Chloroplast DNA and the determination of species status in the Disa tripetaloides complex (Orchidaceae), and its relationships to three species Racemosae, section Disa

Disa cardinalis and three populations within the D. tripetaloides species complex contain variation in their chloroplast DNA (cpDNA) variability. All four taxa possessed unique cpDNAs and sequence divergence values ranged from 0.34 to 1.03%. A phylogeny of these genomes was reconstructed, along with the genomes of three other species, D. racemosa, D. uniflora and D. venosa, all of which are also section Disa and series RAcemosae, to determine the relationship of these closely related species to the D. tripetaloides complex. A phylogeny of the taxa using morphological data was also reconstructed. Outgroup comparison was made with D. sagittalis, a member of section Coryphaea. Although the molecular and morphological data were not completely congruent, both data types revealed D. cardinalis, rather than D. tripetaloides ssp. aurata, to be more closely allied with D. tripetaloides ssp. tripetaloides, suggesting that D. tripetaloides ssp. aurata should be elevated to species rank. Additionally, the high sequence divergence observed between the Natal and Cape populations, coupled with their geographical isolation and alternate flowering seasons, suggests that these two D. tripetaloides ssp. tripetaloides populations may, in fact, be more appropriately ranked as subspecies.     

The sex-peptide gene (Acp70A) is duplicated in Drosophila subobscura

A 3.1-kb region of Drosophila subobscura homologous to the Acp70A region of D. melanogaster, which contains the sex-peptide gene, was cloned and sequenced. This region contains an approximately 600-bp duplication that includes the sex-peptide and its 5′ and 3′ flanking regions. The preproteins are 54 and 56 amino acids long, respectively (as compared to 55 amino acids in D. melanogaster), and each includes a 19-amino-acid-long signal peptide. The C-terminal part of the mature peptide is highly conserved between D. melanogaster and the two copies of D. subobscura. In this species, both copies of the gene are transcribed and, like in D. melanogaster, only expressed in males. The duplicated region includes 300 bp upstream of the gene that would therefore seem sufficient for their expression in males. This region presents at its 5′ end a stretch 93-bp that has a high similarity with the corresponding region of D. melanogaster and could be part of a still unidentified regulatory element of these genes.     

The tegument of the monogenean gill parasites Dactylogyrus amphibothrium and D. hemiamphibothrium

The general features of the tegument of Dactylogyrus amphibothrium and D. hemiamphibothrium, gill parasites of the freshwater fish Acerina cernua, resemble those of other monogeneans. However, in D. amphibothrium the tegument bears spike-like structures associated with tegumental sacs and these have not previously been reported in monogeneans. The origin of the sacs and the possible functions of the spikes and sacs are discussed. It has been found that the tegument covering the two pads located on the ventral surface of D. amphibothrium does not differ in structure from the general body tegument; the pad regions are elevated above the general body surface because of the presence of large glandular sub-tegumentary organs which communicate with the receptaculum seminis. This indicates that the pads play a part in the reproductive biology of the parasite. In spite of the fact that the micro-environments of D. amphibothrium and D. hemiamphibothrium are the same or broadly similar, D. hemiamphibothrium has no spikes, tegumentary sacs or glandular pads and has only two kinds of tegumentary secretory inclusion compared with three kinds in D. amphibothrium. One of the three kinds of cyton in D. amphibothrium is restricted to the ventro-lateral regions of the posterior half of the body. The tegument of both D. amphibothrium and D. hemiamphibothrium differs from that of other adult monogeneans so far investigated in the presence of granular endoplasmic reticulum in the outer syncytial layer.     

基于表型性状的金钗石斛种质资源多样性评价*

金钗石斛是我国重要的经济作物,具有药用和观赏价值。对收集的 17个居群的野生金钗石斛植株形态、花、气孔、有效成分含量等表型性状进行统计分析和多样性评价,并进行亲缘关系的系统聚类分析。结果表明,不同居群金钗石斛在表型性状上存在明显差异,种质资源具有丰富的遗传多样性;以变异系数较低的7个表型性状为参数进一步进行系统聚类分析,当欧式距离为10时,金钗石斛居群分成三组,其中海南白沙居群独立成一组,表明岛屿隔离阻碍了基因交流,对金钗石斛的生物多样性的贡献较大,因此岛屿为金钗石斛种质资源的就地保护和遗传资源有效维护提供了重要场所,为金钗石斛种质资源的保护和利用奠定了理论基础。     

Daphnia development and reproduction: Responses to temperature

1. 1.|The development times and reproduction were measured for Daphnia pulex and Daphnia magna from 5 to 30°C at 5°C increments.

2. 2.|The general trends for D. pulex and D. magna were for the duration of all juvenile instars to be less than that of adults and for the last juvenile (or adolescent) instar to be longer than all previous juvenile instars.

3. 3.|The number of juvenile instars both species pass through before adulthood is influenced by temperature with increasing numbers occurring at temperature extremes.

4. 4.|Duration of development time decreased over the entire range of increasing temperatures measured for D. pulex but increased for D. magna at 30°C in relation to 25°C.

5. 5.|Quadratic models were less desirable than simple linear logarithmic transformations of the form ln Y = ln a + b ln X for describing the temperature/development relationship.

6. 6.|The greatest young production occurs at 15 and 20°C with significant decreases occurring at temperatures above and below these.

7. 7.|The observed temperature-dependent phenomena an the ecological relationships for the two species are discussed.

Cytochrome b of the Dictyostelium discoideum plasma membrane

Cytochrome b of the plasma membrane of Dictyostelium discoideum was investigated in purified plasma membranes and in solubilized form. The membrane-bound cytochrome b can be reduced by NADH. This reduction is inhibited by p-hydroxymercuribenzoate. The reduced cytochrome b does not react with carbon monoxide. Its apparent molecular weight lies between 13000 and 16000. Tryptic digestion yields a large, heme-containing peptide with an apparent molecular weight between 12000 and 15000. After solubilization with cholate, cytochrome b can be enriched by reversed-phase HPLC, indicating that it contains also a hydrophobic component. With these properties, cytochrome b of the D. discoideum plasma membrane resembles microsomal cytochrome b₅.     

Algal colonization in urchin barrens: defense by association during recruitment of the brown alga Agarum cribrosum

We investigated the process whereby juveniles of the kelp Agarum cribrosum escape grazing by the green sea urchin, Strongylocentrotus droebachiensis, on urchin barrens in the rocky subtidal zone in the Mingan Islands, northern Gulf of St. Lawrence. The highest recruitment of juvenile A. cribrosum occurred under the canopy of the large filamentous phaeophyte Desmarestia viridis, where urchin densities were markedly reduced, compared to the surrounding area. This pattern of distribution appeared to be related to the wave-induced sweeping motion of D. viridis, although currents may modify the back and forth motion of the alga by pushing the canopy towards a specific direction, thereby allowing urchins to invade the non-swept areas. The density of juveniles under D. viridis plants increased with plant size and increasing proximity to the holdfast. Living under D. viridis slightly reduced the growth rate of the A. cribrosum juveniles, but this loss in growth was clearly outweighed by the gain in protection from sea urchin grazing. The time scale over which D. viridis provides protection is in the order of months, as D. viridis is an annual alga that disappears in early autumn. This defensive association of juvenile A. cribrosum with D. viridis is possibly a successional step leading to the formation of mature stands of A. cribrosum.     

温度对新菠萝灰粉蚧生长发育和繁殖的影响

新菠萝灰粉蚧是近年在我国新发现的一种重要外来入侵害虫,温度是决定新菠萝灰粉蚧能否建立稳定种群的最基本因素.本研究以南瓜作为寄主,探索恒温条件对新菠萝灰粉蚧生长发育和繁殖的影响.在17、20、23、26、29和32 ℃,光周期14L∶10D,相对湿度(75±5)%的实验室条件下,测定了新菠萝灰粉蚧各虫态的发育历期、发育速率、存活率和繁殖力,组建了新菠萝灰粉蚧的实验种群生命表.结果表明: 在20～29 ℃,各虫态的发育历期均随温度的升高而缩短,在20 ℃下雌、雄若虫期的发育历期最长,分别为46.95和50.26 d;29 ℃时雌虫若虫期的发育历期最短,为20.28 d;而雄虫若虫期在32 ℃时最短,为20.70 d.各虫态的温度与发育速率的关系均符合二次回归关系.此外,温度显著影响新菠萝灰粉蚧的存活率,在29 ℃时雌、雄若虫期的存活率均最高,分别为70.3%和69.3%;雌虫世代的发育起点温度为13.80 ℃,有效积温为491.50日·度;雄虫世代的发育起点温度为11.61 ℃,有效积温为388.85日·度.新菠萝灰粉蚧的产卵前期和成虫寿命随着温度的升高而缩短;成虫产卵量在29 ℃时最高,达每雌442.2粒;最小为20 ℃,仅为每雌111.8粒;29和20 ℃下种群趋势指数分别为168.2和19.1,且在17和32 ℃时,新菠萝灰粉蚧1龄若虫和3龄若虫均表现为生长停滞.说明温度过高或过低均不利于其生长发育.温度对新菠萝灰粉蚧的生长发育、存活、繁殖及种群增长有显著的影响,23～29 ℃是最适宜新菠萝灰粉蚧生长发育和繁殖的温度范围.     

Lack of effect of the nematophagous fungus Duddingtonia flagrans on the development of the dung beetle, Aphodius constans

The nematode-trapping fungus Duddingtonia flagrans may be used as a biological control agent of gastro-intestinal nematode larvae of ruminants by feeding the hosts with fungal spores. This trial was intended to search an eventual detrimental impact of the presence of spores of D. flagrans in high numbers in goat feces on the common dung beetle, Aphodius constans (Coleoptera: Aphodiidae). A. constans eggs were settled in feces derived from grazing goats fed spores at daily dose rates of 0, 0.25 × 10⁶, 0.5 × 10⁶ or 10⁶ spores/kg BW. At the end of the incubation period, the number of adults that have emerged from eggs were counted and compared between dose rates. No difference in emergence rate between treatments can be seen. The presence of D. flagrans spores in goat feces, even in large numbers, did not alter the development of A. constans.     

In vitro cultivation of Diplostomum spathaceum and Diplostomum phoxini metacercariae

Using a new egg macerate medium Diplostomum spathaceum metacercariae were cultured to the stage of egg production for the first time, and an improved vitelline and growth response was obtained in Diplostomum phoxini. The importance of physical factors in the cultivation of strigeoid trematodes was demonstrated. Methods involving a continuous circulating system, diphasic media, a double culture tube technique or the chorio-allantoic membrane proved to be of no value in the cultivation of Diplostomum spp. The addition of selected hormones with known growth promoting properties did not have an appreciable effect on D. phoxini cultures. Supplementation of egg macerate cultures with various nutrients had only slight or no beneficial effect. The ability to use stored metacercariae for cultures was demonstrated.     

A Dictyostelium discoideum DNA fragment complements a Saccharomyces cerevisiae ura3 mutant

Dictyostelium discoideum DNA fragments have been inserted into the chimeric bacterium-yeast plasmid YEp13. Recombinant plasmids were used to transform yeast using a strain of Saccharomyces cerevisiae deficient in OMP decarboxylase activity. Several clones were selected for growth in uracil-free medium. One clone was further analysed and contains a plasmid with a segment of D. discoideum DNA which complements a yeast ura3 mutation.     

Comparative aspects of the thermal biology of the short-tailed gerbil, Desmodillus auricularis, and the bushveld gerbil, Tatera leucogaster

1. 1. The response of oxygen consumption (VO₂), thermal conductance (C_d and C_min, body temperature (T_b), and evaporative water loss (EWL) of Tatera leucogaster and Desmodillus auricularis were measured over the range of ambient temperatures (T_a) from 5–35°C.

2. 2. Basal metabolic rate (BMR) of T. leucogaster was 0.841 ± 0.049 ml O₂ g⁻¹ h⁻¹ and lower than predicted, while that of D. auricularis was similar to the expected value (1.220 ± 0.058 ml O₂ g⁻¹ h⁻¹). D. auricularis had a high, narrow thermoneutral zone (TNZ) typical of nocturnal, xerophilic, burrowing rodents.

3. 3. D. auricularis and T. leucogaster regulated T_b over the range T_a = 5–35°C and kept EWL and dry thermal conductance at a minimum below the TNZ. However, the EWL of T. leucogaster increased rapidly above T_a = 30°C.

4. 4. After comparison with data from other species, it was concluded that there is an optimum size for xeric, nocturnal, burrowing rodents.

A Late Permian flora with Dicroidium from the Dead Sea region, Jordan

Three new species of Dicroidium, D. irnensis, D. jordanensis and D. robustum, are described from the Um Irna Formation (Upper Permian) of the Dead Sea region, Jordan. The plant remains are preserved as compressions with excellent cuticles. These are the earliest unequivocal records of Dicroidium, a genus that is typical for the Triassic of Gondwana. It is also the northernmost occurrence of this genus that apparently originated in the Permian in the palaeotropics. Middle and Late Permian floras from the Arabian Peninsula and adjacent regions show a remarkable mixture of elements from different floral provinces, i.e. Euramerica, Cathaysia and Gondwana. The climatic amelioration in the Early Triassic apparently enabled Dicroidium to migrate southward and eventually colonise the entire Gondwana region. Dicroidium is one of the very few megaplant genera not affected by the end-Permian biotic crisis, the largest Phanerozoic extinction event.     

A Drosophila minisatellite contains multiple Chi sequences

We demonstrate the existence of polymorphic DNA minisatellites in Drosophila mauritiana, a close relative of D. melanogaster. One of these sequences (minisatellite mD4.2) consists of 13 tandemly repeated monomers, 10 of which are 33 base pairs long. Each of the repeat monomers contains sequences identical or very similar to the Chi sequence (GCTGGTGG), a signal for recBCD-dependent recombination in Escherichia coli. Sequences hybridizing to the mD4.2 minisatellite are present in at least 20–25 genomic locations and exhibit substantial variability among different populations of three Drosophila species and two populations of the house fly, Musca domestica. Interpopulational variation is a result of length differences rather than restriction site polymorphisms and genetic crosses establish that the hybridizing restriction fragment patterns have an underlying genetic basis. The presence of these sequences in the genetically well known Drosophila species allows critical examination of processes that produce and maintain the remarkable variability associated with these genomic regions.     

Parvileguminophyllum coloradensis, a new combination for Mimosites coloradensis Knowlton, Green River Formation of Utah and Colorado

The purported ash samara, Fraxinus flexifolia (Lesquereux) Brown (1940) from the middle Eocene Green River Formation, is shown to be the same as small inequilateral legume leaflets identified as Mimosites coloradensis Knowlton. Because the name Mimosites Bowerbank is restricted to legume pods with mimosoid affinities, the new combination Parvileguminophyllum coloradensis (Knowlton) Call and Dilcher is proposed for the previously supposed samara, here recognized as a leaflet, and for leaflets currently placed in M. coloradensis. A lectotype is designated from among Knowlton's original specimens. The transfer of Brown's so-called Fraxinus samara to Parvileguminophyllum coloradensis (Knowlton) Call and Dilcher comb. nov. removes Fraxinus fruits from the list of macrofossil remains presently recognized in the Green River flora. The distribution of Fraxinus samaras in Paleogene assemblages from North America is briefly discussed. The paper concludes with a discussion of nomenclatural problems that may arise when two or more fossil organ types are united under a common name. We argue that this practice should be avoided except when the organs are found in organic connection, or when other indisputable evidence of their conspecificity is preserved, such as shared anatomical or biochemical features. By itself, the co-occurrence of disassociated fossil organs at different localities is only circumstantial evidence of their conspecificity.     

Characteristics of apolipophorin-III of the southwestern corn borer, Diatraea grandiosella

Apolipophorin-III was isolated from the lipophorin-free fraction of larval plasma of the southwestern corn borer, Diatraea grandiosella, because significant amounts of apolipophorin-III were found to be present in the hemolymph not associated with lipophorin. Apolipophorin-III, purified using ammonium sulfate precipitation, cation exchange chromatography, and gel filtration, was shown to be a nonglycosylated polypeptide with 17 kDa mol. wt, as determined by SDS-PAGE and silver staining. The amino acid composition of apolipophorin-III showed similarities to published compositions of apolipophorin-III isolated from other insects. The N-terminal sequence of apolipophorin-III (DAPSTTPPQDXEKKAAEFQKTFTEQXNQLANK), is highly homologous to that of apolipophorin-III of Manduca sexta. Antiserum raised against purified apolipophorin-III was used to demonstrate an immunochemical identity between the isolated apolipophorin-III and that associated with lipophorin. This antiserum cross-reacted with apolipophorin-III of M. sexta, and antiserum raised against M. sexta apolipophorin-III cross-reacted with apolipophorin-III isolated from D. grandiosella, demonstrating an immunochemical relationship between the proteins, and providing confirmatory evidence for the identity of the isolated protein. These antisera did not react with the putative apolipophorin-III of the cricket, Acheta domesticus. Using immunoprecipitation by the apolipophorin-III antiserum of D. grandiosella, the synthesis and secretion of [³H]apolipophorin-III by the fat body in vitro was shown to be maximal in 13–15 day-old larvae, with a transit time of ca 23 min.     

Chemical composition and in vitro fermentation of tannin-rich tree fruits

Dry and mature tree fruits are a potential source of protein for goats in the semi-arid areas of southern Africa, but their chemical composition and feeding value is largely unknown. This study presents the chemical composition and in vitro fermentation of indehiscent whole fruits and separated seed and hull fractions from Acacia nilotica, Acacia erubescens, Acacia sieberiana, Acacia erioloba, Piliostigma thonningii and Dichrostachys cinerea trees. Results indicate that the N contents of whole fruits ranged between 13.5 g/kg DM (A. nilotica) and 27.1 g/kg DM (A. erubescens). Seeds had a higher N content than hulls for all tree species. A. nilotica, D. cinerea and P. thonningii fruits had high levels of extractable phenolics (758, 458 and 299 g/kg DM, respectively). Soluble phenolics (SPh) and ytterbium precipitable phenolics (YbPh) levels were negatively correlated to in vitro gas production but positively correlated to in vitro organic matter degradability (iOMD). Partition factors for whole fruits at 48 h ranged between 3.6 mg/ml for A. erioloba and 7.8 mg/ml for A. nilotica. Seeds of A. erioloba, A. erubescens and P. thonningii were consistently fermented more efficiently throughout the incubation period compared to their whole fruits or hulls. Estimating in vitro degradability of phenolic-rich substrates through filtration procedures can give erroneous results due to the loss of soluble phenolics, which are not necessarily degradable. The feeding value of fruits from D. cinerea and A. nilotica tree species may be reduced due to the presence of high levels of phenolics.     

添加物及植物组合对瞿麦幼苗铅吸收、生长及品质的影响

通过盆栽试验研究了接种丛枝菌根真菌(AM真菌)、种植共生植物(三叶草)、添加重金属螯合物EDTA和磷肥磷酸钙对铅污染下瞿麦生长和品质的影响,为科学种植中药材提供理论依据.结果表明: 接种AM真菌可以显著抑制铅的吸收(P＜0.05),促进根部发育,使根冠比增大,且活性成分累积最多,大黄素含量为6.5 mg·g^-1;与三叶草共生后,抑制铅吸收的效果不佳且药材品质下降,大黄素含量低于对照组,降至3.2 mg·g^-1.但在AM真菌共同参与后瞿麦的生长量和活性成分有所增加,铅含量达到最低,低至1.3 mg·g^-1;添加重金属螯合剂会使瞿麦生长量下降并促进根部对铅的吸收,铅含量最高可达340.0 mg·g^-1;磷酸钙可固定土壤中其他重金属元素,故更适宜在复合型污染时使用.综合考虑,在保护中药材安全、品质方面AM真菌具有良好的应用价值.     

Temperature-mediated characteristics of the dusky salamander (Desmognathus fuscus) of southern Appalachia

Thermal preference of the salamander Desmognathus fuscus was measured in a linear thermal gradient with floor temperatures ranging from 10 to 30°C. Salamanders were acclimated to 21±1°C and a 12 : 12 photoperiod with photophase centered at 1200 h for 8 weeks prior to being placed in the gradient. Substrate temperatures were measured under the salamanders’ stomachs from 1200 to 2400 h at 2 h intervals immediately after feeding and after seven days fasting. We found no selection for temperature in fasting or postprandial D. fuscus. We compared the rate at which D. fuscus cooled and heated with that of a control and found no significant difference. We determined the desiccation rate of D. fuscus at 16 and 26°C and found a significantly more rapid desiccation at 26°C.