Changes in experimental gillnet catches from the Kafue Floodplain, Zambia, since construction of the Kafue Gorge Dam

The Kafue Floodplain fishery produces an annual fish yield of about 5000 tonnes. The 1971 closure of the Kafue Gorge Dam downstream from the floodplain modified flooding patterns. Pre-impoundment studies predicted this modification would increase fish stocks. Experimental gillnets set in 1975 and 1976 caught 18 species on a regular basis, nine of which were abundant enough for comparison with catches in similar gillnet samples taken prior to completion of the Kafue Gorge Dam. Of these nine species, experimental gillnet catches of three predator species were smaller in 1975–76 than in 1969–70. Catches of only one species increased significantly. Whether this change is due to the modified flooding pattern is unclear; unusually dry flood conditions in 1973 and increased fishing effort may have contributed.     

Observations on the breeding biology of Sarotherodon macrochir (Boulenger) in Lake Mcllwaine, Rhodesia

Sarotherodon macrochir matures at 17–18 cm standard length in Lake Mcllwaine and males grow larger than females. There is an extensive breeding season with the main breeding taking place during September-February, the hottest period of the year, which is just before the rainy season. Female S. macrochir produce about 1000 to 5000 eggs in their ovaries and can brood up to 800 eggs in their mouths. Mean brooding efficiency is about 75 % but this declines as the fish increase in size.     

Geese and Red-knobbed Coot on the Kafue Flats in Zambia, 1970–1974

The occurrence, chronology of breeding and wing-moult, and feeding habits of the Pigmy Goose Nettapus auritus, Knob-billed Goose Sarkidiornis melanotos, Spur-winged Goose Plectropterus gambensis, Egyptian Goose Alopochen aegyptiaca and Red-knobbed Coot Fulica cristata on the Kafue Flats in Zambia are described based on observations made between October 1970 and January 1974 at Lochinvar National Park and, from the air, over the central section of the Flats. The Pigmy Goose, Knob-billed Goose, Egyptian Goose and Red-knobbed Coot fed largely by grazing. They were most abundant between March and June, occurring in greatest numbers at Lochinvar. Egyptian Geese occasionally nested on the flood-plain at Lochinvar between August and January, but there was no proof of the other species nesting there. Many Pigmy Geese and male Knob-billed Geese moulted on the lagoon at Lochinvar between March and June; small numbers of Egyptian Geese and Red-knobbed Coot also moulted in the Park, the former between February and May, the latter in June and July. The Spur-winged Goose fed mostly by grazing and grubbing. Numbers on the Flats were greatest between June and November when 60,000–90,000 moved downriver as the floods subsided. Many bred between January and March in the fringing zone and moulted on the floodplain between May and July. A hydroelectric scheme, completed in 1975, may benefit the Pigmy Goose and Red-knobbed Coot but harm the Spur-winged Goose.     

The ecology of the lechwe, Kobus leche kafuensis Haltenorth, in Lochinvar National Park, Zambia, as affected by the Kafue Gorge hydroelectric scheme. Herbage digestibility in free-living antelope

A method of collecting rumen fluid from free-living antelope is presented, together with the in vitro procedure used to try to estimate the digestibility of the herbage grazed by them. Modifications to this procedure are suggested, which it is thought would allow the calculation of a meaningful equation relating these data to digestibility estimates obtained by a chemical method.     

Concurrent infections of Fasciola, Schistosoma and Amphistomum spp. in cattle from Kafue and Zambezi river basins of Zambia

This study investigated interactions among Fasciola gigantica, Schistosoma spp. and Amphistomum spp. concurrent natural infections in Zambian cattle, based on egg and worm counts. In the abattoir 315 cattle were screened for worms of F. gigantica in the liver, Schistosoma spp. in mesenteric veins and/or Amphistomum spp. in the rumen. One hundred and thirty-three (42.2%) of the abattoir-examined cattle harboured one, two or all three trematodes. Of 133 cattle, 50 were randomly selected for worm and egg counts. The mean numbers (+/- SD) of Amphistomum, Schistosoma and Fasciola were 622.08 (+/- 97.87), 33.68 (+/- 7.44) and 19.46 (+/- 4.58), respectively. A total of 32% harboured all the three trematodes, 66% had F. gigantica and Amphistomum spp. infections, 52% had Schistosoma spp. and Amphistomum spp. infections while 32% had F. gigantica and Schistosoma infections. A positive correlation (P = 0.014) was found between F. gigantica and Amphistomum worm burdens. There were no correlations between Amphistomum and Schistosoma worm burdens and between F. gigantica and Schistosoma worm burdens. It may be concluded that there is no significant cross-protection among these trematodes in cattle in endemic areas.     

Trematode infections in freshwater snails and cattle from the Kafue wetlands of Zambia during a period of highest cattle-water contact

A total of 984 snails, comprising nine species, were collected from six areas in the Kafue wetlands between August and October 2003 to assess larval trematode infections. Of these, 135 (13.7%) were positive. Most trematode infections were recorded from Lymnaea natalensis (42.8%), which harboured four of the five morphologically different cercariae found. No trematodes were recovered from Bellamya capillata, Biomphalaria pfeifferi, Melanoides tuberculata, Physa acuta and Cleopatra nswendweensis. One snail (0.2%) of 416 Bulinus snails shed brevifurcate-apharyngeate distome cercariae while three (0.7%) shed amphistomes. Gymnocephalous and longifurcate-pharyngeate distome were the commonest types of cercariae recorded while xiphidiocercaria was the least common. The highest prevalence rates of F. gigantica (68.8%) and amphistomes (50.0%) in cattle (n = 101) were in Chiyasa while those in Kaleya had the lowest (9.1 and 18.2%, respectively). In most habitats, infections were recorded in both cattle and snails. Critical determinants of infection may have been the distance of settlements and/or cattle kraals, the number of animals in nearby homesteads and the presence of susceptible host snails. This study suggests that fascioliasis and amphistomiasis could be major constraints of cattle production in the Kafue wetlands because favourable factors were available to introduce and maintain the infections. It further provides a starting point for some comprehensive studies on snail-related aspects of transmission and snail host ecology in Zambia.     

Ciliate protozoa in the rumen of Kafue lechwe, Kobus leche kafuensis, in Zambia, with the description of four new species.

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 x 10(4), and the number of ciliate species per head of host was 10.8.     

Abundance and distribution of elephants in the Luangwa Valley, Zambia

Elephant density over 40 000 km² of the Luangwa Valley was estimated as 2–17 km^-2 to give a population size of around 86 000 in that area, a tally that would probably top 100 000 if unsurveyed areas within the drainage had been included. Seasonal movement is largely restricted to a migration on to the riverine strip during the wet season and reciprocal dispersal across the valley thereafter. The mean annual range of movement is about 25 km.     

Kinda baboons (Papio kindae) and grayfoot chacma baboons (P. ursinus griseipes) hybridize in the Kafue river valley, Zambia

The ranges of small kinda (Papio kindae) and much larger grayfooted chacma (P. ursinus griseipes) baboons adjoin in the Kafue National Park, Zambia. In a visual survey of baboons at 48 sites in the Kafue River drainage we found that, contrary to previous reports, groups at the species interface near the town of Ngoma are phenotypically diverse and presumably formed by multigenerational hybridization. Mitochondrial and/or Y-chromosome genetic markers from fecal samples (N=164) collected at 29 sites support this conclusion. Groups with phenotypic signs of a history of hybridization also had taxon-specific mitochondria and Y-haplotypes from both parental species. Although the distribution of mitochondrial haplotypes largely mirrored that of external phenotypes, a significant proportion of male specimens from grayfoot as well as hybrid groups carried kinda Y-chromosomes, and kinda Y-chromosomes were involved in all observed cases of mitochondrial/Y-chromosome discordance. These observations are consistent with, though they do not prove, a population history in which the range of chacmas and the hybrid zone have advanced at the expense of the kinda range. They also suggest that, unexpectedly, kinda male×chacma female matings are much more common than the reciprocal cross in the ancestry of hybrids. We suggest that distinctive male kinda behavior and the "juvenile" appearance of kinda baboons of both sexes, perhaps combined with obstetric difficulties of a small kinda female carrying the large offspring of a chacma male, may account for this bias.     

Effect of ration size and feeding frequency on growth, size distribution and survival of juvenile clownfish, Amphiprion percula

This study describes the growth of juvenile clownfish, Amphiprion percula Lacépède 1802, fed with an artificial diet at six ration sizes of 2, 4, 6, 8, 10 and 12% of body mass per day (BM day^?1) each at a feeding frequency of once, twice and three times per day. The effect of ration size on growth depended on the feeding frequency. In fish fed once a day growth did not improve above a ration size of 8% BM day^?1. At two feedings per day fish required a ration size of at least 6% BM day^?1 to achieve good growth, and fish fed three times per day grew at similar rates above a ration size of 4% BM day^?1. A model to estimate the combined effect of ration size and feeding frequency is presented. The results lead to the suggestion of a simple length‐based feeding regimen that could be tested in future studies on this species or adapted for use in other species.     

Stability of the steady-state size distribution in a model of cell growth and division

The approach to steady-state size distribution is studied for a growing population of cells. The model incorporates cell growth at a linear rate and division into two equal daughters after a random time composed of an exponentially distributed phase and a constant deterministic phase.This work was supported by the National Science Foundation under Grant No. MCS 8300559This work was supported by the National Science Foundation under Grant No. MCS 8301104     

Cell cycle- and growth phase-dependent variations in size distribution, antibody productivity, and oxygen demand in hybridoma cultures

Simultaneous determination of cell size and DNA content of hybridomas (HB-32) revealed a direct correlation between average cell volume and progression through the cell cycle. Pseudocontinuous experiments showed that G(1) cells, as estimated from cell size measurements, secreted monoclonal antibody at rates higher than those of cells in other stages of interphase and mitosis. Similarly, fed-batch and batch experiments suggested that specific oxygen uptake rate (qO(2)) is also a function of cell cycle, being minimum for cells in G(0) and G(1) phase. In batch cultures, HB-32 showed a rapid decrease in oxygen uptake rate (OUR) just prior to reaching maximum cell concentration. The OUR steadily increased from 0.01-0.05 to 0.5-0.7 mmol O(2)/L h as the cells went from the lag to the midexponential phase. The qO(2) increased from 0.3 x 10(-10)-0.9 x 10(-10) mmol O(2)/cell h at inoculation to 3.3 x 10(-10)-3.7 x 10(-10) mmol O(2)/cell h during the early exponential phase where it remained relatively constant. Several hours before maximum cell concentration was reached, OUR and qO(2) rapidly decreased to levels below those observed at inoculation. The time at which the shift in OUR and qO(2) occurred and the onset of decrease in the average cell size corresponded to the time of glutamine depletion. Based on monitoring OUR on-line in batch cultures, glutamine was supplemented, resulting in increased cell concentration, extension of culture viability, and increased MAb concentration.     

A dynamical model for the growth and size distribution of multiple metastatic tumors

Metastasis is the spread of tumors culminating in the establishment of one or more secondary tumors at remote sites. In deciding the best treatment for cancer therapy, estimations of the colony size of metastatic tumors and predictions of the future spread of colonies are needed. A dynamical model for the colony size distribution of multiple metastatic tumors is presented here. The dynamics is described by equations that incorporate both the colonization by metastasis and the growth of each colony. When the colony growth is subject to the Gompertz function, the explicit solution obtained tends to an asymptotic stable distribution that shows a monotonically decreasing or U-shaped pattern according to the values of clinically significant parameters, such as the colonization coefficient and the fractal dimension of blood vessels. This predicted colony size distribution agrees well with successive data of a clinically observed size distribution of multiple metastatic tumors of liver cancer. The combined analysis of the theoretical colony size distribution and clinical data will give useful information on the diagnosis and the therapy for cancer patients.     

Isolation and characterization of symbiotes from the Rocky Mountain wood tick, Dermacentor andersoni

Wolbachia-like symbiotes in the Rocky Mountain wood tick, Dermacentor andersoni, were isolated repeatedly by injection of ovarial tissues into 5-day-old chick embryos. In Giemsa-stained smears of infected embryo tissues, the organisms appeared as blueish or pinkstained coccal bodies indistinguishable from those seen in the ovaries of ticks, where they are located in the luminal epithelium and funicle cells, as well as in oocytes.Electron microscopy revealed that these symbiotes are highly pleomorphic and vary in size from 0.6 to 3.4 μm in diameter. Their fine structure in tissue cells is differentiated into a granular, cortical region, which contains densely stained ribosomes, and a medullary region consisting of a diffuse reticulum partially or completely devoid of granular material or ribosomes. Multiplication is by binary fission. Each organism is delimited by a distinct plasmalemma; a cell wall as in bacterial and rickettsial agents was not observed in organisms from ovarial tissues.Symbiotes cultivated in chick embryos and then injected intracoelomically into adult D. andersoni, developed rapidly and produced massive infestations in hemocytes, hypodermal tissues, salivary glands, and in connective tissues surrounding midgut, Malpighian tubules, and ovary. In hypodermal tissue, organisms with a distinct bilayered cell envelope were occasionally detected. The massive invasion of tissues by injected symbiotes invariably proved fatal for ticks.Results of complement-fixation tests and of fluorescent antibody staining indicated that symbiotes in D. andersoni are closely related to Wolbachia persica, previously isolated from Argas arboreus.     

Changes in radial tree growth for Picea abies, Larix decidua, Pinus cembra and Pinus uncinata near the alpine timberline since 1750

Changes in radial growth of the four coniferous species growing in the French Alps near the upper treeline are investigated. Thirty-seven populations of Norway spruce [Picea abies (L.) Karst.], European larch (Larix decidua Mill.), Swiss stone pine (Pinus cembra L.) and mountain pine (Pinus uncinata Mill. ex Mirb.) were sampled by taking 1320 cores and analysing tree-ring widths. Sites were chosen in various climatic conditions (macroclimate and aspect) and on two kinds of bedrock in order to take into account the ecological behaviour of these species. Belledonne, Moyenne-Tarentaise, Haute-Maurienne and Briançonnais areas were sampled along increasing gradients of summer aridity and winter continentality. The calculation of time series after removing the age trend brings strong evidence for an increase in radial growth during the two last centuries, but with different stages and fluctuations for each species. This growth trend is significantly enhanced since 1860 for the spruce, and since 1920 for the two pine species. Furthermore, it also appears on Larix decidua with the same pattern despite periodical growth reduction due to attacks of the larch bud moth (Zeiraphera diniana Gn.). The analysis of ring-widths at a given cambial age reveals that this enhanced phenomenon is observed especially during the tree’s early years (25–75 years). The analysis of four regional climatic series, and three longer series of temperature (in farther single sites) reveals synchronous decadal fluctuations and an evident secular increase in minimum temperatures (especially in January and from July to October), that may be involved in tree-growth enhancement. Thermic amplitudes are significantly reduced during the whole growing period, what is more pronounced in Belledonne, the most oceanic region. Long term growth changes are well described by stepwise regression models, especially for the pine species. These models involved both a linear trend (CO₂ concentration or N-deposition) and low frequency of Turin monthly temperatures. However, they show different patterns than those observed from response functions at a yearly scale.     

Population growth of red lechwe, Kobus leche leche Gray, in the Busanga Plain, Zambia

An isolated population of red lechwe living in the Busanga Plain, Zambia, has been protected from human hunting since 1948. Probably as a result the population has increased, as indicated by reliable census data. From 1956 to 1972 this increase has very closely fitted an exponential rate; the calculated value of the infinitesimal rate of population increase (r) is 0–131, and the finite rate of increase is 14-0% per year. This exponential phase is considered to represent a segment of a logistic curve.     

A note on the distribution and abundance of puku, Kobus vardoni Livingstone, in Kasanka National Park, Zambia

This study (1994) examines the distribution and abundance of puku ( Kobus vardoni Livingstone) in Kasanka National Park (area=470 km²) Zambia, following five years of anti‐poaching control. The puku is an important 'flagship' species for the park. Most puku were confined to a limited number ( n =19) of river floodplains and dambos (total area=20·29 km²) towards the centre of the park. Large areas of 'suitable' habitat contained few, if any animals. The total population was estimated to be 613 (confidence limits=414–967) with an average density of 35·93 km⁻² on occupied sites. The population sex ratio was markedly biased towards females (mean=3·4 females to 1 male), but group sizes were similar to those recorded in other African studies. Male groups were on average (2·6), smaller than those of females (7·3). Males appeared to be particularly vulnerable to poaching. The distribution of puku reflected a patchy distribution of resources and a flexible social system. Puku numbers have increased two fold since the previous (1989) survey. Other species have faired less well. Further work is required to clarify dispersal mechanisms. Taylor's power law may provide a useful model for describing population dispersion. Kasanka is an important local refuge for this increasingly threatened species in Zambia. Metapopulation theory may be applicable to puku because of their ability to move between patches, during seasonal flooding.     

Changes in the distribution and size of synaptic vesicles in neuromuscular junctions of Locusta migratoria after stimulation and rest

Summary The distribution and size of synaptic vesicles in excitatory terminals of the extensor tibiae muscle were determined after stimulation at frequencies varying from 0.5 to 100 Hz and after a subsequent rest. Only in preparations stimulated at the higher frequencies do these parameters differ from those in the controls. The synaptic vesicles in the nonsynaptic areas of these terminals are depleted in number, and the remaining vesicles are reduced in size. These effects are reversed after a 1 h rest.The authors thank Mr. M.J. Parker for invaluable help with the statistical analyses. R.P. Botham thanks the S.R.C. for financial assistance