A new calcichordate from the Ordovician of Bohemia and its anatomy, adaptations and relationships

The paper describes a new member of a group of Lower Palaeozoic marine fossils which partly bridge the gap between echinoderms and chordates. Evidence suggests that this group included the ancestors of the vertebrates. Its members are traditionally regarded as primitive echinoderms, but are better seen as primitive chordates with echinoderm affinities. They form a basal subphylum of chordates-the Calcichordata Jefferies 1967. The Calcichordata, in accordance with an early suggestion by Gislén, are probably ancestral to all living chordates. The new calcichordate is named Reticulocarpos hanusi gen et sp. nov. It comes from the Lower Ordovician ?árka Formation (Llanvirn) of ?árka near Prague, Czechoslovakia and is placed in the family Amygdalothecidae Ubaghs 1970. It is important because of its position in the Calcichordata. This group is divided into two very different orders–the Cornuta and the Mitrata. The Cornuta are the more primitive order and gave rise to the Mitrata, which had the structure of giant, calcite-plated tunicate tadpoles. Many features show that the new species is a very advanced cornute, closely related to the stock that gave rise to the mitrates. For this reason it is important in the general history of the chordates, since some primitive mitrate was probably the latest common ancestor of the living chordate subphyla i.e. of tunicates, of amphioxus and its allies and of the vertebrates. Being a mitrate-like cornute, the new species allows the cornutes and mitrates to be compared more confidently than before. Four results are especially important. Firstly it is likely that the stem (=tail) of mitrates is equivalent only to the anterior part of the stem of cornutes. This is significant, because traditional views as to which was the upper surface in mitrates have been based on stem homologies now seen as false. Secondly Reticulocarpos hanusi is adapted to stay up on very soft mud, using only the strength of the mud for support. The mitrates, on the other hand, supported themselves on soft mud by a much more reliable method resembling buoyancy. Thirdly, the new form had paired transpharyngeal eyes which are otherwise known only in mitrates, and which are the earliest type of paired eyes in chordates. Fourthly, it becomes possible to homologize the thecal plates of cornutes with those of mitrates. Reticulocarpos hanusi represents an important phase in chordate evolution dominated by the necessity of staying up on mud by a very precarious method. During this phase many pre-adaptations for swimming were acquired. Primitive mitrates, descended from a very similar form, were probably the first chordates that could swim.     

A cladistic analysis of the anomalocystitid mitrates

A cladistic analysis of the anomalocystitid mitrates is presented. A neutral terminology for the anomalocystitid skeleton is proposed, independent of the zoological interpretation of the fossils as echinoderms or as craniates. The anomalocystitid monophyly is supported by parsimony, although the instability of several basal taxa makes it difficult to ascertain the sequence in which characters were acquired or modified in the transition from the mi-trocystitids to the anomalocystitids. The genus Barrandeocarpus falls outside the anomalocystitids as traditionally defined in the literature, and is either polyphyletic or monophyletic. Diamphidiocystis drepanon is either a basal anomalocystitid or the sister taxon to the group ( Enoploura popei + Allanicytidiidae). Ateleocystites guttenbergensis is placed either at the base of the anomalocystitids or as the sister taxon to a group including mainly boreal forms, the only non-boreal members being the South African Bokkeveldia oosthuizeni and the Australian Victoriacystis wilkinsi.     

In defence of the calcichordates

The cornutes and mitrates, collectively known as stylophorans or calcichordates, are the most controversial members of the traditional group of the 'carpoid echinoderms'. In a recent review, Philip has rejected Ubaghs' interpretation of them as aberrant echinoderms with a single feeding arm, has also rejected my own interpretation of diem as primitive chordates, and has made some tentative proposals of his own. The present paper answers Philip's criticisms of the calcichordate interpretation and discusses his own proposals and his comments on Ubaghs' views.     

Morphometric analysis of Tremadocian (earliest Ordovician) kirkocystid mitrates (Echinodermata, Stylophora) from the Taebaeksan Basin, Korea

Abundant isolated remains of stylophoran echinoderms (cornutes and mitrates) are reported for the first time in the late Tremadocian (Asaphellus Zone) Tumugol Formation of Korea. Mitrate remains include numerous adorals of Kirkocystidae. Several new important anatomical features have been observed on these adorals, as an internal calcitic layer that is associated to s₂ and possibly also to the palmar complex. This observation suggests that the palmar complex would be present not only in mitrocystitid mitrates, but also in peltocystitids. For the first time, several morphometric analyses have been undertaken based on isolated kirkocystid adorals, so as to explore the morphological diversity displayed by Korean adorals, but also in order to compare their morphology with that of other Gondwanan kirkocystids. Morphometric analyses indicate the occurrence of two contrasted morphologies within Korean adorals (morphotypes A and B), and of three distinct morphologies within European and North African forms (“Anatifopsis”, “Balanocystites”, and “escandei” morphotypes). Comparison of Korean adorals with those from Europe and North Africa shows that: (1) morphotypes B and “Anatifopsis” are equivalent; consequently, the two Korean specimens referred to morphotype B are assigned to the genus Anatifopsis; (2) morphology of most Korean adorals, which belong to morphotype A, is clearly distinct from that of all other described kirkocystids from Europe and North Africa. The small size, juvenile morphology, and great morphological variability observed in the morphotype A of the Korean adorals are suggestive of possible heterochronic processes (peramorphosis).     

A new stem-group chordate (Cornuta) from the Llandeilo of Czechoslovakia and the cornutemitrate transition

A new stem chordate, Prokopiytis mergli, from the Middle Ordovician (Llandeilo) of Bohemia, Czechoslovakia is reconstructed and described. It proves to be the most crownward cornute yet known, sharing with the mitrates (primitive crown chordates) a number of derived features unknown in other cornutes. Such features include: the position of the gonopore-anus, the absence of major dorsal plates from the fore tail and the expansion of the marginal plates of the head onto the dorsal surface. Some other characteristics of P. mergli are a fore tail composed of only three segments and an elongate head. Only three hind-tail ossicles are known. The elongate head and small number of fore-tail segments are autapomorphies of P. mergli. The locomotory cycle is reconstructed and it is concluded that P. mergli moved rearwards, pulled largely by its mid and hind tail. The calcichordate theory is defended and the orientation of the mitrates considered. P. mergli reinforces the view that the convex surface of the mitrates was ventral in life. The origin of the atrial chambers of mitrates is discussed and a new homology proposed between the anterior ventral fore-tail plates of cornutes and what were formerly called plates g and j of mitrates. Nový chordát z kmenové skupiny/stem-group/Cornuta zeského Ilandeila, pechod mezi skupinami Cornuta a Mitrata. V práci je popsán a rekonstruován nový zástupce kmene chordátu Prokopicystis mergli gen. et sp. n., z eského llandeila/eskoslovensko/. Jde o dosud známého nejvýe organizovaného kornuta, vykazukícíhoadu znaku shodných s chordáty mitrátníimi a zcela neznámýc u ostatních pedstavitelå skupiny Cornuta. Tyto znaky zahrnují: pozici gonopor-análníiho otvoru, nepítomnost hlavních dorzálních desek v proximálníásti ocasu a expanzi marginálníc desek hlav na dorzální stranu. K dalím charakteristickým znakåum druhu P. mergli patí protáhlá hlava a proximálníást ocasu tvoená jen temi segmenty. V distálníásti ocasu jsou rovn známy jen 3 destiky. Protáhá halva a maly pocet segmentåu proximálníásti ocasu jsou u. P. mergli autapomorfiemi. V práci je také rekonstruován pohybový cyklus ivoicha se závrem, e P. mergli se pohyboval dozadu, pozvolným tahem stední a zadníáSTI OCASU> Je zde hájena tzv. kalcichordátová teorie a diskutována orientace mitrátåu. VyAsledky studia podporují domnnku, e skupiny Mitrata byla za ivota konvexní strana jejich theky stranou ventrální. Je diskutován påuvod atriálnich koma?rek skupiny Mitrata. Souasn jsou pova ovány pední ventrálni desek pedníásti za homologicke s desek díve oznaovanými jako g a j u mitr     

Functional Morphology of Stylophoran Echinoderms

The life orientation and mode of life of stylophorans are a subject of much ongoing debate. Examination of the ornamentation occurring both on the arm and theca in several cornutes and mitrates strongly supports the view that the life orientation was similar in all stylophorans and was ‘flat‐surface down’. The presence of an asymmetrical ornamentation adapted to hinder, or minimize, back slippage of the organism in all stylophorans gives strong support to their interpretation as mostly sessile organisms, feeding with the arm facing the current and the theca downstream. The examination of a wide array of thecal morphologies and sculpture patterns displayed by the various groups of cornutes and mitrates allows the identification of three main modes of life in stylophorans: (1) an epibenthic mode of life, with the theca as main anchor to the substrate (e.g. asymmetrical cornutes, Diamphidiocystis); (2) an epibenthic mode of life, with the arm as main anchor to the sediment (e.g. symmetrical cornutes, Peltocystis, primitive Mitrocystitida, some Kirkocystidae); (3) an infaunal mode of life, with the theca buried in a slightly inclined attitude (e.g. some Kirkocystidae, Mitrocystitida with cuesta‐shaped ribs). The partially buried mode of life of Lagynocystis is intermediate between 2 and 3.     

ICHNOLOGICAL INSIGHTS INTO MITRATE PALAEOBIOLOGY

Abstract:  Mitrates are a controversial group of extinct deuterostomes; there is little agreement over their affinities, functional morphology or even the orientation of their upper and lower surfaces. Four slabs of slate from the Lower Devonian Hunsrück Slate (Bundenbach, Germany) are here described, showing trace fossils ( Vadichnites transversus igen. et isp. nov.) associated with the mitrate Rhenocystis latipedunculata . These new findings clearly demonstrate that the mitrate appendage was used in locomotion and that this movement took place appendage-first. Such a functional interpretation suggests that mitrates were oriented with the flat body surface upwards in life and argues against a phylogenetic position in the echinoderm crown-group.     

A cladistic analysis of the cornutes (stem chordates)

At the root of the calcichordate controversy is the problem of recognizing homologous similarity. Only when a criterion or set of criteria for hypothesizing homologies is established can the calcichordate theory be tested against its main rival—the Stylophoran theory—by applying the principle of parsimony. The criterion of topological similarity is applied to a three-laxon problem involving a mitrate, the crown-group Echinodermata and the crown-group Chordata. The mitrate shares more features with extant chordates than with extant echinoderms and the calcichordate theory is supported by a simple parsimony analysis. In a cladistic analysis of the cornutes, four monophyletic families are recognized (Cothurnocystidae, Scotiaecystidae, Phyllocystidae and Hanusiidae) and their interrelationships resolved using Hennig86 and the successive-weighting procedure of Farris. Because the known fossil record of cornutes and mitrates is very poor, the correlation between the cladogram produced for cornutes and their order of appearance in the geological record is weak. All of the cornute families must have originated in the Lower Cambrian at the latest.     

Brief review of the stylophoran debate

The "calcichordate" theory interprets an extinct group of calcite-plated invertebrates, the stylophorans, as chordates. In this theory, cornute stylophorans are interpreted as stem chordates, whereas mitrate stylophorans are primitive members of the acraniates, tunicates, and craniates. However, this theory discounts major synapomorphies between cornutes and mitrates. These groups constitute a natural, monophyletic group which is here argued to lie within the echinoderm radiation. The "calcichordate" theory is, therefore, rejected because it relies on assumption-driven hypotheses of character transformation which are supported by ambiguous, poor, or missing fossil evidence. Stylophorans may lie at the base of the echinoderm clade and primitively lack pentameral symmetry, therefore casting light on the near-ancestral body organization of the phylum.     

An atypical fauna in the Lower Devonian Hunsrück Slate of Germany

The Hunsrück Slate is a world renowned conservation lagerstätte, stretching SW-NE in a narrow band between the villages of Bundenbach and Gemünden, Hunsrück region, Germany. A great variety of complete Lower Devonian fossils is preserved with their soft parts pyritised due to rapid burial by sediment. The fossils of the Hunsrück Slate outside the narrow band are scarcely known. They represent the normal Situation: quiet low energy Sedimentation. This paper describes this overall “Rhenish” neritic fauna under the heading “atypical”, in contrast to the famous fossils of the conservation lagerstätte. The fauna described here lacks starfishes, mitrates and chelicerates. The paper begins with an overview of the recent relevant literature (stratigraphic position of the Hunsrück Slate, palaeoecology). The slate fossils were collected in two quarries WNW and NE of Bundenbach (Lingenbach and Karschheck, respectively) and most closely resemble that of the Wisper Valley in the Taunus region. Their geologic age is Lower Devonian, early Emsian, Ulmen Substage. Special interest is given to Community structures, rugose corals, bivalves, gastropods, trilobites, conulariids, brachiopods and crinoids. In the systematic part, the crinoidOrthocrinus simplex is redescribed. Also, two new species are introduced: the rugose coralVolgerophyllum karschheckensis n. gen., n. sp., and the crinoidAcanthocrinus spinosus n. sp.     

A phylogenetic test of the calcichordate scenario

The calcichordate scenario of Jefferies and colleagues purports to explain the origin and early evolution of the phyla Echinodermata and Chordata. Calcichordate proponents have argued that echinoderms are the sister group of the chordates and urochordates are the sister group of the craniates. These phylogenetic hypotheses, which differ from the traditional groupings, are derived primarily from morphological interpretations of carpoids (solutes, cornutes, and mitrates), an enigmatic fossil group usually held to be primitive stem-group echinoderms. Although the scenario has received only limited support, it has yet to be falsified. The difficulty with falsifying the calcichordate scenario is proving that the morphological interpretations, for example, that carpoids possessed notochords, dorsal hollow nerve cords, and other typical chordate or craniate characters, are incorrect. Here, rather than argue over the interpretation of fossils, the phylogenetic hypotheses embedded within the scenario are tested. It is found that the calcichordate scenario fails such a test, even if both the Recent and fossils forms are coded according to the calcichordate scenario. It is argued that: (1) the erection of scenarios must follow the construction of a cladogram; and (2) fossils are unable to dictate the relationships among phyla. □ Calcichordate scenario, Carpoidea, Deuterostomia, Echinodermata, Chordata, phylogeny, cladistics.     

Connections between the cristae and the surface of rat heart muscle mitochondria

Contrary to the generally accepted rule that there are only two fracture faces associated with a membrane, the analysis of double replicas at rat heart muscle mitochondria revealed three pairs of complementary replicas with one face in each pair exposing the outer surface membrane. The replicas must then expose the surfaces of the outer surface membrane and in two of the pairs the fracture had passed between the two surface membranes in two alternative ways, either clearly between the two membranes or the fracture deviated into and through the inner surface membrane at regularly spaced intervals. This deviation reveals that at these sites the connection between the two surface membranes is particularly firm. The analysis led to the conclusion that these sites correspond to those where the stalk-like connections extending from the cristae are connected to the inner surface membrane. This way proteinaceous pathways connect the cristae to the surface of the mitochondria.     

Two overlapping SOS-boxes in ColE operons are responsible for the viability of cells harboring the Col plasmid

In this study, oligonucleotide-directed site-specific mutagenesis was used to change the consensus sequences of the LexA binding motifs in either one of the two SOS-boxes of the ColE7 operon. The results indicated that both mutants produced larger amounts of colicin than cells harboring the wild-type ColE7 plasmid. This finding would imply that two biologically functional SOS boxes exist in the ColE7 operon. In the non-induced state, no lysis of cells harboring wild-type plasmids occurred at 37°C, whereas, cells harboring recombinant plasmids containing either one of the mutated SOS boxes underwent lysis within 100 min under the same conditions. This result indicated that adaptation of two SOS boxes of the ColE operon would obviously tightly control the expression of ColE operons. In such a way that it may prevent excessive expression of the lysis (cel) gene, thus safeguard the host cells from being lysed in ordinary living conditions.     

Regional Context in the Alignment of Biological Sequence Pairs

Sequence divergence derives from either point substitution or indel (insertion or deletion) processes. We investigated the rates of these two processes both in protein and non-protein coding DNA. We aligned sequence pairs using two pair-hidden Markov models (PHMMs) conjoined by one silent state. The two PHMMs had their own set of parameters to model rates in their respective regions. The aim was to test the hypothesis that the indel mutation rate mimics the point mutation rate. That is, indels are found less often in conserved regions (slow point substitution rate) and more often in non-conserved regions (fast point substitution rate). Both polypeptides and rRNA molecules in our data exhibited a clear distinction between slow and fast rates of the two processes. These two rates served as surrogates to conserved and non-conserved secondary structure components, respectively. With polypeptides we found both the fast indel rate and the fast replacement rate were co-located with hydrophilic residues. We also found that the average concordance, of our alignments with corresponding curated alignments, improves markedly when the model allows either of the two fast rates to colocate with hydrophilic residues. With rRNA molecules, our model did not detect colocation between the fast indel rate and the fast substitution rate. Nevertheless, coupling the indel rates with the point substitution rates across the two regions markedly increased model fit. This result suggests that rRNA pairwise alignments should be modeled after allowing for the two processes to vary simultaneously and independently in the two regions.     

Three steroidogenic factor-1 binding elements are required for constitutive and cAMP-regulated expression of the human adrenocorticotropin receptor gene

In the present study, we characterized two new SF-1 binding sites, SF-209 and SF-98, in the promoter of the human ACTH receptor (hACTH-R) gene. Both sites, together with the previously described SF-35 site, are required for full constitutive activity of this gene. This was demonstrated by the use of constructs containing part of the promoter upstream of the luciferase gene and carrying mutation in one of these sites, to transiently transfect H295R cells. Mutations of either SF-35, SF-98, or SF-209 induced a decrease of luciferase activity. This effect was amplified when two or three elements were mutated together in the same construct. Only SF-35 and SF-98 seem to play a major role in the cAMP-induced regulation of the hACTH-R gene, since mutation of either one of these sites reduced the forskolin induction of luciferase activity by 50%. When both elements were mutated, no stimulation was obtained over the control. This indicates that SF-1 protein must bind to both sites for the cAMP response.     

Differences between the manganese- and the iron-containing superoxide dismutases of Escherichia coli detected through sedimentation equilibrium, hydrodynamic, and spectroscopic studies

The genome of Escherichia coli codes for two superoxide dismutases that may contain either iron (FeSOD) or manganese (MnSOD) at the active site. The crystal structures of MnSODs from two bacterial sources (but not E. coli) have been completed, and structural comparisons with the crystal structure of the FeSOD from either E. coli or Pseudomonas ovalis have been made. Despite the low degree (less than 50%) of sequence homology between the E. coli enzymes, the two proteins are suggested to be structurally homologous. Nonetheless, these enzymes exhibit absolute metal cofactor specificity in conferring enzymatic activity to the inactive apoenzyme. This observation is surprising considering the identity of the active site ligands and the similarities in their geometry and surrounding environment. Using analytical ultracentrifugation, we have determined that the solution properties of these two proteins are different. Thus dialysis of FeSOD but not of MnSOD against phosphate buffer in the presence or absence of EDTA caused dissociation of the homodimer. This dissociation appeared to be related to the loss of iron from native FeSOD. Thus, apoFeSOD but not apoMnSOD existed predominantly as a monomer at protein concentrations below 150 micrograms/mL. ApoMnSOD showed no evidence for dissociation under these conditions. Fluorescence data suggest that the tryptophan environments for the two enzymes are also different. The results of these physical measurements lead us to propose that subtle differences, perhaps at the subunit contact faces, exist in the structures of these crystallographically similar proteins.     

A new weevil genus of the tribe Metrioxenini (Coleoptera: Belidae) in Eocene Baltic amber

A new genus, Succinometrioxena n. gen., and a new species, S. poinari n. sp. (Metrioxenini: Oxycoryninae), are described from Baltic amber. This new genus resembles the recent genus Wallacexena Legalov, 2009 but differs from it by the frons with horn-like tubercles on either side, the absence of a middle pronotal carina, teeth on the side of the pronotum, the anterior margin of the pronotum lacking teeth and two long carinae on the elytra. From the fossil genus Paltorhynchus Scudder, 1893 the present fossil differs by possessing a frons with horn-like tubercles on either side, the absence of a middle pronotal carina, teeth on the sides of the pronotum, two long carinae on the elytra and short temples. From the fossil genus Archimetrioxena Voss, 1953, the new genus differs by the frons with horn-like tubercles on either side, the absence of the two truncated elytral carinae, the sides of the pronotum with teeth, short temples and a larger body size.     

The Effects of Upright and Slumped Postures on the Recall of Positive and Negative Thoughts

This study assessed whether it was easier to generate positive and negative thoughts in either an upright or slumped position. Twenty-four participants, who reported no clinical depression or anxiety, completed the Tellegen absorption questionnaire and a self-assessment of imagery ability. Surface electromyography (sEMG) of zygomaticus major, heart rate, and respiratory rate were assessed across four 1-min counterbalanced conditions of either upright or slumped posture and either positive or negative thought generation. Posttrial checks of compliance were completed. At the end of the study, participants rated which thought was easiest to generate in the two postures. Significantly more participants (22), or 92%, indicated it was easiest to generate positive thoughts in the upright position. ANOVA of sEMG activity significantly distinguished positive and negative thoughts in both positions. Significant correlation coefficients were observed between scores on the Tellegen scale of absorption and the ability to generate thoughts quickly and between self-perceptions of imagery ability with the maintenance of thoughts across time. This study supports the finding that positive thoughts are more easily recalled in the upright posture.     

A new two-dimensional gel electrophoresis system for the analysis of complex protein mixtures: Application to the ribosome of E. coli

A new method for two-dimensional polyacrylamide gel electrophoresis of proteins is described. The method, illustrated here by its application for the analysis of ribosomal proteins of E. coli, has a high resolving power. The proteins S15 and S16 can be resolved either following alkylation or under reducing conditions. This was not possible with urea gel systems previously employed. The method should be advantageous in the identification of the components of dimers formed with the reagent methyl 4-mercaptobutyrimidate. An additional advantage of the new method is that both dimensions are run at an acidic pH. For ribosomal proteins it is therefore unnecessary to either polymerize the protein sample in the middle of the first dimension disc gel or to electrophorese two samples with opposite polarity.