bilan 2007 des changements clima-
tiques. Contribution des Groupes de travail I, II et III au
quatrième Rapport dévaluation du Groupe dexperts intergou-
vernemental sur lévolution du climat. Suisse: GIEC Genève;
2007.

5. Intergovernmental Panel on Climate Change (IPCC). IPCC
Fourth Assessment Report: Synthesis Report; 2007. Ac-
cessed: 2025-07-15. https://www.ipcc.ch/report/
ar4/syr/.

6. Verma AK, Rout PR, Lee E, Bhunia P, Bae J, Surampalli RY,
et al. Sustainability: Fundamentals and Applications. In:
Biodiversity and Sustainability. Wiley; 2020. .

7. Poloczanska ES, et al. Responses of marine organisms to
climate change across oceans. Frontiers in Marine Science.
2016;3:62.

8. Cheung WWL, Pauly D. Impacts of climate change on
marine biodiversity and fisheries. Nature Reviews Earth &
Environment. 2023;4(3):160-73.

9. Pörtner HO, et al.. Scientific outcome of the IPCC AR6
Working Group II: Climate Change 2022 Impacts, Adap-
tation and Vulnerability; 2021. https://www.ipcc.ch/
report/ar6/wg2/.

10. Smale DA, et al. Marine heatwaves threaten global biodiver-
sity and the provision of ecosystem services. Nature Climate
Change. 2019;9(4):306-12.

11. Laufkötter C, et al. Projected impacts of ocean warming
on marine species biomass and ecosystem structure. Global
Change Biology. 2020;26(2):1305-18.

12. Cheng L, Abraham J, Trenberth KE, et al. Upper Ocean
Temperatures Hit Record High in 2020. Advances in Atmo-
spheric Sciences. 2021;38:523-30.

Highlights in BioScience Page 7 of 8 July 2025|Volume 8

https://www.ipcc.ch/report/ar4/syr/
https://www.ipcc.ch/report/ar4/syr/
https://www.ipcc.ch/report/ar6/wg2/
https://www.ipcc.ch/report/ar6/wg2/
http://bioscience.highlightsin.org/


Bejaoui S et al., 2025 Change in P.segnis quality under warming conditions

13. Cheng L, von Schuckmann K, Abraham JP, et al. Past and fu-
ture ocean warming. Nature Reviews Earth and Environment.
2022;3:776-94.

14. Intergovernmental Panel on Climate Change (IPCC). Cli-
mate Change 2022: Impacts, Adaptation and Vulnerabil-
ity. Contribution of Working Group II to the Sixth Assess-
ment Report of the IPCC; 2022. Accessed: 2025-07-15.
https://www.ipcc.ch/report/ar6/wg2.

15. AOAC. Official Methods of Analysis. Association of Official
Analytical Chemists; 1990. Food and Nutrition Sciences,
14(7), 1364–1374.

16. Frings C, Fendley T, Dunn R, Queen C. Improved Determi-
nation of Total Serum Lipids by the Sulfo-Phospho-Vanillin
Reaction. Clinical Chemistry. 1972;18(7):673-4.

17. Dubois M, Gilles K, Hamilton J, Rebers P, Smith F. Col-
orimetric Method for Determination of Sugars and Related
Substances. Analytical Chemistry. 1956;28(3):350-6.

18. Lowry OH, Rosebrough NJ, Farr AL, Randall RJ. Protein
measurement with the Folin phenol reagent. Journal of
Biological Chemistry. 1951;193:265-75.

19. Folch J, Lees M, Stanley GHS. A simple method for the
isolation and purification of total lipids from animal tissues.
Journal of Biological Chemistry. 1957;226:497-509.

20. Cecchi G, Basini S, Castano C. Méthanolyse rapide des
huiles en solvant. Note de laboratoire. Revue Française des
Corps Gras. 1985;4:163-4.

21. Visentainer JV, Claus T, Santos Jr OO, Chiavelli LUR,
Maruyama SA. Analytical Aspects of the Flame Ioniza-
tion Detection in Comparison with Mass Spectrometry with
Emphasis on Fatty Acids and Their Esters. In: Guo X, edi-
tor. Advances in Gas Chromatography. IntechOpen; 2013. p.
224.

22. Ren X, Wang Q, Shao H, Xu Y, Liu P, Li J. Effects of
Low Temperature on Shrimp and Crab Physiology, Behav-
ior, and Growth: A Review. Frontiers in Marine Science.
2021;8:746177.

23. Sokolova IM. Energy-limited tolerance to stress as a concep-
tual framework to integrate the effects of multiple stressors.
Integrative and comparative biology. 2013;53(4):597-608.

24. Fadhlaoui M, Couture P. Combined effects of temperature
and metal exposure on the fatty acid composition of cell
membranes, antioxidant enzyme activities and lipid peroxida-
tion in yellow perch (Perca flavescens). Aquatic Toxicology.
2016. S0166445X1630251X.

25. Sugumar V, Vasu P. Effect of temperature on the biochemical
constituents of the blue swimmer crab Portunus pelagicus.
World Applied Sciences Journal. 2013;28(3):382-91.

26. Bagnyukova TV, Lushchak OV, Storey KB, Lushchak VI.
Oxidative stress and antioxidant defense responses by gold-
fish tissues to acute change of temperature from 3 to 23řC.
Journal of Thermal Biology. 2007;32(4):227-34.

27. Xianpeng S, Yunfei S, Dapeng L, Fang W, Jingjing L, Boshan
Z. Agonistic behaviour and energy metabolism of bold and
shy swimming crabs Portunus trituberculatus. Journal of
Experimental Biology. 2019;222(3):188706.

28. Bejaoui S, Trabelsi W, Chetoui I, Ghribi F, Fouzai C, Soltani
A, et al. Assessment of trace elements uptake on the invasive
crab Portunus segnis hepatopancreas using a multivariate
biochemical approach. Humanities and Social Sciences.
2021;1(1):131-51.

29. Fadhlaoui M, Lavoie I. Effects of Temperature and
Glyphosate on Fatty Acid Composition, Antioxidant Ca-
pacity, and Lipid Peroxidation in the Gastropod Lymnaea sp.
Water. 2021;13(8):1039.

30. Truzzi C, Illuminati S, Antonucci M, Scarponi G, Annibaldi
A. Heat shock influences the fatty acid composition of the
muscle of the Antarctic fish Trematomus bernacchii. Marine
environmental research. 2018;139:122-8.

31. Pernet F, Tremblay R, Comeau L, Guderley H. Temperature
adaptation in two bivalve species from different thermal
habitats: energetics and remodelling of membrane lipids.
Journal of Experimental Biology. 2007;210(17):2999-3014.

Highlights in BioScience Page 8 of 8 July 2025|Volume 8

https://www.ipcc.ch/report/ar6/wg2
http://bioscience.highlightsin.org/

	Abstract
	Introduction
	Materials and methods
	Samples and Experimental design
	Crabs dissection and muscles preparation
	Determination of water, ash, and proximate composition content
	Fatty acid composition analysis
	Statistical analysis

	Results
	Temperature and oxygen variation during the experiment
	Water, ash, protein, lipid, and glycogen content
	Fatty acid composition
	Correlation and Principal Component Analysis

	Discussions
	Conclusions