Investigation of gill mucus cells of Lake Van fish (Alburnus tarichi) during reproductive migration.

Lake Van is the largest lake in Turkey. It is one of the few soda lakes in the world. Its water is brackish and soda. The lake water has a salinity rate of 19‰ and a pH of 9.8. The salty-soda content of the lake greatly limits biodiversity. Since the Lake Van fish is anadromous, it migrates from the extreme conditions of Lake Van to the freshwater pouring into the lake to spawn. In the same way, once they have emerged from the eggs, the newly hatched fish return to the lake environment to feed again. In this study, the changes in Lake Van fish gill mucus cell histochemistry were examined using different histological stains. The area and density of the mucus cells were observed to have changed in the aquatic areas of different physicochemical properties due to reproductive migration. The intensity of the mucus staining was also found to vary in different aquatic locations and gill regions. As a result, it was clearly demonstrated that mucus cell glycoprotein contents and levels found in Lake Van fish gills varied in different lake freshwater and aquatic environments. In addition, it was determined that the area and density of the mucus cells varied during reproductive migration. It is thought that the change in mucus cells was caused by salinity, pH, and bacterial and parasitic infections encountered in different aquatic environments. These changes in the gill mucus cells play an important role in the aquatic adaptation of fish.

Polyclonal antibody-based immunoassay of vitellogenin in Van fish (Alburnus tarichi).

Van Lake is the third largest closed lake in the world and the biggest lake in Turkey. An ELISA method has developed with the aim of determining the pollution caused by estrogens and estrogen-like chemicals that have come to the lake Van in recent years. First, the vitellogenin in estrogen-treated male fish plasma was purified by ion exchange chromatography, injected into rats, and the obtained polyclonal antibodies were tested for specificity by Western blot and immunohistochemical methods. Immunohistochemical labeling of the vitellogenin-synthesized liver resulted in the intense marking of the liver of the animals injected with estrogen, while no markings were observed in the control group. The limit of detection of the developed enzyme-linked immunosorbent assay was 4.6 µg L-1, and the working range was 7.8 to 2000 µg L-1. Intra- and inter-assay variations were 13.0 % and 13.3%. The highest level of vitellogenin in male fishes measured was 23.56 µg mL-1.

Development of osmoregulatory tissues in the Lake van fish (Alburnus tarichi) during larval development.

Lake Van is one of the largest alkaline lakes worldwide and Lake Van Fish (Alburnus tarichi Güldenstädt, 1814) is the only vertebrate species inhabiting it. Lake Van Fish is an anadromous species that migrates to the streams (salinity 0.02%, pH 8.42) flowing into Lake Van (salinity 0.22%, pH 9.8) during the spawning period (April-July). Following spawning, fish return to Lake Van while larvae remain in fresh water. This study examined the development of osmoregulatory organs and the distribution of ionocytes in Lake Van Fish larvae adapting to the highly alkaline water characterizing the lake. Ionocytes were marked immunohistochemically and observed in whole mounts with immunofluorescence staining using the Na+/K+ ATPase antibody. Ionocytes were first identified in the yolk sac membrane and skin, and then in the gills, digestive tract, and kidneys of larvae. The number of ionocytes on yolk sac membrane and skin decreased during larval development, indicating ionocytes on these tissues have a role in larvae osmoregulation. Larvae hatched from eggs in stream waters die when transferred to Lake Van water but survived in lake water diluted with deionized water. Thus, larvae need to go through certain alterations at the cellular and organ levels in order to adapt to the conditions of Lake Van water, indicating they do not enter this lake immediately after hatching.

Vitellogenin in the male Lake Van fish (Chalcalburnus tarichi Pallas, 1811).

Chalcalburnus tarichi is an endemic cyprinid species living in Lake Van, Turkey. In the present study, we investigated vitellogenin (Vtg) in the plasma of adult male C. tarichi, sampled monthly from Edremit, Campus and Çarpanak sites of Van Edremit Gulf (VEG) of lake, between October 2004 and May 2005. The fish living around VEG winters in deep water around Edremit site. University and Çarpanak sites are also on fish migration way from VEG to fresh water (Karasu River). The levels of measured plasma Vtg changed from trace levels to 26.35 µg/mL. The highest level of plasma Vtg was detected in April, with a concentration of 21.60 ± 1.29 µg/mL. We also performed immunohistochemical Vtg staining in the liver sections of male fish and determined Vtg positive hepatocytes in the liver of 1/10 sampled fish. Our results indicated that C. tarichi living in Lake Van might be exposed to endocrine-disrupting chemicals.

Metal levels in the liver, muscle, gill, intestine, and gonad of Lake Van fish (Chalcalburnus tarichi) with abnormal gonad.

Recently, an increasing number of studies have shown that Lake Van--the biggest soda lake in the world--is polluted due to an increasing population. Studies have shown abnormalities in the Lake Van fish (Chalcalburnus tarichi), the sole fish species that inhabits the lake. Unlike the vitellogenic and mature oocytes in normal gonads, abnormal gonads show large amounts of connective tissue and young oocytes. In this study, metal levels (nickel [Ni], copper [Cu], cobalt [Co], iron [Fe], zinc [Zn], cadmium [Cd], lead [Pb], and manganese [Mn]) in the muscle, liver, gill, intestine, and gonad of Lake Van fish with normal and abnormal gonads were assessed. Further, the metal contents in the wastewater from the wastewater treatment facility situated near Lake Van in Van City were assessed. All the metal levels, except that of Zn, were high in the Lake Van environment (P<0.05). The highest metal content in the tissues was for Fe, while the lowest level was for Co. The Pb level was found to be very high in both fish groups. Cd was not found in the tissues of both fish groups. The levels of Fe, Cu, Pb, and Mn were not significant in the tissues of both normal and abnormal fish groups. Zn level was significantly high in the livers and gonads of fish with abnormal gonads, and Co level was significantly high only in the livers (P<0.05). Consequently, high levels of Zn in the liver and gonads and high levels of Co in the liver may be factors causing the abnormal gonads in the Lake Van fish.

Determination of selected endocrine disrupting chemicals in Lake Van, Turkey.

In the present study, we investigated the distribution of 17ß-estradiol (E2), 17α-ethynylestradiol (EE2), alkylphenol ethoxylates (APEs) and organochlorine pesticides (DDE/DDT) in water and sediment samples in the Eastern Anatolia of Turkey, Lake Van, which is the largest soda lake in the world. The procedure consisted of solid phase extraction performed with OASIS HLB cartridges followed by non-competitive enzyme-linked immunosorbent assays (ELISA). The endocrine disrupting compounds E2, EE2, and DDT/DDE were detected in most of the lake samples with mean concentrations of 0.996 ± 0.304, 0.050 ± 0.022, and 0.749 ± 0.658 ng/L in water, respectively. Mean concentrations of E2, EE2 and DDT/DDE in sediment were 0.098 ± 0.053, 0.091 ± 0.072, and 1.281 ± 0.754 ng/g, respectively. APEs were not measured in the sediment samples. The EDCs levels in surface water and sediment samples were lower than that of other countries. The EDCs were also found in effluent and influent municipal sewage samples. Van city municipal wastewater treatment plant has no removal efficiency for EDCs.

Environmental regulation of mitochondria-rich cells in Chalcalburnus tarichi (Pallas, 1811) during reproductive migration.

Chalcalburnus tarichi is an anadromous cyprinid fish that has adapted to extreme conditions (salinity 22 ‰, pH 9.8 and alkalinity 153 mEq × l⁻¹) in Lake Van in eastern Turkey. Changes in immunoreactivity of Na⁺/K⁺-ATPase in gill tissue and osmolarity and ion levels in plasma were investigated in C. tarichi during reproductive migration. Physicochemical characteristics and ion levels in Lake Van were high compared freshwater. Plasma osmolality and plasma ion concentrations ([Na⁺], [K⁺] and [Cl⁻]) increased after transfer from freshwater to Lake Van. The mitochondria-rich (MR) cells of the gill were stained in both filament and lamellar epithelia of C. tarichi by immunocytochemistry with a specific antiserum for Na⁺/K⁺-ATPase in river fish samples. Density and area of MR cells were decreased in lake-adapted fishes. These results indicated that freshwater acclimation capacity is correlated with the size and distribution of MR cells in C. tarichi, in contrast to many teleost fishes.