Naked Science Forum
Life Sciences => Plant Sciences, Zoology & Evolution => Topic started by: Digomaje, Kgomotso on 27/11/2011 14:30:03
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Digomaje, Kgomotso asked the Naked Scientists:
Which animal or animals 'vomit' their offspring?
What do you think?
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Some species of Cichlids, known as ‘mouthbrooders’ and a few other such fish, collect the new laid eggs in their mouth to incubate them. Once hatched, the fry swim free.
But I think the animal you may have in your mind are the Australian Platypus Frogs (Rheobatrachus silus ). Once laid and the eggs fertilised by the male, the female would swallow them and incubation of the eggs and tadpoles (pre-juveniles) would take place in a buccal sac in the stomach. Juvenile frogs would then be regurgitated.
Sadly these frogs are now thought to be extinct. The last reported sighting being in the early 1980’s.
Sorry it took a while to answer your question: It stirred a faint memory in the back of my mind, but it took a while for me to recall it to the front. Anyway, I did manage to find a clip (if rather short) on YouTube. Look at this (http://www.youtube.com/watch?v=pORNSnMSsgM)
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An interesting question regarding 'mouth birthing'. When we say animals, we refer to a broad kingdom of species with a huge variety of form and diversity.
If we look at mammals, their birth strategies fall into three broad categories;
Oviparous mammals are the egg-laying species such as the duck-billed platypus.
Metatherians give birth to young who are not yet fully developed or independant and reqiure a period of 'incubation' within the protective pouch of the mother, (as with the case of Kangaroos and other marsupials) where they are likely to suckle milk while further developement occurs.
The remaining group, Eutherians ('true mammals'), are also known as placental mammals due to their more developed uteral/placental cycle of developement within the womb. Eutherians give birth to more or less independant young (although levels of parental care required/given after birth vary greatly between species).
In all instances reproduction and development is confined soley to the womb and there would be no option or possibility of a 'mounth birth'.
This of course is only the case for mammals, other animals have many varing strategies. As the commenter above noted, some species of fish and amphibians will carry eggs or even hatched young in their mouths as part of their parental care strategy. However this is obviously not the same as truely giving birth.
Other groups of animals however may have greatly different stratagies. Many much simpler animals (in a biological sense) do not possess reproductive systems such as a uterus/womb and rely on processes such as budding, whereby the relevant reproductive cells are extruded through the animals' membraous outer layer. I am no expert but I am also aware that some groups of animals such as Hydrazoa (which inlcude jellyfish like animals) have a single appature/organ for both ingestion and excretion and may (though I am far from certain of this) involve the same organ in reproduction. It should be noted however that these animals generally reproduce by releasing gametes in swarms into the ocean, where they encounter the relevant cells from other individuals and there is therefore no internal developement of offspring.
For many species of protozoa (although as their name suggests, they are not actually members of the Animal kingdom), their method of nutrient absorption also (usually) involves the envelopement of their food, this could possibly be seen asgiving birth via the same organ as feeding (i.e. the outer membrane) as many protozoa reproduce via mitiosis, producing whole, identical offspring. Obviously this is nothing like actual 'mouth-birth', though it is and interesting synonym.
The same could again be said of bacteria, who also reproduce through division.
I suppose the general thrust of this post is that as far as I am aware (which in no way confirms anything I must add), there is no species of animal which would actually give birth (in a mammalian sense) through its mouth. This largely relies however on the specific definition of 'mouth', which usually implies a specific apperture for ingestion of food and for respiration, etc. Obviously life on Earth is vast in its diversity of form and function and there is a great deal of room for variation.
I apologise if this post seems rambling and messy, I have just been typing as thing come to mind and reproduction is not really my speciality. I hope this has been at least interesting if not etirely helpfull.
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There were a number of spelling and gramatical errors in my last post.
Apologies.
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This was supposed to be in response to the question in the subject line, which someone had previously asked but was somehow posted as a new question!
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I apologise if this post seems rambling and messy,
On the contrary: I thought it was well structured and informative.
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Don seems to have the answer about hatching through the mouth, and I'm doubtful that any species has a direct connection between the uterus and the mouth, but one is always surprised by nature.
Thanks for the explanation Devilmunkey. I agree that the answer is quite informative. Earlier today I requested that Geezer merge the two disjointed topics as you apparently intended. Thanks Geezer.
I was looking at sharks the other day. There seems to be some extraordinary variation in shark reproductive practices.
Some sharks lay a eggs (oviparous), generally an odd shaped egg sack called a mermaid purse.
Some sharks retain the eggs internally, and give live birth, but otherwise don't give the eggs nutritional support (ovoviviparous). In some cases, the dominant hatchling eats the rest of the brood, with two siblings born in separate uteruses.
Some shark embryos develop a placenta for nutritional exchange (viviparous), at least during a period of the gestation cycle.
But, alas, while some of the oviparous sharks will take their eggs in the mouth and plant them in crevices, they don't actually give birth through their mouths.
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Thanks for sorting my post out CliffordK, I'm rather new to this whole thing.