Antarctic Fish Diversity Based On DNA Barcoding And EDNA Metabarcoding

The Southern Ocean is the coldest ocean in the world,and it is the only ocean on Earth that is circular and not divided by a continent.The Southern Ocean has extreme oceanic and climatic conditions.Antarctic fish have evolved over millions of years to adapt to the extreme conditions of the Antarctic.The Antarctic is currently experiencing complex climate changes,such as rising sea temperatures,melting sea ice,and desalination,which is a great challenge for the oceanic and narrow-temperature Antarctic fish.As the most abundant vertebrate group,fish is the key component of the normal functioning of the marine ecosystem,playing a series of basic ecological functions and an important role in indicating the carrying capacity of the ecosystem.Antarctic fish biodiversity research is the scientific basis for Antarctic biological conservation and management.However,the unique fish fauna and the scarcity of reference materials make it difficult to identify Antarctic fish by traditional morphology,and DNA barcoding can provide accurate and rapid identification of fish by molecular techniques.Due to the remote location and extreme climate of Antarctica,the traditional trawl survey has many limitations in Antarctica,and the environmental DNA technology can extract DNA from water samples to detect biological activities.In this paper,we useDNA barcoding and environmental DNA technology in combination with traditional bottom trawling to achieve a comprehensive survey of Antarctic fish diversity,and the main conclusions of this paper are as follows.1.The accuracy of traditional morphology and COI-based molecular taxonomy in the classification of Antarctic fishes was compared by different ways of taxonomic identification of fishes caught in the Amundsen Sea during the 36^th Chinese National Antarctic Research Expedition,with the following results:traditional morphology identified 69 fishes as 12 morphological species,ASAP supported the classification of the captured fishes into 11 taxonomic units,and BPP supported the classification of the 69 fishes into 13 taxonomic units.Combining the barcode gaps and the majority-rule consensus tree,the results showed that the 69 Antarctic fishes belonged to 12genera,6 families and 2 orders,with a total of 13 species.The topology of the majority-rule consensus tree based on COI verified that the Bathydraconidae were paraphyletic,which is consistent with previous studies.This experiment confirmed that DNA barcoding can play an accurate identification role in the study of Antarctic fish diversity.After repeated confirmation,Ophthalmolycus amberensis,Chaenodraco wilsoni,Dacodraco hunteri,Akarotaxis nudiceps,Artedidraco lonnbergi and Vomeridens infuscipinnis are likely to be caught for the first time in the Amundsen Sea.This is also the first description of the molecular taxonomy of fishes in the Amundsen Sea region,and this study provides important scientific information for understanding the fish fauna of the Amundsen Sea.2.During the 37^th Chinese National Antarctic Research Expedition,bottom trawling and environmental DNA water sampling were conducted in the Bellingshausen Sea,the Weddell Sea,the Cosmonauts Sea and the Prydz Bay respectively.The trawl caught 27 species of Antarctic fish belonging to 7 orders,13families and 24 genera.eDNA metabarcoding was detected in 26 species of fish belonging to 8 orders,13 families and 24 genera.12 species of fish were detected by both trawl and eDNA metabarcoding,mainly from the family level of classification,such as Myctophidae,Stomiidae,Artedidraconidae,Channichthyidae,Zoarcidae,Nototheniidae,Bathydracinidae,Macrouridae,Liparidae.The main species detected by both methods were similar.The endemic species detected by eDNA were mainly pelagic fishes and small individual fishes,and the endemic species caught by trawl were benthic deep-sea fishes.The species detected by eDNA covered 44.45%of the species caught in the trawl,demonstrating that eDNA can be widely used in Antarctic fish diversity research.By analyzing the surface and bottom fish diversity in the four sea areas detected by eDNA technology,in terms of Alpha diversity:the diversity of bottom species in the Bellingshausen Sea is higher than that in the surface layer;the surface diversity of fish diversity in the Weddell Sea,the Cosmonauts Sea and the Prydz Bay are greater than that in the bottom layer.In terms of Beta diversity,there were some differences between the surface fish community and the bottom fish community in the Weddell Sea,the Bellingshausen Sea.The surface fish community and the bottom fish community in the Cosmonauts Sea and the Prydz Bay were more similar in composition.With the relatively similar species detected in the four sea areas,the main reasons for this diversity distribution may be the following:the retention of eDNA in different water layers due to the vertical movement of Antarctic fishes;the influx of bottom eDNA into the surface layer due to the transport and mixing of eDNA in the water column by the complex currents in the Southern Ocean.This study demonstrates the feasibility and applicability of eDNA in the study of Antarctic fish diversity.The combined application of bottom trawling and eDNA techniques helps us to gain a more comprehensive understanding of Antarctic fish diversity and its distribution patterns,which is of great significance for resource management,scientific research and reserve planning of Antarctic marine fishes.