Effects of emergence phenology, taxa tolerances and taxonomic resolution on the use of the Chironomid Pupal Exuvial Technique in river biomonitoring

1. We studied chironomid communities of four rivers in south‐eastern Finland, differing in their water quality, during summer 2004 using the Chironomid Pupal Exuvial Technique, CPET. The aims of the study were to (i) test the adequacy of the generic‐level identification in the CPET method, (ii) define the emergence patterns of chironomid taxa classified as intolerant to organic pollution, (iii) assess the tolerance levels of intolerant chironomids and (iv) identify taxa most indicative of good water quality. 2. Procrustean rotation analysis indicated very strong concordance between the ordinations using either species or genus‐level data, suggesting that generic‐level identification of chironomids is adequate for biomonitoring based on CPET. However, when only a few taxa occur in great numbers, it may be advisable to identify these to the species level, especially if these taxa are important indicators of the impact in question. 3. The detection of a particular species may require accurate timing of sampling, whereas a species‐rich genus might be detected throughout a season. Given that the emergence of chironomid species may vary from year‐to‐year and between sampling sites, community differences detected at the species level may be related to between‐site variation in species’ emergence patterns rather than true differences in species composition. 4. Indicator species analysis (IndVal) showed that the distribution and abundance of intolerant chironomid taxa differed strongly among the studied rivers. Some of the intolerant taxa were restricted to unimpacted conditions, whereas others occurred mainly in impacted rivers. Thus, the indicator status of some genera (e.g. Eukiefferiella, Parametriocnemus, Stempellinella and Tvetenia) needs reassessment.     

营养膜无土栽培技术

前言营养膜技术(Nutrient Film Technique简称NFT)是国外广泛采用的一种特殊的无土栽培方法。它是将植物栽植在一个狭长的不透水的营养槽中,槽中有缓慢流动的营养液。植物根系的一部分浸没在营养液中,一部分露在空气中,植物从这种小环境中吸收水、营养物和氧气。由于这种方法采用很薄一层营养液在根际周围流动,裸露的根     

Réflexion sur l'utilisation des auxiliaires entomophages contreDiprion pini [Hym. Diprionidae]

Résumé Le problème de la lutte biologique en forêt, par utilisation d'entomophages indigènes, est discuté dans le cas d'un hyménoptère, le diprion du pin,Diprion pini L. Des études de dynamique des populations montrent que le schéma de progression spatiale des populations de cet insecte dans le sud du Bassin Parisien semble se renouveler à chaque pullulation. De plus les parasites représentent un véritable “facteur clé”. Leur incidence varie notamment de génération en génération: en faible nombre au début d'une gradation, ils ne peuvent alors en empêcher le développement; mais ensuite leur multiplication assure une régression brutale du ravageur. Dans ces conditions, des interventions assez peu onéreuses et faciles à réaliser, comme de simples transports de matériel parasité pourraient être efficaces; elles supposent toutefois le développement d'un foyer initial d'infestation. En revanche l'élevage d'espèces régulatrices commeAchrysocharella ruforum Krausse etPleolophus basizonus Grav. permettrait d'assurer la préservation permanente des massifs forestiers.

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Summary The spatial pattern of insect populations progression in southern “Bassin Parisien”, showed by population dynamics studies, seems to happen again for every outbreak. Parasites are moreover a true “key-factor”. Their effect is quite different from one generation to another one; scarce at the beginning of an outbreak, they cannot stop its evolution; but then, their increase allows a brutal collape of the pest. In such a case, cheap and easily achieved operations as simple carryings of parasited insects may be efficient, but they need the development of a first infestation focus. In return breeding of regulating species asAchrysocharella ruforum Krausse andPleolophus basizonus Grav. would be able to sure forest stands permanently.

     

Diversity in the immune system: “Preconceived ideas” or ideas preconceived?

Two concepts of the evolution and regulation of expression of the combining site repertoire of the immune system, are compared. One view is based on the Associative Recognition Theory as formulated by the author and the other is based on the Idiotype Network Idea as conceived by Jerne. The two concepts are analyzed from the point of view of their logic, internal consistency and factual support.     

Sequence analysis of a Dictyostelium discoideum gene coding for an active dihydroorotate dehydrogenase in yeast

A Dictyostelium discoideum DNA fragment isolated on the basis of its ability to complement the ural mutation of yeast, codes for a dihydroorotate dehydrogenase activity. The complete nucleotide sequence of this 1898 bp fragment has been determined and reveals an open reading frame capable of coding for a 369 amino acid polypeptide of molecular mass 47.000. The gene shows preferential use of codons with weak pairing forces. Eleven codons, mainly those with a G in the third position, are absent. The flanking sequences are unusually rich in A + T (80%). Several direct and inverted repeats exist in the 5' flanking sequence.     

CONSÉQUENCE DE LA VARIATION DES EFFECTIFS DES FEMELLES DE DINARMUS VAGABUNDUS,SUR LE PARASITISME DE L'UN DE LEURS HÔTES CALLOSOBRUCHUS MACULATUS

Lorsque 2 femelles ou 3 femelles de l'ectoparasite D. vagabundus parasitent conjointement un même lot d'hôtes l'intensité du grégarisme larvaire s'accroît par rapport à celui observé en présence d'une seule femelle pondeuse. Cela se traduit par une augmentation significative du nombre moyen de descendants des 2 sexes mais la production moyenne en fils est toujours très inférieure à celle des filles. Cependant, lorsque la densité de femelles pondeuses passe de 1 à 3, le rapport des sexes mâles/femelles des descendants évolue vers l'unité traduisant une augmentation plus rapide de l'effectif des fils que des filles.