Functional and evolutionary anatomy of the African suckermouth catfishes (Siluriformes: Mochokidae): convergent evolution in Afrotropical and Neotropical faunas

Of those fishes scraping food off substrates and using head parts in substrate attachment for station‐holding, the catfish families Loricariidae, Astroblepidae and Mochokidae display the most dramatically adapted morphologies. Loricariidae and Astroblepidae, living in the Neotropical freshwaters, exclusively contain suckermouth catfish species, and their anatomy and head kinematics have already been studied into detail. Among Mochokidae, living in the tropical freshwaters of Africa, only the chiloglanidine subfamily has a sucker mouth, and occupies similar niches in Africa as both Neotropical families do in South America. Having derived from relatively unrelated catfish ancestors, their anatomy is poorly known, and the nature of their scraping and station‐holding capabilities is not known at all. This paper provides details on the chiloglanidine head anatomy and function (relating their anatomy to that of the non‐suckermouth Mochokidae), and compares this Afrotropical suckermouth taxon with both Neotropical suckermouth families. It identifies both convergences and differing anatomical and kinematic solutions to the same key needs of food‐scraping and station‐holding suckermouth fishes. Chiloglanidine mochokids differ from both Neotropical families in having less mobile jaws, with an upper jaw assisting more in station‐holding than in feeding. They share the highly mobile lower lip with both Neotropical taxa, although the configuration of the intermandibular/protractor hyoidei muscle system, changing the volume of the sucker‐disc cavity, differs in all three taxa. Chiloglanidines have a single, posterior inflow opening into this cavity, whereas Loricariidae have two lateral openings, and Astroblepidae have none, using an opercular incurrent opening instead. The chiloglanidine buccal valve system consists of two passive valves, as in Astroblepidae. Although less diverse in number of genera and species, this Afrotropical suckermouth taxon possesses the anatomical and kinematic key elements allowing a successful occupation of a niche similar to the one found in the Loricariidae + Astroblepidae clade.     

Configuration of the setal fields of Rhoptropus (Gekkota: Gekkonidae): functional, evolutionary, ecological and phylogenetic implications of observed pattern

Many gekkotans possess seta-bearing adhesive subdigital pads. Details of setal structure, however, are largely based upon putatively exemplary fibrils deemed typical of the species. Little is known of the pattern of configuration of the setae across the subdigital pads and how great, if any, the variance in structure and dimensions is. To understand setal fields as functional entities, as opposed to individual setae, it is necessary to consider this pattern. Additionally, gekkotans within individual radiations occupy different environments and potentially are substrate-specific in terms of the locomotor surface exploited. To investigate these issues, we herein examine the configuration and dimensions of seven species of the gekkotan genus Rhoptropus , and an outgroup taxon, Chondrodactylus bibronii . All of these taxa are rupicolous and the array of rock surfaces exploited by this cluster of taxa is extensive. Our results show that setal field configuration follows a predictable pattern, both from one digit to another within a species, and between homologous digits and anatomical locations between species. One species, Rhoptropus afer , a more terrestrial taxon, exhibits significantly shorter setae and a smaller subdigital pad area than do its congeners, but exhibits the same overall pattern of setal arrangement. Our findings have implications for the understanding of the evolution of adhesive structures, and for the principles used for generating and manufacturing biomimetic artificial microfibrillar arrays.     

Distribution of L1-retroposons on the giant sex chromosomes of Microtus cabrerae (Arvicolidae, Rodentia): functional and evolutionary implications

Long interspersed nuclear elements (L1 or LINE-1) are the most abundant and active retroposons in the mammalian genome. Traditionally, the bulk of L1 sequences have been explained by the ‘selfish DNA’ hypothesis; however, recently it has been also argued that L1s could play an important role in genome and gene organizations. The non-random chromosomal distribution of these retroelements is a striking feature considered to reflect this functionality. In the present study we have cloned and analyzed three different L1 fragments from the genome of the rodent Microtus cabrerae. In addition, we have examined the chromosomal distribution of this L1 in several species of Microtus, a very interesting group owing to the presence in some species of enlarged (‘giant’) sex chromosomes. Interestingly, in all species analyzed, L1-retroposons have preferentially accumulated on both the giant- and the normal-sized sex chromosomes compared with the autosomes. Also we have demonstrated that L1-retroposons are not similarly distributed among the heterochromatic blocks of the giant sex chromosomes in M. cabrerae and M. agrestis, which suggest that L1 retroposition and amplification over the sex heterochromatin have been different and independent processes in each species. Finally, we proposed that the main factors responsible for the L1 distribution on the mammalian sex chromosomes are the heterochromatic nature of the Y chromosome and the possible role of L1 sequences during the X-inactivation process.     

Plastid DNA from Pyrenomonas salina (Cryptophyceae): physical map,genes, and evolutionary implications

Summary Cryptomonads are thought to have arisen from a symbiotic association between a eukaryotic flagellated host and a eukaryotic algal symbiont, presumably related to red algae. As organellar DNAs have proven to be useful tools in elucidating phylogenetic relationships, the plastid (pt) DNA of the cryptomonad alga Pyrenomonas salina has been characterized in some detail. A restriction map of the circular 127 kb ptDNA from Pyrenomonas salina was established. An inverted repeat (IR) region of about 5 kb separates two single-copy regions of 15 and 102 kb, respectively. It contains the genes for the small and large subunit of rRNA. Ten protein genes, coding for the large subunit of ribulose-1,5-bisphosphate carboxylase, the 47 kDa, 43 kDa and 32 kDa proteins of photosystem II, the ribosomal proteins L2, S7 and S11, the elongation factor Tu, as well as the - and -subunits of ATP synthase, have been localized on the restriction map either by hybridization of heterologous gene probes or by sequence homologies. The gene for the plastidal small subunit (SSUr) RNA has been sequenced and compared to homologous SSU regions from the cyanobacterium Anacystis nidulans and plastids from rhodophytes, chromophytes, euglenoids, chlorophytes, and land plants. A phylogenetic tree constructed with the neighborliness method and indicating a relationship of cryptomonad plastids with those of red algae is presented.     

Geometric morphometrics of the wing in the subgenus Culicoides (Diptera: Ceratopogonidae): from practical implications to evolutionary interpretations

Biting midges of the genus Culicoides Latreille have been incriminated in transmission of bluetongue. Since 1998, the disease has spread across Europe provoking the largest epidemic ever recorded with important economic loses. Some species of the subgenus Avaritia and Culicoides have been described as candidate vectors involved in these epizootics. Both subgenera contain groups of cryptic species that could differ in their vectorial capacity. For this reason, the correct identification of vector species is considered an essential issue in epidemiological programs. In the current study, the usefulness of wing form in differentiating morphologically similar species of the subgenus Culicoides by means of geometric morphometric techniques is assessed in specimens previously identified through molecular analyses based on cytochrome oxidase subunit I gene sequences. Significant differences between species were detected in the two components of form, i.e., size and shape. Although wing size was affected by temperature, wing shape showed a more stable specific variation, allowing the proper classification of a high percentage of specimens. In addition, the concordance between phylogenies inferred from molecular data and phenetic clusters suggests the existence of a phylogenetic signal in wing shape. These findings enhance the use of this complex phenotypic trait not only to infer genetic relationships among species of the subgenus Culicoides but also as apotentially powerful tool to differentiate cryptic species within the genus.     

The effect of craniokinesis on the middle ear of domestic chickens (Gallus gallus domesticus)

The avian middle ear differs from that of mammalians and contains a tympanic membrane, one ossicle (bony columella and cartilaginous extra‐columella), some ligaments and one muscle. The rim of the eardrum (closing the middle ear cavity) is connected to the neurocranium and, by means of a broad ligament, to the otic process of the quadrate. Due to the limited number of components in the avian middle ear, the possibilities of attenuating the conduction of sound seem to be limited to activity of the stapedius muscle. We investigate to what extent craniokinesis may impact the components of the middle ear because of the connection of the eardrum to the movable quadrate. The quadrate is a part of the beak suspension and plays an important role in craniokinesis. Micro‐computed tomography was used to visualize morphology and the effect of craniokinesis on the middle ear in the domestic chicken (Gallus gallus domesticus). Both hens and roosters are considered because of their difference in vocalization capacity. It is hypothesized that effects, if present, of craniokinesis on the middle ear will be greater in roosters because of their louder vocalization. Maximal lower jaw depression was comparable for hens and roosters (respectively 34.1 ± 2.6° and 32.7 ± 2.5°). There is no overlap in ranges of maximal upper jaw elevation between the sexes (respectively 12.7 ± 2.5° and 18.5 ± 3.8°). Frontal rotation about the transversal quadrato‐squamosal, and inward rotation about the squamosal‐mandibular axes of the quadrate were both considered to be greater in roosters (respectively 15.4 ± 2.8° and 11.1 ± 2.5°). These quadrate rotations did not affect the columellar position or orientation. In hens, an influence of the quadrate movements on the shape of the eardrum could not be detected either; however, craniokinesis caused slight stretching of the eardrum towards the caudal rim of the otic process of the quadrate. In roosters, an inward displacement of the conical tip of the tympanic membrane of 0.378 ± 0.21 mm, as a result of craniokinesis, was observed. This is linked to a flattening and slackening of the eardrum. These changes most likely go along with a deformation of the extra‐columella. Generally, in birds, larger beak opening is related to the intensity of vocalization. The coupling between larger maximal upper jaw lifting in roosters and the slackening of the eardrum suggest the presence of a passive sound attenuation mechanism during self‐vocalization.     

Morphometry,Microstructure, and Wear Pattern of Neornithischian Dinosaur Teeth From the Upper Cretaceous Iharkút Locality (Hungary)

Teeth of iguanodontian ornithopods and ceratopsians could be remarkably similar, thus the referral of isolated dental material to particular neornithischian clades can be highly problematic. These groups are represented by the rhabdodontid Mochlodon vorosi and the basal coronosaurian Ajkaceratops kozmai in the Upper Cretaceous Csehbánya Formation at Iharkút (western Hungary). Whereas teeth of Mochlodon are common elements at the locality, no dental material belonging to Ajkaceratops was identified until now. Here we used mathematical statistical approaches, as well as tooth wear and dental microstructure analysis in order to decide whether the teeth previously referred to Mochlodon can be treated as a homogenous sample, or some remains belong rather to Ajkaceratops. According to our results, there was a striking morphological and structural convergence between the teeth of both taxa. However, the wear study revealed the existence of two different patterns within the sample. One is characterized by straight and parallel microstriations that suggest orthal movements during the jaw closure. This pattern was associated with Mochlodon. The other pattern appeared only on a few teeth, and it can be differentiated by its distinctive curved microstriations that indicate circumpalinal chewing. Because curved striations have never been described in ornithopods, but are found in several neoceratopsians, this pattern was associated here with Ajkaceratops. Here we present the first teeth that can provisionally be referred to the latter genus. We believe that the methodology discussed in this article will facilitate distinguishing ceratopsian and ornithopod teeth in other localities as well. Anat Rec, 300:1439–1463, 2017. © 2017 Wiley Periodicals, Inc.     

On the development of the shoulder girdle in Crocidura russula (Soricidae) and other placental mammals: evolutionary and functional aspects

The development of the shoulder girdle was studied in embryonic stages and a neonate of Crocidura russula using histological sections and 3-D reconstructions. Neonatal stages of Suncus etruscus and Mesocricetus auratus, both altricial placentals, were also studied. The earliest stage of C russula, in which the scapula is still partially blastematous, has already a supraspinous fossa. The dorsal portion of the scapular spine does not develop from the anterior margin of the scapula. Its mode of development varies among the placentals studied to date. In some it is completely appositional bone, in others it consists of bone formed mostly by endochondral ossification of a dorsal cartilaginous process stemming from the acromium. During development the supraspinatus muscle increases in size in proportion to the infraspinatus muscle and the humeral head increases in size in relation to the glenoid fossa. Placentals have secondary cartilage in the sternal and acromial ends of the clavicle, a derived feature absent in Marsupialia. Even the most altricial placentals have a more developed shoulder girdle at birth than any newborn marsupial studied to date.     

Clavicles,interclavicles, gastralia,and sternal ribs in sauropod dinosaurs: new reports from Diplodocidae and their morphological,functional and evolutionary implications

Ossified gastralia, clavicles and sternal ribs are known in a variety of reptilians, including dinosaurs. In sauropods, however, the identity of these bones is controversial. The peculiar shapes of these bones complicate their identification, which led to various differing interpretations in the past. Here we describe different elements from the chest region of diplodocids, found near Shell, Wyoming, USA. Five morphotypes are easily distinguishable: (A) elongated, relatively stout, curved elements with a spatulate and a bifurcate end resemble much the previously reported sauropod clavicles, but might actually represent interclavicles; (B) short, L‐shaped elements, mostly preserved as a symmetrical pair, probably are the real clavicles, as indicated by new findings in diplodocids; (C) slender, rod‐like bones with rugose ends are highly similar to elements identified as sauropod sternal ribs; (D) curved bones with wide, probably medial ends constitute the fourth morphotype, herein interpreted as gastralia; and (E) irregularly shaped elements, often with extended rugosities, are included into the fifth morphotype, tentatively identified as sternal ribs and/or intercostal elements. To our knowledge, the bones previously interpreted as sauropod clavicles were always found as single bones, which sheds doubt on the validity of their identification. Various lines of evidence presented herein suggest they might actually be interclavicles – which are single elements. This would be the first definitive evidence of interclavicles in dinosauromorphs. Previously supposed interclavicles in the early sauropodomorph Massospondylus or the theropods Oviraptor and Velociraptor were later reinterpreted as clavicles or furculae. Independent from their identification, the existence of the reported bones has both phylogenetic and functional significance. Their presence in non‐neosauropod Eusauropoda and Flagellicaudata and probable absence in rebbachisaurs and Titanosauriformes shows a clear character polarity. This implicates that the ossification of these bones can be considered plesiomorphic for Sauropoda. The proposed presence of interclavicles in sauropods may give further support to a recent study, which finds a homology of the avian furcula with the interclavicle to be equally parsimonious to the traditional theory that furcula were formed by the fusion of the clavicles. Functional implications are the stabilizing of the chest region, which coincides with the development of elongated cervical and caudal vertebral columns or the use of the tail as defensive weapon. The loss of ossified chest bones coincides with more widely spaced limbs, and the evolution of a wide‐gauge locomotor style.     

Third genome size category of avian paramyxovirus serotype 1 (Newcastle disease virus) and evolutionary implications

The goal of the study was to establish if there was a relationship between molecular patterns and virus evolution. Therefore the complete genome sequence of two distinct apathogenic Newcastle disease virus (NDV) strains was determined and a third genome size category, containing 15,198 nucleotides, was recognized. Phylogenetic analysis revealed that two major separations resulting in three genome size categories occurred during the history of NDV. An ancient division in the primordial reservoir (wild waterbird species) led to two basal sister clades, class I and II, with genome sizes 15,198 (due to a 12 nucleotide insert in the phosphoprotein gene) and 15,186 nucleotides, respectively. Ancestors of only class II viruses colonized chicken populations and subsequently converted to virulent forms. These took place more than once and resulted in an early lineage [including genotypes I–IV and H33(W)] with genome size of 15,186 nucleotides. A second division occurred in the 20th century in the secondary (chicken) host. This gave rise to the branching-off of a clade (including recent genotypes V–VIII consisting of only pathogenic viruses) with the concomitant insertion of six nucleotides into the 5′ non-coding region of the nucleoprotein gene thereby increasing the genome size to 15,192 nucleotides.     

Ontogeny of the Early Triassic Cynodont Thrinaxodon liorhinus (Therapsida): Cranial Morphology

The cranial morphology of 68 Thrinaxodon liorhinus specimens, ranging in size from 30 to 96 mm in basal skull length, is investigated using both qualitative and quantitative analyses. From this comprehensive survey, we determined that nine cranial features, including five in the temporal region, separated the sample into four ontogenetic stages. A bivariate analysis of 60 specimens indicated that the skull generally increased in size isometrically, with the exception of four regions. The orbit had negative allometry, a result consistent with other ontogenetic studies of tetrapods, whereas the length of the snout, palate, and temporal region showed positive allometry. The last trend had strong positive allometry indicating that during ontogeny the length of the sagittal crest increased at a much faster rate than the rest of the skull. The large number of changes in the temporal region of the skull of Thrinaxodon may indicate a greater development of the posterior fibres of the temporalis musculature from an early ontogenetic stage. For example, the posterior sagittal crest developed much earlier in ontogeny than the anterior crest that formed in adults, and bone was deposited dorsally creating a unified posterior sagittal crest rather than having a suture that spanned the entire depth of the skull roof. In combination with the isometric height of the zygomatic arch and the almost complete absence of the zygomatic arch angulation, these ontogenetic changes suggest that there was greater development of the temporalis relative to the masseter muscles, indicating a strong posterodorsal movement of the mandible in Thrinaxodon. Anat Rec, 298:1440–1464, 2015. © 2015 Wiley Periodicals, Inc.     

Expression and localization of fibroblast growth factor (FGF)23 and Klotho in the spleen: its physiological and functional implications

The FGF23–Klotho signaling axis is known to exert anti-aging effects via calcium–phosphorus metabolism. In mice deficient in FGF23–Klotho signaling, however, the number of splenocytes is reduced. FGF23 is expressed in both bone and spleen, with regulation of its production differing in these organs. As FGF23–Klotho signaling may play an immunological role in the spleen, splenocytes in male C57BL/6J mice were assayed for expression of Klotho or FGF23 by flow cytometry and immunohistochemistry. Cells that expressed Klotho included CD45R/B220⁺ CD21/CD35⁺ CD1d⁺ CD43^? marginal zone B cells. These cells also expressed FGF receptor 1, indicating that Klotho-positive B cells could respond to FGF23. Plasmacytoid dendritic cells (pDCs) with CD11c⁺ CD45R/B220⁺ CD11b^? CD8α^? were found to produce FGF23. Klotho-positive cells and FGF23-producing cells were present in close proximity to each other, suggesting that FGF23 produced by pDCs may act within a limited area. These findings indicate that FGF23–Klotho signaling could play a biological or immunological role in the spleen.     

Cellular and molecular mechanisms in the development of a cleft lip and/or cleft palate; insights from zebrafish (Danio rerio)

Human cleft lip and/or palate (CLP) are immediately recognizable congenital abnormalities of the face. Lip and palate develop from facial primordia through the coordinated activities of ectodermal epithelium and neural crest cells (NCCs) derived from ectomesenchyme tissue. Subtle changes in the regulatory mechanisms of NCC or ectodermal epithelial cells can result in CLP. Genetic and environmental contributions or a combination of both play a significant role in the progression of CLP. Model organisms provide us with a wealth of information in understanding the pathophysiology and genetic etiology of this complex disease. Small teleost, zebrafish (Danio rerio) is one of the popular model in craniofacial developmental biology. The short generation time and large number of optically transparent, easily manipulated embryos increase the value of zebrafish to identify novel candidate genes and gene regulatory networks underlying craniofacial development. In addition, it is widely used to identify the mechanisms of environmental teratogens and in therapeutic drug screening. Here, we discuss the value of zebrafish as a model to understand epithelial and NCC induced ectomesenchymal cell activities during early palate morphogenesis and robustness of the zebrafish in modern research on identifying the genetic and environmental etiological factors of CLP.     

Expression of fibroblast growth factor-2 (FGF-2) in early stages (days 3-11) of the development of the avian lung, Gallus gallus variant domesticus: an immunocytochemical study

In the avian lung, the bronchial system forms from epithelial (endodermal) cells. The intrapulmonary primary bronchus is the focal point of airway development. It originates secondary bronchi (SB) along its proximal-distal extent and parabronchi (tertiary bronchi) arise from and connect the SB. From as early as day 3.5, fibroblast growth factor-2 (FGF-2) is diffusely expressed in the epithelial and mesenchymal cells. Up-regulation of FGF-2 in discrete areas of the developing lung seem to set the growth rate, trajectories followed, areas appropriated, three-dimensional symmetry and coupling of the airways. Expressed early in development and persisting into the incubation period, FGF-2 may be involved in the formation of the avian lung. Morphogenetic differences between the avian and the mammalian lungs may explain the existing structural contrarieties.     

Intercontinental reassortment and genomic variation of low pathogenic avian influenza viruses isolated from northern pintails (Anas acuta) in Alaska: Examining the evidence through space and time

Migration and population genetic data for northern pintails (Anas acuta) and phylogenetic analysis of low pathogenic avian influenza (LPAI) viruses from this host in Alaska suggest that northern pintails are involved in ongoing intercontinental transmission of avian influenza. Here, we further refine this conclusion through phylogenetic analyses which demonstrate that detection of foreign lineage gene segments is spatially dependent and consistent through time. Our results show detection of foreign lineage gene segments to be most likely at sample locations on the Alaska Peninsula and least likely along the Southern Alaska Coast. Asian lineages detected at four gene segments persisted across years, suggesting maintenance in avian hosts that migrate to Alaska each year from Asia or in hosts that remain in Alaska throughout the year. Alternatively, live viruses may persist in the environment and re-infect birds in subsequent seasons.     

Role of the neural crest in development of the cartilaginous cranial and visceral skeleton of the medaka, Oryzias latipes (Teleostei)

Summary Neural crestectomies were performed on neurula stage medaka embryos to remove neural crest with tungsten needles from one of five anteriorly located zones. The embryos were allowed to develop to stage 35 (immediately posthatching) larvae, then cleared and stained for cartilage. An analysis of changes to the head skeletons indicated that most of the anterior neurocranium and the entire viscerocranium received neural crest contributions during development. The elements involved included; the lamina orbitonasalis of the nasal capsule, the trabeculae, Meckels' cartilage and the quadrate of the lower jaw, the pterygoid process, the orbital cartilages and the epiphyseals of the neurocranial roof, as well as all the elements of the hyoid and branchial arches. By further analysis of only those neural crest ablations which produced alterations to the head skeleton, the neural crest cells which contributed to the development of each element were mapped. They originated principally, from one of three regions; the mesencephalon (second most anterior zone removed, number II), the preotic rhombencephalon (zone III), or the postotic rhombencephalon (zone IV). Neural crest from the level of the prosencephalon (zone I) was not chondrogenic nor was neural crest from the fifth region (zone V) which extended beyond the 5^th to about the 8^th or 10^th somite and marked the anterior end of trunk neural crest. The data are discussed and are found to be consistent with the results from other vertebrates and support the central role of the neural crest in the development and evolution of the vertebrate bead skeleton.