Ordinary Fish Research Articles

Granulometric Parameters Determination of the Caviar-Hawk Complex as a Dispersed System for the Fractionated Lecithin Technology Implementation

For the functional food product manufacture a man can use secondary raw materials, the caviar–hawk complex, particularly. The main technological operations in the lecithin–containing substances production include its extraction processes from the initial caviar raw materials and raffinate obtained after the first stage of selective extraction. The operation mechanism requires a comprehensive study of the granulometric composition of raw materials. It was the research aim. A man assessed the granulometric composition of the caviar–hawk complex by visual analysis of its micrographs. The dispersion analysis demonstrated that the studied raw materials of all the analyzed species ranked as a small caviar, which is typical for ordinary fish objects. The thesis contains schematic elementary particle illustrations of fresh and dry caviar of carp, catfish, pike perch; presents dispersed equivalent sizes and shrinkage values of the research objects. Preliminary caviar grinding during conservation is impractical. Although this procedure leads to the mass transfer process intensification, since a man provides the analyzed caviar for using not only to obtain fractionated lecithin and protein texturate, but also as raw materials for enterprises. Staged experiments confirmed that an increase in the mass transfer rate, including the process of extracting target components from crushed caviar raw materials, was insignificant compared with the cost of additional grinding and loss of native caviar properties. The caviar under study is a finely dispersed product. Its additional grinding gives an insignificant effect.

НАУКОВО-ПРАКТИЧНИЙ АНАЛІЗ СТАНУ ПРИРОДНОЇ КОРМОВОЇ БАЗИ СТАВІВ ПІВЛНЯ УКРАЇНИ НА ФОНІ ТРАНСФОРМАЦІЙ АБІОТИЧНИХ ТА БІОТИЧНИХ ЧИННИКІВ

Conducted research on the basis of the breeding ponds of the Kherson production and experimental plant for breeding of the ordinary fish indicate atypical dynamics of the development of the components of the natural feed base. Such aspects form a low fod

Functional relation of agouti signaling proteins (ASIPs) to pigmentation and color change in the starry flounder, Platichthys stellatus

We investigated the involvement of agouti-signaling proteins (ASIPs) in morphological pigmentation and physiological color change in flatfishes. We isolated ASIP1 and 2 mRNAs from the skin of starry flounder (Platichthys stellatus), and compared their amino acid (aa) structures to those of other animals. Then, we examined the mRNA expression levels of two ASIPs (Sf-ASIPs) in the pigmented ocular body and in the unpigmented blind body, as well as in the ordinary skin and in albino skin, in flatfishes. To investigate the role of Sf-ASIPs in physiological color change (color camouflage), we compared the expression of the two genes in two background colors (dark-green and white). Sf-ASIP1 cDNA had a 375-bp open reading frame (ORF) that encoded a protein consisting of 125 aa residues, and Sf-ASIP2 cDNA had a 402-bp ORF that encoded a protein consisting of 132 aa residues. RT-PCR revealed that the strongest Sf-ASIP1 and Sf-ASIP2 expression levels were observed in the eye and blind-skin, respectively. In Sf-ASIP1, the gene expression did not differ between the ocular-side skin and blind-side skin, nor between ordinary skin and abnormal skin of the fish. However, in Sf-ASIP2, the expression level was significantly higher in blind-side skin, compared to ocular-side skin, suggesting that the ASIP2 gene is related to the countershading body pigment pattern of the fish. In addition, the Sf-ASIP2 gene expression level was lower in the pigmented spot regions than in the unpigmented spot regions of the malpigmented pseudo-albino skins on the ocular side, implying that ASIP2 is responsible for the ocular-side pseudo-albino. Additionally, ASIP2 gene expression in the blind-side skin of ordinary fish was enhanced by a white tank, implying that a bright background color could inhibit hypermelanosis in the blind-side skin of cultured flounder by increasing the activity of the Sf-ASIP2 gene. However, we did not find any relationship of ASIPs with camouflage color changes. In conclusion, the ASIP2 gene is related to the morphological pigmentation (countershading and malpigmentation) of the skin in starry flounder, but not with physiological color changes (color camouflage) in the ocular-side skin.

From catch to plate

From catch to plate

Фізіолого-біохімічні аспекти адаптаційно-компенсаторних процесів організму гідробіонтів під впливом технологічних чинників

Purpose. To study the functional status in the body of the common carp Cyprinus carpio (Linnaeus, 1758) after the addition of biologically active substances in feed composition as an adaptogene and corrector of metabolic processes including the antioxidant system, catalase activity in carp body. Methodology. The experimental part of the study was performed at the laboratory of the Scientific and Research Laboratory “Aquaculture Perspectives”, Scientific and Research Laboratory of “S. Pentelyuk Physiological and Biochemical Studies”, Scientific and Research Laboratory of Ecological and Chemical Analysis and Water Monitoring of the State Education Institution “Kherson State Agrarian and Economical University” and at the laboratory of the “Kherson Production and Experimental Hatchery of Ordinary Fish Breeding”. The duration of the experimental part was 30 days. During this period, visual observation of the fish was carried out, biological material was collected for the study in accordance with the current methods in fish farming. Cytological studies of blood were carried out on smears using Micromed MDC-500-5MP eyepiece camera. ThermoMix equipment was used to transport biological material to the laboratory. The hydrochemical parameters in tanks of the recirculating aquaculture system (RAS) were investigated by express methods (tests) with the corresponding recording of results in the work journal. The reaction and ethology of the common carp Cyprinus carpio to the light was carried out using digital equipment and a LDT test. Findings. The obtained results demonstrated the positive effect of the feed factor as an adaptogene and growth stimulator on the redistribution of metabolic energy in the carp body, which in turn had a stimulating effect on the development rate and improved the general functional status of the fish body. The paper presents the results of morpho-functional, biochemical parameters of carp blood in ontogenesis when grown in recirculating aquaculture systems against the background of the application of elements to improve technological aspects while improving the adaptive capabilities of the fish body. It was found that the feed factor, when introduced into the general economic ration, promoted an increase in the average carp body weight in the experimental group, improved the parameters of homeostatic equilibrium in comparison with fish in the control group. Positive results of a scientific and experimental study on the use of the additive as an adaptogene were obtained; it was studied with the aim of activating protective mechanisms, metabolic processes of aquatic organisms under constant or systematic exposure to stress factors of a technological nature. The study showed that the body weight, yield, total number of erythrocytes, hemoglobin content, total protein, and the level of catalase activity in the experimental groups of fish exceeded these parameters in the control group. The results obtained allowed noting the activation of the antioxidant system, the restructuring of physiological and biochemical processes, mobilization systems in the carp body in the experimental group. Originality. We found a correcting effect of the feed factor on metabolic processes, the adaptive capacity of the fish organism, as well as an increase in the resistance of the body as a whole. After implementing the technological scheme of cultivation of a feed factor of natural origin as an adaptogene against the background of the influence of technological stress factors, we found a correlation between the morpho-functional, biochemical parameters of carp blood and stress markers. Addition of biologically active substances of natural origin with a pronounced adaptive and correcting physiological and biochemical parameters into the general diet of carp improved the adaptive capacity. The antioxidant system was activated against the background of the action of technological factors. Practical value. The results of scientific and experimental studies of the functional status of carp body under the influence of technological factors were presented. Parameters of the development of carp in ontogenesis when growing in recirculating aquaculture systems against the background of the introduction of multilevel elements to improve technological aspects were studied. The results demonstrated the positive effect of biologically active substances invlufrf in the feed mixture, in particular, activation of the growth rate, increase in body weight, and yield. Key words: functional state of the carp body, adaptive and compensatory parameters, development rate, recirculation systems, technological factors.

СОСТОЯНИЕ РЫБОЛОВСТВА В ЮЖНОМ РАЙОНЕ ВОЛГО-КАСПИЙСКОГО РЫБОХОЗЯЙСТВЕННОГО БАССЕЙНА

The paper presents the generalized materials on the current state of fisheries in the Northern part of the Caspian Sea (southern region of the Volga-Caspian fisheries basin). It is shown that catches in the North-Western and Tersk-Caspian subdistricts varied in the opposite way: an increase in production in one subdistrict was accompanied by a decrease in the other. The decreasing or increasing catches is due to semi-anadromous (roach, brim, zander, carp) and freshwaterfish species (cat-fish, pike-perch, small size ordinary fish). There have been found the significant relationships between the size of catches in the North-Western and Tersk-Caspian subdistricts with the annual runoff and the volume of spring flooding of the Volga river, which allows to conclude that fish resources are redistributed between these regions depending on the natural conditions of 
 a particular year. In order to more fully develop the fish resources of the southern region of the Volga-Caspian fisheries basin, it is recommended to abandon the division of quotas into parts for the North-Western and Tersk-Caspian subdistricts and to allow the fishing organizations to work at the expense of the total allowable catch

Технологічні аспекти використання інтенсивних технологій при товарному вирощуванні коропа (Cyprinus carpio (Linnaeus, 1758))

Purpose. To study the effect of the feed factor on the functional state of the carp body (Cyprinus carpio L.) under the conditions of growing in a model recirculation system of complex purpose with the use of intensive technologies. Methodology. The experimental part of the study was performed at the laboratory of the Scientific and Research Lab “Aquaculture Perspectives”, Scientific and Research Laboratory of “Physiological and Biochemical Studies named after S. Pentelyuk”, Scientific and Research Laboratory of Ecological and Chemical Analysis and Water Monitoring of the State Education Institution “Kherson State Agrarian and Economical University” and at the laboratory of the “Kherson Production and Experimental Hatchery of Ordinary Fish Breeding”. Carp growing was carried out in the model installation of tanks recirculation type with using intensive technologies, alternative energy sources, method of gas-discharge visualization. During the experiment following was performed: clinical examination of fish, control of growth rate and weight gain, survival rate, physiological state and morpho-functional parameters of blood in accordance with conventional methods. Findings. The general functional state of the organism of the common carp Cyprinus carpio L. in ontogenesis was investigated against the background of activation of adaptive-compensatory mechanisms, metabolic processes under the influence of the food factor under rearing conditions in a model system for complex purposes in aquaculture. Positive results of analysis of morpho-functional, biochemical parameters of carp blood were obtained when feeding with a feed mixture from natural fodder and biologically active substances. The degree of influence of the fodder factor as a corrector of metabolic processes in the carp organism when growing the marketable mass has been studied. Originality. The conducted analysis of gas-discharge visualization of static GDV-gram parameters of optoelectronic emission of young-of-the-year carp showed differences in functional activity in the organism of fish from the experimental group in relation to the control group, which was also substantiated and argumentative by the parameters of carp blood and development rate. Practical value. The proposed method of feeding carp in the recirculation system contributes to the correction of metabolic processes in their body, which makes it possible to reduce the cost through the use of natural feed, the cultivation of which is introduced into the recirculation system, the formation of a mixture of our own production, using the GDV-method diagnostics of objects and energy-saving elements in technological map. Key words: carp, vitality, feeding factor, fish stocking, modular system, intensive technology.

АНАЛИЗ СОСТОЯНИЯ ЗАПАСОВ ОСНОВНЫХ ПРОМЫСЛОВЫХ РЫБ КУЙБЫШЕВСКОГО ВОДОХРАНИЛИЩА ЗА ПЕРИОД 2000–2018 ГГ. И ЭФФЕКТИВНОСТЬ ИХ ИСПОЛЬЗОВАНИЯ ПРОМЫСЛОМ

The article presents a review of the main commercial fish stocks of the Kuibyshev Reservoir based on the long-term research data (2000–2019). The Kuibyshev Reservoir is the leading fishery reservoir in the Republic of Tatarstan, Mari El, Chuvashia, Ulyanovsk and Samara Re-gions. There have been given the data of regular observing species, sex, size-weight and age composition of fish, their reproduction efficiency, distribution, abundance and reproduction of aquatic biological resources, their habitat, as well as control over their fishing and conservation. The analysis of the influence of environmental factors (level and temperature regimes) and fishing on the fish stocks formation is presented. Based on the presented materials, there have been shown the data about the stocks of the main commercial fish species of the Kuibyshev Reservoir (bream, zander, pike, carp, catfish, sterlet) and of the small-sized ordinary fish stocks, the optimal development of which will bring the catches up to 10 thousand tons and more. It has been inferred that for rational fishing in the reservoir, it is necessary to develop a strategy for the integrated effective development of biological resources of the reservoir on an ecosystem basis for better use of the bioproduction capabilities of its biological resources.

Pelatihan Dan Penampingan Pengolahan Rumput Laut Dan Hasil Laut Menjadi Aneka Kuliner Pada Nelayan di Desa Labuhan Haji Kabupaten Lombok Timur

This community service aims to improve the welfare of the community, especially in the coastal areas of Labuhan Hajj village who work as fishermen, as an area that is included in the category of underprivileged areas, this area needs touches that can improve the welfare of its people by optimizing the potential that exists in the village. namely seaweed and its sea products which are quite large. This century, named Kobe Molek, this time, how to cultivate the existing potential to make various culinary delights that can be liked by many people with various attractive forms, affordable prices and can be found in many places. One of the potentials of this area is processing sea rumpu into snacks that they like, having a distinctive taste, such as seaweed lunkhead, seaweed pilus cake, grass grass and so on, while ordinary fish is made of long-lasting shredded with a tantalizing taste and pamper the tongue of culinary lovers . as well as the form of packaging that makes consumers' eyes fixed and of course at a price that does not drain a lot of pockets. The village's huge potential requires high creativity so that it can be accepted by the community and able to compete among other entrepreneurs. This community creativity needs to be supported by training such as product processing, packaging and marketing and what is no less important is financial management. This training is carried out in coordination with related agencies such as the social service, the trade office to be able to provide guidance and direction as well as provide assistance starting from training in production, packaging and sales. The container in the community called Kobe Molek is a container for fishermen's wives who are concerned about cultivating the potential of the village, namely seaweed and its fish products that process it into culinary according to the wishes of consumers. This product is marketed around the village and trying to be marketed through social media, such as Facebook, Instagram, whatshapp, with the hope that the products can be sold more widely and participate in exhibitions conducted by related agencies.

Different resistance potential to reovirus in grass carp (Ctenopharyngodon idella) populations and their immune characteristics

Our aim was to verify whether genes in the coagulation complement and cytokine interaction pathways are crucial to the resistance to grass carp hemorrhagic disease in grass carps (Ctenopharyngodon idella). To evaluate this, we acquired male grass carps with grass carp reovirus (GCRV) resistance, F1 generation, ordinary male fish, control F1 progenies (hybridized ordinary fish), and barbel chub (Squaliobarbus curriculus) as a positive control. We compared the expression variation of 13 immune factors in different tissues using real-time fluorescent quantitative PCR. Our results showed that the expression of the transforming growth factor-β3, nerve growth factor receptor, coagulation factor D, chemokine receptor XCR1, profibrinolysin, γ-globulin of complement component 1, complement component 2, and complement component 5 in the different tissues of the barbel chub were significantly higher than those in the grass carps populations under normal conditions. Except for a limited number of genes, their expression exhibited significant differences. There was no significant difference in these genes among grass carp populations with different GCRV resistance. These results indicate that the high gene expression in the coagulation complement and cytokine interaction pathways may be the main reason for the strong resistance of barbel chub to GCRV. However, high gene expression was not a factor affecting GCRV resistance between grass carp populations.

ОПРЕДЕЛЕНИЕ ВЛИЯНИЯ ДИНАМИЧЕСКИХ ХАРАКТЕРИСТИК СМЕСИТЕЛЕЙ НА СТРУКТУРНО-МЕХАНИЧЕСКИЕ СВОЙСТВА РЫБНЫХ КУЛИНАРНЫХ ФАРШЕЙ

The article presents the empirical results of estimating the dependence of viscoplastic properties of the minced ordinary fish raw materials from the kinematic and dynamic characteristics of mechanisms applied in the course of processing. When mixed in mechanical mixers, minced fish is subjected to shear and normal effects of rotating parts that create a complex three-dimensional flow. Optimization of the process of obtaining viscous-plastic culinary products depends on the dynamics of movement of the studied objects and the influence of working parts of various configurations. To establish the relationship between the duration of mixing, the angular speed of rotation of the working part of the horizontal mixer and general structural and mechanical properties of minced fish, there were carried out experimental studies using various types of mixer working parts: conveyer, screw and blade. The influence of the rotation speed of the mixer working part on the change in the rheological characteristics of the investigated raw materials has been confirmed. Specific energy costs should be emphasized as one of the main criteria for evaluating the performance of the supporting equipment. This parameter depends on redistribution of components during their mixing, changes in the structural and mechanical properties of minced fish and structural characteristics of the working parts. It has been stated that the lowest energy consumption and optimal mode for viscoplastic mixed mass can be achieved by using blades with an inclination angle to the axis of rotation = 20–30° and a humidity increase of mixed mass up to 0.7–0.8 kg/kg.

Research on the drag reduction property of puffer (Takifugu flavidus) spinal nonsmooth structure surface.

Puffers show good drag reduction performance during migration. It is worth noting that spines which are different from ordinary fish scales are densely distributed on the puffer skin. Here, the special morphological structure of puffer spines was observed using microscopy techniques, accurate contour models were established based on image processing techniques and curve fitting, then feature sizes were obtained. Based on the results, the nonsmooth surface was established by orthogonal test to simulate the flow field. In addition, the influence of spinal structure on boundary layer flow field and the drag reduction property of nonsmooth surface were further analyzed. The nonsmooth surface formed by spinal structure elements can effectively reduce the wall shear stress and Reynolds stress, and there was a special "climbing vortex" phenomenon, so as to reduce the surface viscous friction resistance and achieve drag reduction. Compared with the smooth surface, the drag reduction rate of the nonsmooth surface was 12.94% when the inflow velocity was 5 m/s, which revealed and verified the drag reduction performance of the spines of puffer skin. The results lay a foundation for further research and optimization of drag reduction ability of nonsmooth surface of bionic spines. HIGHLIGHTS: The contour of the spinous process was accurately reflected by the Fourier function. The spines of puffer skin have good drag reduction effect. There was a special "climbing vortex" phenomenon to explain the drag reduction property.

РАЗРАБОТКА РАЦИОНАЛЬНЫХ РЕЖИМОВ СУШКИ ЖЕЛАТИНОВОГО БУЛЬОНА ИЗ ОТХОДОВ ПЕРЕРАБОТКИ РЫБЫ

The article presents the research of kinetics and intensity of convective-radiation foam drying of gelatin broth from ordinary fish processing wastes in the Astrakhan region. Approximating dependences of dry gelatin removal from the unit area of the working surface per unit time on the varied factors have been obtained. The rational modes of the process, in which the maximum specific removal of the dry product is achieved, have been determined. It has been found that using only radiation energy supply makes the process of foaming gelatin broth difficult due to the uncontrolled sharp increase of temperature of the product and, as a consequence, the subsequent melting and destruction of the foam. Putting radiation energy supply into the process of convective foam drying of the gelatinized broth under rational conditions increases the specific productivity of the process by three times.

ИССЛЕДОВАНИЕ ИНТЕНСИВНОСТИ КОНВЕКТИВНОЙ ПЕНОСУШКИ ЖЕЛАТИНОВОГО БУЛЬОНА ИЗ ОТХОДОВ ПЕРЕРАБОТКИ РЫБ ЧАСТИКОВЫХ ПОРОД

The intensity of the process of convective foam drying of gelatinized broth prepared from ordinary fish waste in the Astrakhan region was studied experimentally. The product was dried in a foamed state in a layer with a unilateral convective energy supply, as well as in the foamed and natural state in the form of round bars with a uniform convective energy supply. The ranges of variation of the main factors influencing the process were selected and substantiated, and their effect on the objective function (yield of dry gelatin per unit time per unit area) was analyzed. Approximating dependencies of the objective function on the main factors are obtained. According to the results of the research, application of a uniform convective energy supply in the course of drying gelatin broth under rational regimes allows to increase specific productivity of the process by 1.5 times, compared to drying with a unilateral energy supply, and to shorten the drying time from 4.2 to 2.3 hours. In this case, foaming the product results in more than a twofold increase in productivity while reducing the drying time by almost twice. The rational regimes for carrying out the process of convective drying of gelatinized broth in producing dry gelatin are determined: convective drying of the gelatinized broth should be conducted in a foamed state, with a uniform power supply, in the form of bars with circular cross section under the following conditions: initial diameter dn of a round bar = 0.004 m, initial moisture wn of product = 75%, flow rate v of the drying agent not less than 4.5 m/s, temperature T of the drying agent = 293-295 K. The indicated regimes provide the highest specific yield of the dry product G = 0.33 kg/(m2·h) and are recommended for practical use in order to increase the intensity of the process while maintaining the quality of dry gelatin.

Characterizing PBDEs in fish, poultry, and pig feeds manufactured in China.

A total of 53 feeds from 23 brands for four types of animals, i.e., fish, chicken, duck, and pig, as well as six types of raw materials, were bought from Guangxi, Hubei, Anhui, and Guangdong provinces in China and analyzed for polybrominated diphenyl ethers (PBDEs). The raw materials including super fish meal, ordinary fish meal, poultry ore, soybean, stone powder, and rapeseed were selected because they were added to all the animal feeds manufactured. The occurrence of PBDEs was ubiquitous in the feeds and raw materials, with BDE-209 as the most abundant congener. The average concentration of ∑8PBDE was 1.1 and 0.44ngg-1 dry weight in feeds (range 0.25-5.7) and raw materials (range 0.27-0.84), respectively. No statistically significant differences in ∑8PBDE concentrations were observed among the four groups of animal feeds. Feeds from Yangzhiyuan Brand (n = 11) contained statistically (p < 0.01) lower ∑8PBDE concentrations than all other brands except for Baoshun Brand. Chicken was selected as a representative animal to assess health risk for human exposure to PBDEs via the consumption of chicken raised by the feeds under investigation. Hazard quotients based on per-capita consumption of chicken were all below 1, indicating low potential risk to humans consuming chicken raised with the feeds. Graphical abstract.

Scientific foundations of fish-consumption advice for pregnant women: Epidemiological evidence, benefit-risk modeling, and an integrated approach

BackgroundPregnant women need fish consumption advice that increases seafood intake and simultaneously reduces methylmercury (MeHg) exposure. Two disciplines, epidemiology and benefit-risk modeling, can support such advice. Some current models suggest that fish consumption during pregnancy has only net beneficial effects. In contrast, many recent epidemiological studies have associated adverse effects on cognitive development with ordinary fish intake and MeHg doses routinely encountered by up to one in six US women of childbearing age. Proposed federal fish-consumption advice is based solely on a benefit-risk model. A more complete assessment integrating both types of evidence is needed. Objectives and methodsThe goal of this paper is to use a model to rank seafood items by their relative benefits and risks, producing consumer seafood choice recommendations that are also consistent with epidemiological observations. Recent epidemiological studies and benefit-risk models are reviewed, and model results are compared with one another and with epidemiological observations to identify commonalities that support inter-calibration. Results and conclusionsBoth approaches quantify MeHg doses at which harm slightly exceeds benefit. A model from the US Food and Drug Administration (FDA) predicts adverse effects at fish intakes containing, on average, more than 16 times the the US Reference Dose (RfD) for MeHg. Epidemiological results indicate that the RfD itself approximates a minimal adverse dose. This conceptual similarity allows FDA's model to be calibrated with the epidemiological results to generate fish intake recommendations that both the model and the epidemiology suggest should have substantially positive public health impacts.

The Functional Relevance of Prepro-melanin Concentrating Hormone (pMCH) to Skin Color Change, Blind-side Malpigmentation and Feeding of Oliver Flounder Paralichthys olivaceus

To assess the functional structure of prepro-melanin-concentrating hormone (pMCH), we isolated and cloned pMCH (of-pMCH) mRNA from the brain of the olive flounder, Paralichthys olivaceus, and compared its amino acid sequence with those from other animals. In addition, to examine whether activation of the brain of-pMCH gene is influenced by background color, density, and feeding, we compared pMCH mRNA activities against different background colors (bright and dark) and at different densities (100% PCA and 200% PCA). To examine whether the pMCH gene is related with malpigmentation of blind-side skin and appetite, we compared pMCH gene expression between ordinary and hypermelanic flounders, and between feeding and fasting flounders. The of-pMCH cDNA was 405 bp in the open reading frame [ORF] and encoded a protein of 135 amino acids; MCH was 51 bp in length and encoded a protein of 17 amino acids. An obvious single band of the expected size was obtained from the brain and pituitary by RT-PCR. In addition, of-pMCH gene activity was significantly higher in the bright background only at low density (< 100% PCA) making the ocular skin of fish whitening, and in ordinary fish. However, the gene activity was significantly decreased in dark background, at high density (>200% PCA), and in hypermelano fish. These results suggest that skin whitening camouflage of the flounder is induced by high MCH gene activity, and the density disturbs the function of background color in the physiological color change. Moreover, our data suggest that a low level of MCH gene activity may be related to malpigmentation of the blind-side skin. In feeding, although pMCH gene activity was significantly increased by feeding in the white background, the pMCH gene activity in the dark background was not influenced by feeding, indicating that the MCH gene activity increased by feeding can be offset by dark background color, or is unaffected by appetite. In conclusion, this study showed that MCH gene expression is related to ocular-skin whitening camouflage and blind-skin hypermelanosis, and is influenced by background color and density.

Relevance of environmental factors and physiological pigment hormones to blind-side hypermelanosis in the cultured flounder, Paralichthys olivaceus

To identify exogenous and endogenous factors that directly affect hypermelanosis on the blind side of the olive flounder, Paralichthys olivaceus, we examined the potential relationships between blind-side hypermelanosis and three environmental factors (density, background color, and burrowing substratum) and four endocrine genes (prepro-melanin concentrating hormone [pMCH] and prepro-proopiomelanocortins [POMC]-I, II, and III) involved in physiological color change, using juveniles reared at high density in an artificial facility. We recorded the ratios of pigmented blind-side area and ambicolored fish among experimental groups, and compared pMCH and POMC mRNA activities between ordinary and hypermelanic groups. The results indicated that the density and the background color were not critical factors for blind-side hypermelanosis; however, these unnatural conditions (high density and dark background) accelerated the rate of hyperpigmentation. In addition, the presence of burrowing substratum on the bottom of the tank was effective for preventing blind-side hypermelanosis in developing olive flounders. In addition, expression of MCH mRNA was significantly lower in hypermelanic fish than in ordinary fish, but the levels of two POMC (POMC-I and II) mRNAs were higher in hypermelanic fish than in ordinary fish, suggesting that MCH inhibits blind-side hypermelanosis, but POMCs encourage malpigmentation. In conclusion, rearing density and background color are minor causes of the development of blind-side hypermelanosis in olive flounders, but the absence of a burrowing substratum, MCH inactivation, and activation of POMCs (I and II) are main factors involved in the development of hypermelanosis.

FISH CONTROL THEIR ROTATION

Michael Triantafyllou, Dick Yue and colleagues at the Massachusetts Institute of Technology have been studying mechanical and computational models of swimming fish for the last 10 years. With Qiang Zhu, in the Journal of Fluid Mechanics in October, they described how their 3D model based on simplifications of the Navier-Stokes equation shows how swimming fish use their tails to re-capture energy shed by their bodies. The team has also compared their 3D model with two classic 2D theoretical fish models to see how well the 2D models describe how tuna fish and danios swim.First, Zhu and colleagues use their simulations to show how tuna fish and danios exploit `vorticity control' to improve their thrust or their swimming efficiency. When a fish's tail moves back and forth, it causes rotation in the water, called vorticity. For most fishes, the body also moves back and forth and also produces vorticity. The simulations show that when the body vorticity hits the tail vorticity, they interact, either strengthening or weakening each other. If the body vorticity is clockwise when the tail vorticity is also clockwise, they strengthen each other, increasing the total vorticity and thrust. However, if the rotations are in opposite directions, the vortices weaken each other, reducing the amount of energy in the wake. Ideally all of the energy would produce forward motion, rather than a wake where the energy is mostly wasted. So reducing the energy in the wake when the vortices interact increases the fish's swimming efficiency. Zhu's calculations show that tunas improve their thrust while danios improve their swimming efficiency, both through vorticity control.Zhu's model also addresses a problem in simple models of swimming fish: are fish very tall or very long? Two widely used theories from the 1960s analyse a 2D horizontal slice through a swimming fish. The difficulty with analysing a 3D fish in two dimensions is that it requires assumptions about how the fluid flows near the top and bottom of the fish. One 2D theory suggests that if fish are very tall, most of the fluid flows longitudinally down the fish's body. An alternative theory assumes that fish are long and short, and almost all fluid moves laterally and wraps over the top and bottom. Zhu's calculations show that flow around the tuna is largely longitudinal, as if the fish were tall,but that flow around the danio is both longitudinal and lateral, like a combination of the two theories. The difference lies in the different swimming motions. Tunas move their bodies side-to-side relatively little, but danios move side-to-side much more, which forces more fluid laterally.In the end, it seems that tunas can be modelled by one of the earlier 2D models, but neither simplified theory captures the danio's mode of swimming. Since danios are much more similar to an average fish than tunas, Zhu's simulations suggest that 2D theories might not describe how ordinary fish may re-use energy to boost their efficiency.

Gross Anatomy and Histology of the Hook and Skin of Forehead Brooding Male Nurseryfish, Kurtus Gulliveri, From Northern Australia

Mature males of nurseryfish have a hook on their head to which the eggs become attached and are carried like a bunch of grapes. This paper examines the anatomy and histology of the hook. The osteological basis of the hook is shown to be a modification of the supraoccipital crest of the skull covered by typical teleost skin. The integument in the cleft of the hook, where the eggs are attached, is considerably different from ordinary fish skin. The stratified epidermis is devoid of secretory mucus and neurosensory cells and is folded into crypts that extend deeply into the dermis. This may be a specialization that facilitates adhesion of the sticky egg mass. Field observations show that this cleft area of the hook is edematous, and histology confirms that the area is highly vascularized. We speculate that this may facilitate gas exchange and/or nutrition between the male and the egg mass, but this can only be confirmed by physiological experiments with ‘pregnant males’ in captivity. Engorgement with blood in the highly vascularised dermis of the hook may help hold the egg mass in place.