High production of transfer RNAs identifies the presence of developing oocytes in ovaries and intersex testes of teleost fish

5S rRNA is highly transcribed in fish oocytes and this transcription levels can be used to identify the presence of oocytes in the intersex testes of fish exposed to xenoestrogens. Similar to 5S rRNA, tRNAs are transcribed by RNA polymerase III (Pol-III) in eukaryotes, so this study focuses in the analysis of the levels of expression of tRNAs in the gonads (ovaries and testes) of eight teleost species as a possible new oocyte molecular marker. Total RNA extracted from gonads of six commercial teleost species in the Biscay Bay, from the pollution sentinel species thicklip grey mullet (Chelon labrosus) known present intersex testes in response to xenoestrogens in Gernika estuary and from the laboratory model species Danio rerio were analysed through capillary electrophoresis. Bioanalyzer electropherograms were used to quantify the concentrations of tRNAs, 5S and 5.8S rRNA. All studied ovaries expressed significantly higher levels of tRNAs and 5S rRNA than testes. A tRNA to 5.8S rRNA index was calculated which differentiates ovaries from testes, and identifies some intersex testes in between testes and ovaries in mullets. The tRNA/5.8S ratio was highest in ovaries in previtellogenic stage, decreasing towards maturity. Thus, strong oocyte expression of tRNAs is an additional proof of high activity levels of Pol-III during early stages of oocyte development in teleost ovaries. Incidentally, we observed that miRNA concentrations were always higher in testes than ovaries. The indexing approach developed in the present study could have multiple applications in teleost reproduction research and in the development of early molecular markers of intersex condition.This work has been supported by project Born2bEgg (Spanish MCIN & EU-FEDER/ERDF (PGC2018-101442-B-100) and by the grants to consolidated research projects of the Basque Government (IT1302-19 and IT1743-22). We are thankful to the Biscay Bay Environmental Biospecimen Bank (BBEBB; PiE-UPV/EHU) for providing mullet tissues

Method for the molecular and quantitative identification of oocytes and their developmental stage in teleost fish gonads

Fish display diverse reproductive strategies and their gametogenesis is influenced by numerous genetic, physiological and environmental factors. The analysis of 5S rRNA expression levels in gonads has been proposed as useful method for the molecular identification of the presence of oocytes in fish tissues. The present method provides an easy and unbiased approach to analyse the expression of tRNAs and 5S rRNA in teleost gonads and stablish the presence and developmental stage of oocytes. Total RNA extracted from gonads is analysed through capillary electrophoresis in a Bioanalyzer 2100 (Agilent Technologies) using Small RNA Assays. Electropherograms allow quantifying the concentrations of tRNAs, 5S rRNA and 5.8S rRNA per sample and calculate their tRNA/5.8S rRNA and 5S/5.8S rRNA indices. Both indices clearly differentiate ovaries from testes and can be used to identify testes that present oocytes due to exposure to environmental xenoestrogens. The tRNA/5.8S and 5S/5.8S indices show the highest values in ovaries in previtellogenic stage, values decreasing as they advance towards maturity. • Detailed molecular method to sex fish and quantitatively identify the maturity stage of females. • tRNA levels in gonads can help in the study of teleost reproduction (female fecundity assessment, molecular gonad sexing) and environmental health assessment

Impact of commercial probiotics application on growth and production of giant fresh water prawn (Macrobrachium Rosenbergii De Man, 1879)

The study was conducted to observe the impact of commercial probiotics application on growth and production performance of fresh water prawn (Macrobrachium rosenbergii) from August 2011 to March 2012. There were four experimental groups viz (a) control or without probiotics treated prawn (T1), (b) feed probiotics- Zymetin (T2) treated prawn, (c) soil probiotics- Super PS (T3) treated prawn and (d) Both Zymetin and Super PS (T4) treated prawn. Twelve ponds (each 120 m2) were used where stocking density was 2/m2 for all treatments and control and each was triplicated. After pond preparation, prawn PL was reared in the nursery pond for 45 days to become juvenile. At the time of stocking in growout ponds, average body weight of juvenile prawn was 1.04 g. After eight months (240 days) of culture, the mean final weight became 39.5 ± 12.03, 43.4 ± 14.91, 48.0 ± 16.73 and 51.6 ± 15.58 g in T1, T2, T3 and T4 respectively. Significance difference was found among all treatments and T4 showed highest growth. The SGR was found to be 1.50 ± 0.13, 1.53 ± 0.13, 1.58 ± 0.13 and 1.61 ± 0.11 (%BW/day) in T1, T2, T3 and T4 respectively and the difference was significant. The survival rate did not differ significantly but highest survival rate was found in T4 (90%). The average FCR was significantly lowest in T4 (1.39) and highest in T1 (1.9). The net average production was found to be significantly higher in T4 (914 kg/ha) which was 35% and 21 % higher than the control group (T1) and feed probiotics (T2) respectively. Water and soil quality parameters were measured and were within the culturable range. The production of probiotics treated ponds was always higher than without probiotics treated ponds but highest growth and production were found in T4 where Zymetin and Super PS were used combinedly. The results of this study can be applied in the farmer’s pond to increase the total production of prawn in the country

SCHeMA EU Project Summer School Report (Bilbao June 16 – 17, 2016): Conference Report

This conference report describes the training activities that took place in the frame of the Integrated in Situ Chemical MApping probe (SCHeMA) summer school organized from the 14th to the 16th of June 2016 in Bilbao (Spain)