UNUSUAL REPRODUCTION AND CARE OF YOUNG
INTRODUCTION Evolution in Australia has been developing independently for millions of years, this has lead to many unusual and fascinating reproductive habits among its unique wildlife. Australia is an island and as much as man has tried to conquer its magnificent landscape, he has been unable to wipe all traces of Her hidden treasures. Due to this independent evolution many of the animals which remain are unique and primitive. Their social structure and methods of reproduction have a lot to teach us, there is no glass ceiling in their kingdom, male and female are equal among most species, both sharing the burden of caring for and rearing the offspring. However it is those species which do not share this equality that I have chosen to highlight in the following essay.
The Emu - Fathers at the forefront!
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Emu are prehistoric birds that originated about 80 million years ago in Australia. The emu-bird lives only in mainland Australia. They inhabit eucalypt forests, mallee, heathland, desert shrub lands and sand plains. This way of existence is being threatened by man, due to progressive agricultural methods and yet the emu will continue to survive through their unique habit of the male caring for the young. Emu's usually mate during May-August, the female can be as young as 18 months, she will lay up to twenty greenish- black eggs in a shallow nest. The nest is made of grass, leaves, bark and twigs from the surrounding habitat and is maintained by the male emu for the two months of incubation. This is the beginning of the fathers sacrifice to ensure the birth and survival of his young. Even though there is the possibility that not all of the chicks are even his, as young as they are female emu feel no loyalty to one mate. In the two months which it takes to hatch the eggs the father will rarely move from the nest, he drinks little and will lose up to 20 pounds in weight! When the eggs hatch the father will care for all the offspring for the next seven months or so, with the possibility ranging from 5 to 20 hatchlings he has a lot to do. You may well ask where the female is during these 9 months? Well she cares little for when the eggs hatch and even less for the care of the young birds, she is off finding a new mate and once again has no problem reproducing and leaving the unsuspecting father to care for the eggs. a society where a female’s only job is to copulate and lay the eggs, then lead a care free existence! It is this trait that the female continues reproducing while the male cares for the young that ensures the existence of these birds.
Seahorse stallion turns broody
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Seahorse reproduction really stands out, the males are the ones who become pregnant! However this is not to say that the male is the one who carries all the responsibility, unlike the female emu the female seahorse remains loyal. The relationship of the seahorse is monogamous. The pair will remain together for the duration of the pregnancy. They reinforce their bond daily with ritual dances, tail holding and coordinated greetings. The female never strays further than 100 meters from the male. He is not alone! Mating is an elaborate ritual with dances, colour change and many acrobatic movements. It involves the female inserting her oviduct into the male's brooding pouch. She repeats this action several times with short intervals to avoid exhaustion. When the female rests, the male contorts himself in order to position the eggs in his brood pouch. He then releases sperm into to the pouch and fertilisation can occur. It is now the males turn to rest and he moves away from the female to attach to a nearby plant. During the pregnancy he will move no further than a meter from this area. Once the females oviduct has receded, she can now leave the male. The gestation period of the seahorse can last several weeks according to the species. It is the males job to nourish the eggs. The pouch acts like the womb of a female mammal. The eggs are nourished through a capillary network, nutrients are transferred, oxygen is supplied and there are constant atmospheric changes. This enables the young to adapt automatically to their surrounding habitat at birth. Birth can be compared to that of a mammal also, the male will undergo many contractions. He contorts himself in order to give his pouch a spherical shape. The contractions result in a forward and backward motion which ends in an explosive propulsion of the young from the pouch. This whole process takes up to ten minutes. Once the last seahorse has left the pouch it returns to its normal shape and size. The male has now possibly given birth to up to 200 live young! He will be ready to re-mate within a few hours. It is amazing to find that the seahorse is actually an endangered animal, their main threat comes from man, the seas of Australia are being fished extensively by the Chinese. The seahorse features widely in Chinese herbal medicine, it has been known to treat asthma, arteriosclerosis, incontinence, impotence, thyroid disorders, skin ailments, broken bones.
Gastric brooding frog - against all odds
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The Gastric Brooding Frog was found in Australia. Sadly, not long after their discovery they disappeared and are now believed to be extinct. They were last sighted in 1985.
Gastric Brooding Frogs are notable for their reproductive habits. Although never observed it is evident that the female of the species swallows the fertilised eggs and stores them in her stomach during the gestation period. The breeding season occurs from the late spring through the summer months. The correct temperature is important but moisture and rain are essential for mating to occur. All the male contributes is his sperm, it is the female who carries the young. Once the eggs have been fertilised, the male disappears and the female is left to deal with a clutch of 18-25 eggs. It is her job to now bring them from eggs to tadpoles to the adult form. What would any good mother do? She eats the clutch of eggs. After swallowing the eggs they remain incubated in her stomach for up to 7 weeks. During this time the colourless tadpoles do not feed and neither does the mother. She will give up eating in order to maintain the non-acidic state which the young tadpoles and the egg jelly have created in her stomach. The chemicals the young tadpoles secrete turn off the production of hydrochloric acid in the mothers stomach. This completely stops the digestive process, thereby preventing the digestion of the young. Birth occurs once the young are fully developed within the stomach. The process of birth is accomplished by the female widely opening her mouth and dilating her oesophagus, thus propelling the young frogs from her stomach to her mouth. The young are now free to hop from her mouth to the surrounding habitat. The mother will have no more to do with them. This is surely a huge sacrifice, carry the young within her stomach for 7 weeks and relinquishing the ability to feed in order to ensure her species will survive. It is however evident that her sacrifice is in vain, as it remains to be seen if there are still any live gastric brooding frogs inhabiting their native Australia. Scientists have become increasingly interested in the frogs ability to turn off hydrochloric acid production. They hope to be able to put this knowledge to good use in order to treat people suffering from gastric ulcers.
CONCLUSION
From the above discoveries on the most amazing aspects of alternative reproduction and care of young, I have learned that there are many ways in which a species can adapt in order to survive in an increasingly deteriorating ecosystem. It seems that evolution has played an important role in the maintenance of species that would otherwise have been driven to extinction because of man. The saying survival of the fittest is extremely appropriate for these species not only do they ensure their own survival, they have developed extremely unique ways of doing so. The role between male and female may be reversed or seem illogical to the mind of man but I’m sure there is something we can learn from these creatures and adapt to our society. Anatomical it is not possible for male humans to carry young but there is a great deal we can learn in the role of caring for the young.
REFERENCES
www.abc.net.au/science/ scribblygum www.epa.qld.gov.au/ http://www.deh.gov.au/ http://www.abc.net.au/nature/