Ultrastructure de la spermiogenèse et du spermatozoïde de Loimosina wikoni et affinités phylétiques des Loimoidae (Plathelminthes, Monogenea, Monopisthocotylea)

In Loimosina, during spermiogenesis, the zone of differentiation of the spermatid contains two centrioles continued as two 9 +‘1’axonemes. One of the axonemes lengthens and will become the principal axoneme of the spermatozoon. The other axoneme is as long as the first one at the beginning of spermiogenesis, but is shorter in the mature sperm cell. The spermatozoon consists of several regions: (a) at the anterior end, the centriolar derivative of the principal axoneme; (b) a short region which shows cortical microtubules coinciding with external ornamentations; (c) a long uniflagellate region, with mitochondrion; (d) a biflagellate region containing the anterior slender part of the nucleus; (e) the posterior part of the nucleus, with no accompanying cytoplasmic organelles. Spermiogenesis and sperm structure in Loimosina differ from what is known in all other described monogeneans, excepting the monocotylid Heterocofyle to which they show close resemblances. However, the alteration of the second axoneme is more complete in Heterocofyle than in Loimosina. Comparative study of spermiogenesis and sperm ultrastructure thus shows an interesting coincidence with classical phylogenies of the monogeneans, in which the families Loimoidae and Monocotylidae are closely related. Chez Loimosina, pendant la spermiogenèse, la zone de différenciation de la spermatide contient deux centrioles prolongés par deux axonemes de type 9 +‘1′. L'un des axonemes s'allonge et deviendra l'axonème principal du spermatozoïde mûr. Le deuxième axontme est aussi long que le premier au début de la spermiogenèse, mais il est plus court dans le spermatozoïde mûr. Le spermatozoïde comprend: (a) à l'avant, le dérivé centriolaire de l'axonème principal; (b) une courte région contenant quelques microtubules corticaw longitudinaux coincidant avec des omementations extramembranaires; (c) une longue région miflagellée avec mitochondrie; (d) une région biflagellée contenant La partie antérieure effilée du noyau; (e) la région postérieure du noyau, sans organites cytoplasmiques accompagnateurs. La spermiogenèse et la structure du spermatozoïde de Loimosina sont différentes de ce qui est connu chez tous les autres Monogènes décrits, excepté le Monocotylidae Heterocofyle auquel elles ressemblent beaucoup. Toutefois, l'altération du deuxième axonème est moins complète chez Loimosina que chez Heterocotyle. L'étude comparée des spermatozoïdes et des spermiogenèses montre une bonne coincidence avec les phylogenèses classiques, dans lesquelles les familles Loimoidae et Monocotylidae sont proches.     

Resource density regulates the foraging investment in higher termite species

1. Resource density can regulate the area that animals use. At low resource density, there is a conflict in terms of balance between costs of foraging and benefits acquired. The foraging of the higher termite Nasutitermes aff. coxipoensis consists of searching throughout trails and a building galleries phase. 2. In this study, a manipulative field experiment was used to test the hypothesis that colonies of N. aff. coxipoensis forage towards a more profitable balance between the establishment of trails and gallery construction at low resource density. 3. The experiment was conducted in north‐eastern Brazil. Seven experimental plots were established with a continuous increase in resource density (sugarcane baits). Entire colonies of N. aff. coxipoensis were transplanted from their original sites to the experimental plot, totalling 35 nests. The number, branches and total length of trails and galleries were quantified. 4. The results show that N. aff. coxipoensis optimises its foraging output, intensifying the establishment of trails at the cost of gallery construction when resource density is low. The number of trails, the number of trail branches and the total length of trails decreased with increasing resource density. Interestingly, at low resource density, the search effort was concentrated on forming longer and a greater number of trails, a small proportion of which were converted into galleries. The opposite relationship was observed at high resource density. 5. These results suggest an optimisation of search efforts during foraging depending on resource density, a mechanism that may help researchers to understand the use of space by higher termite species.     

Callus tissue of Solanum tuberosum L. cultured in the presence of the pyrethroid deltamethrin

The effect of Decis (deltamethrin as active ingredient) on callus tissue of Solanum tuberosum L. cv. Désirée was studied. Decis is an agrochemical currently used on field grown potato plants to control the Colorado beetle, a potato pest. Deltamethrin added to the culture medium interferes with the behaviour of callus tissue. After 5 h of culture, the level of total proteins was higher in treated tissue than in the control, and SDS-PAGE showed that deltamethrin promoted the increase of some soluble proteins. After 24 h and 14 days of culture, the level of total proteins became similar in both treated and control material. This similarity between control and treated tissues, after 14 days of culture, occurred as a result of the treatment with deltamethrin which caused a decrease of soluble proteins, but an increase in insoluble proteins whereas the opposite was observed for control callus. SDS-PAGE of both soluble and insoluble proteins showed that only quantitative dissimilarities occurred. This longer treatment also increased the chlorophyll content. Ultrastructural study of the cells revealed that tissue callus cultured for 14 days in the presence of deltamethrin had plastids containing a more developed membranous system, with a higher number of grana and with more compartments than in control cells. Deltamethrin also promoted the abundance of vesicles associated with dictyosomes. This response of the callus tissue to Decis added to the callus medium parallels the behaviour of potato plants treated with this agrochemical under field conditions (Fidalgo, Santos & Salema, 1993).     

Spatial distribution of genetic relatedness in a moorland population of red grouse (Lagopus lagopus scoticus)

Several aspects of the ecology and biology of red grouse (Lagopus lagopus scoticus) could prevent the complete admixture of genes within and between populations. Male red grouse display a high degree of natal philopatry, are territorial, and show less aggression to kin man to non-kin. Such factors acting in combination predict limited male-mediated gene flow, which will promote social structure within a population by the formation of stable kin clusters, and facilitate a rapid rise in allelic coancestry and/or inbreeding. In this study we utilize hypervariable microsatellite polymorphisms to examine the extent of social affiliation between relatives in a moorland population of grouse from NE Scodand. Levels of genetic relatedness between individual male red grouse occupying territories at Glas Choille in die spring and autumn of 1995 were examined, and kin clusters delimited. Nine kin groups (mean size = 2.4 individuals) were identified prior to breeding in the spring, which increased to 11 kin groups (mean size =4.0 individuals) when territories were reformed in the autumn. The majority of tiiose individuals that were recruited into the adult population during the autumn already had a first-order male relative established, supporting the hypothesis that recruitment is facilitated by behavioural interactions among relatives. The demographic and population genetic consequences of philopatric recruitment and kin clustering are examined and discussed.     

Microsatellite DNA markers for Lysiphlebus testaceipes

Microsatellite loci were isolated from the aphid parasitoid Lysiphlebus testaceipes (Hymenoptera: Braconidae). Ten loci were obtained from an enriched partial genomic library. Genetic diversity was analysed at seven of these loci and two natural populations, one on oleander and one on citrus. The observed number of alleles ranged from one to 17, and the observed heterozygosity ranged from 0.37 to 0.82. In both populations, no departure from Hardy–Weinberg equilibrium was detected except for one locus. The differentiation between the two populations was characterized by an F_ST of 0.09.