Molecular Identification of Algal Endosymbionts in Large Miliolid Foraminifera: 1. Chlorophytes

Large miliolid foraminifers bear various types of algal endosymbionts including chlorophytes, dinoflagellates, rhodophytes, and diatoms. Symbiosis plays a key role in the adaptation of large foraminifera to survival and growth in oligotrophic seas. The identity and diversity of foraminiferal symbionts, however, remain largely unknown. In the present work we use ribosomal DNA (rDNA) sequences to identify chlorophyte endosymbionts in large miliolid foraminifera of the superfamily Soritacea. Partial 18S and complete Internal Transcribed Spacer (ITS) rDNA sequences were obtained from symbionts of eight species representing all genera of extant chlorophyte-bearing Soritacea. Phylogenetic analysis of the sequences confirms the previous fine structure-based identification of these endosymbionts as belonging to the genus Chlamydomonas. All foraminiferal symbionts form a monophyletic group closely related to Chlamydomonas noctigama. The group is composed of seven types identified in this study, including one previously morphologically described species, Chlamydomonas hedleyi. Each of these types can be considered as a separate species, based on the comparison of genetic differences observed between other established Chlamydomonas species. Several foraminiferal species share the same symbiont type, but only one species, Archaias angulatus, was found to bear more than one type.     

Fruit and seed ontogeny related to the seed behaviour of two tropical species of Caesalpinia (Leguminosae)

Caesalpinia echinata and C. ferrea var. ferrea have different seed behaviours and seed and fruit types. Comparison of the seed ontogeny and anatomy partly explained the differences in seed behaviour between these two species of Brazilian legumes; some differences were also related to fruit development. The seed coat in C. ferrea consisted of two layers of osteosclereids, as well as macrosclereids and fibres, to form a typical legume seed coat, whereas C. echinata had only macrosclereids and fibres. In C. echinata , the developing seed coat had paracytic stomata, a feature rarely found in legume seeds. These seed coat features may account for the low longevity of C. echinata seeds. The embryogeny was similar in both species, with no differences in the relationship between embryo growth and seed growth. The seeds of both species behaved as typical endospermic seeds, despite their different morphological classification (exendospermic orthodox seeds were described for C. echinata and endospermic orthodox seeds for C. ferrea ). Embryo growth in C. ferrea accelerated when the sclerenchyma of the pericarp was developing, whereas embryonic growth in C. echinata was associated with the conclusion of spine and secretory reservoir development in the pericarp. Other features observed included an endothelial layer that secreted mucilage in both species, a nucellar summit, which grew up into the micropyle, and a placental obturator that connected the ovarian tissue to the ovule in C. ferrea . © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 2004, 146 , 57–70.     

Evolution probing for semiochemicals based on secondary metabolites in the cuticles of three species of Halobates (Heteroptera: Gerridae)

We developed methods for characterizing semiochemicals in the cuticles of the sea-skater Halobates (Gerridae). Such substances may be involved in chemical communication at the sea surface and have been shown to act as sexual pheromones for a related marine insect Trochopus plumbeus (Veliidae). We identified 86 volatile compounds in extracts from three Halobates species ( H. micans Eschscholtz, H. hawaiiensis Usinger and H. sobrinus White) and used them to reconstruct the phylogeny of the clade. Sixty-seven of the compounds were found to be parsimony-informative. Suspected semiochemicals appear to be specific autapomorphies in the phylogram, and our results indicated that chemical profiles may be used to predict the phylogenetic history of Halobates . Moreover, the phylogenetic tree derived from our data is congruent with a previously published one based on morphology and mitochondrial DNA sequence (780 bp in the COI gene). The potential role of each compound to be used for chemical communication was also reviewed. At appropriate concentrations, some of the cuticular compounds, being partly hydrophobic and partly hydrophilic, could disperse on the sea surface and thereby play an energetically efficient role in chemical communication, e.g. mate location. Less dispersible components might act as 'sun-screens' and provide protection from UV-irradiation during daylight hours.  © 2003 The Linnean Society of London, Biological Journal of the Linnean Society , 2003, 80 , 671–688.     

The role of major histocompatibility complex diversity in vigour of fish males (Abramis brama L.) and parasite selection

The major histocompatibility complex (MHC) presents a group of genes with highly polymorphic loci involved in specific immune responses. The factors maintaining extensive MHC polymorphism have been questioned, considering three possible hypotheses of parasite‐mediated selection driving an extensive MHC diversity (i.e. heterozygote advantage, rare‐allele advantage, and favouring optimal MHC diversity). The patterns of MHC diversity of class IIB genes were investigated following two noncontradicting hypotheses, parasite‐driven selection and MHC‐based mating preferences, using males of common bream collected in the spawning period. Two allelic groups DAB1 and DAB3 were recognized from the phylogenetic analyses. Individuals expressed one or two alleles of the same or different allelic groups. Several individuals shared identical alleles; however, the presence of parasite species was not associated with the occurrence of a particular allele. The presence of different allelic groups (only DAB1, only DAB3, or both DAB1 and DAB3) in individuals was not associated with parasite presence or diversity. The expression of two DAB1 alleles was associated with higher endoparasite abundance. Moreover, nucleotide diversity in individuals expressing a single type of alleles (DAB1 or DAB3) increased with the abundance of ectoparasitic Dactylogyrus spp. (Monogenea) and Ergasilus sp. (Crustacea). This suggests that the expression of two alleles of a single allelic type is related to high metazoan parasite infection whereas no significant influence of parasitism on the combined allelic form (the presence of both DAB1 and DAB3 alleles) was found. Moreover, the expression of two alleles of a single allelic type was related to decreased immunocompetence measured by spleen size. The condition factor was higher in fish expressing the combined allelic type. Thus, the presence of alleles of different lineages in individuals appears to be advantageous for individual male fitness. The expression of a single allelic type was related to higher sexual ornamentation, which could support the role of MHC in the hypothesis of the sexual selection of ‘good genes’. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society, 2007, 90 , 525–538.     

New chromosome numbers, meiotic behaviour and pollen fertility in American taxa of Lupinus (Leguminosae): contributions to taxonomic and evolutionary studies

Original chromosome determinations are presented for 20 American Lupinus taxa, including, for the first time, unifoliolate species, together with first data on meiotic behaviour and pollen fertility for some South American species. Most of the Brazilian multifoliolate L. lanatus, L. rubriflorus, L. multiflorus, L. paranensis, L. bracteolaris and L. reitzii and unifoliolate L. crotalarioides, L. guaraniticus and L. velutinus accessions analysed presented regular chromosome pairing. Meiotic indexes and estimations of pollen viability were higher than 90% for all species and accessions analysed, reflecting the generally regular meiotic behaviour of these plants. Chromosome numbers were determined for the first time for the eastern South‐American species L. guaraniticus, L. crotalarioides, L. paranensis, L. paraguariensis and L. velutinus (n = 18 or 2n = 36) and for the Andean L. ballianus, L. eanophyllus, L. huaronensis, L. semperflorens, plus another eight taxa (2n = 48) from Peru and Bolivia, and L. bandelierae (2n = 36) from Bolivia. Chromosome numbers were confirmed for L. lanatus, L. rubriflorus (2n = 36), L. bracteolaris (2n = 34) and L. microphyllus (2n = 48). In the three accessions of the North American unifoliolate species, L. cumulicola and L. villosus, a chromosome number (2n = 52) previously unknown among American taxa was found. The results of the study, plus published data, support the suggestions that south‐eastern South American species are a group cytologically differentiated from the Andean as well as from most other American ones, and that the Brazilian and the North American unifoliolate Lupinus had independent origins. © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society, 2006, 150 , 229–240.     

Monthly survival of African Sylvia warblers in a seasonally arid tropical environment

Latitudinal gradients of life-history traits in animals are thought to be shaped by environmental variables. For example, it has been suggested that the increase in avian clutch size from the tropics towards the northern temperate regions is caused by a reduced survival of adult birds in the north due to increasing environmental seasonality. However, the tropical savannahs of East Africa show pronounced seasonality in resources caused by distinct rainy and dry seasons. This raises the question of whether survival and other life-history traits of birds living in these tropical savannahs are influenced by this seasonality, making them more similar to northern temperate species. We used 2-year monthly resighting data, a multistate modelling approach and the program MARK to test whether survival, transition probabilities between breeding states and other life-history traits of two resident Kenyan Sylvia species (Aves: Passeriformes: Sylviidae) are shaped by seasonality of rainfall in their environment. Contradicting our hypotheses, the two species showed only very slight influence of seasonality of rainfall on their survival. Survival in the dry months was hardly lower than in the rainy months. The species in the more seasonal environment ( S. boehmi , annual survival 71%) survived as well as the one in the more constant environment ( S. lugens , 56%). The observed survival rates correspond well to other life-history traits of the two species and are of similar magnitude to survival rates of other tropical passerines. This implies that either seasonality is not the driving force behind the life-history traits of the two species or the birds do not experience their environment as seasonal, as might be suggested by fluctuations in rainfall.     

The taxonomic and evolutionary significance of some juvenile characters in the Brassiceae

The shape of the cotyledon lamina and a few other juvenile characters are studied for some 140 taxa of the cruciferous tribe Brassiceae. They cast a number of doubts on the present botanical status of certain taxa, such as Diplotaxis siifolia, Erucastrum cardaminoides and Brassica balearica. The whole tribe Raphaninae appears rather unnatural when viewed from cotyledon evidence, which suggests that beak development and/or fruit reduction have evolved on different occasions. A primitive cotyledon type seems to be that showed by the genus Sinapidendron. It is nowadays still present in Brassica balearica, Oudneya africana and the oriental genus Orychophragmus. Some phenetic lines now represented by Moricandia, Foleyola, Hemicrambe, Diplotaxis and Brassica repanda may indicate ancient evolutionary trends derived from the primitive Sinapidendron-like Miocenic stock. Brassica ancestors could have either resembled B. repanda or evolved along the phenetic line now represented by the Diplotaxis Erucastrum-Brassica complex. A diphyletic or polyphyletic origin for the genus Brassica becomes thinkable.     

Photolytic Decarboxylation of Carboxyl-14C-labelled Indol-3yl-acetic Acid in Leaves of the Apple Tree

The nature and rate of degradation of carboxyl-¹⁴C-labelledindol-3y1-acetic acid (IAA-[l-¹⁴C]) were studied in apple leaves.The labelled auxin was applied to the cut surface of the growingshoot after the apical part had been removed. The respiratoryCO₂ absorbed by chromatographic paper as Na₂CO₃ then freed byphosphoric acid was quantitatively measured by an internal gascounter. It was found that the concentration of ¹⁴CO₂ evolvedby leaves was 77 times higher in daylight than in darkness.The ratio of ¹⁴CO₂/CO₂ obtained from respiration from the uppersurface of leaf blades was two and seven times higher than thatfrom the lower surface after 15 and 30 h of daylight, respectively.No such differences were noticed in darkness. Similarly, thetotal radioactivity of leaf tissues tripled in daylight, presumablybecause of photosynthetic incorporation of radioactive CO₂ evolvedduring decomposition of LAA. These facts demonstrate the photolyticcharacter of auxin decarboxylation in apple leaves. Prolongeddarkness seemed to provoke a large metabolite withdrawal fromleaves and, to some extent, to protect auxin against decarboxylation.     

A Simple Method for Paraffin and Plastic Embedding of Protozoa

SUMMARY. To avoid multiple centrifugation and considerable losses of material in preparing protozoa for paraffin and plastic embedding a simple method has been worked out, requiring only two centrifugations, one before and one after fixation. During the second centrifugation, which is done at 700 g for 10 minutes, the organisms form a cohesive pellet which may be removed from the centrifuge tube by means of a fine spatula and handled as a piece of tissue through the whole process of dehydration and embedding.     

Evidence of Actin in the Cytoskeleton of Microsporidia

Using transmission electron microscopy, immuno-electron microscopy, and biochemical techniques such as 2-D electrophoresis and immunoblotting, actin was found in all biological stages of the microsporidia Encephalitozoon hellem and Encephalitozoon cuniculi.