Morphological variation in the Weberian apparatus of Cypriniformes

Cypriniformes (which includes the minnows, carps, loaches, algae-eaters, stone loaches, and suckers) is a morphologically diverse and incredibly speciose order of teleosts. It has been suggested that a number of evolutionary innovations, key to improved hearing and feeding, have played an important role in cypriniform fishes' success. One such innovation, the Weberian apparatus, is a novel assemblage of vertebral elements and modified ribs that relay and amplify sound pressure changes from the gas bladder to the inner ear. The Weberian apparatus unites Cypriniformes with other major orders into an extremely species-rich group of fishes, the Otophysi. Together, otophysan fishes comprise one of the largest groups of fishes in the world, as well as the majority of freshwater fishes. Here we present a detailed comparison of the Weberian apparatus in a number of cypriniform families using cleared and stained specimens. We present data regarding inter- and intrafamilial morphological variation within Cypriniformes. With few, but evolutionarily important, exceptions we find that diagnostic features of the Weberian apparatus characterize each family. Interspecific variation within each of the families Balitoridae, Gyrinocheilidae, and Catostomidae is only slight, whereas variation among subfamilies within Cyprinidae and Cobitidae is far more significant. This comparative study identifies a number of distinct morphologies, some of which appear highly correlated with ecological niche. For example, inhabiting swift-moving waters appears to be a key factor in the encapsulation of the anterior gas bladder in some cobitids, balitorids, and gobionin cyprinids.     

Ontogenetic development of weberian ossicles and hearing abilities in the African bullhead catfish

Background

The Weberian apparatus of otophysine fishes facilitates sound transmission from the swimbladder to the inner ear to increase hearing sensitivity. It has been of great interest to biologists since the 19^th century. No studies, however, are available on the development of the Weberian ossicles and its effect on the development of hearing in catfishes.

Methodology/Principal Findings

We investigated the development of the Weberian apparatus and auditory sensitivity in the catfish Lophiobagrus cyclurus. Specimens from 11.3 mm to 85.5 mm in standard length were studied. Morphology was assessed using sectioning, histology, and X-ray computed tomography, along with 3D reconstruction. Hearing thresholds were measured utilizing the auditory evoked potentials recording technique. Weberian ossicles and interossicular ligaments were fully developed in all stages investigated except in the smallest size group. In the smallest catfish, the intercalarium and the interossicular ligaments were still missing and the tripus was not yet fully developed. Smallest juveniles revealed lowest auditory sensitivity and were unable to detect frequencies higher than 2 or 3 kHz; sensitivity increased in larger specimens by up to 40 dB, and frequency detection up to 6 kHz. In the size groups capable of perceiving frequencies up to 6 kHz, larger individuals had better hearing abilities at low frequencies (0.05–2 kHz), whereas smaller individuals showed better hearing at the highest frequencies (4–6 kHz).

Conclusions/Significance

Our data indicate that the ability of otophysine fish to detect sounds at low levels and high frequencies largely depends on the development of the Weberian apparatus. A significant increase in auditory sensitivity was observed as soon as all Weberian ossicles and interossicular ligaments are present and the chain for transmitting sounds from the swimbladder to the inner ear is complete. This contrasts with findings in another otophysine, the zebrafish, where no threshold changes have been observed.     

Histology and structural integration of the major morphologies of the Cypriniform Weberian apparatus

The Weberian apparatus, a diagnostic feature of otophysan fishes, is a novel hearing adaptation integrating several developmental and morphological systems (ear-vertebral column-swim bladder). Otophysan fishes are one of the largest and most successful freshwater clades, with over 10,000 species across most continents. The largest otophysan order, Cypriniformes, dominates the freshwaters of Asia, Europe, North America, and Africa. Spanning such a wide variety of environments, the Weberian apparatus undergoes morphological modifications to maintain functionality. Within Cypriniformes, we propose three distinct morphological classes of the Weberian apparatus based on the level of skeletal expansion around the swim bladder: simple (typical of most Cyprinidae), anterior plate (found in families such as Gyrinocheilidae, Catostomidae, and Botiidae), and encapsulated (either single-capsule as found, e.g., in Gobionidae and Cobitidae, or double-capsule as found, e.g., in Nemacheilidae and Balitoridae). Little ontological or comparative data exists regarding the construction or integration of these different morphologies, and less is known about the tissue level integration and variation within these morphologies. We used paraffin histology to document the hard and soft tissue anatomy of the Weberian apparatus in six species representing all morphological classes. We found sites of similarity across the morphologies including size and structure of the saccule, aspects of ossicle ossification, and swim bladder tunica composition, indicating potential sites of developmental and functional constraint. In contrast, we found differences across both auditory and nonauditory features in otic chamber size, ossification within ossicles and other vertebral elements, and composition of ligaments, indicating likely sites of adaptability. Some of these changes are likely evolutionary (taxonomic), but may be influenced by the environmental niche occupied by the clade. These results show a clear need for increased ontological and comparative study of the complete cypriniform Weberian apparatus, particularly histologically, as well as increased auditory studies across morphological types.     

A novel hearing specialization in the New Zealand bigeye,Pempheris adspersa

The New Zealand bigeye, Pempheris adspersa, is a nocturnal planktivore and has recently been found to be an active sound producer. The rostral end of the swim bladder lies adjacent to Baudelot''s ligament which spans between the bulla and the cleithrum bone of the pectoral girdle. The aim of this study was to use the auditory evoked potential technique to physiologically test the possibility that this structure provides an enhanced sensitivity to sound pressure in the bigeye. At 100 Hz, bigeye had hearing sensitivity similar to that of goldfish (species with a mechanical connection between the swim bladder and the inner ear mediated by the Weberian ossicles) and were much more sensitive than other teleosts without ancillary hearing structures. Severing Baudelot''s ligament bilaterally resulted in a marked decrease in hearing sensitivity, as did swim bladder puncture or lateral line blockage. These results show that bigeye have an enhanced sensitivity to sound pressure and provide experimental evidence that the functional basis of this sensitivity represents a novel hearing specialization in fish involving the swim bladder, Baudelot''s ligament and the lateral line.     

Sexual dimorphism of the Weberian apparatus and pectoral girdle in Sundadanio axelrodi (Ostariophysi: Cyprinidae)

The miniature cyprinid fish, Sundadanio axelrodi , exhibits extreme sexual dimorphism in the skeleton of the Weberian apparatus, the fifth rib and pectoral girdle. Musculature associated with the fifth rib and Weberian apparatus also shows a high degree of sexual dimorphism. It is suggested that these modifications are responsible for the production of a croaking sound that seems to be restricted to males of the species, based on the lack of any corresponding anatomical specializations in females.     

The ontogeny and homology of the Weberian apparatus in the zebrafish Danio rerio (Ostariophysi: Cypriniformes)

The ontogeny of the Weberian apparatus was examined in the zebrafish, Danio rerio , using both cleared and stained specimens and histology. Over 300 individuals from four independent zebrafish lineages, ranging in size from 3 to 28 mm TL, were examined for this study. Results provide a basic understanding of the development of the Weberian apparatus in the wild-type zebrafish. Our results, in conjunction with those already published, point to substantial variation in the development of the Weberian apparatus among otophysans and new interpretations of the homology of certain ossicles (e.g. tripus and claustrum). Hypotheses of homology among various Weberian ossicles are considered and represent an important step in understanding the evolution of sound transmission in ostariophysan fishes.  © 2004 The Linnean Society of London, Zoological Journal of the Linnean Society , 2004, 140 , 241–254.     

Building an evolutionary innovation: Differential growth in the modified vertebral elements of the zebrafish Weberian apparatus

The Weberian apparatus, a complex assemblage of greatly modified vertebral elements, significantly enhances hearing within Otophysi. Ultimately we are interested in investigating the genetic mechanisms responsible for the origin, development and morphological diversification of these vertebral elements in the Weberian apparatus of otophysan fishes. However, a necessary first step involves identifying changes in growth of this region as compared with the vertebrae from which these modified elements purportedly derive. Using an ontogenetic series of the zebrafish, Danio rerio, we collected growth data for specific elements within the Weberian apparatus, including neural arches, ribs, and parapophyses. These data are compared to both serially homologous structures in posterior thoracic vertebrae (which act as internal controls) and vertebral elements from the same axial levels in three other non-otophysan teleosts. Significant differences in growth rate were found among serially homologous structures, as well as at equivalent axial levels in different species. Uniform changes in growth rates (in which all structures derived from a specific somite were equally affected) were not found, suggesting precise targeting of morphological change to specific structures. The variation in growth of anterior vertebrae in and among species was greater than expected. This variation in growth rates created developmental patterns unique to each species. Such patterns of growth may help illuminate the specific heterochronic mechanisms required for the origin and subsequent morphological diversification of the Weberian apparatus. This morphological diversity is exemplified by the multitude of forms seen in the cypriniform Weberian apparatus. Understanding patterns of growth in discrete elements of the Weberian apparatus allows us to hypothesize as to the specific developmental changes, likely constituting differences in gene expression in pathways involved in bone and cartilage differentiation, responsible for this morphological diversity.     

Signs of truth: enchantment, modernity and the dreams of peasant women

This lecture is in three sections. The first discusses the role of classificatory practices distinguishing magic from religion in social life and in narratives of modernity. Concepts of enchantment have been reintroduced into theories of modernity as the Weberian notion of 'ridding the world of magic' has been questioned. The second part sketches some of the characteristic tensions in the Qur'an concerning the signs of truth in the Islamic community. The final section reflects on modern Egyptian denunciations and defences of the dreams of peasant women, dreams that are claimed as direct experiential proofs of the sacred. These dreams command visits to the shrines that are centres for mass ritual, social, and economic activity and whose powers are resistant to regulation by worldly authorities. Such dreams, and the denunciations of them by those self-perceived as religiously orthodox and modern, are part of continuing contests over state and patriarchal authority, citizenship, and exchange with the divine.     

Comparative light and electron microscopic study of the auditory organs of two species of fishes (pisces): Hyphessobrycon simulans (Ostariophysi) and Poecilia reticulata (Acanthopterygii).

Hyphessobrycon simulans has a Weberian apparatus for transmission of sound energy to the auditory organ, whereas Poecilia reticulata does not. The fine structure of the auditory organs is identical in the two species. The better hearing - expressed by large bandwidth and high sensitivity - typical of the Ostariophysi - seems to be based exclusively on the presence of the Weberian apparatus. The sensory epithelium of the saccule and the lagena is made up of hair (sensory) cells and supporting cells. The vertically orientated macula sacculi is divided into a dorsal and a ventral cell area with oppositely arranged hair-cell kinocilia. The sagitta takes up the center of the saccule and shows only three small sites with connections to the otolithic membrane. Remarkably, the dorsal sensory cells are connected to the ventral part of the otolith, but the ventral cells are connected to the dorsal part. The macula of the lagena also comprises a dorsal and a ventral cell area with oppositely arranged hair cells. The sensory cells in all maculae are of type II. They exhibit a striking apical cell protrusion, the cuticular villus. It is partially fused with the kinocilium in the contact zones and joined to the otolithic membrane. The cuticular villus probably stabilizes the long kinocilia.     

Assortative mating,sexual selection,and their consequences for gene flow in Littorina

When divergent populations are connected by gene flow, the establishment of complete reproductive isolation usually requires the joint action of multiple barrier effects. One example where multiple barrier effects are coupled consists of a single trait that is under divergent natural selection and also mediates assortative mating. Such multiple-effect traits can strongly reduce gene flow. However, there are few cases where patterns of assortative mating have been described quantitatively and their impact on gene flow has been determined. Two ecotypes of the coastal marine snail, Littorina saxatilis, occur in North Atlantic rocky-shore habitats dominated by either crab predation or wave action. There is evidence for divergent natural selection acting on size, and size-assortative mating has previously been documented. Here, we analyze the mating pattern in L. saxatilis with respect to size in intensively sampled transects across boundaries between the habitats. We show that the mating pattern is mostly conserved between ecotypes and that it generates both assortment and directional sexual selection for small male size. Using simulations, we show that the mating pattern can contribute to reproductive isolation between ecotypes but the barrier to gene flow is likely strengthened more by sexual selection than by assortment.     

Connecting scales: Achieving in‐field pest control from areawide and landscape ecology studies

Areawide management has a long history of achieving solutions that target pests, however, there has been little focus on the areawide management of arthropod natural enemies. Landscape ecology studies that show a positive relationship between natural enemy abundance and habitat diversity demonstrate landscape‐dependent pest suppression, but have not yet clearly linked their findings to pest management or to the suite of pests associated with crops that require control. Instead the focus has often been on model systems of single pest species and their natural enemies. We suggest that management actions to capture pest control from natural enemies may be forth coming if: (i) the suite of response and predictor variables focus on pest complexes and specific management actions; (ii) the contribution of “the landscape” is identified by assessing the timing and numbers of natural enemies immigrating and emigrating to and from the target crop, as well as pests; and (iii) pest control thresholds aligned with crop development stages are the benchmark to measure impact of natural enemies on pests, in turn allowing for comparison between study regions, and generalizations. To achieve pest control we will need to incorporate what has been learned from an ecological understanding of model pest and natural enemy systems and integrate areawide landscape management with in‐field pest management.     

Production,crystallization, and preliminary X-ray analysis of the human MHC class Ib molecule HLA-E.

HLA-E is the first human class Ib major histocompatibility complex molecule to be crystallized. HLA-E is highly conserved and almost nonpolymorphic, and has recently been shown to be the first specialized ligand for natural killer cell receptors. In functional studies, HLA-E is unlike the class Ia MHC molecules in having tightly restricted peptide binding specificity. HLA-E binds a limited set of almost identical leader sequence peptides derived from class Ia molecules and presents these at the cell surface for recognition by natural killer cell receptors. We now show that the extracellular region of HLA-E forms a stable complex with beta2 microglobulin and can be refolded around synthetic peptide. Crystals of this complex formed slowly over four to six months in the presence of ammonium sulphate. The crystals diffract to 2.85 A with space group P3(1)21 and unit cell dimensions a = 182.2 A, b = 182.2 A, c = 88.4 A.     

Silybin, a new iron-chelating agent.

Silybin, a natural occurring flavolignan isolated from the fruits of Silibum marianum, has been reported to exert antioxidant and free radical scavenging abilities. It was suggested to act also as an iron chelator. The complexation and protonation equilibria of the ferric complex of this compound have been studied by potentiometric, spectrophotometric and electrochemical techniques. The formation of the complex silybin-Ga(III) in anhydrous DMSO-d6 has been studied by 1H NMR spectroscopy. Mass spectrometry and infrared spectroscopy on silybin-Fe(III) complex confirm all data obtained by 1H NMR spectroscopy. The experimental results show that silybin binds Fe(III) even at acidic pH. Different ternary complexes were observed at increasing methoxide ion concentration and their stability constants have been calculated. The results show the possible role of silybin in relation to the chelation therapy of chronic iron overload, as occurs in the treatment of Cooley's anemia.     

团头鲂骨骼系统的发育

本文对团头鲂骨骼系统的发育进行了研究,观察了刚孵化的仔鱼到已具成鱼特征的幼鱼的骨骼发育过程,对脑颅、咽颅、韦伯氏器和脊椎骨、肩带和胸鳍支鳍骨、腰带和腹鳍支鳍骨以及奇鳍支鳍骨在不同生长阶段的形态特征进行了描述。讨论了韦伯氏器、复合神经骨及第二神经板等的发生过程;并根据团头鲂骨骼发育情况,讨论了头骨各骨片的性质。     

Cloning, expression, purification, and biological activity of recombinant native and variant human alpha 1-antichymotrypsins

Human alpha 1-antichymotrypsin has been cloned, sequenced and expressed in Escherichia coli and recombinant protein as well as point-specific mutants have been purified and characterized. The corrected gene-deduced amino acid sequence has 45% overall identity with alpha 1-protease inhibitor, which is higher than the 42% previously reported (Chandra, T., Stackhouse, R., Kidd, V. J., Robson, J. H., and Woo, S. L. C. (1983) Biochemistry 22, 5055-5060). Recombinant antichymotrypsin (rACT) is similar to natural antichymotrypsin with respect to the specificity of its interactions with proteases. Its second-order rate constant for association with bovine chymotrypsin is 6-8 x 10(5) M-1 s-1, which is identical to that of the serum-derived inhibitor. Site-specific mutagenesis has been used to produce two variants of rACT in which the P1 position has been changed from leucine to either methionine (L358M-rACT) or arginine (L358R-rACT). L358M-rACT has a specificity of inhibitory activity toward serine proteases closely similar to that of native rACT. By contrast, the specificity of L358R-rACT is quite different from that of native rACT, most notably in efficiently inhibiting trypsin and human thrombin while showing a decreased ability to inhibit chymotrypsin.     

Factors influencing the natural reproduction decline in the beluga (Huso huso,Linnaeus, 1758), Russian sturgeon (Acipenser gueldenstaedtii,Brandt & Ratzeburg, 1833), and stellate sturgeon (A. stellatus,Pallas, 1771) of the Volga–Caspian basin: A review

The review describes the changes in natural reproduction of three important sturgeon species in the Volga–Caspian basin: (a) the beluga (Huso huso Linneaus, 1758), (b) the Russian sturgeon (Acipenser gueldenstaedtii Brandt &Ratzeburg, 1833), and (c) the stellate sturgeon (Acipenser stellatus Pallas, 1771). Since the past 60 years, these species responded to severe influences of natural and anthropogenic factors. On the basis of original and published data, an analysis has been made of (a) the numbers of larvae migrating from spawning sites (according to plankton net survey), (b) fecundity and histological anomalies in gonad development, (c) the numbers of adult sturgeons in the Caspian Sea and of spawners migrating to the Volga River (according to trawl and beach seine survey), and (d) foraging resources for the sturgeons. The results show that their natural reproduction in the Volga–Caspian basin has declined drastically during the past decades under the impact of (a) fluctuations of the Caspian Sea level and flow discharge from the Volga River, (b) blockage of sturgeon migration routes and loss of spawning sites because of dam construction, (c) water pollution in the lower reaches of the Volga River and in the Caspian Sea, and (d) intensive and selective illegal and unreported fishing. The relative significance of these factors has been changing during the study period.     

Length, mass, and denaturation of double-stranded RNA molecules compared with DNA

The contour lengths of linear, double-stranded (ds) RNAs from mycovirus PcV and Pseudomonas bacteriophage phi 6 have been measured with samples prepared for the electron microscope from 0.05 to 0.5 M NH4Cl solutions. A linear dependence of contour length on the logarithm of ionic strength was found and compared with that of dsDNA (pBR322, linearized and open-circular forms). Conditions for molecular weight determinations of any natural dsRNA by electron microscopy have been established, and the method has been calibrated with phi 6 dsRNA of known nucleotide sequence. The results imply that dsRNA in 0.20 M NH4Cl solution has a rise per basepair of 0.271 nm, which is shorter than that in the A-conformation (4%) and in the A'-conformation (10%). The thermal behavior of dsRNA in terms of melting temperature and exhibition of fine structure of melting curves was found to be generally similar to that of dsDNA, as expected from the literature. Folding of dsRNA in ethanolic solution was similar to that of dsDNA. However, in contrast to dsDNA, coiled coils could not be induced by ethanol, which is consistent with dsRNA being stiffer than dsDNA. Concerning dsDNA, the results show that a contraction in rise per basepair by 0.1 nm is coupled with an increase in the winding angle between basepairs by 0.47 degrees, as qualitatively predicted by polyelectrolyte theory.