Creatures that Live in Logs in Mangrove Swamps

There is a small fish that lives inside worm holes in mangrove trees.  I first saw this fish 25 years ago on a university field trip and I remember the fish being called a cobra fish but googling that term finds nothing and I cannot find its name.  Finding names for mangrove log creatures seems to be harder than normal as not much is published.  The first step is to get a good photo of the creature, not easy when you have to open up muddy logs to find them and then try to get clean enough to use a camera.  What I discovered is that the fish are certainly not alone.  The biodiversity in rotting mangrove logs is as high as the biodiversity of a rock pool.

The mangrove forest where most of the photos were taken - Redden Island

Shipworm holes can be large enough to put your finger in and many are calcified

A small shipworm showing the shells that bore into the wood

The key species in the rotting log ecosystem is the ship worm. These worms, which are actually bivalve molluscs grind away wood using their shells.  Logs soon end up riddled with hole that provide habitat for a wide range of creatures.  Logs also have other habitats. Common mangrove crabs make tunnels under logs, not that they need logs, just that they prefer to tunnel under logs than burrow out in the open.  Another range of creatures live in the space that opens up under the bark when the bark becomes lose.  As logs can be different sizes, in different states of decay and in a different position relative to tide heights, each logs is different and no log supports all species.  In all at least 20 species of macro-invertebrate depend on mangrove logs in north Queensland. 

The photos that follow show some of the creatures that I found under or within logs.  Every tenth log has something interesting.

These dartfish were under the bark of a tree that was completely exposed and had been so for possibly hours or days.  I assume the fish were in this position before I lifted the bark

The fish which are about 20 mm long can also be found inside the trees in shipworm holes.  This fish came out of a hole when I chipped into a shipworm infested log.

Non-descript crabs are the most common inhabitant

Giant flatworms up to 60 mm long glide through cracks

A giant flatworm coming out of a shipworm hole.  See the eye spots.

My new species for yesterday - looks like a species of stone crab

This snapping shrimp was as long as my hand and was found under a log

A colony of shrimps was present in the tunneled log shown above

I have very little idea what these 80 mm long creatures are