It has been postulated that the building of the Shahid-Rajaei dam on the Tajan River around 1995 has lead to the morphological divergence of Siah Mahi Capotes capoeta gracilis (Pisces) of up-and downstream populations due to the isolation. A 13-landmark morphometric truss network system was used to investigate the hypothesis. Univariate analysis of variance showed significant differences between the means of the two groups for 45 standardized morphometric measurements out of 78 characters studied. In linear discriminant function analysis (DFA), the overall assignment of individuals into their original groups was 87.6%. The proportion of individuals correctly classified into their original groups was 90.3% for upstream and 83.7% for downstream population. The principal component analysis (PCA) scatter plot of individual component scores between PC1 and PC2 showed 121 fish specimens grouped into two areas but with a relativity high degree of overlap between two populations. Clustering analysis based on Euclidean square distances among groups of centroids using an UPGMA resulted into two main clusters indicating two populations of C. c. gracilis. The present study indicated the presence of two morphologically different populations of C. c. gracilis in the Tajan River across the Shahid-Rajaei dam, probably due to their limited downstream dispersal and the elimination of upstream migration altogether, due the construction of the dam.
Apoptosis, a form of programmed cell death, is a critical component in maintaining homeostasis and growth in all tissues and plays a significant role in immunity and cytotoxicity. In contrast to necrosis or traumatic cell death, apoptosis is a well-controlled and vital process characterized mainly by cytoplasmic shrinkage, chromatin condensation, DNA fragmentation, membrane blebbing and apoptotic bodies. Our understanding of apoptosis is partly based on observations in invertebrates but mainly in mammals. Despite the great advantages of fish models in studying vertebrate development and diseases and the tremendous interest observed in recent years, reports on apoptosis in fish are still limited. Although apoptotic machinery is well conserved between aquatic and terrestrial organisms throughout the history of evolution, some differences exist in key components of apoptotic pathways. Core parts of apoptotic machinery in fish are virtually expressed as equivalent to the mammalian models. Some differences are, however, evident, such as the extrinsic and intrinsic pathways of apoptosis including lack of a C-terminal region in the Fas-associated protein with a death domain in fish. Aquatic species inhabit a complex and highly fluctuating environment, making these species good examples to reveal features of apoptosis that may not be easily investigated in mammals. Therefore, in order to gain a wider view on programmed cell death in fish, interactions between the main environmental factors, chemicals and apoptosis are discussed in this review. It is indicated that apoptosis can be induced in fish by exposure to environmental stressors during different stages of the fish life cycle.
ABSTRACT. We evaluated the effects of the Shahid-Rajaei dam, 14 years after its construction, on morphometric and genetic divergence between up-and downstream populations of the Iranian fish SiahMahi (Capoeta capoeta gracilis). Sixty-six specimens were analyzed. There were significant differences between the 2 groups in the means of 16 morphometric characters (univariate analysis). In discriminant function analysis, the proportion of individuals classified into their original groups was 97 and 100% for up-and downstream populations, respectively. Principal component analysis of morphometric data demonstrated that the up-and downstream samples of Siah-Mahi are clearly distinct. In the genetic analysis, 6 informative primers produced 89 polymorphic bands with 95% polymorphism. In association analysis between morphological and genetic data, 63 of 89 genetic markers were significantly correlated with the 16 morphometric characters. We conclude that these are 2 morphologically and genetically distinct populations of C. c. gracilis, probably due to limited downstream dispersal and elimination of upstream migration.
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