Assessing the Status of Rotifer Mass Cultures

Rotifers are widely used as live larval feed in aquaculture. The stability of rotifer mass cultures, however, remains a critical unresolved problem. It would be useful to develop indicators that can assess the status of rotifer mass cultures and serve as an early warning of trouble. Indicators should be sensitive, easy to measure and have quick response time. Two indicators have been developed that fulfill these criteria: swimming activity and egg ratio (eggs per female). A swimming activity test is described based on the measurement of rotifer swimming over a grid. Results are obtained in minutes and are sensitive indicators of pH, un-ionized ammonia, starvation and temperature stress in the mass culture. For un-ionized ammonia, swimming activity is about nine times more sensitive than an LC₅₀ test, and maximum response occurs within ten minutes. Egg ratio is also a sensitive indicator of physiological stress, but there is a 18-24 h time lag between exposure to stress and a change in egg ratio. Egg ratios during log phase of population growth ranged from 0.5-1.2 and 0.13-0.5 during stationary phase. When egg ratio fell below approximately 0.13, rotifer populations declined. Monitoring of swimming activity and egg ratios should make it easier for aquaculturists to keep their rotifer cultures productive and stable.     

Deep-sea macroplanktonic sea cucumbers: suspended sediment feeders captured from deep submergence vehicle

Observations in situ confirm the swimming and feeding behavior in previously unreported dense assemblages of the holothurian Peniagone diaphana, at a depth of 2000 meters, off southern California. Proximate analysis of captured specimens indicates that this organism may represent a numerically significant, but low organic content member of many near-bottom deep-sea communities.     

Photopolymerization and Mass-Independent Sulfur Isotope Fractionations in Carbon Disulfide

Irradiation of gaseous carbon disulfide [CS2(g)] at 313 nanometers produces a dark brown aerosol of (CS2)x. Its thermal decomposition products include disulfur (S2), carbon monosulfide (CS), and (CS)x. The photopolymerization process is accompanied by a large mass-independent isotopic fractionation of sulfur (a 5 to 10 per mil sulfur-33 excess and a 61 to 84 per mil sulfur-36 deficit). Excess sulfur-33 has been observed in several classes of meteorites. Photochemical production of (CS2)x may be important in the origin and evolution of cosmochemical environments such as the presolar nebula, meteorites, asteroids, and planetary atmospheres.     

DNA Status on Thawed Semen from Fighting Bull: A Comparison Between the SCD and the SCSA Tests

The assessment of sperm chromatin status is compulsory in a complete spermiogram. Here we applied the sperm chromatin structure assay (SCSA) and the sperm chromatin dispersion (SCD) test to assess the chromatin status of three fighting bulls. Cryopreserved semen (two straws/bull) were analysed by duplicate after thawing and after 6 h at 37°C with and without oxidative stress (1 m m FE²⁺). Results (SCD: percentage of spermatozoa with halo; SCSA: SD-DFI, %DFI and HDS) were analysed for differences between bulls and treatments, sensitivity and specificity (receiver operating characteristic curves) and repeatability (repeatability coefficients as 2SD of duplicate differences).%DFI for the three bulls was below 2% at 0 h, indicating no risk for fertility according to previous reports. It increased slightly for two of the bulls after FE²⁺ treatment (%DFI < 5%) and more pronouncedly for the other bull (C, %DFI∼10%), which merits further investigation. SCD rendered higher percentage of halos for bull C, but could not discriminate between samples with and without oxidizing treatment (AUC: 0.52). SCSA (%DFI) showed a high discriminating ability between treatments (AUC: 0.96). The repeatability coefficient was also higher for SCD (5.9) than for %DFI (1.8), indicating lower repeatability for SCD. Overall, %DFI might be the most useful parameter for assessing sperm chromatin on fighting bull. SCD might yield different information than SCSA, hence further research is warranted.