Application of Scanning Electron Microscopy to the Study of Shark Dermal Denticles

Clear, high resolution scanning electron micrographs of shark dermal denticles are essential to allow the study of their morphology and micro-relief. Various techniques were tried to remove mucus and adventitious debris, including KOH, trypsin enzyme, and ultrasonication. In most species examined the best results were obtained with enzyme treatment followed by ultrasonication. For scanning electron microscopic examination it was found that 15 nm gold coating, or more, and 10 kV, or less, had to be employed to reduce charging of the denticles

Elemental and Ultrastructural Characteristics of the Egg Capsules of Nautilus Pompilius

Six pearly nautili (Nautilus pompilius) raised in captivity produced nonviable egg capsules which were examined using scanning electron microscopy ( SE M) and energy dispersive x-ray spectrometry (EDS). Macro and microscopic observations revealed two distinct and separate walls encircling the yolk sac. Both walls exhibited a porous appearance in cross-section. Protein analysis demonstrated the proteinaceous nature of nidimental gland secretions and egg capsule walls. EDS analysis of each wall shows the elemental composition to be identical in both, with each wall containing similar proportions of S, CI, Mg, Na, K, and trace amounts of Ca. X-ray mapping of Na and Cl along each wall surface suggests similar construction of both walls. EDS analysis of the nidimental gland secretions of the adult female nautilus have shown a composition similar to that of the egg capsule

Effects of Acute Tryptophan Depletion on Brain Serotonin Function and Concentrations of Dopamine and Norepinephrine in C57BL/6J and BALB/cJ Mice

Acute tryptophan depletion (ATD) is a method of lowering brain serotonin (5-HT). Administration of large neutral amino acids (LNAA) limits the transport of endogenous tryptophan (TRP) across the blood brain barrier by competition with other LNAAs and subsequently decreases serotonergic neurotransmission. A recent discussion on the specificity and efficacy of the ATD paradigm for inhibition of central nervous 5-HT has arisen. Moreover, side effects such as vomiting and nausea after intake of amino acids (AA) still limit its use. ATD Moja-De is a revised mixture of AAs which is less nauseating than conventional protocols. It has been used in preliminary clinical studies but its effects on central 5-HT mechanisms and other neurotransmitter systems have not been validated in an animal model. We tested ATD Moja-De (TRP−) in two strains of mice: C57BL/6J, and BALB/cJ, which are reported to have impaired 5-HT synthesis and a more anxious phenotype relative to other strains of mice. ATD Moja-De lowered brain TRP, significantly decreased 5-HT synthesis as indexed by 5-HTP levels after decarboxlyase inhibition, and lowered 5-HT and 5-HIAA in both strains of mice, however more so in C57BL/6J than in BALB/cJ. Dopamine and its metabolites as well as norepinephrine were not affected. A balanced (TRP+) control mixture did not raise 5-HT or 5-HIAA. The present findings suggest that ATD Moja-De effectively and specifically suppresses central serotonergic function. These results also demonstrate a strain- specific effect of ATD Moja-De on anxiety-like behavior

Early development of Thyrsitops lepidopoides (Pisces: Gempylidae)

Thyrsitops lepidopoides larvae were caught with Bongo nets in the upper 200 m of the ocean from the coast of southern Brazil during 1975-1978. Based on a serie of 271 specimens ranging from 2.5 to 24.0 mm body lenght, morphological and osteological development of the larvae and juveniles is described. Small larvae (2.5-12.0 mm NL) can be distinguished from all known gempylid larvae by the presence of a distinct melanophore at the base of the dorsal and anal fins. The larvae have well developed dorsal and ventral spines. It is the only gempylid with six preopercular spines and non-serrated dorsal and ventral spines during the larval stage

A critical appraisal of appendage disparity and homology in fishes

Fishes are both extremely diverse and morphologically disparate. Part of this disparity can be observed in the numerous possible fin configurations that may differ in terms of the number of fins as well as fin shapes, sizes and relative positions on the body. Here, we thoroughly review the major patterns of disparity in fin configurations for each major group of fishes and discuss how median and paired fin homologies have been interpreted over time. When taking into account the entire span of fish diversity, including both extant and fossil taxa, the disparity in fin morphologies greatly complicates inferring homologies for individual fins. Given the phylogenetic scope of this review, structural and topological criteria appear to be the most useful indicators of fin identity. We further suggest that it may be advantageous to consider some of these fin homologies as nested within the larger framework of homologous fin‐forming morphogenetic fields. We also discuss scenarios of appendage evolution and suggest that modularity may have played a key role in appendage disparification. Fin modules re‐expressed within the boundaries of fin‐forming fields could explain how some fins may have evolved numerous times independently in separate lineages (e.g., adipose fin), or how new fins may have evolved over time (e.g., anterior and posterior dorsal fins, pectoral and pelvic fins). We favour an evolutionary scenario whereby median appendages appeared from a unique field of competence first positioned throughout the dorsal and ventral midlines, which was then redeployed laterally leading to paired appendages.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/151971/1/faf12402_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/151971/2/faf12402.pd

Spurring or Blurring Professional Standards? The Role of Digital Technology in Implementing Journalistic Role Ideals in Contemporary Newsrooms

This study examines the perceived relevance and implementation of competing normative ideals in journalism in times of increasing use of digital technology in newsrooms. Based on survey and content analysis data from 37 countries, we found a small positive relationship between the use of digital research tools and “watchdog” performance. However, a stronger and negative relationship emerged between the use of digital audience analytics and the performance of “watchdog” and “civic” roles, leading to an overall increase in conception–performance gaps on both roles. Moreover, journalists’ use of digital community tools was more strongly and positively associated with “infotainment” and “interventionism.”

Chromosome evolution in fishes: a new challenging proposal from Neotropical species

We present a database containing cytogenetic data of Neotropical actinopterygian fishes from Venezuela obtained in a single laboratory for the first time. The results of this study include 103 species belonging to 74 genera assigned to 45 families and 17 out of the 40 teleost orders. In the group of marine fishes, the modal diploid number was 2n=48 represented in 60% of the studied species, while in the freshwater fish group the modal diploid complement was 2n=54, represented in 21.21 % of the studied species. The average number of chromosomes and the mean FN were statistically higher in freshwater fish than in marine fish. The degree of diversification and karyotype variation was also higher in freshwater fish in contrast to a more conserved cytogenetic pattern in marine fish. In contrast to the assumption according to which 48 acrocentric chromosomes was basal chromosome number in fish, data here presented show that there is an obvious trend towards the reduction of the diploid number of chromosomes from values near 2n=60 with high number of biarmed chromosomes in more basal species to 2n=48 acrocentric elements in more derived Actinopterygi