The Numbers and Proportions of Testacea and Ciliates in Litters and Soils

SYNOPSIS. The numbers and kinds of testacea and ciliates were studied in the litters and soils of 23 sites, from temperate and subtropical coniferous and deciduous forests, and grasslands. In coniferous forests, testacea were 10 times or more abundant than ciliates, and numbered 10,000–24,000/g (wet weight) in litters and up to 8,000/g in soils. Ciliates numbered up to 1,500/g, but averaged less than 600/g in litters and less than 300/g in soils. Under deciduous vegetation, ciliates approached, equaled, or exceeded testacea, and numbered 1,000–5,000/g in litters, while remaining about the same in soils. Temperature and soil influence vegetation types, and their rates of litter decay affect the protozoa. Moisture favors numerical dominance of certain species. Among testacea, several species dominate in a particular habitat; among ciliates, the genus Colpoda dominates in almost all litter and soil habitats.     

Periphyton production in Fort River, Massachusetts

SUMMARY. The primary production and general ecology of a periphyton community of a New England, lowland stream were studied over a seventeen-month period. Temperature, light, periphyton chlorophyll-α, and community structure were monitored regularly. Seasonally distinct chlorophyll peaks coincided with the light maximum in early May, just prior to the appearance of leaves of riparian trees, and again in autumn after terrestrial leaf fall. During midwinter, despite low light and temperature levels and high stream discharge, mean chlorophyll concentrations remained similar to summer values.
A mathematical expression relating periphyton photosynthesis per unit chlorophyll-α to temperature, light and periphyton density was established with submersible light-dark chambers in situ . Survey data collected over the study period were employed in the empirical equation to estimate seasonal variations in periphyton primary production. Weekly mean daily estimates of periphyton gross production ranged from < 0.1 g O₂ m⁻², during midwinter, to 6.5 g O₂ m⁻² during early May. Estimated annual periphyton gross production and respiration were 0.58 and 1.27 kg O₂ m⁻², respectively. Factors influencing seasonal variations of Fort River periphyton standing crop are discussed.     

Formation and Fate of Extranuclear Chromatin Bodies in Tetrahymena

The fate of extranuclear chromatin bodies (ECBs) formed by exclusion of macronuclear material at the time of karyokinesis was followed quantitatively in Tetrahymena pyriformis strain GL-I. In a logarithmic growth phase culture, 51% of the dividing cells produced one (43%) or more (8%) ECBs. Most of these gradually disappear before the next cell division, but ? 13% are retained and carried into subsequent cell cycles. The random distribution of ECBs into anterior or posterior daughter cells, their staining and morphological characteristics, and their rapid loss in cells in starvation medium, all indicate that ECBs play no more of a role in cellular activity than that of an internally produced food vacuole.     

Alanine Aminotransferase and Aspartate Aminotransferase in Leishmania tarentolae1

SYNOPSIS. Culture stages (promastigotes) of Leishmania tarentolae were tested for alanine aminotransferase (E.C.2.6.1.2) and aspartate aminotransferase (E.C.2.6.1.1.). Neither enzyme was detected in crude cell extracts. After starch block electrophoresis, however, both transaminase activities were found in proteins migrating toward the anode. Only one species of each enzyme was found. Using coupled enzyme assay systems, the following physical and kinetic properties were seen: 1) aspartate aminotransferase was inhibited by α-ketoglutarate concentrations above 1.68 × 10^?2 M and alanine aminotransferase was inhibited by concentrations higher than 1.34 × 10^?2 M; 2) the Michaelis constant (Km[α-ketoglutarate]) was 5.4 × 10^?4 M for aspartate aminotransferase and 3.0 × 10^?4 M for alanine aminotransferase; 3) maximum activity was found at ?pH 8.5 (broad range between pH 7.75–9.0) for aspartate aminotransferase whereas maximum activity for alanine aminotransferase was ?pH 7.2 (range between pH 7.0–7.5); 4) both enzymes lost half of their activity after 4 days at 8 C; 5) aspartate aminotransferase was most active at 35 C and completely inactivated at 59.5 C, alanine aminotransferase exhibited maximum activity at 29.5 C and was completely inactivated at 61 C; and 6) neither enzyme showed enhanced activity with added pyridoxal phosphate.     

Complementary video and acoustic recordings of foraging by two pest species of slugs on non-toxic and molluscicidal baits

The effects of adding the molluscicides methiocarb and metaldehyde to pelleted foods on the encounter, acceptance, feeding and post-meal stages of the foraging sequence of the slugs Deroceras reticulatum and Arion distinctus have been studied using two complementary laboratory techniques - video and acoustic recordings. Whereas non-feeding slugs encountered wheat grains at random, slugs which fed on wheat grains or pellets encountered them more frequently because of changes in locomotor pattern and olfactory attraction. Slugs would almost always feed on the first pellet they found, regardless of the presence or absence of molluscicide: thereafter they fed on only one pellet in every four encountered. Far fewer slugs accepted wheat grains. Slugs ate much less from pellets containing molluscicide, and meals were more irregular. The relative amounts of non-toxic pellets of various types which were eaten gave no indication of the relative amounts eaten when molluscicide was added. Meal length did not correlate well with meal size on different pellet types because softer pellets were eaten faster. Most Deroceras fed several times on non-toxic pellets or pellets containing methiocarb, although subsequent meals were shorter than the first meal. Most returned to shelters by dawn. In contrast, metaldehydefed slugs were rapidly immobilised; they seldom fed again, moved little, and few regained shelter. Arion were also inhibited after methiocarb meals but Deroceras were not. Arion distinctus moved less, ate less during a meal, and had fewer meals on nontoxic baits than Deroceras reticulatum.     

Potential impacts of wave‐powered marine renewable energy installations on marine birds

One potential approach to combat the impacts of climate change is the expansion of renewable energy installations, leading to an increase in the number of wave‐powered marine renewable energy installations (MREIs). The consequences of increased use of these devices for birds are unknown. Here we describe the wave‐powered energy‐generating devices currently either operational or in development and review the potential threats and benefits of these to marine birds, their habitats and prey. Direct negative effects include risk of collision, disturbance, displacement and redirection during construction, operation and decommissioning. Above‐water collision is a particular concern with wind‐powered devices, but, because of their low profiles, the collision risk associated with wave‐powered devices is likely to be much lower. Conversely, wave devices also pose the novel threat of underwater collision. Wave‐energy‐generating devices may indirectly impact marine birds by altering oceanographic processes and food availability, with implications for trophic cascades. Through appropriate mitigation, wave‐powered MREIs offer the potential to enhance habitats. Direct positive effects may include provision of roosting sites, and indirect positive effects may include prey aggregation due to suitable substrates for sessile organisms or because they act as de facto protected areas. The cumulative effect of these could be the improvement and protection of foraging opportunities for marine birds. Recent studies have been critical of the methods used in the assessment of wind‐powered MREI impacts, which lack sufficient sample sizes, controls or pre‐development comparisons. Here we suggest solutions for the design of future studies into the effects of MREIs. Wave‐powered MREIs are certain to become part of the marine environment, but with appropriate planning, mitigation and monitoring they have the potential to offer benefits to marine birds in the future.     

Protist Biogeography1

Autecology (cellular organelles and secretions, encystment and dispersal abilities), environmental conditions (physiological tolerances and interaction with other organisms), and evolutionary history contribute to protist biogeography, which manifests ecological and historical aspects. Ecological biogeography is seen in the influence of geochemistry on the distribution of fresh-water phytoflagellates and algae, and of moisture and vegetation type on soil-litter protists. A temporal feature is often present because many protists encyst and respond only to certain ranges of temperature and organic content. Historical biogeography has occurred by radiative host evolution on symbiotic protozoa (e.g., termite flagellates and rumen ciliates), and by the isolating effects of water currents, temperature, and density gradients on oceanic protists (coccoliths, dinoflagellates, foraminifera, radiolaria, and tintinnines). These two aspects combine in protists living on animal surfaces. Humans affect protist biogeography by increasing parasite ranges through human migrations and by water pollution. They can diminish these situations by disease control and exploiting appropriate ciliates in sewage disposal. Many free-living protozoa appear to be cosmopolitan, but mating types and isoenzyme studies suggest that speciation with its geographic connotations may be more widespread than presently appreciated.     

Effect of Berenil on Growth,Mitochondrial DNA and Respiration of Leishmania tarentolae Promastigotes*

SYNOPSIS Incubation of Leishmania tarentolae promastigotes in 1.0 μg/ml Berenil for 96 hr resulted in 33% inhibition of cell growth and 42.5% dyskinetoplasty in the cell population. The buoyant density of kinetoplast DNA (kDNA), ρ= 1.703 g/ml, remained unchanged after 96-hr exposure to the drug. Endogenous respiration as well as proline- and glucose-induced respiration dropped markedly after 36-hr exposure to Berenil. This drop occurred 12 hr before the onset of dyskinetoplasty, a result which suggests that this drug adversely affects mitochondrial respiratory activity of the promastigotes.