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PubMed1980

Amines and a peptide as neurohormones in lobsters: actions on neuromuscular preparations and preliminary behavioural studies.

In this communication we report that four substances, thought to function as neurohormones in Crustacea, all produce long-term changes in the physiological properties of lobster opener muscle preparations. The substances are the amines, octopamine, serotonin and dopamine, and the peptide, proctolin. The actions of these substances are superimposed on the normal synaptic apparatus that utilizes the amino acids GABA and glutamate (probably) as the inhibitory and excitatory neurotransmitter compounds. Serotonin acts on excitatory and inhibitory nerve endings to facilitate transmitter release and directly on muscle fibres to produce a contracture and to induce the appearance of Ca2+ action potentials. The latter two actions of serotonin are shared by proctolin and octopamine as well. Dopamine, on the other hand, relaxes muscle baseline tension. The mechanism of action of these substances at their target site (or sites) has been explored with electrophysiological and biochemical techniques and the results will be presented. In addition preliminary behavioural experiments have been carried out with serotonin and octopamine. These substances produce opposite postures when injected into lobsters. The amines act on central ganglia to produce these effects where they cause a programmed readout of firing of neurones that will produce either a flexed posture (serotonin) or an extended posture (octopamine).

Action Potentials↗
PubMed1998

A very-high-density lipoprotein with clotting ability from hemolymph of sand crayfish, Ibacus ciliatus.

A very-high-density lipoprotein (VHDL) with a density of 1.27-1.29 g/ml was the most abundant lipoprotein in the hemolymph of the sand crayfish Ibacus ciliatus. The VHDL isolated by a density gradient ultracentrifugation consisted of 94% protein and 6% lipid reflecting its high density, and phospholipid was a predominant lipid component. The VHDL had an apolipoprotein of molecular mass 195 kDa and its N-terminal amino acid sequence was identified as follows: LQPGLEYQYRYNGRVAA. This sequence was similar to those of clotting proteins from the spiny lobster Panulirus interruptus and the freshwater crayfish Pacifastacus leniusculus. Transglutaminase and Ca2+ also induced the VHDL to clot. Considering large amounts of VHDL in the hemolymph of sand crayfish, the VHDL not only functions as lipid carrier but plays an important role in the defense process of crustacea.

Amino Acid Sequence↗
PubMed2006

Empirical support for optimal virulence in a castrating parasite.

The trade-off hypothesis for the evolution of virulence predicts that parasite transmission stage production and host exploitation are balanced such that lifetime transmission success (LTS) is maximised. However, the experimental evidence for this prediction is weak, mainly because LTS, which indicates parasite fitness, has been difficult to measure. For castrating parasites, this simple model has been modified to take into account that parasites convert host reproductive resources into transmission stages. Parasites that kill the host too early will hardly benefit from these resources, while postponing the killing of the host results in diminished returns. As predicted from optimality models, a parasite inducing castration should therefore castrate early, but show intermediate levels of virulence, where virulence is measured as time to host killing. We studied virulence in an experimental system where a bacterial parasite castrates its host and produces spores that are not released until after host death. This permits estimating the LTS of the parasite, which can then be related to its virulence. We exposed replicate individual Daphnia magna (Crustacea) of one host clone to the same amount of bacterial spores and followed individuals until their death. We found that the parasite shows strong variation in the time to kill its host and that transmission stage production peaks at an intermediate level of virulence. A further experiment tested for the genetic basis of variation in virulence by comparing survival curves of daphniids infected with parasite spores obtained from early killing versus late killing infections. Hosts infected with early killer spores had a significantly higher death rate as compared to those infected with late killers, indicating that variation in time to death was at least in part caused by genetic differences among parasites. We speculate that the clear peak in lifetime reproductive success at intermediate killing times may be caused by the exceptionally strong physiological trade-off between host and parasite reproduction. This is the first experimental study to demonstrate that the production of propagules is highest at intermediate levels of virulence and that parasite genetic variability is available to drive the evolution of virulence in this system.

Animals↗
PubMed1989

Glycogenolysis during recovery from muscular work. The time course of phosphorylase activity is dependent on Pi concentration in the abdominal muscle of the shrimp Crangon crangon.

1) Glycogen is degraded in the abdominal muscle of the shrimp Crangon crangon (Decapoda, Crustacea) during the recovery period following work. The regulation of post-exercise glycogen breakdown and the properties of glycogen phosphorylase (EC 2.4.1.1) have been studied: 2) Glycogen phosphorylase exists as unphosphorylated b-form and phosphorylated a-form, the latter contains 1 molecule phosphate/subunit. Both forms of phosphorylase are dimers, isoenzymes have not been detected. 3) The purified b-form is inactive in absence of AMP and has very low affinities for AMP and Pi. For half-maximum activation 0.33 +/- 0.04 mM AMP is necessary, and the Km-value for Pi at 1 mM AMP is 48 +/- 5 mM. IMP does not affect the activity of the b-form. 4) The a-form is active without effectors, its Km-value for Pi is 5.3 +/- 1.5 mM. The proportion of phosphorylase a increases in vivo, from about 25% at rest, to approximately 90% upon work and remains at this high level during the first minutes of recovery. 5) It is concluded that the glycogenolytic flux in the abdominal muscle of the shrimp even during post-exercise periods depends on the level of the a-form the activity of which is restricted in time and extent by the cytoplasmic Pi concentration (Kamp, G. & Juretschke, H. P. (1987) Biochim. Biophys. Acta 929, 121-127).

Adenosine Monophosphate↗
PubMed2004

Serotonin enhances the resistance reflex of the locomotor network of the crayfish through multiple modulatory effects that act cooperatively.

Serotonin (5HT) is an endogenous amine that modifies posture in crustacea. Here, we examined the mechanisms of action of 5HT on the resistance reflex in crayfish legs. This reflex, which counteracts movements imposed on a limb, is based on a negative feedback system formed by proprioceptors that sense joint angle movements and activate opposing motoneurons. We performed intracellular recordings from depressor motoneurons while repetitively stretching and releasing a leg joint proprioceptor in a resting in vitro preparation (i.e., a preparation that lacks spontaneous rhythmic activity). 5HT increased the amplitude of the depolarization during the release phase of the proprioceptor (corresponding to an upward movement of the leg) and the discharge frequency of the motoneurons. The 5HT-induced increase in the resistance reflex is caused, to a large extent, by polysynaptic pathways because it was very attenuated in the presence of high divalent cation solution. In addition to this activation of the polysynaptic pathways, 5HT also has postsynaptic effects that enhance the resistance reflex. 5HT causes a tonic depolarization, as well as an increase in the time constant and input resistance of motoneurons. We developed a simple mathematical model to describe the integrative properties of the motoneurons. The conclusion of this study is that the input frequency and the decay time constant of the EPSPs interact in such a way that small simultaneous changes in these parameters can cause a large effect on summation. Therefore, the conjunction of presynaptic and postsynaptic changes produces a strong cooperative effect on the resistance reflex response.

Animals↗
PubMed2001

Food resource utilization of the skates Rioraja agassizii (Müller & Henle, 1841) and Psammobatis extenta (Garman, 1913) on the continental shelf off Ubatuba, South-eastern Brazil.

The feeding habits of Rioraja agassizii (syn. Raja agassizii) and Psammobatis extenta (syn. Psammobatis glansdissimilis) of the South-eastern Brazilian coast were studied by means of stomach content analysis. The samples were obtained on eight seasonal oceanographic cruises, carried out between October 1985 and July 1987. The importance of each food item was evaluated on the basis of the Index of Relative Importance and the feeding similarity by Percentage of Similarity. The results indicated that both species are benthic feeders, preying mainly on Crustacea, especially Amphipoda, Caridea and Brachyura. Teleostei were also important for R. agassizii. Seasonal variation of the diet seems to be associated with the availability of the prey, whose distribution and abundance are related to the dynamics of the water masses of the region. Juveniles and adults of P. extenta exploited the same resources while juveniles and adults of R. agassizii presented low diet similarity during most of the year. Caridea were an important food for all length classes of R. agassizii, while Amphipoda were for smaller specimens, and Teleostei for larger ones. The feeding overlap between the two species was higher during autumn 1986, winter 1986 and winter 1987.

Animals↗
PubMed2003

Changes in soft-bottom macrobenthic assemblages after a sulphuric acid spill in the Rio Grande Harbor (RS, Brazil).

The structure of macrobenthic assemblages in Rio Grande Harbor was analyzed during and after a sulphuric acid spill in August 1988. Five stations were sampled four times between September 1988 and March 1999. At each station, three samples were taken using a van Veen grab (0.078 m2). A total of 22 taxa were collected including Crustacea (9 spp.), Polychaeta (7 spp.), Mollusca (3 spp.), Phoronida (1 sp.), Nemertinea (1 sp.), and Plathyelminthea (1 sp.). The macrobenthic assemblages suffered different impacts depending on station location and time: 1) immediate impact, i.e., during acid discharge, as at the station nearest (250 m) the acid spill source; 2) impact some time after the discharge, as at the station 500 m downstream from the acid spill source; and 3) absence of direct impact on the remaining sampling points, on the discharge area outer limit. The macrobenthic assemblage recovered six months after the sulphuric acid spill.

Accidents↗
PubMed2003

Ecology of a stream from upper Paraná River basin inhabited by Aspidoras fuscoguttatus Nijssen & Isbrücker, 1976 (Siluriformes, Callichthyidae).

Most information on catfishes of the genus Aspidoras has focused species kept in aquaria, in non-natural conditions. Biotic and abiotic parameters of environment inhabited by Aspidoras fuscoguttatus, associated ichthyofauna, as well as strategies involved in the successful occupation of different microhabitats in a first order stream, located in São José do Rio Preto, São Paulo State, were investigated. Data collection was monthly performed at three segments (headwaters, middle course, and mouth) from August 1999 to July 2000. The greatest values of water temperature, conductivity, turbidity, alkalinity, width, depth, and current velocity were obtained in the rainy season. Dissolved oxygen levels showed significant differences among three segments in all sampling months, except for September. Substrate composition was predominantly sandy, followed by silt and clay in middle course and mouth in rainy as much as in dry seasons. In headwaters a large increase of the sandy fraction occurred in the rainy season. In the marginal and aquatic vegetation 30 species of macrophytes and 5 of macroalgae were identified. The fauna included tadpoles of Anura and macroinvertebrates (Mollusca, Crustacea, Arachnida, and 8 orders of Insecta). A. fuscoguttatus was found throughout the entire stream in sympatry with 6 fish species. In middle course, cluster analysis revealed an association between A. fuscoguttatus immatures and low depth, suggesting a probable function of depth in that stage of ontogenetic development of catfishes. The results indicate that A. fuscoguttatus present plasticity in terms of microhabitat, including air breathing behavior in hypoxic conditions, previously unknown in genus Aspidoras.

Animals↗
PubMed2004

Relative sensitivity distribution of aquatic invertebrates to organic and metal compounds.

In the field, a multitude of species can be exposed to numerous toxicants; thus, the sensitivity of individual species to particular toxicants must be known to predict effects and to analyze changes in species composition. For most species, no information about their toxicant sensitivity is available. To address this limitation, we have grouped the available information to assign sensitivities to aquatic invertebrate taxa relative to Daphnia magna. With respect to organic compounds, most taxa of the orders Anisoptera, Basommatophora, Coleoptera, Decapoda, Diptera, Ephemeroptera, Eulamellibranchiata, Heteroptera, Hirudinea, Isopoda, Oligochaeta, Prosobranchia, Trichoptera, Tricladida, and Zygoptera are less sensitive than D. magna. Some taxa of the Amphipoda, Plecoptera, and Cladocera (other than D. magna) are significantly more sensitive. For organic compounds, approximately 22% of the investigated taxa were more sensitive than D. magna. Most taxa of the orders Amphipoda, Basommatophora, Diptera, Ephemeroptera, Eulamellibranchiata, Heteroptera, Isopoda, Oligochaeta, and Tricladida are significantly less sensitive than D. magna to metal compounds. The taxa belonging to the Crustacea, with the exception of the order Isopoda, are much more sensitive. For metal compounds, approximately 30% of the investigated taxa were more sensitive than D. magna. Hence, D. magna is among the most sensitive taxa regarding both groups of toxicants. The sensitivities for several taxa are listed, and use of the relative sensitivity distribution to link toxicant effects in mesocosm studies and field investigations is discussed.

Animals↗
PubMed2004

Effects of vertebrate hormones on development and sex determination in Daphnia magna.

Daphnia (Crustacea) are extensively used as model organisms in ecotoxicology; however, little is known regarding their endocrine system. This study examines Daphnia vulnerability to vertebrate hormones. Twelve natural or synthetic vertebrate hormones were screened for activity on developmental and reproductive processes in Daphnia magna. Natural hormones tested included: beta-estradiol, gonadotropin, hydrocortisone, insulin, melatonin, progesterone, somatostatin, testosterone, and thyroxine at concentrations ranging from 1 to 100 microg/L. Synthetic hormones tested included diethylstilbestrol (estrogenic), R-1881 (androgen), and ICI-182,780 (antiestrogen); all hormones were screened with a 6-d assay. Additionally, progesterone, insulin, testosterone, and thyroxine were screened for 25 d. Diethylstilbestrol decreased D. magna growth rate while thyroxine increased it. Short-term testosterone exposure reduced D. magna fecundity; however, long-term exposure did not, potentially indicating testosterone hydroxylation with long-term exposure. Hormones commonly considered sex-hormones (estrogens and androgens) in vertebrates do not appear to control sexual differentiation in D. magna; however, several vertebrate hormones do affect reproduction and development in D. magna making D. magna a potentially useful tool in monitoring for the presence of these hormones or compounds that mimic them.

Animals↗
PubMed2005

Effects of hydrogen sulfide to Vibrio fischeri, Scenedesmus vacuolatus, and Daphnia magna.

The effects of hydrogen sulfide (H2S) were tested in three ecotoxicological tests in order to evaluate its confounding potential in assessment of pore water and groundwater toxicity. The luminescent bacteria Vibrio fischeri, the water flea Daphnia magna, and the microalgae Scenedesmus vacuolatus often are part of a biotest battery. A new technique for the synthesis of hydrogen sulfide solutions of defined concentrations using an electrochemical generator instead of sodium sulfide solutions was used. Because hydrogen sulfide is volatile, the loss rate of H2S was studied over time to enable estimation of the mean test concentrations over the whole test duration. Loss rates were calculated to be 13 +/- 6% after 30 min, and 39 +/- 11% and 43 +/- 16% after a 24- and 48-h exposure time, respectively. Sensitivities of the test organisms in terms of median effective concentration (EC50), corrected for the above loss rates, varied from 0.28 to 0.0036 and 0.055 mM for the luminescent bacteria, the crustacea, and the algae, respectively. A species-sensitivity distribution using EC and mean lethal concentration literature data for marine and freshwater crustaceans and phytoplankton showed a medium sensitivity of the water flea D. magna, though the bacteria V. fischeri and the algae S. vacuolatus were among the least-sensitive group of organisms. This demonstrates that only the algae and the bacteria are easy to use in the assessment of toxicity of matrices with H2S concentrations above 0.06 mM.

Air Pollutants↗
PubMed2001

Shrimp--a dynamic model of heavy-metal uptake in aquatic macrofauna.

A dynamic model for prediction of bioaccumulation in aquatic macrofauna is described. The model, entitled SHRIMP (Simulation of Heavy-metal Rate of Intake for Macrofaunal sPecies), consists of five coupled submodels, which simulate individual growth, population dynamics, metal transport in the abiotic part of the system, metal bioaccumulation at the organism level, and upscaling of individual contamination to the population scale. The sublethal effects of metal toxicity on individual and population levels are shown to act through the reduction of individual growth rates. The model was tested for cadmium and mercury using epibenthic crustacea from an estuarine system. Individual and population patterns of bioaccumulation were analyzed by comparing the simulated results of five different scenarios of dissolved metal concentrations. Model results suggest that the subtle effect of growth reduction due to metal toxicity is sufficient to cause a decrease on population numbers simply by affecting the growth of the mature females and males.

Animals↗
PubMed2005

Potential impact of Dare County landfills on Alligator River National Wildlife Refuge.

Runoff of leachate from East Lake and Dare County Construction and Demolition Debris landfills has the potential to impact wildlife resources at Alligator River National Wildlife Refuge, Dare and Hyde Counties, North Carolina. Sediment quality of samples collected in August 2000 at 14 locations down-gradient from the landfills was assessed by measuring metal and organic contaminants in the sediments, chronic toxicity of solid-phase sediment (28-d static-renewal exposures; survival and growth as test endpoints) and acute toxicity of sediment porewater (96-h static exposures) to Hyalella azteca (Crustacea: Amphipoda). In addition, contaminant bioaccumulation from 4 sediments was determined using 28-d exposures of Lumbriculus variegatus (freshwater oligochaete). Although survival was not impaired, length of H. azteca was significantly reduced in sediments from 5 locations. Pore water from 4 locations was acutely toxic to H. azteca. Metals and a few polycyclic aromatic hydrocarbons (PAHs) were bioaccumulated by L. variegatus from the sediments. Several metals and PAHs exceeded sediment quality guidelines, and metals in porewater from several sites exceeded water quality criteria for the protection of aquatic wildlife. Runoff of leachate from the landfills has reduced sediment quality and has the potential to adversely affect wildlife resources at Alligator River National Wildlife Refuge.

Amphipoda↗
PubMed2002

Revision, phylogeny and biogeography of the groundwater amphipods Salentinellidae. I. Description of Salentinella anae nov. sp. from Spain with remarks on the genera Salentinella and Parasalentinella.

A new species of the groundwater amphipod Salentinella (Crustacea, Salentinellidae), S. anae, is described from Spain. This species is characterised by spines on the antennula peduncle, the absence of retinaculae on the pleopods, and the morphology of the coxal plate 1. Different morphological characters are evaluated before a phylogenetic study of the family. Salentinella prognatha is assigned as a synonym of S. petiti. The description of the genus Parasalentinella, as well as the diagnosis of the Salentinellidae are completed.

Amphipoda↗
PubMed2006

Stream buffer effectiveness in an agriculturally influenced area, southwestern Georgia: responses of water quality, macroinvertebrates, and amphibians.

To determine useful metrics for assessing stream water quality in the Southeastern Coastal Plain, we examined differences among two buffered and three unbuffered streams in an agricultural landscape in southwestern Georgia. Potential indicators included amphibian diversity and abundance, aquatic macroinvertebrate populations, riparian vegetative structure, water quality, and stream physical parameters. Variability among sites and treatments (buffered vs. unbuffered) existed, with sites in the same treatment as most similar, and disturbances from a nearby eroding gully strongly affecting one unbuffered site. Of the invertebrate metrics examined, percentages of clingers, Ephemeroptera-Plecoptera-Trichoptera (EPT), Elmidae (Coleoptera), Crustacea (Decapoda and Amphipoda), and dipterans were found to be possible indicators of stream health for perennial streams within this region. Overall, buffered sites showed higher percentages of sensitive invertebrate groups and showed lower and more stable concentrations of nitrate N, suspended solids, and fecal coliforms (FCs). Percent canopy cover was similar among sites; however, riparian vegetative coverage and percent leaf litter were greatest at buffered sites. No differences in amphibian abundance, presence, and absence within the riparian area were apparent between sites; however, instream larval salamanders were more abundant at buffered streams. In this study, stream buffers appeared to decrease nutrient and sediment loads to adjacent streams, enhancing overall water quality. Selected benthic macroinvertebrate metrics and amphibian abundance also appeared sensitive to agricultural influences. Amphibians show potential as indicator candidates, however further information is needed on their responses and tolerances to disturbances from the microhabitat to landscape levels.

Amphibians↗
PubMed1976

Thermal compensation in protein and RNA synthesis during the intermolt cycle of the American lobster, Homarus americanus.

1. The in vitro rates of incorporation of precursors into protein and RNA and the concentration of RNA were measured in tissues of intermolt and premolt lobsters acclimated to 5 degrees C and 20 degrees C. Midgut gland, abdominal muscle and gill of intermolt lobsters respond to temperature acclimation by a compensatory translation of the rate-temperature (R-T) curves with respect to the rates of incorporation of 3H-leucine and 3H-uridine into the acid-insoluble fraction. Midgut gland and muscle of premolt animals exhibit either no compensation or inverse compensation; gill tissue exhibits a rotation of the R-T curve. 2. The existence of the complete de novo pathway of pyrimidine biosynthesis is demonstrated in the class Crustacea. NaH14 CO2 is incorporated into orotic acid and orotic-14 C-acid is incorporated into the acid-insoluble fraction. 3. Both the concentration of RNA and the rates of incorporation of precursors of both the salvage and de novo pyrimidine pathways are enhanced in the midgut gland of premolt lobsters, relative to intermolt tissue, under conditions of warm-acclimation.

Acclimatization↗
PubMedDate not supplied

Insulin action: 1948-80.

Insulin is an old hormone from the standpoint of evolution. It is found in primitive vertebrates, insects, and crustacea and has effects on growth and glucose uptake in animals low on the evolutionary ladder, yes even unicellular organisms. The fascinating problem to consider is the relative emergence of the hormone and of its receptor. Csaba has reviewed recently the work with more primitive species. He argues convincingly that receptor molecules precede the hormones and adapt themselves to become the specific recognition sites they now are in the mammalian organism. This is a fascinating basis area for further research. The history of insulin research is rich and vivid, and has served to open up very important aspects of biochemistry and physiology. It was the first of the protein or peptide group of hormones; the protein whose amino acid sequence studies served to initiate this fruitful area of polymer biochemistry; and it began the important era of specific immunoassays, a technique that has revolutionized the study of the behavior and action of potent natural materials that are highly active in minute concentrations. Last but certainly not the least of its virtues is its medical use to maintain the life and health of countless victims of severe diabetes. The continuing study of the details of insulin action will undoubtedly have further profound influences on the basic and applied aspects of medicine and biology.

Animals↗
PubMedDate not supplied

Cross-reactions between respiratory and food allergens.

Cross-reactions between inhaled and food allergens are usually attributed to pollen hypersensitivity associated with fruit and vegetable allergy. However, other allergens are involved in these types of cross-reactions. In a few cases, there is a complete similarity between the inhaled and food allergens (garlic, crustacea proteins). More frequently, partial similarity has been demonstrated: whole inhaled allergens are included in ingested substances. Moreover, immunological techniques can demonstrate common antigenic epitopes in organic substances without any apparent relationship. This has been demonstrated by RAST-inhibition and/or immunoblot techniques, using sera from patients cross-sensitized to (1) pollens and fruits or vegetables or (2) avian sera and eggs. Respiratory sensitization always seems to precede food allergy symptoms.

Allergens↗