Seasonal variation of fatty acid content in natural microplankton from the Tumpat coastal waters of the South China Sea

In the search for better understanding on the nutritional quality of natural tropical plankton, samples were collected from shallow coastal waters facing the South China Sea during the dry monsoon (May-September) and the wet monsoon (November-April) seasons from March 1993 to July 1994. The total fatty acid content of the predominantly phytoplankton communities (25-200 microns sieve nets) varied four to fivefold with the lowest value occurring during the dry monsoon when blue-green became predominant. Saturated fatty acid content (SAFA), polyunsaturated fatty acid (PUFA) and total omega 3 (sigma omega 3) showed the same seasonal pattern as the total fatty acid with high values in October to December 1993. When species of the dinoflagellate Peridinium and Ceratium were present in considerable amount, the docosahexaenoic acid DHA content was high, especially from March to May 1993. The maximum content of eicosapentaenoic acid EPA, total omega-3 fatty acid, PUFA and sigma omega 3 in phytoplankton occurred during the pre-monsoon period (October and November 1993) when the diatoms were present in large amounts. The larger fraction sample (> 200 microns sieve nets) which consisted predominantly of zooplankton had high amounts of PUFA from September to November 1993.     

Methyl Jasmonate Increases the Tropane Alkaloid Scopolamine and Reduces Natural Herbivory in Brugmansia suaveolens: Is Scopolamine Responsible for Plant Resistance?

The tropane alkaloid (TA) scopolamine is suggested to protect Brugmansia suaveolens (Solanaceae) against herbivorous insects. To test this prediction in a natural environment, scopolamine was induced by methyl jasmonate (MJ) in potted plants which were left 10?days in the field. MJ-treated plants increased their scopolamine concentration in leaves and herbivory decreased. These findings suggest a cause?Ceffect relationship. However, experiments in laboratory showed that scopolamine affect differently the performance of the specialist larvae of the ithomiine butterfly Placidina euryanassa (C. Felder & R. Felder) and the generalist fall armyworm Spodoptera frugiperda (J. E. Smith): the specialist that sequester this TA from B. suaveolens leaves was not negatively affected, but the generalist was. Therefore, scopolamine probably acts only against insects that are not adapted to TAs. Other compounds that are MJ elicited may also play a role in plant resistance against herbivory by generalist and specialist insects, and deserve future investigations.     

Cyanotoxins in small artificial dams in Kenya utilised for cage fish farming – a threat to local people?

Nine small artificial dams located in different climatic regions of Kenya were studied. The local communities use the stored water for various purposes, such as irrigation, domestic use, watering of livestock and cage fish farming. Such intense use is commonly accompanied by eutrophication, including fast growth of cyanobacteria, which at times produce cyanotoxins threatening human and animal life. We studied the pelagic community, analysed abiotic variables and identified microcystins by means of high performance liquid chromatography and ELISA kits at monthly intervals over a period of one year. Mass spectrometry (MALDI-TOF MS) was used to identify structural variants of microcystins by their protonated masses (M + H). Three dams contained microcystins, with the highly toxic Microcystin-LR being identified as the most prominent substance. Cell content of the toxin varied from 7.2 to 686.7 fg cell^?1. Basic limnological variables that indicate the probability of toxin presence were also recorded. Non-parametric Mann–Whitney U-test revealed significant differences in soluble reactive phosphorous, nitrate-N, water depth, total hardness and post-Nauplii stages sampled between toxin-producing and non-toxin-producing dams. Although most of the samples did not contain high amounts of cyanobacteria, the cyanotoxin-problem was evident, suggesting the need for regular cyanotoxin monitoring programs.     

Aflatoxicosis in rabbits: Effectiveness of Egyptian raw bentonite in prevention or diminution the detrimental effects of naturally aflatoxin contaminated diets

Thirty five females and 15 males of New Zealand White mature rabbits about 6 months of age, were assigned to 1–5 dietary treatments (7 does+3 bucks for each): uncontaminated control diet, naturally aflatoxin contaminated diet without or with 1,2 and 3% bentonite. Rabbit fed with the aflatoxin-diet had a decreased (P<0.01 or 0.05) physical semen characteristics of bucks and a reproductive performance traits of does. The values of conception rate (%), gestation length (days), litter size (n) and litter weights (g) at birth and viability (%) of litters of doe rabbits, fed with the aflatoxin-diet, recorded, respectively: 64.5; 31.0; 4.4; 275.0 and 57.1 versus 85.6; 30.3; 7.9; 508.0; and 100 for those fed with the uncontaminated diet. Addition of bentonite to the aflatoxin contaminated diet improved in general the physical semen characteristics of buck and reproductive performance traits of doe rabbits. The results of the study demonstrate that adding 1% of Egyptian raw bentonite to the naturally aflatoxin contaminated rabbit diets can provide an effective, cheap and safe practical technique for preventing the aflatoxicosis in mature rabbits.     

Seasonal changes in composition and biomass of epiphytic algae on the macrophyte Ranunculus penicillatus in a chalk stream,with estimates of production,and observations on the epiphytes of Cladophora glomerata

The epiphytic algae on surfaces of the macrophyte Ranunculus penicillatus (Dumort.) Bab. var. calcareus (R. W. Butcher) C. D. K. Cook and on Cladophora glomerata (L.) Kütz growing in the River Itchen at Otterbourne near Southampton were studied between February 1984 and June 1985. The river at this site has a mean flow rate of 0.33 m s^–1, and is about 16 m wide and on average 20 cm deep, with a discharge ranging through the year between 0.34 and 2.46 m³ s^–1. The pH of the river varies little around 8.2, with a mean alkalinity of 236 mg HCO _inf3 ^sup1 l^–1, because of its origin from chalk springs. Ranunculus grows throughout the year, with peaks of biomass in spring and autumn. It forms a very large surface for attachment of epiphytes, and covers on average 40% of the stream bed. Numbers of epiphyte cells removed from Ranunculus ranged through the year between 52 × 10³ and 271 × 10³ cells mm^–2 stream floor, with maximum numbers in April, and a secondary peak in October. This pattern partly reflects fluctuations in the biomass of Ranunculus; the number of cells per unit area of plant surface showed a broader spring peak and lower fluctuations in other seasons. Diatoms formed 65 to 98% of these epiphyte cells, with chlorophytes reaching their peak (10%) in summer and cyanophytes (25%) in autumn. Estimates of biomass of these epiphytic forms, derived from measurements of chlorophyll c, indicate a range between 30 and 100 g dry weight m^–2 of weed bed. Colonisation studies showed that the algae grow and reproduce throughout the year, with a mean generation time of about 5 days, suggesting an annual production of about 3 kg dry weight m^–2 of weed bed, which makes epiphytic algae the principal primary producers in the stream. The numbers and biomass of epiphytic algae on Cladophora are considerably less.The species of epiphytic algae found on Ranunculus were generally similar to those growing on Cladophora, and to epilithic algae on pebbles of the stream bed, but different species were dominant on the different substrata. Algal cells in the water column were all derived from benthic habitats, although their relative abundance was very different.     

Homologies of the adductor mandibulae muscles in Tetraodontiformes as indicated by nerve branching patterns

Homologies of the adductor mandibulae muscles in eight families of Tetraodontiformes were hypothesized from the branching patterns of ramus mandibularis trigeminus. Insertions of the muscles to the upper or lower jaw were weak indicators of homology, migrations of the sites occurring frequently in A1, A2, A2, and A3. In monacanthids, tetraodontids, and diodontids, A1 tended to be split into numerous subsections, whereas in aracanids and ostraciids, A3 was highly developed, comprising three or four subsections. In tetraodontids, A2 was found to be a composite of A1 subsection and A2. The methods of and limits to applying nerve branching patterns to muscle homology are discussed. A new naming system that reflects both muscle homologies and insertions is proposed.     

Postsynaptic density antigens: preparation and characterization of an antiserum against postsynaptic densities

Long-term immunization of rabbits with postsynaptic densities (PSD) from bovine brain produced an antiserum specific for PSD as judged by binding to subcellular fractions and immunohistochemical location at the light and electron microscope levels. (a) The major antigens of bovine PSD preparations were three polypeptides of molecular weight 95,000 (PSD-95), 82,000 (PSD-82), and 72,000 (PSD-72), respectively. Antigen PSD-95, also present in mouse and rat PSDs was virtually absent from cytoplasm, myelin, mitochondria, and microsomes from rodent or bovine brain. Antigens PSD-82 and PSD-72 were present in all subcellular fractions from bovine brain, especially in mitochondria, but were almost absent from rodent brain. The antiserum also contained low-affinity antibodies against tubulin. (b)Immunohistochemical studies were performed in mouse and rat brain, where antigen PSD-95 accounted for 90 percent of the antiserum binding after adsorption with purified brain tubulin. At the light microscope level, antibody binding was observed only in those regions of the brain where synapses are known to be present. No reaction was observed in myelinated tracts, in the neuronal cytoplasm, or in nonneuronal cells. Strong reactivity was observed in the molecular layer of the dentate gyrus, stratum oriens and stratum radiatum of the hippocampus, and the molecular layer of the cerebellum. Experimental lesions, such as ablation of the rat entorhinal cortex or intraventricular injection of kainic acid, which led to a major loss of PSD in well- defined areas of the hippocampal formation, caused a correlative decrease in immunoreactivity in these areas. Abnormal patterns of immunohistochemical staining correlated with abnormal synaptic patterns in the cerebella of reeler and staggerer mouse mutants. (c) At the electron microscopic level, immunoreactivity was detectable only in PSD. The antibody did not bind to myelin, mitochondria or plasma membranes. (d) The results indicate that antigen PSD-95 is located predominantly or exclusively in PSD and can be used as a marker during subcellular fractionation. Other potential uses include the study of synaptogenesis, and the detection of changes in synapse number after experimental perturbations of the nervous system.     

Seasonal changes in composition and biomass of epilithic algal floras of a chalk stream and a soft water stream with estimates of production

Microscopic epilithic algae in the River Itchen at Otterbourne near Southampton and in the Ober Water in the New Forest were studied during 1984 and 1985. The River Itchen rises from chalk springs and has a steady pH near 8.2 and a mean alkalinity of 236 mg HCO₃ 1^–1; at the study site the river is about 16 m wide and 20 cm deep, with a mean flow rate of 0.33 m s^–1 and a discharge ranging through the year between 0.34 and 2.46 m³ s^–1. The Ober Water, which drains sands and gravels, has a pH between 6.9 and 7.2 and a mean alkalinity of about 50 mg HCO₃ 1^–1; at the study site it is about 6 m wide, with a mean flow rate of 0.27 m s^–1 and a discharge ranging through the year between 0.08 and 1.0 m³ s^–1.Epilithic algae removed from the pebbles that form the major part of the beds of both streams show seasonal changes in abundance and composition. Diatoms peaked in April/May and dominate the epilithic flora in both streams, comprising 70–95% of all algal cells; highest numbers of chlorophytes occurred in summer and cyanophytes increased in autumn. The species composition of the epilithic flora in the two streams was different, as was the population density; algal cell numbers ranged between 500 and 7000 cells mm^–2 of stream floor in the River Itchen and between 8 and 320 cells mm^–2 of stream floor in the Ober Water. The chlorophyll a content of epilithic algae in the River Itchen ranged between 115 and 415 mg m^–2 of stream floor, representing an annual mean biomass of about 8 g m^–2, whereas in the Ober Water a chlorophyll a content of 2.2 to 44 mg m^–2 of stream floor was found, representing an annual mean biomass of about 1 g m^–2. Cautious estimates of the annual production of epilithic algae in these streams suggest a value of about 600 g organic dry weight m^–2 in the River Itchen and about 75 g m^–2 in the Ober Water.