The deep-sea is considered as the most extensive ecosystem on the Earth.It is meaningful for elucidating the life origins by exploring the origin and adaptive genetic mechanisms of the large deepsea organisms.Caridean shrimps have colonized and successfully adapted to deep-sea environments.They provide an ideal model to analyze the origin and adaptive evolution of modern deep-sea fauna.Here,we conducted the phylogenetic analyses of mitocho ndrial genomes(mitogenomes)from carideans,including 11 newly sequences reported in this investigation to explore the habitat origins,divergence times,and adaptive evolution of deep-sea(seamounts and hydrothermal vents)caridean shrimps.The results showed that the species of deep-sea Caridea formed a monophyletic group.Phylogenetic analysis supported that the deepsea caridean shrimps may originated from shallow sea.The hydrothermal vents alvinocaridid shrimps and Lebbeus shinkaiae from Thoridae underwent a second range expansion from seamounts to vent ecosystems.Estimates of divergence time showed that the caridean shrimps invaded into deep-sea at 147.75 Ma.The divergence of most of the modern seamount and hydrothermal vent species are in the late Cretaceous/early Tertiary.This may associate with the geological events of the Western Pacific,the climate change,and the global deep-water anoxic/dysoxic events during this period.Twenty-two potentially important adaptive residues were detected in the deep-sea shrimp lineage,which were located in atp6,atp8,cox1,cox3,cytb,nad2,nad4 l,and nad5.This investigation adds our understanding of the evolutionary history of deep-sea caridean shrimps,and provides insights into the mitochondrial genetic basis of deep-sea adaptation in this group.
The mitochondrial genome(mitogenome)analysis is a significant tool for investigating the evolutionary history of metazoan animals.The family Pandalidae is a diverse caridean group containing mainly deep-sea species.Until May 302019,only two complete mitogenomes are available in GenBank.Here we present the complete mitogenome sequences of two deep-sea pandalid shrimps,Heterocarpus ensifer and Bitias brevis through Illumina sequencing.The mitochondrial genomes were determined to be 15939 bp and 15891 bp long,and both consist of 13 protein-coding genes(PCGs),23 transfer-RNA genes(tRNAs),two ribosomal-RNA genes(rRNAs),and one control region.The nucleotide composition is biased toward adenine and thymine.Overall,the gene contents and arrangements are consistent with the pancrustacean ground pattern.The alignment of the control regions of four pandalids reveals a conserved sequence block(CSB)(104 bp in length,average GC%=29.47%and 69.23%similarity).A phylogenetic analysis based on 51 Caridea complete mitogenomes revealed that the deep-sea pandalid shrimps are situated an intermediate lineage,with a tendency to originated from those living in shallow sea area.
Four species of caridean shrimps collected from the East China Sea and South China Sea represent new records for the Chinese waters： Lysmata kempi Chace, 1997; Lysmata lipkei Okuno and Fiedler, 2010; Chlorocurtisjactans （Nobili, 1904） and Rhynchocinetes conspiciocellus Okuno and Takeda, 1992. The diagnostic characters and illustrations of these four species are presented, with remarks on their taxonomy. The identification keys of these species from Chinese waters are provided.
The monotypic genus Phycocaris Kemp, 1916, which was established based on material from the Indian Ocean and previously only known from the type localities, Australia and Japan, is now newly recorded from the South China Sea. A detailed description of Phycocaris simulans Kemp, 1916 based on the specimen collected from Hainan Island is presented. Specific features and the differences between the Indian Ocean and the present material are described.
A new genus of the deep-sea pontoniine shrimps,Bathymenes gen. nov.,is established for the 'Periclimenes alcocki species group' of the genus Periclimenes Costa,1844. The new genus is distinguished from other genera of the Pontoniinae by a combination of characters: the posteriormost dorsal rostral tooth remote from other teeth,situated in the epigastric position,cornea usually reduced,the propodus of second pereiopods covered with fine granules,the dactylus of the major second chela being generally flanged,the ambulatory pereiopods with the dactyli being biunguiculate and telson with more than two pairs of dorsolateral spines. The genus is mainly distributed in the tropical to warm-temperate Indo-West Pacific waters at depths greater than 200 m. Fifteen species previously recognized as belonging to the 'P.a lcocki species group' are now placed in Bathymenes gen. nov. A key for their identification and a checklist of congeneric species are provided.
The genus Synalpheus （Decapoda： Alpheidae） from China seas is reviewed. Thirty one species belonging to this genus are described and illustrated in the present paper, including 4 new species and 6 newly recorded species from the China seas as following： S. brevrostrus sp. nov., S. jinqingensis sp. nov., S. liui sp. nov., S. tonkinensis sp. nov., S. biunguiculatus （Stimpson, 1860）, S. gracilirostris de Man, 1910, S. iphinoe de Man, 1909, S. lophodactylus Coutiere, 1908, S. modestus de Man, 1909 and S. mortenseni Banners, 1985. A key to 31 species of the genus Synalpheus from China seas is provided.
This paper reports a new record of Alpheus tenuicarpus de Man, 1908 that belongs to the Brevirostris group of Alpheus from Chinese seas. The species is re-described and includes morphological characters not in the original description. A key species are also provided. to species of the group is provided. Remarks on similar
A new species from the caridean family Hippolytidae,Eualus heterodactylus sp.nov.is described and illustrated based on the specimens collected from Chinese coast of the Yellow Sea.The new species is a part of an informal species group characterized by the possession of epipods on the anterior three pairs of pereopods,and is distinguished from other species of this group by the dactyli of the third to fifth pereopods possessing distinctly stair-like flexor margins in males.
