Growth Of Claws Research Articles

The histology and growth rate of Nile crocodile (Crocodylus niloticus) claws.

The histology and growth of reptilian and crocodilian claws (ungues) have been extensively studied; however, Nile crocodile (Crocodylus niloticus) claws have not received adequate attention. Furthermore, age estimations for reptilian claws remain unexplored, despite Nile crocodile claws being used in long-term dietary reconstruction studies, assuming certain age-related patterns. In this study, we investigate the histology and growth patterns of Nile crocodile claws, aiming to infer axes for sampling cornified material for radiocarbon dating and establish age estimations for crocodilian claws. Our findings reveal that Nile crocodile claws exhibit growth patterns similar to other reptilians, presenting as modified scutes/scales with an age profile along the sagittal plane. This profile starts at the basal germ matrix and progressively expands in thickness and age dorsoventrally towards the apex or "tip." Consequently, the oldest corneous material is concentrated at the most dorsal point of the claw's apex. To validate previous dietary reconstruction assumptions, we conducted radiocarbon dating on this region of the claw, which supported the idea that retained corneous material in the claws is typically relatively young (5-10 years old) due to abrasion. Our study contributes insights into the histology and growth dynamics of Nile crocodile claws, shedding light on their use in dietary reconstruction studies and emphasizing the significance of considering age-related assumptions in such investigations.

A universal power law for modelling the growth and form of teeth, claws, horns, thorns, beaks, and shells

BackgroundA major goal of evolutionary developmental biology is to discover general models and mechanisms that create the phenotypes of organisms. However, universal models of such fundamental growth and form are rare, presumably due to the limited number of physical laws and biological processes that influence growth. One such model is the logarithmic spiral, which has been purported to explain the growth of biological structures such as teeth, claws, horns, and beaks. However, the logarithmic spiral only describes the path of the structure through space, and cannot generate these shapes.ResultsHere we show a new universal model based on a power law between the radius of the structure and its length, which generates a shape called a ‘power cone’. We describe the underlying ‘power cascade’ model that explains the extreme diversity of tooth shapes in vertebrates, including humans, mammoths, sabre-toothed cats, tyrannosaurs and giant megalodon sharks. This model can be used to predict the age of mammals with ever-growing teeth, including elephants and rodents. We view this as the third general model of tooth development, along with the patterning cascade model for cusp number and spacing, and the inhibitory cascade model that predicts relative tooth size. Beyond the dentition, this new model also describes the growth of claws, horns, antlers and beaks of vertebrates, as well as the fangs and shells of invertebrates, and thorns and prickles of plants.ConclusionsThe power cone is generated when the radial power growth rate is unequal to the length power growth rate. The power cascade model operates independently of the logarithmic spiral and is present throughout diverse biological systems. The power cascade provides a mechanistic basis for the generation of these pointed structures across the tree of life.

Autoradiographic observations on developing and growing claws of reptiles

AbstractAlibardi, L. 2010. Autoradiographic observations on developing and growing claws of reptiles. —Acta Zoologica (Stockholm) 91: 233–241The present qualitative autoradiographic analysis aims to present the main features of morphogenesis and growth of claws in reptiles. Lizard embryos treated with tritiated thymidine reveal that epidermal cell proliferation in terminal digits is prevalent in the dorsal side and gives origin to the curved unguis of the claw. Less proliferation occurs in the ventral side of the digit tip where the concave sub‐unguis is derived. Adult claws of a turtle show that thymidine‐labelled cells are present along most of the epidermis of the claw, especially at the claw tip. Also, injection of tritiated histidine and proline, indicating active protein synthesis, confirm autoradiographic labelling along most of the epidermis of claws, in particular at the apical tip. The present study indicates that proximal matrix regions, as have been described in mammalian nails, are absent in reptiles. This pattern of claw growth probably derives from that of terminal digital scales. In fact reptilian (and avian) claws are formed from a modification of scales, a different condition from that present in mammals.

Development, comparative morphology and cornification of reptilian claws in relation to claws evolution in tetrapods

The development of claws in different reptiles and their cornification are analyzed using histological, ultrastructural and autoradiographic methods. Claws develop at the tip of digits in relation to the growth of the terminal phalanx and appear as modified scales. The apical epidermis of digit becomes thickened and is associated with a mesenchymal condensation or a dense mesenchyme. The dorsal side of the digit becomes the unguis while the ventral side becomes the sub-unguis. The corneous layer in the unguis is thicker than in the sub-unguis and accumulates hard-keratin while corneocytes remain separated or partially fused. Bundles of hard-keratin tend to accumulate in parallel orientation with respect to the surface and are directed toward the claw tip. The sub-unguis is formed by a softer corneous material and by a much thinner hard-keratin layer. Autoradiography after tritiated thymidine and histidine injection indicates that the growth of reptilian claws occurs along the entire epidermis of the claw. A proximal matrix zone for cell proliferation like in mammalian nails and claws is therefore absent in claws of reptiles. This observation indicates that the pattern of growth of reptilian and probably avian claws is different from that of mammals.

Immunolocalization and characterization of beta-keratins in growing epidermis of chelonians

Beta-keratins constitute most of the corneous material of carapace and plastron of turtles. The production of beta-keratin in the epidermis of a turtle and tortoise (criptodirians) and of a species of pleurodiran turtle was studied after injection of tritiated proline during the growth of carapace, plastron and claws. Growth mainly occurs near hinge regions along the margins of scutes and along most of the claws (growing regions). Proline incorporation occurs mainly in the growing centers, and is more specifically associated with beta-keratin synthesis. Proline-labeled bands of protein at 12–14 kDa and 25–27 kDa, and 37 kDa, in the molecular weight range of beta-keratins, were isolated from the soft epidermis of turtles 3 h after injection of the labeled amino acid. After extraction of epidermal proteins, an antibody directed against a chicken beta-keratin was used for immunoblotting. Bands of beta-keratin at 15–17 kDa, 22–24 kDa, and 36–38 kDa appear in all species. Beta-keratin is present in the growing and compact stratum corneum of the hard (shell) and soft (limbs, neck and tail) epidermis. This was confirmed using a specific antibody against a turtle beta-keratin band of 15–16 kDa. The latter antibody recognized epidermal protein bands in the range of 15–16 kDa and 29–33 kDa, and labels beta-keratin filaments. This result indicates that different forms of beta-keratins are produced from low molecular weight precursors or that larger aggregate form during protein preparation. The present study shows that beta-keratin is abundant in the scaled epidermis of tortoise but also in the soft epidermis of pleurodiran and cryptodiran turtles, indicating that this form of hard keratin is constitutively expressed in the epidermis of chelonians.

FIGHT STRATEGIES DIFFER WITH SIZE AND ALLOMETRIC GROWTH OF CLAWS IN CRAYFISH, ORCONECTES RUSTICUS

Abstract This study examines differences in fighting strategies between small and large male crayfish, Orconectes rusticus. Due to allometric growth of claws, fighting weapons are of disproportionate size in large crayfish compared to those in smaller individuals. Presumably, such differences in the prominence of claws are reflected in differences in the likelihood of injuries, and we thus explored fighting in size-matched pairs of small or large crayfish and assessed associated strategies in situations of conflict. Although fighting reached the highest intensities in a similar proportion of instances in small and large pairs, differences in fighting strategies were evident. Small crayfish escalated more rapidly, fights were settled more quickly, and were resolved overall at lower intensities. This may be explained by lower risks of injury compared to encounters among larger males due to proportionally smaller claws. Larger males thus appear to spend considerably more time in assessing their opponent's fighting ability before each escalation event.

Health and production in improved cage designs

This paper describes the effects of various cage designs on health characteristics such as skeleton strength, plumage and foot condition, mortality, and some production traits such as egg quality and feed consumption. Three major steps in improving cage design and in developing new cage designs are described. Firstly, cage design in general has been improved by comparing different conventional commercial cage designs under the same experimental conditions. Secondly, unconventional design features, such as an abrasive strip to reduce excessive growth of claws or a perch to improve the behavioral repertoire for the hens as well as to strengthen skeletal structure, are described. Thirdly, the effects of fully furnished cages that also include a nest and dustbath for smaller or larger groups of birds are discussed. These designs create an environment in which the problems of conventional cages, such as behavioral restriction, are reduced and the shortcomings of large litter aviaries, such as cannibalism, parasites, and a poor working environment, are improved. Cages with one perch level containing groups of 4 to 10 hens seem more likely alternatives to conventional cages on larger scale farms than litter systems or colony cages for more than 10 birds. This is due mainly to the higher predictability of production, the decreased risk of cannibalism, and improved hygienic conditions.

Axon composition of the proprioceptive PD nerve during growth and regeneration of lobster claws

AbstractA prominent chordotonal organ spanning the propus and dactyl (PD) joint in the chelipeds of the lobster Homarus americanus has the somata of its sensory cells embedded in an elastic strand while their axons collectively travel in a nerve to the ganglion. Electron microscopic examination of the PD nerve revealed several large and many small axon profiles denoting few movement‐sensitive and many position‐sensitive cells. This axon composition typified the nerve in the normally occurring, paired asymmetric crusher and cutter claws, as well as in the experimentally induced, paired symmetric cutter claws. In the asymmetric condition, the crusher nerve had many more axons than the cutter while in the symmetric condition, the numbers were equivalent between the paired cutter claws. In a size‐graded series of lobsters with paired asymmetric claws there was an increase in the number and size of axons in keeping with an increase in claw size. In a newly regenerated claw, the PD nerve was a miniature version of its pristine counterpart with smaller and fewer axons. Moreover, in newly regenerated paired asymmetric claws, the crusher nerve did not have a larger number of axons than the cutter, suggesting that PD nerve has not fully differentiated. The distribution of axons according to size was, however, similar to the pristine nerve in that there were few large axons and many small ones, suggesting that the ratio of large, movement‐sensitive cells to small, position‐sensitive ones in the PD organ is rigidly specified during regeneration and growth.

Avoiding Excessive Growth of Claws in Caged Laying Hens

Abstract A method to avoid excessive growth and breakage of claws, especially observed in caged White Leghorn layers, was developed and studied in three consecutive trials. Such growth may cause accidents by birds getting trapped in parts of the cage. The sharpness of untrimmed claws may also cause injuries among hens as well as scratching handlers' wrists, for example, when the birds are loaded into crates for transport and slaughter. An 8 mm wide strip of abrasive tape was put onto the manure deflector (egg guard) on the feed trough facing inwards the cage (48×40 cm with 1×2″ welded wire floors). Each cage housed 4 hens. The total number of birds was 672 per trial with 336 birds per treatment, NT-birds (in non-tape cages) and T-birds (in cages with tape). Each trial comprised 15 periods of 28 days from 22–82 weeks of age. Egg production, egg weight, live weight, mortality, frequency of cracked and dirty eggs, egg rolling-out efficiency and the condition of plumage, neck front skin, foot and claws were r...

Remarks on the Bifid Claws of the Varying Lemming

One of the most frequently mentioned characteristics of the varying lemming ( Dicrostonyx ) is the growth of enlarged claws on the 3rd and 4th digits during the winter. Hinton (monograph of the voles and lemmings [microtinae] living and extinct. London, p. 139, 1926) pointed out that in summer the claws do not differ greatly from those of other lemmings; but in winter “they are very large, sometimes exceeding half an inch in length, and have the appearance of being double, each of the two fingers seeming to bear two enormous claws, one on top of the other, which are separated at their tips by a more or less deep notch.” It was formerly believed that the growth of bifid claws was a characteristic of only the “old lemmings in winter pelage.” However, Degerbol and Mohl-Hansen (Med. Om. Gronl. 131.) : 14, 1943) have pointed out that young born during the winter also develop bifid claws. In a captive colony of varying lemmings, D. groenlandicus rubricates (Richardson), stemming from Umiat, Alaska, I find that adults, as …

Remarkable Growth of Claws on Foot of a Lyrebird

Remarkable Growth of Claws on Foot of a Lyrebird