Scuba Diving

Baby Zebra Batfish

/ Maarten De Brauwer / 1 Comment

The next species which I think deserves more attention than it currently gets, is the (baby) Zebra batfish (Platax batavianus). It is also known as the Batavia batfish, Humphead spadefish and probably a dozen or so other names. The reason I’ve taken a liking to this little guy is not just because it is an awesome little critter, but also because I finally got to see it after having it on my wish list for about 7 years.

Batavia batfish adults are not very different than most other batfishes, if possible they might actually be a bit uglier, in any case, they don’t really stand out. They do stand out however in the juvenile phase, and they do so rather magnificently! Check out this great picture Luke took a few days ago:

Zebra batfish (Platax batavianus)

Zebra batfish (Platax batavianus)

In the batfish genus, it is quite a common occurrence for the juveniles to differ greatly from the adults. As not to distract you in this post dedicated to the Batavia batfish, here are links to the juvenile Orbicular batfish and Pinnate batfish. They are almost as amazing as the Zebra batfish, so I do encourage to have a look at them after reading this post!

Zebra batfish are named for their juvenile pattern, which helps distort their outline, again providing camouflage to the rather slow moving fish. Very little is known about the ecology of this species (surprise surprise!) but these are a few things I managed to find from the literature:

Zebra batfish, large juvenile (12 cm)

Zebra batfish, large juvenile (12 cm)

  • Baby batfishes tend to settle on the reef (change from open water swimming, transparant larvae to coloured fish living on reefs) when they are between 1.5 cm and 3 cm. Before they settle on the reef, batfish larvae mostly swim close to the surface of the water.
  • Baby batfishes seem to be mostly attracted to the base of the reef (where the reef meets the sand) or to mangroves.
  • Baby Zebra batfish are usually found on the sand, hiding close to feather stars, sponges or soft corals.
  • Batfishes are mostly herbivores, feeding on algae by day. Some species also feed on zooplankton (small animals floating in the water) at night.
  • Juvenile batfishes (all species) are popular in the marine aquarium trade, but they are very hard to keep alive, so most die within a few days/weeks. If they do survive to adulthood, the often get to big for their tank (over 50 cm) and are subsequently “discarded”. Which is why some batfish species are now an invasive species off the coast of Florida
Baby Zebra Batfish (Platax batavianus)

Baby Zebra Batfish (6 cm)

Conclusion for this little critter? It is better to be patient and go to the right places to see it in the wild instead of getting it in your aquarium. Not only will you be doing reefs a favour, seeing these gorgeous fish in the wild makes for a much more rewarding experience than just buying one.

Oh, and if you were wondering where it got its scientific name, Batavia is the old name for Jakarta (the capital of Indonesia). When Cuvier described the species (1831), this was how Jakarta was known, so I am guessing the original specimen he used to describe this species was either caught or shipped from anywhere near Jakarta.

Psychedelic nightdiving fun!

/ Maarten De Brauwer / 11 Comments

I have been doing quite a lot of night dives recently. Those who know me from when I was still working as a dive instructor might be a bit surprised by this, as I never use to be the biggest night dive enthusiast around. There are two reasons I’m swimming around in the dark a lot recently:

  1. Night diving in Lembeh Strait (and Indonesia in general) is pretty amazing
  2. I’ve been playing with a new toy that makes it all a bit more interesting: a high intensity blue light torch. This torch, combined with a yellow filter allows a diver to see “biofluorescence”
Zombie Seahorse (Hippocampus histrix)

Thorny seahorse – zombie version

So as an excuse to post some very psychedelic photos, let me tell you a bit more about biofluorescence under water.

It is important to realise that biofluorescence is NOT the same as bioluminescence. The former needs an external light source (the sun, a dive torch,…), the latter means that the animal itself produces light. For more info on the differences, check out the site of the Luminescent labs.

Devil Scorpionfish

Devil Scorpionfish (Scorpaenopsis diabolus)

Biofluorescence under water has been described as early as 30 years ago and was first noted in corals and anemones. It has been used for years in coral research that looks at coral growth, diseases and bleaching. More recently however, people have started noticing that many more animals than just coral are fluorescent. A paper in 2008 described how many goby species show red fluorescence. Other publications have described fluorescence in many invertebrates such as mantis shrimps, crabs, worms, nudibranchs,… But I really got interested last year when a paper was published that described how fluorescence in fish was much more widespread than previously assumed. The reason it caught my attention is because it seems to be particularly common in “cryptically patterned species”, many of which happen to be the camouflaged little critters I’m so interested in.

Juvenile Whiptail (Pentapodus emeyrii)

Juvenile Whiptail (Pentapodus emeyrii)

Fluorescent nudibranch (Trapania scurra)

Fluorescent nudibranch (Trapania scurra)

So I got myself the necessary equipment and now I am trying to figure out what exactly fluoresces here in Lembeh, and maybe even getting a clue about why they fluoresce as well. There are a few theories out there: it could be used as a form of communication, it might be some sort of camouflage, it could even just be pure coincidence and we might be looking at a cool, but irrelevant quirky thing that evolved but serves no real purpose (I highly doubt this). Fish see the world differently than we do and many species can actually observe UV-light and fluorescence, which would lead me (and other researchers) to believe there is some function there. To prove these functions however, a lot more research and experiments are needed.

Shrimp trying to hide behind algae

Shrimp trying to hide behind algae

What matters most for this blog post, is that it looks rather amazing and that it shows a different, little known side of the underwater world. In case you were wondering, or doubting what you are seeing, none of the pictures in this post have been photoshopped beyond cropping and cleaning up some backscatter.

Acropora coral

Acropora coral

Copepod constellation

Copepod constellation

Tube anemone

Tube anemone

If you want to know more about how fluorescence works and how to take fluoro pictures yourself, this site is a good place to get started.

Thorny seahorse (Hippocampus histrix)

Thorny seahorse (Hippocampus histrix)

Winged Pipefish

/ Maarten De Brauwer / 4 Comments

As the research that I am doing looks at some of the strangest critters you can find in the ocean, it seems only right to give them a space on this blog. The little guy who kicks of the page is a little known pipefish: the “Winged Pipefish”.

Adult Winged Pipefish

Winged Pipefish

While doing surveys on the Critters@Lembeh housereef, I found a large (15cm) Winged pipefish (Halicampus macrorhynchus) chilling out on a patch of rubble. I have seen this species a few times before on dives in Indonesia, and always liked it a lot, even if you don’t hear or read about them very often. Maybe I like them just because it’s less of an in your face – “take a picture of me now, I’m AWESOME” – kind of critter than some of the more popular ones, but they still manage to be pretty cool creatures. As with most other pipefishes, little is known about their life history and behaviour. Besides the original description, I found a grand total of 0 (=zero) scientific papers that focus on the ins and outs of this amazing fish…

Juvenile Winged Pipefish

Juvenile Winged Pipefish

So here is what we do know: The juveniles are beautiful, mimicking algae or bits of seagrass. The tiny juvies have got large appendages resembling wings, hence the name. The wings don’t serve many other purposes besides looks (more on that later). They can be found on sand or rubble, often in areas with a lot of plant debris or seagrass. I think they are cutest juvenile pipefish you can find, but they are a very rare find, in 12 years of diving I only ever managed to find a single one.

With age the wings appear to get smaller (they grow into them). In big adults the only things that can be seen are small skin flaps on the side. The adult pipefish still look quite amazing, and can display all kinds of colours, ranging from brown to yellow to pink. At this stage, they are more commonly found on coral rubble or coral reefs.

The biggest adults can get overgrown with algae and are extremely well camouflaged, like the one on the housereef. The big ones I’ve seen were always on coral rubble and looked kind of gritty and tough (as far as pipefishes can look tough).

Halicampus macrorhynchus

Halicampus macrorhynchus

For those if you interested in finding or photographing one of these guys, Winged Pipefish range from the Red Sea to as far as Hawaii and Panama. Look in rubble, sand or seagrass patches between 3m and 25m.

Spot the pipefish...

Spot the pipefish…

Oh, and the function of the skin flaps and wings? It is assumed that they help to break up the shape of the fish, making it even harder to find for predators or divers.