Behavioural variation in natural populations. V. Morphological correlates of locomotion in the garter snake (Thamnophis radix)

A series of morphologieal and locomotor performance variables was measured in a population of newborn garter snakes to determine whether performance capacity has a significant morphological basis in these animals. Morphological traits measured were body length and mass, number of body and tail vertebrae and numbers of vertebral abnormalities. Locomotor performances included burst and mid-distance speed and distance and time crawled before anti-predator displays were assumed. All performance variables were repeatable in daily replicate trials ( P < 0.001). Individual burst speed, mid-distance speed, and distance crawled were significantly correlated pairwise ( P < 0.01). Most morphological and performance variables had a significant mass dependence (static allometry), although the effects were rather weak ( r ² < 0.1, except for body length): larger animals performed better and had fewer abnormalities. There were significant associations between some morphological traits and locomotor performance. Morphological factors accounted for 19% of the variation in mid-distance speed and 14% of the variation in antipredator behavior by multiple regression analysis. Canonical correlation of all performance and morphological variables simultaneously accounted for 24% of the observed variation in performance. Numbers of body and tail vertebrae (assayed by scale counts) had an interactive effect on speed of locomotion.     

Ciliate Protozoa in the Rumen of Kafue Lechwe, Kobus leche kafuensis, in Zambia, with the Description of Four New Species

ABSTRACT The composition of the rumen ciliate fauna in 76 Kafue lechwe inhabiting a limited area in Zambia was surveyed and five genera containing 24 species with 16 formae belonging to the family Ophryoscolecidae were identified. Four new species belonging to Diplodiniinae were recognized and described as Diplodinium lochinvarense n. sp., Diplodinium leche n. sp., Diplodinium zambiense n. sp., and Metadinium ossiculi n. sp. In addition, Ostracodinium gracile form fissilaminatum Dogiel, 1932 was found for the second time and described as Metadinium fissilaminatum n. comb. The species composition was fairly unusual. Seven of the species have been found only in African wild antelopes and these species were found more frequently than cosmopolitan species. There was no evidence of isotrichid species. The average density of ciliates per 1 ml of the rumen fluid was 25.7 times 10⁴, and the number of ciliate species per head of host was 10.8.     

Germination of Nosema algerae (Microspora) Spores: Conditional Inhibition by D2O, Ethanol and Hg2+ Suggests Dependence of Water Influx upon Membrane Hydration and Specific Transmembrane Pathways

ABSTRACT. The germination of microsporidian spores under conditions expected to affect water flow across the plasma membrane-wall complex was studied by assessing their responses to in vitro stimulation with Na⁺ or K⁺. Partial or full substitution of common water with D₂O, which more effectively coats ions and electrostatically-charged cell surfaces with relatively stable hydration layers, delayed and inhibited spore germination in a concentration-dependent manner; yet, preincubation in 100% D₂O did not change the normal response to standard stimulation. Water structure-breaking conditions, such as an increase in temperature (within the 15° C to 40° C range) or in ionic strength (2- to 10-fold normal), opposed the inhibition by D₂O and allowed significant stimulation by Li⁺, the monovalent cation with the largest hydration diameter and a usually weak stimulant action on the spores. Ethanol, known to reduce water permeation across cell membranes and phospholipid bilayers, also caused a powerful and dose-dependent (1% to 4% v/v) inhibition of spore germination, but pretreatment with ethanol did not affect the normal response. HgCl₂, an inhibitor of specific water channels, blocked spore germination at just 250 μM in the normal stimulation solution irrespective of the temperature, and permitted only a delayed response in high salt stimulation solutions. However, the inhibition by Hg²⁺ was abolished by the simultaneous presence of 2-mercaptoethanol in the medium. These results suggest (1) that spore germination is keenly dependent upon the hydration states of both the plasma membrane-wall complex and the stimulant ions, and (2) that osmotic water flows into the spores through specific transmembrane pathways with critical sulfhydryl groups, i.e. analogous to the water channels that facilitate water movements across the plasma membranes of highly permeable cells.     

Modelling the ecosystem effects of nitrogen deposition: Simulation of nitrogen saturation in a Sitka spruce forest,Aber, Wales,UK

A new model for simulating nitrogen leaching fromforested ecosystems has been applied to data from anexperimentally manipulated 30-year-old Sitka sprucestand. The manipulation experiment (at Aber, in north-western Wales, UK) was part of the European NITREXproject and involved five years of additions ofinorganic nitrogen to the spruce stand. The model(MERLIN) is a catchment-scale, mass-balance model thatsimulates both biotic and abiotic processes affectingnitrogen in ecosystems.The structure of MERLIN includes representationsof the inorganic soil, one plant compartment and twosoil organic compartments. Fluxes in and out of thesimulated ecosystem and transfers between compartmentsare regulated by atmospheric deposition, hydrologicaldischarge and biological processes such as plantuptake, litter production, immobilization,mineralization, nitrification and denitrification.Rates of nitrogen uptake, cycling and release amongpools are regulated by carbon productivity, inorganicnitrogen availability and the C:N ratios of theorganic pools. Inputs to the model are temporalsequences of carbon fluxes and pools, hydrologicaldischarge and external sources of nitrogen.The NITREX experiment at Aber began in 1990 withweekly additions of ammonium nitrate(NH4NO3) at a rate of 35 kg N ha-1 yr-1.Data were collected from both control andtreatment plots within the stand. The site-intensivedata from the control plots at Aber were augmented bydata taken from a chronosequence of 20 Sitka sprucestands and data from a survey of 5 moorland catchmentsin the same region to providecalibration data for the model. The data were used toestablish current conditions at the Aber site and toreconstruct historical sequences of carbon fluxes andpools from 1900 to the present day with which to drivethe model. The reconstructed sequences included anincrease in nitrogen deposition and a vegetationchange from moorland to plantation forest in 1960. Thecalibrated model was then used to predict the effectsof the experimental nitrogen additions begun in 1990.MERLIN successfully reproduced the observedincrease in NO3 leaching from aging spruce standsthat results from forest maturation and increasednitrogen deposition (as inferred from thechronosequence and forest survey data in the region).MERLIN also correctly predicted the increases insoilwater NO3 concentrations, the changes innitrogen content of tree and soil organic matterpools, and the changes in nitrogen fluxes that occurin spruce stands in response to increased nitrogeninputs (as observed in the nitrogen additionexperiment).     

The impact of sediment reworking by opportunistic chironomids on specialised mayflies

1. Bioturbation, by definition, changes the structure and properties of sediments, thereby altering the environment of the bioturbator and other benthic species. In addition to the indirect effects of sediment reworking (e.g. changes in water quality), bioturbating species may also directly interfere with other species via competition. This study aims, therefore, to examine both the direct and indirect effects of sediment reworking by an opportunistic detritivore on survival and growth of a specialised mayfly species. 2. Bioturbation was imposed by adding different densities of the midge Chironomus riparius to clean and polluted sediments. Changes in water quality and sediment properties, and survival and growth of the mayfly Ephoron virgo were assessed. 3. Chironomid density had a strong negative effect on the concentrations of metals, nutrients and particles in the overlying water, but increased the penetration of oxygen into the sediment. Survival and growth of E. virgo were strongly reduced in the presence of chironomids. In the polluted sediment, the activity of chironomids enhanced the negative effects of pollution on E. virgo. In the clean sediment, inhibition of the mayfly was even more pronounced. 4. This suggests that direct disturbance by C. riparius was more important than indirect changes in water quality, and over‐ruled the potential positive effects of improved oxygen penetration. The results indicated that the distribution of small insects, such as E. virgo, can be limited by bioturbating benthic invertebrates.     

Nosema algerae n. sp. (Cnidospora, Microsporida) a Pathogen in a Laboratory Colony of Anopheles stephensi Liston (Diptera, Culicidae)

SYNOPSIS. A new microsporidan, Nosema algerae n. sp., was found in a laboratory colony of Anopheles stephensi. The microsporidan infects a variety of tissues of both larvae and adults and is highly pathogenic for its host. The structure and life cycle of the microsporidan under the light and electron microscope is described and its relationship to other Nosema species infecting mosquitoes is discussed.     

Fossil oaks of Primorye, USSR, and the origin of oak forests

This paper gives a new locaticn for fossil oaks in Rettikhovka, Primoiye, USSR, from coal-bearing deposits of Miocene age. The large number of different oak species at the above site (leaf imprints) is evidence of their important role in the plant communities of the past. The authors agree with those scientists who maintain that the extant oaks in the Soviet Far East are of autochthonous origin. Two new fossil Quercus species with compound-lobed leaves are described, viz. Q. sichotensis Ablaev & Gorovoi and Q . sp.     

Spontaneous and Evoked Quantal Transmitter Release at a Vertebrate Central Synapse

THIS report deals with some of the statistical properties of quantal transmitter release at the Mauthner fibre-giant fibre synapse in the hatchetfish Gasteropelecus and the way in which these properties are modified by presynaptic intracellular depolarization. The experiments reported indicate that Poisson statistics describe transmitter release in the hatchetfish at low, but not at high, release levels.     

Degradation of Paramylon by Euglena gracilis

SYNOPSIS. Protozoa of the order Euglenida contain a polysaccharide storage product, paramylon, composed of 1, 3-linked glucose molecules arranged into an extremely resistant granule. An enzyme was purified from the soluble phase of Euglena gracilis which would degrade this polysaccharide to single glucose residues, providing the integrity of the paramylon granule was 1st disrupted by dilute base. This enzyme, a β-1, 3 glucanase, had optimal activity at pH 5.0 and 60 C and bound tightly to base-disrupted paramylon substrate tho not to the intact granules. The specific activity of the enzyme was doubled when cell cultures reached stationary phase, the phase where net carbohydrate utilization began. An ATP-dependent hexokinase reaction was also present in Euglena homogenate. No phosphorylase activity has been found in Euglena. It is suggested, therefore, that Euglena do utilize their paramylon as a carbohydrate reserve and the mechanism of this utilization is by exo-hydrolytic cleavage to free glucose followed by phosphorylation and glycolysis.