Who is the“murderer”of the bloom in coastal waters of Fujian,China,in 2019?

On May 24-29,2019,a bloom occurring in Pingtan coastal areas of Fujian Province caused mass mortality of cage-cultured fish(Plectorhinchus cinctus and Pagrosomus major).During the bloom,two major causative organisms were present:Prorocentrum donghaiense(at a concentration of 1.46×10^7 cells/L)and an unknown naked dinoflagellate(4.58×10^6 cells/L).The naked dinoflagellate was isolated and cultured in this study,and its morphological features were examined using light microscopy and scanning electron microscopy.The large subunit(LSU)of the rRNA gene and the internal transcribed spacer(ITS)region of the naked dinoflagellate were also sequenced for field bloom samples and lab culture strains(PT-A and PT-B).On the basis of its morphological characteristics and molecular sequences,the unknown naked dinoflagellate was identified as Karlodinium digitatum.According to the phylogenetic analysis,the Karl.digitatum was most closely related to Karlodinium australe and Karlodinium armiger,and the three species clustered into a single clade of Karlodinium with bootstrap/posterior probability values of 95%/0.99 and 86%/0.99 inferred from LSU and ITS sequences,respectively.Karl.digitatum was first reported as Karenia digitata,a new harmful algal species bloomed in Hong Kong,China,in 1998.In present study,we gave a detailed morphological and phylogenetic description of Karl.digitatum and submitted the molecular sequences of this species to GenBank for the first time.

Characterization of the Complete Mitochondrial Genome of Arius dispar(Siluriformes: Ariidae) and Phylogenetic Analysis Among Sea Catfishes

The mitochondrial genome(mitogenome) was 16792 bp in length, containing 13 protein coding genes(PCGs), two rRNA genes(12 S rRNA and 16 S rRNA), 22 tRNA genes, and two main non-coding regions. Among these 37 genes, 28 genes were encoded on the heavy strand, while 9 genes were transcribed on the light strand. The non-coding regions of A. dispar included a control region, a light strand replication and another 11 intergenic spacers. The CR of A. dispar contained 8 conserved sequence blocks(CSBs), a termination-associated sequence(TAS) and a pyrimidine tract. Phylogenetic analysis based on 12 PCGs revealed that A. dispar was genetically closest to Arius arius. The families Schilbeidae, Claroteidae, Mochokidae, and Ariidae formed a closely evolved clade. Molecular information from this research introduces mitogenomice data of A. dispar and suggests the phylogenetic relationships among Siluriformes.