[Spatiotemporal variation patterns of water quality of Taoranting Lake, Beijing of China].

By the methods of cluster analysis, discriminant analysis, and factor analysis, this paper studied the spatiotemporal variations of water quality of Taoranting Lake, a typical eutrophic urban landscape lake in Beijing, from March to November 2011. At temporal scale, the water quality of the Lake could be grouped into three periods which corresponded to the rainy season, normal season, and dry season in Beijing, respectively, reflecting an obvious temporal variation. At spatial scale, the water quality of the Lake at five sampling sites could be grouped into two groups, implying the different pollution degree. Water temperature, pH, transparency (SD), CODMn, total suspended solid (TSS) , and Chl-a content were the main factors affecting the temporal variation of the water quality, and the eutrophication of the water body was mainly controlled by the water temperature and Chl-a, total nitrogen, and total phosphorous contents. The effects of TSS and organic pollution should be also paid more attention.

Cryoprotectants protect medaka (Oryzias latipes) embryos from chilling injury.

This study was conducted to investigate the effect of six cryoprotectants (dimethyl sulfoxide (DMSO), glycerol (Gly), methanol (MeOH), ethylene glycol (EG), 1,2-propylene glycol (PG) and N,N-dimethylformamide (DMF) on the survival of medaka (Oryzias lapites) embryos at low temperatures (0 and -5C). Firstly, the embryos at 8 to 16-cell stages were exposed to different concentrations (1 to 4 mol per L) of DMSO, Gly, MeOH, EG, PG and DMF for 40min at 26C. After removal of the cryoprotectants (CPAs), the embryo survivals were assessed by their development into live fries following 9 day of culture. The results showed that the higher concentration of the CPA, the lower survival of the embryos; and that the toxicity of the six CPAs to medaka embryos is in the order of PG < MeOH = DMSO < Gly < EG < DMF (P < 0.05). Secondly, based on the results obtained above, embryos at 8 to 16-cell stages or other stages were exposed to 2 mol per L of PG, MeOH or DMSO for up to 180 min at 0C and up to 80 min at -5C respectively. The 8 to 16-cell embryos treated with MeOH at low temperatures showed highest survival. Thirdly, when embryos at different stages were treated with 2 mol per L of MeOH at -5C for 60 min, 16-somite stage embryos showed highest survival, followed by 4-somite, neurula, 50 percent epiboly, blastula, 32-cell and 8 to 16-cell embryos. These results demonstrated that PG had the lowest toxicity to medaka embryos among the six permeable CPAs at 26C, whereas MeOH showed highest cryoprotective efficiency under chilling conditions and chilling injury decreased gradually with the development of medaka embryos.

OPS vitrification of mouse immature oocytes before or after meiosis: the effect on cumulus cells maintenance and subsequent development.

Cryopreservation can cause cumulus cell damage around the immature oocytes, which may result in poor subsequent development. To evaluate the effect of the meiosis stage on the cumulus cell cryoinjury and determine the suitable stage for cryopreservation in immature oocytes, mouse oocytes at germinal vesicle (GV) and germinal vesicle breakdown (GVBD) stages were vitrified using open pulled straw (OPS) method. Cumulus cells damage was scored immediately after thawing by double-fluorescent staining. The survival rate of the oocytes was evaluated and the subsequent development of oocytes was assessed through in vitro culture (IVC) and in vitro fertilization (IVF) separately. After vitrification, a higher proportion of cumulus cells of GV oocytes were damaged than those of GVBD and untreated control groups. The survival rate of vitrified GVBD oocytes (94.1%) was significantly higher (p < 0.05) than that of GV oocytes (85.4%). Oocytes vitrified at GVBD stage (55.7%) showed similar cleavage rate compared to those at GV stage (49.2%), but significantly higher (p < 0.05) blastocyst rate (40.9% vs. 27.4%). These results demonstrate that oocytes at GVBD stage remain better cumulus membrane integrity and developmental ability during vitrification than those at GV stage, indicating they are more suitable for immature oocytes cryopreservation in mice.

[Relationships between copepods and Eriocheir sinensis larvae in ecological breeding ponds].

The study on the relationships between two copepod species Eurytemor affinis and Sinocalanus tenellus and Chinese mitten crab Eriocheir sinensis larvae in the ecological breeding ponds of E. sinensis larvae in Liaohe Delta district of Panjing City, Liaoning Province showed that E. affinis and S. tenellus had significant effects on the survival rate of first stage zoae (Z1). The higher the density of the two copepod species, the lower the survival rate of Z, was (P < 0.01). Third stage zoae (Z3) could prey on the copepods nauplii, and the feeding amount was increased with the increasing density of the nauplii (P < 0.01). Fifth stage zoae (Z5) and megalopae could easily prey on E. affinis, but not on S. tenellus. The megalopae yield in the ecological breeding ponds was negatively correlated with the quantity of the copepods during early breeding stage of E. sinensis larvae, and there was a significant difference among the megalopae yields when different quantity of copepods existed (P < 0.01). Some measures for controlling and utilizing the copepods in ecological breeding ponds of E. sinensis larvae were put forward.