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Öğe Abnormalities in the amphids of free-living nematodes in the black sea: Is it atavism or result of a modern morpho-functional adaptation to environmental changes and the nascent process of microevolution?(Nova Science Publishers, Inc., 2016) Sergeeva, Nelli G.; Ürkmez, Derya; Revkova, Tatiana N.In this chapter we aim to summarize our long-term data (1988-2015) about the abnormalities detected in the development of the vital chemoreceptor organs (amphids) of 49 nematode species from the Black Sea. The total list of species includes 28 valid species and 21 morphotypes, systematic position of which have been identified only to genus level as well as individuals close to a valid species (cf.), however, they require further study and clarification in our view. Amphid abnormalities are characterized by a wide spectrum of appearances. Accordingly, they may have a non-standard number of elements of a species-specific form (instead of two elements they may have 1 or 3-5); one element of amphid may be underdeveloped or not have a speciesspecific form; the topography of amphids in relation to the front edge of the head and to the axis symmetry of the body may be disturbed. Anthropogenic impact on the Black Sea ecosystem is steadily increasing. Its negative effect is revealed in the extinction of species, community perturbations, serious physiological changes in organisms, resulting in different pathological phenomena. It is obvious that the occurrence of specific abnormalities in the vital organs of the same nematodes species is a result of chromosomal mutagenesis. Repeatability and the wide distribution of species with these types of abnormalities in different regions of the basin are shown in this chapter. The issues indicated in this chapter require future research: 1. what is the specific cause of the amphid abnormalities in nematodes? 2. Are these amphid abnormalities offer an advantage or a disadvantage compared to the “normal” organs for organisms inhabiting polluted ecosystems or a life under the impact of climate change? 3. Why similar morphological abnormalities are not recorded in nematodes from the other seas? Are these chemoreceptor organ abnormalities in nematodes unique for the Black Sea? 4. Is this phenomenon shows the nascent process of microevolution of nematode fauna in the Black Sea?. © 2016 Nova Science Publishers, Inc.Öğe Current views on the diversity and distribution of deep-water meiobenthos at the Turkish shelf (Black Sea)(Centre for Biodiversity of Montenegro, 2017) Sergeeva, Nelli G.; Ürkmez, DeryaDeep-water meiobenthos of Turkish shelf has been evaluated at the Black Sea exit of Istanbul Strait (Bosphorus) and off Sinop peninsula as a result of three scientific cruises. Taxonomic diversity of meiobenthos communities was studied at the Black Sea exit of Bosphorus on a transect with a depth range of 75-300 m. The bottom sediments were collected at the area during two cruises, on board RV "Arar'' (of Turkey) and ''Maria S. Merian" (of Germany) in November 2009 and April 2010, respectively. Data on meiobenthos inhabiting both normoxic and extreme conditions was collected in the studied area and meiobenthos composition included 26 high level taxa. In addition, 2-3 morphotypes of benthic fauna were recorded as incertae sedis, which require further study. The number of higher taxa decreased from 22 to 14-8 when switching from oxygenic conditions (50-125 m) to the anoxic hydrogen sulphide environment (226-300 m). The constant components of meiobenthos included protists (Ciliophora, Gromiidea and soft-shelled Foraminifera), and metazoans were constantly represented by Nematoda and Harpacticoida. In 2011, a quantitative study on meiobenthic composition of the oxic/anoxic interface at the western part off Sinop Peninsula (Southern Black Sea) has also been investigated. The material was collected by ROVs during the expedition (Black Sea Leg) of the exploration vessel (E/V) Nautilus. Results showed that the taxa composition of meiobenthos ranged from 4 to 10 major groups. Free-living marine nematodes were numerically the dominant taxon at each station. Total abundances decreased in parallel to increasing water depth, hence decreasing oxygen levels.Öğe Meiobenthic nematodes at the deep oxic/anoxic boundary of the Black Sea (Istanbul Strait Outlet Area) with new records for Turkey(Elsevier, 2021) Sergeeva, Nelli G.; Urkmez, Derya; Revkova, TatianaInvestigations were conducted at nine stations along the oxic/anoxic interface in the Istanbul Strait's (Bosphorus) outlet area of the Black Sea (ISBS). Present work stands as the first study on the distribution patterns of nematodes along water depths between 75 m and 300 m at the ISBS and gives information on the variability of the trophic relationships of nematodes with oxygen depletion and the presence of toxic hydrogen sulfide in the environment. Nematodes were represented by 137 species from 63 genera and 30 families at the studied depths. 34 species were reported for the first time from Turkey. The presented results showed that most of the nematode species in this region were identified only to the genus and even only to the family or order level. This suggested that the fauna of free-living nematodes of the Black Sea as a whole is much more diverse than is currently known, and requires further taxonomic studies. (c) 2021 Elsevier B.V. All rights reserved.Öğe MEIOBENTHIC RESEARCH ON THE BLACK SEA SHELF OF TURKEY: A REVIEW(Turkish Marine Research Foundation-Tudav, 2017) Urkmez, Derya; Sezgin, Murat; Sergeeva, Nelli G.[No abstract available]Öğe Significant occurrence of Musellifer profundus Vivier, 1974 (Gastrotricha, Chaetonotida) in the Black Sea(Pensoft Publishers, 2019) Sergeeva, Nelli G.; Ürkmez, Derya; Todaro, M. AntonioSpecimens of the gastrotrich genus Musellifer are recorded for the first time from the Black Sea. These specimens, identified as M. profundus Vivier, 1974, were found in sediment samples collected at various depths (22-135 m) and from waters characterized by low salinity (17.3-18.62‰) and varying levels of oxygen (2.43-299.59 µM). Three specimens were found from the Istanbul Strait (Bosphorus) outlet area of the Black Sea (Turkey) and 2 were found along the southern and southeastern shelf of the Crimean Peninsula (Russia), from the Yalta Gulf and the Feodosiya Gulf. © Sergeeva et al.
