The abundance of phytophilous invertebrates on different species of submerged macrophytes*

SUMMARY. 1. We tested Krecker's model (1939) which states that the abundance of invertebrates per unit macrophyte biomass varies with plant species and is higher on plants with finely dissected leaves than on plants with broad leaves. The abundance of invertebrates was measured in thirteen lacustrine macrophyte beds in southern Québec, Canada. The model was tested for the total abundance of invertebrates and for the abundances of Chironomidae, Cladocera, Cyclopoida, Gastropoda, Hydracarina, Ostracoda and Trichoptera. 2. More epiphytic invertebrates were found on the dissected Myriophyllum spp. than on the broad-leaved Potamogeton amplifolius Tuckerm, P. robbinsii Oakes and Vallisneria americana Michx. (P<0.01). More invertebrates were also found on P. amplifolius than on P. robbinsii or V. americana (P<0.01). The total abundance of invertebrates was not systematically related to the degree of plant dissection. 3. The abundances of Chironomidae, Cladocera, Cyclopoida, Gastropoda, Hydracarina, Ostracoda and Trichoptera varied on different plant species (P<0.01). Contrary to Krecker's hypothesis, however, macrophytes with finely dissected leaves (Ceratophyllum demersum and Myriophyllum spp.) did not in general support more invertebrates per unit plant biomass than plants with large leaves (Potamogeton amplifolius, P. robbinsii and Vallisneria americana).     

Adaptive response of blood lymphocytes as a marker of hemopoiesis status in exposed persons

An obvious correlation between the type of reaction manifested by peripheral blood lymphocytes to low dose irradiation in vitro (adaptive potential), the RBM cell composition (during the period of the major exposure), and the peripheral blood cell composition (at a late time period coincident with the studies of induced radioresistance) has been found in the Techa riverside residents in the later periods after the onset of a long-term low-dose rate radiation exposure (55-60 years later) within a range of individual red bone marrow doses from 0.01 to 1.79 Gy. The nature of these dependences observed in chronically exposed individuals differs from that revealed in the controls. It can be suggested based on the results of the study that the capacity for the adaptive response shown by peripheral blood lymphocytes donated by exposed persons in the remote period after exposure can be regarded as a biological marker of the functional state of the hemopoietic stem cell pool.     

Volatile chemical release by bethylid wasps: identity, phylogeny, anatomy and behaviour

The structures of volatile chemicals released by parasitic wasps in the family Bethylidae are shown to correspond to the subfamily to which the species belong. Species in the Epyrinae release skatole (3-methylindole) and species in the Bethylinae release a spiroacetal (2-methyl-1,7-dioxaspiro [5.5]undecane): these compounds are chemically very different. The enantiomeric composition of the spiroacetal differs between congeneric species. Chemical release is a discrete event under the active control of both male and female wasps. Structural differences between the mandibular glands and intramandibular glands suggest the mandibular glands to be the source of released volatiles. Real-time mass spectrometry shows that the spiroacetal is released by Goniozus nephantidis females during dyadic resource contests, with release more common during more aggressive interactions. Chemical tagging with deuterium further shows that the volatile is released by the loser of an agonistic interaction and not the winner. The function of spiroacetal and skatole release by bethylids is discussed.  © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 94 , 837–852.     

Physical forces constrain the depth distribution of the abundant native mussel Elliptio complanata in lakes

1. Unionid mussels often account for a large portion of benthic biomass and contribute to nutrient cycling and sediment processes, but are thought to be limited to shallow areas (<2–3 m). 2. The depth distribution and body size of Elliptio complanata were compared in seven Canadian Shield lake basins of different sizes to test what factors determine the upper and lower limit of their depth range. Specifically, I tested whether (i) the upper range of their distribution is limited by exposure to winds and wave action and (ii) the lower range of their distribution is limited by the depth of the thermocline or by the boundary of mud deposition. 3. The average depth distribution of E. complanata shifted to greater depths in larger lake basins. When comparing individual transects, maximum mussel density was found deeper at more exposed sites. Mussel size decreased with increasing depth and was larger, on average, in larger lake basins. These results suggest that physical forces limit the upper range of mussel distribution in lakes. 4. The maximum depth at which mussels were found in different lakes was closely related to thermocline depth. However, mussels were commonly observed below the predicted depth of the mud deposition boundary. The thermocline limits the lower range of mussel distribution in lakes, probably by limiting food availability and by determining water temperature. Substratum type does not limit the lower distribution of mussels. 5. These results suggest that unionid mussels are present in the deeper parts of the littoral zone, especially in large lakes. Therefore, comparisons of mussel populations between sites and between lakes would be biased unless the full depth distribution of these mussels is considered. These results also suggest that long‐term changes in the thermal structure of lakes could affect the range of unionid mussel populations and their functional role in littoral ecosystems.     

Features of DNA synthesis in chromatin from rat blood lymphocytes upon exposure to varying doses of ionizing radiation

Changes in the level of chromatin DNA synthesis after the total X-ray irradiation of rats in the dozes 0.5 Gr, 1 Gr and 7.76 Gr were shown. Interrelations between postradiation correlation of protein and DNA in lymphocytes of peripheral of blood rats were analyzed.     

The roles of redox processes in pea nodule development and senescence

Nodule senescence is triggered by developmental and environmental cues. It is orchestrated through complex but poorly characterized genetic controls that involve changes in the endogenous levels of reactive oxygen species (ROS) and antioxidants. To elucidate the importance of such redox control mechanisms in pea root nodule senescence, redox metabolites were analysed throughout nodule development in a commercial pea variety ( Pisum sativum cv. Phoenix) inoculated with a commercial rhizobial strain ( Rhizobium leguminosarum bv. viciae ). Although a strong positive correlation between nitrogenase activity and nodule ascorbate and glutathione contents was observed, the progressive loss of these metabolites during nodule senescence was not accompanied by an increase in nodule superoxide or hydrogen peroxide. These oxidants were only detected in nodule meristem and cortex tissues, and the abundance of superoxide or hydrogen peroxide strongly declined with age. No evidence could be found of programmed cell death in nodule senescence and the protein carbonyl groups were more or less constant throughout nodule development. Pea nodules appear to have little capacity to synthesize ascorbate de novo . l -galactono-1, 4-lactone dehydrogenase (GalLDH), which catalyses the last step of ascorbate synthesis could not be detected in nodules. Moreover, when infiltrated with the substrates l -galactono-1, 4-lactone or l -gulonolactone, ascorbate did not accumulate. These data suggest that ROS, ascorbate and glutathione, which fulfil well recognized, signalling functions in plants, decline in a regulated manner during nodule development. This does not necessarily cause oxidative stress but rather indicates a development-related shift in redox-linked metabolite cross-talk that underpins the development and aging processes.     

Host preferences of Palaearctic Culicoides biting midges: implications for transmission of orbiviruses

Feeding success depends on host availability, host defensive reactions and host preferences. Host choice is a critical determinant of the intensity at which pathogens are transmitted. The aim of the current study was to describe host preferences of Palaearctic Culicoides species (Diptera: Ceratopogonidae) Latreille using traps baited with the five different host species of poultry, horse, cattle, sheep and goat. Collections were carried out nightly in July and August 2009 in western France with three replicates of a 5 × 5 randomized Latin square (five sites, five hosts). Moreover, an ultraviolet (UV) light/suction trap was operated during host‐baited collections to correlate Culicoides biting rates and UV light/suction trap catches. A total of 660 Culicoides belonging to 12 species, but comprised mainly of Culicoides scoticus Downes and Kettle, Culicoides dewulfi Goetghebuer and Culicoides obsoletus Meigen, were collected on animal baits. Abundance was highest for the horse, which accounted for 95% of all Culicoides caught, representing 10 species. The horse, the largest bait, was the most attractive host, even when abundance data were corrected by weight, body surface or Kleiber's scaling factor. Culicoides obsoletus was the only dominant species attracted by birds. Both C. scoticus and C. dewulfi were collected mainly from the upper body of the horse. Finally, the quantification of host preferences allows for discussion of implications for the transmission of Culicoides‐borne pathogens such as bluetongue virus.     

Développement de la partie antérieure de la mandibule de Salmo trutta fario L. (Pisces, Teleostei, Salmonidae)

A study of the origin and development of the bony complex ("dentaire" s.l.) later forming the anterior part of the mandible of Salmo fario leads to the following conclusions: (1) various modes of ossifications occur in the ontogeny of this bony complex, (2) the main component is the dermal (dento-splénial) whereas the enchondral one (mentomeckelien) is much reduced, (3) the proposed term "dento-splénio-mentomeckelien" focuses attention, at the same time, on the order of appearance and relative importance of the two components.