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Histopathological and pathomorphological effects of 15 ppb mercuric chloride on Persian sturgeon, Acipenser persicus, were investigated using histological and electron microscopy observations. Light microscopy showed that the gill epithelial hypertrophy, wrinkling and hyperplasia in lamellar epithelia and lamellae fusion occurred after 48 h of exposure. Gill epithelia also showed occasional necrosis, which had almost been completed and blood emerged from the capillaries. However, occasional necrosis in some regions of the filament, both with blood emerging and with no bleeding, was observed by using electron microscopy. These injuries were well observed in inter-lamellar regions of the filament and also wrinkling of the lamellar epithelium. Ultrastructural observations showed some cellular disorders in gill epithelium of the Persian sturgeon, A. persicus, fry. In addition, increase in apical vesicles of the chloride cells and necrosis in apical surfaces of some chloride cells, hypertrophy and necrosis of the chloride cells’ mitochondrion and endoplasmic reticulum also were some of the other cellular disorders observed through transmission electron microscopy. In conclusion, the gills of A. persicus fry were sensitive to low concentrations of inorganic mercury (HgCl2).

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The gill Structure and localization of Na⁺, K⁺-ATPase were examined through branchial arches of the Persian sturgeon, Acipenser persicus larvae (25 days-post-hatched, 417.3 mg). Studies were conducted through light microscopy (H&E Staining) and immunofluorescence for Na⁺, K⁺-ATPase. Results showed each gill consisted of four complete holobranches and opercular hemibranch. Each filament carried rows of lamellae consisting of a network of interconnecting blood lacunae, which were lined by pillar cell flanges. Pavement cells covered the outermost layer of the lamella and blood cells were found in lacunae. High density of ionocytes (529.73 per mm² of the gill tissue) was found at the base of the lamella, in the interlamellar regions, on the filaments and the septums. Ionocytes possessed large size and round basal nuclei. Ionocytes possessed strong immunofleurescence in their cytoplasm, especially in the basolateral sides because of high concentration of the enzyme. The results showed that the main structures of the gill has already been formed at this developmental stage of the Persian sturgeon, and along with its respiratory and excretory roles, it also plays an important role in osmoregulation.

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Oxygen concentration the environment and cellular organisms is one of the effective factors during normal development of organisms. In the present study, the transcription levels of the hypoxia-inducible factors (hif-1, hif-2) were evaluated during development of an ancient fish species Acipenser persicus, in the normal oxygen density of environment. The transcription of hif-1, hif-2 detected in all developmental time-points defined, from embryo to juvenile stages. Target genes transcriptions were normalized using RPL6 as reference gene. Changes in normalized hif-1, hif-2 mRNA expression were statistically significant throughout developmental points (p<0.05). Our data revealed that the mRNA expression of hifs were low during embryonic development and then upregulated significantly at hatching and early larval time-points. Then, in the late larval development and juvenile stage the expression of hifs started to decline. The comparison between hif-1 and hif-2 mRNA transcription showed that maximum gene expressions of hif-1and hif-2 occurred in 15 and 20 days after hatching, respectively. The increased expression of hifs suggests their association with two important events in the larval evolution, viz. internal feeding (yolk absorption) and external feeding. Also, the observed increase in mRNA expression of hifs during larval development of A. persicus can be attributed to increase in oxygen demand.

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Length-weight relationships and fecundity of 93 individual female Acipenser persicus broodstocks were investigated. The specimens were caught during 2001-2005 from Golestan, Mazandaran and Guilan provinces along the southern coast of the Caspian Sea. Total length and weight of each fish was measured to the nearest 1cm and 100 g, respectively. Age determination was carried out by using transects of the first ray of pectoral fin. The absolute fecundity was assessed by egg count per weight unit of all eggs existed in the body. The specimens were from 13 to 20 years old, of which the 16 years old had the highest proportion with 23.7%. Range of total length and weight were 132.5 to 211 cm and 14 to 42 kg, respectively. Mean absolute fecundity was estimated 267810 ± 92570. Total length, weight and absolute fecundity of fish increased with age in all cases, showed a significant positive correlation (p <0.01). The slope of the length-weight relationship (b) was equal to 2.745 and isometric growth pattern was determined in this species.

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Effects of sodium salt solutions on physicochemical and sensory characteristics of refrigerated Persian sturgeon (Acipenser persicus) fillets during 12 days of storage were investigated. Fillets were dipped in solutions (2.5% w/v) of sodium acetate (SA), sodium lactate (SL), sodium citrate (SC) and distilled water (as control) for 10 minutes and then packaged. An assessment of TBARS, FFA, pH, heme iron and sensory attributes (flavor, color and odor) was carried out on 0,3,6,9 and 12 days past the storage time. Results indicated that TBARS values of each sample increased with the storage time (P< 0.05). Control showed the highest values of TBARS while sodium acetate sample had the significantly (P< 0.05) lowest figures among the treatments (1.04 for SA versus 2.34 for control). Lipid hydrolysis assessment revealed that the sodium salt treated samples, especially sodium acetate, acquired the lower FFA amounts (P< 0.05) as compared with control. No significant differences (P> 0.05) were observed among the pH values of the treatments. Heme iron assessment showed that the samples treated with sodium acetate contained more heme iron as compared with control. Sensory assessment revealed more desirable scores for the sodium acetate treated group as compared with others samples. The order for the sodium salt treated effects was: SA> SC> SL. As a consequence, sodium salts, in particular sodium acetate, might be considered as effective tools in preventing the quality degradation of the fillets, resulting in an extension of their shelf life.