Wednesday, December 26, 2007

Discovery @ Semakau on 25 Dec 2007

Forty first Discovery posting:

Where were you on Christmas Day? Celebrating with friends? Partying? Or somewhere with nature (like a batch of us).

On Christmas day, while Kok Sheng and a batch of shore lovers were at Chek Jawa doing the CJ monitoring project. Some Semakau and Naked Hermit Crabs volunteer guides were at Semakau for their coral workshop practical session (and i was one of them).

Initially, i thought that the plan was to go Kusu for our practical session as first proposed. But i don't know who (most likely to be Luan Keng) pulled a trick out of the hat and had all of us traveling (via boat) to Semakau for this session.

Here are some of us crossing the seagrass lagoon towards the area where we could see lots of corals (picture below).
Before the trip itself, Luan Keng was lamenting that we haven't been seeing any polka-dot nudibranch at Semakau in the last few trips. And so interestingly, the first interesting thing we saw besides corals was a polka dot nudibranch, Jorunna funebris. First 'discovery' (picture below)!

Side note:
I will do another posting for corals soon, as ID-ing Corals was part of our trip's purpose. Anyway, i will do a feature post for nudibranchs for this posting.
Discovery Note (General Information):
1. Nudibranchs, also known as sea slugs, are one of the most beautiful creatures in earth's waters (oceans and seas)
2. To date, there are about over 3000 described species worldwide.

3. Click here to read more about polka-dot nudibranch on the sea slug forum (picture above).

And very soon, we were spotting polka-dots here and there, here's a big one, about 8 to 10cm (picture below)
Discovery Note (More general information):
1. Nudibranchs are benthic organisms, meaning they live on the ocean bottom. They can be found crawling over rocks, seaweeds, sponges, corals and many other substrates.
2. They can be found from the lower intertidal zone to depths of over 700 m.
3. They are located all over the world.

The second type of nudibranch looks like the Phyllidiella nudibranch and this was 5 small ones (about 1cm) close to one another (picture below). Second 'discovery'!Discovery Note (and more general information):
1. Nudibranchs are essentially snails without shells, and their name literally means "naked gills".
2. In most species, the gills are prominently displayed on their dorsal (upper) surface.
3. They have a pair of tentacles (called rhinophores) located on top of their heads, which biologists believe are used as sensory organs to assist in finding food and seeking a mate.

And somewhere i saw this which looks like the
Phyllidiella (picture below) and which was almost as small as the ones saw earlier (picture above)
Discovery Note (Self defense):
1. As nudibranchs, in the course of evolution, have lost their shell, they have had to evolve other means of defense.
2. Some nudibranchs utilize camouflage through color patterns that make them invisible to the eyes of their predators.
3. Others warn off predators by being brightly colored, which serves to remind predators that they are distasteful or poisonous like the

The third type of nudibranch we saw is Ron's favourite, the Gymnodoris rubropapulosa (picture below). Third 'discovery'.
Discovery Note (Diet):
1. Nudibranchs are carnivorous. Some feed on sponges, others on hydroids, others on bryozoans, the list also includes tunicates, barnacles, anemones, corals, sea pens etc.
2. But the most interesting fact is that some are cannibals, eating other sea slugs, or, on some occasions, members of their own species. The
Gymnodoris rubropapulosa is one example of them.
3. Click here to read more about the
Gymnodoris rubropapulosa on the sea slug forum.

Sightings of more polka-dot nudibranchs. This pair in the act of creating the next generation (picture below). Fourth 'discovery'.

Discovery Note (Reproduction):
1. Nudibranchs are hermaphroditic which means they have a set of sex organs for both genders.
2. Nudibranchs typically deposit their eggs within a gelatinous spiral.

Fourth type of nudibranch, the bohol nudibranch, Discodoris boholiensis (picture below). Fifth 'discovery'.

Discovery Note:
1. Click here to read more about the bohol nudibranch on the sea slug forum.

Click here to read the duck's post on the nudibranchs of Semakau we saw on Christmas day.

To warp up, it was a treat going back to Semakau again before the year ends. Thanks Luan Keng and everyone else for making Christmas a very fun day!


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