Biogenic amines modulate pulse rate in the dorsal blood vessel of Lumbriculus variegatus

The biogenic amines are widespread regulators of physiological processes, and play an important role in regulating heart rate in diverse organisms. Here, we present the first pharmacological evidence for a role of the biogenic amines in the regulation of dorsal blood vessel pulse rate in an aquatic oligochaete, Lumbriculus variegatus (Müller, 1774). Bath application of octopamine to intact worms resulted in an acceleration of pulse rate, but not when co-applied with the adenylyl cyclase inhibitor MDL-12,330a. The phosphodiesterase inhibitor theophylline mimicked the effects of OA, but the polar adenosine receptor antagonist 8(p-sulphophenyl)theophylline was significantly less potent than theophylline. Pharmacologically blocking synaptic reuptake of the biogenic amines using the selective 5-HT reuptake blocker fluoxetine or various tricyclic antidepressants also accelerated heart rate. Depletion of the biogenic amines by treatment with the monoamine vesicular transporter blocker reserpine dramatically depressed pulse rate. Pulse rate was partially restored in amine-depleted worms after treatment with octopamine or dopamine, but fully restored following treatment with serotonin. This effect of 5-HT was weakly mimicked by 5-methoxytryptamine, but not by α-methylserotonin; it was completely blocked by clozapine and partially blocked by cyproheptadine. Because they are known to orchestrate a variety of adaptive behaviors in invertebrates, the biogenic amines may coordinate blood flow with behavioral state in L. variegatus.     

Occurrence of the Sunda colugo (Galeopterus variegatus) in the tropical forests of Singapore: A Bayesian approach

Dermopterans are taxonomically-unique mammals, but little is known about their habitat requirements. The Sunda colugo (Galeopterus variegatus), which is one of only two living species of dermopterans confined to Southeast Asia, reportedly occurs in tropical forests, plantations, and gardens. Based on their ecology, however, we predict that tropical forests are likely to be their primary habitats. Here, we investigate environmental variables that account for the occurrence of G. variegatus in Singapore using Bayesian inference. Our results show that G. variegatus was only detected in transects with over 95% canopy cover, which was ultimately the most important predictor of colugo occurrence. Tropical forests, including disturbed forests, with relatively intact canopies are therefore vital for colugos to persist.     

Influence of piperonyl butoxide on the toxicity of organophosphate insecticides to three species of freshwater benthic invertebrates

Toxicity tests were conducted with amphipods (Hyalella azteca), chironomids (Chironomus tentans) and oligochaetes (Lumbriculus variegatus) exposed to a series of organophosphate insecticides in the absence or presence of piperonyl butoxide (PBO), an inhibitor of cytochrome(s) P450. Piperonyl butoxide effectively reduced the toxicity to H. azteca and C. tentans of three organophosphates (diazinon, chlorpyrifos, azinphos-methyl) which undergo metabolic activation by cytochrome(s) P450. Coadministration of PBO with another organophosphate (dichlorvos) which is not activated by cytochrome(s) P450, did not reduce the toxicity to the two species. Lumbriculus variegatus was relatively insensitive to the organophosphates, and PBO did not reduce their toxicity to the oligochaete. These data indicate that both H. azteca and C. tentans possess cytochrome P450-mediated MOs capable of metabolizing organic xenobiotics. However, the degree to which L. variegatus might be capable of the oxidative metabolism of organic xenobiotics is uncertain.     

Why be cryptic? Choice of host urchin is not based on camouflage in the caridean shrimp Gnathophylloides mineri

The caridean shrimp Gnathophylloides mineri lives among the spines of various species of sea urchins. The shrimp has cryptic coloration that closely matches the coloration of the Caribbean urchin Tripneustes ventricosus. Despite this camouflage, in Jamaica, G. mineri is three times more abundant on the urchin Lytechinus variegatus than on T. ventricosus. L. variegatus exhibits more pronounced covering behavior than T. ventricosus. In laboratory choice experiments, the shrimp exhibited no preference between live, uncovered T. ventricosus or L. variegatus. Similarly, there was no preference between models (the tests, with spines attached, of hollowed out urchins) of T. ventricosus or L. variegatus without cover, or between models of T. ventricosus or L. variegatus with switched cover (i.e., each model was covered with the debris that had belonged to its partner when collected). There was, however, a significant preference for L. variegatus models with their natural covering over T. ventricosus with their natural covering. The shrimp may prefer L. variegatus with its extensive covering over T. ventricosus with extensive covering because the spines of the former are typically erect, as opposed to the spines of T. ventricosus, which usually lay flat across the test and would not give the shrimp much room to maneuver under the debris layer. Our study indicates that despite effective morphological and behavioral traits that render an organism highly cryptic, other, more effective, means of concealment may undermine the usefulness of this crypsis.     

Chemical characterization of the component of the jelly coat from sea urchin eggs responsible for induction of the acrosome reaction.

Jelly coat, a multicomponent extracellular matrix surrounding the sea urchin egg, induces the acrosome reaction in sperm. The jelly coats of the four species studied, Arbacia punctulata, Strongylocentrotus purpuratus, Strongylocentrotus drobachiensis, and Lytechinus variegatus, were found to be very similar in chemical composition. A sialoprotein (approximately 20% of the mass of the jelly coat) and a fucose sulfate polysaccharide (approximately 80%) are the major macromolecular components of the jelly coat. The acrosome reaction inducing capacity resides solely in the fucose sulfate polysaccharide. Induction of the acrosome reaction ranges from highly species specific to nonspecific. Thus, A. punctulata and S. drobachiensis sperm are induced to undergo the acrosome reaction only with their homologous jelly coat, while S. purpuratus sperm react equally well with homologous or L. variegatus jelly coat, but not with A. punctulata jelly coat. L. variegatus sperm seem to be relatively nonspecific in response. Species-specific induction of the acrosome reaction resides solely in the fucose sulfate polysaccharide, suggesting that there must be structural differences in this polysaccharide in the various species. Therefore, in some species, fertilization appears to involve sperm-egg recognition at the level of the jelly coat as well as at the level of sperm-egg receptors.     

Toluene Monooxygenase-Catalyzed Epoxidation of Alkenes

Several toluene monooxygenase-producing organisms were tested for their ability to oxidize linear alkenes and chloroalkenes three to eight carbons long. Each of the wild-type organisms degraded all of the alkenes that were tested. Epoxides were produced during the oxidation of butene, butadiene, and pentene but not hexene or octadiene. A strain of Escherichia coli expressing the cloned toluene-4-monooxygenase (T4MO) of Pseudomonas mendocina KR1 was able to oxidize butene, butadiene, pentene, and hexene but not octadiene, producing epoxides from all of the substrates that were oxidized. A T4MO-deficient variant of P. mendocina KR1 oxidized alkenes that were five to eight carbons long, but no epoxides were detected, suggesting the presence of multiple alkene-degrading enzymes in this organism. The alkene oxidation rates varied widely (ranging from 0.01 to 0.33 μmol of substrate/min/mg of cell protein) and were specific for each organism-substrate pair. The enantiomeric purity of the epoxide products also varied widely, ranging from 54 to >90% of a single epoxide enantiomer. In the absence of more preferred substrates, such as toluene or alkenes, the epoxides underwent further toluene monooxygenase-catalyzed transformations, forming products that were not identified.     

Territory re‐establishment in Cyprinodon variegatus lacepede

Cyprinodon variegatus males were allowed to establish territories in small aquaria. The ability of a male to maintain a territory was examined under conditions that varied group composition and sequentially varied space availability. Three cohorts of males were identified: non‐territorial individuals, rarely territorial individuals, and frequently territorial individuals. The results indicate that group social structure is not affected by changes in available space. Although no single male was always territorial in trials that varied group composition, a small number of males were frequently territorial. Often these successful males were temporarily displaced, but they typically regained a territory in subsequent trials.     

Sociogenetic organisation of two desert ants

Desert ants of the genus Cataglyphis evolved a remarkable diversity in their reproductive strategies. In Cataglyphis species where social organisation was described so far, colonies are headed by one or multiple queens, queens being singly or multiply mated, and workers and/or queens possess the ability to reproduce asexually via thelytokous parthenogenesis. Here, we investigate the social organisation of C. bombycina (group bombycinus) and C. theryi (group albicans) using highly polymorphic microsatellite markers. Our results show that both species are characterized by monogynous colonies and multiply mated queens, supporting the idea that polyandry is an ancestral trait of the genus. No evidence for parthenogenetic reproduction by queens was found. One distinctive feature of the species C. bombycina among the genus is the presence of a morphologically distinct soldier caste, with highly developed scythe blades jaws. In the only colony where a significant number of soldiers have been sampled, the distribution of patrilines is fundamentally different between the soldier and the worker caste. This result suggests a genetic contribution to worker caste determination in this species, and certainly awaits further investigation.     

Versatility in Corrinoid Salvaging and Remodeling Pathways Supports Corrinoid-Dependent Metabolism in Dehalococcoides mccartyi

Corrinoids are cobalt-containing molecules that function as enzyme cofactors in a wide variety of organisms but are produced solely by a subset of prokaryotes. Specific corrinoids are identified by the structure of their axial ligands. The lower axial ligand of a corrinoid can be a benzimidazole, purine, or phenolic compound. Though it is known that many organisms obtain corrinoids from the environment, the variety of corrinoids that can serve as cofactors for any one organism is largely unstudied. Here, we examine the range of corrinoids that function as cofactors for corrinoid-dependent metabolism in Dehalococcoides mccartyi strain 195. Dehalococcoides bacteria play an important role in the bioremediation of chlorinated solvents in the environment because of their unique ability to convert the common groundwater contaminants perchloroethene and trichloroethene to the innocuous end product ethene. All isolated D. mccartyi strains require exogenous corrinoids such as vitamin B₁₂ for growth. However, like many other corrinoid-dependent bacteria, none of the well-characterized D. mccartyi strains has been shown to be capable of synthesizing corrinoids de novo. In this study, we investigate the ability of D. mccartyi strain 195 to use specific corrinoids, as well as its ability to modify imported corrinoids to a functional form. We show that strain 195 can use only specific corrinoids containing benzimidazole lower ligands but is capable of remodeling other corrinoids by lower ligand replacement when provided a functional benzimidazole base. This study of corrinoid utilization and modification by D. mccartyi provides insight into the array of strategies that microorganisms employ in acquiring essential nutrients from the environment.     

Abundance and life cycle of Zonocerus variegatus (Orthoptera: Pyrgomorphidae) in the humid forest zone of southern Cameroon

Weekly captures from January 2000 to January 2002 enabled us to study the abundance and life cycle of the variegated grasshopper, Zonocerus variegatus (Orthoptera: Pyrgomorphidae), in the humid forest zone of Southern Cameroon. We found that Z. variegatus was present throughout the year in the forest reserve and the human‐influenced zones of Yaounde and Mbalmayo in two univoltine populations, which had unequal abundance and durations. The separation of the two populations was clearer in the Yaounde and Mbalmayo developed zones than in the Mbalmayo forest reserve (undeveloped zone). The abundance of Z. variegatus varied according to the post‐embryonic stage, sex, year and season. Hatching and coupling took place during the dry and rainy seasons, whereas oviposition occurred only in the rainy season. In Cameroon, the type of life cycle of Z. variegatus observed in the humid forest zone of the south is different from that of the “Sudanian and Sahelian” zones.     

小球藻亲环蛋白A(CyPA)基因克隆及表达特性分析

亲环蛋白广泛存在于生物体中,并发挥着重要的作用。本研究从小球藻cDNA文库中筛选获得亲环蛋白A(CyPA Gene);通过提取转化35S::CyPA::GFP融合质粒拟南芥的原生质体研究表明,CyPA定位于叶绿体中;过表达CyPA基因的酵母能够增强InV酵母对NaCl、NaHCO3胁迫的生长能力;通过实时定量PCR研究表明,在非生物胁迫的条件下,CyPA基因的表达量升高,推测CyPA基因与非生物胁迫抗性相关,亲环蛋白A参与生物体的抗逆生存能力。     

Characterizing the host specificity of Ischnodemus variegatus (Signoret) (Hemiptera: Blissidae) on two congeneric grass species

Life history parameters of the sap-feeding bug Ischnodemus variegatus (Signoret) (Hemiptera: Blissidae) were compared between the invasive Neotropical grass, Hymenachne amplexicaulis (Rudge) Nees and the Australian native Hymenachne acutigluma (Steudel) Guilliland. Development of immatures, adult longevity, ovipositional preference and population growth of I. variegatus were compared on H. amplexicaulis and H. acutigluma under choice and no-choice conditions. Third-instar nymphs developed on both hosts but individuals reared on H. acutigluma had a 40% lower survival rate to the adult stage, 40% longer developmental time, a 9% reduction in length and a 30% reduction in weight of females compared to those reared on H. amplexicaulis. The no-choice adult longevity and oviposition study indicated that individuals feeding on H. acutigluma had half the lifespan, 62% as many ovipositing females, 52% longer time to first oviposition and only 14% as many eggs per female. Under choice conditions, females laid only 37% as many eggs on H. acutigluma as on H. amplexicaulis. Population growth of I. variegatus was slower on H. acutigluma compared to H. amplexicaulis over a 60 day period resulting in negative population increase on H. acutigluma but positive increase on H. amplexicaulis. These results reflect an overall poorer performance of I. variegatus on H. acutigluma for most life stages.     

Enhanced Growth of Wheat and Soybean Plants Inoculated with Azospirillum brasilense Is Not Necessarily Due to General Enhancement of Mineral Uptake

The capacity of Azospirillum brasilense to enhance the accumulation of K⁺, P, Ca²⁺, Mg²⁺, S, Na⁺, Mn²⁺, Fe²⁺, B, Cu²⁺, and Zn²⁺ in inoculated wheat and soybean plants was evaluated by using two different analytical methods with five A. brasilense strains originating from four distinct geographical regions. A Pseudomonas isolate from the rhizosphere of Zea mays seedlings was included as a control. All A. brasilense strains significantly improved wheat and soybean growth by increasing root and shoot dry weight and root surface area. The degree of plant response to inoculation varied among the different strains of A. brasilense. All strains were capable of colonizing roots, but the best root colonizer, Pseudomonas sp., had no effect on plant growth. The numbers of organisms of Brazilian strains Sp-245 and Sp-246 colonizing roots were similar regardless of the host plant. Numbers of organisms for the other strains were directly dependent on the host plant. The main feature characterizing mineral accumulation in inoculated plants was that all inoculation treatments changed the mineral balance of the plants, but in an inconsistent manner. Enhancement of mineral uptake by plants also varied among strains to a great extent and was directly dependent on the strain-plant combination; i.e., a strain capable of increasing accumulation of a particular ion in one plant species or cultivar often lacked the ability to do so in another. Minerals in inoculated plants were not evenly distributed in different plant tissues, and the changes varied among groups of plants within each bacterial strain inoculation treatment. We suggest that, although A. brasilense strains are capable of changing the mineral balance and content of plants, it is unlikely that this ability is a general mechanism responsible for plant improvement by A. brasilense.     

The effect of the quality of food patches on larval vertical distribution of the sea urchins Lytechinus variegatus (Lamarck) and Strongylocentrotus droebachiensis (Mueller)

Although most invertebrate larvae are weak swimmers and act as passive particles on horizontal scales, they may be able to regulate their vertical position in response to different factors, including increased food concentration. We examined the effect of the quality of food patches on larval vertical distribution for the sea urchins Lytechinus variegatus and Strongylocentrotus droebachiensis, and determined the effect of dietary conditioning on that response in the laboratory. We reared larvae on a mixed algal diet of Dunaliella tertiolecta and Isochrysis galbana under low (500 cells ml⁻¹) and high (5000 cells ml⁻¹) rations. Food patches were maintained in Plexiglas rectangular columns (30×10×10 cm) using a density gradient, where practical salinity in the bottom layer was 33, in the middle layer 30, and in the top layer 27. We examined the magnitude and mechanism of a behavioural response of larvae of L. variegatus in the four-arm stage, and on two developmental stages of S. droebachiensis (four- and six-arm), by manipulating patch quality. In the absence of a patch, larvae of both species and developmental stages swam through to the surface of the experimental columns. In the presence of algae, fewer larvae were present above the patch and more were at the patch than in control columns. More larvae swam through patches of “unflavoured” algal mimics than algal patches, and aggregated at the surface. Larval distribution relative to patches of algal filtrate without algal cells or of “flavoured” algal mimics in algal filtrate was not consistently different from that in either control or algal patches; thus, the magnitude of larval response to filtrate (with or without particles) was intermediate between that to control and algal patches. For L. variegatus, more larvae crossed the patches when reared on low than high rations, indicating that poorly conditioned larvae may be less responsive to environmental cues. Our results suggest that larvae can actively aggregate and maintain a vertical position in response to a food patch that depends on the quality and quantity of food. The response appears to be based mostly on a chemosensory rather than a mechanosensory mechanism.     

Comparative DNA Damage and Repair in Echinoderm Coelomocytes Exposed to Genotoxicants

The capacity to withstand and repair DNA damage differs among species and plays a role in determining an organism''s resistance to genotoxicity, life history, and susceptibility to disease. Environmental stressors that affect organisms at the genetic level are of particular concern in ecotoxicology due to the potential for chronic effects and trans-generational impacts on populations. Echinoderms are valuable organisms to study the relationship between DNA repair and resistance to genotoxic stress due to their history and use as ecotoxicological models, little evidence of senescence, and few reported cases of neoplasia. Coelomocytes (immune cells) have been proposed to serve as sensitive bioindicators of environmental stress and are often used to assess genotoxicity; however, little is known about how coelomocytes from different echinoderm species respond to genotoxic stress. In this study, DNA damage was assessed (by Fast Micromethod) in coelomocytes of four echinoderm species (sea urchins Lytechinus variegatus, Echinometra lucunter lucunter, and Tripneustes ventricosus, and a sea cucumber Isostichopus badionotus) after acute exposure to H₂O₂ (0–100 mM) and UV-C (0–9999 J/m²), and DNA repair was analyzed over a 24-hour period of recovery. Results show that coelomocytes from all four echinoderm species have the capacity to repair both UV-C and H₂O₂-induced DNA damage; however, there were differences in repair capacity between species. At 24 hours following exposure to the highest concentration of H₂O₂ (100 mM) and highest dose of UV-C (9999 J/m²) cell viability remained high (>94.6±1.2%) but DNA repair ranged from 18.2±9.2% to 70.8±16.0% for H₂O₂ and 8.4±3.2% to 79.8±9.0% for UV-C exposure. Species-specific differences in genotoxic susceptibility and capacity for DNA repair are important to consider when evaluating ecogenotoxicological model organisms and assessing overall impacts of genotoxicants in the environment.     

Effect of organic and inorganic nitrogen sources on endogenous polyamines and growth of ectomycorrhizal fungi in pure culture

 The abilities of three ectomycorrhizal fungi, Paxillus involutus, Suillus variegatus and Lactarius rufus, to utilize organic and inorganic nitrogen sources were determined by measuring the growth and endogenous free polyamines (putrescine, spermidine and spermine) of pure culture mycelium. Differences were found in the utilization of the nitrogen sources and in the polyamine concentrations between the fungal species and between isolates of L. rufus. All the fungi grew well on ammonium and on several amino acids. Endogenous polyamine levels varied with the nitrogen source. Spermidine was commonly the most abundant polyamine; however, more putrescine than spermidine was found in P. involutus growing on inorganic nitrogen or arginine. Low amounts of spermine were found in S. variegatus and some samples of L. rufus. None or only a trace of spermine was found in P. involutus mycelium. In all fungi, putrescine concentrations were higher with ammonium than with the nitrate treatment. The total nitrogen content of peat did not determine the ability of L. rufus strains isolated from peatland forest sites to utilize organic nitrogen. Accepted: 27 November 1998     

Cryptococcus gattii, No Longer an Accidental Pathogen?

Cryptococcus gattii is an environmentally occurring pathogen that is responsible for causing cryptococcosis marked by pneumonia and meningoencephalitis in humans and animals. C. gattii can form long-term associations with trees and soil resulting in the production of infectious propagules (spores and desiccated yeast). The ever-expanding number of reports of clinical and environmental isolation of C. gattii in temperate climates strongly imply that C. gattii occurs worldwide. The key ability of yeast and spores to enter, survive, multiply, and exit host cells, and to infect immunocompetent hosts distinguishes C. gattii as a primary pathogen and suggests evolution of C. gattii pathogenesis as a result of interaction with plants and other organisms in its environmental niche. Here we summarize the historical literature on C. gattii and recent literature supporting the worldwide occurrence of the primary pathogen C. gattii.