Morphological asymmetry in two marine fish species  (Family: Sparidae) and  (Family: Mugilidae), collected from brackish and freshwater environments in southern Iraq

Environmental degradation can create noticeable changes in the biology of individuals and populations, possibly resulting in the extirpation of species (Koprivnikar et al. 2006). Additional indirect effects may result in decreased growth, increased disease vulnerability, and more significant morphological deformities (Jawad & Abed 2020). Rapid alerts to such negative impacts allow scientists and resource administrators to adopt corrective actions that may prevent additional habitat degradation and population failures.

One morphological characteristic associated with habitat changes and environmental impact is fluctuating asymmetry, defined as the arbitrary divergence from normal bilateral symmetry (Van Valen, 1962). The homeostatic regulation of morphological development may be adversely affected when individuals are subjected to either anthropogenic or natural impacts, which may be reflected in the development of bilateral asymmetry. Although no bilateral characters are perfectly symmetric, higher levels of asymmetry may result when organisms are subjected to various environmental impacts during their developmental process (Allenbach 2011). Asymmetry levels may also be affected by biological activities that individuals are subjected to, such as inbreeding (e.g., Leamy & Klingenberg 2005). Quantifying disparities in morphological traits represents a cheap method for defining the overall health rank of populations (Jawad & Abed 2020).

Pollution is reported to be the causative agent for several cases of skeletal deformities in fishes (Härdig et al. 1988). Pollutants can produce abnormal changes in the skeletal system of the fish in two ways, (1) by alteration of the biological processes necessary for maintaining the biochemical integrity of bone, or (2) through neuromuscular effects, which lead to deformities without a chemical change in vertebral composition (Raj et al. 2004). Trace elements such as cadmium and mercury can decrease collagen synthesis (Bhatnager & Hussain 1977). Arsenic binds certain enzymatic sulfhydryl groups, acting as a protoplasmic poison (Luh et al. 1973). Cadmium inhibits the cross-linking (i.e., stiffening) of collagen. It causes pathological bone changes that probably lead to the altered structural integrity of bone (Iguchi and Sano 1982) and reduced proline hydroxylation and collagen biosynthesis (Vistica et al. 1977). Pollutants might also act indirectly, increasing susceptibility to diseases and vertebral damage.

Oil is one source of trace metal pollution in the aquatic environment. Although oil dispersants make oil more bioavailable to oil-eating bacteria (Redmond & Valentine 2012), their short and long-term effects on marine flora and fauna have not been adequately elucidated (White et al. 2012). Rico-Martínez et al. (2013) measured the acute toxicity of dispersed crude oil on rotifers. They found that the combination of oil and dispersant produces higher toxicity than the use of only a single compound at a time (Ralph & Burchett 1998).

The Arabian yellowfin seabream, A. arabicus, is a marine pelagic-neritic species generally found at depths down to 50 m (Randall 1995) and ranging from southern Kuwait in the Arabian Gulf southwards to Trivandrum in southwestern India (Iwatsuki 2013) and from Iranian shorelines of the Gulf (Esmaeili et al. 2015). However, several studies have recorded the occurrence of A. arabicus from different locations in the freshwater systems of Iraq (Yesser 2016). The leading food of this species is echinoderms, worms, crustaceans, and molluscs (Bauchot & Smith 1984). Klunzinger’s Mullet, P. klunzingeri, is generally found in marine demersal habitats ranging from the Arabian Gulf to the western coast of India (Randall 1995). However, the species has also been collected from several locations in the freshwater systems of Iraq (Mohamed and Abood 2017). A. arabicus and P. klunzingeri were selected for the current study because they are commonly found in marine and brackish water environments.

The current investigation aimed to assess the levels of bilateral asymmetry in two common marine fish species found in brackish and freshwater environments in southern Iraq, A. arabicus and P. klunzingeri. The two locations chosen for this investigation are proved to be heavily polluted (Al-Hejuje et al. 2017, Hassan et al. 2018, Zahraw et al. 2019, Allafta and Opp 2020). Therefore, they are suitable for the asymmetry study.

Materials and methods

2.1.

Fish specimens

The Shatt al-Arab River and Shatt al-Basrah Canal are well known to be heavily polluted (Al-Saad et al 2015, Al-Hejuje et al. 2017, Hassan et al. 2018) and were therefore selected for the present study. A total of 200 fish specimens of A. arabicus and P. klunzingeri (Fig. 1) were collected from a fisher operating in the Shatt al-Basrah Canal (brackish water environment) and Shatt al-Arab River (freshwater environment), including 50 specimens for each species from each location (Fig. 2). The fish were taken in gillnets (200 m × 1.30 m, 25-, 40 and 50 mm mesh) at a depth of 12 m between January and September 2018. Water samples were also taken from the same locations.

A) Acanthopagrus arabicus (176 mm TL) collected from Shatt al-Arab River; B) Planiliza klunzingeri (180 mm TL) collected from Shatt al-Arab River

2.2.

Water samples

Since fish live in water, they directly react with this environment which also provides the food that enters their body and is metabolised (Yavuzcan et al. 2017). Therefore, water sampling was selected to indicate pollution in the studied areas. Before use, 5% nitric acid was added to the water sampling bottles and thoroughly washed with distilled de-ionised water. Al-Saad et al. (2015) followed the method for water sampling. Polyethene sampling bottles have been washed at least three times before sampling at each site. Clean polyethylene containers were dipped about 10 cm underneath the water surface. Approximately 0.5 l of water samples were taken at each station. Samples were acidified with 10% HNO₃, cooled with ice on-site, and transported to the laboratory, where they were filtered through a 0.45 μm micropore membrane filter and retained at 4°C pending analysis.

2.3.

Sediment samples

As with water, sediment is considered a good indicator of the pollution load at a given location (Hahladakis et al. 2013). Consequently, samples of sediment were collected from the studied areas. Sediment samples were obtained using a grab sampler. They were taken to the laboratory and kept firmly closed at room temperature. Later, sediment samples were crushed and filtered through a 160 μm sieve. The sieved samples were packed in polyethylene bags and stored below -20°C before analysis. Samples were weighed, positioned into digestion bombs with 10 ml of HNO₃/HCl (1:3 v/v), and digested in a microwave digestion system. Sediment analysis was carried out according to the methodology of Binning & Baird (2001).

2.4.

Chemical analysis

Fish specimens were taken directly to the laboratory after being caught and kept on ice during the journey. The total length and weight of the fish were noted. All specimens were held at -30°C until analysis. The method of Bernhard (1976) was followed in the preparation and analysis of the fish samples. Before analysis, muscle tissues taken from the area above the pectoral fin were removed and whipped in a mixer, and one gram of the mixed material was digested. A microwave digestion system (CEM Mars 5 ESP 1500 PLUS) was utilised to prepare the specimens for analysis. Recently, microwave digestion procedures have frequently been used in investigations (Kucuksezgin et al. 2001), which involve rapid digestion and fewer chances of impurity throughout the process. Muscle tissues (without skin) were mixed with 5 ml HNO₃ (65%) and 5 ml H₂SO₄ in polypropylene vials. After 10 minutes of mixing, 1 ml H₂O₂ was added, and samples were placed in a microwave (1 hour at 105°C). After digestion, the residues were diluted to 25 ml with HNO₃ (0.3%)

Fe, Cu, Pb, Cr, Ni, and Cd were detected in all samples using ICP–AES (Varian-Terra Model Liberty II). Identification limits are summarised in Table 1. These limits represent the lowermost analytical levels differentiated regarding quality at a definite assurance value from background levels. The accuracy of the analytical method was tested by analysing comparable standard samples (water: SRM-143d, National Institute of Standards and Technology; sediment: CRM-277, Community Bureau of Reference; fish: DORM-2, National Research Council). Recovery rates ranged from 79 to 96% for all components analysed.

Table 1

Spectral lines used in emission measurements and the instrumental detection limit for the elements measured by using ICP–AES

Element	Wave length (nm)	Instrumental detection limit (μg l^-1)
Cd	227.9	0.001
Cr	268.7	0.006
Cu	325.9	0.013
Fe	258.6	0.07
Ni	230.7	0.05
Pb	221.5	0.05

2.5.

Statistical analysis

The body features (Fig. 3) assessed for bilateral asymmetry in the current investigation were previously used in earlier reports (Jawad et al. 2010, 2016; Hechter et al. 2000). These morphological characteristics were proved to be quickly affected by environmental factors such as pollution (Jawad et al. 2010). The characters assessed included external features (4 characters) and meristic traits (2 features): (1) snout length (SnL); (2) eye diameter (ED); (3) head length (HL); (4) caudal peduncle length (CPL); (5) number of the lateral line scales (LLS); and (6) number of pectoral fin rays (PFR). External body features were computed to the nearest 0.1 cm using digital callipers. Lateral line scales were counted for A. arabicus only, as there is no lateral line in the mugilid species P. klunzingeri. To avoid possible computation errors, all measurements were completed by the same person. The square coefficient of asymmetry variation (CV² a) for meristic and morphometric traits was assessed (Valentine et al. 1973) as follows: ${CV}^{2} a = S_{l - r} X 100 / x_{l + r}$ $${\rm{C}}{{\rm{V}}^2}{\rm{a}} = {{\rm{S}}_{l - r}}{\rm{X}}100/{x_{l + r}}$$

In the equation, we see this: S_l–r is the standard deviation of the signed variance, and X_l+r is the character’s mean, computed by totalling the absolute scores for both sides and dividing by the sample size. To remove variation related to growth in external traits (non-discrete, measurable), the body’s external attributes were divided by a predictable standardising measurement (head length, from the mouth to the posterior edge of the operculum). Every external feature was dealt with similarly, and the squared coefficient of asymmetry was determined. The ANOVA test evaluated the coefficients of asymmetry between the diverse total length groups. Further to the ANOVA test, a Tukey HSD post hoc test was used to assess whether the alterations were significant between couple assessments of length groups (StatSoft, Inc., 1991). Fish specimens were categorised into ranks for every character examined based on their total length. Three- and four-size ranks of fishes of both species were collected from both sampling sites. Coefficients of asymmetry were compared between the fish groups of each species and the collaborative groups using ANOVA tests.

Results

Table 2 summarises the water quality constituents at the two sampling sites compared with reference freshwater values. Heavy metal concentrations in the waters of the Shatt al-Arab River and Shatt al-Basrah Canal were reduced in the sequence of Fe > Cu > Pb > Cr > Ni > Cd.

Table 2

The heavy metal concentrations in the waters of the Shatt al-Arab River and Shatt al-Basrah Canal and comparison with guidelines and different literature (Mean ± SD) (mg l^-1)

Location	Cd	Cr	Cu	Fe	Ni	Pb	Reference
Shatt al-Arab River	0.02 ± 0.002	0.009 ± 0.005	0.01 ± 0.001	0.9 ± 0.4	0.004 ± 0.002	0.03 ± 0.007	Present study
Shatt al-Basrah Canal	0.02 ± 0.012	0.059 ± 0.004	0.01 ± 0.003	0.89 ± 0.95	0.059 ± 0.006	0.025 ± 0.007	Present study
Shatt al-Arab River	3.01	-	2.35	89.45	9.51	7.58	Al-Hejuje et al. 2017
WHO	0.01	0.05	2	-	0.02	0.05	WHO, 1993
EC	5	50	2	0.2	20	10	EC, 1989

Table 3 summarises the total concentrations of metals in the sediment samples at the two sampling sites compared with other sediments estimates that have been published worldwide. Heavy metal concentrations in the sediments of the Shatt al-Arab River and Shatt al-Basrah Canal were reduced in the sequence of Fe > Ni > Cu > Cr > Pb > Cd.

Table 3

The heavy metal concentrations in the Shatt al-Arab River and Shatt al-Basrah Canal sediments and comparison with sediment quality guideline and different literature (Mean ± SD) (mg kg^-1 dry weight)

Location	Cd	Cr	Cu	Fe	Ni	Pb	Reference
Shatt al-Arab River	0.76 ± 0.4	84.47 ± 4.4	28.9 ± 4.7	25272 ± 920	29.71 ± 7.4	2.38 ± 2.1	Present study
Shatt al-Basrah Canal	0.76 ± 0.1	13.41 ± 2.1	22.56 ± 9.8	22732 ± 4084	28.21 ± 6.7	4.03 ± 2.0	Present study
Shatt al-Arab River	0.17 – 2.8	81.8 – 112.4	21.8 – 44.0	5452 – 7584	530 – 811	11.3 – 28.1	Abaychi and Douable 1985
Shatt al-Arab River	0.3	48.1	39.6	6205	57.2	19.0	Abaychi and Al-Saad 1988

The average concentrations of these metals in the muscle samples of A. arabicus and P. klunzingeri are summarised in Table 4. The metal levels in the muscle samples were reduced as Fe > Ni > Cu > Cr > Pb > Cd for both A. arabicus and P. klunzingeri.

Table 4

The heavy metal concentrations of Acanthopagrus arabicus and Planiliza klunzingeri samples from the Shatt al-Arab River and Shatt al-Basrah Canal (Mean ± SD) (mg kg^-1 wet weight)

Location/species	Cd	Cr	Cu	Fe	Ni	Pb	Reference
Shatt al-Arab River
Acanthopaqrus arabicus	0.18 ± 0.07	1.19 ± 0.73	3.85 ± 2.18	16.65 ± 6.99	1.28 ± 1.18	2.15 ± 2.09	Present study
Planiliza klunzingeri	0.19 ± 0.06	1.20 ± 0.73	3.90 ± 2.20	16.95 ± 6.89	1.30 ± 1.19	2.17 ± 2.12	Present study
Shatt al-Basrah Canal
Acanthopagrus arabicus	0.17 ± 0.08	1.18 ± 0.74	3.81 ± 2.16	16.96 ± 6.79	1.29 ± 1.17	2.15 ± 2.10	Present study
Planiliza klunzingeri	0.20 ± 0.05	1.19 ± 0.71	3.85 ± 2.13	16.99 ± 6.69	1.99 ± 6.69	2.17 ± 2.15	Present study
Avşar Dam Lake, Turkey	0.17 ± 0.07	1.18 ± 0.73	3.85 ± 2.18	1116.55 ± 6.99	1.27 ± 1.18	2.14 ± 2.09	Öztürk et al. 2009

The bilateral asymmetry results for six external body traits of A. arabicus and five traits of P. klunzingeri are summarised in Table 5. In the two species investigated, the asymmetry levels of the external morphological traits were greater in the Shatt al-Arab River than in the Shatt al-Basrah Canal. At both locations, asymmetry levels were most significant for snout length and lowest for head length in both species (Tables 5, Figures 1, 3).

Table 5

Squared coefficient asymmetry (CV²a) values and character means (Xr + 1) of Acanthopagrus arabicus and Planiliza klunzingeri collected from Shatt al-Arab River and Shatt al-Basrah Canal, Iraq

	Location	Characters
	Location	Snout length	Eye diameter	Head length	Caudal peduncle length	Pectoral fin ray count	Number of lateral line scales
Acanthopagrus arabicus
CV²a	Shatt al-Arab River	89.371	78.874	63.412	75.981	65.412	77.982
CV²a	Shatt al-Basrah Canal	87.964	75.651	64.914	73.912	65.298	74.329
N	Shatt al-Arab River	50	50	50	50	50	50
N	Shatt al-Basrah Canal	50	50	50	50	50	50
Character mean (Xr + 1)	Shatt al-Arab River	0.9	1.4	3.65	1.3	12.5	37
Character mean (Xr + 1)	Shatt al-Basrah Canal	0.80	1.29	3.59	1.29	12.40	36
% of individuals with asymmetry	Shatt al-Arab River	83	85	86	89	86	87
% of individuals with asymmetry	Shatt al-Basrah Canal	81	82	82	86	81	82
Planiliza klunzingeri
CV²a	Shatt al-Arab River	92.751	81.376	61.286	79.518	73.298	-
CV²a	Shatt al-Basrah Canal	87.251	79.521	69.825	77.538	70.156	-
N	Shatt al-Arab River	50	50	50	50	50	-
N	Shatt al-Basrah Canal	50	50	50	50	50	-
Character mean (Xr + 1)	Shatt al-Arab River	0.7	1.95	3.30	1.55	13.5	-
Character mean (Xr + 1)	Shatt al-Basrah Canal	0.6	1.86	3.29	1.53	13.3	-
% of individuals with asymmetry	Shatt al-Arab River	89	87	88	91	89	-
% of individuals with asymmetry	Shatt al-Basrah Canal	76	74	81	89	87	-

Individuals of A. arabicus and P. klunzingeri from both locations were aggregated into length groups (Tables 6 and 7). Increasing levels of asymmetry were noted for each external body feature investigated.

Planiliza klunzingeri (180 mm TL) collected from Shatt al-Arab River showing the morphometric characters used in the asymmetry study. Head length, HL; snout length, SNL; eye diameter, ED; caudal peduncle length, CPL.

Table 6

Squared coefficient asymmetry (CV²a) values and character means (Xr+ 1) of Acanthopagrus arabicus collected from Shatt al-Arab River and Shatt al-Basrah Canal, Iraq

Character	CV²_a	N	Character mean	% of individuals with asymmetry
Acanthopagrus arabicus
Shatt al-Arab River
Snout length
101 – 130	76.354	10	0.90	70
131 – 150	78.426	25	0.87	86
151 – 180	80.631	15	0.86	92
Eye diameter
101 – 130	65.981	10	1.40	67
131 – 150	67.421	25	1.38	87
151 – 180	72.332	15	1.40	93
Head length
101 – 130	77.541	10	3.64	88
131 – 150	79.981	25	3.62	79
151 – 180	81.321	15	3.65	91
Caudal peduncle length
101 -130	65.552	10	1.29	95
131 – 150	69.442	25	1.30	93
151 – 180	71.332	15	1.28	86
Number of pectoral fin rays
101 – 130	67.771	10	12.4	88
131 – 150	69.991	25	12.5	79
151 – 180	72.441	15	12.2	95
Number of lateral line scales
101 – 130	81.932	10	37	93
131 – 150	82.554	25	36	90
151 – 180	84.221	15	35	87
Shatt al-Basrah Canal
Snout length
101 – 130	55.221	10	0.79	88
131 – 150	56.551	25	0.80	76
151 – 180	57.112	15	0.78	82
Eye diameter
101 – 130	61.331	10	1.28	91
131 – 150	61.998	25	1.29	87
151 – 180	62.778	15	1.27	88
Head length
101 – 130	73.221	10	3.58	77
131 – 150	74.001	25	3.59	43
151 – 180	75.112	15	3.57	88
Caudal peduncle length
101 – 130	81.239	10	1.28	92
131 – 150	81.998	25	1.29	90
151 – 180	82.552	15	1.29	94
Number of pectoral fin rays
101 – 130	77.321	10	12.40	89
131 – 150	77.998	25	12.39	85
151 – 180	78.999	15	12.38	84
Number of lateral line scales
101 – 130	78.8871	10	36	78
131 – 150	78.999	25	36	89
151 – 180	79.932	15	36	95

Table 7

Squared coefficient asymmetry (CV²a) values and character means (Xr+ 1) of Planiliza klunzingeri collected from Shatt al-Arab River and Shatt al-Basrah Canal, Iraq

Character	CV²_a	N	Character mean	% of individuals with asymmetry
Planiliza klunzingeri
Shatt al-Arab River
Snout length
141 – 150	89.751	20	0.70	89
151 – 160	90.332	15	0.68	93
161 – 170	91.256	10	0.70	96
171 – 180	92.665	5	0.69	92
Eye diameter
141 – 150	81.998	20	1.96	88
151 – 160	83.552	15	1.98	85
161 – 170	84.998	10	1.95	82
171 – 180	85.002	5	1.95	89
Head length
141 – 150	88.286	20	3.29	78
151 – 160	88.990	15	3.30	77
161 – 170	89.543	10	3.28	75
171 – 180	90.432	5	3.30	86
Caudal peduncle length
141 – 150	78.998	20	1.49	91
151 – 160	80.442	15	1.54	99
161 – 170	85.678	10	1.55	98
171 – 180	88.965	5	1.53	99
Number of pectoral fin rays
141 – 150	75.664	20	13.4	77
151 – 160	78.987	15	13.5	69
161 – 170	80.425	10	13.6	89
171 – 180	84.763	5	13.5	98
Shatt al-Basrah Canal
Snout length
141 – 150	88.776	15	0.58	77
151 – 160	88.995	20	0.59	86
161 – 170	89.435	10	0.60	87
171 – 180	90.993	5	0.57	89
Eye diameter
141 – 150	79.998	15	1.85	92
151 – 160	80.554	20	1.87	97
161 – 170	85.667	10	1.86	98
171 –180	88.798	5	1.84	99
Head length
141 – 150	68.998	15	3.28	96
151 – 160	69.443	20	3.26	97
161 – 170	71.775	10	3.29	87
171 – 180	72.003	5	3.25	88
Caudal peduncle length
141 – 150	79.998	15	1.52	84
151 – 160	80.332	20	1.54	85
161 – 170	83.665	10	1.53	88
171 – 180	87.442	5	1.53	89
Number of pectoral fin rays
141 – 150	80.366	15	13.2	98
151 – 160	83.281	20	13.3	98
161 – 170	84.987	10	13.5	99
171 – 180	87.669	5	13.3	92

Discussion

The Cd, Cr, Cu, Fe, Ni, and Pb levels in the water at the two sampling sites were comparable with universal values. Except for Cd, Fe, and Pb, the heavy metal levels in the water samples did not exceed the WHO (World Health Organization, 1993) and EC (European Community 1998) guidelines (Table 2). The high Pb, Cd, and Fe levels in the water samples in the Shatt Al-Arab River agreed with previously recorded raised levels (Al-Saffie 2005, Hassan 2007, Al-Hejuje et al. 2017). Mastoi et al. (2008) obtained similar elevated values for Cd, which they attributed to the overflow of chemical fertilisers originating from agricultural areas. The elevated values may also be linked to land-based point of origin releases associated with the rapid development of Basrah city centre (Al-Hejuje 1997). The high levels of Cd may also be due to various human-related effects connected to disparities in population density, wastewater releases, and manufacturing events. The Shatt al-Arab River is widely used for cleaning cars. Indeed, Al-Hejuje et al. (2017) remarked that cities are the primary sources of heavy metals in the river. In general, the variation in the levels of heavy metals could be related to several influences. For example, plankton and other water plants in the river may absorb ionic metals. Sandstorms and high fuel consumption may also be contributory factors, particularly during the summer. Electrical energy production also discharges large quantities of metals, notably lead compounds (Al-Hejuje et al. 2017).

The Cd, Cr, Cu, and Fe levels obtained from the sediment samples at the two sampling sites were either comparable to or exceeded the results previously obtained by other investigators.

The Cd, Cr, Ni, and Pb levels found in the tissue samples of A. arabicus and P. klunzingeri in the present and other studies (Öztürk et al. 2009) exceedsafe levels, which could represent a health hazard for human consumption.

Since water in the Shatt al-Arab River is widely used for agricultural irrigation, and water from the Shatt al-Basrah Canal mixes with the water in the southern marshes of Iraq, the focus of pollution research should be concentrated on these two water bodies in terms of both environmental impact and public health issues.

High levels of bilateral asymmetry for snout length and eye lens diameter have previously been reported in numerous freshwater and marine fish species (Al-Hassan et al. 1990, Jawad 2013, Jawad et al. 2016, Jawad & Abed 2020). Such agreement in the finding of bilateral asymmetry can clarify the tendency of this characteristic to steer deviations in the niche. Consequently, it can be exploited as an operative stress biomarker in aquatic animal niches. Otherwise, head length displayed lower bilateral asymmetry levels in both fish species examined from both locations investigated, which suggests that this feature may be more vulnerable to ecological impact measures comprising contamination. The lesser bilateral asymmetry levels obtained for head length in both species could be explained on the grounds that the growing time of head length may not coincide with the occurrence of opposing ecological measures (Jawad 2003).

Analysis of variance showed that bilateral asymmetry levels for the external body traits examined diverged significantly between A. arabicus and P. klunzingeri from the two locations examined (p < 0.001). The present results of heavy metals showed a clear difference in the concentrations in the two locations. These results were also supported by several other reports on water, sediments, and fish tissues in both locations investigated (Al-Hejuje et al. 2017). Numerous other writings from around the world have proved that pollution was most likely responsible for high levels of bilateral asymmetry (e.g., Elie & Girard 2014). Generally speaking, the toxicity of frequent trace metals and other chemicals is revealed to surge with the growth in both temperature and salinity (Elie & Girard 2014). The average water temperature in the two areas investigated was shown to be high (Ahmed & Ghazi 2014), which supports this finding. Besides, salinity as an influence augmenting the toxicity of pollutants in this instance could be due to the average salinity level of water in the Shatt al-Arab and Shatt al-Basrah Canal (Ahmed & Ghazi 2014).

Animals living in marine and freshwater habitats globally (Elie & Girard 2014) and in Iraq were influenced by chemical and organic pollution, resulting in external body feature anomalies (Jawad et al. 2017).

In the present report, the ANOVA test analysis shows that the specimens falling near the upper size limits of A. arabicus and P. klunzingeri had greater bilateral asymmetry values than those found at the lower size limits (p < 0.001). The disparities in the bilateral asymmetry of the six morphometric features of A. arabicus and five morphological characteristics of P. klunzingeri increased with fish length in both species (Tables 6 and 7). This is because of the result of the decline in fish growth; the characteristic means are often lower in young individual groups than in large individual groups (Valentine et al. 1973). Analogous findings concerning fish species from California, U.S.A., were obtained by Valentine et al. (1973), who recommended that the developmental inconsistencies were linked to a surge in bilateral asymmetry with length (age).

Table 8

Comparison of the coefficient of asymmetry (CV²a) of six and five morphological characters of Acanthopagrus arabicus and Planiliza klunzingeri, respectively examined in the present study with those of other fish species collected from locations around the world.

Species	Coefficient of asymmetry (CV²_a)						Reference
Species	Snout length SnL	Eye diameter ED	Head length HL	Caudal peduncle length CPL	Number of pectoral fin ray PFR	Number of lateral line scales LLS	Reference
Acanthopagrus arabicus Shatt al-Arab River	89.371	78.874	63.412	75.981	65.412	77.982	Present study
Shatt al-Basrah Canal	87.964	75.651	64.914	73.912	65.298	74.329
Planiliza klunzingeri Shatt al-Arab River	92.751	81.376	61.286	79.518	73.298	81.297
Shatt al-Basrah Canal	87.251	79.521	69.825	77.538	70.156	80.312
Saurida tumbil	98.77	87.48	91.92	88.74	79.69	89.96	Jawad and Abed (2020)
Callionymidae Callionymus margaretae	19.10	65.00	18.57	-	31.58	-	Al-Mamry et al. (2011b)
Carangidae Carangoides caeruleopinnatus	5.65	18.29	2.87	-	10.04	-	Jawad et al. (2011a)
Decapterus russelli	18.37	21.36	-	-	11.55	14.05	Jawad et al. (2010)
Cichlidae Coptodon guineensis	20.7	58.3	-	-	-	48.7	Jawad et al. (2016)
Coptodon zillii	33.48	56.09	-	-	15.85	-	Jawad (2002)
Sarotherodon melanotheron	28.4	49.4	-	-	-	48.7	Jawad et al. (2016)
Claroteidae Chrysichthys auratus	61.3	60.4	62.8	-	62.1	-	Jawad and Gnohossou (2019)
Clupeidae Sardinella longiceps	123.2	125.3	98.4	-	178.7	-	Jawad et al. (2012e)
Gerreidae Pentaprion longimanus	328.29	92.90	50.50		478.98		Jawad et al. (2011b)
Hemiramphidae Rhynchorhamphus georgii	2.44	121.30	0.51	-	24.20	-	Al-Mamry et al. (2011a)
Leiognathidae Leiognathus equula	25.76	0	17.03		3.25		Al-Mamry et al. (2011a)
Mugilidae Mugil cephalus	62.2	59.6	58.4	-	60.1	-	Jawad and Gnohossou (2019)
Mullidae Upeneus doriae	1.35	0	25.81	-	4.47	-	Jawad et al. (2012d)
Pinguipedidae Parapercis alboguttata	59.64	-	12.39	-	34.70	6.81	Jawad et al. (2012a)
Scombridae Auxis thazard	154.57	55.74	12.11	-	47.33	-	Jawad et al. (2012c)
Rastrelliger kanagurta	12.19	35.30	-	-	35.30	-	Jawad et al. (2001)
Siganidae Siganus rivulatus	24.62	47.08	8.84	-	80.75	-	Al-Mamry et al. (2011–2012)
Siluridae Heteropneustes fossilis	95.78	-	-	-	87.24	-	Al-Hassan et al. (1990)
Sparidae Boops boops	3.03	23.98	-	-	36.69	-	Jawad (2003)
Diplodus annularis	35.49	18.60	-	-	10.43	-
Diplodus vulgaris	28.14	9.53	-	-	-	-
Lithognathus mormyrus	26.31	35.30	-	-	-	-
Tetraodontidae Lagocephalus sceleratus	74.88	22.8	9.677	-	39.7	-	Jawad (2013)

To appraise the values disparity in regularity obtained for the six external body features of A. arabicus and P. klunzingeri, a valuation was carried out between the report at hand and the levels of the fluctuating asymmetry of fish body external features of other fish species investigated from the same area of the current investigation and other regions around the world (Table 8). The amount of asymmetry of the snout length, the morphometric character with a high asymmetry value, is comparable to that of Saurida tumbil obtained from the Arabian Gulf Coast of Iraq (98.77) (Jawad & Abed 2020). On the other hand, it is less than those of Pentaprion longimanus (328.29) (Jawad et al. 2011b), Auxis thazard (Jawad et al. 2012c), and Sardinella longiceps (123.2) (Jawad et al. 2012e). The overall results of this valuation designate that the values of asymmetry in the six and five external body features of A. arabicus and P. klunzingeri, respectively, are similar in their high value or lower in contrast to other species. Even though the species of fish obtained from various sites stated in this evaluation are dissimilar, the evaluation illustrates the amount of influence of the ecosystem on the body external features of the fish that are vulnerable to the niche’s natural status (Jawad et al. 2012e). Built on the outcomes of the current investigation, it is suggested that an administration policy is required to establish an excellent physical environment in the Arabian Gulf waters of Iraq.

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Morphological asymmetry in two marine fish species Acanthopagrus arabicus (Family: Sparidae) and Planiliza klunzingeri (Family: Mugilidae), collected from brackish and freshwater environments in southern Iraq

Article Category: Original research paper

Online veröffentlicht: 28. Juni 2023

Seitenbereich: 228 - 239

Eingereicht: 09. Aug. 2022

Akzeptiert: 11. Apr. 2023

DOI: https://doi.org/10.26881/oahs-2023.2.07

© 2023 Laith A. Jawad et al., published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

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