Microscopic ovary features of Zebrafish were analyzed. Samples were fixed in Bouin's solution, mounted in parafin and cut into 6-7 µm-thick slices which were stained with Hematoxylin and Eosin (HE), methylene blue and using Periodic-acid Schiff method (PAS). The thin sections in ultramicrotome with the thickness of approximately 0,5-0,7 µm were examined by using Jeol electron microscope following contrasting with Uranyl Acetate-Lead Citrate. The zebrafish was an extremely dynamic organ in which follicles underwent asynchronous development. The oocytes of Zebrafish ovary were observed in various phases. The oocyte development of zebrafish was divided into four stages (primary growth, cortical alveolus, vitellogenic and mature oocyte). Oocyte diameters were observed to vary between 0.,08 mm and 0.76 mm.

In this study, bioaccumulation of cadmium (Cd) and lead (Pb) in Mediterranean mussels (Mytilus galloprovincialis Lamarck, 1819) at Bosphorus, Istanbul, Turkey, has been researched. Mussel samples hand-collected seasonally, between January, 2003 and December, 2004 from six stations in Bosphorus. The concentrations of Cd and Pb in the mussels were determinated by Atomic Absorption Spectrometry (AAS). The results of this study indicated that Cd and Pb were in higher concentrations in the Mussels of Bosphorus. The concentrations of these metals in soft tissues exceeded the acceptable levels for a food source for human consumption and these values are unacceptable for Turkish legal standards.

In sexually reproducing organisms, primordial germ cells (PGCs) give rise to the cells of the germ line, the gametes. In many animals, PGCs are set apart from somatic cells early during embryogenesis. This study explores the origin of primordial germ cells (PGCs) of the zebra fi sh and examines their morphology during early development (1 st day-15 th day). PGCs were selectively stained by the alkaline phosphatase histochemical reaction and viewed by light and electron microscopy from the time they are fi rst detectable in the yolk sac endoderm. PGCs occurred in the subendodermal space on the syncytial periblast; diff ering from the surrounding endodermal cells. Later the PGCs moved to between the blastoderm and yolk sac and transferred to the dorsal mesentery where they formed gonadal anlage with mesoderm cells. PGCs were easily distinguished from somatic cells by their morphology and low electron density of their nuclei. Under light microscopy, PCGs were rounded with a distinct cytoplasmic membrane.

A total of 23 ostracod taxa were found in 48 of 90 different water bodies (wetlands, springs, lakes, creeks, etc.) located at moderate to high elevation (530-1,095 m) in Diyarbakır province. The ecological tolerances and optimum values for environmental variables of 15 species were analyzed. Accordingly, maximum numbers of species were found between 700 and 800 m. Ostracod species and sampling sites along with seven environmental variables were ordinated with canonical correspondence analysis (CCA). The first axis of CCA explained 72% of the relationship between species and environmental variables. Of these, water temperature, redox potential and altitude were the most influential (P \ 0.05) factors for species. Based on habitat similarities, an unweighted pair group mean average dendrogram divided species into four clustering groups. Among the species, Potamocypris arcuata, Candona neglecta and Psychrodromus fontinalis had the highest optimum estimates for altitude, whereas P. arcuata, Herpetocypris brevicaudata and P. fontinalis exhibited the highest tolerances to altitude. While most species revealed unique tolerances and optimum values for different ecological variables, species with cosmopolitan characteristics had wider ranges of ecological tolerances and distribution amid the variety of habitats along elevational gradients.

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