Pelagic coelenterates and eutrophication: a review

Although eutrophication is a widespread problem in marine waters, its effects are often difficult to separate from normal fluctuations of pelagic coelenterate populations and from other anthropogenic changes due to industrial pollution, construction, introductions, global warming and overfishing. The least complex situations are in small coastal water bodies such as the Caribbean lagoons and Scandinavian fjords. Typically, the diversity of pelagic coelenterates decreases, but the biomass of a small number of species (such as the hydromedusae Aglantha digitale and Rathkea octopunctata and the scyphomedusae Aurelia aurita and Cassiopea spp.) may increase. Adaptations that may allow these species to survive under eutrophic conditions are discussed.     

The uniqueness of Daubentonia

The aberrant features of the genus Daubentonia, such as the superficially rodent-like dentition, the globose and foreshortened brain case, and the filiform third manual digit have long been known. But the current assessment of the genus as lemuriform, and within that group as closest to the indriids, depends upon greater weight being placed upon other characteristics such as the cranial arterial pattern, the molariform teeth, and the developmental characteristics of the dentition. Prior multivariate morphometric studies have shown that though the shoulder structure of Daubentonia is uniquely different from that of all other primates, the structure of its pelvis may not be especially different from that of many relatively non-specialized primates. A large series of studies have been summated here in which many different anatomical regions (shoulder, arm, forearm, forelimb as a whole, pelvis, femur, hindlimb as a whole, forelimb and hindlimb combined, and total bodily proportions including limbs, trunk, and head) have been characterized osteometrically in a wide range of primate genera. The resulting data sets have been studied by discriminant function analyses. The differences that have been found are large enough that it can be confidently asserted that in its postcranial skeleton, Daubentonia is more different from the primates as a whole than is any other primate genus. These differences are big enough that their statistical and biological significance is not at all in doubt, notwithstanding the very small numbers of available specimens of this rare genus. They are so great that functional implications exist though they cannot, in our present state of knowledge of the habits of the genus, be ascribed with any certainty. They are so great indeed, paralleling the enormous differences of Daubentonia from other primates in its dentition, skull and cheiridia, that we may prefer to keep open minds about its taxonomic placement.     

A review of habitat selection by the swamp rat,Rattus lutreolus (Rodentia: Muridae)

Abstract This review clarifies important points on habitat selection by the Swamp Rat Rattus lutreolus (Rodentia: Muridae), a species that has been the subject of much research in Australia and has provided a useful model for understanding ecological and biological processes. It also provides an opportunity to cite important earlier research, not readily available through electronic search engines, thus bringing it into current literature to avoid its disappearance into Internet obscurity. We comment on some papers in the literature to correct errors detected and to emphasize the importance of due care in all aspects of a research project, including its reporting. We show that both floristic and structural components have been reported as important to an understanding of habitat and microhabitat selection by R. lutreolus and conclude that it is vegetation density that is of paramount importance. Female R. lutreolus are clearly dominant in driving microhabitat selection, occupying the ‘best’ or densest habitats with male R. lutreolus occupying the next best and Pseudomys or other species, where present occupying the remainder. This demonstrates the important role that intraspecific and interspecific competition play in determining habitat selection. Direct predation and the perception of predation risk may also play a role in habitat selection, again perceived to be pushing individuals towards denser vegetation, representing ‘better cover’. Whether these effects operate as bottom‐up or top‐down needs careful consideration. Climatic variables, such as ENSO‐affecting productivity, and related variables such as temperature and humidity may also play important roles in habitat selection, as can disturbance effects such as wildfire. The relative importance of all of these potential determining factors may vary from place to place, particularly when climatic clines are involved.     

Sociality in a bark-dwelling huntsman spider from Australia,Delena cancerides Walckenaer (Araneae: Sparassidae)

Summary Social behavior is reported for the first time in a member of the family Sparassidae (Araneae), the Australian huntsman spiderDelena cancerides Walckenaer. Unlike any previously known social spider, this is a bark dwelling species and, thus, its sociality cannot have its basis on an aerial web, the structure that has been considered central to the evolution of sociality in other spider species. Colonies ofD. cancerides may comprise up to 300 individuals living in close physical contact under the exfoliating bark of deadAcacia, Callitris andCasuarina species. Specimens maintained in the laboratory feed communally and capture prey jointly. Although this intranest tolerance and communal feeding behavior is reminiscent of other highly social spiders,D. cancerides notably differs from these other species in the extreme aggression shown towards members of foreign colonies, its outbred population structure, and lack of sex ratio bias. We suggest that sociality in this species may have been facilitated by the presence of extended maternal care in the ancestral phylogenetic lineage, as suggested by the occurrence of such behavior in related nonsocial species, and that colonial living may have arisen as a consequence of the reduction and fragmentation ofDelena's habitat associated with the rise to dominance of the eucalypts. The apparent colony recognition observed may have evolved becauseDelena's hunting habits may require mechanisms to locate one's own colony after foraging expeditions and to exclude wandering outsiders from entering one's nest, in contrast to web-bound species that do not need to leave their nest to forage. How the observed outbreeding is accomplished in the face ofDelena's extreme intolerance to members of other nests, as well as how new colonies are formed, are issues that have yet to be investigated.     

Chemistry and Pharmacology of Gynostemma pentaphyllum

In traditional Chinese medicine, Gynostemma pentaphyllum (Thunb.) Makino is a herbal drug of extreme versatility and has been extensively researched in China. The dammarane saponins isolated from Gynostemma pentaphyllum, namely gypenosides or gynosaponins, are believed to be the active components responsible for its various biological activities and reported clinical effects. This review attempts to encompass the available literature on Gynostemma pentaphyllum, from its cultivation to the isolation of its chemical entities and a summary of its diverse pharmacological properties attributed to its gypenoside content. Other aspects such as toxicology and pharmacokinetics are also discussed. In vitro and in vivo evidence suggests that Gynostemma pentaphyllum may complement the popular herbal medicine, Panax ginseng, as it also contains a high ginsenoside content and exhibits similar biological activities.     

Dispersal ability and relative abundance of Boeckella and Calamoecia (Copepoda: Calanoida) in Australian and New Zealand waters

Two calanoid copepod genera, Boeckella and Calamoecia have broadly similar geographic distributions in Australia but Boeckella is more common than Calamoecia. A field survey and literature search indicate that Boeckella is usually the first calanoid to colonize newly formed bodies of water, and Boeckella is more common in temporary pools and in high altitude environments. Boeckella usually produces larger clutches than Calamoecia, increasing its probability of establishment in lakes and ponds; calculations indicate that Boeckella's probability of establishment is far greater than that of Calamoecia. That Calamoecia is common on the North Island of New Zealand may be due to the presence of planktivorous fish; small species are more likely to survive in such environments. Calamoecia clutches may be able to move more often and farther than those of Boeckella but Calamoecia remains rare because its probability of establishment is low. Boeckella may be able to survive temporary pool environments not only because it can produce larger clutches, but also because many species in this genus are highly pigmented, and as such can survive brightly lighted environments. Patterns of abundance of North American diaptomids appear to be consistent with factors affecting those of Australian and New Zealand centropagids.     

Epigenetic silencing of TNFSF7 (CD70) by DNA methylation during progression to breast cancer

To escape the immune system, tumor cells may remove surface molecules such as the major histocompatibility complex (MHC) and co-stimulatory molecules, which are essential for recognition by lymphocytes. Down-regulation of the co-stimulatory molecules CD70 (TNFSF7) and CD80 may contribute to tumor cell survival; however, the mechanism of down-regulation of the TNFSF7 gene during tumorigenesis is poorly understood. Here we present evidence indicating that TNFSF7 gene expression is epigenetically down-regulated via DNA hypermethylation within its promoter region during progression in breast cancer cells in the isogenic MCF10 model. Bisulfite sequencing revealed that the CpG pairs at the proximal region of the TNFSF7 promoter are heavily methylated during progression of breast cancer cells but that methylation of the more distal sequences was not changed considerably. Thus, this epigenetic silencing of the TNFSF7 gene via hypermethylation of its proximal region may allow the benign and invasive MCF10 variants to escape immune surveillance.     

The impact of fire,and its potential role in limiting the distribution of <Emphasis Type="Italic">Bryophyllum delagoense</Emphasis> (Crassulaceae) in southern Africa

Increasing emphasis has been placed on identifying traits of introduced species which predispose them to invade, and characteristics of ecosystems which make them susceptible to invasion. Habitat disturbance such as floods, fires and tree-falls may make ecosystems more prone to invasion. However, in this study the absence of fire was considered to be a factor in facilitating the invasion potential of a Madagascan endemic, Bryophyllum delagoense. Fire trials in South Africa killed 89 and 45% of B. delagoense plants in a high and low intensity controlled fire, respectively, with tall plants and those growing in clumps more likely to escape being killed. A reduction in the incidence and intensity of fires may therefore facilitate the invasion of B. delagoense and contribute to its invasive potential. Overgrazing, which reduces the frequency and intensity of fires probably facilitates the invasion of large and small succulent species. In South Africa, B. delagoense is still considered to be a minor weed or garden escape, despite its introduction to southern Africa 175 years earlier than in Australia, where it is extremely invasive. However, other succulents such as Opuntia species have become invasive on both continents, confounding our hypothesis that fire may be inhibiting B. delagoense from becoming invasive in southern Africa. However, closer analysis of Opuntia literature indicates that smaller species, similar in size to B. delagoense, are more likely to be killed, even by low intensity fires. We speculate that B. delagoense is more invasive in Australia because of a reduction in the frequency and intensity of fires and that fire is, amongst other factors, largely responsible for inhibiting its invasion potential in southern Africa.     

Dispersed growth of Streptomyces in liquid culture

Summary The study of the physiology of the filamentous bacterium Streptomyces is inhibited by its formation of mycelial pellets in liquid cultures. It is demonstrated that dispersed growth may be achieved by the addition of polymers to the culture medium. Uncharged polymers, such as polyethylene glycol, are relatively ineffective but polyanions such as agar, Carbopol and Junlon produce dispersed cultures when included in a defined growth medium at low concentrations. Junlon-containing media enable optical density measurements to be used to follow batch growth of Streptomyces. Improvements in both biomass yield and product yield of the pigmented antibiotic actinorhodin were found to result from the incorporation of Junlon into minimal medium.     

Antioxidant properties of MitoTEMPOL and its hydroxylamine

Piperidine nitroxides such as TEMPOL have been widely used as antioxidants in vitro and in vivo. MitoTEMPOL is a mitochondria-targeted derivative of TEMPOL designed to protect mitochondria from the oxidative damage that they accumulate, but once there is rapidly reduced to its hydroxylamine, MitoTEMPOL-H. As little is known about the antioxidant efficacy of hydroxylamines, this study has assessed the antioxidant activity of both MitoTEMPOL and MitoTEMPOL-H. The hydroxylamine was more effective at preventing lipid-peroxidation than MitoTEMPOL and decreased oxidative damage to mitochondrial DNA caused by menadione. In contrast to MitoTEMPOL, MitoTEMPOL-H has no superoxide dismutase activity and its antioxidant actions are likely to be mediated by hydrogen atom donation. Therefore, even though MitoTEMPOL is rapidly reduced to MitoTEMPOL-H in cells, it remains an effective antioxidant. Furthermore, as TEMPOL is also reduced to a hydroxylamine in vivo, many of its antioxidant effects may also be mediated by its hydroxylamine.     

Absence of predation eliminates coexistence: experience from the fish–zooplankton interface

Examples from fishless aquatic habitats show that competition among zooplankton for resources instigates rapid exclusion of competitively inferior species in the absence of fish predation, and leads to resource monopolization by the superior competitor. This may be a single species or a few clones with large body size: a cladoceran such as Daphnia pulicaria, or a branchiopod such as Artemia franciscana, each building its population to a density far higher than those found in habitats with fish. The example of zooplankton from two different fish-free habitats demonstrates the overpowering force of fish predation by highlighting the consequences of its absence. Released from the mortality caused by predation, a population of a superior competitor remains at a density equal to the carrying capacity of its habitat, in a steady state with its food resources, consisting of small green flagellate algae, which are successful in compensating high loss rates due to grazing, by fast growth. In such a situation, the high filtering rate of Daphnia or Artemia reduces resources to levels that are sufficient for assimilation to cover the costs of respiration (threshold food concentration) in adults but not in juveniles. This implies long periods of persistence of adults refraining from producing live young, because production of instantly hatching eggs would be maladaptive. Severe competition for limiting resources imposes a strong selective pressure for postponing reproduction or for producing resting eggs until food levels have increased. Offspring can only survive when born in a short time window between such an increase in food levels and its subsequent decline resulting from population growth and intense grazing by juveniles. Such zooplanktons become not only a single-species community, but also form a single cohort with a long-lifespan population. The observations support the notion that diversity may be sustained only where predation keeps densities of coexisting species at levels much below the carrying capacity, as suggested by Hutchinson 50 years ago.     

Tyrosinase‐Mediated Formation of a Reactive Quinone from the Depigmenting Agents, 4‐tert‐Butylphenol and 4‐tert‐Butylcatechol

Exposure of the skin to certain phenols or catechols such as 4‐tert‐butylphenol (TBP) and 4‐tert‐butylcatechol (TBC) may cause leukoderma. These substances are used in the polymer industry and numerous cases have been reported. Several theories of the mechanism for chemical leukoderma have been suggested. In the present study, TBP and TBC are shown to be oxidised by tyrosinase. The oxidation of TBC yields a quinone that is further investigated on its reactions with cysteine or glutathione (GSH). The products formed are isolated and identified by mass spectrometry and nuclear magnetic resonance as being 4‐tert‐butyl‐6‐S‐cysteinylcatechol (cys‐TBC) and 4‐tert‐butyl‐6‐S‐glutathionylcatechol (GS‐TBC). The reactive quinone is a strongly electrophilic substance that rapidly reacts with GSH. A depletion of the GSH defence system may give conditions where the quinone lives long enough to effect its toxic properties. The influence of the reactive tert‐butylquinone on enzymatic activities is demonstrated by the inhibition of glyceraldehyde‐3‐phosphate dehydrogenase.     

Friend or foe? A parasitic wasp shifts the cost/benefit ratio in a nursery pollination system impacting plant fitness

Nursery pollination systems are species interactions where pollinators also act as fruit/seed herbivores of the plant partner. While the plants depend on associated insects for pollination, the insects depend on the plants’ reproductive structures for larval development. The outcome of these interactions is thus placed on a gradient between mutualism and antagonism. Less specialized interactions may fluctuate along this gradient with the ecological context, where natural enemies can play an important role. We studied whether a natural enemy may impact the level of seed consumption of a nursery pollinator and how this in turn may influence individual plant fitness. We used the plant Silene latifolia, its herbivore Hadena bicruris, and its ectoparasitoid Bracon variator as a model plant–herbivore–natural enemy system. We investigated seed output, germination, survival, and flower production as proxies for individual plant fitness. We show that B. variator decreases the level of seed consumption by H. bicruris larvae which in turn increased seed output in S. latifolia plants, suggesting that parasitism by B. variator may act as a regulator in the system. However, our results also show that plant survival and flower production decrease with higher seed densities, and therefore, an increase in seed output may be less beneficial for plant fitness than estimated from seed output alone. Our study should add another layer to the complex discussion of whether parasitoids contribute to plant fitness, as we show that taking simple proxies such as seed output is insufficient to determine the net effect of multitrophic interactions.     

Bacillus and relatives in foodborne illness

Species of Bacillus and related genera have long been troublesome to food producers on account of their resistant endospores. These organisms have undergone huge taxonomic changes in the last 30 years, with numbers of genera and species now standing at 56 and over 545, respectively. Despite this expansion, relatively few new species have been isolated from infections, few are associated with food and no important new agents of foodborne illness have been reported. What has changed is our knowledge of the established agents. Bacillus cereus is well known as a cause of food poisoning, and much more is now understood about its toxins and their involvement in infections and intoxications. Also, although B. licheniformis, B. subtilis and B. pumilus have occasionally been isolated from cases of food‐associated illness, their roles were usually uncertain. Much more is now known about the toxins that strains of these species may produce, so that their significances in such episodes are clearer; however, it is still unclear why such cases are so rarely reported. Another important development is the use of aerobic endosporeformers as probiotics, as the potentials of such organisms to cause illness or to be sources of antibiotic resistance need to be borne in mind.     

Observations on the ultrastructure, mode of infectivity and host range of xenosomes

Xenosomes are infectious bacterial-like symbionts that reside in the cytoplasm of certain strains of the marine hymenostome ciliate, Parauronema acutum. Ultrastructural studies of xenosomes of one such strain, P. acutum, 110/3, reveal that the particles possess a cell envelope whose outer membrane resembles that of Gramnegative bacteria. Unlike typical Gram-negative bacteria, however, xenosomes possess a much reduced ‘murein’ layer. The DNA is not located in a ‘nucleosome’ or ‘nuclear body’ as it is in most bacteria, but may be found dispersed throughout the internal contents of the particle. Xenosomes are capable of infecting several strains of Parauronema spp. and at least one other ciliate of marine origin, Miamiensis avidus, Ma. They are also capable of inhibiting the growth of certain marine ciliate strains, particularly those of the genus Uronema. Infectivity may be related to the fact that the particles are motile. When released from the host protozoan, they may be seen spinning or darting rapidly, suggesting the presence of a motile apparatus. Phosphotungstic acid staining of the released particles show that they do, indeed, possess bacterial-like flagella. The average number of flagella per particle observed was two, although some particles were seen with as many as five. A flagellum may occur at almost any point on the surface of the particle and is characteristically wider near its point of insertion into the cell envelope than it is near its tip. During normal growth in axenic culture, xenosomes are actively released into the ambient medium. Particles, thus released, rapidly lose their capacity to infect susceptible hosts, and this capacity parallels their ability to remain motile.     

Cell polarity and the mechanism of asymmetric cell division

During development one mechanism for generating different cell types is asymmetric cell division, by which a cell divides and contributes different factors to each of its daughter cells. Asymmetric cell division occurs through out the eukaryotic kingdom, from yeast to humans. Many asymmetric cell divisions occur in a defined orientation. This implies a cellular mechanism for sensing direction, which must ultimately lead to differences in gene expression between two daughter cells. In this review, we describe two classes of molecules: regulatory factors that are differentially expressed upon asymmetric cell division, and components of a signal transduction pathway that may define cell polarity. The lin-11 and mec-3 genes of C. elegans, the Isl-1 gene of mammals and the HO gene of yeast, encode regulatory factors that determine cell type of one daughter after asymmetric cell division. The CDC24 and CDC42 genes of yeast affect both bud positioning and orientation of mating projections, and thus may define a general cellular polarity. We speculate that molecules such as Cdc24 and Cdc42 may regulate expression of genes such as lin-11, mec-3, Isl-1 and HO upon asymmetric cell division.     

Natural organic matter (NOM) has the potential to modify the multixenobiotic resistance (MXR) activity in freshwater amphipods Eulimnogammarus cyaneus and E. verrucosus

Based on the chemical features of natural organic matter (NOM) with its variety of functional groups, we hypothesized that NOM will modify the multixenobiotic-resistance (MXR) of an organism as xenobiotic chemicals do. The MXR system is a general first rather non-specific line of defense against environmental contaminants. The aim of this study was to compare the impacts on MXR activity in amphipod species (Eulimnogammarus cyaneus and E. verrucosus, from Lake Baikal) stressed by cadmium chloride or dissolved NOM for 24 h. NOM exposure concentrations were environmentally realistic. MXR activity was assessed based on rhodamine B efflux; its specificity was proven by a verapamil inhibition assay. It was shown that both NOM and CdCl₂ lead to substantial reduction of the rhodamine B efflux. This suggests that NOM may be regarded as a chemosensor which is able to reduce the efficiency of the MXR system. Possible mechanisms of direct NOM impact on MXR processes are discussed, such as peroxidation of the membranes (including P-glycoproteins) or internal blockage of the MXR pump by bioconcentrated NOM. In general, our results show that well-developed depuration pathways of freshwater organisms in contaminated environments may be impaired by strong chemical stressors and, more important, by natural biogeochemical matrices such as humic substances — humic substances are present in all freshwater systems.     

Codon usage bias: causative factors,quantification methods and genome‐wide patterns: with emphasis on insect genomes

Codon usage bias refers to the phenomenon where specific codons are used more often than other synonymous codons during translation of genes, the extent of which varies within and among species. Molecular evolutionary investigations suggest that codon bias is manifested as a result of balance between mutational and translational selection of such genes and that this phenomenon is widespread across species and may contribute to genome evolution in a significant manner. With the advent of whole‐genome sequencing of numerous species, both prokaryotes and eukaryotes, genome‐wide patterns of codon bias are emerging in different organisms. Various factors such as expression level, GC content, recombination rates, RNA stability, codon position, gene length and others (including environmental stress and population size) can influence codon usage bias within and among species. Moreover, there has been a continuous quest towards developing new concepts and tools to measure the extent of codon usage bias of genes. In this review, we outline the fundamental concepts of evolution of the genetic code, discuss various factors that may influence biased usage of synonymous codons and then outline different principles and methods of measurement of codon usage bias. Finally, we discuss selected studies performed using whole‐genome sequences of different insect species to show how codon bias patterns vary within and among genomes. We conclude with generalized remarks on specific emerging aspects of codon bias studies and highlight the recent explosion of genome‐sequencing efforts on arthropods (such as twelve Drosophila species, species of ants, honeybee, Nasonia and Anopheles mosquitoes as well as the recent launch of a genome‐sequencing project involving 5000 insects and other arthropods) that may help us to understand better the evolution of codon bias and its biological significance.     

Blastogeny in tabulate corals: case studies using X‐ray microtomography

X‐ray microtomography (XMT) is a non‐invasive and non‐destructive method that has often been used to study fossils. It allows serial sections to be made as little as few micrometers apart; such a resolution is unachievable for classical serial sectioning; moreover, in contrast to the latter, the specimen is not destroyed. Microtomography can, however, be applied only in cases where differences in X‐ray absorption between the skeleton and its infilling are great. We show that this method may be also applied to tabulate corals. Case studies of blastogeny are based on Silurian (Aulopora, Favosites) and Devonian (Thamnopora) specimens from Poland. We show that the sequence of events in the blastogeny of Aulopora sp. is different from that of ‘Aulopora serpens minor’ from the Devonian of the Holy Cross Mountains and similar to auloporids from the Devonian of England. Blastogeny in Favosites is very similar to that known from the related genera Squameofavosites and Thamnopora. This suggests that members of the genus Aulopora may be more diversified within the genus (as presently understood) than genera within the Favositidae.