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The influence of temperature on the hemolymph CO_2 solubility coefficient (αco_2) and the apparent dissociation constant of carbonic acid (pKapp) in Mytilus coruscus was investigated. Mytilus coruscus hemolymph was equilibrated with standard CO_2 gas mixtures to obtain expressions for αco_2 and pKapp as a function of temperature. The relationship between αco_2 and temperature (T) is expressed as follows： αco_2 = 138.247 – 11.253 • T + 0.554 • T^2 − 0.0140 • T^3 + 0.000138 • T^4. The following relationship between pKapp and temperature was found： pKapp = 6.6407 – 0.01589 • T . The parameter units are ℃ for T and µM/L/torr for αco_2. These equations enable estimation of hemolymph αco_2 and pKapp at arbitrary temperatures and simple calculation of Pco_2 and [HCO_3^–].

In 2023, a new seafood cracker named Bakan-Senbei was commercialized in collaboration with National Fisheries University and two private companies. The standout feature of Bakan-Senbei is that it is made from low-utilized/unutilized fish, which contributes to the Sustainable Development Goals. Focusing on this feature, two types of questionnaires（A and B）were implemented to evaluate visitors’ perception of its quality at the Osaka Seafood Show held in February 2024. In questionnaire A, we investigated the potential demand price after providing product information. In questionnaire B, the potential demand price was examined by intentionally excluding only the material information, and then the potential demand price was examined while first excluding material information； then it was examined again after only providing material information and excluding lust time. Interval regression analysis revealed no significant difference between the potential demand prices from the two questionnaires. This result revealed that consumers did not recognize the added value converted into monetary value as perceived quality of the use of low-utilized/unutilized fish. This result indicated that consumers did not perceive the added value of using low-utilized /unutilized fish as translating into monetary value in terms of quality. Conversely, there was a significant difference between the two groups regarding the provision of material information in questionnaire B. This result was supported by the outcome that 21% of respondents raised the rank of potential demand price due to the provision of material information. We estimated the increase price to be 5.5 yen, which was 4.5% of the list price. It was suggested that the added value could be improved by providing important information.

Triacid staining solution (neutral mixture) contains dye complex. Here, we speculate on the structure and characteristics of the dye complex in various triacid staining solutions. It was inferred that the dye complexes in the Ehrlich (methyl green + 2 acid fuchsin, methyl green + 2 orange G, methyl green + acid fuchsin + orange G), Romanowsky (eosin + methylene blue), and Pappenheim (eosin + methylene azure) triacid stains behave as acidic dyes, and that the dye complexes do not dissociate against weakly acidophilic objects, resulting in staining with a complex color (purple). Therefore, it can be said that the objects to which the dye complexes bind without dissociation do not need to be basophilic. When the stained material is highly acidophilic or basic, the dye complex dissociates, and the acidophilic object is stained by the acidic dye and the basiophilic object by the basic dye. The dissociation of dye complexes depends on the degree of acidophilicity and basophilicity of the stained material, and the dissociation depends on the types of dye composing the dye complexes. The dye complex in a triacid stain can be defined as a purple acidic dye in which the bonds between the acidic and basic dyes in the complex can be broken, depending on the acidophilic and basophilic strength of the object.

Previously, we speculated on the staining principle of triacid staining solution (neutral mixture) containing a dye complex. The principle could be explained solely by the relationship between the stained object and the dye complex. We propose here to extend the staining principles of triacid stain to explain the staining principles of other dye mixtures such as May-Grünwald (MG), Giemsa and MG-Giemsa. In a mixture of acidic and basic dyes, the staining characteristics of the object were presumably determined by the degree of stainability (degree of acidophilicity or basophilicity) of the object, the degree of stainability of both dyes (degree of basophilicity of the acidic dye and degree of acidophilicity of the basic dye), and the ratio and concentration of each dye.

‘Hikoshima-haruna’ (Brassica rapa var. narinosa) is a local traditional vegetable in Shimonoseki (Yamaguchi, Japan). The mature leaves are edible and much of the harvest is processed into pickles for consumption in the Shimonoseki area. To expand the consumption of ‘Hikoshima-haruna’, we verified the use of ‘Hikoshima-haruna’ powder in fish paste products as a part of the utilization research. We prepared heated gels (Kamaboko) mixed with 0-10% ‘Hikoshima-haruna’ powder and measured their breaking strength. The Kamaboko containing 1.0-4.0% powder exhibited a bright green color, preserving the characteristics of ‘Hikoshima-haruna’ as a plant with bright green leaves. Although the breaking strength of the two-step heating (30℃ for 30 min followed by 85℃ for 20 min) gels tended to decrease with increasing powder concentration, the 1.0% powder concentration exhibited a slightly greater breaking strength than the other concentrations. Therefore, when applying ‘Hikoshima-haruna’ powder to fish paste products, its use as Kamaboko at a powder concentration of 1.0% was considered appropriate.

Characteristics of the feeding behavior and relationship between the standard length (SL) and the size of scrape marks of ayu Plecoglossus altivelis altivelis were studied using 123 cultured specimens in aquaria. Feeding behavior was observed individually, 116 specimens (94%) have mouth laterality for feeding. Also, feeding behavior were found two types. The first was eating the algae directly from the shelter in 91 specimens (78%). The second left the shelter and ate the algae after changing direction back to the shelter (22%). One side of the lower jaw when feeding on the acrylic plate side was turned downward and the other side of the jaws was closing. On the scrape marks, 11 to 14 and 11 to 13 level lines were visible caused by the upper and lower jaws and the algae was not scraped between the upper and lower parts. The comb–like teeth groups are arranged as 13 to 14 rows and 12 to 14 rows on the upper and lower jaws, respectively. Therefore, it is suggested that they use almost all of the comb–like teeth groups except the back teeth row on the upper and lower jaws for feeding. The lengths of upper and lower jaws were found to have power regression with the SL, respectively. Also, the relationship between the SL and full width of the scrape marks (FWSM) was： FWSM = 0.3939SL^0.6767 (R^2= 0.8392, 64-212 mm SL).

We investigated the hemolymph CO_2 partial pressure (Pco_2) and bicarbonate concentration ([HCO_3^–]) of the acid–base balance of Mytilus coruscus under resting conditions. Hemolymph collected from the adductor muscle was subjected to the following measurements. Mean values for hemolymph pH and total CO_2 concentration for this state between 18℃ and 23℃ were 7.568-7.601 and 1.54-1.59 mM/L, respectively. Hemolymph Pco_2 and [HCO_3^–] were calculated using the hemolymph pKapp estimated using the relational expression with temperature. Hemolymph Pco_2 and [HCO_3^–] were 1.77-1.83 torr and 1.47-1.50 mM/L at 18℃ and 23℃. To verify Pco_2 and [HCO_3^–], the values were calculated using pKapp obtained by in vitro method (tonometry). Despite the different determination methods, no statistical difference in the obtained values of Pco_2 and [HCO_3^–] were observed. Non-bicarbonate buffer values (ꞵ_NB), which were calculated using the slope of the relational expression between pH and [HCO_3^–] in hemolymph, were 0.42 slykes at 18℃, and 0.54 slykes at 23℃. The hemolymph ꞵ_NB of M. coruscus was in the range of other bivalves, and the hemolymph buffer capacity of the non-bicarbonate buffer system would reflect the Mitilid species.

Identification of leukocytes on tissue sections is important to elucidate the mechanism of swim bladder lesions. To determine the best fixative solution for a koi carp swim bladder, the swim bladders were fixed in 10% formalin, Bouin's, MFAA and Davidson's solution. The swim bladders fixed in MFAA or Davidson's solution were severely detached and twisted, whereas those fixed in 10% formalin and Bouin's solution kept their external shape. However, the majority of the 10% formalin-fixed specimens showed detachment of the tunica interna from the tunica externa under the light microscope. Therefore, Bouin’s solution was determined to be the most suitable fixing solution for the swim bladder. Imprints (head kidney-touched slides glass were fixed with Bouin's solution) and tissue sections of head kidney fixed in Bouin’s solution were stained with Mayer’s hematoxylin and eosin (HE) and May-Grünwald·Giemsa (MGG), and the best staining method for leukocytes identification was investigated. In the HE-stained specimens, identification of leukocytes by staining was difficult. On the other hand, MGG-stained specimens could be identified by staining. Fixation with Bouin's solution and MGG staining was determined to be the most suitable method for leukocytes identification in the swim bladder.

Artur Pappenheim reported a poor description of the morphology of blood neutrophils from lamprey (Lampetra planeri； adult and ammocoetes) and hagfish (Myxine glutinosa) in Folia Haematologica (volume 8, 1909). Here, we inferred on the morphological characteristics of cyclostome neutrophils observed by Pappenheim based on his descriptions and our previous reports. He recognized neutrophilic leukocytes (mature neutrophils) in lamprey (adult and ammocoetes) and hagfish, and neutrophilic myelocytes (immature neutrophils) in ammocoetes and hagfish. This means the existence of specific granules and azure granules. However, the specific granules were considered as an inner layer (L0) of the striated granule (NG2), and the azure granules outer (L1) layer of the striated granule (NG2). The specific granules (=L0 of NG2) would probably have been stained with triacid (purple), acid dyes, and May-Grünwald·Giemsa (MGG； purple), but not with methylgreen-pyronine (MP). The azure granules (=L1 of NG1a) would also have stained purple with MGG, but negative with triacid, acidic dyes and MP.

The monocytes of lampreys [Lethenteron camtschaticum (adult), L. reissneri (adult), L. hattai (adult, ammocoetes)] were round or oval, low nucleus/cytoplasm ratio, and have striated (two-layered) granules (MoG). The MoG consisted of a basophilic inner layer (L0) and a chromophobic outer layer (L1). The L0 were positive for acid phosphatase, α-naphthyl acetate esterase, naphthol AS-D chloroacetate esterase and Sudan black B. Also, the L0 showed orthochromatic (blue) with toluidine blue. However, ꞵ-glucuronidase, α-naphthyl butyrate esterase and peroxidase were not detected in the monocytes, which were negative for periodic acid Schiff reaction, alcian blue, Sudan III, and oil red O. Kenji Kiyono reported the two types of monocytes (as blood histocytes), real and dubious monocytes, from the blood of hagfish Eptatretus burgeri. He observed both monocyte types in grown-up hagfish, but only real monocytes in undeveloped (details not stated) hagfish. His real monocytes in undeveloped hagfish were speculated as the monocytes of lamprey (mistaking the specimen), and the real monocytes in grown-up hagfish as poorly stained neutrophils. The dubious monocytes of Kiyono were considered as the real monocytes of hagfish.

The author has previously developed and published energy and resource flow models focusing on the post-collection process of marine debris. These models were designed to examine the technical and economic feasibility of establishing businesses with energy systems. One of the previous studies examined the economic feasibility of a microgrid system combining a styrene oil conversion device from drifted styrofoam and a cogeneration system (CGS). The current study focuses on the “biomass gasification furnace and methanol synthesis furnace” technology, which has a proven track record with woody biomass. If this methanol synthesis furnace could be applied to drifting marine debris, it would be an option for providing energy to coastal facilities. In this study, an energy flow model was developed that can easily calculate the energy flow of a methanol synthesis furnace, CGS, and fuel supply system using biomethanol obtained from coastal biomass such as marine debris. If only marine debris is taken into account, the amount of biomass will be insufficient. For this reason, discarded fish and food residues from fishing ports and fish processing plants were also evaluated. Furthermore, this biomethanol can be used together with waste cooking oil to synthesize biodiesel fuel (FAME), enabling various applications including marine fuel. Using this energy model, the potential for energy self-sufficiency for coastal fisheries facilities (fishing ports, fish processing plants, and fishing boats) was calculated. The calculation results show energy selfsufficiency as a function of changes in biomass volume. However, they also found it difficult to be self-sufficient in electricity, heat, and fuel at the same time. Additionally, an optimization model was developed to determine the optimal size of the CGS, demonstrating the potential to improve the energy self-sufficiency of coastal fishery facilities.