Table 1.

Checklist of the species currently identified to genus or species levels collected from deep-sea habitats of Haima cold seeps, Ganquan Plateau and a mud volcano field in May of 2018

Phylum	Class	Order	Family	Species	Location and habitatb	Figure	Remarks
PORIFERA	Hexactinellida	Lyssacinosida	Rossellidae	Caulophacus sp.	GP1	4a	Sessile living on rocks
		Sceptrulophora	Euretidae	Pleurochorium sp.	GP1	4b	Sessile living on rocks
				Chonelasma sp.	GP2	4c	Sessile living on rocks
CNIDARIA	Anthozoa	Scleractinia	Dendrophylliidae	Enallopsammia rostrata (Pourtalès, 1878)	GP1	4d	Sessile living on rocks
		Alcyonacea	Chrysogorgiidae	Rhodaniridogorgia sp.	MV	3a	Sessile living on rocks
				Psedochrysogorgia sp.	GP2		Commensal with Euryalid ophiuroid
		Actiniaria	Actinernidae	Actinernus sp.	HM	4e	Adherent to dead shells, especially abundant in the rim area of mussel beds
ANNELIDA	Polychaeta	Phyllodocida	Polynoidae	Branchipolynoe pettiboneae Miura & Hashimoto, 1991	HM	4f	Commensal, living within shells of mussels
			Glyceridae	Glycera sp.	GP2		Found in crevice of a Pheronematidae sponge
		Sabellida	Siboglinidae	Paraescarpia echinospica Southward et al., 2002	GP1, HM	3d, 4g	Usually clusters on edges of authigenic carbonate rocks and occasionally forms small assemblages on mussel bed
MOLLUSCA	Polyplacophora	Lepidopleurida	Leptochitonidae	Leptochiton tenuidontus Saito & Okutani, 1990	HM	5a	Among mussles and ophiactids in mussel bed of Haima cold seeps
	Bivalvia	Nuculanida	Malletiidae	Malletia sp.	HM	5b	Within mussel bed of cold seeps
		Solemyida	Solemyidae	Solemya sp.	HM	5c	Within mussel bed of cold seeps
		Mytilida	Mytilidae	Gigantidas haimaensis Xu, Feng, Tao & Qiu, 2019	HM	5d	This species is a chemosynthetic-special mussel, and is one of the most dominant species in the mussel beds of Haima cold seeps
		Pectinida	Propeamussiidae	Propeamussium sp.	MV, HM		Identified based on a small colorless specimen associated with dead sponge in mud volcano field. Plenty of Propeamussium scallops were also observed free-living upon mud in rim area of mussel beds
		Venerida	Vesicomyidae	Calyptogena marissinica Chen, Okutani, Liang & Qiu, 2018	HM	5e	Very common in mussel-bed assemblages
		Lucinida	Lucinidae	Lucinoma sp.		5f	Within mussel bed of cold seeps
	Gastropoda	Patellogastropodaa	Pectinodontidae	Bathyacmaea lactea Zhang et al., 2016	HM		Small in size and predominant in abundance in mussel-bed assemblages
		Trochida	Calliostomatidae	Tristichotrochus ikukoae (Sakurai, 1994)	GP1	5g	Identified based on a small specimen associated with a Hexasterophora sponge
			Margaritidae	Margarites sp.	HM		Within mussel bed of cold seeps
		Caenogastropodaa	Provannidae	Provanna glabra Okutani, Tsuchida & Fujikura, 1992	HM	5h	Within mussel bed of cold seeps
		Neogastropoda	Raphitomidae	Phymorhynchus buccinoides Okutani, Fujikura & Sasaki, 1993	HM		Within mussel bed of cold seeps
			Buccinidae	Plicifusus sp.	HM	3e	Outside of the mussel bed. The species, based on a large specimen (> 9 cm in length), was observed creeping on muddy seafloor in rim of a mussel bed
			Muricidae	Scabrotrophon scitulus (Dall, 1891)	HM	5i	Within mussel bed of cold seeps
ARTHROPODA	Hexanauplia	Lepadiformes	Poecilasmatidae	Glyptelasma gigas (Annandale, 1916)	MV	6a	Adherent to Isididae coral
				Poecilasma litum Pilsbry, 1907	MV	6b	Adherent to carapace of Metanephrops neptunus (Bruce, 1965)
				Poecilasma obliqua Hoek, 1907	MV	6c	Adherent to the 3rd maxilliped of Metanephrops neptunus
	Malacostraca	Amphipoda	Eurytheneidae	Eurythenes maldoror d'Udekem d'Acoz & Havermans, 2015	HM	6d	Captured by trapping cage deployed on the seafloor between two seep sites. The cage was put during dive of the day ahead, and collected during the dive of the next day by the corresponding author (Xinzheng Li)
		Isopoda	Cirolanidae	Bathynomus jamesi Kou, Chen & Li, 2017	HM	6e	Captured together with Eurythenes maldoror using trapping cage by corresponding author (Xinzheng Li)
		Decapoda	Alvinocarididae	Alvinocaris longirostris Kikuchi & Ohta, 1995	HM	3f, 6f	One of the dominant crustaceans in West Pacific chemosynthetic ecosystems. This species was observed in swarms within seepage mussel beds
			Nematocarcinidae	Nematocarcinus sp.	HM	3g	Identified based on an uncollected individual; inhabiting on muddy seafloor in rim of the mussel bed
			Palaemonidae	Palaemonella sp.	GP2		Observed in high abundance suspending upon the seafloor
			Nephropidae	Metanephrops neptunus (Bruce, 1965)	MV	3h	Common in mud volcano area, inhabiting under stones or in gas holes. Stalked barnacles were recovered from a specimen of Metanephrops neptunus
			Lithodidae	Paralomis sp.	HM	3i	Identified based on a specimen captured using the submersible’s mechanic arm; in situ observed crawling in the rim area of mussel bed
			Chirostylidae	Uroptychus setosidigitalis Baba, 1977	GP2	6g	Associated with Psedochrysogorgia corals. The specimen, with the chelipeds lost, was temporarily assigned to U. setosidigitalis, although its rostrum was relatively longer than that of the holotype
			Munidopsidae	Munidopsis lauensis Baba & Saint Laurent, 1992	HM	6h	Typical species in chemosynthetic habitats, widely distributed in West-Pacific chemosynthetic environment
				Munidopsis pilosa Henderson, 1885	HM	6i	Widely distributed in Indo-West Pacific. In the deep waters of Taiwan Island, it was found associated with sunken wood (Baba et al. 2009). This is the first discovery of the species from cold-seep environment
				Munidopsis trifida Henderson, 1885	GP1		Widely distributed across Pacific and Indian Oceans. The specimen collected from Ganquan Plateau has been parasitized by an isopod species in gill chamber
			Inachidae	Cyrtomaia sp.	GP2, MV	3j	The specimen in northeastern slope of Ganquan Plateau was captured upon a Chonelasma sponge. Another small specimen was observed inhabiting on a reefs in mud volcano area
			Geryonidae	Chaceon sp.	MV	3k	Common in chemosynthetic environment, which is seen as an opportunist in this kind of habitat. The species was observed crawling on sea bottom in the mud volcano field
ECHINODERMATA	Ophiuroidea	Amphilepidida	Ophiothamnidae	Histampica sp.	HM		Inhabiting in mussel bed with other ophiuroids species

^aSubclass

^bLocation and habitat: GP1: slope of southwestern Ganquan Plateau, depth 1300–1412 m, with the substrates basically boulders and flat rocks, and the only exception of a cold-seep site where the tubeworm P. echinospica were collected, GP2: rocky slope of northeastern Ganquan Plateau, depth 586–910 m, with the substrate flat rocks, HM: within mussels bed of Haima cold-seep sites, depth 1380–1390 m, with the substrate muddy seafloor, MV: mud volcano area, depth 500–810 m, with the substrates flat rocks on the otherwise muddy seafloor