Life history and laboratory host range of Stenopelmus rufinasus, a natural enemy for Azolla filiculoides in South Africa

The frond-feeding weevil, Stenopelmus rufinasus Gyllenhal, was imported into quarantine for testing as a potential natural enemy for the invasive fern Azolla filiculoides Lamarck in South Africa. Adult S. rufinasus lived for approximately 55 days during which the females produced on average 325 offspring. The developmental period for the immature stages (egg, three larval instars and pupation) was about 20 days indicating the potential for several overlapping generations per year. Both the adults and the larvae caused severe damage to A. filiculoides in the laboratory. Host specificity of this insect was determined by adult no-choice oviposition and larval starvation tests on 31 plant species in 19 families. Adult feeding, oviposition and larval development was only recorded on the Azolla species tested (A. filiculoides, A. pinnata subsp. poss. asiatica R.K.M. Saunders and K. Fowler, A. pinnata subsp. africana (Desv.) R.K.M. Saunders and K. Fowler and A. nilotica De Caisne Ex Mett.). A. filiculoides proved to be significantly the most suitable host for the weevil. The low adult emergence from A. nilotica and A. pinnata subsp. africana would most probably prevent the weevil from establishing on them in the field. A. pinnata subsp. poss. asiatica which supported greater development, is thought to be introduced and has a weedy phenology in South Africa and is thus of low conservation value. Therefore, any damage inflicted on this plant in the field may be an acceptable trade-off for the predicted impact of S. rufinasus on the aggressive exotic weed, A. filiculoides.     

Response of growth and antioxidant enzymes in Azolla plants (Azolla pinnata and Azolla filiculoides) exposed to UV-B

Effect of ultravilolet-B (0.4 Wm(-2)) irradiation on growth, flavonoid content, lipid peroxidation, proline accumulation and activities of superoxide dismutase and peroxidase was comparatively analysed in Azolla pinnata and Azolla filiculoides. Growth measured as increment in dry weight reduced considerably due to all UV-B treatments. However, the reduction was found to be severe in A. filiculoides as compared to A. pinnata. The level of UV-absorbing compound flavonoids increased significantly in A. pinnata plants whereas only a slight increase in the flavonoid content was observed in A. filiculoides. UV-B exposure led to enhanced production of malondialdehyde (MDA) and electrolyte leakage in A. filiculoides than A. pinnata. Proline accumulation also showed a similar trend. Marked differences in the activity of antioxidant enzymes such as superoxide dismutase (SOD) and peroxidase (POD) was noticed in both the plants exposed to UV-B. Our comparative studies indicate A. pinnata to be better tolerant to UV-B as compared with A. filiculoides which appears to be sensitive.     

Genetic diversity among and within cultured cyanobionts of diverse species of <Emphasis Type="Italic">Azolla</Emphasis>

The cyanobionts isolated from 10 Azolla accessions belonging to 6 species (Azolla mexicana, A. microphylla, A. rubra, A. caroliniana, A. filiculoides, A. pinnata) were cultured under laboratory conditions and analyzed on the basis of whole cell protein profiles and molecular marker dataset generated using repeat sequence primers (STRR(mod) and HipTG). The biochemical and molecular marker profiles of the cyanobionts were compared with those of the free-living cyanobacteria and symbiotic Nostoc strains from Anthoceros sp., Cycas sp. and Gunnera monoika. Cluster analysis revealed the genetic diversity among the selected strains, and identified 3 distinct clusters. Group 1 included cyanobionts from all the 10 accessions of Azolla, group 2 comprised all the symbiotic Nostoc strains, while group 3 included the free-living cyanobacteria belonging to the genera Nostoc and Anabaena. The interrelationships among the Azolla cyanobionts were further revealed by principal component analysis. Cyanobionts from A. caroliniana-A. microphylla grouped together while cyanobionts associated with A. mexicana-A. filiculoides along with A. pinnata formed another group. A. rubra cyanobionts had intermediate relationship with both the subgroups. This is the first study analyzing the diversity existing among the cultured cyanobionts of diverse Azolla species through the use of biochemical and molecular profiles and also the genetic distinctness of these free-living cyanobionts as compared to cyanobacterial strains of the genera Anabaena and Nostoc.     

Identification of a common cyanobacterial symbiont associated with Azolla spp. through molecular and morphological characterization of free-living and symbiotic cyanobacteria.

Symbiotically associated cyanobacteria from Azolla mexicana and Azolla pinnata were isolated and cultured in a free-living state. Morphological analyses revealed differences between the free-living isolates and their symbiotic counterparts, as did restriction fragment length polymorphism (RFLP) analyses with both single-copy glnA and rbcS gene probes and a multicopy psbA gene probe. RFLP analyses with Anabaena sp. strain PCC 7120 nifD excision element probes, including an xisA gene probe, detected homologous sequences in DNA extracted from the free-living isolates. Sequences homologous to these probes were not detected in DNA from the symbiotically associated cyanobacteria. These analyses indicated that the isolates were not identical to the major cyanobacterial symbiont species residing in leaf cavities of Azolla spp. Nevertheless, striking similarities between several free-living isolates were observed. In every instance, the isolate from A. pinnata displayed banding patterns virtually identical to those of free-living cultures previously isolated from Azolla caroliniana and Azolla filiculoides. These results suggest the ubiquitous presence of a culturable minor cyanobacterial symbiont in at least three species of Azolla.     

Identification of a common cyanobacterial symbiont associated with Azolla spp. through molecular and morphological characterization of free-living and symbiotic cyanobacteria.

Symbiotically associated cyanobacteria from Azolla mexicana and Azolla pinnata were isolated and cultured in a free-living state. Morphological analyses revealed differences between the free-living isolates and their symbiotic counterparts, as did restriction fragment length polymorphism (RFLP) analyses with both single-copy glnA and rbcS gene probes and a multicopy psbA gene probe. RFLP analyses with Anabaena sp. strain PCC 7120 nifD excision element probes, including an xisA gene probe, detected homologous sequences in DNA extracted from the free-living isolates. Sequences homologous to these probes were not detected in DNA from the symbiotically associated cyanobacteria. These analyses indicated that the isolates were not identical to the major cyanobacterial symbiont species residing in leaf cavities of Azolla spp. Nevertheless, striking similarities between several free-living isolates were observed. In every instance, the isolate from A. pinnata displayed banding patterns virtually identical to those of free-living cultures previously isolated from Azolla caroliniana and Azolla filiculoides. These results suggest the ubiquitous presence of a culturable minor cyanobacterial symbiont in at least three species of Azolla.     

Indole-3-acetic acid (IAA) production by Arthrobacter species isolated from Azolla.

Arthrobacter species, isolated from the leaf cavities and the microsporocarps of the aquatic fern species Azolla pinnata and Azolla filiculoides, produced indole-3-acetic acid (IAA) in culture when the precursor tryptophan was added to the medium. No IAA production was detected in the absence of tryptophan. Maximum IAA formation was obtained in the first 2 d of incubation. Part of the tryptophan was transformed to N alpha-acetyl-L-tryptophan.     

Scanning Electron Microscopic Observation of Symbiotic Relationship of Azolla-Anabaena AzoUae During the Vegetative Growth

The occurrence and development of the hair ceils on the shoot tips and in the leaf cavities of A. filiculoides, A. microphylla, A. pinnata and their algae-free cultures were examined by means of scanning electron microscopy with microdissect technique. The patterns of Anabacna moving into the leave cavities from the shoot tips were investigated on three species of Azolla during their vegetative growth. The results showed that the patterns of symbiotic Anabaena infecting the leaf cavities are similarity among three species of Azolla and may be divided to the four phases which are summarized as follows: 1. occurrence of primary branched hair and adhesion of Anabaena; 2. development of primary branched hair and spreding of Anabaena; 3. building of hair bridge and entrance of Anabaena into the cavities; 4. formation of secondary simple hair and transference of Anabaena within the cavity. These observations resulted in a hypothesis that hair induces and leads its partner. It is suggested that the hair cell is likely to be a structure of Azolla for attracting and recognizing its symbiont in addition to transport substance between fern and algae.     

Synergistic effect of deoxyanthocyanins from symbiotic fern Azolla spp. on hrmA gene induction in the cyanobacterium Nostoc punctiforme

The hrmA gene of the N2-fixing cyanobacterium Nostoc punctiforme functions in repressing the formation of transitory motile filaments, termed hormogonia, by plant-associated vegetative filaments. Here, we report that anthocyanins can contribute to induction of hrmA expression. Aqueous extract from fronds of the fern Azolla pinnata, a host of symbiotic Nostoc spp., was found to be a potent inducer of hrmA-luxAB in N. punctiforme strain UCD 328. The hrmA-luxAB inducing activities of A. pinnata, as well as Azolla filiculoides, were positively correlated with levels of frond deoxyanthocyanins. Analyses of the deoxyanthocyanins in frond extracts revealed, in order of predominance, an acetylated glycoside derivative of luteolinidin (m/z 475) and of apigeninidin (m/z 459) and minor amounts of a second luteolinidin derivative. At up to 150 microM, a purified preparation of deoxyanthocyanins only weakly induced hrmA-luxAB on its own, but mixtures with hrmA-luxAB inducers (A. filiculoides extract or the flavonoid naringin) synergistically doubled to tripled their inducing activities. These results suggest that appropriately localized deoxyanthocyanins could function in plant-mediated mechanisms for repressing Nostoc spp. hormogonium formation.     

Studies on the Microstructure and Ultrastructure of Photosynthetic Apparatuses in Azolla

The structures of photosynthetic apparatuses such as leaves, chloroplasts and symbiotic cyanobacterum (blue-green algae) in Azolla-Anabaena azollae associations (Azolla imbricata (Roxb) Nakai) which occur in paddy fields of China were examined using light, scanning and transmission electrn microscopy. Some comparisons were made with A. filiculoides, A. japonica, A. caroliniana, A. pinnata and A. mexicana. Cross sections of A. imbricata were observed by light microscopy and the symbiotic association between the eukaryotic water fern and its prokaryotic blue-green algal symbiont, an Anabaena, was studied. The symbiotic cyanobacterum cells occur not only in a mature leaf cavity, but also in early stages of leaf development, around leaf primordia, and even in macrospores. Under scanning electron microscopy (SEM) it is possible to see stomata and nipples on the surface of dorsal lobes of the fern. The species in the subgenus Euazolla (i.e.A. filiculoides, A. japonica, A. caroliniana and A. mexicana) have rounded nipples, but those in the subgenus Rizosperma (i.e.A. imbricata and A. pinnta) prolate ones. This morphological character is first reported to be related to the taxonomic system. The result of the observation with transmission electron microscopy (TEM) shows that A. filiculoides contains more thylakoides in chloroplasts than A. imbricata does, and the grana lamellae have more stacks in the former than in the latter. The differences are in agreement with the differentiation of the two species in photosynthetic capacity. This may be one of the differences between the two subgenera. The ultrastructures of the symbiotic cyanobacterum are similar to those of free-living Anabaena. The vegetative cells show a typical bilayered cell wall and the heterocysts have a thikened wall. The thylakoid membranes in both heterocysts and vegetative cells are oftenseen forming whirls. During the division of vegetative cells, their contents aggregate and then redistribute.     

Spatial and temporal distribution of benthic Polychaeta from the continental shelf of Tamaulipas, Gulf of Mexico]

In three oceanographic cruises off southern Tamaulipas (May, July and November, 1992), a total of 102 sediment samples were collected by autonomous diving at depths of 2.5 to 20.5 m, with a cylindrical 4 liter acrylic tube. The samples were sieved (aperture size 0.5 and 1.0 mm). In total, 88 species of polychaete annelids were determined (33 families); 15 species are first records for Mexico and three for the Gulf of Mexico. The dominant species were Paraprionospio pinnata, Scoletoma verrilli, Ceratocephale oculata, Aricidea finitima, Apoprionospio pygmaea, Onuphis eremita oculata and Prionospio cristata; P. pinnata was the most abundant (14.4% of the total). Highest abundance and diversity of species was in May (63 species and 622 organisms), followed by July (48 species and 401 organism); November was lowest (47 species and 217 organisms). Most diversity and abundance were found in the sandy bottoms.     

Chromosome numbers and taxonomic implications in the fern genusAzolla (Azollaceae)

Investigation of chromosome numbers of allAzolla species, and for the first time of hybrids, has been undertaken. Removal of wax from the leaf surface proved invaluable in achieving clear cytological preparations and providing unambiguous chromosome numbers. In contrast to previous records, the speciesA. pinnata, A. filiculoides, A. filiculoides var.rubra, A. caroliniana, A. microphylla, andA. mexicana were found to be 2n=44, andA. nilotica to be 2n=52. Several triploids (2n=66) and one tetraploid (2n=88) were identified. No geographical pattern could be observed in the distribution of triploids which probably derive from the function of unreduced gametes. The chromosome number of hybrids occasionally deviates from the diploid chromosome number (2n=44). The small chromosome size limits karyotypic analysis and only differences in overall chromosome size can be observed. Taxonomic implications of chromosome numbers and sizes are discussed.     

Morphometric and morphological delineation of southern African species of Aethomys (Rodentia: Muridae)

Five species of African rock rats, Aethomys namaquensis, A. granti, A. silindensis, A. nyikae and A. chrysophilus, have to date been recognized in southern Africa. While the first three species are craniometrically well-delineated, morphometric analysis of cytogenetically known and other specimens of A. chrysophilus revealed that it comprises two sympatric, morphologically similar species, the nominate species and the newly recognized A. ineptus. This is in agreement with observations on cranial morphology and earlier investigations involving cytogenetics, protein electrophoresis, and gross sperm and bacular morphology. Contrary to published reports, the Central African A. nyikae does not extend into southern Africa, and the single previous record from eastern Zimbabwe is probably based on a misidentification.     

Changes in leaf nutrient traits and photosynthesis of four tree species: effects of elevated [CO2], N fertilization and canopy positions

Aims Leaf traits of trees exposed to elevated [CO₂] in association with other environmental factors are poorly understood in tropical and subtropical regions. Our goal was to investigate the impacts of elevated [CO₂] and N fertilization on leaf traits in southern China.Methods Four tree species, Schima superba Gardn. et Champ. (S. superba), Ormosia pinnata (Lour.) Merr (O. pinnata), Castanopsis hystrix AC. DC. (C. hystrix) and Acmena acuminatissima (Blume) Merr. et Perry (A. acuminatissima) were studied in a factorial combination of atmospheric [CO₂] (ambient at ~390 μmol mol ? 1 and elevated [CO₂] at ~700 μmol mol^-1) and N fertilization (ambient and ambient + 100 kg N ha^-1 yr^-1) in open-top chambers in southern China for 5 years. Leaf mass per unit leaf area (LMA), leaf nutrient concentration and photosynthesis (A sat) were measured.Important findings Results indicated that leaf traits and photosynthesis were affected differently by elevated [CO₂] and N fertilization among species. Elevated [CO₂] decreased LMA in all species, while N fertilization did not affect LMA. Leaf mass-based N concentration (N M) was significantly greater in O. pinnata and C. hystrix grown in elevated [CO₂] but was lower in S. superba. Leaf mass-based P concentration (P M) was significantly greater in C. hystrix and A. acuminatissima exposed to elevated [CO₂] but was lower in S. superba. N fertilization significantly increased P M in O. pinnata but decreased P M in S. superba. Photosynthetic stimulation in O. pinnata, C. hystrix and A. acuminatissima was sustained after 5 years of CO₂ fumigation. N fertilization did not modify the effects of elevated [CO₂] on photosynthesis. Leaf traits (N M, N A, P M, P A) and light-saturated photosynthesis were decreased from the upper to lower canopy. Canopy position did not alter the responses of leaf traits and photosynthesis to elevated [CO₂]. Results suggest that photosynthetic stimulation by elevated [CO₂] in native species in subtropical regions may be sustained in the long term.     

A cladistic phylogeny of the family Patellidae (Mollusca: Gastropoda)

A phylogenetic hypothesis for the patellid limpets is reconstructed by cladistic analysis of morphological characters from 37 species, representing all but one of the living members of the family. Characters included in the analysis are derived from shell shape and microstructure, headfoot and pallial complex, radula and sperm. The species fall into four clades, providing the basis for a new phylogenetic classification into four monophyletic genera: Helcion (four species; southern Africa), Cymbula (eight species; southern Africa, eastern Atlantic, southern Indian Ocean), Scutellastra (17 species; southern and southwestern Africa, Australia, Indo-West Pacific, Eastern Pacific) and Patella (nine species; northeastern Atlantic and Mediterranean). The analysis suggests sister-group relationships between Helcion and Cymbula, and between Scutellastra and Patella. In combination with present-day patterns of geographical distribution, this phylogenetic hypothesis is used to discuss the historical biogeography of the Patellidae. Scutellastra may have originated in southern Africa and dispersed across the Pacific, or alternatively may be a primitively Tethyan group. Both Helcion and Cymbula appear to have originated in southern Africa, but three Cymbula species have dispersed respectively to northwest Africa, St Helena and the southern Indian Ocean. The patellids of the northeastern Atlantic form a single clade, Patella (including P. pellucida), which may have arrived by northward dispersal of an ancestor from southern Africa, or possibly by vicariance of a widespread ancestral Tethyan distribution. The known fossil record of patellids is too fragmentary to permit choice between these alternatives.     

7. GENERAL NOTES

Hockey, P. A. R., Brooke, R. K., Cooper, J., Sinclair, J. C. &; Tree, A. J. 1986. Rare and vagrant scolopacid waders in southern Africa. Ostrich 57: 37–55.

Records of rare scolopacid waders in southern Africa are reviewed. 374 records of 15 species are accepted: seven of four Nearctic species. 51 of four Holarctic species and 316 of seven Palaearctic species. Their spatial and temporal (year and season) occurrence is analysed and their habitat requirements in southern Africa are described.     

无藻萍的RAPD分析及其在三膘组满江红种间关系研究中的应用

从满江红Azolla Lam.萍-藻共生体中提取DNA进行的RAPD系统分析通常忽视了满江红样品的异质性。本研究通过获得无藻的满江红,比较有藻萍、无藻萍和离体藻之间的RAPD指纹图谱。发现从有藻萍中提取DNA的扩增反应来源于萍藻双方DNA的共同影响。依引物和植物样本的不同,共生双方对扩增产物的贡献结果不同,说明了用无藻萍进行RAPD检测的重要性。对满江红三膘组5个种的11个无藻萍样本进行了RAPD分析,由9个引物产生的127个DNA多态片段用于计算样本间的Jaccard相似系数和UPGMA树状聚类图。结果     

Distribution,diversity and conservation of Anostraca (Crustacea: Branchiopoda) in southern Africa

Southern Africa is defined here as Africa south of the Zambezi and Kunene Rivers. Here, annual average rainfall, rainfall season, and effective temperature are climatic factors which influence anostracan distribution. The type of temporary pool also appears to have some effect on distribution. Areas of high species richness are not confined to any particular climatic region and such areas occur in arid, montane and subtropical regions of southern Africa. Forty-six anostracan species have been recorded from the subcontinent and 80% of these are endemic. IUCN Red Data assessment of species revealed that two species can be considered 'Critically Endangered', while a further four are 'Endangered', and three are 'Vulnerable'. Many parts of southern Africa have been inadequately sampled but in South Africa, where the anostracans are relatively well known, temporary pool inhabitants are threatened mainly by agriculture, urbanization, pollution and pesticides. This revised version was published online in August 2006 with corrections to the Cover Date.     

Phylogenetic relationships and generic delimitation in subtribe Arctotidinae (Asteraceae: Arctotideae) inferred by DNA sequence data from ITS and five chloroplast regions

Asteraceae are the largest family in southern Africa. Elucidating its origins and radiation in the region requires well-supported species-level phylogenies of the lineages. This paper presents a phylogenetic framework for subtribe Arctotidinae, which have a southern and eastern African-Australian distribution centered in the winter-rainfall region of South Africa. DNA sequence data from five chloroplast fragments (ndhF, psbA-trnH, rps16, trnS-trnfM, and trnT-trnF) and the nuclear ITS region were analyzed separately and in combination using parsimony and Bayesian methods. The data sets comprised exemplars from 18 ingroup species, representing the five currently accepted genera, and four outgroup species from Gorteriinae. All analyses indicated Arctotis and Haplocarpha are polyphyletic as presently circumscribed. The Australian-endemic Cymbonotus lawsonianus was placed within a strongly supported clade also containing A. arctotoides from South Africa and H. schimperi from eastern Africa. Retention of Dymondia and resurrection of Landtia at generic level are strongly supported. The phylogenetic hypotheses indicate the subtribe might have originated in temperate southern or eastern Africa, or it was ancestrally widespread in southern Africa and has diversified vicariously. The derived placement of C. lawsonianus indicates long-distance dispersal from southern Africa to Australia occurred.     

A conservation assessment of the freshwater crabs of southern Africa (Brachyura: Potamonautidae)

Recent taxonomic revisions of the freshwater crabs of southern Africa (Angola, Botswana, Lesotho, Mozambique, Namibia, South Africa, Swaziland, Zambia and Zimbabwe) allow accurate depictions of their diversity, distribution patterns and conservation status. The southern African region is home to nineteen species of freshwater crabs all belonging to the genus Potamonautes (family Potamonautidae). These crabs show high levels of species endemism (84%) to the southern African region and to the country of South Africa (74%). The conservation status of each species is assessed using the IUCN (2003) Red List criteria, based on detailed compilations of the majority of known specimens. The results indicate that one species should be considered vulnerable, fifteen species least concern and three species data deficient. The results have been utilized by the IUCN for Red Lists, and may prove useful when developing a conservation strategy for southern Africa’s endemic freshwater crab fauna.