Naked Science Forum
Life Sciences => Plant Sciences, Zoology & Evolution => Topic started by: Mrinal Shah on 10/07/2008 22:01:05
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Mrinal Shah asked the Naked Scientists:
Dear Chris,
Nature has created a counter part for almost everything. For male species there is the female counterpart. Why is so that only female species are able to bear offspring. I am aware that male seahorses are an exception to this universal rule. Are there other exceptions as well.
Thanks,
Mrinal Shah
Troy, NY USA
What do you think?
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I think the question has been phrased wrongly. It is about males bearing offspring, not raising them. There are quite a few species where the male rears, or at least shares in the rearing of, offspring. It is especially common among species of fish.
Blumer (1979) noted that 89 of 422 families of bony fish exhibit parental care and in 36 of those it is the male that tends the young.
As far as I am aware, though, seahorses are the only species where it is the male that actually bears the offspring.
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Hi There!
I agree with DoctorBeaver as there is a difference between bearing and raising the offspring.
The first question has to be, if the male seahorse really bears the offspring or if its just more or less breeding the eggs.
And if its really a birth, that the males experience, one should ask, if there is e difference between seahorses and species, that are considered as mouthbrooder. Mostly the males breed the eggs in their mouth and "give birth" to the offspring...e.g. Hexanematichthys seemanni. So could this be another exception from the rule? But maybe the birth of seahorses looks more familiar, because the Babys pop out of the bag at the belly, not out of the mouth.
Something similar could be the breeding of Rhinoderma darwinii (a frog), where the male keeps the pollywogs in its mouth, until they are little frogs.
The other point, raising the offspring:
Of course, its impossible for mammal-males to raise the youngsters without the female. They need the mothermilk. But at other groups of animals, its not that unusual. As DocBeaver said, for a lot of fish raising the offspring is the job of the males. For some birds as well, like Actitis macularius, Hydrophasianus chirurgus, Centropus grillii (I think black-chested coucal is the english common name for this one).
ok, then the real question itself - why do only female animals bear offspring?:
In general, thats just not true. There are also other lifeforms, that are able to reproduce. For example a lot of snails. Mostly there are no males an females, but hybrids. So they are half male, half female...so its more or less a male, thats able to bear. Or a female thats able to fertilize.. whatever.
How else should a bearing male look like? Maybe thats only a question of definition of male an female?
Of course, to produce eggs and bear offspring there have to be special inner organs that mark the animal as a female per definition.
But now, the really interessting part of the answer: There are some animals, that can change their sex, depending on their social environment. Amphiprioninae- the clownfish for example. If the female of a brace dies, the male switches into a female and ist looking for another male. ... ´so this is the perfect example for a bearing male..
Other species are Thalassoma bifasciatum (fish) or some annelidae (worms). And i think, there are also some insects, that can change their sex... but I´m not sure.
cu
aj
ps: sorry, that I could only use scientific names, I don´t know most of the common names in english. And sorry, if my english is hard to read. But I hope you can understand the information I wanted to share anyway ;-)
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Hi There!
I agree with DoctorBeaver
See that? Someone agrees with me - WOO-HOO! [:D]
Thanks for your reply, atrox. It was certainly a lot more informative than mine.
Is your name anything to do with Crotalus atrox?
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Is your name anything to do with Crotalus atrox?
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Darwin's Frog (Rhinoderma darwinii) is a frog native to the forest streams of Chile and Argentina.
It is named after Charles Darwin who discovered it on his world voyage, "Voyage of the Beagle", on the HMS Beagle.
The most striking feature is the way the tadpoles are raised - inside the vocal sac of the male.
http://en.wikipedia.org/wiki/Darwin's_Frog
Unlike the seahorse these frogs are not conceived in vivo.
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See that? Someone agrees with me - WOO-HOO! [:D]
[..]
Is your name anything to do with Crotalus atrox?
*g* Well, I know how to find the most important person in a community and make friends with this one ;)
And yes, somehow my nick is related to this snake....but not only. I use this nickname since 1998, when I first got in contact with the internet.
Back then, I was very interested in scientific names and realised, that "atrox" in different ways often as a part of it for the kind of animals, most people dont like that much (eg. Acanthoscurria atrox, Bothrops atrox, prehistoric Panthera leo atrox and Thylacosmilus atrox, Vaejovis intrepidus atrox, Atrax robustus, even plants (mostly spiny) Cyathea atrox, Euphorbia atrox)
...so I looked it up and i liked it.
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The most important person here is him -> neilep aka Sheepie
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Oh, sorry...thanm I can´t aggree with you anymore, unless its also the opinion of neilep ;-P
*kidding*
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PAH! [:(!]
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Thanks everyone for your responses to the question.
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Thanks everyone for your responses to the question.
You're most welcome