New record of the feather star Palaeocomatella hiwia(Echinodermata:Crinoidea:Comatulida)from Zhenbei Seamount in South China Sea:new insights into the taxonomic position of Palaeocomatella

One specimen belonging to the family Comatellinae was collected from the Zhenbei Seamount(332.5–478.2 m)in the South China Sea in July 2022.Based on the morphological characters,the specimen was identified as Palaeocomatella hiwia McKnight,1977.It is first recorded from China Sea and redescribed in detail.This specimen differs from the original description from New Zealand for never showing syzygy at br4+5 or br5+6 on interior and br1+2 on exterior arms.However,it is much conform to the redescription to specimens from Indonesia,with only differences in position of the second syzygy and distalmost pinnule comb.Specimen is deposited in the Institute of Oceanology,Chinese Academy of Sciences.Phylogenetic analyses based on the mitochondrial c oxidase subunit I(COI)and 16S rRNA genes indicated that P.hiwia was nested within the tribe Phanogeniini and clustered with Aphanocomaster pulcher.Furthermore,P.hiwia showed same morphological features in terms of mouth placement,comb location,and number of comb teeth rows as other genera of Phanogeniini.Therefore,we suggest that the genus Palaeocomatella should be put in the tribe Phanogeniini.

Mitochondrial phylogenomics reveal the origin and adaptive evolution of the deep-sea caridean shrimps(Decapoda:Caridea)

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.