Number of results to display per page
Search Results
472. Feeding strategies and competition between terrestrial Haemadipsa leeches (Euhirudinea: Arhynchobdellida) in Danum Valley rainforest (Borneo, Sabah)
- Creator:
- Gąsiorek, Piotr and Różycka, Hanna
- Format:
- print, počítač, and online zdroj
- Type:
- model:article and TEXT
- Subject:
- parazitismus, parasitism, ectoparasites, foraging behaviour, Haemadipsidae, haematophagy, 2, and 59
- Language:
- English
- Description:
- Haemadipsid leeches are among the most successful terrestrial invertebrates in Bornean rainforests. They are very common ectoparasites of vertebrates, and their abundance has facilitated the conduction of numerous projects in the fields of ecology, zoogeography and taxonomy. We undertook research on two species inhabiting lowland dipterocarp forest, Haemadipsa picta Moore, 1929 and Haemadipsa subagilis (Moore, 1929), in order to address the following questions: (a) is there a difference in leech abundance between trails and off-trails?; (b) is ambush location dependent on specimen size or is species-specific?; (c) is intra- and interspecific competition limited by differences in foraging behaviours or vertical niche partitioning? Our results clearly show that H. picta is more abundant on trails than on off-trails and is vertically dispersed within the understory; the size of a specimen is strongly correlated with plant height. Haemadipsa subagilis was found not to exhibit such patterns. We suggest a possible lowering of interspecific competition between these species as a result of: (i) size-dependent dispersion of H. picta (together with reduction of intraspecific competition); and (ii) habitat specialisation of H. subagilis. Moreover, we provide new observations on their foraging behaviour., Piotr Gąsiorek, Hanna Różycka., and Obsahuje bibliografii
- Rights:
- http://creativecommons.org/publicdomain/mark/1.0/ and policy:public
473. Females of the parasitoid wasp, Dendrocerus carpenteri (Hymenoptera: Megaspilidae), adjust offspring sex allocation when competing for hosts
- Creator:
- Mackauer, Manfred and Chow, Andrew
- Format:
- print, počítač, and online zdroj
- Type:
- article, články, journal articles, model:article, and TEXT
- Subject:
- Zoologie, konkurence, poměr pohlaví, competition, sex ratio, Megaspilidae, Dendrocerus carpenteri, hyperparasitoid, larval mortality, intensity of parasitism, offspring sex allocation, superparasitism, 2, and 59
- Language:
- English
- Description:
- Parasitoid females may adjust offspring sex allocation according to the number and quality of hosts available. Because in solitary species only one offspring survives per host, already parasitized hosts are of low quality and generally rejected. Superparasitism (i.e., sequential oviposition by the same or different females) results in aggressive interactions and competition for nutritional resources among larvae. We examined variations in the offspring sex ratio of Dendrocerus carpenteri (Curtis) (Hymenoptera: Megaspilidae), a solitary ectoparasitoid developing as a hyperparasitoid on the prepupae and pupae of primary aphid parasitoids inside mummified aphids. Mated females produced a female-biased sex ratio of 0.433 (proportion of sons) when caged singly and provided with 12 mummies for 2 h; they parasitized an average of four mummies/h and rarely superparasitized. Superparasitism increased when two females were caged together and provided with 12 mummies, from 1.18 to 1.24 and 1.38 eggs/host parasitized in 1, 2 and 3 h, respectively. The offspring sex ratio became increasingly more female-biased with increase in superparasitism; however, sex ratio variations were not correlated with cohort size. One mated and one unmated female provided with 12 mummies and caged together for 1 h produced a mean cohort sex ratio of 0.645, which differed from the one predicted (0.717) by an algebraic model incorporating the assumptions that both females contribute equal numbers of offspring and that the mated female does not change her offspring-sex allocation strategy. The observed shift in the cohort sex ratio to an increased female-bias indicates that mated females of D. carpenteri change their behaviour when encountering parasitized mummies or a conspecific competitor in the same patch. By depositing fertilized rather than unfertilized eggs, a female can increase the proportion of her daughters among parasitoids competing for a diminishing host supply., Manfred Mackauer, Andrew Chow., and Obsahuje bibliografii
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
474. Fenomén efemérních polních mokřadů na orné půdě
- Creator:
- Němec, Radomír, Vlasta Škorpíková, and Václav Křivan
- Format:
- Type:
- article, články, model:article, and TEXT
- Subject:
- Botanika, mokřady, orná půda, 2, and 58
- Language:
- Czech
- Description:
- Wetlands on arable land host ephemeral vegetation and their existence relies on soil water saturation and periodic mechanical disturbations. In this habitat, we found several rare species listed in the Black and Red List of Vascular Plants of the Czech Re - public. Evidently, wetlands on arable land deserve protection and further research is needed for their closer inspection. and Radomír Němec, Vlasta Škorpíková, Václav Křivan.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
475. Ferredoxin: the central hub connecting photosystem I to cellular metabolism
- Creator:
- Mondal, J. and Bruce, B. D.
- Format:
- print, bez média, and svazek
- Type:
- model:article and TEXT
- Subject:
- přenos elektronů, electron transfer, cellular metabolism, ferredoxin, global interaction, oxidation-reduction, 2, and 581
- Language:
- Multiple languages
- Description:
- Ferredoxin (Fd) is a small soluble iron-sulfur protein essential in almost all oxygenic photosynthetic organisms. It contains a single [2Fe-2S] cluster coordinated by four cysteine ligands. It accepts electrons from the stromal surface of PSI and facilitates transfer to a myriad of acceptors involved in diverse metabolic processes, including generation of NADPH via Fd-NADP-reductase, cyclic electron transport for ATP synthesis, nitrate reduction, nitrite reductase, sulfite reduction, hydrogenase and other reductive reactions. Fd serves as the central hub for these diverse cellular reactions and is integral to complex cellular metabolic networks. We describe advances on the central role of Fd and its evolutionary role from cyanobacteria to algae/plants. We compare structural diversity of Fd partners to understand this orchestrating role and shed light on how Fd dynamically partitions between competing partner proteins to enable the optimum transfer of PSI-derived electrons to support cell growth and metabolism., J. Mondal, B. D. Bruce., and Obsahuje bibliografické odkazy
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
476. Fertilization regimes under hot conditions alter photosynthetic response of bean plants
- Creator:
- Hassan, I. A., Abou Zeid, H. M., Taia, W., Haiba, N. S., Zahran, A., Badr, R. H., El Dakak, R. A., and Shalaby, E. A.
- Format:
- print, bez média, and svazek
- Type:
- model:article and TEXT
- Subject:
- fotosyntéza, fazol obecný, photosynthesis, Phaseolus vulgaris, heat stress, nitrogen fertilization, photosynthetic performance, Phaseolus vulgaris L, French bean, 2, and 581
- Language:
- Multiple languages
- Description:
- We examined the effects of foliar application of various nitrogen (urea) concentrations on gas-exchange and chlorophyll (Chl) fluorescence characteristics in bean plants treated by heat stress (42/30°C, day/night temperatures). Heat stress caused reductions in contents of Chl a, Chl b, and in maximum photochemical efficiency of PSII by 13, 20, and 27%, respectively, regardless of the N treatment. However, N fertilization caused significant increases in these parameters, especially at higher N concentrations. The net photosynthetic rate and stomatal conductance were enhanced by 32, 60, and 69% and by 25, 88, and 100% due to addition of 5, 10, and 15 mM N, respectively. However, gas-exchange parameters were reduced by 24% due to heat stress. N fertilization alleviated adverse effects of heat stress., I. A. Hassan, H. M. Abou Zeid, W. Taia, N. S. Haiba, A. Zahran, R. H. Badr, R. A. El Dakak, E. A. Shalaby., and Obsahuje bibliografii
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
477. Field and laboratory studies on drought tolerance and water balance in adult Pergalumna nervosa (Acari: Oribatida: Galumnidae)
- Creator:
- Slotsbo, Stine, Sørensen, Jesper G., Josef Starý, and Holmstrup, Martin
- Format:
- print, počítač, and online zdroj
- Type:
- article, články, journal articles, model:article, and TEXT
- Subject:
- Zoologie, pancířníci, ztráty vody, propustnost materiálů, přežití, Oribatida, water losses, permeability, survival, Galumnidae, oribatid mites, drought, soil water potential, osmolality, desiccation tolerance, 2, and 59
- Language:
- English
- Description:
- We studied the water balance, body fluid osmolality and survival of the oribatid mite, Pergalumna nervosa, when exposed to drought in field and laboratory experiments. In a replicated field experiment we artificially lowered the soil water content by putting roofs over selected plots, which reduced soil water potential to levels well below the permanent wilting percentage for plants (i.e. below -1.5 MPa). Even though a slight decrease in the abundance of P. nervosa (only found in the 0-5 cm soil layer) was recorded during the most severe drought stress (ca. -3.5 MPa), the majority of adult mites clearly survived these conditions for 3 weeks in the field without migrating to deeper soil layers. Exposing field collected adults in laboratory experiments simulating even more severe drought conditions revealed that P. nervosa can survive several weeks of gradually increasing drought stress (down to -7 MPa) with moderate water loss. The osmolality of body fluids increased as dehydration progressed, but apparently as a result of simple up-concentration of solutes and not the de novo synthesis of protective osmolytes. We compare and discuss these results in the light of what is known about other arthropods., Stine Slotsbo, Jesper G. Sørensen, Josef Stary, Martin Holmstrup., and Obsahuje bibliografii
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
478. Fine fluorescent powder marking study of dispersal in the spruce bark beetle, Ips typographus (Coleoptera: Scolytidae)
- Creator:
- Petr Doležal, Okrouhlík, Jan, and Davídková, Markéta
- Format:
- print, počítač, and online zdroj
- Type:
- article, články, journal articles, model:article, and TEXT
- Subject:
- Zoologie, kůrovcovití, lýkožrout smrkový, Scolytidae, Ips typographus, Coleoptera, bark beetle, dispersal, fluorescent powder, chráněná území, 2, and 59
- Language:
- English
- Description:
- A novel method was used to study dispersal in the spruce bark beetle, Ips typographus (L.), under epidemic conditions (rapidly increasing population density) in the Šumava National Park. Infested spruce logs were coated with a fine fluorescent powder and the passively marked emerging beetles were captured in pheromone baited traps located at various distances from these logs. The number of marked beetles captured decreased exponentially with increasing distance from the release point. The sex ratio of the bark beetles was more female biased the further they were recaptured from the logs, being 57% and 60% at distances of up to 50 and 100 m, respectively. The maximum distance flown by a marked beetle recorded in this experiment was 1094 m. A model fitted to the data on dispersal indicates that 10% of the spruce bark beetles dispersed over distances of 55 m and 4 m in spring (overwintered parental generation) and summer (first filial generation), respectively. Differences between spring and summer swarming are briefly discussed., Petr Doležal, Jan Okrouhlík, Markéta Davídková., and Obsahuje bibliografii
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
479. Fine structure of the external sheaths of the ovipositor of Aphidius ervi (Hymenoptera: Braconidae)
- Creator:
- Ruschioni, Sara, Riolo, Paola, Romani, Roberto, Battaglia, Donatella, and Isidoro, Nunzio
- Format:
- print, počítač, and online zdroj
- Type:
- model:article and TEXT
- Subject:
- blanokřídlí, lumčíkovití, Hymenoptera, Braconidae, Aphidius ervi, ultrastructure, ovipositor valve, parasitoid, gland, marking pheromone, 2, and 59
- Language:
- English
- Description:
- The function and structure of the ovipositor in Hymenoptera have been studied intensively, although there is a lack of information on the external sheaths. We provide here a contribution on the structure of the external sheaths of the ovipositor of the parasitic wasp Aphidius ervi, in particular the secretory structure is described for the first time. These glands are made up of a large epithelial structure that consists a single layer of large secretory cells that occupy most of the lumen of the valve and belong to gland cell class 1. Based on the different features of the glands, a lubricating and/or host marking function is hypothesized and discussed., Sara Ruschioni, Paola Riolo, Roberto Romani, Donatella Battaglia, Nunzio Isidoro., and Obsahuje bibliografii
- Rights:
- http://creativecommons.org/publicdomain/mark/1.0/ and policy:public
480. First evidence of serotoninergic components in the nervous system of the monogenean Chimaericola leptogaster (Chimaericolidae, Polyopisthocotylea), a gill parasite of the relict holocephalan fish
- Creator:
- Mochalova, Natalya V, Terenina, Nadezhda B, Poddubnaya, Larisa G, Yashin, Valery A, Kuchin, Andrei V, and Kreshchenko, Natalya D
- Format:
- print, počítač, and online zdroj
- Type:
- model:article and TEXT
- Subject:
- ploštěnci, Platyhelminthes, serotonin, reproductive system, muscle system, haptor, 2, and 59
- Language:
- English
- Description:
- The localisation and distribution of the serotoninergic nerve elements was studied for the first time in the flatworm Chimaericola leptogaster (Leuckart, 1830) using immunocytochemical methodology and confocal laser scanning microscopy. The musculature was investigated by histochemical staining of actin filaments; scanning electron microscopy was used to identify the sensory structures on the worm's surface. Uniciliated, bi-ciliated and multiciliated sensory endings have been described on the worm's surface. The morphological data demonstrate the presence of circular, longitudinal and diagonal muscles that comprise the musculature of C. leptogaster in the anterior, median and posterior body regions. Well-developed radial and circular muscle fibres were also observed surrounding the genital pore, two vaginae and in clumps of the haptor. The study revealed the presence of biogenic amine, serotonin, in the central and peripheral nervous systems of C. leptogaster: in the neurons and fibres of the cephalic ganglia and ventral nerve cord, in the innervation of reproductive system compartments. The localised sites of the serotoninergic elements point to important roles of serotonin in monogenean reproductive processes and, possibly, in the regulation of muscle function., Natalya V. Mochalova, Nadezhda B. Terenina, Larisa G. Poddubnaya, Valery A. Yashin, Andrei V. Kuchin, Natalya D. Kreshchenko., and Obsahuje bibliografii
- Rights:
- http://creativecommons.org/publicdomain/mark/1.0/ and policy:public