Species of Artemia are regionally endemic branchiopod crustaceans composed of sexual species and parthenogenetic lineages, and represent an excellent model for studying adaptation and speciation to extreme and heterogeneous hypersaline environments. We tested hypotheses of whether populations from the Tibetan Plateau belong to A. tibetianaAbatzopoulos, Zhang & Sorgeloos,1998 and whether a population from Kazakhstan is a new species, using other Asian species of Artemia as outgroups. We conducted a multitrait phylogenetic study based on the complete mitogenome, mitochondrial (COI, 12S, 16S) and nuclear (microsatellites, ITS1) markers, and a suit of uni- and multivariate morphological traits. Our results led to the discovery of two new species, one from the Tibetan Plateau (Haiyan Lake) in China (Artemia sorgeloosin. sp.) and a second from Kazakhstan (Artemia amatin. sp.). Our analysis demonstrate that A. tibetiana and A. amatin. sp. are monophyletic, whereas A. sorgeloosin. sp., and A. tibetiana are polyphyletic. Evolutionary relationships based on mitochondrial and nSSR markers suggest that A. tibetiana may have arisen from a past hybridization event of a maternal ancestor of A. tibetiana with A. sorgeloosin. sp. or its ancestor. We present the complete mitogenome of A. tibetiana, A. amatin. sp., and A. sorgeloosin. sp. We also provide a novel taxonomic identification key based on morphology, emphasizing the phenotype as a necessary component of the species concept.
In the previously published mitochondrial genome sequence of Artemia urmiana (NC_021382 [JQ975176]), the taxonomic status of the examined Artemia had not been determined, due to parthenogenetic populations coexisting with A. urmiana in Urmia Lake. Additionally, NC_021382 [JQ975176] has been obtained with pooled cysts of Artemia (0.25 g cysts consists of 20,000–25,000 cysts), not a single specimen. With regard to coexisting populations in Urmia Lake, and intra- and inter-specific variations in the pooled samples, NC_021382 [JQ975176] cannot be recommended as a valid sequence and any attempt to attribute it to A. urmiana or a parthenogenetic population is unreasonable. With the aid of next-generation sequencing methods, we characterized and assembled a complete mitochondrial genome of A. urmiana with defined taxonomic status. Our results reveal that in the previously published mitogenome (NC_021382 [JQ975176]), tRNA-Phe has been erroneously attributed to the heavy strand but it is encoded in the light strand. There was a major problem in the position of the ND5. It was extended over the tRNA-Phe, which is biologically incorrect. We have also identified a partial nucleotide sequence of 311 bp that was probably erroneously duplicated in the assembly of the control region of NC_021382 [JQ975176], which enlarges the control region length by 16%. This partial sequence could not be recognized in our assembled mitogenome as well as in 48 further examined specimens of A. urmiana. Although, only COX1 and 16S genes have been widely used for phylogenetic studies in Artemia, our findings reveal substantial differences in the nucleotide composition of some other genes (including ATP8, ATP6, ND3, ND6, ND1 and COX3) among Artemia species. It is suggested that these markers should be included in future phylogenetic studies.
The complete mitochondrial genome of Sarcophyton trocheliophorum was completed using nextgeneration sequencing (NGS) method. The mitochondrial genome is a circular molecule of 18,508 bp in length, containing 14 protein-coding genes, two ribosomal RNA genes and one transfer RNA gene (Met-tRNA). The base composition is 30.45% A, 16.03% C, 19.13% G, and 34.40% T, with an A þ T content of 64.85%. A phylogenetic analysis of Alcyoniidae showed that genus Sarcophyton had the closest relationship with Sinularia.
The mitochondrial genome of Sinularia maxima was completed using next-generation sequencing (NGS) method. The mitochondrial genome is a circular molecule of 18,730 bp in length. The gene arrangements include 14 protein-coding genes (PCGs), 2 ribosomal RNA genes, and 1 tRNA (tRNA-Met). The base composition is 30.18% A, 16.47% C, 19.35% G, and 33.99% T, with an A þ T content of 64.18%. With regard to the phylogenetic analysis, members of genus Sinularia were clustered in different clades.
Neon flying squid Ommastrephes bartramii and jumbo flying squid Dosidicus gigas are two important commercial ommastrephid species in the Pacific Ocean. As short-lived marine species, squids are highly susceptible to changes in climate and marine environments. According to samples collected from the northwest and southeast Pacific Ocean in different years, we explored the growth characteristics of these two squids in terms of their mantle length (ML) distribution and the relationship between mantle length and body weight (LWR), also considering the relative condition factors (Kn), and explored the effects of the El Niño and Southern Oscillation (ENSO) on their growth. The results showed that the ML for O. bartramii and D. gigas had significant differences among different years and different sexes (p < 0.01), and the size of females was larger than that of males. LWR showed that both squids demonstrated a positive allometric growth pattern (b > 3), and parameters a and b were influenced by year and sex. Furthermore, there were significant differences in Kn in both squids for different years and different sexes (p < 0.01), and their interannual fluctuations were quite significant. In conclusion, the alterations in the marine environment caused by climate change had a significant impact on the growth of O. bartramii and D. gigas in this study. ENSO events had opposite effects on the growth of both squid species.
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