Optimal control: when redundancy matters

A new experiment provides support for optimal feedback control as a theoretical basis of how the motor system responds to perturbations in a context-dependent manner.     

Aspartic proteinases in fishes and aquatic invertebrates

1. The literature on molecular properties and physiological role of aspartic proteinases in fishes and aquatic invertebrates has been reviewed. 2. Pepsins have not been detected in invertebrates, and apparently cathepsin D, as well as other cathepsins, act both as digestive and lysosomal enzymes in many of these animals. The molecular properties of invertebrate cathepsin D correspond with cathepsin D in fishes and mammalians. 3. Fishes with a true stomach have pepsinogen secretion. Fish pepsins have higher pH optimum and are less stable in strong acid conditions than mammalian pepsins. They are very efficient at low temperatures, but less thermostable than mammalian pepsins. 4. Many fishes have two significantly different pepsins: Pepsin I and Pepsin II, which digest haemoglobin at a maximal rate in the pH ranges 3-4 and 2-3 respectively. Usually the pI of Pepsin I is in the range 6.5-7, whereas pI of Pepsin II is about 4. 5. Fish Pepsin I and cathepsin D have very similar molecular properties, and a hypothesis proposing that cathepsin D is the ancestor enzyme of aspartic proteinases in higher animals is presented.     

Cyst ornamentation in aquatic invertebrates: a defence against egg-predation

Hydrobiologia - Eggs, including encysted embryos (cysts) of aquatic invertebrates may not only be thick-walled, but also provided with various external ornamentations such as spines and...     

Protein N-terminal acetyltransferases: when the start matters

The majority of eukaryotic proteins are subjected to N-terminal acetylation (Nt-acetylation), catalysed by N-terminal acetyltransferases (NATs). Recently, the structure of an NAT-peptide complex was determined, and detailed proteome-wide Nt-acetylation patterns were revealed. Furthermore, Nt-acetylation just emerged as a multifunctional regulator, acting as a protein degradation signal, an inhibitor of endoplasmic reticulum (ER) translocation, and a mediator of protein complex formation. Nt-acetylation is regulated by acetyl-coenzyme A (Ac-CoA) levels, and thereby links metabolic cell states to cell death. The essentiality of NATs in humans is stressed by the recent discovery of a human hereditary lethal disease caused by a mutation in an NAT gene. Here, we discuss how these recent findings shed light on NATs as major protein regulators and key cellular players.     

A study of the hatching process in aquatic invertebrates

Summary The hatching process was observed in eggs of Notonecta melaena. A thick outer egg membrane ruptured at the cephalic end by pressure from within, exerted by the expansion of an inner egg membrane which forms a blister over the head. The osmotic nature of this expansion is demonstrated. The pronymph then drank water and its head pushed forward. At the same time, the blister membrane broke. The pronymph then emerged by a combination of a swelling of its body and a worm-like expansion and contraction in the abdominal region. The body swelled from a copious ingestion and absorption of water. The appendages did not participate in any way during hatching. At the termination of the emergence, a second inner membrane was ruptured. Shortly thereafter the pronymph underwent an ecdysis and swam away as a fully formed nymph.The eggs of Ranatra absona hatched in a somewhat similar manner, but the blister membrane was broken only after the head pushed against it. Also, the second inner membrane was ruptured long before the emergence of the nymph had been completed. In addition, there was no pronymphal stage and no ecdysis immediately after emergence.The eggs of Amnicola (?) hydrobioides are described. They were laid at an advanced stage of development. The young were very small (ca. 350 × 270 µ) and were surrounded by single egg membranes whose diameters were about % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaaGOmaKaaGm% aaliaabaGaaGymaaqaaiaaikdaaaaaaa!385B!\[2{\raise0.7ex\hbox{$1$} \!\mathord{\left/ {\vphantom {1 2}}\right.\kern-\nulldelimiterspace}\!\lower0.7ex\hbox{$2$}}\] times that of the young. Hatching was through a mechanical tearing motion by the foot and proboscis, but the tearing reflex set in only after the egg membrane collapsed. Evidence is presented which suggests that the collapse was caused by the enzymatic softening of the membrane.

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Sumario Eclosión se observa en los huevos de Notonecta melaena. La membrana exterior del huevo se rompe en la extremidad cefálica por presión desde el interior. Esta presión se deriva de la expansión de una membrana interior, que forma sobre la cabeza una ampolla. Es demonstrado que ésta expansión es de tipo osmótico.. Entoncces la proninfa bebe agua y empuja hacia adelante. Al mismo tiempo la membrana la de ampolla se rompe. Entonces sale la proninfa por combinación la de hinchazón del cuerpo y la expansón y abreviatura del abdomen,, como de la un gusano. El cuerpo se hincha debido a la gran imbibición de agua. Las patas no participan en algunas de estas acciones. Al final de la eclosión la segunda membrana interior se rompe. Poco tiempo despues la proninfa vierte su esqueleto exterior y nada como una ninfa verdadera.Los huevos de Ranatra absona se rompen de una manera semejante, pero la membrana dela ampolla se rompe despures de que la cabeza la ha empujado. Además, la segunda membrana interior se rompe despues de que la ninfa ha salido completamente. Tampoco hay etapa proninfal y no hay muda de esqueleto exterior immediatemente despues de la salida.Los huevos de Amnicola (?) hydroboides han sido descritos. Ellos son puestos en un estado avanzado de desarrollo. Los jóvenes son muy pequeños (ca. 350 × 270 µ) y están circundados por membranas únicas que tienen diámetros cerca de% MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaaGOmaKaaGm% aaliaabaGaaGymaaqaaiaaikdaaaaaaa!385B!\[2{\raise0.7ex\hbox{$1$} \!\mathord{\left/ {\vphantom {1 2}}\right.\kern-\nulldelimiterspace}\!\lower0.7ex\hbox{$2$}}\] veces más que los de los jóvenes. Eclosión es por causa de una rotura mecánica de la membrana por accion del pie y probóscide, pero la acción refleja de rotura occure solamente despues de un hundimiento de la membrana del huevo. Se han presentado evidencias que indican que este hundimiente es ocasionado por un ablandamiento enzimático de la membrana.

     

Body mass and excretion of phosphorus in aquatic invertebrates

Empirical materials on the dependence of the intensity of mineral phosphorus excretion (Ex) on the body mass (W) in invertebrates are summarized. The parameters of the average dependence of Ex on W in animals at 20°C are determined. The main factors that influence the parameters of this dependence are discussed. It is shown that the decrease of Ex with an increase of W in animals is, as a rule, more significant compared with the decrease in the intensity of metabolism.     

A rapid,non-stressing technique for measuring growth in Anostraca and other delicate,medium-sized aquatic invertebrates

A rapid, non-stressing technique for measuring growth in Anostraca and other delicate, medium-sized aquatic invertebrates     

Invertebrate eggs can fly: evidence of waterfowl-mediated gene flow in aquatic invertebrates

Waterfowl often have been assumed to disperse freshwater aquatic organisms between isolated wetlands, but no one has analyzed the impact of this transport on the population structure of aquatic organisms. For three cladocerans (Daphnia ambigua, Daphnia laevis, and Sida crystallina) and one bryozoan (Cristatella mucedo), we estimated the genetic distances between populations across North America using sequences of several mitochondrial DNA genes and genotypic frequencies at allozyme and microsatellite loci. Waterfowl movements across North America (estimated from band recovery data) explained a significant proportion of the gene flow occurring between populations across the continent for three of the four species, even after controlling for geographic distances between localities. The fourth species, S. crystallina, has propagules less likely to survive desiccation or ingestion by birds. Differences in the capacity to exploit bird-mediated transport are likely to have important consequences for the ecology of aquatic communities and the spread of invasive species.     

Upstream-downstream movements of aquatic invertebrates in a Rocky Mountain stream

Simultaneous collections of drift and organisms moving either upstream or downstream in association with the substrate were made using a specially designed sampler. Samples were taken in a diel series along a transect across the study riffle of a Colorado foothills stream on six dates over an annual cycle. In addition to longitudinal movements, taxonomic composition and diel periodicity were evaluated. The insect-dominated fauna showed a net downstream displacement. Only the caddisflies Helicopsyche borealis and Hesperophylax occidentalis exhibited net upstream movement, primarily a result of low drift frequencies. The taxonomic composition of moving invertebrates differed from that of the benthos. Drift resembled downstream moving substrate-associated invertebrates in composition, but differed from that of the upstream directed fauna. Taxa collectively exhibited four types of diel patterns: 1) similar downstream (drift and substrate-associated movements) patterns, which generally differed from the upstream pattern; 2) similar benthic (upstream and downstream) patterns, which differed from that of drift; 3) aperiodic patterns; and 4) independent patterns for each type of directional movement. Analysis of size classes based on head capsule width for the mayfly Baetis tricaudatus showed significantly smaller size in stationary individuals compared with moving individuals in the population and revealed that nymphs moving during the day were smaller than those moving at night.     

Consumption of aquatic subsidies by soil invertebrates in coastal ecosystems

Routes of aquatic allochthonous inputs (aquatic subsidies) to detrital food webs are studied, as is the effect of aquatic subsidies on the functional and taxonomic structure of soil invertebrate communities in coastal ecosystems. The study took place in the coastal zone of an oxbow lake of the Pra River in the Oka Reserve. The results indicate a strong dependence of soil animals in the coastal habitats on aquatic subsidies. Isotopic analysis shows that aquatic resources enter soil food webs not only via predators feeding on flying insects or aquatic prey, but also via saprophages decomposing organic debris of aquatic origin. The contribution of aquatic subsidies to the energy balance of soil invertebrates decreases rapidly with increasing distance from the lake. The fraction of aquatic carbon in tissues of collembolans and saprophages is negligible already a few meters from the water edge. The dependence of predatory invertebrates on aquatic resources can be traced at somewhat greater distance (tens of meters).     

Physiological and molecular biological mechanisms underlying diapause in aquatic invertebrates

The review considers the published data, as well as its own, which demonstrate the abundance and evolutionary conservation of the mechanism of diapause in invertebrates. The ecological reasons for the emergence of diapause in life cycles of hydrobionts are analyzed. The specific physiological features of invertebrate diapausing organisms and the hormonal control of diapause are briefed. The molecular genetic mechanism of diapause is demonstrated by the example of a model species, Caenorhabditis elegans. Recent fundamental discoveries in molecular genetics related to the joint effect of genes and environmental factors on the basic metabolism, choice between the development-diapause alternative, and many other seasonal adaptations in multicellular organisms are discussed. The near discovery of the functional role of daf genes in hydrobionts is postulated. These studies will lead to a deeper understanding of the fine mechanism that underlies photoperiodism and the wider application of diapause phenomenon in theory and practice.     

Activity traps and the corer: complementary methods for sampling aquatic invertebrates

We compared the picture of aquatic invertebrate fauna given by three types of sampling methods: the corer as well as bottom and mid-water activity traps. The corer mainly caught benthic animals (89%), the most numerous groups of which were chironomids and sphaerids. Nekton was more abundant in activity traps (77% in bottom and 63% in mid-water), the most numerous groups were Cladocera and water mites. The size distributions in catch of the corer and the activity traps differed but there was no difference between the two types of activity traps. In activity traps, individuals of the smallest size class were most abundant, wheras animals of the second smallest size class were most numerous in the corer. We suggest that activity traps and the corer could be used as complementary methods to sample aquatic invertebrate communities.     

Protecting biodiversity when money matters: maximizing return on investment

Background

Conventional wisdom identifies biodiversity hotspots as priorities for conservation investment because they capture dense concentrations of species. However, density of species does not necessarily imply conservation ‘efficiency’. Here we explicitly consider conservation efficiency in terms of species protected per dollar invested.

Methodology/Principal Findings

We apply a dynamic return on investment approach to a global biome and compare it with three alternate priority setting approaches and a random allocation of funding. After twenty years of acquiring habitat, the return on investment approach protects between 32% and 69% more species compared to the other priority setting approaches. To correct for potential inefficiencies of protecting the same species multiple times we account for the complementarity of species, protecting up to three times more distinct vertebrate species than alternate approaches.

Conclusions/Significance

Incorporating costs in a return on investment framework expands priorities to include areas not traditionally highlighted as priorities based on conventional irreplaceability and vulnerability approaches.     

Seasonality of aquatic invertebrates in low-latitude and Southern Hemisphere inland waters

The seasonality of freshwater aquatic invertebrates in Southern Hemisphere and low-latitude inland waters in Africa, Australasia and South America is reviewed. Fauna from the tropics to temperate latitudes manifests some seasonality, the amplitude of which tends to increase, albeit inconsistently, with latitude. The wide diversity of habitats considered, and deficiencies in the data preclude generalizations about patterns and magnitude of seasonal response, which principally reflect system-specific events and interactions. For example, zooplankton declined after mixing events in some stratified systems, but increased in others, food availability being implicated. Zooplankton was most abundant in summer in some stratifying systems, and in winter in others, while in most non-stratifying systems, it was most abundant around the winter solstice, and in several, declined during the rainy season.Seasonality of the zoobenthos was frequently linked to hydrological events such as fluctuations in water level which potentially influence food and habitat availability. Seasonal anaerobiosis in shallow sheltered waters and deeper hypolimnia imposes spatio-temporal restrictions on the benthic fauna. Low oxygen solubility, rapid oxygen depletion and decomposition of organic food matter at the elevated temperatures are probably significant influences. Life histories of Southern Hemisphere stream fauna appear seasonally flexible and opportunistic by contrast with the apparently synchronous cycles exhibited by north temperate representatives. Such flexibility may be selective both in respect of climatic unpredictability and equability.The influences of predation and resource availability upon seasonal dynamics remain to be explored more fully, particularly in aquatic ecosystems in warm, arid regions which lack the climatic predictability of the cooler, humid, temperate zones.     

Effect of aluminum and iron on lipid metabolism in aquatic invertebrates

Methods of thin-layer, gas-liquid, and liquid chromatography were applied to the study of the effect of various concentrations of aluminum and iron salts on the contents of phospholipids, cholesterol, and fatty acids in the aquatic invertebrate Hydropsyche contubernalis L. (Trichoptera). It was found that the effect of the metals under study on lipid contents in living organisms depended on the composition of the aqueous medium and concentrations of the metals. Aluminum and iron altered the value of the cholesterol-to-phospholipid molar ratio. In the absence of lethal effects, this was indicative of attempts to switch adaptational biochemical mechanisms to stabilize cellular structures.     

Effect of aluminum and iron on lipid metabolism in aquatic invertebrates

Methods of thin-layer, gas-liquid, and liquid chromatography were applied to the study of the effect of various concentrations of aluminum and iron salts on the contents of phospholipids, cholesterol, and fatty acids in the aquatic invertebrate Hydropsyche contubernalis L. (Trichoptera). It was found that the effect of the metals under study on lipid contents in living organisms depended on the composition of the aqueous medium and concentrations of the metals. Aluminum and iron altered the value of the cholesterol-to-phospholipid molar ratio. In the absence of lethal effects, this was indicative of attempts to switch adaptational biochemical mechanisms to stabilize cellular structures.Translated from Prikladnaya Biokhimiya i Mikrobiologiya, Vol. 41, No. 2, 2005, pp. 220–227.Original Russian Text Copyright © 2005 by Regerand, Nefedova, Nemova, Ruokolainen, Toivonen, Dubrovina, Vuori, Markova.     

Assessing the impact of ionizing radiation on aquatic invertebrates: a critical review

There is growing scientific, regulatory and public concern over anthropogenic input of radionuclides to the aquatic environment, especially given the issues surrounding existing nuclear waste, future energy demand and past or potential nuclear accidents. A change in the approach to how we protect the environment from ionizing radiation has also underlined the importance of assessing its impact on nonhuman biota. This review presents a thorough and critical examination of the available information on the effects of ionizing radiation on aquatic invertebrates, which constitute approximately 90% of extant life on the planet and play vital roles in ecosystem functioning. The aim of the review was to assess the progress made so far, addressing any concerns and identifying the knowledge gaps in the field. The critical analysis of the available information included determining yearly publications in the field, qualities of radiation used, group(s) of animals studied, and levels of biological organization at which effects were examined. The overwhelming conclusion from analysis of the available information is that more data are needed in almost every area. However, in light of the current priorities in human and environmental health, and considering regulatory developments, the following are areas of particular interest for future research on the effects of ionizing radiation on nonhuman biota in general and aquatic invertebrates in particular: (1) studies that use end points across multiple levels of biological organization, including an ecosystem level approach where appropriate, (2) multiple species studies that produce comparable data across phylogenetic groups, and (3) determination of the modifying (i.e. antagonistic, additive or synergistic) effects of biotic and abiotic factors on the impact of ionizing radiation. It is essential that all of these issues are examined in the context of well-defined radiation exposure and total doses received and consider the life stages and life span of the species studied. The review also provides future directions for studies in this stimulating area of research to protect human and environmental health.     

Multidrug therapy and evolution of antibiotic resistance: when order matters

The evolution of drug resistance among pathogenic bacteria has led public health workers to rely increasingly on multidrug therapy to treat infections. Here, we compare the efficacy of combination therapy (i.e., using two antibiotics simultaneously) and sequential therapy (i.e., switching two antibiotics) in minimizing the evolution of multidrug resistance. Using in vitro experiments, we show that the sequential use of two antibiotics against Pseudomonas aeruginosa can slow down the evolution of multiple-drug resistance when the two antibiotics are used in a specific order. A simple population dynamics model reveals that using an antibiotic associated with high costs of resistance first minimizes the chance of multidrug resistance evolution during sequential therapy under limited mutation supply rate. As well as presenting a novel approach to multidrug therapy, this work shows that costs of resistance not only influences the persistence of antibiotic-resistant bacteria but also plays an important role in the emergence of resistance.