Karl Jürss

Mitochondria-rich (MR) cells and the activities of the Na+/K+-ATPase and carbonic anhydrase in the gill and opercular epithelium of Oreochromis mossambicus adapted to various salinities

1. 1. The activities of the Na+K+-ATPase and carbonic anhydrase and the number and size of mitochondria rich cells were determined in the gills and opercular epithelia of tilapias adapted to freshwater, brackish water, seawater, 130% seawater and 170% seawater. 2. 2. In the gill all parameters examined increased significantly in correlation to an enhanced environmental salinity, whereas in the opercular epithelium the activities of the enzymes remained constant. 3. 3. On the basis of size-frequency analysis two classes of mitochondria rich cells were found.

Molecular identification key based on PCR/RFLP for three polychaete sibling species of the genus Marenzelleria, and the species’ current distribution in the Baltic Sea

Studies of Marenzelleria species were often hampered by identification uncertainties when using morphological characters only. A newly developed PCR/RFLP protocol allows a more efficient discrimination of the three species Marenzelleria viridis, Marenzelleria neglecta and Marenzelleria arctia currently known for the Baltic Sea. The protocol is based on PCR amplification of two mitochondrial DNA gene segments (16S, COI) followed by digestion with restriction enzymes. As it is faster and cheaper than PCR/sequencing protocols used so far, the protocol is recommended for large-scale analyses. The markers allow an undoubted determination of species irrespective of life stage or condition of the worms in the samples. The protocol was validated on about 950 specimens sampled at more than 30 sites of the Baltic and the North Sea, and on specimens from populations of the North American east coast. Besides this test we used mitochondrial DNA sequences (16S, COI, Cytb) and starch gel electrophoresis to further investigate the distribution of the three Marenzelleria species in the Baltic Sea. The results show that M. viridis (formerly genetic type I or M. cf. wireni) occurred in the Öresund area, in the south western as well as in the eastern Baltic Sea, where it is found sympatric with M. neglecta. Allozyme electrophoresis indicated an introduction by range expansion from the North Sea. The second species, M. arctia, was only found in the northern Baltic Sea, where it sometimes occurred sympatric with M. neglecta or M. viridis. For Baltic M. arctia, the most probable way of introduction is by ship ballast water from the European Arctic. There is an urgent need for a new genetic analysis of all Marenzelleria populations of the Baltic Sea to unravel the current distribution of the three species.

Cellular and epithelial adjustments to altered salinity in the gill and opercular epithelium of a cichlid fish (Oreochromis mossambicus)

Morphological features of the gill and opercular epithelia of tilapia (Oreochromis mossambicus) have been compared in fish acclimated to either fresh water (FW) or hypersaline water (60‰ S) by scanning electron and fluorescence microscopy. In hyperosmoregulating, i.e., FW-acclimated, tilapia only those mitochondria-rich (MR) cells present on the filament epithelium of the gill were exposed to the external medium. After acclimation of fish to hypersaline water these cells become more numerous, hypertrophy extensively, and form apical crypts not only in the gill filament but also in the opercular epithelium. Regardless of salinity, MR cells were never found to be exposed to the external medium on the secondary lamellae. In addition, two types of pavement cells were identified having distinct morphologies, which were unaffected by salinity. The gill filaments and the inner operculum were generally found to be covered by pavement cells with microridges, whereas the secondary lamellae were covered exclusively by smooth pavement cells.

Where did Marenzelleria spp. (Polychaeta: Spionidae) in Europe come from?

Abundant populations of Marenzelleria spp. were reported for the first time in the North Sea during the late 1970s and then in the Baltic Sea in 1985. Genetic analysis by means of allozyme electrophoresis and sequencing of a segment of mitochondrial 16srDNA showed that two different genetic types or sibling species of Marenzelleria were present in Europe. Marenzelleria Type I is found only in the North Sea, whereas Type II has been found in both the North Sea and the Baltic Sea. The North Sea animals (Type I) correspond to Type I specimens found in North American coastal waters between Nova Scotia and Cape Henlopen (Delaware), while Marenzelleria Type II from the Baltic Sea correspond to Marenzelleria type II animals from the Arctic (Tuktoyaktuk Harbor, Northwest Territories, Canada), New Hampshire and coastal waters between Chesapeake Bay southward to the Ogeechee River (Georgia). Human mediated introduction (by shipping) and natural range expansion are discussed as the possible causes of these virtually simultaneous invasions by two sibling species. Marenzelleria Type I appears to colonize habitats with a higher salinity and/or in which salinities tend to fluctuate considerably. The osmolality of the coelomic fluid after acclimation to various salinities between 0.25 and 18‰ is the same for both sibling species/genetic types. Although the two types do not differ in respect of hyperosmoregulation (<10‰), differences may exist in their cell volume regulation or its time course in the almost isoosmotic range at salinities >10‰.

Biochemical adaptation of juvenile carp (Cyprinus carpio L.) to food deprivation

Abstract 1. 1. Food deprivation for 28 days leads to biochemical adaptation in juvenile carp which reduces their metabolism to a level corresponding to their energy deficit. 2. 2. Starved carp have lower white muscle and liver RNA concentrations than fed carp. Their RNA/DNA quotients are therefore also lower, indicating protein synthesis restriction under food deprivation. 3. 3. Food deprivation reduces the cell size of the liver, but not of white muscle. Liver cell size reduction is associated with a decrease in soluble and total protein concentrations (mg/mg DNA and protein/DNA respectively). 4. 4. Energy saving reductions in enzyme activity are induced in intermediary hepatic metabolism. The activities of NADP+-specific dehydrogenases (G6PDH, 6PGDH, IDH, ME) implicated in lipogenesis and of the amino acid metabolism enzyme G1DH are greatly depressed after four weeks of food deprivation.

Are there two species of the polychaete genus Marenzelleria in Europe

North Sea and Baltic Sea populations of the introduced polychaete Marenzelleria viridis (Verrill, 1873) reproduce at different times (spring and autumn, respectively). Enzyme separation by starch gel electrophoresis revealed major differences between specimens from the Baltic Sea and those from the North Sea (collected in 1992 and 1993) but a high degree of homogeneity among populations from the same sea. Three enzyme loci, glucose-6-phosphate isomerase (GPI-A, GPI-B) and malate dehydrogenase (MDH), were fixed to 100% by different alleles in the North and Baltic Sea populations, respectively. Different alleles are dominant for mitochondrial aspartate aminotransferase (mAAT) with allele frequencies of ca. 0.97 in all sampled populations from the North Sea and Baltic Sea, respectively, but heterozygotes were found in all populations. These genetic differences could be due to environmentally induced selection or genetically different origins of the populations, suggesting that populations of the genus Marenzelleria in the North and Baltic Seas may be two different species.

Colonization of Europe by two American genetic types or species of the genus Marenzelleria (Polychaeta: Spionidae). An electrophoretic analysis of allozymes

Allozyme electrophoresis was conducted in an attempt to identify the origin ofMarenzelleria sp. found in the North Sea and Baltic Sea. The analysis covered eight enzymes with ten loti from nine populations found on the North American Atlantic toast, these populations in the North Sea and five populations in the Baltic. The North Sea spionids correspond to the Type IMarenzelleria from North American coastal waters between Barnstable Harbor (Massachusetts) and Cape Henlopen (Delaware). Neis genetic distance between these North American populations and those from the North Sea wasD = 0.010 to 0.020. TheMarenzelleria sp. found in the Baltic Sea very probably stems from North American populations of Type II found from the region of Chesapeake Bay (Trippe Bay) south to the Currituck Sound (North Carolina). The genetic distance between these North American populations and the Baltic populations isD = 0.000 to 0.001. The invaders appear to have lost little of their genetic variation while colonizing the North and Baltic Seas. Probably, both colonizing events tan be attributed to large numbers of individuals reaching Europe simultaneously on one or more occasions. In addition, aMarenzelleria Type III was found by electrophoresis among specimens from Currituck Sound (North Carolina), rohere it is sympatric withMarenzelleria Type II. Salinity is discussed as an important factor for the establishment ofMarenzelleria Type I in the North Sea and Type II in the Baltic Sea.

Genetic differences between two allopatric populations (or sibling species) of the polychaete genus Marenzelleria in Europe

Abstract Genetic variation and differentiation in introduced European populations of the spionid polychaete Marenzelleria viridis were studied by enzyme electrophoresis. Major differences exist between the North Sea and Baltic populations, although the genetic structure within each of them is largely homogeneous. Nine loci were studied, five of which are of diagnostic value. The genetic distance between the North Sea population and the Baltic population is 0.891-0.897. Genetic differences of this extent suggest that the Marenzelleria populations found in the North Sea and Baltic Sea are two different species.

Effects of temperature, salinity, and feeding on aminotransferase activity in the liver and white muscle of rainbow trout (Salmo gairdneri Richardson).

1. The liver-somatic index of rainbow trout is governed by temperature and salinity, and by the interaction of these two factors. 2. The overall liver-alanine aminotransferase activity (in units/100 g body weight) increases slightly with increasing salinity of the surroundings in the case of rainbow trout. 3. The overall liver-aspartate aminotransferase activity (in units/100 g body weight) in rainbow trout depends on their food and the temperature at which they are kept. 4. Salinity adaptation leads to reductions in the specific alanine and aspartate aminotransferase activity in the liver of rainbow trout. 5. The specific alanine aminotransferase activity in the muscle of starving rainbow trout kept in diluted seawater (580 mOsm/l, 18 degrees C) is clearly higher than in control animals kept in tapwater.

Chapter 7 Amino acid metabolism in fish

Publisher Summary This chapter focuses on the mechanism of amino acid metabolism in fish. From a nutritionists standpoint, the animal organism has one common pool of free amino acids (FAA or AA). This pool also feeds all reactions in which AA are consumed. The total FAA pool is broken down by the cell membrane into an intracellular and an extracellular pool. The intracellular pool is organ specific and probably also cell specific. The intracellular pools of different organs are linked by the extracellular pool (blood circulation). The various organs can, therefore, interact with each other as the nutritional status of the organism changes. Transport mechanisms are needed for the movement of amino acids from the extracellular to the intracellular pool. The chapter discusses the roles and interactions of the organs in the fish AA metabolism and draws attention to corresponding control points. To simplify the discussion, the amino acids are considered as being metabolized mainly in just four organs: the intestine, liver, kidney and skeletal muscle. An overview of interorgan amino acid fluxes is also presented in the chapter.