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'''Why platypus?''' Greek ''Platus'' = flat or broad, and ''pous'' = foot.
'''Why platypus?''' Greek ''Platus'' = flat or broad, and ''pous'' = foot.


:'''Links:''' [[Echidna Development|Echidna]] | [[Koala Development|Koala]] | [[Platypus Development|Platypus]] | [[:Category:Platypus|Category:Platypus]]
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{{Animals}}
== Some Recent Findings ==
== Some Recent Findings ==
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Revision as of 06:55, 5 November 2011

Introduction

Platypus, 1840 Cyclopaedia

The platypus (Ornithorhynchus anatinus) also called the "duck-billed platypus" together with the 2 echidna groups (short-beaked and long-beaked) are the only 3 surviving genera of the order Monotremata.

The platypus is a unique egg-laying mammal and is not a common animal model of mammalian embryonic development. It lives in freshwater stream systems and is also the only known mammal that produces venom.

The platypus genome has also been recently sequenced 17495919 18464734.

Why platypus? Greek Platus = flat or broad, and pous = foot.

Links: Echidna | Koala | Platypus | Category:Platypus

Animal Development: axolotl | bat | cat | chicken | cow | dog | dolphin | echidna | fly | frog | goat | grasshopper | guinea pig | hamster | horse | kangaroo | koala | lizard | medaka | mouse | opossum | pig | platypus | rabbit | rat | salamander | sea squirt | sea urchin | sheep | worm | zebrafish | life cycles | development timetable | development models | K12
Historic Embryology  
1897 Pig | 1900 Chicken | 1901 Lungfish | 1904 Sand Lizard | 1905 Rabbit | 1906 Deer | 1907 Tarsiers | 1908 Human | 1909 Northern Lapwing | 1909 South American and African Lungfish | 1910 Salamander | 1951 Frog | Embryology History | Historic Disclaimer

Some Recent Findings

  • Sex Determination - ATRX, DMRT1, DMRT7 and WT1[1] "One of the most puzzling aspects of monotreme reproductive biology is how they determine sex in the absence of the SRY gene that triggers testis development in most other mammals. Although monotremes share a XX female/XY male sex chromosome system with other mammals, their sex chromosomes show homology to the chicken Z chromosome, including the DMRT1 gene, which is a dosage-dependent sex determination gene in birds. ... We show that these four genes in the adult platypus have the same expression pattern as in other mammals, suggesting that they have a conserved role in sexual development independent of genomic location."
  • Mammalian Diversity[2] "... Monotremes are remarkable because these mammals are born from eggs laid outside of the mother's body. Marsupial mammals have relatively short gestation periods and give birth to highly altricial young that continue a significant amount of "fetal" development after birth, supported by a highly sophisticated lactation. Less than 10% of mammalian species are monotremes or marsupials, so the great majority of mammals are grouped into the subclass Eutheria, including mouse and human."
  • How did the platypus get its sex chromosome chain? [3] "... Its chromosome complement is no less extraordinary, for it includes a system in which ten sex chromosomes form an extensive meiotic chain in males. Such meiotic multiples are unprecedented in vertebrates but occur sporadically in plant and invertebrate species."

Taxon

Ornithorhynchus anatinus Lineage( full ) cellular organisms; Eukaryota; Fungi/Metazoa group; Metazoa; Eumetazoa; Bilateria; Coelomata; Deuterostomia; Chordata; Craniata; Vertebrata; Gnathostomata; Teleostomi; Euteleostomi; Sarcopterygii; Tetrapoda; Amniota; Mammalia; Prototheria; Monotremata; Ornithorhynchidae; Ornithorhynchus

Development Overview

Platypus mate in July to October, eggs are laid about one month later, eggs hatch and young suckle from their mother, emerging from the burrow in late January to early March.

Gestation is about 2-4 weeks (not exactly known) female lays lays usually 2 (sometimes 3) soft-shelled eggs.

Egg Development after laying, incubation approximately 6 - 10 days.

intrauterine has a major axis (approximately 17mm) and contains neurula-stage (19-20 somite) embryo with prominent trigeminal ganglion (CN 5) 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.

after laying five primary brain vesicles, cranial ganglia (CN5, CN7, CN8, CN9, CN10, CN11 and CN12). Alimentary system has an expanded stomach, pancreatic primordia and a gall bladder.

somitogenesis faster than in humans

Just Before Hatching- upturned snout (contains an oscaruncle and a sharp recurved median egg tooth, for shell removal). Forelimbs (pronated with separate digits with claw primordia).

Hatching- forelimbs with clawed digits and hindlimbs are still paddles with digital rays. A prominent yolk-sac navel is present.

Post-Hatching- (external features from day 0 to 6 months old) development of bill and webbing of the forefeet. Many features show similarities to marsupials (though different in both timing and morphology). (Note- exact age of the specimens relies on ages given to specimens at time of collection)

Young- feed on milk from mother and live in a river burrow for 3 - 4 months.

Differences between Platypus and Human- platypus rate of somitogenesis faster and size of early platypus embryonal area is larger, extra-embryonic membranes have unique morphology and function.

(Data/text above modified from (Hughes Hughes RL and Hall LS, 1998; Manger Manger PR, Hall LS, Pettigrew JD, 1998 and other sources)

Gastrointestinal Tract

Eutherian gastrointestinal system
A recent study has identified differences in the gastrointestinal tract digestive enzymes secreted.[4]

Note that in humans parietal cells produce gastric intrinsic factor, but this is produced in the pancreas of monotremes and other mammals.

Cardiovascular

Platypus ventricular septum

Heart conduction system-bird-monotreme-placental.jpg

Heart conduction system species comparison: Bird, Monotreme and Placental[5]

Genome

Platypus karyotype.jpg

The platypus karyotype (2 n = 52) consists of 21 autosomes and 10 sex chromosomes (5X's and 5Y's in male and 5 X-pairs in female).[6]


Emergence of traits along the mammalian lineage.[7]

The platypus mitochondrial genome was sequenced in 1994.[8]

The nuclear genome first draft sequence was released in 2008.[7]

"This monotreme exhibits a fascinating combination of reptilian and mammalian characters. For example, platypuses have a coat of fur adapted to an aquatic lifestyle; platypus females lactate, yet lay eggs; and males are equipped with venom similar to that of reptiles. Analysis of the first monotreme genome aligned these features with genetic innovations. We find that reptile and platypus venom proteins have been co-opted independently from the same gene families; milk protein genes are conserved despite platypuses laying eggs; and immune gene family expansions are directly related to platypus biology."


Genetic Divergence

Divergence of mammalian species dentin phosphoprotein This graph shows the phylogeny and divergence timescales of mammalian species using the dentin phosphoprotein (DPP) gene sequence comparison.[9]

Note the early timescale divergence of the platypus species relative to the other mammalian species.

Sex Chromosomes

The total diploid number of chromosomes is n=52 and in the males ten sex chromosomes form an extensive meiotic chain.[3]

Five male-specific chromosomes (Y chromosomes) and five chromosomes present in one copy in males and two copies in females (X chromosomes) These ten chromosomes form a multivalent chain at male meiosis, adopting an alternating pattern to segregate into XXXXX-bearing and YYYYY-bearing sperm. .

Spermatozoa Development

  • monotreme spermatozoa undergo some post-testicular maturational changes
    • acquisition of progressive motility
    • loss of cytoplasmic droplets
    • aggregation of single spermatozoa into bundles during passage through the epididymis
  • epididymis of monotremes is not adapted for sperm storage
    • absence of platypus genes for the epididymal-specific proteins
    • most abundant secreted protein in the platypus epididymis is a lipocalin (homologues are the most secreted proteins in the reptilian epididymis).
    • lipocalins are a group of extracellular proteins able to bind lipophiles by enclosure within their structures and minimizing solvent contact.

Information based on[7]

Immune System

For details read the recent article.[10]

  • Monotremes have IgM, IgG, IgA and IgE
  • do not use IgY
  • has multiple Ig heavy chain subclasses
  • at least two IgG and two IgA sub-isotypes

References

  1. <pubmed>19874722</pubmed>
  2. <pubmed>16478607</pubmed> | CSIRO
  3. 3.0 3.1 <pubmed>16344965</pubmed>
  4. <pubmed>18482448</pubmed>
  5. <pubmed>17104326</pubmed>
  6. <pubmed>17822525</pubmed>| BMC Evol Biol.
  7. 7.0 7.1 7.2 <pubmed>18464734</pubmed>| PMC2803040 | Nature
  8. <pubmed>7932783</pubmed>
  9. <pubmed>20030824</pubmed>
  10. <pubmed>14667846</pubmed>

Reviews

<pubmed>9720108</pubmed> <pubmed>9720109</pubmed> <pubmed>8371093</pubmed>

Articles

<pubmed>18464734</pubmed> <pubmed>16244467</pubmed> <pubmed>15534209</pubmed> <pubmed>17104326</pubmed>

Books

  • Platypus: The Extraordinary Story of How a Curious Creature Baffled the World (Hardcover) by Ann Moyal (Amazon Link)
  • Platypus (Mondo Animals) (Paperback) by Joan Short, Jack Green, Bettina Bird, Andrew Wichlinski (Illustrator) (Amazon Link)

Search PubMed

Search Feb2006 "Platypus development" 303 reference articles of which 5 were reviews.

Search PubMed: Platypus development | monotreme development

Additional Images

External Links

External Links Notice - The dynamic nature of the internet may mean that some of these listed links may no longer function. If the link no longer works search the web with the link text or name. Links to any external commercial sites are provided for information purposes only and should never be considered an endorsement. UNSW Embryology is provided as an educational resource with no clinical information or commercial affiliation.



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Historic Embryology  
1897 Pig | 1900 Chicken | 1901 Lungfish | 1904 Sand Lizard | 1905 Rabbit | 1906 Deer | 1907 Tarsiers | 1908 Human | 1909 Northern Lapwing | 1909 South American and African Lungfish | 1910 Salamander | 1951 Frog | Embryology History | Historic Disclaimer

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Cite this page: Hill, M.A. (2024, March 28) Embryology Platypus Development. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Platypus_Development

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© Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G