Night diving brings out many creatures that we don’t normally see during the day. One of these creatures is very strange looking as it appears to be a sponge but it is scuttling across the reef. These are commonly known as sponge crabs and can all look a little bit different due to the size/colour/shape of sponge on their backs. The sponge crab uses the sponge as a disguise to hide from predators such as other crabs, fish and octopus and the disguise is so good we will usually not see them during the day and only spot them when they start to hunt and move at night. To see sponge crabs looking silly in their sponge hats, come night diving in Bunaken.
The sponge picked by the sponge crab usually is poisonous and doesn’t taste good which means there is less chance for the crab to be found by predators taking a bite from the sponge. During the day the sponge crabs are hiding away in caves and cracks, only coming out at night to scavenge on the dead plants and animals which it finds. It is carnivorous and sponge crabs will open shells with their front claws but will mostly scavenge for dead creatures.
The sponge crab uses its front pincers to cut out a piece of living sponge to fit over its body. It needs to be the right shape so it snugly fits the top of the shell without being awkward to hold on to. To stop the sponge falling off as it walks around it uses its back pair of legs. The back pair are slender and tipped with sharp claws which grip onto the sponge tightly. They have to hold onto the sponge pretty tight not to drop it down the walls in Bunaken while they are climbing around. The sponge on top of them is alive and keeps growing and getting bigger but the crab keeps trimming it to the right size… just enough to hide the crab beneath. They sometimes leave one sponge behind and try a different one.
Sponge crabs are almost impossible to spot unless they move but they don’t like the light from dive lights and tend to move quickly to hide in the crevices. Sponge crabs usually grow up to 15cm wide and we have seen many this big on some of our night diving spots close to Two Fish Divers Bunaken. They really look like crabs with hats or plates on their heads.
Our PADI Divemaster Trainee Alex has been doing his Night Diver Specialty Training this week with instructor Colin. This involves 3 night dives with different skills on each dive and is a great way to also make the most of night diving in Bunaken. Along with many sponge crabs they also spotted blacktip reef sharks, a blue spotted ribbon tail ray, turtles, different species of lionfish, pleurobranch, slipper lobster, crayfish, eels, shrimps, and lots of bioluminescence.
Night diving is a great way to focus on a tiny part of the reef as you search with a flashlight and don’t get distracted by the never ending, panoramic views of the coral walls. This is why we often see so many macro critters at night.
Day diving has been spectacular this week too! Jeff has been blown away by the coral walls and amount of turtles he has seen this week. Christina and John did a combo between here and our Lembeh Resort to make the most of the worlds best walls and spend time in the muck diving capital of the world. Mal and Cathie felt at home with us for the whole week and we couldn’t keep them out of the water, Cathie even did a PADI Discover Scuba Diver and was a natural! Well done and thanks to everyone for coming, see you next time!
Even if you have never tried night diving all you need is a PADI Open Water certification and you can try night diving as an adventure dive. It can credit towards your PADI Advanced Open Water Course too!
Would you like to join us for diving in the world-famous Bunaken Marine Park? Did you know that the world’s best muck diving is located in the Lembeh Strait which is only a short drive away? Combine Lembeh and Bunaken for the best reef and muck diving in North Sulawesi!
If you would like to join us for diving in Bunaken, a combination with Two Fish Divers Lembeh or to take your next level of PADI Course, fill in the contact form below and we’ll get right back to you.
We look forward to welcoming you to tropical Bunaken Island soon!