Friday, July 6, 2012

Biology Lesson

When walking on the beach as often as I do, you notice things. Things that change. Something is different.

On this day I noticed a dark wavy line, stretching across the beach.

Looking more closely I noticed that it was much courser sand, pieces of shell, little bits of vegetation, sea glass (haven't found glass in a long, long time). This was all tone in tone, browns, beiges and creams.

As I walk along I start seeing tiny spots of purple and wonder what the heck is that? 

I bend down and see that it's little purple shells and they were all over a small stretch of the beach. Hundreds of them.

So tiny and yet so much detail!

Love the warm glow of the morning sun.

Now wait a minute,  here was something different. This one seemed to have a float, just like a Portuguese Man of War jellyfish.

Let me blow this up for you

Got me thinking of an acquaintance of mine, John Hoover. 

John wrote "The Books" on Hawaii sea life.  Tirelessly gathering information on fish and invertebrates. So I dropped John a quick note, with photos, asking what this might be. Here is his response. 

"The purple shells are called "Violet Snails" - Janthina janthina and they eat Portuguese Man of War jellyfish." 

And just as I thought, he goes on to say that if the wind changes they get swept on shore.

Now that I had a name I researched a bit more and found this here:

The violet snail is a marine gastropod that spends its whole life drifting on the ocean surface in warm seas, floating on a bubble raft of its own making. It feeds on jellyfish, such as the By-the-wind-sailor, Velalla velalla, or the Portuguese man-o-war, Physalia physalis. It starts life as a male and becomes female over time.
The violet snail, Janthina janthina, also known as the violet shell snail and purple bubble raft snail, is holopelagic, meaning it spends its entire life cycle on the open sea. It secrets mucus from its foot which binds bubbles together in a raft, on which it floats freely on the ocean, in equatorial and temperate waters. Its shell is 3-4 cm in size, light and fragile, and is a dark purple at the widest part, fading to a light purple at the narrow top. Its body ranges from dark purple to black.
Violet snails are protandric hermaphrodites, meaning they are born male and develop into females over time. Fertilization is internal, but males lack a penis, so there is no direct mating. Instead, the males release their sperm into a case that drifts to a female, where the sperm fertilizes the eggs. The eggs develop internally and are born live, with the tiny purple snails immediately able to build their own rafts. They use their feet to agitate the water, creating bubbles, which they bind together with mucus. If the bubble raft ever breaks apart, the snail will sink into the ocean and die."

Lastly, I took a pic of one of the shells next to a pin. Just so you get a feel for the size.

And that, was your biology lesson of the day!

Aloha a Hui Hou! 

1 comment:

  1. Hey Heidi! Thanks for your sweet comments. I've seen those purple shells on beaches before but never researched what they were. Thanks for the lesson!!



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