Abstract
Environmental isolation can result in the evolution of distinct shape traits, which can eventually cause evolutionary isolation and the formation of different populations. The shape features of fish are influenced by environmental factors such as the type of substrate, water flow, vegetation type, competition, predation, pollution levels, and food availability. Therefore, ecological or environmental conditions play a major role in creating morphological changes in fish. A recent study examined the morphological differences caused by geographical isolation and environmental factors to assess the status and level of population differentiation of Mudskipper (B. dussumieri) based on quantifiable morphological traits in different climatic environments along the Persian Gulf coast. A total of 35 adult Mudskippers (B. dussumieri) were caught randomly using a scoop net. The fish were then stored in ice and transported to the laboratory The results indicated that there were almost two isolated clusters and that Mudskippers were present in the Goban and Delwar areas opposite Khor Abi region. It seems that the extensive coastline, dense mangroves, variation in bed type in various parts of the Persian Gulf, salinity differences in the east, center, and west regions, and human population density in these areas have largely hindered the mobility of individuals among diverse habitats.
 
INTRODUCTION
As a semi-enclosed sea basin, the Persian Gulf has relatively unique characteristics. Its entrance is the narrow Strait of Hormuz, and the circulation of water is limited to the Makran Sea (Gulf of Oman). This sea is very shallow compared to other seas of similar size, with an average depth of only 35 meters and vast expanses only a few meters deep. Its maximum depth, a few kilometers from the Strait of Hormuz, is only 100 meters. As a result of this physiography, the Persian Gulf experiences large seasonal fluctuations in surface water temperature. The temperature in coastal surface waters varies from 10°C in winter to 35°C in summer and reaches higher values in shallow lagoons and tidal flats. This recent study was conducted to investigate the morphological differences caused by the above factors, to test the status and degree of population differentiation of this species based on measurable morphological traits in different parts of the Persian Gulf.
MATERIALS AND METHODS
In general, 35 samples of adult mudskipper fish (B. dussumieri)—15 samples from Goban, 13 samples from Delvar, and 7 samples of khur-Abi—were caught randomly, mostly with scoop nets, in the muddy beds and intertidal areas. The samples were stored in ice and transported to the laboratory. After identification and isolation of the B. dussumieri species using the existing identification key and common and standard methods, they were placed under morphometric examination. ANOVA tests were used to compare the measured variables between three regions: Goban (A), Delvar (B), and Khur-Abi (C). Since there was no prejudice towards the grouping of samples in this research, principal component analysis (PCA) was used to distinguish between samples of different populations. The variables used in this test were seven variables that had significant differences between the Mudskippers of the three study areas based on the ANOVA test. Euclidean distance and the average linkage algorithm (UPGMA) were also used to measure the morphological distance between the samples and to draw the morphological dendrogram of the Mudskippers of regions A, B, and C, respectively.
 
RESULTS
The dendrogram obtained by the average linkage method for clustering and calculating the Euclidean distance for seven significant traits between all the measured anemones showed the creation of two separate and distinct clusters, including the anemones of areas A and B versus area C (Figure 3). Based on the results of the CVA analysis, the Wilks' lambda test (p < 0.001) confirmed the fit of the data for the MANOVA test. The results of the MANOVA test (p < 0.001), based on the paired comparison of the Hotelling test, showed that there is a significant difference between the body shape of the populations of Khur-Abi and the other two regions (Table 4).
 
DISCUSSION AND CONCLUSION
Environmental factors such as temperature and salinity in the west of the Persian Gulf differ from those in the east of the Persian Gulf. These differences are mainly caused by the discharge of the main rivers (Helle, Zohre, and Arvand) into the western part of the Persian Gulf. Polgar et al. (2017) investigated seven populations of Waltoni's walrus (P. waltoni) from the Persian Gulf and the Gulf of Oman, and concluded that differences in physicochemical parameters are the main potential factors for distinguishing the four Persian Gulf populations from the two Gulf of Oman populations. The results of this research are consistent with the present survey. These physicochemical factors likely also caused the separation between the western and eastern populations of the Persian Gulf.
 
REFRENCES
Polgar, G., Ghanbarifardi, M., Milli, S., Agorreta, A., Aliabadian, M., Esmaeili, H.R. and Khang, T.F., 2017. Ecomorphological adaptation in three mudskippers (Teleostei: Gobioidei: Gobiidae) from the Persian Gulf and the Gulf of Oman. Hydrobiologia, 795, pp. 91-111. https://doi.org/10.1007/s10750-017-3120-8