Locomotor activity of river lamprey Lampetra fluviatilis (L.) during the spawning season

At high latitudes (62–64°N) the river lamprey Lampetra fluviatilis (L.) is shown to have a 24-hr locomotor activity during its spawning period just before midsummer. By keeping lampreys in cold water, the spawning was delayed about one month. Analysis of event recorder graphs indicate that the 24-hr activity is caused by addition of diurnal spawning activity to the basic nocturnal activity and is not caused by weak Zeitgeber conditions during midsummer.Water temperature might indirectly determine time of spawning of the river lamprey.     

Parasite fauna of the European river lamprey Lampetra fluviatilis (L.) from Lake Onega

Data on the parasite fauna of the adult European river lamprey Lampetra fluviatilis (L.) from Lake Onega are reported. Ten parasite species are found, including trematodes Diplostomum petromyzifluviatilis and D. spathaceum (metacercariae), cestode Proteocephalus longicollis, nematodes Cucullanus truttae and Raphidascaris acus, acanthocephalan Echinorhynchus salmonis, ectoparasitic infusoria Chilodonella hexastica, Trichodina tenuidens, and Trichodinella epizootica, and fungus Saprolegnia parasitica. Three species are found to be dominate, namely D. petromyzifluviatilis, Cucullanus truttae, and P. longicollis. Comparative analysis of the parasite faunas of the lampreys from other basins is carried out. Some similarity in the parasite faunas of lampreys and salmonids is discovered.     

Population genetics of a cyclostome species pair, river lamprey (Lampetra fluviatilis L.) and brook lamprey (Lampetra planeri Bloch)

Horizontal agarose gel electrophoresis of 24 allozyme loci in four species of Central European lampreys (321 Lampetra planeri , 83 L. fluviatilis , 11 Eudontomyzon mariae and nine Petromyzon marinus ) was used to study the 'paired species' L. fluviatilis and L. planeri . The genetic differentiation of the anadromous river lamprey ( L. fluviatilis ) from the stationary brook lamprey ( L. planeri ) was within the range of ingroup differentiation of the latter, but L. fluviatilis exhibited much greater population cohesion over a more extended geographic range: G _ST = 0.0537 versus G _ST = 0.3398, N _em = 4.402 versus N _em = 0.4856, mean genetic among-stock distances D = 0.0047 versus D = 0.0257. L. planeri populations coexisting geographically with L. fluviatilis in the Rhine and Elbe river systems were genetically more cohesive than L. planeri stocks from the Danubian basin where L. fluviatilis is absent. Danubian L. planeri populations exhibit a lower degree of heterozygosity than brook lampreys from the Rhine river system, but comprise deeper genetic lineages ( G _ST = 0.4629 versus G _ST = 0.2434), despite being sampled from a much more restricted area. Isolation-by-distance is observed for L. planeri from the Danubian but not from the Atlantic drainage basins. Transspecific gene flow between L. planeri from Atlantic drainage basins and the long-distant migrating L. fluviatilis is inferred, raising doubt on the validity of two separate biospecies. E. mariae and P. marinus are clearly differentiated from Lampetra spp. at several allozyme loci.     

Mitochondrial and lysosomal pathways of lamprey (Lampetra fluviatilis L.) hepatocyte death

Mechanisms of mitochondrial and lysosomal pathways of natural death of lamprey hepatocytes are described at the spring period of the prespawn migration. The mitochondrial pathway (release of cytochrome c from mitochondria into cytosol and activation of caspases) is realized by the classic scheme of apoptosis. Comparatively recently, the lysosomal pathway of cell death associated with cathepsin B activation has been revealed in cells in pathologies, specifically in obstruction of gallbladder and bile ducts. A peculiarity of lamprey hepatocytes consists in that in the adult animal liver there takes place biliary atresia (the absence of gallbladder and bile ducts. Thereby, the lamprey hepatocytes are an excellent object for study of this new pathway of cell death. We have revealed development of the mitochondrial and the lysosomal pathways of cell death of lamprey hepatocytes.     

Fine structure of the interplatelet area in the gills of the macrophthalmia stage of the river lamprey,Lampetra fluviatilis (L.)

The interplatelet epithelium of the gills of freshwater and seawater adapted macrophthalmia stages of the river lamprey, Lampetra fluviatilis, was studied by electron microscopy. Three main cell types: basal, ion-excretory and superficial cells were identified and described. Ion-excretory cells were exposed to the environment in sea water but covered by a layer of superficial cells in fresh water. Electron-dense secretory granules in the apex of the cell were more abundant in fresh water. In fresh water, a few of the superficial cells contained numerous mitochondria and were identified as ion-uptake cells. In view of the scarcity of ion-uptake cells, the possibility that the ion-excretory cells are also responsible for ion-uptake in fresh water is discussed. Phagocytic removal of degenerating ion-excretory cells may be an important mechanism for the conservation of materials in a starving animal.     

The hypothalamo-hypophysial system of the lamprey,Lampetra fluviatilis L.

The proximal neurosecretory contact region (PNCR) of the lamprey, a homologue of the median eminence of tetrapods, was studied by light, fluorescence and electron microscopy. Paraldehyde fuchsin-positive neurosecretory fibers are seen mainly in the central part of the rostral subdivision of the PNCR. The Falck-Hillarp technique reveals a weak, mainly diffuse yellow-green fluorescence in the PNCR. The ultrastructure of the tanycyte layer of the PNCR is very similar to that in the neurohypophysis of the same species, although the funnel-shaped protrusions of the third ventricle in the rostral part of the PNCR are more frequent than in the neurophypophysis. Peptidergic A1 and A2 neurosecretory fibers are characterized by neurosecretory granules of 120-200 nm and 100-150 nm in diameter, respectively. Monoaminergic B type fibers contain granules 80-100 nm in diameter. Neurosecretory terminals and the vascular endfeet of tanycytes make contact with the basement membrane of the avascular connective tissue layer separating the PNCR from the hypophysial pars distalis. It is suggested that both peptide and monoamine neurohormones diffuse through the thick connective tissue septa into the underlying blood vessels which supply the pars distalis and thus affect the function of its glandular cells.     

The hypothalamo-hypophysial system of the lamprey,Lampetra fluviatilis L.

The distribution of monoaminergic structures was studied in the proximal neurosecretory contact region and neurohypophysis of the lamprey by light and electron microscopic radioautography. Only weak radioautographic reactions were found in the proximal neurosecretory contact region 1 h after injection of 3H-dopamine. High-resolution radioautography revealed some labeled neurosecretory terminals mainly in contact with the basement membrane of the connective tissue layer separating the proximal neurosecretory contact region from the hypophysial pars distalis. The number of silver grains as well as the number of neurosecretory terminals marked by the presence of labeled dopamine was much higher in the neurohypophysis of the same species. In the latter, labeled neurosecretory terminals were found in contact with the connective tissue layer containing blood vessels of the general circulation. Some neurosecretory terminals make synaptoid contacts with tanycyte perikarya and their basal processes. According to their ultrastructure and the size of their granules, the labeled neurosecretory terminals are identical with the B type terminals described in both neurohemal regions (transmission electron microscopy). No labeled neurosecretory terminals were observed in the proximal neurosecretory contact region and the neurohypophysis of lampreys treated with the serotonin precursor, 3H-5-hydroxytryptophan.     

Kinetic properties of sodium transport pathways in the river lamprey Lampetra fluviatilis erythrocytes

To activate Na+/H+ exchange, intracellular pH (pHi) of erythrocytes of the river lamprey Lampetra fluviatilis were changed from 6 to 8 using nigericin. The Na+/H+ exchanger activity was estimated from the values of amiloride-sensitive components of Na+ (22Na) inflow or of H+ outflow from erythrocytes. Kinetic parameters of the carrier functioning were determined by using Hill equation. Dependence of Na+ and H+ transport on pHi value is described by hyperbolic function with the Hill coefficient value (n) close to 1. Maximal rate of ion transport was within the limits of 9-10 mmol/l cells/min, and the H+ concentration producing the exchanger 50% activation amounted to 0.6-1.0 microM. Stimulation of H+ outcome from acidified erythrocytes (pHi 5.9) with increase of H+ concentration in the incubation medium is described by Hill equation with n value of 1.6. Concentration of Na+: for the semimaximal stimulation of H+ outcome amounted to 19 mM. The obtained results indicate the presence in lamprey erythrocytes of only one binding site for H+ from the cytoplasm side and the presence of positive cooperativity in Na+ binding from the extracellular side of the Na+/H+ exchanger. Its efflux from cells in the Na+ -free medium did not change at a 10-fold increase of H+ concentration in the incubation medium. The presented data indicate differences of kinetic properties of the lamprey erythrocyte Na+/H+ exchanger and of this carrier isoforms in mammalian cells. In intact erythrocytes the dependence of the amiloride-sensitive Na+ inflow on its concentration in the medium is described by Hill equation with n 1.5. The Na+ concentration producing the 50% transport activation amounted to 39 mM and was essentially higher as compared with that in acidified erythrocytes. These data confirm the concept of the presence of two amiloride-sensitive pathways of Na+ transport in lamprey erythrocytes.     

Oxidative enzymes and myosin-ATPase in the trunk musculature of the river lamprey (Lampetra fluviatilis).

Synopsis The distribution and activities of several oxidative enzymes and of myosin-ATPase have been studied in the trunk musculature of the river lamprey. The strongest activity of oxidative enzymes and of myosin-ATPase was shown by the parietal fibre bundles of the myotomal subunits, whilst the central fibres reacted to a lesser extent.Pre-incubation of sections in media containing formaldehyde and glycine or with buffers of different pH, followed by incubation for myosin-ATPase, also differentiated the muscle fibres into a specific distribution pattern within the myotomes, resembling that of the oxidative enzymes to some extent.The parietal fibres were found to be of the slow type (type I) and the central fibres to be fast (type II A).