Subocclusal dental morphology of sahelanthropus tchadensis and the evolution of teeth in hominins

The evolution of the teeth in hominins is characterized by, among other characters, major changes in root morphology. However, little is known of the evolution from a plesiomorphic, ape‐like root morphology to the crown hominin morphology. Here we present a study of the root morphology of the Miocene Chadian hominin Sahelanthropus tchadensis and its comparison to other hominins. The morphology of the whole lower dentition (I₁–M₃) was investigated and described. The comparison with the species Ardipithecus kaddaba and Ardipithecus ramidus indicates a global homogeneity of root morphology in early hominins. This morphology, characterized notably by a reduction of the size and number of the roots of premolars, is a composite between an ape‐like morphology and the later hominin morphology. Trends for root evolution in hominins are proposed, including the transition from a basal hominoid to extant Homo sapiens. This study also illustrates the low association between the evolution of tooth root morphology and the evolution of crowns in hominins. Am J Phys Anthropol 153:116–123, 2014. © 2013 Wiley Periodicals, Inc.     

Wing morphology,winter ecology,and fecundity selection: evidence for sex-dependence in barn swallows (<Emphasis Type="Italic">Hirundo rustica</Emphasis>)

Variation in wing morphology results from the combination of diverse selection pressures. Wing feather morphology within species varies with sex and ontogenetic effects, and also with ecological factors. Yet, the direction of causation for the wing morphology–ecology association remains to be elucidated. Under the ‘ecology-dependence’ hypothesis, wing morphology covaries with ecological conditions, because the latter affect feather molt. Alternatively, the ‘habitat choice’ hypothesis posits that individuals with different wing morphology choose different habitats because of the habitat-dependent advantages of a specific wing morphology. We tested these competing hypotheses in the migratory, aerially insectivorous barn swallow (Hirundo rustica). We quantified wing morphology (isometric size, pointedness, and convexity) on the same individuals during consecutive breeding seasons (i.e., before and after molt in sub-Saharan wintering areas) and located wintering areas using light-level geolocators. Wing pointedness of females but not males during 1 year negatively correlated with vegetation vigor (gauged by the Normalized Difference Vegetation Index; NDVI) in the African area where individuals spent the next winter. Partial least-squares path modelling showed that the association between wing morphology and NDVI was sex-dependent. Conversely, NDVI during wintering did not predict wing morphology in the next breeding season. Because wing morphology can have carry-over effects on subsequent performance, we investigated selection on wing traits and found strong positive fecundity selection on wing size of females. Our results suggest that female barn swallows choose their wintering habitat depending on their wing morphology. In addition, directional fecundity selection operates on females, suggesting sex-dependence of current selection on the flight apparatus.     

The Gegenbaur Transformation: a paradigm change in comparative biology

The leading experts in the development of phylogenetic systematics, Walter Zimmermann and Willi Hennig, formulated their research program in opposition to (neo-) idealistic morphology as expounded by authors such as Wilhelm Troll and Adolf Naef. Idealistic morphology was synonymous with systematic morphology for Naef, who wanted it to be strictly kept separate and independent of phylogenetics. Naef conceded, however, that the natural system researched by systematic morphology is to be causally explained by the theory of descent with modification. Naef went on to compile a dictionary that would regulate the translation of the language of systematic morphology into the language of phylogenetics. The switch from idealistic morphology to phylogenetic morphology is paradigmatically exemplified in the two editions (1859, 1870) of Carl Gegenbaur's Grundzüge der vergleichenden Anatomie. This paper traces the development of phylogenetic systematics from Gegenbaur through the work of Adolf Naef to Walter Zimmermann and Willi Hennig. Hennig added to Naef's systematic morphology the dimension of time, which required an ontological replacement: Naef's natural system, a nested hierarchy of intensionally defined sets subject to the membership relation, was replaced by Hennig's phylogenetic system, an enkaptic hierarchy subject to the part-to-whole relation.     

Evolution of dentition in salamanders: relative roles of phylogeny and diet

Despite being widely regarded as generalist predators, amphibians exhibit a diversity of tooth shapes and dentition patterns, which may indicate the influence of dietary specialization on the evolution of tooth morphology. Very few studies have analysed the relationship between tooth morphology and diet (i.e., prey items) in amphibians, and those existing studies are highly speculative. We investigated the evolution of salamander teeth and the relationship between tooth morphology and diet in a phylogenetically independent fashion. We used a phylogeny of 23 species of salamander representing three families (Ambystomatidae, Plethodontidae, and Salamandridae) to, first, analyse the divergence of tooth morphology and its relationship to phylogeny and, second, to analyse the relationship between tooth morphology and diet diversity. We used electron scanning microscopy and a statistical comparative approach using Spatial Evolutionary and Ecological Analysis (SEEVA) and phylogenetic generalized least‐squares regression in R. Our results indicated significant divergence in tooth morphology at major phylogenetic splits. Moreover, there was a significant, phylogenetically independent relationship between tooth morphology and diet diversity. The relationship between diet and tooth morphology indicates not only a reflection of phylogenetic history, but also a degree of dietary specialization, indicating that evolution in tooth morphology has had an adaptive aspect in relation to salamander diet.     

Foregut morphology and ontogeny of the mud crab Dyspanopeus sayi (Smith, 1869) (Decapoda,Brachyura, Panopeidae)

The morphology of the foregut of the Say's mud crab Dyspanopeus sayi was described in adults and larvae. The ossicle system was illustrated based on a staining method with Alizarin-Red. The gastric teeth and cardio-pyloric valve were dissected and examined using optical and scanning electron microscopy. In the adults, the morphology of ossicles and gastric teeth of D. sayi is very similar to the related species Rhithropanopeus harrisii. The foregut of first zoea (ZI) presented a functional cardio-pyloric valve while the filter press was lacking. The filter press was observed in the pyloric chamber from ZII. The most significant changes in morphology take place after metamorphosis from ZIV to megalopa, including the occurrence of the gastric mill. The organization and morphology of many megalopal foregut ossicles are recognizable in the adult phase, although the morphology of the gastric teeth differs from the morphology of adults. A correlation of gastric mill structures with food preferences and their contribution to the phylogeny are briefly discussed.     

Differences in sperm morphology in foam‐nesting leptodactyline frogs (Anura,Leptodactylidae)

Sperm morphology is diverse among vertebrates and is influenced by the reproductive strategies adopted by species. In anurans, sperm morphology is associated with reproductive modes and mating systems. Here, we describe the sperm morphology of 11 frog species in the genus Leptodactylus and that of Lithodytes lineatus and discuss the relationship between sperm morphology and species' mating systems. We observed two distinct sperm morphotypes among the leptodactyline species, which differed mostly in head morphology. Type I sperm had triangular head, discrete acrosome vesicle with posterior margin not clearly visible; type II sperm had elongated head, clear acrosomal vesicle with posterior margin clearly visible. These sperm types do not seem to be associated with phylogeny; instead, type II sperm was observed in all polyandrous species analysed and in species with evidences of polyandry. Moreover, sperm of all species presented tail with undulating membrane connected to the axial fibre. We suggest that differences in sperm morphology might be associated with sperm competition to what polyandrous species are subjected. However, natural history observations on polyandrous mating in some species presenting type II sperm and phylogenetic comparative studies are need to elucidate the role of mating systems in the evolution of sperm morphology in leptodactylines.     

Morphology-driven downscaling of <Emphasis Type="Italic">Streptomyces lividans</Emphasis> to micro-cultivation

Actinobacteria are prolific producers of secondary metabolites and industrially relevant enzymes. Growth of these mycelial micro-organisms in small culture volumes is challenging due to their complex morphology. Since morphology and production are typically linked, scaling down culture volumes requires better control over morphogenesis. In larger scale platforms, ranging from shake flasks to bioreactors, the hydrodynamics play an important role in shaping the morphology and determining product formation. Here, we report on the effects of agitation on the mycelial morphology of Streptomyces lividans grown in microtitre plates. Our work shows that at the appropriate agitation rates cultures can be scaled down to volumes as small as 100 µl while maintaining the same morphology as seen in larger scale platforms. Using image analysis and principal component analysis we compared the morphologies of the cultures; when agitated at 1400–1600 rpm the mycelial morphology in micro-cultures was similar to that obtained in shake flasks, while product formation was also maintained. Our study shows that the morphology of actinobacteria in micro-cultures can be controlled in a similar manner as in larger scale cultures by carefully controlling the mixing rate. This could facilitate high-throughput screening and upscaling.     

Genetic Determinism vs. Phenotypic Plasticity in Protist Morphology

Untangling the relationships between morphology and phylogeny is key to building a reliable taxonomy, but is especially challenging for protists, where the existence of cryptic or pseudocryptic species makes finding relevant discriminant traits difficult. Here we use Hyalosphenia papilio (a testate amoeba) as a model species to investigate the contribution of phylogeny and phenotypic plasticity in its morphology. We study the response of H. papilio morphology (shape and pores number) to environmental variables in (i) a manipulative experiment with controlled conditions (water level), (ii) an observational study of a within‐site natural ecological gradient (water level), and (iii) an observational study across 37 European peatlands (climate). We showed that H. papilio morphology is correlated to environmental conditions (climate and water depth) as well as geography, while no relationship between morphology and phylogeny was brought to light. The relative contribution of genetic inheritance and phenotypic plasticity in shaping morphology varies depending on the taxonomic group and the trait under consideration. Thus, our data call for a reassessment of taxonomy based on morphology alone. This clearly calls for a substantial increase in taxonomic research on these globally still under‐studied organisms leading to a reassessment of estimates of global microbial eukaryotic diversity.     

Geographic variation in lower pharyngeal jaw morphology in the Shiner Perch <Emphasis Type="Italic">Cymatogaster aggregata</Emphasis> (Embiotocidae,Teleostei)

Correlations of feeding morphology with body morphology reflect ecological variation of a species and the geographic or ontogenetic scales over which it occurs. In this study, evidence was found for geographic variation in lower pharyngeal jaw (LPJ) morphology of Cymatogaster aggregata Gibbons (Embiotocidae, Teleostei) in the Pacific Northwest, U.S.A. Correlations of LPJ morphology with body morphology were more obvious in adulthood than the juvenile stage. Morphological patterns corresponded better with environmental variables and gut contents than geographic proximity, indicating that they were most likely caused by habitat differences. Qualitative common garden experiments indicated the nature and direction of plastic responses, and indicate a likely plastic origin to most naturally observed differences. Recognizing ecological patterns via morphology is an important first step in understanding how and when ecological mechanisms influence the functional role of an organism within its environment.     

Carpal development and morphology in archontan mammals

Carpal morphology and development in bats, colugos, tree shrews, murids, and sciurids were studied in order to homologize carpal elements. Prenatal coalescence of discrete cartilaginous templates with a loss of a center of ossification appears to be the most common method of reducing carpal elements in these mammals. Only bats and colugos showed postnatal ossification between discrete elements as a method of reducing carpal elements. Carpal morphology of tree shrews is more diverse than previously reported. Ptilocercus shows a highly derived carpal morphology that may be related to its relatively greater arboreality. Dendrogale exhibits what is most likely the ancestral tupaiid carpal morphology. Carpal morphologies of Tupaia, Urogale, and Anathana are identical to each other. Carpal morphology differs between megachiropterans and microchiropterans. These differences may be related to different aerodynamic constraints between the suborders. The carpal morphology of microchiropterans is diverse and may reflect different adaptive regimes between microchiropteran families. Carpal morphology of the colugos shows both megachiropteran and microchiropteran characters. The function of these characters in colugos and bats (stabilization of the carpus in dorsiflexion) is proposed to be similar, although the locomotor roles may be quite different between these taxa. J. Morphol. 235:135–155, 1998. © 1998 Wiley-Liss, Inc.     

TRIBUTE: In Goethe's Wake: Marvalee Wake's conceptual contributions to the development and evolution of a science of morphology

Decrying the typological approach in much of the teaching of morphology, from the outset of her career Marvalee Wake advocated a synthetic, mechanistic and pluralistic developmental and evolutionary morphology. In this short essay, I do not evaluate Wake's contributions to our knowledge of the morphology of caecilians, nor her contributions to viviparity, both of which are seminal and substantive, nor do I examine her role as mentor, supervisor and collaborator, but assess her broader conceptual contributions to the development and evolution of morphology as a science. One of the earliest morphologists to take on board the concept of constraint, she viewed constraint explicitly in relation to adaptation and diversity. Her approach to morphology as a science was hierarchical – measure form and function in a phylogenetic context; seek explanations at developmental, functional, ecological, evolutionary levels of the biological hierarchy; integrate those explanations to the other levels. The explanatory power of morphology thus practised allows morphology to inform evolutionary biology and evolutionary theory, and paves the way for the integrative biology Wake has long championed.     

Strong morphological support for the molecular evolutionary tree of placental mammals

The emerging molecular evolutionary tree for placental mammals differs greatly from morphological trees, leading to repeated suggestions that morphology is uninformative at this level. This view is here refuted empirically, using an extensive morphological and molecular dataset totalling 17 431 characters. When analysed alone, morphology indeed is highly misleading, contradicting nearly every clade in the preferred tree (obtained from the molecular or the combined data). Widespread homoplasy overrides historical signal. However, when added to the molecular data, morphology surprisingly increases support for most clades in the preferred tree. The homoplasy in the morphology is incongruent with all aspects of the molecular signal, while the historical signal in the morphology is congruent with (and amplifies) the historical signal in the molecular data. Thus, morphology remains relevant in the genomic age, providing vital independent corroboration of the molecular tree of mammals.     

Choose Your Weapon: Defensive Behavior Is Associated with Morphology and Performance in Scorpions

Morphology can be adaptive through its effect on performance of an organism. The effect of performance may, however, be modulated by behavior; an organism may choose a behavioral option that does not fully utilize its maximum performance. Behavior may therefore be decoupled from morphology and performance. To gain insight into the relationships between these levels of organization, we combined morphological data on defensive structures with measures of defensive performance, and their utilization in defensive behavior. Scorpion species show significant variation in the morphology and performance of their main defensive structures; their chelae (pincers) and the metasoma (“tail”) carrying the stinger. Our data show that size-corrected pinch force varies to almost two orders of magnitude among species, and is correlated with chela morphology. Chela and metasoma morphology are also correlated to the LD50 of the venom, corroborating the anecdotal rule that dangerously venomous scorpions can be recognized by their chelae and metasoma. Analyses of phylogenetic independent contrasts show that correlations between several aspects of chela and metasoma morphology, performance and behavior are present. These correlations suggest co-evolution of behavior with morphology and performance. Path analysis found a performance variable (pinch force) to partially mediate the relationship between morphology (chela aspect ratio) and behavior (defensive stinger usage). We also found a correlation between two aspects of morphology: pincer finger length correlates with the relative “thickness” (aspect ratio) of the metasoma. This suggests scorpions show a trade-off between their two main weapon complexes: the metasoma carrying the stinger, and the pedipalps carrying the chelae.     

Convergence and divergence of the photoregulation of pigmentation and cellular morphology in Fremyella diplosiphon

Photosynthetic pigment accumulation and cellular and filament morphology are regulated reversibly by green light (GL) and red light (RL) in the cyanobacterium Fremyella diplosiphon during complementary chromatic adaptation (CCA). The photoreceptor RcaE (regulator of chromatic adaptation), which appears to function as a light-responsive sensor kinase, controls both of these responses. Recent findings indicate that downstream of RcaE, the signaling pathways leading to light-dependent changes in morphology or pigment synthesis and/or accumulation branch, and utilize distinct molecular components. We recently reported that the regulation of the accumulation of the GL-absorbing photosynthetic accessory protein phycoerythrin (PE) and photoregulation of cellular morphology are largely independent, as many mutants with severe PE accumulation defects do not have major disruptions in the regulation of cellular morphology. Furthermore, morphology can be disrupted under GL without impacting GL-dependent PE accumulation. Most recently, however, we determined that the disruption of the cpeR gene, which encodes a protein that is known to function as an activator of PE synthesis under GL, results in disruption of cellular morphology under GL and RL. Thus, apart from RcaE, CpeR is only the second known regulator to impact morphology under both light conditions in F. diplosiphon.     

Environmental correlates of phenotypic variation: do variable tidal regimes influence morphology in intertidal seaweeds?

Seaweed morphology is often shaped by the hydrodynamic environment. However, exposure to air at low tide represents an additional factor potentially affecting the morphology of intertidal species. Here, we examined the relationships between the morphology of Hormosira banksii, an important intertidal habitat‐forming seaweed in southern Australia, and environmental factors across multiple spatial scales around the island of Tasmania, Australia. Tasmania is surrounded by a diverse coastline with differences in wave exposure, tidal parameters, and temperature. We sampled Hormosira from four regions (100s km apart), three sites (10s km apart) within each region, and two zones (meters apart; eulittoral and sublittoral) at each site, and measured multiple morphological variables to test for differences in morphology at those different spatial scales. Thirteen environmental variables reflecting wave exposure, tidal conditions, and temperature for each site were generated to assess the relationship between Hormosira morphology and environmental variation. Morphology varied at all spatial scales examined. Most notably, north coast individuals had a distinct morphology, generally having smaller vesicles and shorter fronds, compared to other regions. Tidal conditions were the main environmental factors separating north coast sites from other sites and tidal regime was identified as the best predictor of morphological differences between regions. In contrast to other studies, we found little evidence that wave exposure was associated with morphological variation. Overall, our study emphasizes the role of tidal conditions, associated with emersion stress during low tide, in affecting the morphology of intertidal seaweeds.     

Alternaria leaf spot of tobacco II. Independent segregation of morphological and virulence traits in conidial populations of Alternaria tenuis nees

Morphologically, conidia ofAlternaria tenuis exhibit dual forms, A and B. Virulent single conidial isolates commonly produce a considerably higher percentage of A-type conidia than B-type conidia. While avirulent isolates produce more B-type than A-type conidia. Genetic factors governing conidial morphology appear to be extranuclear and not genetically linked to virulence. Selection for A-type conidia for six cultural cycles resulted in a rapid and marked segregation of A-type morphology and virulence.The relationship between conidial morphology and virulence commonly observed in fresh isolates appears fortuitous and is apparently due to separate and independent selection pressures (adverse climate and resistant host tissue) operating on the sameA. tenuis population which results in two genetically independent traits (morphology and virulence) in the population appearing linked. The frequent breakdown of this relationship, especially in culture, indicates that conidial morphology is not a reliable criterion for virulence.     

Are patients with non-ST elevation myocardial infarction undertreated?

Background

We have previously documented significant differences in orthogonal P wave morphology between patients with and without paroxysmal atrial fibrillation (PAF). However, there exists little data concerning normal P wave morphology. This study was aimed at exploring orthogonal P wave morphology and its variations in healthy subjects.

Methods

120 healthy volunteers were included, evenly distributed in decades from 20–80 years of age; 60 men (age 50+/-17) and 60 women (50+/-16). Six-minute long 12-lead ECG registrations were acquired and transformed into orthogonal leads. Using a previously described P wave triggered P wave signal averaging method we were able to compare similarities and differences in P wave morphologies.

Results

Orthogonal P wave morphology in healthy individuals was predominately positive in Leads X and Y. In Lead Z, one third had negative morphology and two-thirds a biphasic one with a transition from negative to positive. The latter P wave morphology type was significantly more common after the age of 50 (P < 0.01). P wave duration (PWD) increased with age being slightly longer in subjects older than 50 (121+/-13 ms vs. 128+/-12 ms, P < 0.005). Minimal intraindividual variation of P wave morphology was observed.

Conclusion

Changes of signal averaged orthogonal P wave morphology (biphasic signal in Lead Z), earlier reported in PAF patients, are common in healthy subjects and appear predominantly after the age of 50. Subtle age-related prolongation of PWD is unlikely to be sufficient as a sole explanation of this finding that is thought to represent interatrial conduction disturbances. To serve as future reference, P wave morphology parameters of the healthy subjects are provided.