Based on polychaete specimens collected from coastal areas of China in 1959, a new species of the family Orbiniidae, Leodamas sinensis sp. nov. is described in the present paper. The new species can be distinguished from its cogeners by the combination of following characters: branchiae present from chaetiger 5; each thoracic neuropodial postchaetal lobe possessing broad tori, with a digital to triangular-shaped papilla at its midlength; 4 or 5 vertical rows of uncini and one posterior row of accompany capillaries in thoracic neuropodia; acicula present in both abdominal notopodia and neuropodia, slightly or distinctly projecting. A key to all known species of the genus is provided.

The male of Candacia varicans Giesbrecht, 1892 from the South China Sea was recorded and described. In general, the male of C. varicans is morphologically similar to those of C. armata and C. curta. However, it is distinguished with them by below several morphological characters: (1) posterolateral corners of the fifth thoracic segment prominently sharp and symmetrical; (2) right side of posterior edge of genital segment with a small backward protuberance; and (3) the dorsal surface of the third segment of the fifth pereiopod with a squama-shaped protuberance.

A new record of the ampharetid genus Auchenoplax, A. worsfoldi Jirkov and Leontovich, 2013, is reported and described from the East China Sea. The specimens agree well with the original description of Auchenoplax worsfoldi with two pairs of branchiae, two thoracic uncinigers with enlarged neuropodia and 12 abdominal uncinigerous segments. The present specimens have long and filiform branchiae extending to thoracic chaetiger 9, which was not included in the original description. This is the first record of this species in Chinese waters.

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.

In order to investigate the tintinnid diversity, vertical distribution and latitudinal variation in the tropical West Pacific Ocean, water samples of different depths from surface to 200 m were collected along four transects. Totally 124 tintinnid species in 39 genera were detected. Most species preferred to live in the surface and subsurface waters. High tintinnid species richness, abundance and diversity index mainly occurred at depths slight shallower than the layer of deep chlorophyll maximum. Species richness, abundance and Shannon’s diversity index were significant positive correlation with temperature and chlorophyll a in vivo fluorescence, but significant negative correlation with salinity and depth. The correlations between most dominant species and environmental factors were not significant. Tintinnid diversity was extremely high in this area, species richness ranged from 25 to 52 at each station, Shannon’s diversity indexes were higher than 3 at most sampling positions from surface to 75 m. Proportions of redundant species were high, accounted for 87.90% of species pool and 60.38% of total abundance, indicating high capacity to response to changes in resource composition and predation pressures of tintinnid communities in the tropical West Pacific Ocean.

The littoral paranthurid isopod crustacean Paranthura nigropunctata (Lucas, 1846) is recorded for the first time from the littoral of El Jadida located on the Atlantic northwest coast of Morocco. Specimens were obtained from the invasive brown seaweed Sargassum muticum and the natives Bifurcaria bifurcata and Cystoseira tamariscifolia in January 2015. This new record further confirms a significant southward distribution of P. nigropunctata and contributes to the knowledge of the biogeography of this isopod. Heretofore, the species was only known from the western and eastern Mediterranean and some Atlantic coasts. The present finding is the first of the species from Moroccan Atlantic shores, and suggests that the species may also be present in other coastal localities from Morocco and Africa. Some data on morphology, ecology and spatial distribution of the species are provided.

Research and protection of biodiversity is generally started with species recognizing guided by achievement of cataloguing and illustration obtained through in situ investigation data accumulation and literature learning. Facing the shortage of taxonomist, it is getting harder to maintain important specimen collections and handle loans. The West Pacific Ocean has been operating as a center of the origin of global marine biodiversity result of the richest species diversity of marine taxa found in these waters. The present work is a compilation and summary of systematics, species diversity and new taxa of mesozooplankton major group known in West Pacific Ocean and its marginal seas (0°–45°N, 105°–152°E) according to 6 203 mesozooplankton samples acquired from 701 stations during 1965 and 2008. A total of 2 657 species belonging to 686 genera and 206 families of 10 mesozooplankton groups have been found through taxonomic identification and document consulting. In details, 697 species from 251 genera of 99 families belong to the Medusozoa, 59 species from 22 genera of 12 families to the Ctenophora, 85 species from 36 genera of 14 families to the pelagic Mollusca (Pteropoda and Heteropoda), 416 species from 91 genera of 8 families to the Ostracoda, 908 species from 156 genera of 51 families to the Copepoda, 202 species from 60 genera of 4 families to the Mysidacea, 56 species from 8 genera of 2 families to the Euphausiacea, 105 species from 23 genera of 8 families to the Decapoda, 48 species from 13 genera of 5 families to the Chaetognatha and 81 species from 26 genera of 5 families to the Tunicata. The dominant species of each group are enumerated. Moreover, 2 new species of Medusozoa, Tubulariidae, Ectopleura, 1 new species of Medusozoa, Protiaridae, Halitiarella, 1 new genus and 1 new species of Medusozoa, Corymorphidae are established. An amount of 806 species are expanded with an increase of 43.5% on the basis of 1 852 species recorded before 2008, including 1.4% increase from tropical sea around equator, 4.0% from the frigid water in high latitude region, and 3.0% of bathypelagic-associated waters. The authors also summarized future prospects into five major areas in marine mesozooplankton research in China. Such information of qualitative phyletic classification could be of high relevance to studies on biodiversity and biogeography of marine mesozooplankton, especially for monographs contributed to make an overall and systematic conclusion on the species of marine life in China after 2008.

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.

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.

Two chiton specimens were collected from sedimentary habitat by China’s manned Jiaolong submersible diving to a depth of 6 754 m in the north of the Yap Trench. This is a new locality record for chiton. Both morphological and molecular data support that the two specimens are the same species belonging to the genus Leptochiton. Morphologically, this species strongly resembles L. vanbellei and L. deforgesi. Phylogenetically, it has a close evolutionary relationship with L. vanbellei, L. deforgesi and L. boucheti. This is the third deepest record for deep-sea chitons so far.