The community structure of caprellids inhabiting 3 species of seagrasses was investigated at 6 stations of the sublittoral zone of Otsuchi Bay, northeastern Japan. Ten species of Caprella were collected from 5 stations, while no caprellids were collected from the estuary station where the salinity was 6.8 to 26.4 (PSU). The community structure of caprellids can be separated into two groups; Caprella japonica was strongly associated with Phyllospadix iwatensis which is distributed on rocky outcrops, while C. tcuc arensis was with Zostera marina and Z. caulescens near the inner most part of the bay.

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Morphological and genetic differences between Japanese and Chinese red ark shell Scapharca broughtonii were examined. Differences were recognized between the two forms in all of the morphological characters examined. In particular the number of radial costae and shell weight index differed sufficiently for unequivocal differentiation of the forms, when used in combination. Isozyme analyses of genetic characters indicated differences in allelic frequencies at the MEP-1^*, PGM^* and PROT^* loci. The genetic distance (D value) between the Japanese and the Chinese forms, calculated from isozymic allele frequencies was 0.108, suggesting significant genetic independency of the two forms. The considerable morphological and genetic differences suggested that the Chinese red ark shell is a distinct subspecies or species from Scapharca broughtonii.

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Metabolic aspects of osmoregulation were examined in two species of tilapia. Oreochromis niloticus, a moderate hypo-osmoregulator, was reared in fresh water (FW) or 50% seawater (SW) for 4 weeks with limited diet, while more euryhaline species, O. mossambicus, was keptin FW, 100% SW, or 160% SW. There was no significant difference in plasma concentrations of growth hormone, and Na⁺ and Cl^- among the fish acclimated to different salinities in both species, indicating successful adaptation to each salinity. Plasma levels of prolactins (PRL₁₇₇ and PRL₁₈₈) were significantly higher in FW than in hypertonic environments in both species, confirming their important roles in FW osmoregulation.
Activities of phosphofructokinase, glycogen phosphorylase, and glucose-6-phosphate dehydrogenase, key enzymes in carbohydrate metabolism in the liver, were all higher in 50% SW than in FW in O. niloticus, whereas no difference was seen in O. mossambicus among different salinities. Plasma glucose level also was higher in hyperosmotic environment than in FW only in O. niloticus. There was no difference in liver glycogen contents among the fish adapted to different salinities in both species. The increase in the liver metabolic activity in hyperosmotic environment observed only in O. niloticus, suggests a different efficiency in energy utilization for hypo-osmoregulation between the two species of tilapia.

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Restriction fragment length polymorphism (RFLP) analysis of the mitochondrial DNA (mtDNA) D-loop region was used to compare the genetic diversity of 5 strains of red sea bream Pagrus major. Composite haplotypes, representing the information from 6 restriction endonucleases, were generated for samples of 35-40 fish from each strain. The components of haplotypes in the cultured strains differed considerably from those of the natural population. This is remarkable from the point of view of haplotype specialization. The results of a chi-square randomization test, in which differences between the strains were very significant, also showed that the specializations of haplotype were accelerated. Haplotypes occurred at a rate of 0.11 to 0.29 in the cultured strains, and 0.33 in the natural population. Haplotypic diversities were 0.34 to 0.84 in the cultured strains, and 0.86in the natural population. The UPGMA clustering, based on pure mean nucleotide sequence divergence, differed entirely from the UPGMA clustering based on the allozyme genetic distance. For this reason, it is thought that RFLP analysis of the mtDNA D-loop region could sensitively detect the bottleneck effect caused by a decrease in the effective number of parents. The pure mean nucleotide sequence divergences between the cultured strains were wider (17 times) and higher (29 times) than the values between the natural population. Thus, RFLP analysis of the mtDNA D-loop region was thought to be a good method for monitoring the genetic changes that occur during selective breeding.

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Relative values of hepatopancreas and intestinal weight to somatic weight were significantly higher in the tiger puffer Takifugu rubripes (puffer) than the red sea bream Pagrus major (bream). Relative values of intestinal length to body length were reversely high in the bream, indicating that the puffer have intestines with large diameters.
Feces of the fishes were periodically collected after feeding on a test diet with 0.5% Cr₂O₃. Small amounts of feces and fecal Cr₂O₃ were obtained in the puffer until 72 hours after feeding (hAF), but those in the bream showed a great change, reaching a peak at 8-12 hAF and decreasing rapidly thereafter.
Intestinal digesta of the puffer fed 1.5% body weight of the test diet fell gradually until 48 hAF. In the bream fed the same ration size of the test diet, gastric digesta fell markedly until 9 hAF, but intestinal digesta was maintained at a relatively constant and low level until 24 hAF. Moreover, apparent protein, fat, and sugar digestibilities in intestinal digesta of the puffer rose gradually and linearly from 8 to 32 hAF, however, those of the bream were already high at 3 hAF and then tended to fall slightly until 24 hAF.
The results suggest that the puffer, which do not have a stomach, conduct digestion and absorption more slowly than the bream, which have a stomach.

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The tiger puffer Takifugu rubripes (puffer) and the red sea bream Pagrus major (bream) were fasted or fed 1/4, 1/2, and 1 satiation of an artificial diet for 20 days, and digestive and absorptive ability and energy flow were composed. The puffer fed 1/2 and 1 satiation of the diet showed higher feeding rate, growth rate, feed efficiency, protein efficiency ratio, and protein retention than those of the bream fed under the same feeding protocols. Higher fat retention and protein digestibilities were obtained in the bream, however, no marked difference between the fishes was found in sugar and fat digestibilities, excepting the lowest fat digestibility of the puffer fed 1 satiation. Although the bream tended to show better digestable, metabolizable, and retention energy than the puffer, higher standard metabolizable energy was obtained in the puffer. Energy expenditure for heat increment plus voluntary activity was less in the puffer. These suggest that low energy expenditure for heat increment plus voluntary activity in the puffer, which do not have a stomach, compensates for poorer protein digestibilities than those in the bream, which have a stomach.

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The relationship between the strontium content and growth rate of otoliths was examined in the goldfish Carassius auratus. After 131-day rearing of hatched larvae, asterisci and lapilli were dissected, measured for length and weight, and analyzed for calcium and strontium contents by atomic absorption spectrophotometry. Data were expressed in terms of the growth rate of each otolith.
Lapilli were smaller and contained 4.7 times more strontium than asterisci. Calcium content did not differ between the lapilli and asterisci and had no significant correlation with the growth rate of either otolith. On the other hand, strontium contents showed significant negative correlations for otoliths with low growth rates in both asterisci (correlation coefficient, r=-0.46) and lapilli (r=-0.62). Sr/Ca ratios also showed similar correlations for otoliths with low growth rates (r=-0.46 and -0.64 for asterisci and lapilli, respectively). These results indicate that strontium tends to incorporate into otoliths in the slow phase of calcification.

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The effects of injection of 17, 20β-dihydroxy-4-pregnen-3-one (DHP) on induced ovulation in the artificially matured Japanese eel Anguilla japonica were examined, with special reference to the effect of injection time on the time of ovulation. Ovulation occurred 18h and 21h after injection of DHP at 9:00, in 10 of 15 females and in the remaining 5 females, respectively. Injection of DHP at 18:00 induced ovulation 15, 18, and 21h after injection in 4, 12, and 2 of 18 females, respectively. Fertility and hatching rates were not significantly different between females which ovulated 18h after injection at 9:00 or 18:00. In the second experiment, eggs from females which ovulated 15h after DHP injection showed significantly higher fertility (about 63%) and hatching rates (about 54%) than eggs from females which ovulated 18h after the injection. These results indicate that the time of ovulation depends on the time elapsed after the DHP injection in the eel.

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A stock population of the apple snail has been maintained for artificial selection without human interference and has become inbred. Hatchability fluctuated significantly among the egg lumps, and average hatchability decreased with the decrease in number of mature snails in the stock population.
Heritability of hatchability was estimated from the regression line of hatchabilities of offspring to that of their parents; the value was 0.461. The realized heritability was calculated from the first selection for high and low hatchability, and the values were 0.398 for high hatchability and 1.427 for low hatchability.
High heritability probably involved heterotic effects, because of decreased hatchability observed in full-sib mating.

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We have numerically modeled the transport and survival processes of Japanese sardine eggs and larvae Sardinops melanostictus in the Kuroshio-Oyashio region to investigate thedependence of yearly recruitment of the sardine on the mortality rate during the early life stages. The model covers from 130°E to 160°E and simulates the Kuroshio Current and wind-induced current resulting from the winter monsoon in a simple way. As a biological process, natural mortality of the eggs and larvae is parameterized by area and year, considering the oceanographic condition such as the extent of southward intrusion of the Oyashio. The year-to-year variations in the amount of survivors simulated by the model are compared to that of one-year sardine stock based on the field data. The variation in the abundance of one-year old sardine is well correlated to that of the surviving juveniles off the east but not the south of Japan, both of which are calculated by the model. This indicates that the survival condition after the postlarval period off the east coast of Japan, which is strongly affected by the Oyashio, could play an important role in determining the year class strength. A strong year class can be formed by the numerous juveniles transported to the east and/or by the good survival condition in the eastern offshore region of Japan.

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Bacterial strains were isolated from the intestinal tract of river fish and the environmental water and sediment, and examined for their antibacterial abilities against Aeromonas hydrophila ATCC 7966, A. salmonicida ATCC 33658, Escherichia coli IAM 1264 and Staphylococcus aureus ATCC 25923 using a double agar-layer method. A total of 940 isolates including aerobic and anaerobic bacteria were classified into 13 taxonomic groups. Almost all specimens of carp and crucian carp harbored Aeromonas, Enterobacteriaceae and Bacteroidaceae (including Bacteroides type A) as predominant intestinal microflora. All fish specimens harbored the bacteria with antibacterial abilities. An average of 2.1% of tested strains exhibited antibacterial activity against the four target strains, but the activity varied with fish species, intestinal segments and sampling times, along with taxonomic groups of tested bacteria. The target strains were inhibited mainly by the predominant microflora of fish intestines: 3.2-10.3% of strains belonging to Bacteroides type A and other Bacteroidaceae inhibited the growth of A. salmonicida ATCC 33658 while 3.1-7.4% of strains of genus Aeromonas exhibited the inhibitory effect against E. coli IAM 1264 and S. aureus ATCC 25923. These results may suggest that these bacteria affect the composition of intestinal microflora of river fish, to some extent, by producing antibacterial substances.

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Japanese flounder Paralichthys olivaceus were artificially infected with Edwardsiella tarda by three different methods, viz., intraperitoneal injection (IpI), oral intubation (O1), and immersion (IMM). Moribund stages were attained earliest (4-5 days) in IpI group, followed by IMM (7-10 days) and OI (9-10 days) groups. However, almost the same trend in the fate of E. tarda, monitored by viable count, was observed regardless of inoculation methods. The viable number of the pathogen continuously increased in all the four tissues tested (blood, intestine, liver, and kidney) for7 days after inoculation and reached the highest levels at moribund stages. The viable counts in the intestine, liver and kidney tissues were always higher than those in the blood. Histopathological examination demonstrated abscess formations in the liver together with massive hepatocytic necroses. Kidney conditions were characterized by necrotic lesions involving nephrons and abscess formations. Intestine showed only sporadic necrosis in the villar epithelia and abscess in the tunica propria. The abscesses and diffuse necrotic lesions in these three tissues were characterized by migration of E. tarda-laden phagocyticcells. Phagocytosis and intraphagocytic multiplication of the pathogen in these tissues were confirmed by enzyme labeled antibody technique (ELAT) and electron microscopy.

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The stomach contents of 100 yolk-sac larvae and 376 larvae of Spanish mackerel collected in the Seto Inland Sea from 1981-1983 were examined. Standard lengths (SL) of prey animals were back-calculated from their body heights (BH).
Late stage yolk-sac larvae with eye pigmentation had jaw teeth and gastric blind-sac, and some of them had already initiated feeding. Stomach contents of larvae consisted primarily of fish larvae, though invertebrate zooplanktons were observed in some early stage larvae. Main prey of Spanish mackerel larvae were larval Clupeiformes, 21% being Japanese anchovy (93% of identified Clupeiformes). The ratios of head length (HL), upper jaw length (UJL), and body height (BH) to SL of Spanish mackerel larvae increased as larval size increased until 11mm SL, then remainedconstant. The back-calculated maximum size and the size range of Japanese anchovy larvae eaten by Spanish mackerel larvae increased until 12mm SL. Spanish mackerel larvae larger than 12mm SL fed on 8-12mm SL Japanese anchovy larvae.
The feeding incidence was high for early larval stages: 66, 84, and 92% in 4-5, 5-6, and 6-7mm SL larvae, respectively. These results suggest that Spanish mackerel larvae collected in the Seto Inland Sea actively fed mainly on fish larvae from the first feeding stage.

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The motility and fertility of the Japanese eel testicular spermatozoa, which hadacquired motility during an incubation with K30 solution (consisting of 30mM KCl, 134.5 mM NaCl, 1.3mM CaCl₂, 1.6mM MgCl₂, 20mM NaHCO₃, and buffered with 20mM TAPS-NaOH at pH 8.1), were compared with those of the milt spermatozoa obtained from the genital pore of a Japanese eel. The motility percentages of milt spermatozoa and testicular milt spermatozoa, were 84.7±4.1% and 2.6±1.9%, respectively. The percent motility of incubated testicular milt spermatozoa was 63.3±2.2%. The fertility and hatchability of the milt and incubated testicular milt were significantly higherthan those of testicular milt. There were no significant differences found between the fertility and hatchability of the milt and those of the incubated testicular milt. To examine the toxicity of the high potassium oncentration in the K 30 solution on egg fertility, we compared the fertility and hatchability ofmilt spermatozoa diluted with K 30 solution or K 15 solution. No significant differences in the fertility or hatchability were found between the K 30 and the K 15 solutions. These results indicate that the testicular spermatozoa which acquired motility during their incubation in K 30 solution are just as fertile as the motile milt spermatozoa, and that K 30 solution is suitable as a milt diluent in the artificial fertilization of the eel.

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A new preparative method of purified G-actin from myofibril of carp dorsal muscle was developed. Myofibril suspended in 0.1M KCl was treated with acetone and converted into dried myofibril-powder. Polymerizable G-actin was extracted from the powder with ATP containing solution. G-actin was purified by collecting the pellet at 40% saturated ammonium sulfate. The G-actin purified by the above procedures was indistinguishable from the conventional G-actin in its purity, yield, and abilities to polymerize and to interact with myosin. G-actin thus prepared was proved to be resistant to high-salt (such as 40% saturated ammonium sulfate, 4.5M NaCl or 3.5M KCl) treatment.

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G-actin was extracted from the acetone-dried myofibril-powder of walleye pollack, rainbow trout, carp and rabbit, and was purified by collecting the pellet at 40% saturated ammonium sulfate. Their thermal denaturation upon heating in the presence of ATP was compared by monitoring the actin-activated subfragment-1 Mg-ATPase, and the chymotryptic digestability. It was demonstrated that there is practically no difference in the stability among species; G-actin denaturation took place above 50°C for all species. Thermal stability of walleye pollack actin in myofibril was studiedby measuring the amount of G-actin extracted from the acetone dried powder of the heated myofibril. Decrease was detected above 50°C, which was rather similar to that for causing G-actin enaturation.

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A chitinase (EC 3. 2. 1. 14) was purified from the liver of Japanese common squid Todarodes pacificus by ammonium sulfate fractionation and column chromatographies with Chitopearl Basic BL-03, CM-Toyopearl 650 S, and Bio-Gel HTP. The purified enzyme gave a single protein band on polyacrylamide gel electrophoresis (PAGE), and its molecular weight was estimated tobe 38 kDa by SDS-PAGE. The isoelectric point was 8. 3. The enzyme showed two optimum pHs at 1.5 and 8.5 using glycol chitin as the substrate. The enzyme was stable between pH 4.0 and 6.0 after incubation at 50°C for 10 min. The optimum temperature was 50°C. The chitinase hydrolyzed glycol chitin and colloidal chitin, but not p-nitrophenyl N-acetyl-β-D-glucosaminide and Micrococcus lysodeikticus. The cleavage pattern was investigated using N-acetylchitooligosaccharides (GlcNAc_n, n=2 to 6). The enzyme hydrolyzed GlcNAc₄ to two molecules of GlcNAc₂, GlcNAc₅ to GlcNAc₂ plus GlcNAc₃, and GlcNAc₆ to GlcNAc2 plus GlcNAc₄ (84%) and two molecules of GlcNAc₃ (16%). The substrate specificityof the enzyme was that of endo-type chitinase.

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Tauropine dehydrogenase (tauropine: NAD oxidoreductase) was purified to homogeneity from the sponge Halichondria japonica Kadota (colony). Relative molecular masses of this enzyme in its native form and in its denatured form were 36, 500 and 37, 000, respectively, indicating a monomeric structure. The maximum rate in the tauropine-iosynthetic reaction was observed at pH 6.8, and that in the tauropine-catabolic reaction at pH 9.0. Pyruvate and taurine were the preferred substrates. The enzyme showed significant activity for oxalacetate as a substitute for pyruvate but much lower activities for other keto acids and amino acids. The tauropine-biosynthetic reaction was strongly inhibited by the
substrate pyruvate. The optimal concentration of pyruvate was 0.25-0.35mM and the inhibitory concentration giving half-maximal rate was 3.2mM. The tauropine-catabolic reaction was inhibited by the substrate tauropine: the optimal concentration was 2.5-5.0mM. Apparent K_m values determined using constant cosubstrate concentrations were 37.0mM for taurine, 0.068mM for pyruvate, and 0.036mM for NADH in the tauropine-biosynthetic reaction; and 0.39mM for tauropine and 0.16mM for NAD⁺ in the tauropine-catabolic reaction.

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To recover efficiently proteins from fish frame that is remained on bone portions after filleting fish in fish processing manufactory, the enzymatic recovery by hydrolysis was applied. The enzyme was a crude proteinase partially purified from tuna Thunnus thynnus pyloric caeca. Tuna pyloric caeca crude proteinase (TPCCP) showed the highest hydrolytic activity for BAEE (N-benzoyl-L-arginine ethyl ester), synthetic substrate of trypsin. The optimum activity condition of TPCCP for fish (cod; Gadus macrocephalus) frame proteins, the deboned proteins isolated from fish frame, was known as pH 10 at 45-50°C. The hydrolysis reaction for cod frame by TPCCP was attained to an end after 12h incubation in the above condition. Under the optimum reaction conditions for the same enzyme concentration, the degree of hydrolysis by TPCCP on time course was similar to those by purified proteinases such as chymotrpysin, pronase E, papain, etc. After the cod frame was treated with TPCCP for 12h at 50°C, all tissues, mainly muscle proteins, were readily digested from fish bone and approximately 80% of the total soluble protein was hydrolyzed. Therefore, it appeared that the protein from fish frame as fish processing waste could be efficiently recovered with TPCCP.

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To examine the dietary effects of hijiki Hijikia fusiformis, aonori Enteromorpha sp., and nori Porphyra sp., which are traditional marine foodstuffs in Japan, on the levels of serum lipid and cecal microflora, diets containing 1% and 5% of these algae were administered to male rats for one week. All of the diets containing algae increased the weight of feces. The diets containing 5% algae increased the weight of cecum. Both the ingestion of 1% and 5% nori diet reduced the weight ofliver. Except the diet containing 1% hijiki, the test diets suppressed cecal ammonia, cecal free fatty acids (FFA), serum triglycerides (TG), and serum FFA. In the case of the diet containing 5% nori, the number of bifidobacteria and total viable counts in the cecum were markedly higher than those of the control diets. The diet containing 5% aonori suppressed the numbers of enterobacteriaceae and lactobacilli in the cecum and elevated cecal pH to a significantly high value of about 8. 6. These results indicate that hijiki, aonori, and nori, have similar effects on serum lipids and different effects on intestinal microflora and environment.

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This study was conducted to clarify whether krill meal contained in the soft-dry pellets (SDP) was responsible for the improved spawning performance and egg quality of yellowtail broodstock. After the termination of a previous study, broodstock from the experimental lots fed on raw fish, moist pellets and soft-dry pellets were separately kept on a commercial SDP for about 5 months. Thereafter, the fish which had been fed entirely on SDP were offered a test diet without krill meal supplementation, whereas broodstock which had been fed moist pellets or raw fish were fed test diets containing 20 and 30% krill meal, respectively; all for about 5 months prior to spawning.
The total egg production, the hatching rate among the fertilized eggs and the rate of normal larvae were the highest in the eggs obtained from the brood fish fed SDP without krill meal supplementation; these figures decreased relatively with the increase of krill meal in the diets. The rates of buoyant and fertilized eggs among the total eggs produced were not markedly different. It appears that higher levels of krill meal in the SDP was not beneficial for yellowtail brood fish.

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Alanine racemase [EC 5. 1. 1. 1], which catalyzes the interconversion of D-, L-alanine, was partially purified from the muscle of the black tiger prawn Penaeus monodon using DEAE-cellulose, DEAE-Toyopearl, hydroxyapatite, Phenyl- and Butyl-Toyopearl, and Gel-Toyopearl HW column chro-matographies. The final enzyme preparation was not homogeneous but the purification was as high as about 17, 700-fold with a final yield of 2.5%.
Apparent molecular weight of the enzyme in its native form was 85, 000. The maximal activity was attained at 35-40°C and at around pH 8. 5. The alanine racemase was inactivated between 40 and 60°C and was also rather unstable during low temperature storage. The enzyme acts specifically on D-, L-alanine as substrates, but not on the other amino acids in the present assay conditions. The enzyme did not require pyridoxal 5'-phosphate or FAD as a cofactor. The enzyme was inhibited strongly with pyruvate and L-alanine, which are metabolites from D-alanine.

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Parvalbumin content and its isoform pattern in the muscle of red sea bream Pagrus major were analyzed during the course of development from the larval stage to adult stage. Parvalbumin content in the muscle was found to increase from the larval stage to juvenescence stage, followed by a small decrease until the young stage. Furthermore, its isoform pattern was found to change from the larval stage to adult stage. These results indicate that parvalbumin is closely related with muscle development.

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β-N-Acetylhexosaminidase (EC 3. 2. 1. 52) in moon jellyfish mesogloea was extracted with 50mM sodium phosphate buffer (pH 6.0) and purified by chromatographies on CM-Toyopearl 650M and Toyopearl HW-55 F. By these two purification steps, the enzyme was isolated from crude extracts. A final specific activity of 17875 units/mg and 19-fold purification were attained. The molecular weight of the enzyme was estimated to be about 130, 000 by gel filtration on Toyopearl HW-55F. By SDS-PAGE, the enzyme was composed of a subunit molecular mass of 64, 000. The optimum pH was 4 and the enzyme was stable at the range between 4 and 5. This enzyme was extremely unstable in comparison with those from other species. The optimum temperature was 50°C. The enzyme was strongly inhibited by Hg²⁺, CH₂ICOOH, and DTNB, but was slightly activated by K⁺, Na⁺, Mg²⁺, Cu²⁺, and Ca²⁺. The enzyme hydrolyzed various oligosaccharides, and the rate of hydrolysis of N-acetylchitooligosaccharides tended to decrease with increasing degree of polymerization of the substrate. Moreover, in comparison with some other species, this enzyme had a high affinity for p-nitrophenyl-2-acetamide-2-deoxy-β-D-glucopyranoside.

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A sialoglycoprotein (SGP) has been purified from the skin mucus of the stingray Dasyatis akajei. SGP contained 22.1% (w/w) NeuAc, 24.4% GalNAc, 9.9% GlcNAc, 6.1% Gal, and 27% amino acids, and its average molecular weight (Mr) was estimated to be 500, 000. SGP was very rich in Thr (32 mol%) and Ser (12 mol%). Treatment of SGP with alkali (β-elimination of carbohydrate chains) result-ed in the destruction of 70% of Thr and Ser, indicating that the carbohydrate chains were attached through these amino acids. Exhaustive digestion of SGP by actinase yielded a highly glycosylated glycopeptide with Mr of 50, 000. Based on these results, it is assumed that a SGPmolecule bears more than 400 oligosaccharide chains which are attached to the Thr and Ser residues of the polypeptide backbone and spaced at an average of 3 amino acids apart.

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Thermal properties of several jellyfish mesogloea were studied using the differential scanning calorimeter. As a result, the three endothermic peaks were shown for many jellyfish. The first, second, and third peak corresponded to myosin, sarcoplasmic proteins and/or collagen, and actin. Each transition temperature (Tm) in jellyfish were lower than those in mammals. Although the three endothermic peaks were shown for hydrozoan jellyfish, the highest Tm were lower than the lowest one for the other jellyfish. Only two peaks were shown for cubic jellyfish. It was suggested that the first and second peak corresponded to sarcoplasmic protein and/or collagen and actin.
Moreover, it did not related between the water temperature in the sampling occasion and the denaturation temperature of each protein in jellyfish.

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Myosins and their rod fragments from fast skeletal muscles of carp acclimated to 10 and 30°C were digested with α-chymotrypsin. Myosins in 0.12M NaCl were digested at 10°C with the protease at an enzyme-to-myosin weight ratio of 1/100 which cleaved mainly the region connecting myosin subfragm-
ent-1 and rod. When relative amounts of remaining myosin heavy chain band from the 10°C-acclimat-ed carp were plotted on a logarithmic scale against reaction time, digestion wasfound to proceed in the first order reaction with 4.2×10^-4 s^-1, which was lower than 6.1×10^-4 s^-1 for the 30°C-acclimated carp (P<0.05). The other region, which is susceptible to protease and located between myosin subfragment-2 and light meromyosin, was examined at 10°C using myosin rod in 0.5M KCl and α-chymotryp-sin with an enzyme-to-rod weight ratio of 1/120. Both myosin rods from the 10-and 30°C-acclimated carp gave about 2×10^-4 s^-1, with no differences in protease susceptibility. These results are in marked contrast to our previous observation that myosin from the 10°C-acclimated carp is less thermostable in the crossbridge head and α-helical region of the rod part than that from the 30°C-acclimated carp.

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Two experiments were conducted in order to examine the effect of a high amount of vitamin A (VA) given through Artemia on the vertebral development of larval Japanese flounder Paralichthys olivaceus. Ten-day-old flounder larvae were cultured for 30 days. In Experiment I, larvae were fed on Artemia enriched in a 10-liter medium containing 100mg VA palmitate (1 μg VA palmitate=1 IU VA), starting from different larval stages until metamorphosis, or at a different rearing period. In Experiment II, critical larval periods (three days) of feeding Artemia enriched in a 10-liter culture medium containing 100mg VA palmitate on vertebral development were examined.
Enrichment of Artemia with 100mg VA palmitate in a 10-liter culture medium resulted in 1069 and 918 IU VA per g Artemia (dry basis) in Experiments I and II, respectively. Feeding on Artemia containing these high VA concentrations caused the compression of vertebrae in flounder. This vertebral deformity was found to occur when larvae were exposed to these high dosages of VA during the G stage (during day 25-27, about 11mm of total length) in which notochord segmentation tookplace. The effect of high dosage of VA was even more distinct in fish receiving VA for a longer period, a high incidence of deformity being accompanied by retardation of growth.

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