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1.
ABSTRACT: The reproductive traits and the monthly larval abundance of the mantis shrimp Oratosquilla oratoria were investigated in Tokyo Bay, Japan, in 2002. The goal of the study was to elucidate the cause of changes in the monthly pattern of larval abundance from the 1980s to the 1990s as these changes relate to variation in the stock size of the adult shrimp. Oogenesis was divided into 10 stages by histological observation. The developmental stage of oocytes in an individual's ovary was synchronous, suggesting that almost all the oocytes in an ovary are spawned at the same time. The size at first maturity was estimated to be 7 ≤ body length ( BL ) < 8 cm. Fecundity was expressed as a function of BL , ranging from 19 300 eggs for 8 cm BL to 92 100 eggs for 14 cm BL . Small female shrimps (<10 cm BL ) spawned around August. Most large female shrimps (≥10 cm BL ) spawned around May, and some large female shrimps also spawned until September. Although most large female shrimps spawned in spring, the larval abundance was low before July and high from August onwards. The results suggest that a substantial decrease in the stock size of large individuals causes the low larval abundance before July. 相似文献
2.
Keita?KodamaEmail author Takashi?Yamakawa Takamichi?Shimizu Ichiro?Aoki 《Fisheries Science》2005,71(1):141-150
ABSTRACT: In this study, the age composition of the Japanese mantis shrimp, Oratosquilla oratoria , in Tokyo Bay, central Japan, was investigated using lipofuscin, an autofluorescent pigment, as an age marker. Lipofuscin in a histological section of protocerebral bridge cell mass (PBCM) in the brain was identified by confocal microscopy, and its concentration was quantified by image analysis. Modal analysis of the lipofuscin concentration showed four regularly-spaced modes that could each be regarded as a distinct age group. This implied a constant lipofuscin accumulation in PBCM at a 6.5 × 10−2 % volume fraction per year; it also implied the existence of individuals that are at least 4 years old. The lipofuscin concentration was found to be a more appropriate index than body length for estimating the age of O. oratoria , because the modal analysis on the body–length histogram failed to detect apparent age groups. This was probably a result of the declining growth rate with age and the individual variations in growth through molting leading to considerable overlap in the size between different age groups. The lipofuscin analysis suggested that fast-growing individuals in each cohort are recruited to the fishery, and most individuals attain the exploitable size between 2 and 3 years of age. 相似文献
3.
Haruo Yamaguchi Yuko Tanimoto Takamichi Yoshimatsu Shinya Sato Tomohiro Nishimura Keita Uehara Masao Adachi 《Fisheries Science》2012,78(5):993-1000
Blooms of toxic dinoflagellates of the genus Ostreopsis, which is known as a producer of palytoxin (PTX) analogs, may pose a threat to human health in tropical, subtropical, and temperate regions around the world. In the present study, we established a suitable culture method for Ostreopsis spp. isolated from Japanese coastal waters and characterized their growth potential using the method to discuss their bloom dynamics. Each clonal strain of Ostreopsis cf. ovata, Ostreopsis sp.?1, Ostreopsis sp.?5, and Ostreopsis sp.?6 was incubated in 25?×?150?mm test tubes with a flat bottom containing various kinds of medium. Since Ostreopsis spp. strains grew well in IMK and/or f/2 media, we selected these media for cultivation of all the Ostreopsis spp. isolates. Growth rates of O. cf. ovata (0.834?divisions/day), Ostreopsis sp.?1 (0.619?divisions/day), and Ostreopsis sp.?6 (1.04?divisions/day) that produce PTX analogs significantly differed (p?<?0.05) respectively and are clearly higher than those of other reported epiphytic dinoflagellate Gambierdiscus toxicus, Prorocentrum lima, and Coolia monotis cultures, which suggest that these species have ecological advantages to predominate through the algal succession in Japanese coastal waters, resulting in a potential risk to human health in this region. 相似文献
4.
Changes in reproductive patterns in relation to decline in stock abundance of the Japanese mantis shrimp Oratosquilla oratoria in Tokyo Bay 总被引：2，自引：0，他引：2
ABSTRACT: We investigated changes in the reproductive patterns of mantis shrimp Oratosquilla oratoria concurrent with stock-abundance decline in Tokyo Bay, Japan. Stock abundance was high in the mid to late 1980s but decreased abruptly in the early 1990s. The yearly change in annual mean larval abundance was similar to that of stock abundance. Mantis shrimp in the bay have two spawning seasons, an early season (May–June) for ≥1-year-old individuals and a late season (July–September) for 0–1-year-old individuals. This general reproductive pattern does not differ among different stock-abundance levels. However, the monthly pattern in larval abundance has changed with stock-abundance decline; larval abundance from the early spawning season was highest in the high-stock-abundance period, and it decreased significantly in the low-stock-abundance period, probably as a result of decreased spawning-stock abundance of large female mantis shrimp ≥1-year-old. Correlation analysis on the egg production index and larval abundance suggested that during this low-stock-abundance period the population is supported mostly by late-hatched larvae spawned by small, 0–1-year-old female mantis shrimp. Considering the reproductive pattern and the present status of the fishery, the stock of small female mantis shrimp should be conserved to enhance reproduction of the population for stock recovery. 相似文献
5.
Mami Harada Tadashi Tokai Michiyo Kimura Fuxiang Hu Takamichi Shimizu 《Fisheries Science》2007,73(3):477-488
ABSTRACT: In Tokyo Bay, conger tube-trap fishers voluntarily deployed escape holes of at least 13 mm diameter to reduce the by-catch of young conger smaller than the marketable size of 35 cm total length. Comparative fishing experiments in Tokyo Bay were carried out using tube traps with seven hole diameters (3, 9, 13.5, 14, 15, 17, and 19 mm), to obtain the size-selectivity of the escape-hole size for inshore hagfish Eptatretus burgeri and white-spotted conger Conger myriaster . On the assumption of the geometrical similarity in the combination of body g and hole perimeter m at a given retention probability, a single master curve s ( R ) = exp(−13.52 + 11.31 R )/(1 + exp [−13.52 + 11.31 R ]) was estimated for the two species in terms of relative R = g / m using the Share Each LEngth's Catch Total (SELECT) process based on a multinomial distribution. Almost all conger and hagfish with a girth equivalent to the hole perimeter were able to pass through the hole. Thus, the two species have a high ability to escape through a narrow space by squeezing the body through the hole in the rigid PVC tube. Optimum escape-hole size is discussed from several objectives for conger tube-trap fishery management, e.g. reduction of hagfish by-catch. This study also specifies the conditions for pooling data when fishing experiments using more than two fishing gears are replicated. 相似文献
6.
Yugo Kitazawa Osamu Netsu Takamichi Nijo Tetsuya Yoshida Akio Miyazaki Shinichiro Hara Yukari Okano Kensaku Maejima Shigetou Namba 《Journal of General Plant Pathology》2014,80(6):499-503
Since 2006, a commercial grower in Japan has noted a leaf blight symptom on potted cosmos plants grown in a field. In August 2012, a Pseudomonas-like bacterium was isolated from the symptomatic leaves and found to cause the same symptom on cosmos seedlings after inoculation. On the basis of bacteriological and phylogenetic analyses, the causative bacterium was identified as Pseudomonas cichorii. This is the first report of bacterial leaf blight on cosmos caused by P. cichorii in Japan. 相似文献
7.
Keiji OKADA Kazue YAJIMA Takamichi OHBA Tamako MIYAZAKI Takenori ORIHASHI Shigeru SATO Jun YASUDA 《Animal Science Journal》2010,81(1):89-93
Eight Holstein bull calves were divided into two groups; a non-treated control group and a famotidine treated group. Fresh milk was fed twice a day. The experiment was conducted between 7 and 14 days of age. During the experimental period the control group was injected with physiological saline, and the famotidine group was injected with famotidine, a histamine-H2-receptor blocker, into the jugular vein 30 minutes prior to each feeding. The control group showed maximum curd formation 2 h after feeding at both 7 and 14 days of age. Curd scores of 7-day-old and 14-day-old calves were significantly lower in the famotidine than in the control group at 2 and 4 h after feeding. Most fecal samples from the famotidine group exhibited an acidic smell. The famotidine group showed significantly lower values for both average weight gain and the rate of weight gain from 7 to 14 days of age. The inhibition of gastric acid secretion decreased curd formation in the abomasum as well as daily weight gain compared to non-treated control calves. This suggested that curd formation in the abomasum is important for the weight gain of newborn calves. 相似文献
8.
Keita Kodama Masaaki Oyama Jeong-Hoon Lee Yoshiaki Akaba Yoshihiro Tajima Takamichi Shimizu Hiroaki Shiraishi Toshihiro Horiguchi 《Fisheries Science》2009,75(4):875-886
To explore which lifestages affect the stock size of young-of-the-year mantis shrimp Oratosquilla oratoria in Tokyo Bay, Japan, we investigated interannual variations in the quantitative relationships among egg production, larval
density, and juvenile density. We collected adult females, larvae, and juveniles during monthly field surveys from 2004 to
2007. The interannual trend for the juvenile density index differed from those for egg production and larval density; although
indices of both egg production and larval density were high in 2004 and 2007, the juvenile density index was high only in
2007, suggesting high mortality during the pelagic larval stage or the early phase of the postsettlement juvenile stage in
2004. We found that larval settlement started at the end of August and peaked in October, although larvae from the early spawning
season (May–June) should have settled in August or earlier. Juveniles were found throughout the bay except in areas where
bottom hypoxia occurred, suggesting that hypoxia restricts the spatial distribution of juveniles. Our results suggest that
mortality during the early life history fluctuates among years, probably because of changes in environmental conditions in
the bay, resulting in interannual variation in the stock size of young-of-the-year juvenile O. oratoria. 相似文献
9.
Groundwater contamination by nitrates is a worldwide problem, but to date there have been no effective measures to purify contaminated groundwater. If a denitrifying system can be constructed in aquifers, it will be able to purify groundwater in situ. This purifying system should also be maintenance free. The purpose of our work is to construct a maintenance-free denitrification system for in situ groundwater purification. This paper presents the result of a basic study on a maintenance-free denitrification system using biodegradable plastic and iron powder. A biodegradable plastic (polylactic acid, PLA) and iron powder were used as detergents, and the nitrate-contaminated groundwater was injected from the bottom of a packed silica sand column filled with a mixture of the detergents. Laboratory experiments were carried out, varying factors such as molecular weight of the biodegradable plastic and mixing ratio of the detergents. Water that permeated through the purification column was sampled to determine the decrease in nitrate concentration. The experimental results suggest that a combination of PLA and iron powder seems effective for denitrification, and that the rate of the PLA degradation is closely related to the molecular weight of the PLA and iron powder content. In this case iron powder acts as accelerator in denitrification. It is concluded that a maintenance-free denitrification system can be built, using PLA and iron powder as detergents. The proposed system may also be used in a wide range of nitrate contamination conditions, adjusting the molecular weight of the PLA and the mixing ratio of the detergents. 相似文献
10.