Observations on the influence of external factors on the duration of the embryonic development and on the molting rhythm of Cyclops vicinus. [Translation from: Oecologia 7, 342-355, 1971.]

Investigations on the control of the embryonic and post-embryonic development of arthropods have formed an intensively studied field of zoological research for a long time, Here in especially favourable cases the causal chain from the operation of external factors on the influence of physiological mechanisms, eg. of the hormone variety, is known right through to its primary influences. A comparative approach to the relevant questions was in the main only made in the case of the insects. For crustacea , investigations are available almost exclusively only for the malacostraca. This study examines the influence of the factors of temperature and photoperiod on the entire development of Cyclops vicinus. Tests were made on whether the light-darkness change serves as a regulator for a possible existing molting rhythm - a question which for the entire arthropods has been settled only very rarely. The basic material for the cultures that were examined originates from Lake Constance.

The ecological impact of different mechanisms of chronic sub-lethal toxicity on feeding and respiratory physiology

Sub-lethal toxicity tests, such as the scope-for-growth test, reveal simple relationships between measures of contaminant concentration and effect on respiratory and feeding physiology. Simple models are presented to investigate the potential impact of different mechanisms of chronic sub-lethal toxicity on these physiological processes. Since environmental quality is variable, even in unimpacted environments, toxicants may have differentially greater impacts in poor compared to higher quality environments. The models illustrate the implications of different degrees and mechanisms of toxicity in response to variability in the quality of the feeding environment, and variability in standard metabolic rate. The models suggest that the relationships between measured degrees of toxic stress, and the maintenance ration required to maintain zero scope-for-growth, may be highly nonlinear. In addition it may be possible to define critical levels of sub-lethal toxic effect above which no environment is of sufficient quality to permit prolonged survival.

Behavioral and Physiological Responses to Light by the Sea Anemone Anthopleura elegantissima as Related to its Algal Endosymbionts

The endosymbiosis of algae with invertebrates may be viewed with at least two major orientations. On the one hand, one may focus on the plant and animal as essentially separate organisms living together, as the word symbiosis states. The products which are exchanged between the plant and animal and the effects of the association on either partner are then of particular interest. On the other hand, one may consider the partnership as an entity, and attempt to investigate the physiology, behavior, etc. of the symbiotic association, observing what differences may appear between the "plant-animal" and analogous non-symbiotic organisms. It is the second approach which I have tried to take in this thesis. I have concentrated on some effects of light on symbiotic and aposymbiotic sea anemones of the species Anthopleura elegantissima, particularly with respect to pigmentation and several types of behavior.

Environmentally induced physiological responses that determine fish survival and distribution: a review

Limitation to an aqueous habitat is the most fundamental physiological constraint imposed upon fish, phrases such as 'like a fish of water', convey our acceptance of the general unsuitability of fish for terrestrial existence. The constraints that restrict fish to an aquatic habitat relate to respiration, acid-base regulation, nitrogenous excretion, water balance and ionic regulation. A fish not adapted for an amphibious lifestyle when removed from water, becomes hypoxic and hypercapnic and soon succumbs to respiratory acidosis because the problem of excretion of H super(+) and C0 sub(2) are more immediate than lack of oxygen. This happen because fish gills collapse in air, while the ventilator arrangements that moves an incompressible medium (water) oven them become ineffective

Kurzinformation zum EU - Projekt: "Mechanisms influencing long term trends in reproductive success and recruitment of Baltic cod : implications for fisheries management"

In July 1994 an internationally coordinated and EU financed multidisciplinary research project about Baltic cod recruitment was started. The primary goals are to identify and describe dominant biotic and abiotic processes affecting the developmental success of early stages and the maturation of cod in the Central Baltic, to incorporate these processes into recruitment models in order to enhance prediction of future stock fluctuations due to environmental pertubations, species interactions and fisheries management directives as a prerequisite for an integrated fish stock assessment in the Central Baltic and to evaluate the feasibility and possible effects of stock enhancement programs on stock and recruitment and providing the biological basis for assessing their economic value.

The importance of temporary waters for Diptera (true-flies)

Flies are the largest order of wetland insects in Britain. Of 6668 known species, larvae of at least 1138 are considered to be aquatic while a large number, perhaps as many again, are associated with wetlands. Despite this abundance of species they have been neglected in nearly all studies of temporary ponds. The prerequisites that are usually quoted for surviving in temporary pools are an ability to reach maturity before the system dries out, physiological or behavioural mechanisms to survive the dry period, and an ability to recolonise. Larvae of many British wetland Diptera have these features, which should enable them to develop and survive in temporary ponds. Some examples are considered in this article, with brief comments on adaptations in insects from other geographical regions.

Sensitivity of sturgeons to environmental hypoxia: a review of physiological and ecological evidence

In this essay, three lines of evidence are developed that sturgeons in the Chesapeake Bay and elsewhere are unusually sensitive to hypoxic conditions: 1. In comparison to other fishes,sturgeons have a limited behavioral and physiological capacity to respond to hypoxia. Basal metabolism, growth, feeding rate, and survival are sensitive to changes in oxygen level, which may indicate a relatively poor ability of sturgeons to oxyregulate. 2. During summertime, temperatures >20°C amplify the effect of hypoxia on sturgeons and other fishes due to a temperature oxygen "squeeze" (Coutant 1987). In bottom waters, this interaction results in substantial reduction of habitat; in dry years, sturgeon nursery habitats in the Chesapeake Bay may be particularly reduced or even eliminated. 3. While evidence for population level effects due to hypoxia is circumstantial, there are corresponding trends between the absence of Atlantic sturgeon reproduction in estuaries like the Chesapeake Bay where summertime hypoxia predominates on a system-wide scale. Also, the recent and dramatic recovery of shortnose sturgeon in the Hudson River (4-bid increase in abundance from 1980 to1995) may have been stimulated by improvement of a large portion of the nursery habitat that was restored from hypoxia to normoxia during the period 1973-1978.

Investigations of certain eco-physiological characteristics of the broad and long-pincered crayfish in connection with their interspecific relationships. [Translation from: Lietuvas TSR Mokslu Akademijos Darbai, C Serija 2(40), 279-286, 1966.]

The results are described of eco-physiological investigations of the broad-pincered (Astacus astacus L.J.) crayfish and the long-pincered (Astacus astacus Esch.) crayfish, conducted in 1963—64 in the Institute of Zoology and Parasitology of the Academy of Science of the Lithuanian SSR, for the purpose of studying the interspecific relationship of these two species. In the course of the investigation were determined: the influence of the temperature of the environment on the consumption of oxygen by full grown individuals of both species and on the respiratory movements of the scaphognathites, the threshold temperatures and the saturation of the water by oxygen, the diel activity in the winter period.

Observations on the physiological development of trout eggs [Translation from: Roux. Arch. f. Entwicklungsmechanik der Organismen, 114. 771, 1929]

The osmotic pressure of the perivitelline fluid and the yolk of trout (Salmo trutta) eggs were measured separately by the Drucker-Schrein method. The permeability of the egg membrane and the variations in the osmotic pressure of the eggs when placed in salt solutions were also investigated.

Physiological aspects of the life cycle of the river lamprey, Lampetra fluviatilis L

The life cycle of the river lamprey, L. fluviatilis, is reviewed. The larval lamprey, or ammocoete, is a blind, filter-feeding animal, which normally lies concealed in the silt deposits of streams and rivers. After a period of 3-5 years in fresh water the ammocoete undergoes a metamorphosis in the summer months into a sexually immature, non-feeding stage known as the macrophthalia, which is active. This stage migrates downstream in late winter. It adopts a parasitic existence, in intertidal areas. After 18 months it returns to spawn in fresh water, after a final freshwater stage lasting up to 9 months. The river lamprey dies within a few days after the spawning period of 3-4 weeks, and none survive to spawn the following year.

Phytoplankton periodicity: its motivation, mechanisms and manipulation

This review summarizes some recent work to find a generalized explanation of phytoplankton periodicity in lakes. Much of the observational and experimental evidence is drawn from work centred on the large enclosures (Lund Tubes) installed in Blelham Tarn, English Lake District. Observations on the phytoplankton in the tubes are related to the periodic changes that occur in natural lakes and it is suggested that such changes have common patterns, that they are due to common causes, that they are affected by similar processes and that they are therefore predictable and, potentially, manipulable.

Physiological ecology of the ciliated protozoon Loxodes

Loxodes faces special problems in living close to the oxic-anoxic boundary. In tightly-stratified ponds like Priest Pot its optimum environment may be quite narrow and it can be displaced by the slightest turbulence. Loxodes cannot sense an O sub(2) gradient directly but its ability to perceive gravity allows it to make relatively long vertical migrations. It is also sensitive to light and oxygen and it uses these environmental cues to modulate the parameters of its random motility: in the dark, it aggregates at a low O sub(2) tension and in bright light it aggregates in anoxic water. The oxic-anoxic boundary is also a zone where O sub(2) may be a scarce and transient resource, but Loxodes) can switch to nitrate respiration and exploit the pool of nitrate that often exists close to the base of the oxycline.

Physiological Determinants of Invasive Success Linking Distribution Patterns to Metabolic Physiology in Native and Invasive Blue Mussels (genus Mytilus)

In the early 20th century, a blue mussel species from the Mediterranean invaded the California coast and subsequently out-competed the native species south of Monterey Bay. Like other invasive species, Mytilus galloprovincialis has physiological traits that make it successful in habitats formerly occupied by the native M. trossulus, namely its adaptation to warm sea surface temperatures. This study looks at the current genotype distributions and enzymatic activities of field-acclimatized mussels within the hybrid zone where the species co-occur as well as mussels that have been acclimated for four weeks to different temperature and salinity conditions. In the field-acclimatized and laboratory-acclimated mussels, the native species exhibited significantly higher enzyme rates, which may reflect an evolutionary adaptation to compensate to low habitat temperatures. Indeed, the results of the laboratory acclimation indicate that these differences are genetically based. Whether an acclimation capacity exists may require even longer-term acclimation to different temperatures. Current findings suggest that the further spread of the invasive species is likely to be governed in large measure by the potentially counteracting effects of rising temperatures, which would favor the northerly spread of M. galloprovincialis, and increased winter precipitation, which would favor the persistence of M. trossulus. However, the success of M. galloprovincialis during acclimation to ‘dilute’ salinity (25 ppt) suggests that the invasive species can tolerate a greater salinity range than previously thought. Thus, further investigation is needed to build a comprehensive predictive model of the movement of M. galloprovincialis and the hybrid zone along the California coast.

Relationship between abundance of juvenile rockfishes (Sebastes spp.) and environmental variables documented off northern California and potential mechanisms for the covariation

We estimated annual abundance of juvenile blue (Sebastes mystinus), yellowtail (S. f lavidus), and black (S. melanops) rockfish off northern California over 21 years and evaluated the relationship of abundance to oceanographic variables (sea level anomaly, nearshore temperature, and offshore Ekman transport). Although mean annual abundance was highly variable (0.01−181 fish/minute), trends were similar for the three species. Sea level anomaly and nearshore temperature had the strongest relationship with interannual variation in rockfish abundance, and offshore Ekman transport did not correlate with abundance. Oceanographic events occurring in February and March (i.e., during the larval stage) had the strongest relationship with juvenile abundance, which indicates that year-class strength is determined during the larval stage. Also of note, the annual abundance of juvenile yellowtail rockfish was positively correlated with year-class strength of adult yellowtail rockfish; this finding would indicate the importance of studying juvenile abundance surveys for management purposes.

Some physiological effects of two algal epiphytes on the surfgrass Phyllospadix torreyi Wats.

Measurement of the physiological effects of the red algal epiphytes Smithora naiadum (Anders.) Hollenberg and Melobesia mediocris (Fosl.) Setch. and Mason on Phyllospadix torreyi Wats. were made near Hopkins Marine Station, Pacific Grove, California. Field studies revealed a significant influence of these epiphytes on both the breakage incidence and length, with that of Melobesia being the most pronounced. Analysis of the photosynthetic rate of the seagrass shows a decrease in the photosynthetic maxima in both epiphytized samples at a light saturating intensity. Under light limiting conditions, an increase in photosynthetic efficiency and a change in chlorophyll a composition in both epiphytized sample types suggest an adaptive mechanism similiar to those found in terrestrial and aquatic shade plants.