Topic
Egg tooth
About: Egg tooth is a research topic. Over the lifetime, 35 publications have been published within this topic receiving 504 citations.
Papers
TL;DR: New observations on developmental stages from the Hill collection are presented, which allow for a more complete description of pre-hatching development of the platypus.
Abstract: Information on the pre-hatching development of the platypus, Ornithorhynchus anatinus, is reliant on a small number of specimens, whose precise age is unknown. Material collected for J. P. Hill and now housed in the Hubrecht International Embryological Laboratory, Utrecht, contributes a major source of specimens. This paper presents new observations on developmental stages from the Hill collection, which allow for a more complete description of pre-hatching development. A feature of the pre-embryonic development of the platypus is the incomplete meroblastic cleavage. A column of fine yolk spheres extends from beneath the embryonic blastodisc towards the centre of a yolky vitellus, as seen in birds. The major expansion of extra-embryonic membranes occurs after the formation of the primitive streak. The primitive streak develops within an embryonal area as part of the superficial wall of the yolk-sac, a feature also shared with marsupials, birds and reptiles. The full-term, subspheroidal, intrauterine egg of the platypus has a major axis of about 17 mm and contains a flat, 19-20 somite, neurula-stage embryo which has prominent trigeminal ganglion primordia. The embryo at this stage is in a period of rapid modelling of the major early organ primordia of the nervous system, cardiovascular system, excretory system, and somite-derived components of the body wall. Soon after laying, five primary brain vesicles are present, the trigeminal ganglia CN5 as well as CN7, CN8, CN9, CN10, CN11 and CN12 are well developed. The alimentary system has an expanded stomach, pancreatic primordia and a gall bladder. Mesonephric tubules are associated with patent mesonephric ducts, which empty laterally into the cloaca. Extra-embryonic membranes at this stage show an extensive chorioamniotic connection that extends through the greater part of the caudal half of fused amniotic folds. The vascularized yolk-sac consists of a superficial yolk-sac omphalopleura and a deep yolk-sac splanchnopleure. The non-vascularized yolk-sac comprises one-quarter of the ahembryonal pole. Some distinctive monotreme features have developed by the mid-incubation period. The head is bent at an acute angle to the main body axis. The blunt upturned snout marks the site of the future oscaruncle and on the maxilla there is a median primordial papilla representing the egg tooth. The eye is open with a partly pigmented retinal ring. The forelimbs have partly separated digits, and the hindfeet are paddles. Just before hatching the upturned snout contains an oscaruncle and a sharp recurved median egg tooth. Forelimbs are pronated with separate digits possessing claw primordia. Portions of the highly vascularized extra-embryonic membranes are attached to the umbilical region and the flattened vesicular allantois has a distal region fused with the chorion. Prominent features of the hatchling are the presence of a bluntly conical oscaruncle and a translucent, horn-like egg tooth. These structures are though to enable the hatchling to extricate itself from the egg shell. At hatching, the forelimbs exhibit clawed digits and are capable of digitopalmar prehension. Hindlimbs are still paddles with digital rays. A prominent yolk-sac navel is present. The newly hatched platypus has an external form similar to that of a new-born marsupial. The early development of the platypus has many major differences to the developmental sequence for humans, which has been categorized by the use of Carnegie Stages. The rate of somitogenesis of the platypus is faster in relation to the central nervous system morphogenesis than seen in humans, and the size of the early platypus embryonal area is massive in relation to that of humans. The unique morphology and function of extra-embryonic membranes in the platypus defies comparative staging with human development. Structures adapted for altricial survival of the platypus hatchling require the acquisition of functional competence at an earlier stage of organogenesis than seen in eutherians, although they are reminiscent of those found in new-born marsupials.
89 citations
TL;DR: It is suggested that hatching is more difficult for a Cuckoo than for a Great Reed Warbler and that Cuckoos possess several mechanisms to overcome the problems of hatching from a structurally strong egg.
Abstract: Brood parasitism represents a unique mode of avian reproduction that requires a number of adaptations. For example, to reduce chances of puncture ejection of their eggs by small hosts, brood parasites may have been selected for laying eggs of unusually great structural strength. However, great structural strength of eggshells should hinder hatching. The goals of our study were to establish if chicks of the Common Cuckoo Cuculus canorus have more difficulty with hatching out of their strong eggs than chicks of species with eggs of similar size, and whether they possess any mechanisms facilitating hatching. To achieve these goals, we compared hatching pattern and selected body characteristics of chicks of the Common Cuckoo with those of another altricial species with eggs of a similar size, the Great Reed Warbler Acrocephalus arundinaceus. Although the rate of pecking was similar in the two species, the Common Cuckoo chicks started pecking earlier in relation to their emergence and consequently required more time and a greater cumulative number of pecks for breaking open their eggs than did young Great Reed Warblers. The two species also differed with respect to the pattern of opening their shells; in contrast to the warbler chicks, which enlarged the original pip circularly, the cuckoo chicks opened the egg by systematically creating a long narrow slit until they emerged. Finally, our study of hatched young revealed several differences; the Cuckoo hatchlings were significantly heavier, had a longer forearm, and their egg tooth was located significantly farther from the tip of the beak. The edge used for cutting through the shell was also significantly longer than that of hatchling Great Reed Warblers. To conclude, our data suggest that hatching is more difficult for a Cuckoo than for a Great Reed Warbler and that Cuckoos possess several mechanisms to overcome the problems of hatching from a structurally strong egg.
55 citations
TL;DR: Embryological data suggest the placement of Zoraptera among the “lower neopteran” or polyneopteran lineage: features supporting this are embryo formation by the fusion of paired regions with higher cellular density and blastokinesis accompanied by full elongation of the embryo on the egg surface.
Abstract: The embryonic development of Zorotypus caudelli Karny (Zoraptera) is described with the main focus on its external features. A small heart-shaped embryo is formed on the dorsal side of the egg by the fusion of paired blastoderm regions with higher cellular density. The orientation of its anteroposterior axis is opposed to that of the egg. This unusual condition shows the potential autapomorphy of Zoraptera. The embryo extends along the egg surface and after reach- ing its full length, it migrates into the yolk. After developing there for a period of time, it reappears on the surface, accompanied by a reversion of its antero- posterior axis, finally taking its position on the ventral side of the egg. The definitive dorsal closure completes, and the prelarva hatches after perforating the chorion with very long egg tooth formed on the embryonic cuti- cle. Embryological data suggest the placement of Zor- aptera among the "lower neopteran" or polyneopteran lineage: features supporting this are embryo formation by the fusion of paired regions with higher cellular density and blastokinesis accompanied by full elonga- tion of the embryo on the egg surface. The extraordi- narily long egg tooth has potential synapomorphy with Embioptera or Eukinolabia (5 Embioptera 1 Phasma- todea). Together with the results from our previous studies on the egg structure, male reproductive system and spermatozoa, the close affinity of Zoraptera with Eukinolabia appears likely, that is, a clade Zoraptera 1 (Embioptera 1 Phasmatodea). J. Morphol. 000:000-
40 citations
TL;DR: During a survey of this species' natural history in the vicinities of Campinas (22o52'S, 46o49'W), Sao Paulo State, field observations were made on the Oviposition behavior, in which after the male left the oviposition site, the female covered the surface of the eggs with soil particles.
Abstract: The Pumpkin toadlet, Brachycephalus ephippium (Spix, 1824), is an orangish daily anuran, which inhabits the litter of the Atlantic Forest of Southeastem Brazil. During a survey of this species' natural history in the vicinities of Campinas (22o52'S, 46o49'W), Sao Paulo State, field observations were made on the oviposition behavior, in which after the male left the oviposition site, the female covered the surface of ali eggs with soil particles. She pressed and rolled each egg against the ground using her hindfeet, until the eggs were indistinguishable from the litter background. A clutch was obtained in laboratory and two others were found in the field. After 25 days of development the embryo possess a big yolk sac, differentiated mouth and a small tail with caudal membranes poorly developed. After 41 days, fingers and toes are fully formed, the tail is relatively smaller than the previous state, the abdomen is large due to the yolk within, and the mouth possess two egg tooth. After 54 days, the tail remains as a small appendix, there is only one egg teeth, and body is densely pigmented. The hatehling oceurred after 64 days of development, the young possess reddish brown coloration, vestigial tail, and no egg teeth.
37 citations
33 citations
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 2021 | 2 |
| 2020 | 5 |
| 2017 | 3 |
| 2016 | 2 |
| 2014 | 1 |
| 2013 | 2 |