ALBERT

Description: One concept of evolutionary ecology holds that a living fossil is the result of past evolutionary events, and is adapted to recent selective forces only if they are similar to the selective forces in the past. We describe the present environment of the living coelacanth Latimeria chalumnae Smith, 1939 at Grande Comore, western Indian Ocean and report depth-dependent cave distribution, temperature, salinity and oxygen values which are compared to the fish's distribution and its physiological demands. We studied the activity pattern, feeding behaviour, prey abundance and hunting success to evaluate possible links between environmental conditions, feeding ecology and evolutionary success of this ancient fish. Transmitter tracking experiments indicate nocturnal activity of the piscivorous predator which hunts between approximately 200 m below the surface to 500 m depth. Fish and prey density were measured between 200 and 400 m, both increase with depth. Feeding tracks and feeding strikes of the coelacanth at various depths were simulated with the help of video and laser techniques. Along a 9447 m video transect a total of 31 potential feeding strikes occurred. Assuming 100% hunting success, medium-sized individuals would obtain 122 g and large females 299 g of prey. Estimates of metabolic rates revealed for females 3.7 ml O2 kg−1 h−1 and for males 4.5 ml O2 kg−1 h−1. Today coelacanths are considered to be a specialist deep-water form and to inhabit, with their ancient morphology, a contemporary environment where they compete with advanced, modern fish.

Description: Acoustic telemetry was used to examine patterns of activity and space utilisation of coelacanths, nocturnal predators which spend the day in submarine caves. Nine coelacanths (Latimeria chalumnae) were tracked, each for a period of 1 to 16 nights at Grande Comore, West Indian Ocean. Activities lasted on average 9 h, usually starting shortly after sunset and ending before sunrise. Vertically, coelacanths moved up and down at and below cave level by following the bottom contour, mainly between 180 and 400 m depth. The deepest record was 698 m, the shallowest 133 m. Most time was spent between 200 and 300 m depth. Large individuals performed deep excursions to depths below 400 m, usually once per night. The fish spent most time in water temperatures of 15 to 19 °C; they rarely ventured into waters warmer than 22 °C measured at depths shallower than 160 m depth. Horizontally, coelacanths stayed in narrow areas ranging from 〈1 to 10 km of coastline. Coelacanths are extremely slow drift-hunters with an estimated average swimming speed of 3.2 m min−1, often travelling not more than 3 km per night. They probably take advantage of local upwelling and downwelling and slow currents occurring parallel to the steep slopes. This study shows that coelacanths are inhabitants of the subphotic zone, where they are active mainly below the depth of their daytime refuges.

Description: A detailed analysis of beak length to body size and mass measurements was carried out for the glacial squid Psychroteuthis glacialis, which is an endemic cephalopod species in the Southern Ocean. Beak lengths (lower rostral length) were measured from 211 specimens which had been sampled in the Atlantic sector of the Southern Ocean. The basic idea was to find some calibration model in order to inter- or extrapolate missing mantle length and/or wet body mass data by means of beak lengths. The relationships between beak length and mantle length/wet body mass bear essential information for future use in biomass estimates in Southern Ocean top predators, since beaks of P. glacialis occur frequently in the stomach contents of Antarctic seabirds, seals and toothed whales. Therefore, lower rostral lengths were plotted against both mantle length and wet body mass to determine the relationship between these variables. The relationships had limited scatter and very high coefficients of determination, showing that lower rostral length is a good predictor of the squid's mantle length and wet mass. A non-linear 3rd order polynomial regression of lower rostral length against mantle length was identified as the best fitted calibration model, explaining 93% (R 2) of the associated variance. The relationship between lower rostral length and wet body mass was empirically well fitted through regressing ln-transformed values of lower rostral length against wet body mass, explaining 95% (R 2) of the associated variance. The present investigation provides measurements for a wide size range of P. glacialis individuals compared to earlier studies, which were limited on very small data sets.

Description: Based on the re-interpretation of published data, the von Bertalanffy growth function parameters of the coelacanth, Latimeria chalumnae, are estimated as L∞=218 cm total length, s.e. 23; K=0.059 (year−1), s.e. 0.012; t0=−3.3 (year), s.e. 0.5, corresponding to a life span of 48 years. The length–weight relationship of the form W=a*TL∧b, with wet weight (W) in g and total length (TL) in cm, is estimated as a=0.0278, b=2.89, r2=0.893, n=87, range=42.5–183 cm TL. Using extreme value theory, the maximum length for female coelacanths is estimated as 199 cm TL (95% confidence interval=175–223 cm TL) and for males as 168 cm TL (95% confidence interval 155–180 cm TL). Based on data from seven females with embryos or mature eggs, the length-at-first-maturity for females is estimated to be about 150 cm TL, corresponding to an age of about 16 years. Based on the value of t0=−3.3 years and on the presence of three scale rings found in a newborn coelacanth, the period of embryogenesis lasts for about three years, the longest known in vertebrates. The natural mortality rate is estimated at M=0.12. Population food consumption is found to be 1.4 times the existing biomass per year, and gross food conversion efficiency indicates that only 10% of the consumed food is utilized for somatic growth.

Description: Ferromanganese crusts from the Atlantic, Indian and Pacific Oceans record the Nd and Pb isotope compositions of the water masses from which they form as hydrogenous precipitates. The10Be/9Be-calibrated time series for crusts are compared to estimates based on Co-contents, from which the equatorial Pacific crusts studied are inferred to have recorded ca. 60 Ma of Pacific deep water history. Time series of ɛNd show that the oceans have maintained a strong provinciality in Nd isotopic composition, determined by terrigenous inputs, over periods of up to 60 Ma. Superimposed on the distinct basin-specific signatures are variations in Nd and Pb isotope time series which have been particularly marked over the last 5 Ma. It is shown that changes in erosional inputs, particularly associated with Himalayan uplift and the northern hemisphere glaciation have influenced Indian and Atlantic Ocean deep water isotopic compositions respectively. There is no evidence so far for an imprint of the final closure of the Panama Isthmus on the Pb and Nd isotopic composition in either Atlantic or Pacific deep water masses.

Description: Grazing experiments were conducted with natural mesozooplankton from Kiel Bight, Germany, using radioactive labelled phytoplankton cultures and seston size fractions. The results of experiments using phytoplankton cultures indicated that bivalve veligers performed highest clearance of particles within a size range of 4.7 to 6.3 µm, whereas optimum particle size for copepods was 15 µm. The results of experiments using labelled natural seston size fractions identified bivalve veligers and appendicularians as those responsible for the removal of particles within the smallest size class (〈2 µm). Seston size fractions larger than 5 µm were mainly cleared by copepods and nauplii. As particle size increased, the contribution of copepod clearance to total zooplankton clearance within size classes increased from 57% (〈5 µm size class) to more than 81% (30 to 100 µm size class). When the nauplii clearance rates were included, the total copepod clearance accounted for 90 to 97.6% of the total volume cleared of particles bigger than 10 µm. Despite low abundances of bivalve veligers and appendicularians in Kiel Bight at the time of the experiment, we calculated that approximately 10 and 8.5%, respectively, of the carbon ingested by total mesozooplankton was due to veliger and appendicularian grazing. The importance of bivalve veligers might be seen in their grazing on seston particles that escape predation by copepods and on the amount of energy that is therefore directed from the water column to the benthos when larvae settle.

Description: Spatial and temporal variability in environmental factors can exert major influences on survival and growth of living organisms. However, in many key areas of fisheries science (e.g. growth, survival and recruitment determination), environmental heterogeneity is usually ignored because of insufficient environmental or fisheries data or lack of evidence that such heterogeneity impacts response variables. For the eastern Baltic Sea (ICES Subdivisions 25 to 32), we evaluated spatial and temporal differences in conditions affecting the survival of cod Gadus morhua L. eggs at survival on four distinct spawning sites within the assessment area. We intercalibrated ways of quantifying the volume of water ('reproductive volume') at each site where salinity, oxygen and temperature conditions permitted successful egg development. We have developed and compared a time series (1952 to 1996) of reproductive volumes among the areas to identify spatial differences. The results of 2 independent volume-estimation methods are comparable, indicating that highly significant differences exist among the sites, and that the westernmost spawning ground, Bornholm Basin, has on average the highest reproductive volume and the lowest variability among the 4 sites. These findings may be useful in evaluating how spatial and temporal variability in environmental conditions affect egg hatching success and possibly recruitment in the Baltic stock.

Description: Two submarine volcanoes (named Friday and Domingo) have been mapped and sampled to the west of the youngest island (Alexander Selkirk) in the Juan Fernandez chain, SE Pacific. Samples from the seamounts are fresh, highly vesicular olivine and plagioclase-phyric basanites. Their MgO contents lie between 7 and 4 wt.%. Major element variation trends, especially decreasing SiO2 with increasing MgO, cannot be explained by crystal fractionation, and suggest the influence of CO2 during partial melting. Highly incompatible element ratios in both Friday and Domingo magmas are identical, with the exception of ratios involving Th and Nb for which Domingo shows depletions. These depletions are coupled with depletions in Zr, Hf and Ca and enrichments in the heavy rare-earth elements and Al2O3. All these geochemical features can be explained if the Domingo magmas reacted with harzburgitic mantle materials during transit to the surface in a manner shown experimentally to occur during CO2-dominated kimberlite magmatism. The metasomatism results in the stabilisation of clinopyroxene, rutile and zircon which withhold the elements depleted at Domingo, and the breakdown of garnet which releases HREE and Al into the magmas. Magmas erupting from the large, more mature Friday edifice have traversed a mantle region already metasomatised during earlier stages of volcanism and so are not significantly modified during passage. The Juan Fernandez trace element patterns are similar to the low 87Sr/86Sr, high 143Nd/144Nd components in many Pacific hotspots and to the pattern suggested for recycled, altered, dehydrated oceanic crust, implying that such recycled crust is a common component in many hotspots. Isotopically, the Juan Fernandez magmas lie between the composition of prevalent mantle (PREMA) and HIMU.

Description: Symbiotic and pathogenic bacteria have in common that they live in or on host organisms or host cells. To make a successful living in eukaryotic hosts, bacteria must possess the traits to recognize a given host and establish adherence. When the bacterial location is internal or intracellular, they must further have the ability to invade, to establish a niche, and finally to multiply within a host. The underlying mechanisms which allow this form of existence show similarities between symbiotic and pathogenic bacteria. The final outcome, however, may result in a wide spectrum of consequences for the host ranging from the acquisition of novel metabolic pathways to damage or death. Despite the vastly different forms of interactions, symbiotic and pathogenic bacteria have in common that they are adapted to a particular environmental niche represented by the host organism or compartment thereof. This contribution reviews the evolutionary forces which have shaped the microbial-host interactions. Particular emphasis is placed on the genetic and molecular mechanisms that drive bacterial evolution in response to the selective pressures of the host environment.

Description: During the 1960s and 1970s the Baikalian amphipod Gmelinoides fasciatus (Stebbing) was intentionally introduced into more than 20 lakes and reservoirs outside its native range in Siberia and European Russia, in order to enhance fish production. Abilities of Gmelinoides to spread within the basins and to compete with native amphipods were neglected. In the European Russia this species successfully established in the Volga River basin, in such large lakes as Lake Ladoga, Lake Onega, Lake Peipsi, Lake Ilmen and their basins, and in the Neva Estuary (Baltic Sea). In most cases the native amphipods were completely replaced by Gmelinoides, and negative impact on other aquatic invertebrate species is also likely because direct predation by Gmelinoides. Studies of Gmelinoides biology, including experimental estimation of its salinity and temperature resistance, showed that this invasive amphipod tolerates wide range of environmental conditions and potentially is able to invade other parts of the Baltic Sea and inland waters within its basin.Considering intensive shipping activity in the Neva Estuary, and high densities of Gmelinoides in the St.Petersburg harbour area, introduction of this species into the North American Great Lakes and estuarine ecosystems with ballast waters of ships via existing invasion corridor is likely.