ANNALES · Ser. hist. nat. · 21 · 2011 · 2 
151
Short scientific article                UDK 591.159:597.556.33(535)
Received: 2011-07-22
PRELIMINARY STUDY ON ASYMMETRY IN MORPHOLOGICAL 
CHARACTERS OF PENTAPRION LONGIMANUS (OSTEICHTHYES: 
GERRIDAE) FROM THE SEA OF OMAN
Laith A. JAWAD & Juma M. AL-MAMRY
Marine Science and Fisheries Centre, Ministry of Agriculture and Fisheries Wealth, PO Box 427, Post Code 100, Muscat, 
Sultanate of Oman
E-mail: laith_jawad@hotmail.com
Amal M. AL-HINAI & Maryam A. AL-RASHIDI
High Technical College, Muscat, Sultanate of Oman
Haithem K. AL-BUSAIDI
Marine Science and Fisheries Centre, Ministry of Agriculture and Fisheries Wealth, PO Box 427, Post Code 100, Muscat, 
Sultanate of Oman
ABSTRACT
The fluctuating asymmetry in Pentaprion longimanus, was estimated by determining the number of rays in pec-
toral fins and measurement of four body morphometric characters, i.e. preorbital length, postorbital length, orbital 
diameter and head length on both sides of the body in 91 individuals from the population of P. longimanus, collected 
from the waters off Muscat City, The Sea of Oman. Units of asymmetry were determined as the absolute value of 
difference between counts on both sides of body. Results indicate that pre and postorbital length and the number 
of pectoral fin rays demonstrate a higher level of asymmetry than the rest of the characters studied. In the pre and 
postorbital lengths we also noticed the trend of increase in the asymmetry values with the fish length. The possible 
cause of the asymmetry in this species was discussed in relation to different pollutants and their presence in the area. 
The usefulness of the information in future taxonomic studies on P. longimanus was also addressed. 
Keywords: fluctuating asymmetry (FA), Sea of Oman, Sultanate of Oman, Pentaprion longimanus, indicator
STUDIO PRELIMINARE SULL’ASIMMETRIA DEI CARATTERI MORFOLOGICI DI 
PENTAPRION LONGIMANUS (OSTEICHTHYES: GERRIDAE) DEL MARE DELL’OMAN
SINTESI
L’Asimmetria Fluttuante di Pentaprion longimanus è stata valutata grazie alla determinazione del numero dei 
raggi delle pinne pettorali e alla misurazione di quattro caratteri corporei morfometrici: lunghezza preorbitale, lun-
ghezza postorbitale, diametro orbitale e lunghezza del capo da entrambi i lati del corpo, in 91 individui provenienti 
da una popolazione di P. longimanus catturata nelle acque al largo della città di Mascate, nel mare dell’Oman. Le 
unità di asimmetria sono state determinate come valore assoluto della differenza fra i conteggi effettuati su entrambi i 
lati del corpo. I risultati indicano che le lunghezze pre- e postorbitali e il numero dei raggi delle pinne pettorali dimo-
strano un livello di asimmetria maggiore rispetto agli altri caratteri studiati. Riguardo alle lunghezze pre e postorbitali 
è stato inoltre notato un aumento nei valori dell’asimmetria all’aumentare della lunghezza corporea. Gli autori discu-
tono la possibile causa di asimmetria in questa specie in relazione ai diversi inquinanti e alla loro presenza nell’area. 
L’articolo evidenzia pure l’utilità di tale informazione per studi tassonomici futuri su P. longimanus.
Parole chiave: asimmetria fluttuante (FA), mare dell’Oman, Sultanato dell’Oman, Pentaprion longimanus, 
indicatore
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Laith A. JAWAD et al.:  PRELIMINARY STUDY ON ASYMMETRY IN MORPHOLOGICAL CHARACTERS OF PENTAPRION LONGIMANUS ..., 151–156
INTRODUCTION
The longfin mojarra, Pentaprion longimanus (Cantor, 
1849) is a tropical demersal species distributed in the 
Indo-West Pacific, mainly in the Sea of Oman, western 
and southern coasts of India and off Sri Lanka to Indone-
sia. It is also reported from the Philippines, the Ryukyu 
Islands and southern to northern parts of Australia (Fro-
ese & Pauly, 2010). This species inhabits coastal waters 
and forms large schools. It feeds on small benthic ani-
mals. In Oman, the longfin mojarra is considered com-
mercially important as its landing reached 10 000 tons 
in 2010 (Fish Statistics, 2010). It represents an important 
part of the everyday Omani diet and is also used as dry 
fish commodity (Al-Abdessalaam, 1995).
There are numerous studies investigating the im-
pact of miscellaneous environmental stressors on deve-
lopmental stability and the variety of organisms studied 
is wide (Eriksen et al., 2008). However, the only publi-
shed study on the fluctuating asymmetry in Omani fish 
species is that of Jawad et al. (2010), therefore, the pre-
sent study is considered a quantitative and qualitative 
addition to the previous studies on Omani fish fauna.
The objectives of the present preliminary study were 
to determine the extent and direction of the asymmetry 
in some morphological characters of Pentaprion longi-
manus and the possible usefulness of the information in 
future taxonomic studies of P. longimanus.
MATERIALS AND METHODS
Sultanate of Oman lies on the coasts of two seas, the 
Sea of Oman and the Arabian Sea. The country has an 
extensive coastline of 3,165 km, on the Sea of Oman 
in the north and the Arabian Sea in the south. Muscat 
is located in NE Oman, at 24°00’ N and 57°00’ E with 
the Sea of Oman at the northern and western periphery 
of the city.
A total of 91 specimens of Pentaprion longimanus 
were collected from the Muscat coastal area, the Oman 
Sea (Fig. 1). Five bilateral characters used to compare 
asymmetry were recorded as follows: (1) length of the 
pre-orbital distance (mm): measured from mouth to the 
anterior edge of the orbit; (2) length of the post-orbital 
distance (mm): measured from the posterior edge of the 
eye to the posterior edge of the operculum; (3) orbital 
diameter (mm): measured from the anterior to the po-
sterior edges of the eye; (4) head length (mm): measu-
red from mouth to the posterior edge of operculum; (5) 
number of pectoral fin rays: count of the total number 
of pectoral fin rays, including the most upper ray. Most 
characters were counted and measured under a binocu-
lar dissecting microscope. For specimens too large to fit 
under a microscope, a magnifying glass was used.
The statistical analysis included calculating the square 
coefficient of asymmetry variation (CV2a) for metric and 
meristic characters according to Valentine et al. (1973):
CV2a = (Sr-l × 100/ Xr+l)
2
where Sr-l is the standard deviation of the signed dif-
ference and Xr+l is the mean of the character, calculated 
by adding the absolute scores for both sides and divi-
ding by the sample size. To eliminate scaling problems 
associated with growth in metric characters, each mea-
surement was divided by suitable general size measure-
ments, e.g. head length was used as the standardizing 
measurement. Each of the metric characters was treated 
in this manner before obtaining the signed differences.
RESULTS
The results of asymmetry data analysis of the pre-
viously listed characters of Pentaprion longimanus col-
lected from the Muscat coastal area, the middle part of 
the Oman Sea, are shown in Table 1. The highest values 
were recorded for the pre and postorbital length and the 
number of pectoral fin rays, and the lowest value for the 
head length.
The percentage of individuals showing asymme-
try in the postorbital length character was the highest 
among the percentages recorded for the five characters 
(85.71% of the total fish studied) and the lowest percen-
tage was for individuals with asymmetry in preorbital 
length (65.93% of the total fish studied). Individuals of 
P. longimanus were grouped into length classes (Tab. 2). 
An increasing trend in the asymmetry value with fish 
length was noticed for preorbital and postorbital lengths 
(P <0.05).
The results have shown that all the characters studi-
ed are dextral, with the right side showing higher value 
Fig. 1: Map showing the collection site of the specimens 
of Pentaprion longimanus.
Sl. 1: Zemljevid, ki prikazuje lokacijo ulova primerkov 
vrste Pentaprion longimanus.
ANNALES · Ser. hist. nat. · 21 · 2011 · 2 
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Laith A. JAWAD et al.:  PRELIMINARY STUDY ON ASYMMETRY IN MORPHOLOGICAL CHARACTERS OF PENTAPRION LONGIMANUS ..., 151–156
Size class n CV2a character mean X r + l
% of individuals 
with asymmetry
Preorbital length
10.1-11.0 3 81.29 6.92 66.67
11.1-12.0 23 92.48 8.08 78.26
12.1-13.0 31 98.13 8.88 67.74
13.1-140 30 101.87 9.57 63.33
14.1-15.0 4 105.45 10.50 0
Total 91
Postorbital length
10.1-11.0 3 43.83 6.17 66.67
11.1-12.0 23 75.15 8.67 82.61
12.1-13.0 31 83.03 9.73 90.23
13.1-140 30 94.72 10.06 80.00
14.1-15.0 4 99.23 11.23 100
Total 91
Eye diameter
10.1-11.0 3 243.87 6.92 100.00
11.1-12.0 23 147.43 9.48 78.26
12.1-13.0 31 63.61 9.68 70.97
13.1-140 30 84.81 9.95 76.67
14.1-15.0 4 17.42 10.38 25.00
Total 91
Head length
10.1-11.0 3 44.64 21.17 33.33
11.1-12.0 23 54.25 25.52 78.26
12.1-13.0 31 78.32 27.82 83.87
13.1-140 30 24.78 29.46 70.00
14.1-15.0 4 5.20 32.44 75.00
Total 91
Number of pectoral fin rays
10.1-11.0 3 338.61 11.17 100
11.1-12.0 23 351.08 9.39 73.91
12.1-13.0 31 469.10 9.32 77.42
13.1-140 30 602.44 9.82 80.00
14.1-15.0 4 203.22 10.38 75.00
Total 91
Tab. 1: Square coefficient of asymmetry variation (CV2a) values and character means (X r+l) of P. longimanus.
Tab. 1: Vrednosti kvadratnega koeficienta asimetrije (CV2a) in povprečne vrednosti morfoloških znakov (X r+l) vrste 
P. longimanus.
Character CV2a N
Character 
mean
% of individuals 
with asymmetry
Preorbital length 328.29 91 8.91 65.93
Postorbital length 418.73 91 9.52 85.81
Eye diameter 92.90 91 9.66 73.63
Number of pectoral fin rays 478.98 91 9.61 78.02
Head length 50.50 91 22.76 75.82
Tab. 2: Square coefficient of asymmetry variation and character means (X r+l) by size class of P. longimanus.
Tab. 2: Kvadratni koeficient asimetrije in povprečne mere telesnih morfoloških znakov (X r+l) za posamezne veliko-
stne razrede vrste P. longimanus.
ANNALES · Ser. hist. nat. · 21 · 2011 · 2 
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over the left side. The only exception is the pectoral fin 
ray count, which appears to be sinistral since counts on 
the left side are larger than those on the right side. For 
the pectoral fin ray count, bilateral asymmetry occurred 
in 78.02% of the total of 91 P. longimanus examined. 
The percentage of the left handed individuals is 46.2%. 
As to the preorbital, postorbital lengths, orbital diameter 
and head length, the bilateral asymmetry exhibited was 
65.9%, 85.81%, 73.6% and 75.8% respectively. The 
percentages of the right handed specimens are, 38.5%, 
49.5%, 35.7% and 38.9% respectively.
DISCUSSION
Pentaprion longimanus is an active fish, subjected 
to greater energy demands. The energy is needed both 
for its developmental needs and environmental stress. 
Some energy is allocated for maintaining homeostasis 
(Mitton, 1994). If the available energy is not sufficient 
to buffer the stress effects, homeostasis may be impai-
red, resulting in abnormal development (Mitton, 1994; 
Somarakis et al., 1997). Consequently, higher levels of 
asymmetry can be recorded in P. longimanus.
There is some variation in the asymmetry values 
among the five morphological characters studied in P. 
longimanus. Characters like pre and postorbital length 
and pectoral fin ray count showed higher asymmetry 
values than those of the other characters studied. High 
asymmetry values for these three characters have also 
been recorded in several freshwater and marine fish spe-
cies (Al-Hassan et al., 1990; Al-Hassan & Hassan, 1994; 
Jawad, 2001, 2003; Jawad et al., 2010). Such agreements 
in results of asymmetry might indicate the vulnerability 
of these three characters to immediate changes in the 
environment. On the other hand, the low asymmetry va-
lues displayed in the two characters, head length and 
orbital diameter might be explained on the basis that 
these characters are designated with high functional im-
portance and are highly canalized during ontogeny thus 
giving low level of fluctuating asymmetry, FA (Palmer & 
Strobeck, 1986; Moller & Pomiankowski, 1993).
The effect of asymmetry on the size of the fins, the 
body proportions of the fish and rendering the fish either 
left handed or right handed is evident from the results 
of some studies (Moodie & Reimchen, 1976; Reimchen, 
1983; Cameron, 1995; Zygar et al., 1999; Künzler & Ba-
kker, 2000; Gonçalves et al., 2002; Bergstrom & Reim-
chen, 2003). It is quite possible for such asymmetry to 
hinder the basic functions of those body parts.
In taxonomic and racial studies involving pectoral fin 
ray count and the pre and postorbital lengths, interchan-
ging counts and differences in dimensions from left and 
right sides of P. longimanus introduce an additional source 
of variation to taxonomists who rely on these characters 
when separating specimens of this species or its populati-
ons. Bilateral asymmetry has proven problematic for fish 
taxonomists (Parenti, 1986) and taxonomists of animal 
groups other than fish such as owl (Norberg, 1977).
Pollution of sea water and sediments by hydrocar-
bons, heavy metals, pesticides and organic matter are 
considered the main cause of environmental stress 
(Bengtson & Hindberg, 1985). This state of pollution is 
not unusual for the coastal environment of the Oman 
Sea where different pollutants were reported to affect 
its waters in the last twenty years (De Mora et al., 2004, 
2005; Al-Darwish et al., 2005; Tolosa et al., 2005; Abdel 
Gawad et al., 2008; Khan, 2008).
Several authors have shown a relationship between 
the coefficient of asymmetry and fish length (Al-Hassan 
et al., 1990; Al-Hassan & Hassan, 1994; Al-Hassan & Sh-
wafi, 1997; Jawad, 2001; Jawad et al., 2010) where there 
was a trend of increase in the asymmetry value with the 
increase in fish length. This trend is probably the result 
of incomplete development; character means are always 
lowest in smaller size classes (Valentine et al., 1973). The 
same results were obtained by Valentine et al. (1973) in 
selected fish species collected from California, U.S.A. and 
Jawad et al. (2010) in the carangid fish species, Decap-
terus russelli collected from the northern coastal region 
of the Oman Sea, Oman. The researchers suggested two 
possible hypotheses that may account for such a trend; 
namely, the ontogenetic changes (an increase in asymme-
try with size - age) and the possible historical process (a 
secular increase in asymmetry).
ACKNOWLEDGEMENT
We would like to thank the Ministry of Agriculture 
and Fisheries Wealth, the Agriculture and Fisheries De-
velopment Fund and the Marine Science and Fisheries 
Centre for giving us the opportunity to work on the fish 
samples within the qualitative and quantitative distribu-
tion of marine organisms in Sultanate of Oman and for 
providing the appropriate financial support.
Laith A. JAWAD et al.:  PRELIMINARY STUDY ON ASYMMETRY IN MORPHOLOGICAL CHARACTERS OF PENTAPRION LONGIMANUS ..., 151–156
ANNALES · Ser. hist. nat. · 21 · 2011 · 2 
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PREDHODNA ŠTUDIJA ASIMETRIJE MORFOLOŠKIH ZNAKOV PRI VRSTI PENTAPRION 
LONGIMANUS (OSTEICHTHYES: GERRIDAE) IZ OMANSKEGA ZALIVA
Laith A. JAWAD & Juma M. AL-MAMRY
Marine Science and Fisheries Centre, Ministry of Agriculture and Fisheries Wealth, PO Box 427, Post Code 100, Muscat, Sultanate of 
Oman
E-mail: laith_jawad@hotmail.com
Amal M. AL-HINAI & Maryam A. AL-RASHIDI
High Technical College, Muscat, Sultanate of Oman
Haithem K. AL-BUSAIDI
Marine Science and Fisheries Centre, Ministry of Agriculture and Fisheries Wealth, PO Box 427, Post Code 100, Muscat, Sultanate of 
Oman
POVZETEK
Članek obravnava spremenljivost asimetrije pri vrsti Pentaprion longimanus, ocenjeno na podlagi števila plavu-
tnic v trebušnih plavutih in meritev štirih telesnih morfoloških znakov, tj. preorbitalne razdalje, postorbitalne razdalje, 
premera očesa in dolžine glave na obeh straneh telesa 91 primerkov iz populacije P. longimanus, ujetih pri mestu 
Muscat v Omanskem zalivu. Kot mero za asimetrijo smo uporabili absolutno razliko v meritvah telesnih morfoloških 
znakov na vsaki strani telesa. Rezultati kažejo, da je pri preorbitalni in postorbitalni razdalji in številu plavutnic v tre-
bušnih plavutih asimetrija večja kot pri drugih obravnavanih telesnih znakih. Pri preorbitalni in postorbitalni razdalji 
je bil opažen tudi trend večanja vrednosti asimetrije z večanjem dolžine ribe. Kot možen vzrok asimetrije pri tej vrsti 
bi lahko navedli različna onesnaževala in njihovo prisotnost na obravnavanem območju, Upoštevana je bila tudi 
možnost uporabe teh ugotovitev v prihodnjih taksonomskih študijah vrste P. longimanus.
Ključne besede: spremenljiva asimetrija (FA), Omanski zaliv, Sultanat Oman, Pentaprion longimanus, indikator
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