The sexual illusion of the spotted hyena

 So how many times do we hear women talk about the pain of childbirth? Well I’m here to tell you that compared to the hyena, we have it easy. The spotted hyena (Crocuta crocuta) is one of the most unique carnivores when it comes to sexual behaviour. The female is more aggressive than the male, possesses the larger body size and are the socially dominant ones in the clan. This can make for an interesting courtship, especially when it comes to copulation as the female is known to “rule the roost”.

 What is exceptionally unique about the female hyena is that they have no external vagina. In fact the females have genitalia that look like males. The labia is fused together to form what is known as a pseudoscrotum and the clitoris is elongated and fully erected and can act like a penis(Szykman et al, 2007). The female will urinate, copulate and even give birth through the elongated clitoris. This is helped by a hormone that allows for an increased extensibility and elasticity for the central urogenital canal (clitoris) to be dilated enough so the foetus can pass through it (Steinetz et al, 1997).

 As one would imagine, copulation becomes extremely difficult for the males as intromission must be through the urogenital canal. The female can retract the clitoris into her abdomen, allowing the male to insert with more ease. Even then it would appear to be rather difficult for the initial intromission and can be a slow process that can put mating pairs in risk of predation (Szykman et al, 2007). 
 The males are often fearful of courtship and will sometimes avoid opportunities to mate. Behaviours such as approach- avoid and bowing are displayed towards the female and only if the female is accepting of the male will copulation occur. Sadly for the male the more a female is likely to respond to mating the more aggressive she will be towards that male. Researches are still not sure why the female’s genitalia have evolved this way (Szykman et al, 2007), although it does make it almost impossible for forced mating to occur and could possibly be a trait that has evolved by the female solely choosing the genes of her future offspring.


 References:
 Steinetz, B.G., Randolph, C., Weldele, M., Frank, L.G., Licht,P., and Glickman, S.E, 1997. ‘Pattern and source of secretion of relaxin in the reproductive cycle of the Spotted Hyena (Crocuta crocuta)’, Biology of reproduction, Vol. 56, pp. 1301-1306.

 Szykman, M., Van Horn, R. C., Engh, A. L., Bodystone, E. E., and Holekamp, K.E, 2007.‘Courtship and mating in free-living Spotted Hyenas’, Behaviour, Vol. 144, no. 7, pp. 815-846.

Persian carpet flatworms

Persian carpet flatworms

This week’s topic is about the Persian carpet flatworm (pseudobiceros Bedfordi).

The Persian carpet flat worm is a species of marine polyclads located around the tropical reefs of Australia and up through Asia. It gets its name from the colour patterns displayed on its back that look remarkably like a Persian carpet.  Although this seems rather normal, what is unusual is that they are hermaphroditic, meaning each individual carries both male and female sexual organs, including a pair of side by side penises (Milius, 2006).

The behaviour when copulation occurs is known as fencing. They fight each other with their penises trying to stab and insert semen into the back of the other, without been stabbed itself. When one is stabbed by the other, the semen burns a hole through skin, making its way to the eggs.  The reason for the semen being placed on the back is the flat worm has reproductive tracks that open but they do not lead to the eggs.  The flat worm that absorbs the semen then becomes the ‘mother’. This unusual mating ritual is said to evolved due to a lack of partner options, by both obtaining male and female reproductive organs there is a higher chance of each individual been a suitable partner (Milius, 2006).

As for the fencing behaviour, the care of offspring is far more taxing than to be the inseminator. Once copulation is finished, which is said to last for up to an hour, the “father” will simply swim off whereas the “mother” will immediately eat (Milius, 2006).    

References:

Milus, S 2006, ‘Battle of the hermaphrodites’, Science News, Vol. 170, no. 12, pp. 186-188. 

Humble Honey Bee

Hi all

This series of blogs is about unusual reproductive behaviors in animals.

Many animals have strange ways of reproducing, but some animals seem to go above and beyond to pass on their genes.

This week I will talk about the humble honey bee (Apis mellifera).

I’m sure many of you have watched a honey bee, hypnotically gazing as he collects pollen from a beautiful flower but have you ever watched a bee and wondered how It came to be? How in fact did these bees’ parents make that pretty little thing that creates the best thing to ever be applied to a crumpet?

Well it’s not as romantic or sexy as one might think.

Although not in first class with Qantas at 30,000 feet, copulation does occur mid-flight. The drone (male honey bee) will mount the virgin queen and attempt to insert his endophallus (Penis) into the queen’s vagina (Baer  2005, p.1-4). If successful he will then ejaculate his semen and this is when things become really interesting. When the drone ejaculates the action is quite literally explosive. The semen is exploded into the queen with such force, it is said the can be heard by the human ear.

But wait there’s more…….

This poor little guy’s endophallus is also ripped off and left stuck in the queen along with some of his abdomen. Sadly, he dies shortly after.

It is thought that this behavior has evolved more for social bees, especially ones that are polyandry (mate with more than one) as it ensures that the semen stays with the female for longer. Whereas some solitary bees such as the bumblebee (b.terrestris) are known to be monogamous and can mate up to 10 times a day with an average of 30 or so minutes each round. The bumble bee also assures that his semen is staying put and is able to produce a gelatinous like plug that he uses to clog up the bersa copulatrix (Goulson 2003).   

Although this may seem extreme it is a good example of a highly evolved reproduction method.

References:

Baer, B. 2005, ‘Sexual selection in Apis Bee’s’, Institute of Biology, Apidulgie, vol.36, pp.187-200

Goulson, D. 2003, Bumblebee’ s behaviour and ecology, Oxford Biology, Oxford university press, New York.

Picture 1- www.greenanswers.com

Picture2 – www.extension.org