Jun Nishikawa

Tokai University, Japan · School of Marine Science and Technology

The Tōhoku earthquake and tsunami of March 11, 2011, resulted in unprecedented radioactivity releases from the Fukushima Dai-ichi nuclear power plants to the Northwest Pacific Ocean. Results are presented here from an international study of radionuclide contaminants in surface and subsurface waters, as well as in zooplankton and fish, off Japan in...

Distribution and biomass of salps and Antarctic krill (Euphausia superba) were investigated near the South Shetland Islands during austral summer 1990–1991. Salp biomass ranged between 0 and 556 mgCm–3 and was greatest at a station in the Bransfield Strait in late December 1990. Salp biomass was lower than that of E. superba. Two species of salps;...

We describe a new species of Crambionella , C. helmbiru , from central Java, Indonesia. The combination of the mean number of lappets per octant (14), presence of foliaceous appendages amongst frills on oral-arms, absence of tubercles on the velar lappets, proportion of terminal club length to oral-arm length (0.28), and the body colour distinguish...

Tissue shrinkage of gelatinous zooplankton in preservatives may lead to significant bias in length measurements of animals. We measured the body lengths of two gelatinous zooplankton, Thalia democratica and Dolioletta gegenbauri (Tunicata: Thaliacea) in 5% buffered formalin and seawater for up to 1053 days in order to evaluate the degree of shrinka...

The rhizostome jellyfishes, Rhopilema hispidum and Lobonemoides robustus, are two of the most abundant and commercially important species in Southeast Asia. However, information on genetic diversity and continuities among local populations remains totally unknown. We explored the genetic structure and population continuities of R. hispidum and L. r...

Seasonal occurrences of Calanus sinicus and Calanus jashnovi were investigated using monthly samples covering 0–200 or 0–1000 m in central Sagami Bay, Japan, from May 2002 to January 2004. While copepodite stages I–V (CI–CV) of C. sinicus appeared at 0–200 m throughout the year, significant fractions of the CVs occurred below 200 m during spring–au...

Background Gelatinous zooplankton in epipelagic environments often have highly transparent bodies to avoid detection by their visual predators and prey; however, the digestive systems are often exceptionally opaque even in these organisms. In a holoplanktonic gastropod, Pterotrachea coronata , the visceral nucleus is an opaque organ located at the...

Although marine cladocerans are known as coastal zooplankton, they sometimes appear in offshore waters in large numbers. In Suruga Bay, located in the center of Japan and opens to the Pacific Ocean, cladocerans occur abundantly in offshore waters during the spring and summer seasons. However, the mechanisms by which these offshore populations form...

The impacts of environmental changes and mangrove disturbance on the gelatinous zooplankton community structure were investigated monthly for one annual cycle at six stations in three estuaries in Matang, Malaysia. Tiram, Tinggi, and Sepetang estuaries were classified based on the Mangrove Quality Index (MQI) to represent the least (MQI 5 = excelle...

The fatty acid composition of sakura shrimp muscle was used to determine the origin and estimate the dietary habits of the shrimp. The major fatty acids in sakura shrimp muscle were C16:0, C18:1n-9, C20:5n-3, and C22:6n-3. The discrimination rate between sakura shrimp from Suruga Bay and Taiwan was 90%. Consequently, it is considered possible to di...

Seasonal occurrences of marine cladocerans in offshore Suruga Bay, Japan, were studied from 2014 to 2019. Zooplankton samples were collected monthly from a station (depth: ca. 1000 m) located in the offshore area of the bay. Cladocerans appeared each year from February to December, and disappeared in January. Their abundance in- creased drastically...

We report five episodic blooms of the pinkish-brown salp Pegea confoederata (Forskảl 1775) in Malaysian waters occurring between July 2017 and August 2019. On 28 July 2017, a swarm of P. confoederata consisting of solitaries and aggregates was detected at Pulau Kapas, Terengganu (N 05°12'56'', E 103°15'44''), close to its western shoreline. The sec...

Mastigias papua, known as the golden (or spotted) jellyfish, is an epipelagic jellyfish widely distributed in the warm waters of the West Pacific. This jellyfish has a brownish body, owing to zooxanthellae, and white spots. We measured the maximum force to pierce the umbrella, which averaged 94–144 mm in diameter, to evaluate the hardness of M. pap...

The edible jellyfish Acromitus hardenbergi Stiasny, 1934 is harvested throughout the year at the mouth of the Perak River, Malaysia. Although this species is an important fishery resource in the local area, limited biological studies have been carried out on it. The aim of the present study was to elucidate the life cycle of this unique brackish-wa...

Seasonal and vertical variations in photosynthetic–irradiance (P–E) parameters and primary production were examined in offshore Suruga Bay, where both the subtropical warm Kuroshio Water and eutrophic coastal water were influential. The maximum light-utilization coefficient, α*, did not show significant variation between the surface and subsurface...

Hydrozoan jellyfish of the genus Blackfordia currently consist of three described species: B. manhattensis, B. virginica and B. polytentaculata. These species are distinguished by combinations of the position and shape of the gonads, the number of marginal tentacles, and the presence or absence of black pigments on the bell rim. We discovered a spe...

The exumbrellar surfaces of six pelagic cnidarians from three classes were ultra-structurally compared to reveal their structural diversity in relation to their gelatinous, transparent bodies. We examined two hydrozoans (Diphyes chamissonis and Colobonema sericeum), a cubozoan (Chironex yamaguchii), and three scyphozoans (Atolla vanhöffeni, Aurelia...

Scyphozoans are currently causing great concern because of their blooms in the marine environment. During the field surveys in Cat Ba and Hon Me islands in 2019 and Thuy Trieu lagoon in June 2020, we found specimens of a rhizostome jellyfish that had not been previously recorded in Vietnam sea. These specimens had the following morphological charac...

In Thailand, two species of rhizostome jellyfish, Rhopilema hispidum and Lobonemoides robustus , are commercially harvested. The cnidomes, nematocyst size and toxicities were compared between these species. Rhopilema hispidum and L. robustus each had four types of nematocysts on their oral arms. For R. hispidum , these nematocyst types included two...

An array of nano-scale protrusions, called the nipple array, is found on the body surface of various invertebrates, and this structure is believed to decrease light reflectance and water wettability on the surface in the terrestrial environment. However, its potential functions have not been well studied in aquatic environments. Clavelina spp. are...

The stings of box jellyfishes can be fatal, so knowing the fauna of a certain area is important to save lives. Five described and two still-undescribed species of Cubozoa have been reported from Thailand: Chironex indrasaksajiae, Chironex sp., Chiropsella sp., Chiropsoides buitendijki, Copula sivickisi, Morbakka fenneri, and Tripedalia cystophora....

Gelatinous zooplankton can be extremely fragile, sometimes with over 95% of their mass comprised of water. Although some taxa can be sampled and observed in an aquarium, many taxa do not survive collection and can only be studied in situ. Many of these taxa are undescribed species, sometimes in new genera, families or even orders. Since holotypes o...

The relationship between zooplankton community structure and selected environmental conditions was investigated by simultaneous two-day consecutive sampling in the waters overlying coral and sand sites off Sibu Island and a seagrass site off Tinggi Island, Johor, Malaysia. A total of 129 taxa were identified, 60 non-copepod taxa and 69 copepod spec...

Background Invisibility in the water column is a crucial strategy for gelatinous zooplanktons in avoiding detection by visual predators, especially for animals distributed in the euphotic zone during the daytime; i.e., surface dwellers that do not undergo diel vertical migration. Salps, a member of the subphylum Tunicata (Urochordata), usually have...

Peniculus hokutoae n. sp. is described on the basis of an ovigerous adult female parasitizing the caudal fin of the myctophid fish Symbolophorus evermanni (Gilbert, 1905), collected from Suruga Bay, Japan. This is the first record of parasitism by this genus on mesopelagic myctophid fish. The new species is easily distinguished from other congeners...

Scyphozoans are very attractive as ornamental animals at public aquaria. Almost all European and American species are exhibited at world aquaria. However, few Southeast Asian scyphozoans are exhibited, although some of them are very beautiful species and deserve exhibition. We have been studying edible jellyfish biology in Southeast Asian countries...

Pegea confoederata is a salp with a pinkish-brown body. The color was retained in the mantle tissue, while the tunic was transparent. We examined the fine structures of the mantle tissue to clarify the cytological basis of the body coloration. Apical cytoplasmic bulges of the epidermal cells were associated with dense tunic fibers, suggesting an in...

The relationship between Zooplankton community structure and selected environmental conditions was investigated by simultaneous two-day consecutive sampling in the waters overlying Coral and sand sites off Sibu Island and a Seagrass site off Tinggi Island, Johor, Malaysia. A total of 129 taxa were identified, 60 non-copepod taxa and 69 copepod spec...

To elucidate the activity concentration and behavior of radiocaesium, we observed the spatial and vertical distributions of radiocaesium in sediment collected at 12 monitoring stations off the coast of Fukushima Prefecture in 2013–2015. In bulk surface-layer sediment (core depth: 0–3 cm), high ¹³⁴Cs activity concentrations were observed at stations...

We report for the swarm of salp Pegea sp. in the Terengganu waters of Peninsular Malaysia. On July 28th 2017, close to the shore at Pulau Kapas, Terengganu (5. °13'N, 103 °15'E), a swarm of the salp, solitaries and aggregates forms were noticed. The hand-collected salps from the tidal zones were kept alive for more than five hours, which was eviden...

Efficiency and effectiveness of collagen extraction process contribute to huge impacts to the quality, supply and cost of the collagen produced. Jellyfish is a potential sustainable source of collagen where their applications are not limited by religious constraints and threats of transmittable diseases. The present study compared the extraction yi...

This paper focuses on how a community of researchers under the COMET (CO-ordination and iMplementation of a pan European projecT for radioecology) project has improved the capacity of marine radioecology to understand at the process level the behaviour of radionuclides in the marine environment, uptake by organisms and the resulting doses after the...

The 2011 release of Fukushima-derived radionuclides into the Pacific Ocean made migratory sharks, teleosts, and marine mammals a source of speculation and anxiety regarding radiocesium (134+137Cs) contamination, despite a lack of actual radiocesium measurements for these taxa. We measured radiocesium in a diverse suite of large predators from the N...

Online biogeographic databases are increasingly being used as data sources for scientific papers and reports, for example, to characterize global patterns and predictors of marine biodiversity and to identify areas of ecological significance in the open oceans and deep seas. However, the utility of such databases is entirely dependent on the qualit...

Background Tunic is a cellulosic, integumentary matrix found in tunicates (Subphylum Tunicata or Urochordata). The tunics of some ascidian species and pelagic tunicates, such as salps, are nearly transparent, which is useful in predator avoidance. Transparent materials can be detected visually using light reflected from their surfaces, with the dif...

Antarctic krill (Euphausia superba) and salps are major macroplankton contributors to Southern Ocean food webs and krill are also fished commercially. Managing this fishery sustainably, against a backdrop of rapid regional climate change, requires information on distribution and time trends. Many data on the abundance of both taxa have been obtaine...

A doliolid species belonging to the genus Paradoliopsis was photographed by an Autonomous Visual Plankton Recorder (AVPR) off the eastern seaboard of Japan in October 2014 at 493–512 m depth. Two Paradoliopsis gonozooids were also captured on the video record of the ROV Crambon at 372–373 m depth during the same cruise. This is the first record of...

Antarctic krill (Euphausia superba) and salps are major macroplankton contributors to Southern Ocean food webs and krill are also fished commercially. Managing this fishery sustainably, against a backdrop of rapid regional climate change, requires information on distribution and time trends. Many data on the abundance of both taxa have been obtaine...

During 2013–2015, the dissolved 137Cs activity concentrations in seawater off the coast of Fukushima were one or two orders as high as those before the Fukushima accident. The activity concentrations in the surface-layer seawater at NPE2, NP0, NP2, NPE1, AN7, I01, E and A stations, which are located within about 10 km from the coast, relatively hig...

Seasonal variations of Zooplankton community in terms of biomass and size-fractionated densities were studied in a tropical Sangga Kechil river, Matang, Perak from June 2010 to April 2011. Zooplankton and jellyfish (hydromedusae, siphonophores and ctenophores) samples were collected bimonthly from four sampling stations by horizontal towing of a 14...

In the Seto Inland Sea of western Japan, metacercariae of three species of trematodes, Lepotrema clavatum Ozaki, 1932, Cephalolepidapedon saba Yamaguti, 1970, and Opechona olssoni (Yamaguti, 1934), were found in the mesoglea of the jellyfish Aurelia aurita s.l., Chrysaora pacifica, and Cyanea nozakii. Moreover, these jellyfish frequently harbored j...

The potential bioaccumulation of 137Cs in marine food webs off Japan became a concern following the release of radioactive contaminants from the damaged Fukushima nuclear power plant into the coastal ocean. Previous studies suggest that 137Cs activities increase with trophic level in pelagic food webs, however, the bioaccumulation of 137Cs from sea...

The study aimed to evaluate nutraceutical potential of three commercially significant edible jellyfish species (Acromitus hardenbergi, Rhopilema hispidum and Rhopilema esculentum). The bell and oral arms of these jellyfishes were analyzed for their proximate composition, calorific value, collagen content, amino acid profile, chemical score and elem...

The salp Thalia rhomboides is distributed in the shallow depths during the day, and is thus at increased risk of predation by visual predators and from the damaging effects of ultraviolet (UV) radiation compared with species distributed in deeper layers in the daytime. The integument (tunic) of T. rhomboides may have adaptive optical properties, bu...

The Sulu Sea is a semi-isolated, marginal basin surrounded by high sills that greatly reduce water inflow at mesopelagic depths. For this reason, the entire water column below 400 m is stable and homogeneous with respect to salinity (ca. 34.00) and temperature (ca. 10 °C). The neighbouring Celebes Sea is more open, and highly influenced by Pacific...

A review of the current status of DNA barcoding in pelagic cnidarians is given. Most current studies tend towards using the 16S mitochondrial ribosomal RNA gene for barcoding purposes in pelagic cnidarians, judged more appropriate for this group than the mitochondrial COI gene. Although further studies on mitochondrial genome structure and the prev...

A wide variety of fish and invertebrates are associated with marine jellyfishes, and their interactions are diverse. We preliminarily investigated symbionts on two species of rhizostome jellyfishes collected from Leyte and Palawan Islands, the Philippines, in August 2013. The collected jellyfishes were Lobonemoides robustus Stiasny on both islands...

An Autonomous Visual Plankton Recorder (AVPR) was used to record colour in situ images of plankton and other marine particulates at several oligotrophic stations around the world, including a northern hemisphere subtropical open ocean, a northern hemisphere subtropical marginal sea, a southern hemisphere tropical marginal sea, and a polar open ocea...

An Autonomous Visual Plankton Recorder (AVPR) was used to record colour in situ images of plankton and other marine particulates at several oligotrophic stations around the world, including a northern hemisphere subtropical open ocean, a northern hemisphere subtropical marginal sea, a southern hemisphere tropical marginal sea, and a polar open ocea...

Reproductive characteristics of poorly studied hyperiid amphipods, especially Phronimella elongata, are described. Among nine species of hand-collected phronimids, females of Phronimella elongata, Phronima dunbari and Phronima sedentaria cohabited with their young in a ‘barrel' derived from gelatinous zooplankton. Five growth stages of young were i...

Many polypeptides isolated from shallow water cnidarian species have been utilized as valuable biochemical tools in both basic and applied biological sciences. Deepwater cnidarian species might be another potential resource for novel biochemical tools. However, because of limited access to cnidarian samples from deep-sea environments, bioactive pol...

A recently developed untethered but remotely operated survey platform, the PICASSO system, is described. This vehicle was designed specifically for surveys of macro- and megazooplankton and marine particulates (maximum depth 1000 m), to link information on gelatinous zooplankton diversity, behaviour and community structure with their function as pa...

The study was undertaken to determine zooplankton composition and abundance along Perak River estuarine system during the Northeast (NE) monsoon. Monthly samplings were conducted from November 2009 until February 2010. Four sampling stations were selected along the salinity gradient covering stations from the upstream down to 1 km off the coastal s...

The untethered remotely operated vehicle (uROV) PICASSO-1, which is controlled in real time from a surface support vessel via a φ{symbol}0.9 mm fiber optic cable, is capable of dives to 1,000-m depth at a duration of up to 6 h and yet is deployable from ships of sizes as low as 17 tonnes. The vehicle was developed at the Japan Agency for Marine-Ear...

Hippocampus denise, one of the world's smallest seahorses, was described from Indonesia and appears to be relatively widespread in the West Pacific (Lourie and Randall 2003). The widespread occurrence of this species has been recorded in books, dive magazines and on the internet (e.g. Kuiter 2000), and recently the occurrence of this species was re...