Effects of osmotic pressure, temperature and stocking density on survival and sexual reproduction of Craspedacusta sowerbii

The effects of osmotic pressure, temperature and stocking density on medusae survival of Craspedacusta sowerbii were examined. The medusae were shown to be sensitive to the variations of osmotic pressure. And the survival time was 〈90 h at 34 mOsm/L and it declined rapidly with rising osmotic pressure. The peak survival time of 〉200 h was recorded at 0.2 mOsm/L. Comparing with 27℃ and 32 ℃ treatments, 23 ℃ treatment yielded lower activities at a range of 8-13/min. However, there was a longer survival time. A non-linear relationship existed between survival time and stocking density. Lower density resulted in larger body size. And sexual reproduction resumed after breeding for 〉22 days. Newly-formed polyps and medusae appeared subsequently but only in the higher-density groups of 10, 14 and 18 ind./L. It suggested that the number of newly-formed polyps and medusae was highly dependent on stocking density. That is, a higher stocking density produced more organisms. However, newly-formed medusae died within one month and none grew a diameter of 〉5 mm.

Construction of a chromosome-level genome assembly for genome-wide identification of growth-related quantitative trait loci in Sinocyclocheilus grahami(Cypriniformes,Cyprinidae)

The Dianchi golden-line barbel,Sinocyclocheilus grahami(Regan,1904),is one of the“Four Famous Fishes”of Yunnan Province,China.Given its economic value,this species has been artificially bred successfully since 2007,with a nationally selected breed(“S.grahami,Bayou No.1”)certified in 2018.For the future utilization of this species,its growth rate,disease resistance,and wild adaptability need to be improved,which could be achieved with the help of molecular markerassisted selection(MAS).In the current study,we constructed the first chromosome-level genome of S.grahami,assembled 48 pseudo-chromosomes,and obtained a genome size of 1.49 Gb.We also performed QTL-seq analysis of S.grahami using the highest and lowest bulks(i.e.,largest and smallest size)in both a sibling and random population.We screened two quantitative trait loci(QTLs)(Chr3,14.9-39.1 Mb and Chr17,4.1-27.4 Mb)as major growth-related locations.Several candidate genes(e.g.,map2k5,stat1,phf21a,sox6,and smad6)were also identified,with functions related to growth,such as cell differentiation,neuronal development,skeletal muscle development,chondrogenesis,and immunity.These results built a solid foundation for in-depth MAS studies on the growth traits of S.grahami.

Restocking of Anabarilius grahami in Lake Fuxian,Southwest China:morphological and genetic effects

DEAR EDITOR,The restocking of the endangered Kanglang white minnow(Anabarilius grahami)in Lake Fuxian,China,has been conducted for 13 years.However,few studies have reported on the effectiveness of the captive breeding and release of this species.