REVERSED VERTICAL MIGRATION OF PLANKTONIC CRUSTACEANS IN A EUTROPHIC LAKE OF HIGH pH

SUMMARY

Two studies of the diel vertical migration of zooplankton in the hyper-eutrophic Hartbeespoort Dam, revealed that both in summer when the lake was anaerobic below 15 m depth, and in winter, when homogeneous, aerobic conditions existed throughout the water column, a major portion of the zooplankton standing crop displayed a reversed migration tendency. The clado-cerans Daphnia pulex and D. longispina, and the copepod Thermo-cyclops oblongatus were the species involved. There was no evidence to sugest that interspecific interference, a phenomenon recently found to have caused reversed vertical migration in the rotifer Asplanchna priodonta, was responsible for the unusual movements recorded in the present study, since the species concerned were by far the total biomass and size dominants of the population.     

THE EFFECT OF AGITATION AND TURBULENCE OF THE GROWTH MEDIUM ON THE GROWTH AND VIABILITY OF MICROCYSTIS

SUMMARY

Observation of natural blooms of Microcystis, suggested that increased turbulence plays a role in retarding bloom formation of Microcystis. In laboratory experiments the influence of turbulence mediated by a magnetic stirrer on the growth and viability of Microcystis in batch cultures was determined. The different turbulences (0, 25, 75, 126, 209 and 314 cm sec^?1 linear velocity) had no effect on the growth rate. There was a highly significant correlation between the linear velocity and percentage viability as determined by a plating and serial dilution method. The viability ranged from 0,8% for stationary cultures to 99,2% for vigorously stirred (314 cm sec^?1 linear velocity) cultures.     

POPULATION STRUCTURE OF TWO LABEO SPECIES IN THE HENDRIK VERWOERD DAM AS DETERMINED BY GILL NET SAMPLING

SUMMARY

A series of seven gill nets was used to sample populations of two Labeo species in the Hendrik Verwoerd Dam. Selection curves were computed for these nets and were used to define size and age structure of the two populations; these populations differ markedly, in that the moggel Labeo umbratus has a greater proportion of mature fish, while Labeo capensis (the Orange River Labeo) showed a more normal size and age distribution. Bio-mass curves closely follow the size distribution, while the fecundity of both species is highest in the larger size groups. These data were used to speculate on a fish exploitation strategy for the dam.     

ON THE STATUS OF CLARIAS GARIEPINUS (BURCHELL) IN LARGE MAN-MADE LAKES IN RHODESIA

SUMMARY

Data from some large man-made lakes in Rhodesia suggest that the populations of Clarias gariepinus have declined in these lakes. The reasons for this are not clear although commercial fishing does not appear to be responsible.     

TAXONOMIC BIBLIOGRAPHY OF VASCULAR AQUATIC PLANTS IN SOUTHERN AFRICA

SUMMARY

The length mass relationship for a Labeo capensis population is described by the equation M = 0,0134 L^2'999 where 2,999 represents a constant the value of which indicates isometric growth. There is very little difference between the length/mass relationship for males and that for females and this is similar to the results found by Mulder (1973) for L. capensis in the Vaal River. The length/mass relationships for gravid males and females are different from that of the population as a whole indicating that maturity does result in a change of the body form which is in accordance with the results of Mulder (1973).

A modified formula to take into account, small length intervals of an age group, is used to calculate the relative condition factor for Labeo capensis from the Caledon River for a consecutive “winter” and “summer” period. The results show that the conhd1t10ni for Labeo capensis of the 0⁺, 1⁺ and 2⁺ age groups is better in the summer period than in the winter period, whereas in the older age groups 3⁺ to 5⁺ the condition in winter is better than in summer. This can be attributed to the attainment of sexual maturity at the age of 3⁺ years and the presence of large quantities of fat deposited in the body during the winter months, which are then utilised for the development of the gonads prior to spawning. These results are similar to those obtained for the same species by Mulder (1973) in the Vaal River and by Bloemhof (1974) in the Hardap Dam.     

OBSERVATIONS ON THE THREE ALLOPATRIC POPULATIONS OF THE MALUTI MINNOW,OREODAIMON QUATHLAMBAE (BARNARD) WITH NOTES ON ITS EVOLUTION,ECOLOGY, SPAWNING,AND CONSERVATION

SUMMARY

Meristics and pigmentation of specimens of Oreodaimon quathlambae from the three known populations were compared to determine whether the species has experienced divergent evolution. Pigmentation was found to vary substantially but meristics counts did not. A proposal is made-to recognise three varieties of the species: Tsoelika-na, Senqu, and Moremoholo.

A review of the possible evolution of the species and the Drakensberg ecosystem suggests that the decline of the minnow is due to its exclusive adaption to a disappearing habitat.

Examination of what is known of the fish's life history and the history of the host rivers implies that competition from trout is a secondary cause of extermination of the endangered minnow. Environmental degradation poses a greater threat to the survival of the species.

Speculation is offered that O. quathlambae is a crevice spawner.

A report on the current conservation status and research is given along with management recommendations. Recent surveys have discovered another isolated population on the Tsoelikana River.     

BATHYMETRIC STUDIES ON THE PONGOLO RIVER FLOODPLAIN

SUMMARY

Thirteen of the major pans on the Pongolo river floodplain have been studied. Most are shallow (>2.5 m) and regularly lose up to 70% of their water each year, although few dry out. Floods inundate considerable areas (1000 ha) around pans situated in the flatter parts of the floodplain. Whilst inundated, these areas provide an allochthonous energy and nutrient source for the pan and, as the water levels recede, the exposed Cynodon dactylon (L.) Pers lawns provide grazing for cattle. The suitability of the various pans for fish production is discussed.     

Improved and Reliable Synthesis of 3′‐Azido‐2′,3′‐dideoxyguanosine Derivatives

An improved synthesis of N²‐protected‐3′‐azido‐2′,3′‐dideoxyguanosine 20 and 23 is described. Deoxygenation of 2′‐O‐alkyl (and/or aryl) sulfonyl‐5′‐dimethoxytritylguanosine coupled with [1,2]‐hydride shift rearrangement gave protected 9‐(2‐deoxy‐threo‐pentofuranosyl)guanines ( 10 , 12 and 16 ). This rearrangement was accomplished in high yield with a high degree of stereoselectivity using lithium triisobutylborohydride (l‐Selectride®). Compounds 10 , 12 and 16 were transformed into 3′‐O‐mesylates ( 18 and 21 ), which can be used for 3′‐substitution. The 3′‐azido nucleosides were obtained by treatment of 18 and 21 with lithium azide. This procedure is reproducible with a good overall yield.     

Antisense Knockdown of PKC-α Using LNA-Oligos

Abstract

Full-length and 4 nucleotides truncated Locked Nucleic Acid (LNA) modifications of ISIS 3521 were compared for antisense properties in a cellular assay. ISIS 3521 is a 20-mer phosphorothioate designed to hybridise to human protein kinase C-α (PKC-α) mRNA and is currently submitted to clinical trials against cancer. We report that LNA can potentate this antisense oligo and retain the antisense potential with shorter oligos.     

PRELIMINARY RESULTS ON THE UPTAKE AND RELEASE OF 32P BY POTAMOGETON PECTINATUS

SUMMARY

The absorption and release of ³²PO₄, by Potamogeton pectinatus L during winter was investigated using a partitioned container in which the roots were separated from the stems and leaves. ³²PO₄ is absorbed by the roots as well as the stems and leaves under both light and dark conditions and transported to all parts of the plant. Transport rates (μg P plant^?1 24 hr^?1) show that more phosphorus is released by the roots than by the stems and leaves, indicating a nett movement of phosphorus from the surrounding water to the substrate. Foliar absorption of ³²P exceeds root absorption under both light and dark conditions.     

THE HABITATS AND HABITAT PREFERENCES OF CLARIAS GARIEPINUS (PISCES: CLARIIDAE) IN A CLEAR COASTAL LAKE (LAKE SIBAYA,SOUTH AFRICA)

SUMMARY

The habitat preferences of the sharptooth catfish, Clarias gariepinus, in a clear coastal lake, Lake Sibaya, are described. Larval and small juvenile catfish inhabit flotsam and the rootstocks of plants in very shallow marginal areas. Larger juveniles inhabit densely-vegetated marginal pools, and may venture into open areas at night. Adult catfish (over 350 mm TL) occupy offshore areas, where their density is highest in terrace and sheltered bay habitats, and least in slope and profundal habitats. Adult catfish undergo a diel migration into shallow water at night and into deeper water during the day which is more marked at low lake levels. The methods used to capture catfish, and the main habitats in Lake Sibaya, are also described.     

BOOK REVIEWS

SUMMARY

Scale studies indicated that the annulus is a reliable year mark. A linear relationship existed between scale radius and body growth enabling back calculations to be made. The growth rate of males in Doorndraai Dam were similar to findings in the Incomati and Limpopo systems by Gaigher 1969 and Potgieter 1974 for the same species. The average sex ratio was one male to 1,8 females and was similar to that of the above river systems. Males reached sexual maturity at 12 cm while females matured at a length of 15 cm. The spawning season extended from late September to after December. Fecundity increased with an increase in length from 3 600 ova for a 15,4 cm fish to 8 500 for a 30,9 cm fish. T. rendalli fed extensively on macro-phytic vegetation when it was available, otherwise they became facultative feeders.     

Tourist impact on Tibetan macaques

Abstract

Ecotourism is a growing sector of the tourism industry, but few studies to date have quantified its impacts on local people, tourists and wildlife. We present a preliminary study on threat and affiliative behaviors of two groups of free-ranging Tibetan macaques (Macaca thibetana) as a function of habituation and tourist presence. Data indicate that the less habituated group spent less time within sight of tourists compared with the more habituated group. The more habituated group engaged in frequent affiliative behaviors while within sight of humans, whereas affiliative behavior was not observed in the less habituated group. The general pattern of threats consisted of adults primarily threatening juveniles and juveniles primarily threatening humans, possibly due to redirection. No clear pattern of threats as a function of tourist density emerged. Tourist feeding, although discouraged, potentially provided a catalyst for some aggression. Future research will focus on clarifying which human behaviors evoke specific threat responses from monkeys. These data will be used to refine the existing management plan for this monkey population.     

A New Synthesis of 7-Methyl-8-Oxoguanosine

Abstract

A new, facile synthesis of 7-methyl-8-oxoguanosine is reported. 2-Chloro-7-methylpurine-6, 8-dione (5) was silylated with hexamethyldi-silazane and the silylated intermediate, 6, glycosylated with 1-0-acetyl-2, 3, 5-tri-0-benzoyl-D-ribofuranose to yield 2-chloro-7-methyl-9-(2′, 3′,-5′-tri-0-benzoyl-β-D-ribofuranosyl) purin-6, 8-dione (8). Deprotection of 8 with sodium hydroxide in aqueous methanol gave 2-chloro-7-methyl-9-(β-D-ribofuranosyl) purine-6,8-dione (9), which was aminated with liquid ammonia or methanolic ammonia to yield 7-methyl-8-oxoguanosine (3).     

Synthesis of Brunfelsamidine Ribonucleoside and Certain Related Compounds by the Stereospecific Sodium Salt Glycosylation Procedure

Abstract

A synthesis of 2,4-dideazaribavirin ( 2 ), brunfelsamidine ribonucleoside ( 8c ) and certain related derivatives are described for the first time using the stereospecific sodium salt glycosylation procedure. Glycosylation of the sodium salt of pyrrole-3-carbonitrile ( 4 ) with 1-chloro-2, 3-O-t-isopropylidene-5-O-t-butyldimethylsilyl-α-D-ribofuranose ( 5 ) gave exclusively the corresponding blocked nucleoside ( 6 ) with β-anomeric configuration, which on deprotection provided 1-β-D-ribofuranosylpyrrole-3-carbonitrile ( 7 ). Functional group tranformation of 7 gave 2 , 8c and related 3-substituted pyrrole ribonucleosides. These compounds are devoid of any significant antiviral/antitumor activity invitro.     

5′-O-[N-(Amnoacyl)Sulfamoyl]Nucleosides. Synthesis and Antiviral and Cytostatic Activities

Abstract

5′-O-[N-(Aminoacyl)sulfamoyl]-uridines and -thymidines 4a-12a and 4b-12b have been synthesized and tested against Herpes Simplex virus type 2 (HSV-2) and as cytostatics. Condensation of 2′,3′-O-isopropylidene-5′-O-sulfamoyluridine and 3′-O-acetyl-5′-O-sulfamoylthymidine with the N-hydroxysuccinimide esters of Boc-L-Ser(Bzl), (2R, 3S)-3-benzyloxycarbonylamino-2-hydroxy-4-phenylbuta-noic acid [(2R, 3S-N-Z-AHPBA], (2R, 3S) and (2S, 3R)-N-Boc-AHPBA gave 4a,b-7a,b, which after removal of the protecting groups provided 1Oa,b-12a,b. A study of the selective removal of the O-Bzl protecting group from the L-Ser derivatives 4a,b, without hydrogenation of the pyrimidine ring, has been carried out. Only the fully protected uridine derivatives 4a-7a did exhibit high anti-HSV-2 activity, and none of the synthesized compounds showed significant cytostatic activity against HeLa cells cultures.     

Conformational Analysis of 6-Substituted Uridine Analogues: Crystal Structures of Uridine-6-Thiocarboxamide and 6-Cyanouridine

Abstract

Crystal structure analyses of uridine-6-thiocarboxamide (I) and 6-cyanouridine (II) show that both structures adopt a syn conformation about the glycosyl bond. The conformation of I is similar to that of orotidine (III). The furanose ring conformation of I is C4′-exo, unusual for syn conformers, and is C3′-endo in II. These results have a bearing on the inhibition of orotidylate decarboxylase by the 5′-phosphate of I.     

Some factors influencing adoption of sheltered dogs

Abstract

In Italy the law forbids euthanizing shelter dogs unless they are severely ill or dangerous. This has created a problem: many dogs are housed for long periods of time in shelters. It is important to the welfare of these dogs for us to find methods to increase successful adoption rates. The aim of this study was to evaluate the effect of different management factors such as the number of dogs in a pen, Temporary Adoption Programs (TAPs), and animal-owner-related characteristics on successful adoptions of kenneled dogs. The study included 763 dogs, 92 of whom were dogs showing behavioral problems. The age of the dogs upon arrival at the shelter was the most important determinant for length of stay, with younger dogs being adopted faster (Kruskal-Wallis, H = 150.27; df = 3; n = 733; p < 0.001). Dogs up to six months of age (n = 73) were adopted more quickly than older dogs (average length of stay: 1.4 vs. 6.4 months). The year of admittance was also significant since dogs who were admitted in a year in which more dogs were brought to the shelter spent more time in the shelter before being re-homed (Kruskal-Wallis, H = 96.18; df = 2; n = 733; p < 0.001). Dogs' gender had no effect on length of stay (Mann-Whitney, U = 64563; Z = 0.81; p = ns; n¹ = 389; n² = 344). Temporary Adoption Programs had a significant positive effect in reducing the return rate when the final adopter was the same person who had “temporarily” adopted the dog (Fisher exact test, p = 0.0063). Return rate was also associated with behavioral problems. Fearful dogs were returned more often than dogs with other problems (Fisher exact test, p = 0.029). It is concluded that, although young age is the most important factor leading to quick adoption, programs which include increased human interaction, and special training for dogs with behavioral problems, could aid in the successful re-homing of shelter dogs.     

Production of nematocidal compounds by hairy root cultures of Tagetes patula L.

Summary Marigold (Tagetes patula L.) hairy roots induced by infection with Agrobacterium rhizogenes produced -terthienyl when grown in darkness, and an n-hexane extract of the roots showed nematocidal activity. Depending on the hairy root line used, the level of -terthienyl varied from 15 to 1268 g per g dry weight, a level that corresponded to 0.15 to 12.7-fold that in intact roots. Analysis by HPLC indicated that the nematocidal activity was due predominantly to -terthienyl. However, it is suggested that nematocidal compounds other than -terthienyl are present in hairy roots cultured in the dark for long periods or in the light.