Geographical distribution and age composition of Euphausia superba larvae (Crustacea：Euphausiacea) in the South Shetland Islands region and southern Scotia Sea in relation to environmental conditions

Spatial distribution patterns of the different life stages of Euphausia superba in the region of the South Shet- land Islands and southern Scotia Sea （Antarctica） were assessed based on scientific survey data collected in lanuary and February of 2010. Adults, eggs, nauplii, metanauplii, calyptopis I-Ill, and furcilia I-II were found in the investigation. The abundance of larvae averaged 1 172.8 ind./mz, with calyptopis I and II as the dominant stages. Habitat occupancy patterns varied among Euphausia superba at different stages, and three sub-regions were identified by cluster analysis. The degree of larval development increased from west to east. Larvae were not observed north of the South Shetland Islands. Calyptopis I was predominant in the water between Elephant Island and the South Orkney Islands, which featured no thermocline. Older stages, including calyptopis II and III and furcilia I and II, were common in north and northeast of the South Orkney Islands, which were characterized by high temperature and high chlorophyll concentration. Distri- bution and abundance of the early life stages of E. superba were associated with specific environmental con- ditions. According to Biota-Environment matching （BIOENV）, the distributions of E. superba larvae were correlated with a combination of temperature at the surface and 200 m, and 0-100 m integrated chlorophyll a concentration.     

葛氏长臂虾的幼体发育

于１９９１年４月，从长江口采集葛氏长臂虾标本，实验室进行幼体发育研究，结果表明，幼体自孵出后，在水温２４℃、盐度１２、饵料充足的条件下，有规律的每２天蜕皮１次，共经１１次蜕皮，约２２ｄ完成变态，入仔虾期。     

Species composition and spatial distribution of euphausiids of the yellow sea and relationships with environmental factors

We investigated species composition and spatial distribution of the euphausiid community in the Yellow Sea and identified the relationship with environmental factors (temperature, salinity, chlorophyll a, nitrate, phosphate, and silicate) using bimonthly data from June, 1997 to April, 1998. The environment varied during the sampling period. In warm seasons, thermocline was well developed rendering lower temperature and higher salinity and nutrient concentrations in the bottom layer. During cold seasons the water column was well mixed and no such vertical stratification was noted. Horizontal distribution of temperature, however, differed slightly between near-coast and offshore areas because of the shallow depth of the Yellow Sea, and between southern and northern areas because of the intrusion of water masses such as Yellow Sea Warm Current and Changjiang River Diluted Water. Four euphausiid species were identified:Euphausia pacifica, E. sanzoi, Pseudeuphausia sp. andStylocheron affine. E. sanzoi andS. affine were collected, just one juvenile each, from the southern area in June and December, respectively.Pseudeuphausia sp. were collected in the eastern area all the year round except June.E. pacifica occurred at the whole study area and were the predominant species, representing at least 97.6% of the euphausiid abundance. Further, the distribution pattern of the species was varied in regards to developmental stages (adult, furcilia, calyptopis, egg). From spring to fall,E. pacifica adults were abundant in the central area where the Yellow Sea Bottom Cold Water prevailed. Furcilia and calyptopis extended their distribution into nearly all the study area during the same period. From late fall to winter, adults were found at the near-coastal area with similar pattern for furcilia and calyptopis. The distribution pattern ofE. pacifica was consistent regarding temperature, salinity, and three nutrients during the sampling period, whereas chlorophyll a showed a different pattern according to the developmental stages. The nutrients should indirectly affect via chlorophyll a and phytoplankton concentration. With respect to these results, we presented a scenario about how the environmental factors along with the water current affect the distribution ofE. pacifica in the Yellow Sea.     

Larval stages,developmental ecology,and distribution of Scyllarus sp. Z (probably Scyllarus aoteanus Powell, 1949) (Decapoda: Scyllaridae)

Phyllosomata and nistos of Scyllarus sp. Z taken from plankton around and offshore northern New Zealand and in the Tasman Sea are presumed to be those of S. aoteanus Powell, 1949, the most common Scyllarus species in this area. The full larval and postlarval development of this species are described. Three features are characteristic of Scyllarus sp. Z phyllosomata; a dorsal crest on the cephalic shield, dorsal thoracic spines, and a forked telson in middle stages persisting as two prominent spines outreaching the telson posterior margin in the final stage. Scyllarus sp. Z's closest affinities are with a group of Scyllarus species whose phyllosomata have forked telsons in middle stages and medium to strong posterolateral telson spines in the final stage. The nisto is low in profile but distinctive in its armature. Too few Scyllarus sp. nistos have been described to suggest any group to which that of Scyllarus sp. Z can be assigned. The spatial and temporal distribution of the larvae and postlarvae of Scyllarus sp. Z are also described. Although early larval stages and postlarvae are found close to New Zealand, mid‐ and late‐stage larvae are widely distributed, some well beyond the known latitudinal range of the adults. There is probably an extended egg‐bearing and hatching period as early stage larvae are caught in most months. Variable rates of development of the larvae and/or delayed metamorphosis, are also possible.     

Life history ofEuphausia similis (crustacea,euphausiacea) in Sagami Bay,central Japan

The life history ofEuphausia similis G.O. Sars in Sagami Bay, central Japan, has been studied by examining the abundance, size distribution, and occurrence of each growing stage from egg to adult. Three cohorts were laid within the period from July 1979 to July 1980. Individuals of cohort I of 1980 were laid in November and December 1979, and matured and spawned in March and April of the following year. Those of cohort II of 1980 laid in January and February 1980 should mature in November and spawn after December, by analogy with cohort II of 1979. Cohort III of 1980 was laid in April 1980, but decreased in number in July. Cohort II was the dominant cohort in Sagami Bay throughout the period studied. From December 1979 to April 1980 when the mixing layer was present, many eggs ofE. similis were in the epipelagic zone. It is suggested that the spawning season ofE. similis roughly coincided with the season of active feeding, indicated by high fullness of stomachs in individuals. The production of juveniles and adults was about 1.33 mg C m^–2 day^–1, and the production to bio mass (P/B) ratio was estimated to be 4.78 between July 1979 and July 1980.     

Mesoscale distribution of larval Euphausia similis in various water masses of the East Australian Current

Larval Euphausia similis were collected off temperate eastern Australia in spring 2004 and 2006 to evaluate the relationships between larval populations, mesoscale oceanographic variability, and the wider planktonic community. Larval E. similis were present in greater numbers in the East Australian Current (EAC) relative to productive coastal waters. Larval E. similis density was homogenous across the EAC—Tasman Sea frontal region, but larvae were smaller in the Tasman Sea. Larval E. similis density was not enhanced within a cold core eddy relative to the surrounding EAC. We observed a negative correlation between larval E. similis density and larval fish density, and a weak positive correlation with fluorescence. Evaluation of a significant fish density×fluorescence interaction term showed that the effect of fish density was reduced at high fluorescence values. Analysis of normalized biomass size spectrum (NBSS) provided evidence for potential competitive exclusion of copepods by krill. Data presented in this study suggest a predatory influence on surface E. similis populations by mesopelagic larval fish. The degree of predation appears to be dependent on food availability, potentially mediated by changes in the physiological condition of krill.     

Occurrence patterns of mesopelagic fish larvae in Sagami Bay, central Japan

The species composition, seasonal abundance, and vertical distribution of mesopelagic fish larvae are described based on discrete depth sampling from the surface down to 1000 m depth during four cruises at a fixed sampling station in Sagami Bay. The abundances of total mesopelagic fish larvae in April, July, September, and December were 65.7, 13.6, 118.9, and 17.2 individuals per 10 m² sea surface, respectively. Twenty species or types of mesopelagic fish larvae belonging to 10 families were collected. Diaphus garmani, Lipolagus ochotensis, Diogenichthys atlanticus, Sigmops gracile, and Maurolicus japonicus were the five most abundant larvae and accounted for 43.1, 14.5, 7.4, 6.3, and 5.9% of the total mesopelagic fish larvae, respectively. These five species showed clear seasonal changes in abundance, i.e. L. ochotensis, D. atlanticus, and S. gracile larvae mainly occurred during winter— spring; D. garmani and M. japonicus were collected during summer—autumn. No obvious diel vertical migration was found in these larvae. The larvae of D. garmani and M. japonicus were concentrated in the 25–50 and 50–100 m depth layers, respectively. The transforming stage of L. ochotensis, S. gracile, and D. atlanticus occurred at 400–1000 m depth, while their larvae (<8 mm standard length) occurred in the upper 100 m layer, indicating that metamorphosis of these species takes place in the 400–1000 m layer. Based on the occurrence of mesopelagic fish larvae and oceanographic processes in Sagami Bay, with the exception of D. garmani and M. japonicus, most larvae are considered to originate from the Kuroshio region where their main spawning grounds are formed.     

南极夏季南设得兰群岛周边海域浮游动物优势种群的分布、丰度及种群结构分析

根据2013/2014年夏季在南极南设得兰群岛周边海域使用北太平洋网采样品及同步环境调查资料,分析了南极大磷虾(Euphausia superba)、拟长臂樱磷虾(Thysanoessa macrura)、尖角似哲水蚤(Calanoides acutus)和近缘哲水蚤(Calanus propinquus)这四种优势浮游动物的丰度和分布特征。结果表明,南极大磷虾和拟长臂樱磷虾在南设得兰海域均有较为广泛的分布,其中南极大磷虾丰度较高,且它们的水平分布存在一定程度的空间分离。在研究海域东部的南奥克尼群岛(South Orkneys)邻近海域发现了大量的南极大磷虾原蚤状C期幼体,表明大磷虾曾于1月中上旬左右产卵繁殖。研究海域的东部南极大磷虾种群结构以幼体前期为主,而西部的种群结构则以幼体后期、未成体和成体为主。尖角似哲水蚤和近缘哲水蚤的空间分布也较为广泛,且两者分布基本一致。东部南奥克尼群岛临近海域的浮游植物浓度较低,这可能是大量南极大磷虾幼体和桡足类摄食活动的结果。     

First record of three giant marine Bathynomids (Crustacea, Isopoda, Cirolanidae) from India

Three species,Bathynomus decemspinosus,B.doederleini and B.kensleyi (Crustacea,Isopoda,Cirolanidae),are reported for the first time from the Parangipettai coastal waters,Southeast coast of India.Several Trilasmis (Temnaspis) tridens (Cirripedia Thoracica,Lepadomorpha) were attached to the pleopods of some individuals.So,five bathynomid species are currently reported from India.     

Two records of patchy occurrences of the oceanic shrimpSergestes similis Hansen off the east coast of Honshu,Japan

Two recent records of the occurrences of the pelagic shrimp,Sergestes similis Hansen, are reported. They provide evidence of dense swarms ofS. similis in midwater off the east coast of Honshu, Japan, in spring. On one occasion,S. similis was found in a stomach of the basking shark,Cetorhinus maximus (Gunnerus). The shark, 8.11 m in total length, was accidentally trapped in a set net off Izu-oshima Island on April 18, 1974, and its foregut was filled only withS. similis. Feeding and swimming behavior of the basking shark, condition of the gut contents, and temperature profiles of the sea revealed thatS. similis was preyed upon by the shark near the island when the shrimp swarmed below 100 m depth at night. On another occasion,S. similis was fished by a commercial ground trawler 31 miles off Cape Shioyazaki on April 4 and 5 and off Hitachi on April 11, 1976. The trawlings were made around 500 m depth at daytime, and a total of 3.8 tons ofS. similis was caught and marketed. The size-frequency distribution and sex ratio ofS. similis in both occurrences from off Izu-oshima Island and off Cape Shioyazaki coincided very well. The samples consisted of identical population of probably 2nd year class having a body length mode between 46.0 and 50.0 mm. The sex ratio was skewed greatly toward females in both samples, that is 38∶2 and 100∶3 respectively. These two phenomena are discussed in relation to the life history ofS. similis.     

Congruence between euphausiid community and water region in the northwestern Pacific: particularly in the Oyashio–Kuroshio Mixed Water Region

The relationship between euphausiid community structure and water region was studied during a 2-year seasonal survey in the northwestern (NW) Pacific Ocean. The euphausiid community structure and its associated species were analyzed from 38 micronekton samples collected during eight cruises. The euphausiid community structure and its distribution patterns clearly corresponded to physical oceanographic features in the Oyashio region, Oyashio–Kuroshio Mixed Water Region (OKMWR), and Kuroshio region. In contrast, community structure was unrelated to seasonality. The 19 species out of 40 identified in this area were grouped and named after their habitats. The six cold-water species were grouped into three regional types: two coastal Oyashio species, three Oyashio–OKMWR species, and one Oyashio–Kuroshio species. The four species dominating in the OKMWR were categorized into each specific types: Nematoscelis difficilis as OKMWR–Oyashio species, Euphausia gibboides as OKMWR species, Euphausia similis as OKMWR–Oyashio & OKMWR–Kuroshio species, and Euphausia recurva as OKMWR–Kuroshio species. The seven warm-water species were categorized as Kuroshio–OKMWR species or Kuroshio species. The other two species were categorized as cosmopolitan species. In particular, regarding the result in the OKMWR, our study suggest that (1) the OKMWR has high species diversity, and (2) the dominant species, such as Euphausia pacifica, N. difficilis, E. similis, and E. gibboides, are considered to be key species in the food webs in this region.     

Spatial distribution of sister species of vesicomyid bivalves Calyptogena okutanii and Calyptogena soyoae along an environmental gradient in chemosynthetic biological communities in Japan

Vesicomyid bivalves have a substantial biomass in deep-sea chemosynthetic biological communities in the Pacific. Using a novel multiplex-PCR (mPCR) method to identify the co-occurring vesicomyids in Sagami Bay, we analyzed the distribution of Calyptogena okutanii and Calyptogena soyoae along environmental gradients. All the known distributions of C. okutanii indicated the different preferences in salinity and temperature to those of C. soyoae, and in Sagami Bay, depth seemed to be an important environmental factor, too. Although the concentration of hydrogen sulfide in sediment was not examined, our results showed that the distributions of these two Calyptogena clams were affected by salinity and temperature.     

Stage-V copepodites of Calanus sinicus and Calanus jashnovi (Copepoda: Calanoida) in mesopelagic zone of Sagami Bay as identified with genetic markers, with special reference to their vertical distribution

We applied genetic makers to identify Calanus species occurring in Sagami Bay, Japan, in order to investigate their vertical distribution in the upper 1000 m. First, interspecific genetic distances of three gene loci, mitochondrial small ribosomal RNA (srRNA), nuclear internal transcribed spacers 1 (ITS1) and 2 (ITS2), were estimated from morphologically distinguishable adult females of Calanus sinicus, Calanus jashnovi and Calanus pacificus that were collected from Sagami Bay, the Kuroshio Extension and the Oyashio region, respectively. The highest levels of interspecific genetic distance were observed in srRNA, followed by ITS1 and ITS2. The intraspecific genetic distances within C. sinicus were much lower than the interspecific genetic distances, indicating that DNA sequences in these loci are consistent with the morphological differences. This information was used as a criterion for species identification based on DNA sequence variation, and allowed us to identify the fifth copepodites (CVs) or younger stages of these species. Next, the vertical distribution of Calanus species was investigated in Sagami Bay in May 2006, on the basis of a stratified sampling in the upper 1000 m. By applying the genetic markers, 23 individuals comprising all copepodite stages were allocated into either C. sinicus or C. jashnovi, and the small- and large-sized CVs were identified as C. sinicus and C. jashnovi, respectively. The total abundance of C. sinicus was highest at 0-50 m and decreased with depth. On the contrary, CV individuals of C. sinicus were abundant not only in 0-50 m but also below 200 m with minimum occurrences in 150-200 m depth. C. jashnovi was much less abundant than C. sinicus and comprised of only CIV and CV which occurred in the upper 100 m and deeper than 50 m depths, respectively. The abundance of C. sinicus in the 1000-m water column of Sagami Bay was at a level comparable to that in shelf waters, suggesting the importance of off-shelf individuals in the biological production and organic transport in the respective areas.     

The seasonal succession of zooplankton in the Southern Ocean south of Australia,part I: The seasonal ice zone

Between November 2001 and March 2002 an Australian/Japanese collaborative study completed six passes of a transect line in the Seasonal-Ice Zone (south of 62°S) along 140°E. Zooplankton samples were collected with a NORPAC net on 22–28 November, and a Continuous Plankton Recorder on 10–15 January, 11–12 February, 19–22 February, 25–26 February, and 10–11 March. Zooplankton densities were lowest on 22–28 November (ave=61 individuals (ind) m⁻³), when almost the entire transect was covered by sea ice. By 10–15 January sea surface temperature had increased by ∼2 °C across the transect line, and the study area was ice-free. Total zooplankton abundance had increased to maximum levels for the season (ave=1301 ind m⁻³; max=1979 ind m⁻³), dominated by a “Peak Community” comprising Oithona similis, Ctenocalanus citer, Clausocalanus laticeps, foraminiferans, Limacina spp., appendicularians, Rhincalanus gigas and large calanoid copepodites (C1–3). Total densities declined on each subsequent transect, returning to an average of 169 ind m⁻³ on 10–11 March. The seasonal density decline was due to the decline in densities of “Peak Community” taxa, but coincided with the rise of Euphausia superba larvae into the surface waters, increased densities of Salpa thompsoni, and an increased contribution of C4 to adult stages to the populations of Calanoides acutus, Calanus propinquus and Calanus simillimus. The seasonal community succession appeared to be influenced by the low sea ice extent and southward projection of the ACC in this region. The relatively warm ACC waters, together with low krill biomass, favoured high densities of small grazers during the January/February bloom conditions. The persistence of relatively warm surface waters in March and the seasonal decrease in chlorophyll a biomass provided favorable conditions for salps, which were able to penetrate south of the Southern Boundary.     

五种经济海水鱼类的染色体研究

采用PHA体内注射──空气干燥制片法初步研究了5种海水鱼类的染色体。核型公式分别为鲻鱼、鲈鱼和黄姑鱼2n＝48t，NF＝48，其中鲻鱼的t1染色体、鲈鱼的t12染色体及黄姑鱼的t3染色体均为具明显次缢痕染色体，矛尾复虎鱼2n＝44，2m＋42st、t，NF＝46，其t18染色体为具次缢痕染色体；绿鳍马面2n＝40t，NF＝40，其中t14染色体具次缢痕。     

Carapidae larvae (Acanthomorpha,Paracanthopterygii, Ophidiiformes) from the oceanic region of the southwest Atlantic Ocean off Brazil (12–22°S)

We report the occurrence and distribution of Carapidae larvae in the southwest Atlantic Ocean, between Real River (12°S) and São Tomé Cape (22°S), off Brazil. Carapidae larvae were collected during three oceanographic cruises: spring 1998, winter 1999 and autumn 2000. The hauls were conducted obliquely from a maximum depth of 200 m, during day and night, with bongo nets 330- and 500-μm mesh size. Three species were recorded in this study: Carapus bermudensis, Echiodon dawsoni and Snyderidia canina. Only one C. bermudensis was collected during the winter cruise off the Salvador coast (13°S). Twenty-one larvae of E. dawsoni were collected during the three cruises between 14.5° and 22°S, including some at the banks of Vitória–Trindade Ridge. One S. canina larva occurred, during the spring in the north coast of Rio de Janeiro (22°S).     

Some aspects of the biology of the micronektonic fishCyclothone pallida andC. acclinidens (Pisces: Gonostomatidae) in Sagami Bay,Central Japan

Some aspects of the biology of the micronektonic fishesCyclothone pallida andC. acclinidens are described on the basis of samples taken during a series of 20 cruises from December 1982 to November 1985 at a fixed station near the center of Sagami Bay, Central Japan.C. pallida is a regular component of theCyclothone population in Sagami Bay, being found in more than 90% of the samples. On the other hand,C. acclinidens was encountered sporadically, being found in less than 25% of the samples. The depth range ofC. pallida is estimated to be about 400–1,000 m. It spawns mainly during the spring and summer in Sagami Bay.C. pallida releases about 1,000–3,000 eggs and may spawn several times during its life span. On the average, it reaches 18.5 mm standard length (SL) in one year, 24 mm SL in two years and 29.5 mm SL in three years during its subadult stage. Extrapolation of the growth curve suggests that males and females attain first sexual maturity in three to four years at 30–35 mm and five to six years at 40–45 mm SL, respectively.Cyclothone pallida is concluded to have a regular life cycle in Sagami Bay. It remains uncertain whether or notC. acclinidens reproduces in this area.     

Spatial and seasonal distribution of adult Oithona similis in the Southern Ocean: Predictions using boosted regression trees

We applied a multivariate statistical modelling technique called boosted regression trees to derive relationships between environmental conditions and the distribution of the adult stage of the cyclopoid copepod Oithona similis in the Southern Ocean. Nearly 20 000 samples from the Southern Ocean Continuous Plankton Recorder survey (87% from East Antarctica) were used to model the probability of detection (presence) and relative abundance of adults of this zooplankton species in surface waters. We demonstrate that it is possible to obtain reasonable models for both the presence (area under the Receiver Operating Characteristic curve of 0.77) and relative abundance (28–35% variance explained) of adult O. similis between November and March in much of the Southern Ocean. No investigation was possible where the environmental characteristics were not well represented by the SO-CPR dataset, namely, the Argentine shelf, Weddell Sea, and the frontal region north of the Amundsen Sea, or under sea-ice. Our analyses support the hypothesis that adult O. similis abundance is related to environmental conditions in a broadly similar way throughout the Southern Ocean. Compared to a compilation of net-haul data from the literature, the abundance model explained 34% of the variance in surface concentrations of adult stages of this species, and 23–59% of the variance in depth-integrated abundance of copepodite and adult stages combined. The models show higher occurrence and elevated abundances in a broad circumpolar band between the Antarctic Polar Front and the southern boundary of the Antarctic Circumpolar Current (approximately 54–64°S). Evidence of diel vertical migration by adults of this species north of 65°S was found, with surface abundances 20% higher at night than during the day. There was no evidence of diel migration south of 65°S. Five potential “hotspots” of adult O. similis were identified: in the southern Scotia Sea, two areas off east Antarctica, in the frontal zone north of the Amundsen Sea, and a small area in the outer Bellingshausen Sea. We recommend that a database of all available net-haul data on Oithona similis in the Southern Ocean be created to facilitate further investigations on the circumpolar distribution of this species.     

东山湾底栖介形类一新种(介形纲:壮肢目:海萤超科)

本文记录采自福建省东山湾的底栖介形类真喜萤属一新种:多刺真喜萤Euphilomedes spinulosasp.nov对其进行绘图和详细的描述,并与它的相似种非洲真喜萤Euphilomedes africanus(Klie,1940)进行特征比较,确定其新种地位。多刺真喜萤Euphilomedes spinulosasp.nov鉴别特征:(1)左壳腹缘内侧中部具13束短刺毛束;(2)第1、2、4、6对尾叉爪为主爪且细长,第3、5和7~11对尾叉爪为副爪,其中,第3和第5对爪夹于主爪之间;(3)第7附肢末端的开口下缘仅具1弯刺。