Spermatogenesis in teleost: insights from the Nile tilapia (Oreochromis niloticus) model     

D.A.R. Vilela  S.G.B. Silva  M.T.D. Peixoto  H.P. Godinho  L.R. França 《Fish physiology and biochemistry》2003,28(1-4):187-190

The morphometric study of spermatogenic cysts in sexually mature tilapias, during the evolution of spermatogenesis, showed a dramatic increase in both number of germ cells and cyst volume. However, the opposite trend was observed for germ cell size. Nevertheless, the number of Sertoli cells increased gradually up to leptotene/zygotene cysts, stabilizing thereafter. Based on the number of spermatids supported by each Sertoli cell and compared to mammals, Sertoli cell efficiency in tilapias is remarkably high. Sertoli cell proliferation was frequently observed, mainly in spermatogonial cysts, and probably is the major factor related to the testis growth and the increase in sperm production that normally occurs in adult tilapias. The combined duration of spermatocytes (5 days) and spermiogenic (5–6 days) phases of spermatogenesis in fish kept at 25 °C was 10–11 days. Mainly due to acceleration in meiosis, these two phases lasted a total of 6 days in tilapias kept at 30 °C, in the opposite way, at 20 °C spermatogenesis was arrested at pachytene spermatocytes. To our knowledge, this is the most comprehensive investigation performed up to date on testis morphometry and function in adult tilapias.  相似文献   

The evaluation of secondary stress response of grass carp (Ctenopharyngodon idella, Val. 1844) after exposing to the saline water     

H. Yavuzcan-Yıldız  M. Kırkavgaç-Uzbilek 《Fish physiology and biochemistry》2001,25(4):287-290

The stress response of grass carp to salinity was evaluated assessing the levels of hematocrit, leucocrit, plasma glucose, sodium, potassium and calcium. Mean hematocrit values increased following exposure to salinity. Mean leucocrit values elevated after exposure to salinity for 24 h, then decreased. Mean plasma glucose increased during saline exposure for 48 h and then decreased to normal values. Plasma sodium and chloride levels were increased to their highest values after 48 h. While plasma potassium value increased with the exposure time, plasma calcium values were not affected by salinity exposure.  相似文献   

Selective control of polyamide dyeing with acid dyes using hydroxypropyl-β-cyclodextrin     

Jorge G. Santos  Teresa Miranda  Graça M. B. Soares 《Fibers and Polymers》2014,15(4):788-793

The effect of hydroxypropyl-β-cyclodextrin (HPβCD) in the dyeing of polyamide fabric was investigated under conditions that mimic industrial dyebaths where dye mixtures are used. The dyes used were Telon Red BN, Telon Yellow A-2R, and Telon Blue RR. The blue dye complexed with HPβCD whereas the other dyes did not do so under the conditions used. The dyeing results were compared with those obtained using a traditional retarding agent, Albegal B. The exhaustion dyeing data showed that HPβCD mainly affected the dyeing behavior of the blue dye that became encapsulated. In the case of the yellow and red dyes, changes in the overall kinetics of dyeing were observed, resulting in modified exhaustion profiles. In comparison, Albegal B retarded the blue dyeing process and increased the rate of exhaustion of the yellow dye while the exhaustion curve of red dye remained unchanged. The color uniformity of the dyed polyamide was improved when HPβCD was used. This resulted from the more controlled exhaustion rate during the critical phase of the dyeing process.  相似文献   

Estimation of the area-specific suspended sediment yield from discrete samples in different regions of Belgium     

Van Campenhout  Jean  Petit  François  Peeters  Alexandre  Houbrechts  Geoffrey 《Journal of Soils and Sediments》2022,22(2):704-729

Journal of Soils and Sediments - Suspended sediment transport, which represents the majority of the sediment load, has been studied across very different scales and in a wide variety of regions and...  相似文献   

Determining home range,changes in habitat use with time,and the threats to an endangered freshwater turtle (Rafetus euphraticus) in Turkey     

Yusuf Bayrakcı  Dinçer Ayaz  Luca Luiselli 《水产资源保护:海洋与淡水生态系统》2021,31(11):3276-3290

1. The Euphrates softshell turtle (Rafetus euphraticus) is the most threatened chelonian species in the Middle East, where it is endemic to the Tigris and Euphrates basins. Since the ecology of this species is little known, it is difficult to plan any reliable action for its correct management and conservation.
2. To enhance the scientific knowledge on R. euphraticus, and to establish a science-based management strategy, a detailed investigation was undertaken on the distribution, habitat, activity and home range of R. euphraticus in Turkey. The previous distribution records in Turkey are for the 1990s; thus, this study is the first comprehensive field research on the species after nearly 3 decades.
3. There was a significant sexual size dimorphism in the Turkish population, with males larger than females.
4. Four individuals were radiotracked for 1 year. The mean home range was highly variable depending on how it was calculated, but that of males was considerably greater than that of females by all methods used.
5. A quantitative evaluation was made of habitat change with time. The land cover classes potentially available to turtles in the Euphrates River basin increased by more than 100% between the 1990s and 2018: 92% of this enhancement was derived from water bodies and coastal lands.
6. Fifteen dams have been built in the lower part of the basins in the last 30 years. In addition, continuing human interactions have caused the fragmentation or destruction of suitable habitats for R. euphraticus.
7. The factors threatening R. euphraticus were assessed and a conservation action plan was developed. Some objectives such as monitoring and creating awareness of this action plan have been met while others are still waiting to be achieved.

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The Effect of Live and Artificial Diets on Growth, Survival, and Trypsin Activity in Larvae of Penaeus indicus   总被引：4，自引：0，他引：4  

Metin  Kumlu D. A. Jones 《Journal of the World Aquaculture Society》1995,26(4):406-415

In this study, partial and total replacement of live diets (microalgae and Artemia nauplii) with microencapsulated diets (MED) are demonstrated for larval culture of P. indicus . Slower growth and lower survival rate of larvae fed experimental MED were significantly improved by a supplement of 15 cells/μL frozen mixed algae (1:2, Tetrtaselmis and Skeletonema ) during protod stages (PZ1–PZ3). This low level of algal supplement to MED resulted in survival (85–92%) equal to that obtained from control live diets (91%) during protod stages. These significant improvements in larval growth and survival are likely to be due to higher larval digestive enzyme activities and hence more efficient digestion of the artificial diet by the larvae. Like other penaeids, P. indicus larvae show high total and tissue trypsin activities during PZ stages, with a peak at mysis stage 1 (M1), and a decrease during subsequent stages when fed on conventional live diets of algae followed by Artemia during mysis stages. Larvae fed 15 ceUs/μL mixed frozen algae in addition to MED demonstrated a significantly higher trypsin activity throughout herbivorous larval stages in comparison to larvae fed solely on MED. A freeze dried alga Rhinomonas reticulata incorporated into a MED at 23Vo (v/v) induced larval trypsin activity equal to that produced by live algae. Hence, the algal substances, which trigger digestive enzyme production, may be retained within the microcapsules. At mysis stages, however, addition of live prey (one Artemia/ mL) to cultures fed with MED significantly improved growth and survival although it depressed trypsin activity. For mysis stages it appears that the use of predigested ingredients is necessary to improve the digestibility of formulated diets.  相似文献   

Occurrence of Pesticides in Water, Sediments, and Fish Tissues in a Lake Surrounded by Agricultural Lands: Concerning Risks to Humans and Ecological Receptors     

Nelson Abrantes  Ruth Pereira  Fernando Gonçalves 《Water, air, and soil pollution》2010,212(1-4):77-88

Lake Vela (Littoral Centre of Portugal) is considered a natural habitat with community interest and consequently was included in the Natura 2000 Network. However, this freshwater ecosystem has been potentially exposed to diffuse pollution generated by agricultural and livestock activities, which seriously compromise its ecological balance. As part of the Ecological Risk Assessment (ERA) proposed for Lake Vela, this study aimed to evaluate the occurrence of pesticides in different compartments: surface water, groundwater, sediments, and fish tissues. Moreover, to assess potential concerning effects on ecosystem and human health, the measured concentrations of pesticides were compared with regulatory and toxicological benchmarks. The results confirmed the presence of high concentrations of pesticides, including organochloride pesticides banned decades ago, in surface water, groundwater, and sediment. The measured concentrations of pesticides, compared with toxicological benchmarks, indicated that harmful effects are likely for aquatic species due to the presence of alachlor, aldrin, and dieldrin. Additionally, the concentrations of pesticides detected in groundwater were also above the recommended safety levels for drinking water, which constitutes a concern for the local population’s health. Results also showed an accumulation of alachlor in predator and benthic fish species which could represent a risk to human consumers and particularly to the regular fish predators (e.g., otters and birds). This study, as the first exposure characterization performed on the Lake Vela system, constitutes valuable and useful information for the ERA process. Although this preliminary assessment of risks should be continued and confirmed through a weight-of-evidence approach, it had already unraveled how concerning are the problems in this ecosystem and the urgency of implementing restoration measures to guaranty its sustainability. Furthermore, this study reinforces the importance of evaluating similar freshwater ecosystems that are also highly threatened by diffuse pollution.  相似文献   

Chromosomes of salmon (Salmo salar) by leukocyte culture     

Anne-Françoise Grammeltvedt 《Aquaculture (Amsterdam, Netherlands)》1975,5(2):205-209

Chromosome preparations from salmon (Salmo salar) were obtained by means of leukocyte culture. The chromosome number varied from 55 to 60 with a clear maximum of 2n = 58. The chromosomes are tentatively grouped as follows: group A, two large submetacentrics; group B, 14 metacentrics; group C, two large telocentrics; group D, 22 medium telocentrics; group E, 18 small telocentrics.  相似文献   

The effect of various nitrogen fertilizers on zinc (zn) availability in non calcic brown forest soils     

Aydin Adiloglu  Sevinç Adiloglu  Esin Gonulsuz  Nureddin Oner 《Archives of Agronomy and Soil Science》2013,59(6):601-606

In this article the effect of different nitrogen fertilizer application on the availability of zinc (Zn) content in non calcic brown forest soil was investigated. For this purpose increasing rates of NH₄Cl, (NH₄)₂S0₄; NH₄N0₃ and Ca(N0₃)₂.4H₂0 fertilizers were applied for having different physical and chemical properties in two soil samples. An incubation experiment was carried out over 4 months. The available Zn content of the soils was determined each month. According to the results the highest available Zn content of the soils was obtained from NH₄Cl applied to the soils followed by (NH₄)₂S0₄; NH₄N0₃ and Ca(N0₃)₂.4H₂0 application to soil. At the end of the experiment the average available Zn content of non calcic brown forest soils for NH₄Cl, (NH₄)₂S0₄; NH₄N0₃ and Ca(N0₃)₂.4H₂0 fertilizers are 0.93, 0.91, 0.88 and 0.77 mg kg^?1, respectively.  相似文献   

Isozyme analysis of an active cassava germplasm bank collection     

Angélica V. V. Montarroyos  Marco A. G. de Lima  Elton O. dos Santos  José G. E. de França 《Euphytica》2003,130(1):101-106

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