Occurrence and ultrastructure of mast cells in the hypothalamus of teleost fishes]

From 56 light-, fluorescence- and electronmicroscopically investigated brains of fishes mast cells could be found only in 4 cases. They were concentrated in the meninges of one pike (Esox licius) and in the meninges and at larger blood-vessels of the hypothalamus of 2 trouts (Salmo trutta fario). In the hypothalamus of a carp (Cyprinus carpio) an infiltration of mast cells was detectable in the meninges, at blood-vessels and capillaries, between neuronal and glial fibres and sub- and intraependymaly. Contrary to the pike the granules of the mast cells of the carp show changes, hinting at release of their content. Junctions between mast cells and capillary walls or ependymal cells are characterized by structures indicating an enhanced cytopempsis. The present results are compared with observations on mast cells in the brain and peritoneum of mammals.     

Polonium-210 in fishes from the Black Sea

The specific activity of naturally occurring radionuclide 210Po in main species of the Black Sea fishes and some their organs were used for the calculation of absorbed and equivalent dose rates. The values of the dose in investigated fish depend on their ecological belonging. Maximum values of equivalent dose rates for viscera and, first of all, liver exceed such for the whole body of fishes. But they are significantly lower than the dose rate limit recommended by IAEA for the protection of aquatic organisms from ionizing radiation.     

Vascularization and glomerular ultrastructure in the pig mesonephros

Summary Vascularization of the pig mesonephros was investigated in embryos 5–8 cm in length. Vascular injections with microfil were cleared and dissected; corrosion casts were studied under the scanning electron microscope (SEM). Perfusion-fixed tissue was used for SEM and transmission electron microscope (TEM) studies, including freeze-fracture specimens.The branches of one mesonephric artery carry up to 15 glomeruli. Several glomeruli occupy the same arterial branch, with very short afferent arterioles proper. The efferent vessels, frequently 2–5, leave the extensive vascular pole opposite the entering arteriole and split into peritubular capillaries radiating towards the superficial veins. These capillaries form vascular regions in the shape of flattened pyramids. Along its course, one nephron is supplied by vessels derived from 4–7 glomeruli. The nephrons have less vascular contact than in the definitive kidney.The ultrastructure of the single mesonephric vessels matches the metanephric counterparts. Epithelioid cells with renin granules are common in afferent arterioles, larger arteries, and efferent vessels. The lobulated glomeruli are up to 750 m long and flattened, showing the usual features of podocytes, mesangial cells, and an attenuated endothelium with fenestrations between 50 and 250 m. It partially retains its own basement membrane. There is no proximal mesangium.Supported by Deutsche Forschungsgemeinschaft.     

Diel activity of littoral and epipelagic teleost fishes in the Mediterranean Sea

Reviews in Fish Biology and Fisheries - Diel activity patterns are an important aspect of behavioural ecology, yet summarising works on diel activity patterns of fishes are lacking for several...     

Serotonin-like immunoreactivity in the epidermal club cells of teleost fishes

Summary The present immunocytochemical study concerns the distribution of serotonin in the epidermis of three species of teleost fish. Serotonin-like immunoreactivity was found in the club cells of Heteropneustes fossilis and Carapus acus but not in those from the sea eel Conger conger. This study is the first immunocytochemical identification of serotonin in the club cells of teleost epidermis. By comparing data from the literature (Zaccone et al. 1986, 1987, 1988) regarding the occurrence of serotonin and GRP/bombesin in the exocrine sacciform gland cells of piscine skin, it is worthy mentioning here that the serotonin contained in the club cells of the species studied may have the ability to affect the pheromonal or other possible functions of these cells. The presence of serotonin in these systems has been correlated with the capacity of the exocrine glands of fish skin to secrete, ectopically, amine messengers in contrast to those produced eutopically i.e. in the neuron-paraneuron system in some vertebrates (Fujita et al. 1988).     

Serotonin-like immunoreactivity in the epidermal club cells of teleost fishes

The present immunocytochemical study concerns the distribution of serotonin in the epidermis of three species of teleost fish. Serotonin-like immunoreactivity was found in the club cells of Heteropneustes fossilis and Carapus acus but not in those from the sea eel Conger conger. This study is the first immunocytochemical identification of serotonin in the club cells of teleost epidermis. By comparing data from the literature (Zaccone et al. 1986, 1987, 1988) regarding the occurrence of serotonin and GRP/bombesin in the exocrine sacciform gland cells of piscine skin, it is worthy mentioning here that the serotonin contained in the club cells of the species studied may have the ability to affect the pheromonal or other possible functions of these cells. The presence of serotonin in these systems has been correlated with the capacity of the exocrine glands of fish skin to secrete, ectopically, amine messengers in contrast to those produced eutopically i.e. in the neuron-paraneuron system in some vertebrates (Fujita et al. 1988).     

New data on Myxosporidia of Black Sea fishes

A new species of myxosporidians Alatospora solomoni from Trachurus mediterraneus is described. Two more species Sphaeromyxa balbiani from Blennius sanguinolentus and Ortholinea divergens from Symphodus roissali are found in the Black Sea for the first time.     

The pineal organ of teleost fishes

The pineal organ of teleost fish is a directly photosensory organ that contains photoreceptor cells similar to those of the retina. It conveys photoperiod information to the brain via neural pathways and by release of indoleamines, primarily melatonin, into the circulation. The photoreceptor cells respond to changes in ambient illumination with a gradual modulation of neurotransmission to second-order neurons that innervate various brain centres, and by modulation of indoleamine synthesis. Melatonin is produced rhythmically, and melatonin synthesis may be regulated either directly by ambient photoperiod, or by an endogenous circadian oscillator that is entrained by the photoperiod. During natural conditions, melatonin is produced at highest levels during the night. Although the pineal organ undoubtedly influences a variety of physiological parameters, as assessed by experimental removal of the pineal organ and/or administration of exogenous indoleamines, its role in any physiological situation is not clear cut. The effects of any interference with pineal functions appear to vary with the time of year and experimental photothermal regimes. There are strong indications that the pineal organ is one component in a central neural system that constitutes the photoperiod-responding system of the animal, i.e. the system that is responsible for correct timing of daily and seasonal physiological rhythms. It is important to envisage the pineal organ as a part of this system; it interacts with other photosensory structures (the retina, possibly extraretinal non-pineal photoreceptors) and circadian rhythm generators     

On the occurrence of merkel cells in the epidermis of teleost fishes

Summary The ultrastructure of a differentiated cell type in the epidermis of two species of teleost fish, Ictalurus melas and Phoxinus phoxinus, is described. This cell type has a synaptic association with nerve fibres, microvillus-like peripheral processes, and membrane-bounded inclusions, which together are the diagnostic features of the Merkel cells of tetrapod vertebrates. Other cytoplasmic features are shared with the epithelial cells. The appearance of the membrane-bounded granules depends on the fixative used; after fixation with glutaraldehyde the granules are of a size and electron-density comparable to that found in tetrapod Merkel cells, but after fixing in osmium tetroxide the granules are inconspicuous.Our thanks are due to Mr. A.C. Wheeler of the British Museum (Natural History) for help with the identification of the species of Ictalurus, and to Mr. E. Perry for technical assistance. One author (EBL) was supported by a SRC research studentship     

Hydration of oocytes in teleost fishes

Data on the hydration of oocytes in teleost fishes during maturation stimulated by gonadotropic or steroid hormones in vivo and in vitro are reviewed. The cause of hydration, its dynamics, and some mechanisms ensuring uptake of water and ions by the oocyte are considered.     

Morphology of the hypothalamus in advanced teleost fishes

A remarkable structure in the hypothalamus of brachiopterygian and actinopterygian fishes consists of the inferior lobes, nucleus rotundus and torus lateralis. Optic connections are predominant among a variety of fibre paths.  

ZUSAMM ENFASSUNG

Actinopterygier (und Brachiopterygier) besitzen im Hypothalamus eine spezielle, oft beachtlich ausgeprägte Region; diese besteht aus den Lobi inferiores, dem Nucleus rotundus hypothalami und dem Torus lateralis. Unter den reichhaltigen Faserverbindungen haben die meisten optischen Charakter.     

Duplicated cytoglobin genes in teleost fishes

Cytoglobin is a recently discovered myoglobin-related O2-binding protein of vertebrates with uncertain function. It occurs as single-copy gene in mammals. Here, we demonstrate the presence of two paralogous cytoglobin genes (Cygb-1 and Cygb-2) in the teleost fishes Danio rerio, Oryzias latipes, Tetraodon nigroviridis, and Takifugu rubripes. The globin-typical introns at positions B12.2 and G7.0 are conserved in both genes, whereas the C-terminal exon found in mammalian cytoglobin is absent in the fish genes. Phylogenetic analyses show that the two cytoglobin genes diverged early in teleost evolution. This is confirmed by gene synteny analyses, which suggest a large-scale duplication event. Although both cytoglobin genes are highly conserved and have evolved under purifying selection, substitution rates are significantly higher in Cygb-1 than in Cygb-2. Similar to their mammalian ortholog, both fish cytoglobins are expressed in a broad range of tissues. However, Cygb-2 is more than 250-fold stronger expressed in neuronal tissues, suggesting a subfunctionalization of the two cytoglobin paralogs after gene duplication.     

The behaviour and neuro-anatomy of some developing teleost fishes

This investigation relates the ontogenetic development of observable behaviour to theunderlying co-ordinating and conducting systems in telecosts. It is based on a study of the eggs of seven species, fertilized artificially. The onset of behaviour was marked by the heart beat; this started in separate regions which became connected and developed a rhythm. It was followed by non-rhythmic contractions of the body musculature, the resulting flexures becoming alternating or serial and cephalo-caudal. Movements of the pectoral fins, jaws and opercula were first performed as part of the axial musculature of the body; later they became independent and co-ordinated. There was an increasing tendency towards stability and efficiency in the development of response to tactile, chemical, vibrational, feeding, rotational and light stimulation.     

Composition of the milt of some teleost fishes

The milt composition of six freshwater teleosts was studied, and the measured parameters showed clear specific differences between species. The highest spermatocrits and sperm densities were observed in perch, Perc afluviatilis , and burbot, Lota lota , and the lowest in rainbow trout, Salmo gairdneri , and whitefish, Coregonus lavaretus . Fructose concentrations in the seminal plasma were small compared to mammalian values. The glucose concentrations in the seminal plasma were five times higher than those of fructose, and higher in landlocked salmon and rainbow trout than in the other species. The citric acid concentration of all species except whitefish showed a significantly positive correlation to either spermatocrit or sperm density. The role of citric acid in the seminal plasma of fishes was also assumed to be important. The glycerol concentration in the seminal plasma was comparatively high, and highest in whitefish. This was assumed to be related to the high applicability value of glycerol as a cryoprotective agent for whitefish sperm. The high glycerol concentration was also assumed to be related to the lipolytic capacity of the testis in the studied species.