Clearly, the possibility that Van Peenen's statements are correct exists, but no molecular geneticist would contend that these assertions have been established, in any but a very few cases, which appear at present to be atypical. The educated lavman, for whom this book is intended, will find the author's leaps from the level of the quoted material into sophisticated physical chemistry and back again disconcerting at least, if not completely confusing. It can be said, however, that the authors have assembled an excellent group of illustrations; lecturers in elementary genetics wishing to locate clear illustrations to use as slides would do well to look in this book first.

Animal Tissue Techniques.

Freshwater fish distribution

High-entropy alloys (HEAs) are a novel class of alloys that have many desirable properties. The serrated flow that occurs in high-entropy alloys during mechanical deformation is an important phenomenon since it can lead to significant changes in the microstructure of the alloy. In this article, we review the recent findings on the serration behavior in a variety of high-entropy alloys. Relationships among the serrated flow behavior, composition, microstructure, and testing condition are explored. Importantly, the mechanical-testing type (compression/tension), testing temperature, applied strain rate, and serration type for certain high-entropy alloys are summarized. The literature reveals that the serrated flow can be affected by experimental conditions such as the strain rate and test temperature. Furthermore, this type of phenomenon has been successfully modeled and analyzed, using several different types of analytical methods, including the mean-field theory formalism and the complexity-analysis technique. Importantly, the results of the analyses show that the serrated flow in HEAs consists of complex dynamical behavior. It is anticipated that this review will provide some useful and clarifying information regarding the serrated-flow mechanisms in this material system. Finally, suggestions for future research directions in this field are proposed, such as the effects of irradiation, additives (such as C and Al), the presence of nanoparticles, and twinning on the serrated flow behavior in HEAs.

A Review of the Serrated-Flow Phenomenon and Its Role in the Deformation Behavior of High-Entropy Alloys

The shape of shark teeth varies among species, but traditional testing protocols have revealed no predictive relationship between shark tooth morphology and performance. We developed a dynamic testing device to quantify cutting performance of teeth. We mimicked head-shaking behaviour in feeding large sharks by attaching teeth to the blade of a reciprocating power saw fixed in a custom-built frame. We tested three tooth types at biologically relevant speeds and found differences in tooth cutting ability and wear. Teeth from the bluntnose sixgill ( Hexanchus griseus ) showed poor cutting ability compared with tiger ( Galeocerdo cuvier ), sandbar ( Carcharhinus plumbeus ) and silky ( C. falciformis ) sharks, but they also showed no wear with repeated use. Some shark teeth are very sharp at the expense of quickly dulling, while others are less sharp but dull more slowly. This demonstrates that dynamic testing is vital to understanding the performance of shark teeth.

https://royalsocietypublishing.org/doi/pdf/10.1098/rsos.160141

Modelling tooth-prey interactions in sharks: the importance of dynamic testing.

/pdf/the-teeth-of-non-mammalian-vertebrates-285620jta1.pdf

The teeth of non-mammalian vertebrates

Elasmobranchs exhibit two distinct arrangements of mineralized tissues in the teeth that are known as orthodont and osteodont histotypes. Tra- ditionally, it has been said that orthodont teeth main- tain a pulp cavity throughout tooth development whereas osteodont teeth are filled with osteodentine and lack a pulp cavity when fully developed. We used light microscopy, scanning electron microscopy, and high-resolution micro-computed tomography to compare the structure and development of elasmobranch teeth representing the two histotypes. As an example of the orthodont histotype, we studied teeth of the blue shark, Prionace glauca (Carcharhiniformes: Carcharhinidae). For the osteodont histotype, we studied teeth of the great white shark, Carcharodon carcharias (Lamni- formes: Lamnidae). We document similarities and dif- ferences in tooth development and the microstructure of tissues in these two species and review the history of definitions and interpretations of elasmobranch tooth histotypes. We discuss a possible correlation between tooth histotype and tooth replacement and review the history of histotype differentiation in sharks. We find that contrary to a long held misconception, there is no orthodentine in the osteodont teeth of C. carcharias. J. Morphol. 276:797-817, 2015. V C 2015 Wiley Periodicals, Inc.

Development and microstructure of tooth histotypes in the blue shark, Prionace glauca (Carcharhiniformes: Carcharhinidae) and the great white shark, Carcharodon carcharias (Lamniformes: Lamnidae).

Shark teeth as edged weapons: serrated teeth of three species of selachians.

Teeth are a potentially rich source of character data for phylogenetic studies of living and fossil sharks, but there are many uncertainties about the homologies of tooth loci as well as structural details of teeth in different taxa. Here, we provide new developmental data on the so-called lateral cusplets of the teeth in Lamniformes. We studied the five living species of Lamnidae (Lamna nasus, L. ditropis, Isurus oxyrinchus, I. paucus, and Carcharodon carcharias) and a more basal lamniform, the Sand Tiger Carcharias taurus, using light microscopy and micro-CT scanning. We also studied a single skeletal specimen of the smalltooth Sand Tiger, Odontaspis ferox. Structures in the teeth of juvenile White Sharks, C. carcharias, were interpreted as lateral cusplets in some previous studies, but we show that they develop differently from lateral cusplets in the teeth of Lamna and Carcharias. We conclude that the structures in Carcharodon are not homologous to the lateral cusplets of Lamna and Carcharias taurus a...

https://bioone.org/journals/copeia/volume-103/issue-4/CG-14-109/Homology-of-Lateral-Cusplets-in-the-Teeth-of-Lamnid-Sharks/10.1643/CG-14-109.pdf

Homology of Lateral Cusplets in the Teeth of Lamnid Sharks (Lamniformes: Lamnidae)

This study describes the teeth, dentition, and tooth replacement pattern of the Gulper Shark, Centrophorus granulosus, using histology and micro-CT scanning. Tooth microstructure and the orthodont histotype of C. granulosus are described and illustrated, and tooth morphology is discussed in the context of squaliform phylogenetic studies. Dental characters previously used to study squaliform interrelationships need revision. The dentitions of adult and near-term pups are documented to illustrate ontogenetic changes in tooth morphology as well as the pattern of tooth replacement. Based on the positions of replacement teeth in each tooth file, the replacement pattern of the palatoquadrate dentition is best described as phased sinusoidal replacement. This study also documents the monognathic and dignathic heterodonty of pups and adults, confirming previously published descriptions of heterodonty that have proven to be of taxonomic significance. A revised dental formula is provided that better reflects the too...

Tooth Microstructure and Replacement in the Gulper Shark, Centrophorus granulosus (Squaliformes: Centrophoridae)

This study examines the feeding behaviour and kinematics of three sub-adult sand tiger sharks Carcharias taurus on display at Mystic Aquarium (Mystic, Connecticut, USA). Using high-speed video data from 52 bites, we identify kinematic variables associated with the expansive and compressive phases of the bite. The mean bite duration from the onset of the expansive phase to the conclusion of the compressive phase is mean (± SE) 0.14 ± 0.01 s and across the 10 fastest bites of each individual, the maximum performance average is 0.13 ± 0.01 s. Values of maximum performance do not vary significantly among individuals. When compared with kinematic bite data from species studied previously, these results indicate that body size is not the only determinant factor of bite duration. This study also provides detailed descriptions of feeding behaviours in C. taurus and presents documentation of tooth loss both prior to and during feeding, suggesting that there are multiple mechanisms of tooth loss and use in C. taurus. Finally, we discuss the behavioural and ecological components of prey capture in C. taurus and suggest points of consideration to facilitate interspecific comparisons of prey capture performance in ram-feeding, macrophagous elasmobranchs.

Joshua K. Moyer

Papers

Development and microstructure of tooth histotypes in the blue shark, Prionace glauca (Carcharhiniformes: Carcharhinidae) and the great white shark, Carcharodon carcharias (Lamniformes: Lamnidae).

Shark teeth as edged weapons: serrated teeth of three species of selachians.

Homology of Lateral Cusplets in the Teeth of Lamnid Sharks (Lamniformes: Lamnidae)

Tooth Microstructure and Replacement in the Gulper Shark, Centrophorus granulosus (Squaliformes: Centrophoridae)

Bite performance and feeding behaviour of the sand tiger shark Carcharias taurus