The nervous system of Tricladida. IV. Neuroanatomy of Planaria torva (Paludicola,Planaridae): an immunocytochemical study

Characters of the nervous system have scarcely been used in consideration of the phylogenetic relationships of the Tricladida. In order to contribute characters toward this end, we studied the nervous system of Planaria torva with immunocytochemical methods and we compare the results with what is known of nervous system structure in other triclads. Antisera against four neuroactive substances were used: neuropeptide F (NPF), RFamide, GYIRFamide, and serotonin (5-HT). All four substances showed positive immunoreactions throughout the nervous system; and the patterns of distribution of the first three were similar, while 5-HT showed a distinct distribution. The organization of these nervous system elements in Planariidae and Dendrocoelidae resembles that of the Maricola but differs from that of the Dugesiidae. The results support the hypotheses that the Paludicola is a more advanced taxon than the Maricola and that the Planariidae and Dendrocoelidae together are a sister group of the Dugesiidae. This revised version was published online in July 2006 with corrections to the Cover Date.     

Ontogenetic patterns and phylogenetic trends in freshwater flatworms (Tricladida); constraint or selection?

Semelparity and iteroparity are unevenly distributed among the families of the Paludicola and this implies that there have been taxonomic restrictions on life-history evolution. Species differ in their investments in reproduction and high levels can be related, causally, to reduced life-spans; i.e. semelparous species invest more in reproduction than iteroparous species. However, there does not appear to be any fundamental reason why the extent and timing of these investments should not be open to modification by natural selection.A major morphological difference between the predominantly semelparous Dendrocoelidae and the predominantly iteroparous Dugesiidae and Planariidae is the presence of an anterior adhesive organ; dendrocoelids have one, but members of the other families do not. A plausible scenario can be formulated relating this structure, causally, to enhanced juvenile survivorship which, in turn, favors the semelparous life history.     

A robust molecular phylogeny of the Tricladida (Platyhelminthes: Seriata) with a discussion on morphological synapomorphies.

The suborder Tricladida (Platyhelminthes: Turbellaria, Seriata) comprises most well-known species of free-living flatworms. Four infraorders are recognized: (i) the Maricola (marine planarians); (ii) the Cavernicola (a group of primarily cavernicolan planarians); (iii) the Paludicola (freshwater planarians); and (iv) the Terricola (land planarians). The phylogenetic relationships among these infraorders have been analysed using morphological characters, but they remain uncertain. Here we analyse the phylogeny and classification of the Tricladida, with additional, independent, molecular data from complete sequences of 18S rDNA and 18S rRNA. We use maximum parsimony and neighbour-joining methods and the characterization of a unique gene duplication event involving the Terricola and the dugesiids to reconstruct the phylogeny. The results show that the Maricola is monophyletic and is the primitive sister group to the rest of the Tricladida (the Paludicola plus the Terricola). The Paludicola are paraphyletic since the Terricola and one paludicolan family, the Dugesiidae, share a more recent common ancestor than the dugesiids with other paludicolans (dendrocoelids and planariids). A reassessment of morphological evidence may confirm the apparent redundancy of the existing infraorders Paludicola and Terricola. In the meantime, we suggest replacing the Paludicola and Terricola with a new clade, the Continenticola, which comprises the families Dugesiidae, Planariidae, Dendrocoelidae and the Terricola.     

Chromosome bands in freshwater triclads

Four species of Triclads belonging to three families, Dugesia polychroa and Dugesia mediterranea (Dugesiidae), Planaria torva (Planariidae) and Dendrocoelum lacteum (Dendrocoelidae) were studied for chromosome banding: C-banding for all the species, ASG banding for Dugesia polychroa and G-banding for Dugesia polychroa and Dugesia mediterranea. C-banding results for Dugesia lugubris-polychroa group suggest a high level of heterochromatin evolution in the group. Small bands strictly limited to the centromeric region were seen in Dugusia lugubris and this pattern is similar to the patterns of some species belonging to other families, notably Planaria torva and Dendrocoelum lacteum. This could be considered a primitive character. In contrast numerous heterochromatin bands which are useful to characterize the different karyotypes were seen in Dugesia polychroa and Dugesia mediterranea. Our data suggest that heterochromatin is important in freshwater triclad speciation.     

Localization of the antigen for the monoclonal antibody ②9F11-B-E4 interspecific cross-reaction in the freshwater triclads

The localization of the antigen for monoclonal antibody 9F11-B-E₄ was clarified by immuno-electron microscopy. The antigens were localized on the mitochondria and Golgi bodies in the male germ cells and on the secretory granules of various glands cells in the penis bulb and subepidermal parenchymal tissue of Phagocata vivida. The results of the interspecific cross-reaction tests with seven other freshwater triclads showed that these secretory granules are species-specific. A positive interspecific reaction was showed with Dugesia (family Dugesiidae), but not with Polycelis within the same family Planariidae which suggests the position of Phagocata within the Planariidae needs to be reassesed.     

Origin and Evolution of Paralogous rRNA Gene Clusters Within the Flatworm Family Dugesiidae (Platyhelminthes, Tricladida)

Analysis of the 18S rDNA sequences of five species of the family Dugesiidae (phylum Platyhelminthes, suborder Tricladida, infraorder Paludicola) and eight species belonging to families Dendrocoelidae and Planaridae and to the infraorder Maricola showed that members of the family Dugesiidae have two types of 18S rDNA genes, while the rest of the species have only one. The duplication event also affected the ITS-1, 5.8S, ITS-2 region and probably the 28S gene. The mean divergence value between the type I and the type II sequences is 9% and type II 18S rDNA genes are evolving 2.3 times more rapidly than type I. The evolutionary rates of type I and type II genes were calibrated from biogeographical data, and an approximate date for the duplication event of 80–120 million years ago was calculated. The type II gene was shown, by RT-PCR, to be transcribed in adult individuals of Schmidtea polychroa, though at very low levels. This result, together with the fact that most of the functionally important positions for small-subunit rRNA in prokaryotes have been conserved, indicates that the type II gene is probably functional. Received: 24 March 1998 / Accepted: 17 March 1999     

Towards a phylogenetic classification of dendrocoelid freshwater planarians (Platyhelminthes): a morphological and eclectic approach

We explore and review the taxonomic distribution of morphological features that may be used as supporting apomorphies for the monophyletic status of various taxa in future, more comprehensive phylogenetic analyses of the dendrocoelid freshwater planarians and their close relatives. Characters examined are: (i) musculature of the pharynx; (ii) anatomy of the eye; (iii) distribution of testis follicles along the longitudinal axis of the body; (iv) epidermis of the body wall; (v) musculature of the ventral body wall; (vi) presence or absence of a penis papilla; (vii) position of the mouth opening; and (viii) anterior adhesive organ. A phylogenetic hypothesis, in the form of a character state tree, is developed. This hypothesis suggests that the Kenkiidae should be resurrected as a separate family, sharing a sistergroup relationship with the Dendrocoelidae. This sistergroup relationship is supported by the shared presence of an apomorphic anterior adhesive organ. Although the shape of the anterior adhesive organ, both within and between kenkiids and dendrocoelids, may differ considerably between species, they are all constructed according to the same principles. The monophyly of the Kenkiidae is supported by the presence of an apomorphic thickening of the marginal zone of the epidermis and presumably also by the presence of prepharyngeal testes. Within the Kenkiidae, the genus Macrocotyla should be considered as a junior synonym of Kenkia, which is characterized by the presence of an apomorphic ‘planariid pharynx‐type 2’. The monophyly of the Dendrocoelidae is suggested by the presence of a dendrocoelid type of pharynx. It is shown that multicellular eye cups with numerous photoreceptor cells are not restricted to the Dugesiidae and the Terricola but are also characteristic for the Dendrocoelidae; the phylogenetic implications of this character state distribution are discussed. It is pointed out that in planarians there may be a relationship between: (i) body size, the size of an eye cup and the number of its constituent pigment cells; and (ii) the size of an eye cup and the number of photoreceptor cells that it contains. Some tentative phylogenetic groups are suggested on the basis of the following presumed apomorphic characters: presence of transverse fibres in the ventral subepidermal musculature, presence of an extra longitudinal muscle layer in the outer pharynx musculature, a mouth opening that has shifted anteriad. It is suggested that the presumed monophyly of the genus Bdellocephala is supported by the apomorphic absence of a penis papilla, combined with a penial lumen provided with many plicae.     

Molecular analysis of the diversity of terrestrial planarians (Platyhelminthes, Tricladida, Continenticola) in the Iberian Peninsula

This work is a prospective study to estimate the potential species diversity of terrestrial planarians in the Iberian Peninsula. Live specimens were collected from several Iberian localities and assigned to different morphotypes on the basis of their external morphological characteristics. From the same specimens, sequences from the mitochondrial Cytochrome Oxidasa subunit I (COI) and from the nuclear ribosomal gene 18S rRNA were obtained. Sequences from GenBank of the families Dendrocoelidae, Planariidae, Bipaliidae, Geoplanidae and Rhynchodemidae have been used as outgroups in the phylogenetic analysis. The results showed that terrestrial planarians have a wide distribution in the Peninsula, with all individuals found belonging to the Rhynchodemidae family. Morphological observations indicated the presence of 10 morphospecies confirmed by the molecular analyses. At the same time, COI sequences were successfully used as a molecular marker for species identification in the barcoding mode, which is of great use in groups like this with few external morphological characteristics. The combined data strongly suggest the presence of at least 15 species in the Iberian Peninsula, a number that nearly doubles previous estimates, indicating that terrestrial planarians are more diverse than expected in the region and, as proposed, may be a good biodiversity indicator and model for biogeographical studies.     

Evolutionary Analysis of Mitogenomes from Parasitic and Free-Living Flatworms

Mitochondrial genomes (mitogenomes) are useful and relatively accessible sources of molecular data to explore and understand the evolutionary history and relationships of eukaryotic organisms across diverse taxonomic levels. The availability of complete mitogenomes from Platyhelminthes is limited; of the 40 or so published most are from parasitic flatworms (Neodermata). Here, we present the mitogenomes of two free-living flatworms (Tricladida): the complete genome of the freshwater species Crenobia alpina (Planariidae) and a nearly complete genome of the land planarian Obama sp. (Geoplanidae). Moreover, we have reanotated the published mitogenome of the species Dugesia japonica (Dugesiidae). This contribution almost doubles the total number of mtDNAs published for Tricladida, a species-rich group including model organisms and economically important invasive species. We took the opportunity to conduct comparative mitogenomic analyses between available free-living and selected parasitic flatworms in order to gain insights into the putative effect of life cycle on nucleotide composition through mutation and natural selection. Unexpectedly, we did not find any molecular hallmark of a selective relaxation in mitogenomes of parasitic flatworms; on the contrary, three out of the four studied free-living triclad mitogenomes exhibit higher A+T content and selective relaxation levels. Additionally, we provide new and valuable molecular data to develop markers for future phylogenetic studies on planariids and geoplanids.     

Molecular phylogeny of land and freshwater planarians (Tricladida, Platyhelminthes): from freshwater to land and back

The suborder Tricladida (phylum Platyhelminthes) comprises the well-known free-living flatworms, taxonomically grouped into three infraorders according to their ecology: Maricola (marine planarians), Paludicola (freshwater planarians), and Terricola (land planarians). Molecular analyses have demonstrated that the Paludicola are paraphyletic, the Terricola being the sister group of one of the three paludicolan families, the Dugesiidae. However, neither 18S rDNA nor COI based trees have been able to resolve the relationships among species of Terricola and Dugesiidae, particularly the monophyly of Terricola. Here, we present new molecular data including sequences of nuclear genes (18S rDNA, 28S rDNA) and a mitochondrial gene (COI) of a wider sample of dugesiid and terricolan species. The new sequences have been analyzed, together with those previously obtained, in independent and concatenated analyses using maximum likelihood and bayesian methods. The results show that, although some parts of the trees remain poorly resolved, they support a monophyletic origin for Terricola followed by a likely return of some species to freshwater habitats. Relationships within the monophyletic group of Dugesiidae are clearly resolved, and relationships among some terricolan subfamilies are also clearly established and point to the need for a thorough revision of Terricola taxonomy.     

Chauvinism in science

Is Science chauvinistic? It is not, but scientists often are. How does chauvinism in Science manifest itself? Could it be that we are genetically programmed to reject those we see as “foreign”?     

Phylogenetic relationships of the genus Dugesia (Platyhelminthes, Tricladida, Paludicola)

A phylogenetic analysis was performed on the genera and subgenera within the freshwater triclad family Dugesiidae, based on 19 terminal taxa and 17 morphological characters. The phylogenetic tree proposed has length of 27 steps and consistency index of 0.66. This phylogenetic hypothesis implies that the current genus Dugesia is paraphyletic and that its subgenera Girardia, Schmidiea and Dugesia S.S. should be elevated to the rank of genus. The genera Cura, Spathula and Neppia are presumed monophyletic by default because the database was unable to provide autapomorphies for any of these genera. The genera Dugesia S.S. and Neppia share sistergroup relationship. Several characters are discussed which were previously considered to be of phylogenetic importance but were not included in the present analysis. It is emphasized that sensory organs form potentially useful set of phylogenetic characters for the Dugesiidae.     

Changing Islam,changing the world: contrasting visions within political Islam

ABSTRACT

How do political Islamists, movements and thinkers view political change? To what extent do they promote violence as a means of bringing about change? Are they themselves willing to change and adapt to modern political systems? There is a wide array of movements in the Muslim world that grapple with these questions and as a consequence, numerous answers and disagreements. This paper will focus on three cardinal and contested issues: Is violence a legitimate means to bring about change? Is it legitimate to adopt Western political institutions? How should Muslim movements and regimes coexist with ancient political entities such as tribes and ethnic groups? By comparing and contrasting the political outlooks of the Muslim Brothers and the Salafi-Jihadis, the article highlights the ideological gaps between moderate and militant political Islam.     

Transmission of Pneumocystis infection in humans

Is Pneumocystis pneumonia (PcP) a transmissible fungal disease? Does nosocomial PcP occur? Is there Pneumocystis transmission in the community? These questions, which could not be tackled before the 2000s, may at present be approached using either noninvasive detection methods or experimental transmission models. Represented by a unique entity (P.?carinii) for almost one century, the Pneumocystis genus was shown to contain several species, being P.?jirovecii the sole species identified in humans hitherto. Molecular methods combined with cross infection experiments revealed strong host specificity that precludes Pneumocystis inter-species transmission. In contrast, respiratory transmission between mammals of a same species is usually highly active, even between immunocompetent hosts. Other transmission ways could also exist. New data show that human being is the unique P.?jirovecii reservoir; it would constitute the sole infection source in both hospital and community.     

Seed plant phylogeny: Demise of the anthophyte hypothesis?

Recent molecular phylogenetic studies indicate, surprisingly, that Gnetales are related to conifers, or even derived from them, and that no other extant seed plants are closely related to angiosperms. Are these results believable? Is this a clash between molecules and morphology?     

Comparing Families of Dynamic Causal Models

Mathematical models of scientific data can be formally compared using Bayesian model evidence. Previous applications in the biological sciences have mainly focussed on model selection in which one first selects the model with the highest evidence and then makes inferences based on the parameters of that model. This “best model” approach is very useful but can become brittle if there are a large number of models to compare, and if different subjects use different models. To overcome this shortcoming we propose the combination of two further approaches: (i) family level inference and (ii) Bayesian model averaging within families. Family level inference removes uncertainty about aspects of model structure other than the characteristic of interest. For example: What are the inputs to the system? Is processing serial or parallel? Is it linear or nonlinear? Is it mediated by a single, crucial connection? We apply Bayesian model averaging within families to provide inferences about parameters that are independent of further assumptions about model structure. We illustrate the methods using Dynamic Causal Models of brain imaging data.     

The viable but nonculturable phenotype: a crossroads in the life-cycle of non-differentiating bacteria?

In nature, prokaryotes must face alternating periods of prosperity and adversity. Differentiating bacteria confront situations of adversity by developing resistant structures. When there is a plentiful period, they adopt a vegetative state and when the period is adverse, a resistant structure, thereby completing a cycle. Non-differentiating bacteria do not develop such morphological distinct resistant structures. It has been proposed that many of these bacteria withstand periods of adversity by adopting the viable but nonculturable phenotype (VBNC). Bacteria of this phenotype conserve detectable metabolic function but become unculturable. Is it possible that the VBNC phenotype can revert to a culturable state, and vice versa, thus establishing a life-cycle? This review presents and evaluates different hypotheses regarding this question. Moreover, it attempts to analyse and proffer answers to other questions related to this phenotype. Is this a successful phenotype which prolongs survival? Is this a strategy for the survival of individual cells, or is it a strategy for the survival of a population? Finally, is it possible that this phenotype is, in fact, an example of altruistic death?     

Narrative Identity in Third Party Reproduction: Normative Aspects and Ethical Challenges

In the last few decades, assisted reproduction has introduced new challenges to the way people conceive and build their families. While the numbers of donor-conceived (DC) individuals have increased worldwide, there are still many controversies concerning access to donor information. Is there a fundamental moral right to know one’s genetic background? What does identity in DC families mean? Is there any relationship between identity formation and disclosure of genetic origins? These questions are addressed by analysing core regulatory discourse (ethical recommendations and codes of practice). This analysis shows that the notion of narrative identity is suitable for defining and answering these questions. This review analyses the meaning of resemblance in DC families and the way donors are selected following affinity-ties and discusses disclosure strategies and agreements. As a preliminary conclusion, it could be said that, in the field of third-party reproduction, knowing about the donor conception significantly contributes towards the development of a narrative identity and also serves as a moral basis for the child’s right to know.     

Vascular considerations in the use of a latissimus dorsi myocutaneous flap after a mastectomy with an axillary dissection.

Is an intact thoracodorsal vascular pedicle necessary for clinical rotation of a latissimus dorsi myocutaneous flap? Our laboratory and clinical experiences indicate that it is not necessary. These are described herein.     

Applying Weight-of-Evidence in Retrospective Ecological Risk Assessment When Quantitative Data Are Limited

Retrospective ecological risk assessment attempts to identify likely causal agents to explain adverse effects that have occurred in ecological targets. It can never be decisive since it is post hoc and usually based on limited evidence that is rarely very quantitative. It can, nevertheless, be made more transparent, systematic, and logical, and less subjective. Based on human health epidemiological criteria we develop an approach that moves from systematic consideration of seven basic questions to assigning a likelihood of involvement of putative agents. The questions are: 1. Is there evidence that the target is or has been exposed to the agent? 2. Is there evidence for correlation between adverse effects in the target and exposure to the agent either in time or in space? 3. Do the measured or predicted environmental concentrations exceed quality criteria for water, sediment or body burden? 4. Have the results from controlled experiments in the field or laboratory led to the same effect? 5. Has removal of the agent led to amelioration of effects in the target? 6. Is there an effect in the target known to be specifically caused by exposure to the agent? 7. Does the proposed causal relationship make sense logically and scientifically? We identify 15 common scenarios of answers to the questions and illustrate the approach by reference to three real-world case studies (decline in benthos in a tropical marine bay, decline in fisheries in a temperate sea, decline in marine mollusc populations). The primary challenge in retrospective risk assessment is to make best use of the available evidence to develop rational management strategies and/or guide additional analyses to gain further evidence about likely agents as causes of observed harm.