A brief morphometric study of the recent planktonic foraminifera in the eastern Indian Ocean was provided with the taxonomic key to species, synonyms, SEM microphotographs of shells and chamber arrays. By recent classification, currently 20 species representing 13 genera and 6 families (Canderinidae, Heterohelicoidae, Hedbergellidae, Higerigerinoidae, Globigerinoidae, and Globorotaloidae) identified from the planktonic material of the eastern Indian Ocean up to a depth of 200 m. Their distribution in water (0–200 m) also reports on the new range of expansion in the eastern Indian Ocean, with Dentigloborotalia anfracta, Hastigerina pelagica, Streptochilus globigerus, Globigerinella calida, Globigerinella adamsi, Orcadia reidelii, Tenuitella parkerae, Tenuitella compressa, reported for the first time in this study area. In general, only around 50 planktonic species are valid worldwide, more specifically the species, e.g., H. pelagica, G. calida, G. adamsi, S. globigerus, O. riedeli, T. parkerae, T. compressa, which occur in the eastern Indian Ocean to fill the the paucity of the recent regional taxonomic literature and the problematic identification from the eastern Indian Ocean. This work aims to bridge this gap and help scientists, managers, educators and students to identify plankton foraminifers by using species notes and images.

Foraminiferal oozes were sampled from the tropical West Pacific seamount and seabed of deep sea, by a remotely operated vehicle (ROV) in December 2014 and March 2016. Using standard morphological method, four Miliolinella species, including Miliolinella obesa, M. circularis, M. suborbicularis and M. subrotunda were described. Among the four species, M. obesa is a new species. It is a large member (about 500 μm in length) of the genus. This species is characterized by having a very stout and transverse broadly circular outline, and its body width is greater than the body length. In addition, its chamber demarcations are obscure from the exterior appearance. Three chambers are unclearly visible on one side and two chambers are visible on the opposite. Finally, we provided very detailed taxonomic microphotographs and the ecological distribution information for each species.

Planktonic ostracods are small crustaceans abundant in marine ecosystem worldwide as appreciable part of marine zooplankton. Family Halocyprididae is a large group of halocyprid ostracods, and the tribe Conchoeciini has contained 21 genera previously. We described a further genus with a species Polyconchoecia commixtus gen. et sp. nov. from the middle of South China Sea in this study. The new species can be distinguished from related genera and species in having a unique combination of these characteristics: a lateral gland placed over right asymmetric gland and open near posterior margin; dense edge glands placed along ventral margin of carapace in line; shape of frontal organ; e-seta of first antenna is bare; endopod of second antenna has one small oval hump with central concave on mid-ventral margin, instead of processus mamillaris, exopod 1 has a small disto-dorsal spine, exopod 1 and 2 are fused, exopod 3 and 4 are bare; endopod 1 of mandible has one long ventral seta, endopod 2 has one ventral seta; maxillary endopod 1 has two basal setae; endopod 1 of fifth limb has only one ventral seta; endopod 1 of sixth limb and endopod 2 have no ventral seta. The definite distinctions in locations of major glands are the key characteristics of the new genus.

Epipont peritrich ciliates are one of the most sessilie protists that attached to the substrate of zooplankton communities especially copepods and crustaceans. Peritrich ciliates can be solitary or colonial form found from the coastal zones and embayment around the world. Present research report is the first snapshot study of the peritrich ciliates and the horizontal distribution in open waters from surface to 200 m depth in the eastern Indian Ocean. Recently, five peritrich ciliates, e.g., Vorticella oceanica, Zoothamnium alternans, Z. alrasheidi, Z. pelagicum, and Z. marinum were collected from plankton net tow samples during the cruise from April 10 to May 13, 2014. The characteristics of the peritrich ciliate were determined according to the shape of the zooids, the ciliary structure and the stalks. The morphometric shape, sizes and characters also explained by examination under light/scanning electron microscopy. Vorticella oceanica and Z. pelagicum showed their association with host such as diatom (i.e, Chaetoceros coarctatus) and copepod (Oithona brevicornis) including some individuals around the dinoflagellate species (Ceraitum tripose). The distribution of these sessilid ciliates was dominated by the V. oceanica, Z. pelagicum and Z. marinum at the southeast zone while the large colonies of Z. alrasheidi observed at the Bay of Bengal. This distribution can be influenced by substrate availability like diatom (Ch. coarctatus) and copepods (O. brevicornis).

The living morphology and infraciliature of six spirotrichous ciliates collected from the coastal South China Sea were investigated using live observation and protargol impregnation. These are Euplotes woodruffi Gaw, 1939, Hemigastrostyla enigmatica (Dragesco and Dragesco-Kernéis, 1986) Song and Wilbert, 1997, Neourostylopsis flavicana (Wang et al., 2011) Chen et al., 2013, Protogastrostyla pulchra (Perejaslawzewa, 1886) Gong et al., 2007, Pseudoamphisiella alveolata (Kahl, 1932) Song and Warren, 2000, and Pseudokahliella marina (Foissner et al., 1982) Berger et al., 1985. Among these, Protogastrostyla pulchra, Pseudoamphisiella alveolata and Pseudokahliella marina are reported from the South China Sea for the first time, which manifest obvious differences apart from other Chinese populations. As new contribution, the detailed description of isolates from mangrove habitat of E. woodruffi and H. enigmatica, and aquaculture pond isolate of N. flavicana, are present.

Four species of Trichodina parasitizing the gills of cultured molluscs and fishes in China are described: Trichodina pectenis Stein, 1974 from the scallop Mizuhopecten yessoensis; Trichodina jadranica Raabe, 1958 from the fishes Mugil cephalus and Anguilla bicolor bicolor; Trichodina acuta Lom, 1961 and Trichodina rostrata Kulemina, 1968 from the fish Acrossocheilus fasciatus. The description of T. pectenis presented here first includes both live characters and morphometric data obtained from specimens impregnated using the wet silver nitrate and protargol methods. The other species were revealed by the dry silver nitrate method. Intensities of infestation and comparisons with related species and populations are provided for each of the four.

This study reviews all genera and species belonging to the family Bougainvilliidae from the South China Sea. The Nubiella atentaculata Xu and Huang, 2004 formerly included in the genus Nubiella, now is transferred to a new genus Paranubiella and included in the Bougainvilliidae as Paranubiella atentaculata (Xu and Huang, 2004) n. comb.. Two new species, Paranubiella nanhaiensis Xu, Huang and Guo, sp. nov. and Nubiella apapillaris Xu, Huang and Guo, sp. nov. from the South China Sea are described and illustrated in the present paper. In addition, the key to known genera of family Bougainvilliidae and species of genus Nubiella are described. Other data are briefly summarized to the list of species presented on the family Bougainvilliidae in the South China Sea. The type species were deposited at the Third Institute of Oceanography, State Oceanic Administration.

This study reviews all species belonging to the families Laodiceidae, Lovenellidae, Malagazziidae, and Mitrocomidae in the South China Sea. Two new species, Eucheilota carinata sp. nov. and Halopsis nanhaiensis sp. nov., are described and illustrated. One genus, Staurostoma, and two species, Staurostoma sp. and Octophialucium aphrodite (Bigelow, 1928), are first recorded in China seas. The key to all medusa genera and species of Lovenellidae and Malagazziidae are presented. Other data are briefly summarized to the list and distribution of species presented on the family Laodiceidae, Lovenellidae, Malagazziidae and Mitrocomidae in the South China Sea. The type specimens are deposited in the Third Institute of Oceanography, State Oceanic Administration, China.

This study describes and illustrates four new species Laticanna nanhaiensis Xu, Huang and Wang, gen. nov. and sp. nov., Protiaropsis gemmifera Xu, Huang and Du, sp. nov., Merga nanhaiensis Xu, Huang and Guo, sp. nov. and Rhabdoon apiciloculus Xu, Huang and Du, sp. nov. based on specimens from the south-central South China Sea. Additionally, keys to known genera of family Bythotiaridae and species of genera Protiaropsis, Merga, and Rhabdoon are described. All type specimens are deposited in the South China Sea Fisheries Research Institute, Chinese Academy of Fishery Science.

Box jellyfish Chiropsoides buitendijki from the coastal zone along the Andaman Sea, southwestern Thailand are characterized by a box-shaped body with unilateral branched tentacles and lack of interradial furrows. Tentacular banding was first reported in the present study with 1-3-2-3-2-3-2-3-1 patterns (1-major band, 2-thicker minor band and 3-thinner minor band). The DNA sequences of 18 S ribosomal RNA genes indicated that the specimen examined were genetically similar to C. buitendijki that was previously identified from the Nam Bor Bay, Phuket, Thailand, and distinct to the other known taxa in the order Chirodropida. In addition, a significant genetic divergence based on 16S mitochondrial gene was observed within the C. buitendijki samples. This indicates a population genetic differentiation but needs further confirmation.