Faunal and chemical dynamics of some acid and alkaline New Zealand streams

SUMMARY 1. Water from acid (pH 4.3–5.7), brown water streams was low in alkalinity (0–2.3 g m^?3 CaCO₃) and conductivity (2.5–4.1 mS m^?1) but contained relatively high concentrations of dissolved organic carbon (6.6–16.3 gm^?3). In contrast, alkaline (pH 6.6–8.0), clearwater streams had high CaCO₃ (12.6–57.6 g m^?3) and conductivity (3.7–22.3 mS m^?1) but low dissolved organic carbon concentrations (0.3–4.7 g m^?3). 2. Total reactive aluminium (Al) concentrations were high in acid streams (123–363 mg m?³) but never exceeded 84 mg m?³ in alkaline streams. Acid-soluble and organic monomeric Al were the major Al species in the acid streams (31–168 and 84–178mg m?³, respectively). Concentrations of toxic inorganic monomeric Al were low in all streams (<50mg m?³). 3. Sixty-four invertebrate taxa were collected from the alkaline streams compared to forty-seven from the acid sites. Numbers of taxa in specific insect orders were similar at all sites, however. Benthic faunas at most sites were dominated by the mayfly Deleatidium sp. and chironomids. 4. Overall, mean densities of benthic invertebrates were 2.4–4.8 times higher in alkaline streams than acid streams. No seasonal patterns of abundance were evident at any site. 5. Temporal variability of invertebrate densities was correlated with stream channel stability such that fluctuations in densities declined as stability increased. 6. Sources of dissolved organic carbon and aluminium in acid, brown water streams are discussed. We suggest that changes in the food supply available in acid streams account for the depauperate faunas found there.     

Local population differences in emergence of cabbage root flies from south-west Lancashire: implications for pest forecasting and population divergence

ABSTRACT.

• 1 Emergence of cabbage root fly, Delia radicum (L.), from overwintering populations of puparia collected from twenty-one sites in south-west Lancashire, was extremely variable.
• 2 The patterns of emergence indicated that there were two extreme biotypes, one with early- and the other with late-emerging flies. There was also evidence of an intermediate biotype, tending more to early than to late emergence.
• 3 This gradient of biotypes, or clinal divergence, was maintained by populations breeding at different times and by females mating close to their sites of emergence. Non-dispersive females then perpetuated their genotype within their own locality.
• 4 The time of emergence was not obviously associated with the type of host-crop on which larvae had developed.
• 5 The late-emerging biotype was most prevalent around Halsall. The minimum distance between populations of the late- and the early-emerging biotypes was 16 km. 20 km south-east from Halsall only half of the fly population was early-emerging, possibly a result of a displacement of the Halsall biotype by the prevailing NW wind.
• 6 Regional-based forecasts will need to take into account the emergence characteristics of the populations to predict the peak periods of cabbage root fly activity adequately in south-west Lancashire and other areas where emergence patterns differ.

     

Influence of nymphal size, sex and morphotype on microdistribution of Deleatidium (Ephemeroptera: Leptophlebiidae) in a New Zealand river

• 1 The interaction of water depth and velocity with size, sex and morphotype of nymphs belonging to the leptophlebiid mayfly genus Deleatidium was investigated in a New Zealand river.
• 2 Velocity had a significant effect on distribution such that larger nymphs tended to be found more commonly in faster water. Depth also influenced size distribution, but in different ways at different sites.
• 3 Water velocity or depth alone did not significantly influence the distribution of sexes (1.0 mm head width), but the combined effect of these two factors was significant. Final instar males appeared to be relatively more abundant in slower water than final instar females.
• 4 Nymphs (1.0 mm head width) belonging to the informal lillii group (apically pointed gills) were present over a wide range of depth and velocity conditions, but those belonging to the myzobranchia group (round-tipped gills) were largely restricted to fast water (>0.9ms^?1).
• 5 Several mechanisms thought to cause variations in microdistribution are discussed. These include differential effects of oxygen availability, food requirements and drag forces, nymphal behaviour, and selection of oviposition sites by adults.

     

The art of otology

Management of chronic ear infections dependent on recognition of the differences (pathological and clinical) between tympano-tubal lesions and attico-antral disease. Chronic suppurative otitis media as a reason for rejection for military service. Statistics obtained from the Ministry of Labour and National Service. Relative incidence of tympanic and attico-antral disease in a series of 500 hospital patients at the present time. Resistant chronic tympanic disease still a problem. Relation to acute suppurative otitis media. Recurrent and relapsing attacks of acute otitis media. Does early chemotherapy interfere with development of immunity?Problems presented by acute otitis media likely to be elucidated by the general practitioner rather than by the otologist. The general practitioner's opportunities for research in this clinical problem. Incidence of ear diseases in average general practice.Training of medical students in diseases of the ear, nose and throat. Methods of instruction followed in the teaching schools of Great Britain and Northern Ireland and attitude of the Examining Bodies to this subject. The contribution of otologists to the education of doctors.Some observations on facial paralysis. Importance of prognosis. Different criteria in early and late stages of paralysis. Reasons for abandoning the faradic-galvanic tests in the management of facial paralysis. Use of constant current square pulse stimulators in early days of facial paralysis. Electromyography of value in later stages.Present-day difficulties in acquiring skill for facial nerve surgery. Importance of the stylomastoid artery. Recent investigations on the blood supply of the facial nerve: gross vascular pattern and the interfascicular plexus. Further work necessary to relate these anatomical facts to the condition of Bell's palsy.     

ACETYLTRIETHYLCHOLINE: A CHOLINERGIC FALSE TRANSMITTER IN CAT SUPERIOR CERVICAL GANGLION AND RAT CEREBRAL CORTEX

The accumulation and metabolism of [¹⁴C]triethylcholine by cat superior cervical ganglia [rested or stimulated (20 Hz)] and by rat cerebral cortex minces was measured. In ganglia, preganglionic nerve stimulation increased the accumulation (2.4 fold) and the acetylation (5.7 fold) of triethylcholine; however the depletion of the ganglion's acetylcholine content was 9.5 times greater than the amount of acetyltriethylcholine synthesized. In the presence of eserine, neither stimulated nor rested ganglia synthesized any extra (surplus) acetyltriethylcholine. It is concluded that the rate-limiting step in acetyltriethylcholine synthesis is the acetylation of triethylcholine by choline acetyltransferase. Subsequent preganglionic nerve stimulation of ganglia, which had been stimulated during the exposure to [¹⁴C]-triethylcholine, caused the increased release of only acetyltriethylcholine; the release was frequency-dependent, required the presence of Ca²⁺, and was blocked by increasing the ratio of Mg²⁺/Ca²⁺ in the perfusion fluid. All of the acetyltriethylcholine which had been accumulated was available for release. Rat cerebral cortex also accumulated triethylcholine and acetylated about 3% of the accumulated choline analogue. Subsequent stimulation by high K⁺ (46 mM)-atropine (3 μM) caused the increased release of acetyltriethylcholine from the cortex and this release required the presence of Ca²⁺. Triethylcholine can therefore form a cholinergic false transmitter in the cat superior cervical ganglion and the rat cerebral cortex.     

Survival of Rio Grande Wild Turkeys on the Edwards Plateau of Texas

Abstract: The southeastern portion of the Edwards Plateau of Texas, historically a stronghold of Rio Grande wild turkeys (Meleagris gallopavo intermedia), has seen a decline in turkey numbers since the 1970s. Because adult and juvenile survival are key parameters affecting turkey population dynamics, we used radiotagged individuals to compare Rio Grande wild turkey survival in areas of suspected decline versus stable portions of the Edwards Plateau during 2001–2003. Reproductive period (breeding or nonbreeding) had an impact on survival, but differences in age, sex, or region did not influence survival. Model averaged estimates of monthly survival were 0.97 (SE = 0.005) for nonbreeding periods and 0.96 (SE = 0.007) for breeding periods. Our results indicate juvenile and adult survival in the declining areas was similar to survival in the stable areas of the Edwards Plateau. This suggests causes of the decline might be associated with differences during other life-history stages, such as nest success or poult survival, although we cannot rule out the possibility juvenile or adult survival contributed to the decline in the past. This situation demonstrates why wildlife managers should be cognizant of the implications of initiating long-term monitoring programs after changes in population status occur, rather than initiating them in expectation of such changes.