Five species of penaeid shrimps in the genus Penaeus exist in the Pacific coast of Central America and are commercially important. The morphology of their wild postlarvae has not been studied for all the species, causing difficulties of reliable identification and resource management.
The present study examined the wild postlarvae of the five species and describes sequentially their morphological characters such as dorsal spinules, antennal spine, relative rostral length, thoracic spines, and rostral teeth. These characters were used to prepare an identification key for the wild postlarvae of the five species. The dorsal spinules on the 6 th abdominal somite and those around the epigastric tooth were found to be subgeneric diagnostic characters, and the taxonomic importance of the thoracic spines was demonstrated.

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Attempts to re-establish dense colonies of a deposit-feeding polychaete, Capitella sp. I for promoting the organic decomposition of organically polluted marine sediment below fish net pen culture need more information on the oxygen consumption characteristics of the worms. In this study, the oxygen consumption characteristics of Capitella colonies have been examined in laboratory conditions by using a method consisting of measuring the depletions of dissolved oxygen concentrations ([O₂];mg O₂/l) over the reconstituted sediment cores containing a given number of active adult Capitella. Oxygen uptake rate (OUR) of the worms (ca. 20, 000 individuals/m²) was calculated and expressed as an oxygen flux (mg O₂/m²•h) Worm OUR was found to be a function of [O₂] and can be characterized by OUR=14.45+36.75 log [O₂], under an constant temperature of 21±1°C. Compared to other benthic oxygen consumption data, respiratory activities of Capitella colonies were slightly low. During oxygen depletion periods, the worms have revealed an ability to adapt well. Moreover, they still survived for several days although ambient [O₂] was beneath 0.3-0.5mg O₂/l. These results demonstrated that Capitella has appropriate abilities to be utilized as an effective biological treatment for poorly oxygenated sediment below fish net pen culture areas.

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We built a forecasting system for the path types of the Kuroshio current and the distance between the Kuroshio axis and Cape Iroh-zaki. A layered type of the artificial neural network was used in the system. Input data sets included six months' precedent data of distances between the Kuroshio axis and major capes, occurrence rates of Kuroshio path types and deviations of sea surface temperature. The predicted values of the hydrographic conditions in the months of March and April were well matched to the observed values. The investigation of the interconnection weight values suggests that the deviations of sea surface temperature and occurrence order of the Kuroshio path types significantly affected the predictions in the neural network. As the catch of sardine larvae in Sagami Bay during March and April is affected by the path types of the Kuroshio current and the distance between the Kuroshio axis and Cape Iroh-zaki, the predicted results will be used to forecast the catch.

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A theoretical prolate spheroid liquid model is used to predict the target strength (TS) of krill. Scattering patterns are shown to demonstrate orientation dependence of krill TS. Length-to-wavelength ratio (L/λ) dependencies of reduced (normalized by square of the body length) target strength are shown for some orientation distributions. The results can explain the well-organized experimental results. The variability of the TS of krill is large when L/λ is larger than unity, therefore, a frequency around 70 kHz is superior to 120 kHz which is ordinarily used for krill surveys.

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Bacterial tolerance to bis-tributyltin oxide (TBTO) and triphenyltin chloride (TPT) was compared at different contaminated areas by the agar plate method. The TBT concentration at which colony forming units (CFU) began to decrease (inhibitory concentration, IC) was almost the same within the range of 2 to 40 μg Sn/l of TBTO for all samples but one. The proportions of TBTO-tolerant bacteria were also not related to the ambient level of contamination. The Tolerance of bacteria in sediment samples was higher than that in water samples from each station, but was not proportional to the level of contamination. The numbers of TPT-tolerant bacteria did not reflect the numbers of TBTO-tolerant bacteria. These findings demonstrate that the distributions of TBT- and TPT-tolerant bacteria were independent to of the level of TBT contamination.

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To prove air breathing, common carps Cyprinus carpio acclimated at 27°C were subjected to the following experiments after a 3 h precooling period in water by decreasing the temperature to 17°C. 1) Each fish with a plugged oesophagus was accommodated in a respiratory chamber connected to gas meters for measurements of concentration changes of O₂ and CO₂ at 17°C. 2) Each group of five fish was exposed to 17°C air to examine its 100% survival time.
Over time, the O₂ concentration decreased and that of CO₂ increased. The CO₂ concentration showed a saturation curve. Mean respiratory rates in the initial period of 1-1.5 h were 51±24.2ml O₂ per kg•h and 24±5.8ml CO₂ per kg•h. The 100% survival time with a 3 h precooling was 4.5 h. As a conclusion, carp breathe following an incomplete CO₂ excretion even in air.

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We induced homozygous clones of amago salmon by gynogenetic chromosome manipulation. Mitotic gynogenesis diploid (mitotic-G2N) as first generation was produced by suppression of the first cleavage of the eggs inseminated with UV-irradiated sperm of rainbow trout by hydrostatic pressure shock. The yield of apparently normal gynogenetic embryos was 2.26% when the eggs were shocked at 650kg/cm² of hydrostatic pressure for 6min at 5 h 30min (approximately 68 h•°C in cumulative temperature) after insemination. Homozygous evidence of gynogenetic juveniles was demonstrated by the segregation of Idh-3 and Pgm-1 loci. Five homozygous inbred strains were produced from the eggs of homozygous gynogenetic females by retaining the second polarbody, while outbred controls were produced for each strain by crossing with males of other strains. The clonal proof of these strains was demonstrated by the immunological acceptance of operculum allografts from inbred sisters. Similar survivals were shown among clones produced by mothers from identical strain. On the other hand, various survivals were seen between the clones using maternal parents from different strains. These results suggested that the line selection was a vital factor in clone production.

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Larval and juvenile prawns P. japonicus were fed test diets containing fresh or oxidized corn, squid liver, and pollack liver oils. In the larval study, the peroxide values (POV) of test oils added to each of the test diets were respectively 0.6, 24.6, 69.8 meq/kg oil for fresh (Of), slightly oxidized (Os), and mildly oxidized (Om) oils for the corn oil-based diets, 0.3, 19.8, 37.6 meq/kg oil for corresponding squid liver oil-based diets, and 1.7, 25.5, 38.6 meq/kg oil for corresponding pollack liver oil-based diets. In the juvenile study, these figures are respectively 0.6, 29.9, 44.3 meq/kg oil for corn oil-based diets, and 1.9, 35.3, 45.8 meq/kg oil for pollack liver oil-based diets.
Os and Om oils delayed development, reduced postlarval size, and weakened the postlarva₁ although mortality was not so high. A POV of more than 13 meq/kg seems to be a critical level for larvae whereas a POV of 35 meq/kg was still within the allowable degree of oxidation for juveniles. The size of postlarva₁ was reduced further when fed diets containing marine Os or Om oils compared to vegetable oil such as corn oil.

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The oxidative stability of sardine lipids increased remarkably with an increase in heating time a 100°C under a nitrogen atmosphere. Therefore, factors affecting the stability of heated lipids were investigated. A combination of phospholipids with non-polar lipids was indispensable for producing this heat-induced stabilization. An interaction between the ethanolamine residue of phosphatidylethanola-mine and the polyunsaturated fatty acids in triglycerides during heating seemed to participate in the prolongation of the induction period in lipid autoxidation; however neither phosphatidylcholine nor phosphocholine residue was effective in prolonging the induction period of lipids. Therefore, the mechanism of lipid oxidation of cooked fish meat is presumed to be much more complicated than is commonly thought.

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A transglutaminase-free actomyosin was prepared from Alaska pollack frozen surimi and various physico-chemical properties were investigated on the suwari gel prepared from it. The elastic modulus and viscosity of the gel increased rapidly at the initial stage of setting from the starting surimi, up to 70-80% value of the suwari gel, and gradually decreased after setting for 10 h. SDS-polyacrylamide gel electrophoresis of the gel revealed that a band due to myosin heavy chain gradually decreased as the setting progressed and the bands due to myosin heavy chain polymers increased somewhat. These findings suggest that both the setting of the surimi paste and the aggregation of myosin heavy chain still proceed even without transglutaminase.

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The accumulation of histamine during the storage of fish meat does not depend only on histamine-forming bacteria but also on histamine-decomposing bacteria. To clarify the mechanisms of histamine accumulation, changes in the numbers of both histamine-decomposing and histamine-forming bacteria and histamine contents were examined during the storage of common mackerel at 5 and 30°C for two months each throughout the year.
In the case of samples stored at 5°C, the histamine contents, once accumulated, decreased and disappeared when the sample putrefied as histamine-decomposing bacteria took over (more than 10⁶ cells/g) and the pH value became neutral. At 30°C storage, the histamine content did not always decrease, suggesting that the histamine-decomposing ability of the bacteria might therefore be inhibited at 30°C.

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The carp β-globin gene was cloned and the nucleotide sequence was determined. The carp β-globin gene contains three exons and two introns, as do other vertebrate β-globin genes. The coding regions of exons I, II, and III were 93 base pairs (bp), 222 and 129 bp in length, respectively. The intervening sequences were 106 and 121 bp long, respectively. A TATA box was found 88 bp upstream from the start site (ATG) of translation. In the 3' flanking region, there were two poly adenylation signals, AATAAA, on 90 and 172 bp downstream from the stop codon (TAG) of translation. The predicted amino acid sequences from the carp β-globin gene and cDNA were the same. The amino acid identity of the carp β-globin gene with those reported in other vertebrates including goldfish, rainbow trout, duck, goose, chicken, rat, and human, ranged from 52.4 to 97.3%. The carp β-globin has one inserted amino acid residue, which was also found in the reported amino acid sequences of other fish β-globins, but not in the other vertebrate β-globin polypeptides. The carp β-globin gene consisted of a family structure from the results of Southern hybridization.

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Zinc-induced activation of rainbow trout metallothionein-A (rtMT-A) promoter was investigated in transgenic medaka using chloramphenicol acetyltransferase (CAT) gene as a reporter. The plasmid prtMT-A-CAT containing rtMT-A promoter and CAT gene was microinjected into medaka fertilized eggs at the one-cell stage. Hatched fry, in which the transgene was detected by PCR, were exposed to 0 to 100 μM of ZnCl₂ and the promoter activity was monitored by CAT assay. The activity was induced dose-dependently at concentrations of ZnCl₂ over 1 μM. These results suggest that the rtMT-A promoter was useful for controlling expression of transgenes in transgenic fish by experimental conditions.

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In a study of chemical inducers for larval settlement and metamorphosis in the sea urchins Pseudocentrotus depressus and Anthocidaris crassispina, eight out of 16 commercially-available fatty acids (five saturated and 11 unsaturated) induced larval responses. Fatty acids lacking or having only one double bond in the molecule had no inducing effect. Highly unsaturated fatty acids induced high rates of larval responses, but caused larval abnormalities at higher concentrations. The responses of the sea urchin larvae to the assayed fatty acids was highly specific with respect to the chain length and the number of double bonds in the molecule.

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The oxidative stability of free fatty acid (FFA) mixtures from soybean, linseed, and sardine oils in an aqueous solution was compared with that in air. Due to its high contents of DHA and EPA, sardine oil FFA was most rapidly oxidized in air, followed by linseed and soybean oil FFAs. However, this order was reversed in autoxidation in an aqueous solution (pH=7.4 at 37°C). Gas chromatographic analysis showed that sardine oil FFA was most oxidatively stable in the aqueous solution and about 78% of polyunsaturated fatty acids (PUFAs) remained unchanged after 168h of oxidation, while soybean oil FFA was highly susceptible to autoxidation in the aqueous solution, losing more than 80% of PUFAs after only 40h of oxidation. This unusual order of oxidative stability in an aqueous solution can be explained by correlation with the micellar conformations of individual FFA mixtures in an aqueous solution.

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Three active compounds have been isolated from the brown alga Sargassum thunbergii whose lipophilic extract promoted larval metamorphosis in two kinds of ascidians Halocynthia roretzi and Ciona savignyi. The most active compound was identified as diphlorethol by means of spectral data, while a mixture of phlorotannins was also afforded as a promoter. The last active compound was determined to be a mixture of sulfoquinovosyl diacylglycerols by spectral analysis. All compounds induced larval metamorphosis of H. roretzi and C. savignyi at a concentration of 25 μg/ml.

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Meat firmness of muscles of sixteen crustacean species was examined to clarify the contribution of the following three factors to the raw meat texture: 1) total collagen content in muscle, 2) distribution of intramuscular collagen fibers, and 3) properties of an α component, α2 (AR-I), which is one of the constituents of Type AR-I collagen. Total collagen content varied among species, ranging from 0.04 to 0.58% per wet tissue and from 0.4 to 3.5% per total tissue protein. The component α2 (AR-I) was distributed widely among custacean species, but it was not detected in some species of crabs. Moreover, a considerable difference in the relative staining intensity of the α2 (AR-I) component to the total collagen (α2 (AR-I)/total collagen) was revealed among species.
The muscles of prawns and shrimps which showed relatively high collagen content and high relative staining intensity of α2 (AR-I)/total collagen tended to be firm in contrast to those of crabs, whose firmness and collagen contents were lower. In light microscopic observation, the muscles of prawns and shrimps exhibited a dense distribution of collagen fibers, while the muscles of crabs had a sparse distribution. These results indicated that the three factors described above had very important roles in determining the raw meat texture of crustaceans.

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The changes in content of ATP and related compounds were investigated in the muscle of oyster, hard clam, ark-shell, and abalone during storage at 5°C. We evaluated the efficacy of the K, K', and A. E. C. values calculated from the content of ATP and related compounds as freshness indices. The degradation patterns of ATP and related compounds were different among the 4 species. ATP decreased rapidly in the oyster and hard clam, but gradually in the ark-shell and abalone. AMP accumulated in all 4 species, while further degradation to IMP and/or HxR occurred markedly in the oyster and ark-shell. Although the K values on the hard clam, ark-shell, and abalone were low at the acceptable stage, the K' value on the hard clam increased slowly but linearly and increased rapidly and linearly for the oyster and ark-shell from the beginning of storage. For the ark-shell and abalone, the A. E. C. value decreased rapidly and linearly during the acceptable stage. The K' and A. E. C. values appeared to be useful as freshness indices for shellfishes.

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White croaker and walleye pollack frozen surimis were manufactured with CaCl₂-washing of the minced meat. The behavior of several components in the fish meat during manufacturing was then investigated.
CaCl₂ rapidly permeated into the minced meat and prevented the washed meat effectively from swelling during the washing processes. The greater the Ca content of the washed meat, the easier it was to remove the water during the dehydrating process. Simultaneously, the concentration of myofibrillar protein in the materials was caused by elution of water-soluble protein from the same meat. Such behavior was affected by the suppression of swelling of the washed meat by CaCl₂. Thus, the myofibrillar protein content and the myofibrillar Ca-ATPase total activity of the frozen surimi increased, although a slight denaturation of the myofibrillar Ca-ATPase of the materials could not be avoided due to CaCl₂-washing of the minced meat.
These reuslts suggest that the efficiency of manufacturing frozen surimi and the quality of the surimi based-products could be improved by adopting this method under appropriate conditions.

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