05 February 2011

Kranji mangroves: cool spiders and colourful crabs

Decided to check out Kranji mangroves again as it was such a bright sunny day!
Oops, the tide is really high when I arrive!

The tide is so high it nearly touches the base of the Main Bridge! But this makes it much easier to see and photograph the fishes! Finally, a better look at the Striped nose halfbeak (Zenarchopterus buffonis) and now I understand its common name! It does have a stripe on its nose! Which is hard to see when the fish is far away.
Among floating leaves and twigs,
this surface-dwelling fish is sometimes overlooked.
There were some big fat Banded archerfishes (Toxotes jaculatrix) and small ones too, hanging around near the sluice gate.
Also a school of these small fishes (about 10cm long). Mullets (Family Mugilidae)? I also saw from a distance, some Garfish or Needlefish (Family Belonidae), but they didn't come close enough for a photograph.
The little fishes were swimming in circles.

When we headed for the mangroves, the water was still high but rapidly falling. We managed to successfully check up on the various plants there. One of the trees here that I've not noticed properly are the large tall old Teruntum trees. I remember Dr John Yong sharing that Teruntum is a feature of this mangrove.

This old gnarly tree with fissured bark turned out to be Teruntum putih (Lumnitzera racemosa)! I found out only after processing the photos of the canopy when I got home. Awesome to see one so tall! Those I've usually seen are short bushes.
Once I started looking, I realised there were many of these trees.
There are lots of interesting animals in our mangroves. Such as spiders! It seems to be the season now for the Golden orb web spider (Nephila maculata). The male is tiny compared to the huge female.
This is the Mangrove St. Andrew's Cross spider (Argiope mangal) which was described by Joseph Koh, our dear friend and spider expert who wrote the Guide to Spiders of Singapore. Only the female Argiope mangal builds webs. These contain only 2 white zig-zag lines, called stabilimentum. Argiope versicolor, which is found inland, makes the "full" cross with 4 stabilimentum.
A little jumping spider was hiding under a leaf. It looks like the Yellow-Lined Epeus (Epeus flavobilineatus) which is reported from our mangroves and which Joseph Koh noted as a new record for Singapore. Apparently the male has this kind of 'punk hairdo' on the top of its head.
The mangroves is full of crab! Most are well camouflaged but often have colourful body parts. This Tree climbing crab (Episesarma sp.) has red tips on its white pincers.
Another tree climbing crab with white pincers.
The colourful Face-banded crabs (Perisesarma sp.) were everywhere!
A pretty stout purple crab that I haven't seen before. It was quite large, the body was about 8cm across.
Fortunately, once again, Jerome is here to find and tell me more about fishes. He noticed this tiny banded fish. Could it be the Bumblebee goby (Brachygobius kabillensis)?
There were some tiny fishes with big eyes, schooling in the pools. Could they be Javanese ricefish (Oryzias javanicus) or Priapus fish (Neostethus sp.)?
There were also all kinds of mudskippers, skipping AWAY from us. Including some very large and splashy Giant mudskippers (Periophthalmodon schlosseri).

Some sort of insect larva has been eating its way through this mangrove tree leaf throughout its caterpillar life. Possibly the appropriately named Leaf miner moth (Phyllocnistis sp.). It tunnels its way through the leaf, without breaking either the upper or lower leaf surface. When it first started, the tunnel is thin and narrow, becoming wider as it grows larger, finally ending in a folded leaf edge where it stopped eating to pupate, then breaks through the leaf to emerge as a winged adult.
I usually ignore birds, but the loudly cackling Collared kingfishers that were busy around us were hard to ignore. We also saw a quiet little woodpecker on a big old mangrove tree.
Our mangroves are full of interesting animals!

Jerome noticed lots and lots of these tiny translucent spheres among the moss-like hairy green seaweed that forms carpets under the mangrove trees. The spheres are hard and can't be compressed. I'm not sure what they are. Are they artificial? Plastic beads? Oh dear.
Alas, this shore (and many of our other shores) is endlessly inundated by litter that floats in with every high tide.
More litter!
Fortunately, International Coastal Cleanup Singapore works tireless to educate about marine litter. Kranji is one of the major sites for the Cleanup.


  1. The purple stout crab looks like a Mound Crab (Sarmatium germaini), a sesarmine.

    The image on A Guide to The Mangroves of Singapore II shows the brown version.

  2. Can be ''Plastic beads'' be small/baby jelly fish out-of-water? I remember i saw something like that during one of the prawn farm tour at buloh.

  3. Wow, thanks Pei Yan for the ID!

  4. The 'plastic beads' were hard and we couldn't squish them. I do hope they are something natural. Sigh.



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