Project description:Trachypenaeus curvirostris is a common and important shrimp species in the shallow waters of Indo-West Pacific. In this study, the mitochondrial genome of T. curvirostris was determined for the first time using next-generation sequencing; the overall base components of mitogenome consisting of 15968 bp was 35.16% (5614 bp) for A, 33.51% (5351 bp) for T, 11.54% (1842 bp) for G, 19.80% (3161 bp) for C, and its GC content was 31.34%. The mitochondrial circular genome was composed of 13 protein-coding genes, 22 transfer RNAs, 1 D-loop and 2 ribosomal RNAs. Polygenetic analysis showed that the T. curvirostris was more closed to Parapenaeopsis hardwickii.
Project description:Pond-dwelling cyclic parthenogens are often proposed to be highly vagile. However, the Holarctic biogeography of parthenogens has been hampered by very limited sampling in the eastern Palearctic. Here we examine the geographic boundaries, diversity, and connectivity across the Palearctic for the Daphnia curvirostris complex (Cladocera: Daphniidae). Nuclear (HSP90) and mitochondrial (ND2) sequence data supported the existence of five main clades (most of which corresponded to presumptive species) with one eastern Palearctic clade being novel to this study (the average mitochondrial genetic divergence from known species was 19.2%). D. curvirostris s.s. was geographically widespread in the Palearctic, with a population genetic signature consistent with postglacial expansion. The Eastern Palearctic had local nine endemic species and/or subclades (other Holarctic regions lacked more than one endemic subclade). Even though several endemic species appeared to have survived Pleistocene glaciation in the eastern Palearctic, much of the Palearctic has been recolonized by D. curvirostris s.str. from a Western Palearctic refugium. A disjunct population in Mexico also shared its haplotypes with D. curvirostris s.str., consistent with a recent introduction. The only apparently endemic North American lineage was detected in a thermally disturbed pond system in northwestern Alaska. Our results for pond-dwelling cyclic parthenogens further support the hypothesis that the Eastern Palearctic is a diversity hotspot for freshwater invertebrates.
Project description:In order to improve the size selectivity and exploitation pattern for cocktail shrimp (Trachypenaeus curvirostris) in shrimp trawl fishery of the South China Sea (SCS), selective properties of four codends were tested and compared. These experimental codends involved two mesh sizes, 30 and 35 mm, and two mesh shapes, diamond-mesh (T0) and diamond-mesh turned by 90 degree (T90), respectively. Our results demonstrated that increasing the mesh sizes in T0 codends or/and applying T90 codends would improve the selective properties for cocktail shrimp in the SCS. By comparing selectivity parameters, delta selectivity and exploitation pattern indicators, the T90 codend with 35-mm mesh size (T90_35) presented the best selective properties for cocktail shrimp in the studied areas. It will be a potential choice to substitute the currently legal codend in fisheries management to mitigate the bycatch of undersized cocktail shrimp in shrimp trawl fisheries of the SCS.
