Is Giardia a living fossil?

Despite enormous efforts, the patterns of the rise of eukaryotic life on Earth are not clearly defined. The ability of eukaryotes to produce energy using oxygen and sugars was a key factor in advancing life on Earth towards complex multicellular organisms. However, this was not the only way to produce energy and survive. Mitochondria probably appeared soon after the oxygen increase in the Earth's atmosphere but many microaerophilic protists require little or no oxygen to survive. New ultrastructural, biochemical and molecular phylogeny data about structures and processes involved in the generation of energy by currently known protists have forced the revision of understanding of the "tree of life".     

Some proteins keep “living fossil” pre-sequence

The sequences of hydrophobic segments of exported bacterial proteins, some serine proteinases and all known plastocyanins are examined in order to find out subsequences differing in amino acid composition and primary structure regularities. It is established that the extension in protein precursor, cleaved by a proteolysis (so-called P-sequence), demonstrates a higher share of usual amino acids (Thr, Pro, Ala, Ser, Arg, Gly, Leu, Val, Glu, Asp) and more clearly expressed periodicity compared to the mature protein (M-sequence). The obtained results confirm the conception of primitive proteins comprising a small number of amino acids realized a preferable bonding (between identical and very similar in structure-function-evolution sense).     

Gaps in fossil teeth: Saltations or sampling errors?

All evolutionists accept that there are gaps in the fossil record. To some, gaps are data: they mark sudden transitions, unlikely to be preserved, between one species and its descendants that have arisen by a brief genetic revolution within an otherwise stable lineage. However, recent studies of sediment gain and loss show that few fossil beds can be complete enough to give details of the process of speciation, so that most gaps are gaps, and nothing more. Differences in the perception of time and sampling completeness mean that paleontologists and geneticists see the rate and pattern of evolution in different ways. Just how misleading each view may be is seen by analysing the laws of life governing change in living populations using the limitations intrinsic to studies of past times; and by a new insight into the details of species formation now emerging from some remarkably complete primate fossil sequences.     

Bacillus DNA in fossil bees: an ancient symbiosis?

We report here the isolation of DNA from abdominal tissue of four extinct stingless bees (Proplebeia dominicana) in Dominican amber, PCR amplification of a 546-bp fragment of the 16S rRNA gene from Bacillus spp., and their corresponding nucleotide sequences. These sequences were used in basic local alignment search tool searches of nonredundant nucleic acid data bases, and the highest scores were obtained with 16S rRNA sequences from Bacillus spp. Phylogenetic inference analysis by the maximum-likelihood method revealed close phylogenetic relationships of the four presumed ancient Bacillus sequences with Bacillus pumilus, B. firmus, B. subtilis, and B. circulans. These four extant Bacillus spp. are commonly isolated from abdominal tissue of stingless bees. The close phylogenetic association of the extracted DNA sequences with these bee colonizers suggests that a similar bee-Bacillus association existed in the extinct species P. dominicana.     

Sterol composition of the “living fossil” crinoid Gymnocrinus richeri

• 1.1. The composition of sterol mixture from the “living fossil” crinoid Gymnocrinus richeri collected off Nouméa (New Caledonia) was investigated.
• 2.2. The free 3β-OH sterol mixture was found to contain 14 components, Δ⁵ and ring saturated stanols, identified by GC-MS.
• 3.3. Cholest-4-en-3-one, cholesta-1, 4-dien-3-one (this latter firstly isolated from a marine source), 5α-8α-epidioxy sterols, and 5α-ergosta-7,22-diene-3β,5,6β-triol were also present, their characterization being accomplished by EI-MS and ¹H-NMR. The methanol extract also contained sterol sulphates, which were identified by GC-MS after solvolysis to remove the sulphate group.

     

Symbiophagy and biomineralization in the “living fossil” Astrosclera willeyana

Representatives of all major metazoan lineages form biominerals. The molecular mechanisms that underlie this widespread and evolutionarily ancient ability are gradually being revealed for some lineages. However, until a wider range of metazoan biomineralization strategies are understood, the true diversity, and therefore the evolutionary origins of this process, will remain unknown. We have previously shown that the coralline demosponge, Astrosclera willeyana, in some way employs its endobiotic bacterial community to form its highly calcified skeleton. Here, using in situ hybridization and immunohistochemistry, we show that an ortholog of ATG8 (most likely a GABARAPL2/GATE-16 ortholog) is expressed in cells that construct the individual skeletal elements of the sponge. In TEM sections sponge cells can be observed to contain extensive populations of bacteria, and frequently possesses double-membrane structures which we interpret to be autophagosomes. In combination with our previous work, these findings support the hypothesis that the host sponge actively degrades a proportion of its bacterial community using an autophagy pathway, and uses the prokaryotic organic remains as a framework upon which calcification of the sponge skeleton is initiated.     

Symbiophagy and biomineralization in the “living fossil” Astrosclera willeyana

Representatives of all major metazoan lineages form biominerals. The molecular mechanisms that underlie this widespread and evolutionarily ancient ability are gradually being revealed for some lineages. However, until a wider range of metazoan biomineralization strategies are understood, the true diversity, and therefore the evolutionary origins of this process, will remain unknown. We have previously shown that the coralline demosponge, Astrosclera willeyana, in some way employs its endobiotic bacterial community to form its highly calcified skeleton. Here, using in situ hybridization and immunohistochemistry, we show that an ortholog of ATG8 (most likely a GABARAPL2/GATE-16 ortholog) is expressed in cells that construct the individual skeletal elements of the sponge. In TEM sections sponge cells can be observed to contain extensive populations of bacteria, and frequently possesses double-membrane structures which we interpret to be autophagosomes. In combination with our previous work, these findings support the hypothesis that the host sponge actively degrades a proportion of its bacterial community using an autophagy pathway, and uses the prokaryotic organic remains as a framework upon which calcification of the sponge skeleton is initiated.     

Is the bacterial ferrous iron transporter FeoB a living fossil?

The cytoplasmic membrane protein FeoB of Escherichia coli, Helicobacter pylori, Legionella pneumophila and Synechocystis sp. strain PCC 6803 is necessary for Fe(2+) uptake. The C-terminal part of FeoB is predicted to contain 8-12 membrane-spanning helices. The N-terminal domain shows much similarity to eukaryotic and prokaryotic G proteins and, indeed, GTPase activity is necessary for Fe(2+) transport. Four of the five characteristic conserved G protein motifs have been identified in FeoB proteins. Whether FeoB is involved directly, via its Me(2+) binding site, or indirectly in Fe(2+) transport, remains to be investigated.     

Microbial carbonate crusts-a key to the environmental analysis of fossil spongiolites?

Summary Morphological and geochemical comparisons between modern cryptic microbialites from Lizard Island/Great Barrier Reef and fossil counterparts in the Upper Jurassic (Southern Germany, Dobrogea/Romania) and late Lower Cretaceous (Aptian/Albian from Cantabria/Spain) spongiolitic environments show that there are common factors controlling the crust formations mostly independent of light despite of diverging (paleo-) oceanographic positions as well as relationships of competitors. Factors such as increased alkalinity, oligotrophy, and reduced allochthonous deposition are of major importance. Thrombolitic microbialites are interpreted as biologically induced and therefore calcified in isotopic equilibrium with the surrounding sea water. Corresponding with shallowing upward cycles, microbial mats which produce stromatolitic peloidal crusts become more important. Different biomarkers are introduced for the first time extracted and analyzed from spongiolitic limestones of Lower Kimmeridgian age from Southern Germany.     

The fossil family Ameghinornithidae (Mourer-Chauviré 1981): a short synopsis

A short synopsis of the taxa included in Ameghinornithidae is presented. The rather poor fossil record suggests that these birds were (nearly?) flightless, similar to small phorusrhacids.     

Is Palaeospondylus gunni a fossil larval lungfish? Insights from Neoceratodus forsteri development

The enigmatic Devonian fossil Palaeospondylus gunni was identified as a larval form, metamorphosing into the lungfish Dipterus valenciennesi. Morphological features used to identify P. gunni as a larval lungfish include enlarged cranial ribs, rudimentary limb girdles, and absence of teeth. However, this combination of features does not characterize the extant lungfish Neoceratodus forsteri, even at very young stages, nor early stages of Devonian and younger fossil lungfish. Absence of teeth is problematic because early ontogenetic stages of fossil and living lungfish possess full dentitions including marginal teeth. Also problematic are cranial ribs as a defining character of lungfish, as these also occur in certain actinopterygians.It is argued that Neoceratodus is an obligate neotene (reproductively mature larva), with the implication that metamorphosis was a feature of the ontogeny of early lungfish. Pedomorphic characters have been recognized in Neoceratodus and other post-Devonian lungfish, including large cells and correspondingly large genome size; these latter characters correlate with neoteny in salamanders. Small cells preserved in fossil bone suggest that Devonian lungfish had a smaller genome than post-Devonian lungfish, implying that they were not neotenic. As fossil lungfish cell sizes (and genomes) increased in the late Paleozoic, the diversity of lungfish morphologies decreased, so that taxa like Sagenodus and Conchopoma show morphological similarity to Neoceratodus, marking a point in phylogeny at which metamorphosis was potentially lost. Since ancestral larval characters are retained in neotenic adults, we predict that Devonian larvae should resemble these post-Devonian taxa, a prediction which Palaeospondylus does not fulfill.     

What can we learn about ecology and evolution from the fossil record?

The increased application of abundance data embedded within a more detailed and precise environmental context is enabling paleontologists to explore more rigorously the dynamics and underlying processes of ecological and evolutionary change in deep time. Several recent findings are of special theoretical interest. Community membership is commonly more stable and persistent than expected by chance, even in the face of the extreme environmental changes of the Ice Ages, and major evolutionary novelties commonly lie dormant for tens of millions of years before the ecological explosions of the clades that possess them. As we discuss here, questions such as these cannot be adequately addressed without the use of the fossil record.     

Alfred Nicholson Leeds and the first fossil egg attributed to a ‘saurian’

Discovered by the nineteenth century collector Alfred Nicholson Leeds, the first object to be described (1898) as a fossil reptile egg is a unique find from the Oxford Clay near Peterborough. It also comes from one of a very small number of Jurassic localities worldwide that can claim to have yielded a fossil egg. Given its historical and contemporary significance, this object is reassessed in the light of increased understanding of such objects. Data from scanning electron microscopy, computerised tomography, synchrotron imaging, X-ray diffraction and petrographic thin sectioning prove inconclusive. However, the presence of apparent external openings resembling angusticanaliculate pores – a pore type common only to certain types of dinosaur eggshell – in both size and sparseness of distribution prevents its summary dismissal as not being a dinosaurian egg.     

Anion inhibition studies of an α-carbonic anhydrase from the living fossil Astrosclera willeyana

An α-carbonic anhydrase (CA, EC 4.2.1.1) isolated from the living fossil sponge Astrosclera willeyana, Astrosclerin, was investigated for its inhibition profile with simple inorganic anions, complex anions and other small molecules known to interact with these zinc enzymes. Astrosclerin is a catalytically highly efficient enzyme, and is inhibited in the low micromolar range by sulfamide, sulfamic acid, phenylboronic acid and phenylarsonic acid, and in the submillimolar range by a variety of anions including fluoride, chloride, cyanate, thiocyanate, cyanide, hydrogen sulfide, bisulfate, stannate, perosmate, divanadate, perrhenate, perruthenate, selenocyanide, trithiocarbonate, diethyldithiocarbamate and iminodisulfonate. Less efficient Astrosclerin inhibitors were sulfate, bromide, iodide, azide, bicarbonate, carbonate, tetraborate and perchlorate (K(I)s of 5.11-30.6mM) whereas tetrafluoroborate was not at all inhibitory. Because Astrosclerin is involved in calcification processes in vivo, its anion inhibition profile may be important for future studies designed to shed light on the physiologic functions of α-CAs in marine organisms.     

An enigmatic molluscan fossil from the Devonian of Germany: scaphopod or cephalopod?

The taxonomic position of a fossil recently found in Givetian strata of the Eifel Mountains, Germany, is discussed. It is a member of the Mollusca, but it is uncertain if it should be assigned to the Cephalopoda or the Scaphopoda. Both possibilities can be supported by the preserved morphology of the specimen. Without additional material the question of higher taxonomic assignment remains unsolved.     

Estimating stature in fossil hominids: which regression model and reference sample to use?

coResearchers have long appreciated the significant relationship between body size and an animal's overall adaptive strategy and life history. However, much more emphasis has been placed on interpreting body size than on the actual calculation of it. One measure of size that is especially important for human evolutionary studies is stature. Despite a long history of investigation, stature estimation remains plagued by two methodological problems: (1) the choice of the statistical estimator, and (2) the choice of the reference population from which to derive the parameters.This work addresses both of these problems in estimating stature for fossil hominids, with special reference to A.L. 288-1 (Australopithecus afarensis) and WT 15000 (Homo erectus). Three reference samples of known stature with maximum humerus and femur lengths are used in this study: a large (n=2209) human sample from North America, a smaller sample of modern human pygmies (n=19) from Africa, and a sample of wild-collected African great apes (n=85). Five regression techniques are used to estimate stature in the fossil hominids using both univariate and multivariate parameters derived from the reference samples: classical calibration, inverse calibration, major axis, reduced major axis and the zero-intercept ratio model. We also explore a new diagnostic to test extrapolation and allometric differences with multivariate data, and we calculate 95% confidence intervals to examine the range of variation in estimates for A.L. 288-1, WT 15000 and the new Bouri hominid (contemporary with [corrected] Australopithecus garhi). Results frequently vary depending on whether the data are univariate or multivariate. Unique limb proportions and fragmented remains complicate the choice of estimator. We are usually left in the end with the classical calibrator as the best choice. It is the maximum likelihood estimator that performs best overall, especially in scenarios where extrapolation occurs away from the mean of the reference sample. The new diagnostic appears to be a quick and efficient way to determine at the outset whether extrapolation exists in size and/or shape of the long bones between the reference sample and the target specimen.     

The fossil record of Cunoniaceae: new evidence from Late Cretaceous wood of Antarctica?

Fossil angiosperm wood from Upper Cretaceous sediments of Livingston Island and James Ross Island in the northern Antarctic Peninsula region is identified as having the combination of anatomical characters most similar to modern Cunoniaceae. The material is characterised by predominantly solitary vessels, opposite to scalariform intervessel pitting, scalariform perforation plates, heterocellular multiseriate and homocellular uniseriate rays, diffuse axial parenchyma. Anatomically, the specimens conform most closely to the fossil organ genus Weinmannioxylon Petriella which has been placed within the Cunoniaceae. The presence of Weinmannioxylon in Late Cretaceous sediments suggests that taxa within or stem taxa to the Cunoniaceae might have been a notable component of the forest vegetation that covered the Antarctic Peninsula during the Late Mesozoic and may therefore represent the earliest record of this family.