Wednesday, January 25, 2012

Port Jackson sharks breed in Western Port Bay

One of the features of Western Port Bay flotsam is the fact that Port Jackson shark egg cases are fairly common. These screw-shaped cases, which look as if they're made of seaweed, once contained the embryo of a developing shark, attached by a cord to an egg yolk.

In my youth, we called these discarded egg cases the romantic name of mermaid's purses. Almost always they were empty of their developing shark. Sometimes though, they were full of sand.

It's been my life-long habit to pick up anything of interest along the seashore so, over the years, I've picked up hundreds of Port Jackson egg cases -- especially on Phillip Island beaches after storms.

One day, however, I found one that looked intact. Filled with excitement I carried it home where I cut it open on the kitchen bench. Miracle, miracle: inside was my very own shark pup -- Samuel! He was dead but not at all decomposed, so I preserved him in methylated spirits and have him to this day.

The egg case is tough and flexible, and screw-shaped for a reason,. The female Port Jackson shark lays her eggs and wedges each into an underwater rocky crevice, using her mouth, where it will remain stuck until hatching.

Port Jackson sharks (Heterodontus portusjacksoni) are small and do not attack people, therefore can be viewed with affection.

Tomorrow I'm booked in to have three skin cancers removed from my face, under a general anaesthetic. Consequently, I'll not be able to write my blog for a couple of days. But I will be back!

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