Estimation of genetic parameters for disease‐resistance traits in Cynoglossus semilaevis (Günther, 1873)

The objective of this study was to estimate genetic parameters for three traits based on 28 Cynoglossus semilaevis families approximately 6 months of age (at least 5 cm total length), including trait_1 (survival of 26 families, 3434 individuals in total subjected to challenge tests with Edwardsiella tarda), trait_2 (survival of 20 families, 2016 individuals in total subjected to challenge tests with Vibrio anguillarum) and trait_3 (survival of 27 families, 9340 individuals tagged at circa 180 days of age and reared in indoor ponds for circa another 5 months). The result showed that there were large differences in the survival of the families after challenge (11.11–65.31% for E. tarda and 9.18–70.54% for V. anguillarum). Additionally, the survival of families reared in indoor ponds was also different, varying from 21.00% to 73.67%. Heritabilities of the three traits varied from 0.14 to 0.26, as estimated by the linear model (LM) and the threshold model (TM). The trait_1 heritabilities (0.26 and 0.19 estimated by LM and TM) were higher than those of the others (0.20 and 0.23 estimated by LM, 0.14 and 0.19 estimated by TM). The estimates of heritabilities using LM were consistently higher than those of TM in this study. There were significant medium genetic correlations of 0.44 and 0.42 between trait_1 and trait_2 obtained from LM and TM (P < 0.05). However, very low and non‐significant genetic correlations of trait_1 and trait_3 (?0.10 for LM, ?0.05 for TM), as well as those of trait_2 and trait_3 (0.05 for LM, 0.04 for TM) were obtained. Therefore, indirect selection for trait_1 and trait_2 was effective, but almost ineffectual for trait_1 and trait_3 as well as trait_2 and trait_3. Otherwise, there was no significant difference in the predictive abilities of LM and TM. Two families resistant to both Edwardsiella tarda and Vibrio anguillarum were selected plus one family resistant to both Vibrio anguillarum and naturally infected by unknown pathogens through family selection. As there was very low and non‐significant genetic correlation of trait_3 and trait_1 as well as trait_2, superior strains are anticipated with the ability to resist two or more kinds of diseases, through the crossing of families selected for the three traits described above. The results support the hypothesis that genetic variation exists for disease survival, which could be used to design a breeding program for selecting strains of Cynoglossus semilaevis with high disease resistance.     

Experimental evaluation of calcein and alizarin red S for immersion marking of silver carp Hypophthalmichthys molitrix (Valenciennes, 1844)

Calcein (CAL) and alizarin red S (ARS) at concentrations of 50–200 and 150–300 mg/L, respectively, were used for immersion marking of juvenile silver carp Hypophthalmichthys molitrix (79.65 ± 2.11 mm total length, mean ± SD). The marked fish were kept in separate tanks (0.012 individuals per litre, rearing temperature 18.4–25.7°C) for 360 days. Each experimental treatment group consisted of three replicates (16 individuals per replicate). Immersion for 24 h produced detectable marks in the sagittae, lateral line and non‐lateral line scales, and fin rays (dorsal, pectoral, ventral, anal, and caudal) at 360 days post‐marking. Acceptable marks in the sagittae were observed for CAL at concentrations of 150–200 mg/L and for ARS at concentrations of 200–300 mg/L. Fluorescent marks were poorly visible in all non‐lateral line scales from both the CAL‐ and ARS‐treated groups. Acceptable fluorescent marks in the lateral line scales and fin rays were detected for CAL at concentrations of 150–200 and 100–200 mg/L, respectively, and for ARS at concentrations of 200–300 and 150–300 mg/L, respectively. In particular, optimal marks were observed at the highest concentrations investigated in lateral line scales (200 mg/L CAL, 300 mg/L ARS) and fin rays (200 mg/L CAL, 200–300 mg/L ARS). There was no significant difference in the survival or growth of marked fish compared to controls throughout the experiment (P > 0.05).     

Length–weight and length–length relationships of seven fish species from the Ili River and tributaries,northwest China

Length–weight and length–length relationships were estimated for seven fish species belonging to four families from the Ili River and its tributaries, northwest China. From April to October 2013 and May to October 2014, specimens were collected monthly for a total of 783 specimens. This study presents the first references on LWRs for Diptychus maculates, Gymnodiptychu dybowskii, Perca schrenkii, Silurus meridionalis and Schizothorax pseudoaksaiensis pseudoaksaiensis, and LLRs for G. dybowskii, P. schrenkii, S. meridionalis, S. pseudoaksaiensis pseudoaksaiensis, Triplophysa strauchii and Triplophysa stoliczkai.     

Temporal rhythm of petal programmed cell death in Ipomoea purpurea

• Flowers are the main sexual reproductive organs in plants. The shapes, colours and scents of corolla of plant flowers are involved in attracting insect pollinators and increasing reproductive success. The process of corolla senescence was investigated in Ipomoea purpurea (Convolvulaceae) in this study.
• In the research methods of plant anatomy, cytology, cell chemistry and molecular biology were used.
• The results showed that at the flowering stage cells already began to show distortion, chromatin condensation, mitochondrial membrane degradation and tonoplast dissolution and rupture. At this stage genomic DNA underwent massive but gradual random degradation. However, judging from the shape and structure, aging characteristics did not appear until the early flower senescence stage. The senescence process was slow, and it was completed at the late stage of flower senescence with a withering corolla.
• We may safely arrive at the conclusion that corolla senescence of I. purpurea was mediated by programmed cell death (PCD) that occurred at the flowering stage. The corolla senescence exhibited an obvious temporal rhythm, which demonstrated a high degree of coordination with pollination and fertilization.