Kostrena – 2.9.2023

It didn’t take long to be scuba diving back in Kostrena, Croatia again. The weather was nice and not too hot. Although the visibility was quite good there were a lot of particles in the water. I guess this was due to recent storms. It did interfere a bit with my photography but it was all good practice for me.

This time I did 3 dives, all over 1 hour long.

As previously, there were a lot of fish. This time though I didn’t see as many nudibranchs as previously.

Sea slugs and anemones

I will start with the sea slugs section.

First up is the dotted sea slug (Peltodoris atromaculata). These can grow quite large, up to 120 mm. You can spot them on the stony sponge (Petrosia ficiformis) which is their preferred food source.

Peltodoris atromaculata Peltodoris atromaculata Peltodoris atromaculata

The next one is Flabellina pedata.

Flabellina pedata Flabellina pedata Flabellina pedata

And a couple of Flabellina ischitana.

Flabellina ischitana Flabellina ischitana

An interesting fact I learned recently is, that some nudibranchs use parts of their food for their defense mechanisms in interesting ways. A good example is the Flabellina species with its ability to incorporate nematocysts (the stinging cells) from their food for self-defense.

You can find this information and more here:

The last of the sea slugs is the Thuridilla hopei.

Thuridilla hopei

The next image is quite interesting. It is an example of a nudibranch egg mass.

nudibranch eggs

While on the subject of stinging sea animals, there are quite a few organisms in the sea that have that ability.

A good example of this is the anemone. First is the picture of a golden anemone (Condylactis aurantiaca) with a close-up photo. Following is the picture of a fat anemone (Cribrinopsis crassa). The last one is a picture of the cylinder or colored tube anemone (Cerianthus membranaceus). They can come in a wide array of colors.

Condylactis aurantiaca Condylactis aurantiaca Cribrinopsis crassa Cerianthus membranaceus

You can see tens if not hundreds of tiny shrimps of the Leptomysis genus in front of the fat anemone (Cribrinopsis crassa). Symbiosis is quite common under the sea.

Keeping in line with the subject, a couple of pictures of the yellow cluster anemone (Parazoanthus axinellae) growing on the sponge of genus Axinella.

Parazoanthus axinellae Parazoanthus axinellae

Everything else

I decided to take some pictures of the more common species that are everywhere and are usually ignored.

A good example is the hermit crab. The ones in the pictures should be Pagurus anachoretus.

Pagurus anachoretus Pagurus anachoretus

Next a few examples of older juvenile damselfish (Chromis chromis). You can tell how old they are by their color. They start with a beautiful iridescent blue which they slowly lose and finally turn dark gray.

Chromis chromis

Following is a close-up of a tompot blenny (Parablennius gattorugine). This one was quite shy. Sometime they can be quite patient and will stay out in the open for quite some time.

Parablennius gattorugine

And the last picture the red comb star (Astropecten aranciacus).

Astropecten aranciacus


Overall it was another great day scuba diving in Kostrena. It is interesting how things change in just a few weeks.

I am now quite sure I will be back soon.