The Effect of Carbon Dioxide Concentratioin, light Intensity and Isonicotinyl Hydrazide on the Photosynthetic Production of Glycollic Acid by Chlorella

Glycollic acid production by Chlorella was measured by colorimetricdetermination of the acid excreted into the medium. It was foundthat glycollic acid production showed a maximum at a low concentrationof carbon dioxide but tended toward zero as the rate of photosynthesisapproached carbon dioxide saturation. Glycollic acid productionbecame measurable at light intensities approaching that requiredto saturate photosynthesis and increased steadily with furtherincrease in intensity. Treatment with isonicotinyl hydrazideresulted in an approximately threefold stimulation of glycollicacid concentration over the range of conditions used. It issuggested that the precursor of glycollic acid is ribulose diphosphate,and that isonicotinyl hydrazide acts by inhibiting the furthermetabolism of glycollic acid.     

Application of the most probable number method to estimations of entomopathogenic nematode populations in soil

The calculation of most probable numbers (mpn) was used for the estimation of numbers of infective entomopathogenic nematodes in soil. The mpn concept was first introduced in bacteriology as a means of estimating numbers of organisms in a substrate without a direct count, in cases where direct enumeration could not be applied. In the work reported here, soil samples infested with infective juveniles (IJs) of Heterorhabditis megidis (isolate HF85) were diluted with uninfested soil and the diluted soils were baited with mealworm larvae (Tenebrio molitor). The mpn of infective units of IJs in the undiluted soil was calculated. The mpn calculation was found to be applicable to entomopathogenic nematodes in soil under particular conditions. It could be successfully applied to data for the response of soil units but not to the data based on the response of individual insects, as the latter did not confirm to a Poisson series. The calculated mpn represented between 2.9 and 7.1% of the initial inoculum of IJs. It was suggested that IJs might act as a group in infecting an insect host. Using the data for Tenebrio mortality on parasitisation, the mpn based on quantal response of the mealworms would therefore not give the true density of IJs in the soil sample but the effective density, or the quantity of infective units. Although the biological significance of the infective unit needs further clarification, mpn was found to be a useful parameter for use in comparative experiments.     

Acanthamoeba comandoni and A. astronyxis: Taxonomic Characteristics of Mitotic Nuclei, "Centrosomes" and Cysts

SYNOPSIS. A new strain (F-111) of Acanthamoeba comandoni was isolated from Turtle Pond, Boston, Mass. Comparative studies of A. comandoni Pussard, 1964 and A. astronyxis Ray & Hayes, 1954 indicated that the 2 species are distinct, and that the 2 names are valid and not synonymous as proposed by various investigators. An astral or brush-pile “centrosomal body” was present near the nucleus of interphase stages of both species. During mitosis, bipolar “centrosomal bodies” were detected in A. comandoni but not in A. astronyxis. Cysts of both species were spherical and had stellate or rayed endocysts. The rays in cysts of A. comandoni extended outward and upward at different angles, and all of them were not visible in the same optical plane. In A. astronyxis, the rays extended outward from the central cyst mass, and all of them were visible in the same optical plane.     

Phylogeny of the Dictyoptera

Abstract. Relationships among six key dictyopteran taxa (Mantodea; Blattodea (excluding Cryptocercidae); Cryptocercidae; Mastotermes darwiniensis , Termopsidae and Kalotermitidae [Isoptera]) are analysed based on seventy morphological, developmental and behavioural characters. The fossil record and the 'living fossil' genera Cryptocercus, Mastotermes and Archotermopsis are discussed in detail. Exact analysis of the character state matrix by implicit enumeration (Hennig86) resulted in one cladogram, strongly supporting Blattodea + Cryptocercidae as a sister group to Mantodea, with the Isoptera as a sister group to that complex. Arrangements within the termites are equivocal, with Termopsidae and Mastotermes darwiniensis possible as the relatively most primitive element of Isoptera.     

Competitive saprophytic colonization of wheat straw

Using the ‘Cambridge method’, the effect of temperature on the colonization of wheat straw by Fusarium culmorum, Gibberella zeae, Cochliobolus sativus and C. spicifer was studied. Within the range 10–30 °C, saprophytic colonization by the four fungi was favoured by lower temperatures. This could not be attributed to the effect of temperature on the growth of the fungi in pure culture, but was probably caused by increased antagonism at higher temperatures from the general soil microflora. Contrary to previous indications, C. sativus strongly colonized straw under suitable environmental conditions.     

ANNUAL AND LUNAR REPRODUCTIVE CYCLES IN LITTORINA SAXATILIS (OLIVI) AND DIFFERENCES BETWEEN BREEDING IN THE MARINE FIRTH OF FORTH AND THE FORTH ESTUARY

Gonads were most commonly reduced in October and fullest inMar-Jun with more pronounced seasonal differences in the estuarythan in the firth. Brood-pouches accordingly were fullest inspring-early summer and emptiest in autumn-early winter. Eggsand early embryos predominated in brood-pouches of early springbut were few in Aug-Oct whereas well-developed juveniles werefew in early spring, increased in spring-summer and came topredominate in Jun-Nov. Brood-pouch loads varied with size offemale but, for a standard 10 mm female, were significantlylower in the 2 estuarine sites than in the firth. Changes inmean brood-pouch count varied only 2.5-fold during the yearin the firth but 4.10-fold in the estuary. In vitro development of eggs to shelled juveniles with the velumresorbed took some 68 d at 10°C and 32%. Eggs and late brood-pouchjuveniles were significantly heavier in the estuary than inthe firth (dry weight, ash-free dry weight (AFDW), ash weight).AFDW changed little during development while ash weight (mostlyshell) increased 3.5-4.4-fold. In a laboratory tide tank, femalesreleased 60 d means of <1.3 juveniles d^–1; more inmid- and late year than in Jan-Mar, more from upshore firthfemales than from low shore or estuary females, more when heldat high tide-tank levels than at lower levels, and generallyat rates comparable to release in containers held at the siteof origin. Egg production in laboratory females did not keeppace with release of young and, at the end of trials, brood-pouchcounts were mostly lower than in contemporary free winkles.Females that had released most (e.g. at high tank levels) containedleast brood-pouch embryos and young subsequently. Release of young in the tide tank was markedly faster at timesnear new moon (often reaching or exceeding 2 female^–1d^–1) than near full moon (often <1 female^–1 d^–1).This lunar fluctuation was clearest in fast-releasing sets heldat high- or mid-tide tank levels. It was not observed in Jan-Mar(when release from most females was slow) nor in females atlow tank levels. (Received 3 September 1990; accepted 8 November 1990)     

Stress Responses in Avian Embryos

The day 13–14 chicken embryo is a useful model for studieson prenatal stress responses. Free dopamine, norepinephrineand epinephrine in its plasma, amniotic and allantoic fluidrespond to a variety of stresses. The allantoic fluid also containsconjugated catecholamines and conjugated steroids. However,a blood/allantois barrier excludes free thyroid hormones andfree steroids, and insulin. On the other hand, the allantoicfluid contains at least 40 amino acids (including six excitatoryamino acids) and related compounds. Most, possibly all, componentsof the allantoic fluid are regulated at specific blood/allantoisand amnion/allantois barriers, and they respond to ethanol stressand metabolite loading differentially. The avian allantois isa depot for important metabolites and messenger substances whichseems to be controlled by as yet unidentified hormones     

CO2 effects on the water budget of grassland microcosm communities

Experimental grassland ecosystems, in microcosms 0.2 m in diameter and with a 0.95 m soil column, varied in their responses to elevated partial pressure of CO₂ (pCO₂) and altered moisture inputs. Ecosystems on moderately fertile sandstone soil and with a typical mix of moderately fast-growing sandstone species, responded to elevated pCO₂ with decreases in mid-season evapotranspiration of nearly 50%. This pattern reversed at the end of the growing season, and sandstone ecosystems under elevated pCO₂ continued active transpiration farther into the summer drought. The sandstone ecosystems appeared to convert mid-season water conservation into increased late-season growth. Effects of increased pCO₂ on ecosystem evapotranspiration were much smaller in ecosystems with very infertile serpentine soil and a diverse mixture of slow-growing serpentine species.     

Ammonium and phosphate regenerationby the zooplankton of an Amazon floodplain lake

SUMMARY. 1. Regeneration of ammonium and phosphate by macro-zooplankton (Cladocera. adult copepods. and copepodites) was measured in Lake Calado. an Amazon floodplain lake, Macrozooplanktonabundances ranged between 1×10⁴ and 3×10⁵ individuals m⁻².
2. Phosphate regeneration ranged from 0.2 to 1.3 μ mol PO₄ m⁻² b⁻¹at station 1. located 2 km from the Solimoes River, and from 1.6 to8.3 μ mol PO₄ m⁻² h ⁻¹ at station 3, located 7 km from the SolimoesRiver. Ammonium regeneration at stations 1 and 3 ranged from 1.7 to11.9 and from 13.4 to 77.2 μ mol NH₄ m⁻² h⁻¹. respectively.
3. Zooplankton regenerated ammonium and phosphate at similarrates during rising and falling waier. Regeneration by macrozooplankton was low compared to other tropical lakes and compared to microbesand microzooplankton in Lake Calado.