Comparative Aspects of Energy Metabolism in Plant Trypanosomatids

ABSTRACT. The energy metabolism was compared among four different representatives of the genus Phytomonas isolated from different plants and localities: the sieve tubes of the hartrot-infected coconut palm in French Guyana, the latex fluid of Euphorbia hyssopifolia in French Guyana and the fruits of tomato and cherimoya in Spain. All four isolates produced acetate, ethanol, glycerol and glycine as metabolic end-products. In addition, small amount of succinate and pyruvate were excreted. Only minor quantitative differences were observed in the four isolates. Glycosomes, harboring the glycolytic enzymes, were present in all isolates. No evidence was found for an active involvement of the mitochondrion in metabolism. Respiration was insensitive to the classical inhibitors of the respiratory chain, such as antimycin and potassium cyanide, but inhibited by salicylhydroxamic acid. No evidence was found for the functioning of a citric-acid cycle. It is concluded that representative of this genus share the same highly active carbohydrate metabolism combined with a complete suppression of mitochondrial activity.     

Daily patterns of mixing and nutrient concentrations during early autumn circulation in a small sheltered lake

1. Autumn circulation in lakes is currently conceived to occur very rapidly, being controlled mainly by wind‐power dynamics, decreasing irradiance and heat flux. In addition, autumn mixing is usually related to nutrient redistribution in the vertical column, resulting in its overall increase. To test these assumptions, mixing and nutrient dynamics in a Spanish small, wind‐sheltered, mesotrophic, seepage lake were studied daily during autumn circulation. 2. The seasonal erosion of the pycnocline in Las Madres Lake was the outcome of vertical and horizontal exchanges of heat and matter. The overall mixing of the water column lasted 3 months, which was an unexpected period for a rather shallow lake. Two periods of mixing could be envisaged until full circulation was attained. First, a slightly faster period of pycnocline deepening than that predicted by the heat flux and wind stress model of Fisher et al. (1979) occurred for 41 days, mixing most of the water column down to within two meters of the bottom. Then a much slower process took place promoting frequent instability of the bottom layer and resulting in entire mixing in a further 52 days. 3. Vertically, the whole mixing process was a response to weak surface cooling, resulting from the mild air temperatures of the semiarid climate of the area, and weak wind stress, because of low wind fetch and high shelter. Horizontally, a gravity current transporting cold, denser water from western shallower areas of the lake and materials produced by the decomposition of organic matter of littoral origin may produce a bottom layer of increased density, thus impinging on vertical stability. Seepage inputs of water of roughly constant temperature might also have increased bottom density. Bottom density enhancement resulted in a double diffusion process. 4. Only in‐lake nitrogen content increased until full circulation was attained, whereas carbon showed no trend and phosphorus declined. External processes, such as seepage exchange and atmospheric deposition, coupled to internal processes, such as nitrification, oxidised phosphorus precipitation and complexation with organic carbon, might have been responsible for the areal nutrient patterns observed. 5. Our study demonstrates that current models of water column mixing and nutrient redistribution in lakes during autumn circulation must be improved to encompass the effects of external inputs, including horizontal heat and matter exchange.     

Karyomorphology, heterochromatin patterns and evolution in the genus Ophrys (Orchidaceae)

Karyotype structures and heterochromatin distribution in representative taxa of the genus Ophrys are compared, based on Feulgen-stained and banded somatic metaphase chromosomes. The karyotypes of Ophrys iricolor , O. lupercalis , O. caesiella , O. lutea , O. lunulata , O. x. tardans , O. apifera , O. praecox , O. lacaitae and O. insectifera are described for the first time. The karyological analyses indicate the relationships among the species with respect to asymmetry indices and heterochromatin content. Chromosomal differences have been helpful in clarifying the taxonomic position of Ophrys species that do not have clear affinities. The representative species of Araniferae , Fuciflorae and Ophrys sections exhibited the most asymmetrical karyotypes, while chromosome complements of the O. fusca–O. lutea group, of O. tenthredinifera and of O. bombyliflora proved to be less asymmetrical. Weakly heterochromatic chromosomes, with heterochromatin present mostly in thin centromeric bands, characterize Ophrys C-banded karyotypes. Chromomycin A₃ (CMA) staining revealed that the analysed species exhibit a weak pattern of CMA⁺ bands at centromeric, intercalary or telomeric regions. No DAPI bright blocks were observed. The significance of the karyological data is discussed with regard to the relationships between the analysed species. © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society , 2005, 148 , 87–99.     

The Ultrastructure of Specimens of Paramecium multimicronucleatum Impregnated with Silver by the Fernández-Galiano Method1

Transmission and scanning electron microscopy of specimens of Paramecium multimicronucleatum treated with the Rio-Hortega silver-impregnation method as modified by Fernández-Galiano demonstrate that considerable deposition of silver occurs around the kinetosomes, especially at the level of the basal plate and also at the proximal end of the kinetosome. In addition, silver is heavily deposited within the kinetodesmal fibers, in the fibrous matrix that surrounds the postciliary and transverse microtubules, in the connective structures observed between the two kinetosomes of a pair and between the kinetodesmal fiber and the anterior kinetosome, and in the trichocysts. Differences and similarities in sites of deposit when other methods of silver impregnation are employed are discussed and the particular value of the present technique in studies of ciliate systematics and phytogeny is stressed.     

Histological characterization of the spawning process in the catarina scallop,Argopecten ventricosus (Sowerby II, 1842) induced by thermal shock and serotonin injection

Summary

The histology of the spawning catarina scallop Argopecten ventricosus was studied to characterize cellular and anatomical changes occurring along the gonad-kidney pathway. Broodstock were conditioned for 25–30 days and induced to spawn with two methods: thermal shock and serotonin by intracardiac injection. Samples of the kidney-gonad-digestive gland complex were fixed at the sperm and oocyte stages of gamete emission and at the end of spawning. Both induction methods elicited gametes, and no particular difference in the microscopic anatomy of the acini-kidney pathway was detected. However, serotonin injection, apart from producing a rough valve opening, sporadic movement (opening and closure of valve), and pronounced foot extension, induced gamete emission in less time than thermal shock. Primary gonad ducts opened to acini to permit sperm emission; at the same time, germinal vesicles broke down in female acini and meiosis restarted. Shortly afterward, oocytes gradually changed form from typically poly-hedral to a more malleable form. This probably contributed to oocyte transport through ciliary activity along the gonad and kidney ducts. Nucleoli disintegration, chromosome condensation, and appearance of meiotic figures were observed along the acini-kidney pathway. Although sperm and oocytes were sometimes observed in gonad or kidney ducts, self-fertilization was rarely observed.     

Daily variations in the optical properties of a small lake

1. The major components of the underwater light field (ULF: vertical attenuation, absorption, scattering and suspensoids including plankton fractions) of Las Madres Lake, a small wind‐sheltered, oligohumic lake in Central Spain, were investigated daily over a period of 3 months at the onset of vernal circulation. 2. Gilvin, arising mostly from the decomposition of reeds in the littoral in autumn, was the main component of vertical attenuation, and its variability explained the highest fraction of absorption variability. Tripton appeared to be the main factor responsible for scattering, and might have resulted from dust deposition from the surrounding mining land. The plankton community played a minor role in attenuation, absorption or scattering throughout the investigation period. 3. Vertical and horizontal mixing dynamics may control the ULF to a certain extent, as most optical properties changed within different mixing periods and poor advective exchanges may have resulted in uneven distribution of water colour in this small lake. 4. Time series analysis showed that most autocorrelations were shorter than a week, inherent properties (absorption, scattering) being delayed longer than apparent properties (attenuation, transparency) as a result of their lower dependence on solar irradiance. A 2‐day lag was observed in cross‐correlations between either gilvin and absorption or tripton and scattering. When different mixing periods at early circulation were considered, however, ULF components changed their relationships and delays with suspensoids and dissolved substances over such periods, probably tracking the dynamics of their controlling factors. 5. Our study, and others at daily, weekly, seasonal, interannual and long‐term scales, demonstrates that ULF is a system upon which different processes are operating at different time scales. Contrary to expectations, however, the variability in the ULF does not increase with time scale and depends partly upon the trophic status of lakes.     

Fossil water striders in Cretaceous French amber (Heteroptera: Gerromorpha: Mesoveliidae and Veliidae)

Fossil gerromorphan bugs from the Cretaceous (Albian–Cenomanian boundary) amber of Charentes, SW France, are reviewed. A larva described by Perrichot et al. (2005) as incertae familiae within the Gerromorpha is now placed in the Mesoveliidae. Three new genera and species are also described and illustrated: Emilianovelia audax Solórzano Kraemer & Perrichot, gen. et sp.n. , and Malenavelia videris Solórzano Kraemer & Perrichot, gen. et sp.n. , which are placed in the Mesoveliidae: Mesoveliinae; and Arcantivelia petraudi Solórzano Kraemer & Perrichot, gen. et sp.n. , which is the first Mesozoic member of the Veliinae. The relationships between these fossils and their palaeoecology are discussed. The new discoveries confirm the antiquity of the semi‐aquatic gerromorphans, particularly the clade (Veliidae + Gerridae). The habitat is described as aquatic and likely marine‐influenced, yet adaptation to a fully marine habitat in these gerromorphans remains difficult to establish. This published work has been registered in ZooBank, http://zoobank.org/urn:lsid:zoobank.org:pub:F8C034B8-7BD0-4C03-B8FC-CD81D75C7001 .