6. Chelonians

2019 ◽  
pp. 99-116
Author(s):  
T. S. Kemp
Keyword(s):  
Characteristic Feature ◽  
The Body ◽  
Lateral Undulation

Chelonians are the tortoises, terrapins, and turtles, with the single most characteristic feature being the shell, made up of a small number of very large scales, immovably joined to one another. Inside the shell, the number of vertebrae has been greatly reduced and all traces of the lateral undulation of the body typical of most reptiles have vanished. ‘Chelonians’ explains that this greatly affects other aspects of their anatomy and biology, such as how they walk, breathe, and feed. The roughly 320 species of living chelonians fall into two groups: the Pleurodira (the side-necked turtles) and the Cryptodira, far the most diverse of the two.

scholarly journals Slithering CSF: Cerebrospinal Fluid Dynamics in the Stationary and Moving Viper Boa, Candoia aspera

Biology ◽  
2021 ◽  
Vol 10 (7) ◽  
pp. 672
Author(s):  
Bruce A. Young ◽  
Skye Greer ◽  
Michael Cramberg
Keyword(s):  
Cerebrospinal Fluid ◽  
Cardiac Cycle ◽  
Low Frequency ◽  
Mean Amplitude ◽  
The Body ◽  
Body Waves ◽  
Lower Amplitude ◽  
Lateral Undulation ◽  
Recovery From Anesthesia ◽  
The Relationship

In the viper boa (Candoia aspera), the cerebrospinal fluid (CSF) shows two stable overlapping patterns of pulsations: low-frequency (0.08 Hz) pulses with a mean amplitude of 4.1 mmHg that correspond to the ventilatory cycle, and higher-frequency (0.66 Hz) pulses with a mean amplitude of 1.2 mmHg that correspond to the cardiac cycle. Manual oscillations of anesthetized C. aspera induced propagating sinusoidal body waves. These waves resulted in a different pattern of CSF pulsations with frequencies corresponding to the displacement frequency of the body and with amplitudes greater than those of the cardiac or ventilatory cycles. After recovery from anesthesia, the snakes moved independently using lateral undulation and concertina locomotion. The episodes of lateral undulation produced similar influences on the CSF pressure as were observed during the manual oscillations, though the induced CSF pulsations were of lower amplitude during lateral undulation. No impact on the CSF was found while C. aspera was performing concertina locomotion. The relationship between the propagation of the body and the CSF pulsations suggests that the body movements produce an impulse on the spinal CSF.

scholarly journals The mode of formation of Neumann bands. Part I.–The mechanism of twinning in the body-centred cubic lattice

1928 ◽  
Vol 121 (788) ◽  
pp. 477-486 ◽  
Keyword(s):  
Characteristic Feature ◽  
The Body ◽  
Twin Structure ◽  
Cubic Crystals ◽  
Cubic Lattice ◽  
Cube Face

1. The existence of Neumann lamellæ as a characteristic feature of hexahedral meteoric iron and of the kamacite of octahedral meteorites has been known for many years. The traces of these lamellæ upon polished and etched surfaces were at first regarded as Widmanstätten figures; but it was shown by Neumann that they were distinct from such figures, that they were character­ istic of single cubic crystals, and that their outcrops upon a cube face, which he determined, were inconsistent with the assumption that they were octahedral lamellæ. Neumann, Tschermak and other mineralogists inferred from the geometrical relations between the outcrops of the bands that they were a consequence of an interpenetrating-cube twin structure within the meteorite, of a type known to occur in various minerals, e. g ., in fluor spar.

The Mechanism of Action of a Contact Insecticide

1944 ◽  
Vol 35 (2) ◽  
pp. 161-170 ◽  
Author(s):  
D. N. Roy ◽  
S. M. Ghosh
Keyword(s):  
Oleic Acid ◽  
Characteristic Feature ◽  
Mechanism Of Action ◽  
The Body ◽  
Tracheal Wall ◽  
Fat Globules ◽  
Rapid Diffusion

In order to determine the method of entry of a contact insecticide such as pyrethrum into the body of an insect, studies were undertaken which showed that:—(a) The rapid penetration of the insecticide into the body cannot be effected through the cuticle.(b) When a mosquito has been sprayed with a mixture of pyrethrum extract and oleic acid, the deposition of fat globules around the tracheal trunks is a characteristic feature; this suggests that rapid diffusion of the insecticide takes place through the tracheal wall.(c) Experiments on flies with their spiracles closed indicate that the absorption of pyrethrum, either in the liquid and powdered states, was very slow. This fact indicates that normally pyrethrum enters the body through the spiracle.

Locomotion in derived dicynodonts (Synapsida, Anomodontia): a functional analysis of the pelvic girdle and hind limb of Tetragonias njalilus

2006 ◽  
Vol 43 (9) ◽  
pp. 1297-1308 ◽  
Author(s):  
Jörg Fröbisch
Keyword(s):  
Functional Analysis ◽  
Hind Limb ◽  
Pelvic Girdle ◽  
The Body ◽  
Step Cycle ◽  
Biomechanical Stress ◽  
Hind Limbs ◽  
Gradual Evolution ◽  
Lateral Undulation ◽  
Limb Posture

A general locomotor model for derived dicynodont anomodonts is proposed on the basis of a functional analysis of the pelvic girdle and entire hind limb of the medium-sized Middle Triassic dicynodont Tetragonias njalilus. The joint mobility of the hind limb is examined, and a hind limb step cycle is reconstructed. The data provided in this case study indicate that Tetragonias adopted a highly adducted (upright) hind limb posture during stance and most of its stride. Nevertheless, lateral undulation of the vertebral column must also have contributed to the locomotion of dicynodonts. Character optimization of the traits associated with an upright posture of the hind limb shows a gradual evolution of dicynodont locomotion. The evolution of an upright hind limb posture has occurred several times independently in a number of amniote clades. Within synapsids, the Anomodontia, Dinocephalia, and Theriodontia acquired a parasagittal hind limb gait already as early as the late Paleozoic and early Mesozoic, prior to its evolution in mammals. This phenomenon has previously been explained as being related to an increase in body size as a response to increased biomechanical stress on the limb. This scenario appears plausible with respect to dicynodonts because of the occurrence of megaherbivore-sized taxa in the Triassic, but this study shows that a parasagittal gait had already evolved in the medium-sized basal kannemeyeriiform Tetragonias. Therefore, the vertical support of the body by the hind limbs in medium-sized dicynodonts could have allowed the evolution of the large Triassic taxa in the first place.

scholarly journals What Defines Different Modes of Snake Locomotion?

2020 ◽  
Vol 60 (1) ◽  
pp. 156-170 ◽  
Author(s):  
Bruce C Jayne
Keyword(s):  
Motor Pattern ◽  
Empirical Work ◽  
Current Data ◽  
The Body ◽  
Lateral Bending ◽  
Motor Patterns ◽  
Different Types ◽  
Lateral Undulation ◽  
Left And Right ◽  
Vertical Cylinders

Synopsis Animals move in diverse ways, as indicated in part by the wide variety of gaits and modes that have been described for vertebrate locomotion. Much variation in the gaits of limbed animals is associated with changing speed, whereas different modes of snake locomotion are often associated with moving on different surfaces. For several decades different types of snake locomotion have been categorized as one of four major modes: rectilinear, lateral undulation, sidewinding, and concertina. Recent empirical work shows that the scheme of four modes of snake locomotion is overly conservative. For example, during aquatic lateral undulation, the timing between muscle activity and lateral bending changes along the length of the snake, which is unlike terrestrial lateral undulation. The motor pattern used to prevent sagging while bridging gaps also suggests that arboreal lateral undulation on narrow surfaces or with a few discrete points of support has a different motor pattern than terrestrial lateral undulation when the entire length of the snake is supported. In all types of concertina locomotion, the distance from the head to the tail changes substantially as snakes alternately flex and then extend different portions of their body. However, snakes climbing cylinders with concertina exert forces medially to attain a purchase on the branch, whereas tunnels require pushing laterally to form an anchoring region. Furthermore, different motor patterns are used for these two types of concertina movement. Some snakes climb vertical cylinders with helical wrapping completely around the cylinder, whereas all other forms of concertina bend regions of the body alternately to the left and right. Current data support rectilinear locomotion and sidewinding as being distinct modes, whereas lateral undulation and concertina are best used for defining categories of gaits with some unifying similarities. Partly as a result of different motor patterns, I propose recognizing five and four distinct types of lateral undulation and concertina, respectively, resulting in a total of 11 distinct gaits previously recognized as only four.

scholarly journals A new species of palaeosiphonocladal algae Kamaena gigantea from the Lower–lowermost Middle Mississippian sediments of the Donbas (Upper Tournaisian–Lower Visean)

2021 ◽  
Vol 30 (4) ◽  
pp. 754-761
Author(s):  
Oleh A. Sukhov
Keyword(s):  
New Species ◽  
Characteristic Feature ◽  
Early Carboniferous ◽  
The Body ◽  
Thin Sections ◽  
Middle Mississippian ◽  
Convex Partitions ◽  
The Family ◽  
A New Species ◽  
Tubular Shape

A new species of green paleosiphonocladаl algae Kamaena gigantea from the Lower–lowermost Middle Mississippian sediments of the Donbas has been described. This species was distinguished from other representatives of the genus Kamaena Antropov by its extremely large size, tortuous shape of the thallus and convex partitions. The species belongs to an artificial taxonomic unit of the Kamaenae Shuysky tribe, 1985 , of the family Palaeoberesellaceae Mamet et Roux , a systematic grouping which is still controversial. The attribution of this family to green siphonocladal algae is controversial and quite conditional, the opinions of different authors being based on personal vision, and varying in range from the plant to the animal kingdom. A characteristic feature of the family is the tubular shape , the segments of which are connected by partitions with a large central pore, sometimes with additional small pores. The thallus wall (fossilized remains of the body) is porous or non-porous and has simple or branched pores. It has been emphasized that study of Paleoberezellides in thin sections, the sometimes fuzzy images of the typical material in publications and ignorance of other researchers’ publications have caused confusion and led to the selection of an unreasonably large number of genera and species within the family. It has been noted that in previous works, representatives of this species were mistakenly identified as Anthracoporellopsis Maslov, a genus characteristic of the Lower–Middle Pennsylvanian sediments. This erroneous definition was based mainly on general external similarity, a poorly illustrated description of the type species, and did not take into account the morphological features that were characteristic for the genus. It has been found that representatives of the new species had a rather limited stratigraphic distribution: the Upper Tournaisian (Dokuchaevskian horizon) and the Lower Visean (Hlybokian–Sukhinskian horizons), and the most similar specimens found in the Ural region in underlying Tournaisian sediments were, unfortunately, poorly illustrated and smaller in size and had a narrower thallus. It has been noted that a characteristic feature of the tribe Kamaenae Shuysky, 1985 was the tubular shape, its inter-segmental partitions were perpendicular to the walls and were at the approximately same interval from each other. It has been pointed out that representatives of the new species were found mainly in grainstones, packstones, and wackstones − organogenic-detrital limestones along with such groups of microfauna as echinoderms and ostracods, isolated spicules of sponges and remains of worms. The material for illustrations was mainly taken from the borehole74 (near the village of Rodnikove, Starobeshiv district, Donetsk region) , which most fully revealed the Lower–Middle Pennsylvanian deposits of the southern part of the Donbas. The knowledge of the systematic composition of the Early Carboniferous algoflora has been expanded. This has helped us to conclude that the tribe Kamaeneae Shuysky, 1985 ,includes 6 genera and at least 22 species that were found in the layers from the Early Devonian to the Early Visean of the Lower Carboniferous.

scholarly journals A New Flagellate (Macrostoma mesnili N. Sp.) from the Human Intestine with some Remarks on the Supposed Cysts of Trichomonas

Parasitology ◽  
1910 ◽  
Vol 3 (2) ◽  
pp. 210-216 ◽  
Author(s):  
C. M. Wenyon
Keyword(s):  
Characteristic Feature ◽  
Longitudinal Axis ◽  
Great Difficulty ◽  
The Body ◽  
Human Intestine ◽  
The Bahamas ◽  
Fresh Material

The flagellate to be described in this paper was found in the faeces of a native of the Bahamas who was admitted to the Seamen's Hospital, Albert Dock, in October, 1909. In the course of the examination of the perfectly fresh material it was noticed that numerous flagellates were swimming about. They were taken to be Trichomonas but on closer examination they were seen to differ markedly from these. In the character of their movements there was little to distinguish them from Trichomonas except that the undulating membrane so characteristic of this genus appeared to be absent. The body is pear shaped and there are three long flagella directed forwards from the blunt end of the body. By the lashing of these three flagella the animal is drawn along with the blunt end in advance and at the same time revolves upon its longitudinal axis. A very characteristic feature is the presence of a very large cytostome extending from the base of the three flagella towards the posterior end of the body for about one half to two thirds of its length. The movements of the animals were at first so violent that great difficulty was experienced in making out the details of the anatomy, but as the faeces cooled their activities began to abate. It was then seen that the flagella was as long or longer than the body and that the large cytostome was arranged in a slightly spiral manner: that is to say it did not run directly parallel to the longitudinal axis of the body.

scholarly journals Leishmania infantum in Chinese hamsters

1928 ◽  
Vol 103 (724) ◽  
pp. 252-257 ◽  
Keyword(s):  
Characteristic Feature ◽  
Peripheral Blood ◽  
Leishmania Infantum ◽  
Leishmania Donovani ◽  
The Body ◽  
Large Numbers ◽  
Chinese Hamsters ◽  
General Appearance

The presence of peculiarly localised lesions in hamsters infected with Leishmania infantum was first observed by one of us (E. H.) in two animals kindly sent by Dr. Marshall Hertig. These had been inoculated at Peking on May 25, 1926, with a strain of L. infantum originally obtained in culture from Dr. Nicolle, and known as the "Infantum tunis K. A." strain. Before being sent from Peking, both hamsters were examined by liver puncture and found to be infected. On arrival at Tsinan, on July 17, the peripheral blood of both animals contained numerous parasites. On August 25, approximately fifteen weeks after inoculation, one of these animals was killed, as it had the appearance of suffering from an intercurrent infection. The regions of the distal joints of all four limbs were enormously swollen. The testes, and also the base of the tail, were swollen and suppurating, and one of the testes contained an abscess which was discharging through the scrotum. Examination of the pus from the tail showed the presence of very large numbers of Leishmania . In addition, the margins of the ears and also the nose of this animal showed thickening and ulceration. All other organs of the body were normal, both in size and general appearance, and it is of interest that there was no enlargement of the spleen, which is such a characteristic feature in animals infected with typical strains of Leishmania donovani .

4. How amphibians move

2021 ◽  
pp. 72-81
Author(s):  
T. S. Kemp
Keyword(s):  
Life History ◽  
The Body ◽  
Lateral Undulation ◽  
Basic Biology

‘How amphibians move’ examines how amphibians move. The three kinds of living amphibians share the same basic biology and life history. However, the anatomy of the skeleton and muscles is very different amongst them. This reflects the different ways that the locomotion of the three respective ancestors evolved. The urodeles retained the most primitive way, with a long body and tail. Salamanders and newts use lateral undulation when swimming, but they also coupled it with limbs for walking on land. The anurans became far more modified by shortening the body, losing the tail altogether, and elongating the back legs. Meanwhile, the caecilians evolved a limbless burrowing mode.

Skeletons in Motion, Ancestors in Action: Early Mesolithic Collective Tombs in Southern Belgium

2001 ◽  
Vol 11 (2) ◽  
pp. 147-163 ◽  
Author(s):  
Nicolas Cauwe
Keyword(s):  
Characteristic Feature ◽  
Western Europe ◽  
The Body ◽  
Body Parts ◽  
Upper Palaeolithic ◽  
Late Neolithic ◽  
Neolithic Transition ◽  
Form Part

Collective tombs are a characteristic feature of Neolithic societies of Western Europe. Some recent studies have suggested that they originated from an earlier tradition of individual burials at the Mesolithic–Neolithic transition. The concept of collective burial involving movement and manipulation of bodies and body parts is, however, entirely different. The former tries to preserve the integrity of the bodies and does not acknowledge the stages of metamorphosis of the corpse. The latter by contrast involves observation and assistance in the dissolution of the body. Recent discoveries of Early Mesolithic collective tombs in southern Belgium have underlined the fact that collective burials are far from restricted to Neolithic contexts in Western Europe. They themselves, however, are not merely a potential point of origin for Middle and Late Neolithic collective tombs but form part of a long-standing tradition reaching back into the Upper Palaeolithic.

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