The effect of lunar eclipse on the vertical migration behaviour of Meganyctiphanes norvegica (Crustacea: Euphausiacea) in the Ligurian Sea

The vertical migration of a zooplankton community dominated by the euphausiid Meganyctiphanes norvegica was monitored between 16 and 23 September 1997 with a 153 kHz Acoustic Doppler Current Profiler (ADCP) and a MOCNESS net. The sampling period covered a phase in the lunar cycle when the rise of the moon (full moon) coincided initially with sunset and then became progressively later. On 16 September 1997, a lunar eclipse occurred 45 min after sunset, lasting for 2 h. At dusk, the ADCP observed the upward vertical migration of two principal backscattering bands 10 min apart with vertical velocities of up to 7 cm s^-1. After a period at the surface, a more diffuse band subsequently sank at a slower rate (1-2 cm s^-1) to a depth of 75-100 m. Net samples showed that the earlier band consisted mainly of the pteropod Cavolinia inflexa, whilst the later band was mostly euphausiids, predominantly M.norvegica. This species was also the major constituent of the band that sank. The timing of upward migration was relatively constant over the sampling period, but there was an increasing delay of the secondary sinking until 21 September. This showed as a strong correlation between the onset of sinking and the time of moonrise. The lunar eclipse on 16 September perturbed this pattern, such that animals did not sink soon after their arrival at the surface, as occurred on 17 September but remained at the surface until the end of the umbra. This suggests that M.norvegica can perceive moonlight and that this influences vertical migration. Evidence that the behaviour is not solely mediated by this erogenous factor, however, is seen in the pattern that emerged after 21 September, when midnight sinking occurred at a relatively constant time after sunset and before moonrise. These observations support the hypothesis that moonlight is a Zeitgeber for an endogenous rhythm that synchronizes secondary sinking behaviour with the lunar cycle.      

Ecological investigations on the zooplankton community in Balsfjorden,Northern Norway: seasonal changes in the lipid class composition of Meganyctiphanes norvegica (M. Sars), Thysanoessa raschii (M. Sars), and T. inermis (Krøyer)

The lipid class composition of three krill species, Meganyctiphanes norvegica (M. Sars), Thysanoessa raschii (M. Sars), and T. inermis (Krøyer), was determined throughout the year in Balsfjorden, Northern Norway. Meganyctiphanes norvegica had triglycerides as its major neutral lipid, Thysanoessa raschii had mainly triglycerides with small amounts of wax esters, whereas T. inermis had mainly wax esters with lesser amounts of triglycerides. Neutral lipids were generally accumulated by the krill during spring-early summer, maintained at high levels through to mid-winter and then declined to minimal levels during early spring. Differences in rates of deposition and mobilization of neutral lipid between males and females occurred in Meganyctiphanes norvegica and Thysanoessa raschii but not in T. inermis. T. raschii accumulated lipid somewhat later in the year than T. inermis but earlier than Meganyctiphanes norvegica. A major rôle for lipid in the elaboration of gonads is indicated. The accumulation of either wax esters or triglycerides by euphausiids is considered in terms of the feeding habits and ecological niche differentiation of the species.     

Beitrag zur Kenntnis desAlnetum incanae in der Tschechischen Sozialistischen Republik (ČSR)

Gegenstand dieses Beitrages ist die syntaxonomisch-synökologische Charakteristik desAlnetum incanae Lüdi 1921 in den Tschechischen Ländern. Bestände dieser montanen Auenwaldassoziation begleiten hier Flussgewässer in Gebirgstälern und am Hochgebirgsrand, meist in den Lagen von 650–900 mü. NN. DasAlnetum incanae wird in zwei Subassoziationen geteilt. Das feuchteliebendeAlnetum incanae calthetosum Knapp exNeuhäuslová-Novotná subass. nova ist an Gleyböden (Nassgleye, sauerstoffreiche Gleye) gebunden, dasAlnetum incanae typicum Oberd. 1949 (mit zwei Varianten)bestockt Paternia-Böden. DieAegopodium podagraria-Variante der typischen Subassoziation bevorzugt pedogenetisch mehr entwickelte Böden mit tiefem Grund-wasser, meist in der Kontaktzone zu Klimaxgesellschaften.     

Distribution and reproduction strategies of krill (Euphausiacea) on the Norwegian shelf

Meganyctiphanes norvegica and Thysanoessa inermis were the dominant krill species that were observed on the Norwegian shelf. T. inermis and M. norvegica were found in abundances of up to 14 and 22 no. m^?2, respectively, on the mid Norwegian shelf (Møre plateau, Halten, Sklinna, Træna banks) and up to the Lofoten area. The main distribution of the krill indicates that they are mostly restricted to the Atlantic waters of the shelf region in April and little krill was observed south of 62°N. The two dominant krill species appeared to have different strategies for the timing of spawning, thus avoiding direct overlap of spawning products. The majority of the T. inermis females were in the spawning condition in April. Meganyctiphanes norvegica appeared to spawn at least a month later. The sizes of the first time spawners of T. inermis were around 11–16 mm, and they were approximately 1 year old. The sizes of the second time spawners were around 17–22 mm. The spawning of krill on the Norwegian shelf coincides with the blooming of the spring phytoplankton in this region . Advection of eggs and larvae of krill, as well as other plankton, is important not only to the shelf and slope region, but also for the functioning of the wider Norwegian Sea ecosystem and the adjacent areas.     

Behavioural differences in relation to pycnoclines during vertical migration of the euphausiids Meganyctiphanes norvegica (M. Sars) and Thysanoessa raschii (M. Sars)

An observation on differences in the vertical migration patternbetween Meganyctiphanes norvegica (M. Sars) and Thysanoessaraschii (M. Sars) caused by the presence of a thermocline isreported. Generally, M.norvegica did not migrate through a thermoclineat 50–60 m depth while T.raschii did. This observationis discussed in the context of how the combination of differencesin vertical migration and advection over sill depth may affectthe abundance of fjord stocks of these two euphausiid species.     

Der Einfluss von K-Humat auf Teilung und Längenwachstum der Wurzelspitzenzellen vonAllium cepa L.

0,1 und 0,01 prozentige K-Humatlösungen besohleunigen in den ersten Züchtungstagen das Wurzelwachstum der Keimpflanzen der KüchenzwiebelAllium cepa L. Durch unmittelbare Zählung der Mitosen in Quetschpräparaten der Wurzelspitzen nach der Methode von PAZOUBEK (1960) ist festgestellt worden, das sich bei einer Wirkung, die länger dauert als 24 Stunden, der Prozentsatz an Mitosen naehweisbar gegenüber der Züehtungskontrolle in aqua dest. erhöht. Dieser Unterschied wächst mit der Verlängerung der Einwirkungsdauer von K-Humat. An Längsschnitten durch die Wurzelspitze in fünf aufeinander folgenden Abschnitten vom Beginn der Verlängerungszone an wurde durch unmittelbare Messung der Zellenlange festgestellt, dass K-Humat in allen Fällen das Längenwachstum der Zellen nachweisbar erhöht. Der Unterschied zwischen der Zellenlänge der Versuchspflanzen und der Kontrolle wächst mit der Entfernung vom Beginn der Verlängerungszone, erreicht sein Maximum und sinkt wieder ab. Es ist auch festgestellt worden, dass K-Humat-Lösungen bis zu gewissem Grade die ungünstigen Lebensbedingungen ausgleichen, die durch eine längere Züchtungsperiode in Wasserkulturen ohne Mineralnährstoffe hervorgerufen worden sind. Aus den Ergebnissen geht hervor, dass das raschere Zellenwachstum sowohl durch Vermehrung der Zellenteilungen, als auch durch eine Erhöhung des Längenwachstums bewirkt wird. K-Humat beeinflusst das Längenwachstum der Zellen bedeutend stärker als die Zellenteilung.     

Gentianella × austroamarella hybr. spec. nova

Im nördlichen Böhmerwaldvorgebirge trifft die borealeGentianella amarella auf drei südlichen Vorpostenfundorten mit der südosteuropäischenGentianella austriaca zusammen und bildet mit ihr eine bisher unbekannte Hybride, die alsGentianella × austroamarella beschrieben wird.     

Moult cycle and seasonal activities of chitinolytic enzymes in the integument and digestive tract of the Antarctic krill,Euphausia superba

Summary Chitinolytic activity was quantified in euphausiid integuments in relation to moulting. In Euphausia superba, shortly before moult the activity increased in chitinase and N-acetyl--D-glucosaminidase to pronounced maxima indicating the onset of massive resorption of cuticular material. Enzymatic activity of E. superba corresponded to values in Meganyctiphanes norvegica, a boreal euphausiid which was investigated for comparison, as well as in insecta. Antarctic krill from winter catches displayed activities comparable to summer material suggesting physiological preparation for moulting. Accordingly, moulting did not cease during winter. Both enzymes were also active in the digestive tract in summer as well as in winter krill: chitin containing food of phyto-and zooplankton origin is digestable. Seasonally stable activities did not point to changes in nutritional preference. In contrast to other crustacea, digestive enzyme activity was not reduced around moult, suggesting a high capacity to continuously utilize food sources including chitin. This property can be linked directly to the high energy need caused by the necessity of constant active swimming in both krill species.Supported by German Research Counsil (DFG), grant-nos. Ad 24/9 and Bu 548/1Dedicated to Professor Dr. G. Hempel on the occasion of his 60th birthday     

Phylogeny and maternal donors of the tetraploid species with St genome (Poaceae: Triticeae) inferred from CoxII and ITS sequences

Mitochondrial CoxII and ITS sequences of 29 tetraploid species with St genome were compared with their related genera and species of Pseudoroegneria (Nevski) Á. Löve (St), Hordeum L. (H), Thinopyrum bessarabicum (Savul. & Rayss) Á. Löve (E^b), Lophopyrum elongatum (Host) Á. Löve (E^e), Agropyron Gaertner (P), Australopyrum (Tzvelev) Löve (W) and Psathyrostachys Nevski (Ns). The results indicate that: (1) the maternal donors of North American and Eurasian StStHH tetraploid species may have acquired their St genome from distinct Pseudoroegneria gene pools, with Pse. spicata (Pursh) Á. Löve potentially the maternal donor of North American species; (2) Lophopyrum is the maternal donor of StStE^eE^e tetraploid species, hence, Pse. geniculata ssp. scythica (Nevski) Á. Löve, Elytrigia caespitosa (K. Koch) Nevski and El. caespitosa ssp. nodosa (Nevski) Tzvelev should be identified as species of Trichopyrum Á. Löve; (3) tetraploid species with the same maternal donors were more closely related to each other than those with different maternal donors.     

Thlaspi finitimum,eine neue Art aus dem Verwandtschaftskreis vonThlaspi jankae

Auf Grund der taxonomisch-chorologischen Analyse des Pflanzenmaterials vonThlaspi jankae A. Kern. erwies sich als berechtigt, im Verwandtschaftskreis desselben eine neue, Art,Thlaspi finitimum sp. n., zu unterscheiden. Die in den nordungarischen Hügelländern und Gebirgen wachsenden Pflanzen gehören zumT. jankae A. Kern., während das Vorkommen der neu aufgestellten ArtT. finitimum auf das Gebiet der südslowakischen Zobor-Berge (NÖ von Nitra) und des Südslowakischen Karstes beschränkt ist.     

Lipolysis post mortem in North Atlantic krill

• 1.1. Three common species of North Atlantic krill, Meganyctiphanes norvegica (M. Sars), Thysanoessa inermis (Krøyer) and T. raschii (M. Sars), have been stored at 0°C post mortem, and the lipolytic activity followed by measuring changes in the lipid composition during storage.
• 2.2. Both phosphoglycerides and triacylglycerols were subjected to extensive hydrolysis with the formation of free fatty acids in all krill species examined, whereas wax esters, constituting a considerable proportion of the lipids in the Thysanoessa species, were not hydrolysed at all.
• 3.3. In M. norvegica the triacylglycerols and phosphoglycerides were hydrolysed at similar rates, whereas in T. inermis and T. raschii the phosphoglycerides were hydrolysed most rapidly.
• 4.4. For all krill species examined, the rate of production of free fatty acids was nearly constant during the initial phase of storage, and subsequently declined on prolonged storage.
• 5.5. At the end of the storage period of 16–24 days, the free fatty acids constituted about 35% of the total lipid in M. norvegica, and about 50% in the Thysanoessa species.
• 6.6. The rate of production of free fatty acids was about the same in all the three species of krill and seemed to be independent of the total lipid content.

     

Fish predators, food availability and diel vertical migration in Daphnia

Diel vertical migration of zooplankton is a highly variableand complex behaviour which apparently cannot be explained byany single factor. We determined the relative importance offish predation, food availability and water depth in shapingthe migratory behaviour of Daphnia. A modified 2x2x2 factorialexperiment provided two levels of fish density (present/absent),food availability (ambient/high) and depth (4–10 m); shallowtreatments with fish were excluded. Triplicate 1.2 m diameterenclosures for each of the six treatments were held in an 18unit array in Peter Lake, Gogebic Co., MI, USA. Repeated measuresANOVA identified significant trends in daphnid density, migrationand fitness (determined by lipid-ovary-egg index, LOE) as wellas in chlorophyll a content of the water column for part ofa 4-week experiment in July 1988. In deep enclosures with fish,Daphnia performed significantly more intense migrations thanin fishless enclosures, save those in fishless ambient-foodenclosures. Daphnia in deep fishless enclosures without abundantfood at depth performed significantly reduced migrations. DaphnidLOE index was significantly influenced only by food content.Our results were consistent with the predator-avoidance hypothesisas well as with observations of greatest migrations where largevertical differences in food abundance exist. They support ahierarchical view of vertical migration, with presence of fishthe primary factor, and food availability the secondary factor.     

Related antipodes: a comparative study on digestive endopeptidases from Northern krill and Antarctic krill (Euphausiacea)

The Antarctic krill, Euphausia superba, and the Northern krill, Meganyctiphanes norvegica, are closely related species but occupy significantly different trophic and climatic environments. E. superba holds a key position as a phytoplankton grazer in the Southern Ocean. The omnivorous M. norvegica is an important member of plankton communities in the Northeast Atlantic. Both species expressed high proteolytic activities which were dominated by serine proteinases. In the stomachs of Antarctic krill, activities of total proteinase, trypsin, and chymotrypsin were significantly higher than in Northern krill. In the midgut glands, however, total proteinase and trypsin activities were similar in both species, but chymotrypsin activity was significantly higher in Antarctic krill. Moreover, Antarctic krill expressed four trypsin isoforms while only one isoform appeared in Northern krill. Chymotrypsin was present in either species as one single isoform. Antarctic krill adapted to the low and patchy distribution of food by elevated enzyme activities and the expression of trypsin isoforms with slightly different catalytic properties. Presumably, these enzymes facilitate in concerted action the efficient utilization of proteins from phytoplankton, the major food. Northern krill, in contrast, seems not to be equipped to face food limitation. It expresses a “simple” or “basic” set of digestive enzymes for utilizing abundant and easily digestible prey.     

Behavioral,Ecological and Genetic Differentiation in an Open Environment—A Study of a Mysid Population in the Baltic Sea

Diel vertical migration (DVM) is often assumed to encompass an entire population. However, bimodal nighttime vertical distributions have been observed in various taxa. Mysid shrimp populations also display this pattern with one group concentrated in the pelagia and the other near the bottom. This may indicate alternative migratory strategies, resembling the seasonal partial migrations seen in birds, fishes and amphibians, where only a subset of the population migrates. To assess the persistence of these alternative strategies, we analyzed the nitrogen and carbon stable isotope signatures (as proxies for diet), biochemical indices (as proxies for growth condition), and genetic population divergence in the Baltic mysid Mysis salemaai collected at night in the pelagia and close to the bottom. Stable isotope signatures were significantly different between migrants (pelagic samples) and residents (benthic samples), indicating persistent diet differences, with pelagic mysids having a more uniform and carnivorous diet. Sequencing of the mitochondrial cytochrome subunit I (COI) gene showed genetic differentiation attributable to geographic location but not between benthic and pelagic groups. Divergent migration strategies were however supported by significantly lower gene flow between benthic populations indicating that these groups have a lower predisposition for horizontal migrations compared to pelagic ones. Different migration strategies did not convey measurable growth benefits as pelagic and benthic mysids had similar growth condition indices. Thus, the combination of ecological, biochemical and genetic markers indicate that this partial migration may be a plastic behavioral trait that yields equal growth benefits.     

Proteolysis post mortem in North Atlantic krill

• 1.1. The autoproteolytic processes in selected species of North Atlantic krill, Meganyctiphanes norvegica (M. Sars), Thysanoessa inermis (Krøyer) and T. raschii (M. Sars) have been examined at 0°C by following the release of peptides and free amino acids.
• 2.2. The krill contains high levels of peptide hydrolases, and autoproteolysis seems to be due mainly to digestive enzymes localized in the hepatopancreas and the intestinal tract of the animals.
• 3.3. During autoproteolysis the individual amino acids were generally released at rates corresponding to their proportion in the bulk protein of the krill. The major exceptions were alanine which accumulated in amounts larger than was to be expected from the composition of the krill protein, and glutamic acid/glutamine, aspartic acid/asparagine, arginine, and to some extent glycine, proline and serine, which accumulated to a lesser extent than was to be expected.
• 4.4. Storage of krill for 1 week resulted in only minor changes in the total content of amino acids as determined after acid hydrolysis, with the exception of alanine which increased in concentration.
• 5.5. The results suggest that the formation of free alanine is partly due to reactions other than proteolysis.
• 6.6. The release of free amino acids was accompanied by a considerable increase in the amount of small peptides, and glutamic acid/glutamine, aspartic acid/asparagine, glycine and proline tended to accumulate in these peptides.
• 7.7. The autoproteolytic activity of the Thysanoessa species showed seasonal variations, probably in response to food availability. In the case M. norvegica, the results suggest that there are smaller fluctuations in the level of proteolytic enzymes, probably indicating less pronounced variations in the food intake over the year.

     

Chemical composition of North Atlantic krill

• 1.1. The main chemical components of Meganyctiphanes norvegica (M. Sars), Thysanoessa inermis (Krøyer) and T. raschii (M. Sars) have been examined.
• 2.2. Protein accounted for 42–47% of the dry weight of M. norvegica and 32–50% of the dry weight of the Thysanoessa species. On a wet weight basis, the protein content was relatively constant and independent of season.
• 3.3. The dominating amino acids in the bulk protein of the krill were glutamic acid/glutamine, aspartic acid/asparagine, glycine, alanine, lysine and leucine.
• 4.4. Lipids were present in amounts of 13–29% of the dry weight in M. norvegica, 15–50% in T. inermis and 12–44% in T. raschii, and the lipid content varied with season.
• 5.5. The main nitrogen extractives in krill, expressed on a dry weight basis, were free amino acids (5–10%), trimethylamine oxide (about 4%), peptides (about 1%) and nucleotides (0.4–1.3%). Trimethylamine and ammonia were present in very low concentrations in living krill.
• 6.6. The amino acids taurine, glycine, proline, arginine, sarcosine and alanine made up 89–93 mol% of the free amino acid pool.
• 7.7. The ash content of krill was in the order of 10–13% of the dry weight, and fluoride represented 1040 and 3200 ppm in the Thysanoessa species and M. norvegioca, respectively.

     

Catalytic Properties of Two Pyruvate Kinase Isoforms in Nordic Krill,Meganyctiphanes norvegica,With Respect to Seasonal Temperature Adaptation

Two isoforms of pyruvate kinase (PK I and PK II) were partly purified and characterized from the Nordic krill Meganyctiphanes norvegica. Both PK variants were present in summer and winter specimens with a tissue specificity in abdominal muscle (PK I) and cephalothorax (PK II). Obvious differences were found in chromatographic and kinetic characteristics. Enzymatic adaptations to low temperatures were found in PK I only, whereas PK II did not contribute to seasonal temperature adaptation. In winter specimens, the activation energy of PK I decreased significantly from 53.2 ± 1.5 to 50.2 ± 1.2 kJ·mol⁻¹. The affinity of PK I to phosphoenol-pyruvate was higher in winter (K_M = 0.024 ± 0.002 mmol·l⁻¹) compared to summer (K_M = 0.033 ± 0.003 mmol·l⁻¹). Both effects lead to an increased efficiency of this enzyme isoform in the cold. In contrast, K_M values of PK II showed no significant differences between summer (K_M = 0.181 ± 0.014 mmol·l⁻¹) and winter specimens (K_M = 0.193 ± 0.015 mmol·l⁻¹). The effects of cooperativity remained unchanged during the seasons with approximate values of n_Hill = 1.0 (PK I) and 1.5 (PK II). Fructose-1,6-bis-phosphate affected only PK II by shifting sigmoidal kinetics to hyperbolic curves resulting in a decrease of K_M to 0.027 mmol·l⁻¹. Further effectors were tested showing an inhibiting effect of oxalate on both isoforms with a reduction to 20% and 50% in PK I and PK II, respectively. Presumably, the ecophysiological effect of the capacity to regulate muscle PK is related to the necessity to increase motility during vertical migration and phases of feeding activity.     

Life-cycle strategies and seasonal migrations of oceanic copepods in the Irminger Sea

Abundance and seasonal vertical distribution of dominant zooplankters in the Irminger Sea was studied from data collected during four cruises between November 1996 and June 1997. In addition, egg production of Calanus finmarchicus was measured during winter, spring and summer 1996–2001. Five taxa constituted >95% of the copepod biomass, C. finmarchicus, Pareuchaeta norvegica, C. hyperboreus, Oithona spp. and Oncaea spp. A seasonal migration pattern was evident for C. finmarchicus, P. norvegica and Oithona spp.: from December to February, they inhabited the deeper layers, whereas, from April to June, they were most abundant in the upper layers. Oncaea spp. also stayed deep during winter and only a very limited part of the population rose to the surface during summer. C. hyperboreus remained deep from December to April, but had virtually disappeared in June. Reproduction of C. finmarchicus took place in May in the surface layers and was linked to the phytoplankton spring bloom. In contrast, reproduction of P. norvegica occurred at depth in February and was uncoupled with the spring bloom. C. hyperboreus did not reproduce in the Irminger Sea. Data on Oithona spp. and Oncaea spp. indicated that the former reproduced between April and June in the upper layers, whereas the latter reproduced year-round at depth. Thus, data on vertical distribution and seasonal stage composition suggested that the dominant copepods are separated, at least partly, at spatial and temporal scales with regard to overwintering and development.     

Die auswirkungen von Kahlschlag und Brand auf dasQuercetum ilicis von Süd-Toskana,Italien

Das in der südtoskanischen Maremma klimatogeneQuercetum ilicis wird in regelmässigen Abständen von etwa 12 Jahren kahlgeschlagen, wodurch tiefgreifende Änderungen in der Vegetation entstehen. Es wird in den ersten zwei Jahren ein Massenauftreten von Therophyten beobachtet und bald darauf eine allmähliche Wiederentwicklung des Waldes, die durch Stockausschläge der kräftigeren Holzarten zustande kommt. Die häufig auftretenden Brände bedingen hingegen das Entstehen desEriceto-Lavanduletum als degradierte Dauergesellschaft. Die vorliegende Arbeit stellt einen Versuch dar, die wichtigsten Momente dieser Sukzession zu beschreiben, u. zw. mit floristischen Angaben und mit der Bearbeitung von Lebensformen, ökologischen Synusien, Schichtung, Verbreitungstypen und Polyploidie.     

Anthriscetum trichospermae im Gebirge Malé Karpaty (Slowakei)

Die synmorphologische, syntaxonomische, synökologische, symphänologische und synchorologisch Charakteristik der AssoziationAnthriscetum trichospermae Hejný etKrippelová inHejný et al. 1979 ist angeführt. Es handelt sich um eine wärmeliebende, nitrophile Therophyten-Gesellschaft auf lehmigen bis lehmig-sandigen Ruderalböden, die warme, lichte oder mässig beschattete Orte, steile Feldraine und Lese-Steinhaufen in Weingärten im südlichen Teil des Gebirges Malé Karpaty (Westslowakei) besiedelt. Das Vorkommen dieser Assoziation ist auch von Ungarn angegeben.