Precision of age determination from otoliths,opercular bones,scales and vertebrae in the threatened freshwater snakehead,Channa punctata (Bloch, 1793)

Ages were estimated from otoliths, opercular bones, scales, and vertebrae of 514 specimens of Channa punctata from three Indian rivers – the Ganga, Gomti, and Yamuna – to evaluate the potential bias of age estimates between readers and between pairs of aging structures. Standard procedures were followed to prepare and study the age structures. Among all structures, otoliths showed highest (97.4%) values of agreement between readers' age estimates followed by the opercular bones (89.5%), scales (84.2%) and vertebrae (78.9%). Because of the highest percentage of agreement and lowest average percentage of error (0.05%) and coefficient of variation (0.76%) values between readers, otoliths were considered the most suitable aging structure for C. punctata. When otoliths ages were compared with those of the other structures viz., opercular bones, scales and vertebrae, percentage of agreement was found highest between estimates (90.8%) of otoliths and opercular bones.     

The use of opercular bones in the study of age and growth in Labeo senegalensis from Lake Kainji, Nigeria

Check marks were found on the scales and opercular bones of Labeo senegalensis from Lake Kainji, Nigeria. The scale marks were often indistinct and difficult to interpret, but an attempt was made to determine age from the opercular bones.
At least two check marks per year were found on the opercular bones, one of these occurring during June-July, and the other during January. The relationship between opercular length and fish total length was plotted logarithmically and back-calculations of length made.
Problems of interpretation are discussed in relation to possible causes of ring formation.     

Ontogeny of the osteocranium in the African catfish,Clarias gariepinus Burchell (1822) (Siluriformes: Clariidae): Ossification sequence as a response to functional demands

The ontogeny of the bony skull of the African catfish, Clarias gariepinus, is studied from initial ossification until a complete skull is formed. The ossification sequence in C. gariepinus seems to be related to the functional demands that arise in a developing larva. Early ossification of the opercular bone coincides with the initiation of opercular skin movements. Early ossifications involve several dentulous bones, formed shortly before the transition phase from endogenous to exogenous feeding. The enlarging branchiostegal membrane becomes supported by the gradual adding of branchiostegal rays. Parasphenoid ossification may be related to protection of the brain during prey transport, whereas the several hyoid bones, including the parurohyal, are formed in relation to the increasing loads exerted onto the tendons of the sternohyoideus and consequently onto the hyoid bar. Overall skull reinforcement occurs almost simultaneously, with a whole set of perichondral bones arising especially at places of high mechanical load. The suspensorium becomes protected against dislocation in an anteroposterior direction through a ligamentous connection, which even becomes partially ossified, forming the sesamoid entopterygoid. Later, the cranial lateral-line system becomes enclosed by a set of gutters, which close, frequently becoming plate-like later in ontogeny. The brain also becomes covered dorsally. Additional dentition (prevomeral tooth plates) formation seems to coincide with formation of the opercular four-bar system, as well as with the time the digestive system becomes completely functional. Eventually, unossified regions between the bones become closed off, fortifying and completely covering the skull. J. Morphol. 235:183–237, 1998. © 1998 Wiley-Liss, Inc.     

Neural ectoderm,neural crest,and placodes: Contribution of the otic placode to the ectodermal lining of the embryonic opercular cavity in Atlantic cod (Teleostei)

Development of neural ectoderm, neural crest, and otic placode with special reference to a new placodal derivative, the ectodermal lining of the opercular cavity, is described in a teleost fish, the Atlantic cod Gadus morhua, from a stage-by-stage examination of embryonic development. The ectodermal lining of the opercular cavity forms by invagination of the otic placode. The neural plate “infolds” by a wave of cellular rearrangement that transforms the neural plate into a neural rod. This transformation creates a distinct dorsal ectodermal cell layer. When the neural rod is arranged as monostratified columnar cells in the forebrain and midbrain, dorsal ectoderm at the midbrain level thickens lateral to the neural rod to form a cell cluster—the presumptive neural crest and placode. Upon migration of the neural crest from the postoptic midbrain, the dorsolateral area of the dorsal ectoderm thickens and segregates from the neural crest as a placode that is continuous with the presumptive lens placode. As the neural crest migrates from the hindbrain, this placode extends along the hindbrain as a single continuous cluster of cells. At the onset of formation of the lens placode, this continuous placode becomes the placode in the postoptic area of the midbrain and separates into the otic placode at the hindbrain. The otic placode gives rise to the otic neuromast and probably the otic lateral line nerves rostrally and to the ectodermal cell lining of the opercular cavity and otic vesicles caudally. The opercular cavity forms by invagination of the otic placode, creating an internal lumen lined by ectoderm that becomes continuous with evaginated endodermal pharyngeal cells. Free neuromasts are observed along the trailing edge of the external opening of the opercular cavity, which lies horizontally, ventral to the otic vesicles. As embryos develop to hatching, the opening rotates and takes up a vertical position. The adult opercular apparatus, including associated bones and muscles, forms during larval stages. The otic neuromast may be a remnant of neuromasts in the spiracle organ. The spiracle opening lies between the mandibular and hyoid arches, whereas the opercular cavity opens between the hyoid and the first branchial arches. The spiracle opening is, therefore, not homologous with the external opening of the opercular cavity, although the cell lining of the spiracle opening may be of placodal origin. J Morphol 231:231–252, 1997. © 1997 Wiley-Liss, Inc.     

MiR‐199b‐5p inhibits osteogenic differentiation in ligamentum flavum cells by targeting JAG1 and modulating the Notch signalling pathway

Ossification of the ligamentum flavum (OLF) is a pathology almost only reported in East Asian countries. The leading cause of OLF is thoracic spinal canal stenosis and myelopathy. In this study, the role of miR‐199b‐5p and jagged 1 (JAG1) in primary ligamentum flavum cell osteogenesis was examined. MiR‐199b‐5p was found to be down‐regulated during osteogenic differentiation in ligamentum flavum cells, while miR‐199b‐5p overexpression inhibited osteogenic differentiation. In addition, JAG1 was found to be up‐regulated during osteogenic differentiation in ligamentum flavum cells, while JAG1 knockdown via RNA interference caused an inhibition of Notch signalling and osteogenic differentiation. Moreover, target prediction analysis and dual luciferase reporter assays supported the notion that JAG1 was a direct target of miR‐199b‐5p, with miR‐199b‐5p found to down‐regulate both JAG1 and Notch. Further, JAG1 knockdown was demonstrated to block the effect of miR‐199b‐5p inhibition. These findings imply that miR‐199b‐5p performs an inhibitory role in osteogenic differentiation in ligamentum flavum cells by potentially targeting JAG1 and influencing the Notch signalling pathway.     

The growth of the freshwater murrel,Ophicephalus punctatus Bloch

Summary The growth of O. punctatus has been studied from the zones on the opercular bones and scales. Size estimates obtained from the opercular bones and scales were further substantiated by length frequency distribution and back-calculations. A close agreement in length-age relationship was obtained by various methods. These observations provide adequate evidence towards the validity of age determination in O. punctatus.Growth rate differs markedly in the two sexes. Males grow faster than the females. To study the changes in length with age, von Bertalanffy growth equation and Gompertz curve were used. The theoretical lengths obtained from the von Bertalanffy equation agreed very closely with the observed lengths.There is sexual difference in the weight-length relationship of O. punctatus. Modal weight of each year class obtained according to age reading showed that growth in weight is faster in males. The theoretical growth equation gives a good fit for weight-age data. O. punctatus is generally a fish of the impounded waters. The interrelationship between pond environment and growth characteristics has been discussed.     

Functional architecture of the ligamentum arteriosum in adults]

The ligamentum arteriosum was studied in eight normal adult human hearts obtained at autopsy. Four of these hearts were treated by the Zemper method and extensively dissected under a steromicroscope (from X 6 up to X 40); two were embedded in celloidin and sectioned at 100mugm; two were embedded in paraffin and sectioned one 50mugm and the other at 75 mugm. Section were stained by the axan and the resorcin-fuchsin methods. Unstained sections were examined under polarized light.The ligamentum arteriosum may be considered as a small smooth muscle, whose origin is in the arteria pulmonalis sinistra and the insertion in the arcus aortae. Therefore, the ligamentum arterisum may be considered as a myoelastic system, included in a collagenous stroma. Muscle, elastic and collagen fibers present a cross-spiral disposition. Being a myoelastic system with a collagen component, the ligamentum arteriosum cannot be considered as a simple arcus aortae support; it must play some functional role in controlling the arcus aortae curvature during the several different steps of the cardiac cycle.     

Histology of melanic flank and opercular color pattern elements in the firemouth cichlid,Thorichthys meeki

Dark melanic color pattern elements, such as bars, stripes, and spots, are common in the skin of fishes, and result from the differential distribution and activity of melanin‐containing chromatophores (melanophores). We determined the histological basis of two melanic color pattern elements in the integument of the Firemouth Cichlid, Thorichthys meeki. Vertical bars on the flanks were formed by three layers of dermal melanophores, whereas opercular spots were formed by four layers (two lateral and two medial) in the integument surrounding the opercular bones. Pretreatment of opercular tissue with potassium and sodium salts effectively concentrated or dispersed intracellular melanosomes. Regional differences in epidermal structure, scale distribution, and connective tissues were also identified. J. Morphol. 2013. © 2013 Wiley Periodicals, Inc.     

Age and growth of the common carp, Cyprinus carpio, in the River Murray, Australia: validation, consistency of age interpretation, and growth models

The present study validates age estimates from a suite of calcified structures (scales, opercular bones and otoliths), assesses the consistency of age interpretations and evaluates growth models in common carp from the lower Murray River, Australia. Marginal increment analysis was used to validate annulus counts, with attention to the 'edge interpretation problem'. The formation of annuli occurred annually after pooling annulus groups, and in carp 4 and 5 years old. The regular alternation of opaque and translucent zones in opercular bones and whole otoliths of younger and older carp was also suggestive of annual periodicity. From systematic comparisons, the use of both opercular bones and whole otoliths in routine age determinations is recommended. Six growth models, including the von Bertalanffy growth function (VBGF) and five polynomial curves were tested to describe growth in length. A log-log quadratic function, by virtue of its precision, and the VBGF, with wider applicability and more biological realism, were chosen.     

Development and evolution of craniofacial patterning is mediated by eye-dependent and -independent processes in the cavefish Astyanax

We studied the development and evolution of craniofacial features in the teleost fish, Astyanax mexicanus. This species has an eyed surface dwelling form (surface fish) and many different cave dwelling forms (cavefish) with various degrees of reduced eyes and pigmentation. The craniofacial features we examined are the tooth-bearing maxillary bones, the nasal and antorbital bones, the circumorbital bones, and the opercular bones, all of which show evolutionary modifications in different cavefish populations. Manipulations of eye formation by transplantation of the embryonic lens, by lentectomy, or by removing the optic vesicle showed that eye-dependent and -independent processes change both the surface fish and cavefish craniofacial skeletons. The size of the olfactory pits, which the nasal and antorbital bones define, and the size and positioning of the circumorbital bones were found to correlate with eye development. For the six suborbital bones (SO1-6), the relationship with the developing eye appears to be due to ossification initiated from foci in the suborbital canal of cranial neuromasts, whose patterning is also highly correlated with the presence or absence of an eye. By contrast, we found that the number of maxillary teeth, the number of SO3 bone elements, the positioning of SO4-6 with respect to the opercular bone, and the shape of the opercular bone are not dependent on eye formation and vary among different cavefish populations. The results suggest that evolution of the cavefish craniofacial skeleton is controlled by multiple developmental events, some a direct consequence of eye degeneration and others unrelated to loss of the eye.     

Morphological Development of the Opercular Apparatus in Kneria wittei(Ostariophysi: Gonorynchiformes) with Comments on its Possible Function

The structure, development and function of the male opercular apparatus were examined in the freshwater ostariophysan Kneria wittei using a combination of techniques (i.e. histology, SEM, skeletal clearing and staining). Specimens ranged in standard length from 10 to 65 mm. Morphological comparisons were also made between males and females, as well as comparisons with closely related taxa. Our study shows that the Kneria opercular apparatus consists of two structures: an opercular cup and a posteriorly positioned opercular flange, each of which is composed largely of connective tissue with keratinized papillae and ridges positioned on the surface. Our results further show that the development of the opercular apparatus is linked directly to the development of the anterior vertebral elements (i.e. epicentral intermuscular bones and neural arches). Understanding the function of the opercular apparatus must therefore include an understanding of its associated skeletal elements. As a result of our morphological observations two hypotheses for the function of the opercular unit are addressed; as an auditory specialization, and as an adhesive device. Copyright     

Age validation,and comparison of otolith,vertebra and opercular bone for estimating age of <Emphasis Type="BoldItalic">Schizothorax o’connori</Emphasis> in the Yarlung Tsangpo River,Tibet

A collection of 514 Schizothorax o’connori was made between August 2008 and August 2009 from Yarlung Tsangpo River to assess the suitability of three bony structures for age estimation. The annulus characteristics of otolith, vertebra and opercular bone were described. Location of the first annulus was validated by daily growth increment (DGI) analysis in the otoliths. Annual periodicity was verified by marginal increment ratio (MIR) analysis in otoliths and edge analysis in vertebrae and opercular bones. Annuli formed, once a year, between March and May for all three bony structures. Otoliths, vertebrae and opercular bones were examined to determine which structure produced the most precise and accurate age estimates in S. o’connori. Vertebrae and otoliths matched closely for the first 21 years of life, while opercular bones appeared to underestimate age. For older fish, the counts diverged and otoliths consistently providing higher age estimates. Sectioned otoliths proved to be the most precise and accurate structure for age estimation. The oldest observed schizothoracine fish was 50, more than twice the longevity previously accepted in S. o’connori.     

Respiratory vasculatures of the intertidal air-breathing eel goby, <Emphasis Type="Italic">Odontamblyopus lacepedii</Emphasis> (Gobiidae: Amblyopinae)

Lacking a propensity to emerge over the mud surface, the eel goby, Odontamblyopus lacepedii, survives low tide periods by continuously breathing air in burrows filled with hypoxic water. As with most marine air-breathing fishes, O. lacepedii does not possess an accessory air-breathing organ, but holds air in the buccal–opercular cavity. The present study aimed to clarify how the respiratory vasculature has been modified in this facultative air-breathing fish. Results showed that the gills apparently lacked structural modifications for air breathing, whereas the inner epithelia of the opercula were richly vascularized. Comparison with two sympatric gobies revealed that the density of blood capillaries within 10μm from the inner opercular epithelial surface in O. lacepedii (14.5 ± 3.0 capillaries mm⁻¹; mean ± s.d., n = 3) was significantly higher than in the aquatic non-air-breathing Acanthogobius hasta (0.0 ± 0.0) but significantly lower than in the amphibious air-breathing mudskipper, Periophthalmus modestus (59.1 ± 8.5). The opercular capillary bed was supplied predominantly by the 1st efferent branchial arteries (EBA1) and drained by the opercular veins, which open into the anterior cardinal vein. Deep invaginations at the distal end of the EBA1 and the junction with EBA2 are suggestive of blood flow regulatory sites during breath-holding and apnoeic periods. It remains to be investigated how blood flow through the gills is maintained during breath holding when the buccal–opercular cavity is filled with air.     

Dielectric relaxation studies on bovine ligamentum nuchae

Dielectric relaxation studies of bovine ligamentum nuchae are reported over the frequency range of 1 MHz to 1 GHz and over the temperature range of 23–48°C. A temperature-dependent relaxation process was observed at low megahertz-frequency with the correlation time of around 40 ns. The result is quite similar to that of a synthetic polypentapeptide (VPGVG) and of α-elastin. The relaxation is proposed to arise in part from the peptide libration within the polypentapeptide of bovine ligamentum nuchae.     

Microstructure and formation of the calcareous operculum in Pyrgopolonctenactis and Spirobranchusgiganteus (Annelida, Serpulidae)

The calcareous operculum of Pyrgopolon ctenactis is composed of spherulitic prismatic structures. The opercular cup consists of regular spherulitic prismatic crystals; the talon has two layers, an inner with an irregular spherulitic prismatic structure (150 μm thick) and an outer with a regular spherulitic prismatic structure (110 μm thick). The outer regular structure has thick (1 μm) organic interprismatic sheets unique in biomineralization of this group, but similar to that of Bivalvia. We infer that control over biomineralization is stronger during the formation of the outer regular layer, with its thick organic interprismatic sheets, than during the formation of the inner irregular spherulitic prismatic structure, without such sheets. In Spirobranchus giganteus, opercular formation differs from that of P. ctenactis. S. giganteus has numerous pores in its opercular plate, and calcification starts with the formation of an outer irregularly oriented prismatic structure followed by an oriented prismatic structure without interprismatic sheets.     

Comparative studies of the cross-linked regions of elastin from bovine ligamentum nuchae and bovine, porcine and human aorta.

1. The preparative Edman degradation of desmosine-containing peptides permitted the isolation of peptides C-terminal to the desmosine cross-links in bovine, porcine and human aortic elastin as well as bovine ligamentum nuchae elastin. This identifies the lysines in the tropoelastin which give rise to the desmosine cross-links. 2. The sequences from bovine aortic elastin were identical with those obtained from bovine ligamentum nuchae elastin but differed from those obtained from the other species. The most striking difference involves the occurrence of phenylalanine in bovine elastin and tyrosine in porcine and human elastin C-terminal to the desmosine cross-links. 3. The sequences of the C-terminal peptides were found to fall into two distinct classes, one starting with hydrophobic residues, the other starting with alanine. It is proposed that thehydrophobic residue prevents the enzymic oxidative deamination of the adjacent lysine e-amino group and this then contributes the nitrogen to the pyridinium ring of the cross-links.     

Homology and evolution of the opercular series in the loricarioid catfishes (Pisces: Siluroidei)

Aspects of the morphology of the opercular region of siluroids (catfishes) were examined to determine the homologies of the opercular bones of loricarioid catfishes, a diverse monophyletic neotropical group. Homology of the component structures was inferred by examination of three criteria: (1) functional relations to the jaw abduction mechanism of primitive halecostome fishes; (2) positional relations to the bones of the suspensorium and the path of the preopercular laterosensory canal; and (3) pattern of development of the preopercular canal and lateral cheek plates of loricarioid catfishes. The majority of siluroids have lost one or more of the preopercular canal exit branches to the skin surface present in most primitive siluroids. A number of specializations of the canal pathway and components of the opercular series have occurred in loricariids. Trichomycterids have the preopercular canal reduced to a short branch from the pterotic. Callichthyids share the presence of a preopercular canal with primitive siluroids, but have lost the communication of the canal between the preopercle and pterotic bones. Callichthyids and scoloplacids share one additional loss of a preopercle exit. The second of two subopercular elements of astroblepids is homologous with the interhyal. Astroblepids and loricariids have lost one additional preopercle exit, the interoperculo-mandibular ligament and the corresponding biomechanical couple for lower jaw abduction. Loricariids have probably lost the interopercle as well. These derived features of loricariids and astroblepids are viewed as specializations for a particular feeding behaviour: scraping algae and detritus from the substratum.     

Structure and mechanical properties of the longitudinal ligaments and ligamentum flavum of the spine

Stress-strain curves were recorded from anterior and posterior longitudinal ligaments and ligamenta flava dissected from pig lumbar spines. Ligaments were examined during extension by light microscopy, to observe crimp structure, and by X-ray diffraction, to determine collagen fibril orientations. Scanning electron microscopy (SEM) was used to examine ligaments fixed at high and low strains. Initial stages of ligament extension involvd alignment of collagen fibrils. Collagen fibrils in unstrained ligamentum flavum were much more disoriented than in the longitudinal ligaments. Thus, fibril alignment, and consequent stiffening, occurred at much higher strains than for longitudinal ligaments, allowing ligamentum flavum to exploit the extensibility of its elastin.