The creature from the pit

28th June 2012, Thursday

A couple of winters ago a small willow dominated pit had its cover of trees removed and the vegetation is still in transition.  A range of ruderal species grow on what was once shaded bare ground around the pit whilst the open water, lacking in aquatic flowering plants, is dominated by filamentous algae, with unicellular algae colouring the water.

pit.jpg

Over time of course the vegetation will settle down and become dominated by the species associated with unshaded wetlands, with seeds lying dormant in the seed bank in the silt at the bottom of the pond providing some of the likely successful species.

The aquatic fauna seems to be on the way to establishing itself too. Peering into the turbid water to see if I could spot one of the medicinal leeches I noticed a few weeks back, subtle movements drew attention to

a 2-3 cm long fish-like creature.  It was infact the larva of the great crested newt.

gcn-larva.jpg

Excuse the picture, it was as I said a rather turbid pond.  The three pairs of bushy gills are absolutely characteristic of newt larvae, and the behaviour was typical great crested newt.  Whilst the larvae of smooth and palmate newts tend to lurk, frequently hidden in aquatic weeds or at the bottom of the pond, great crested newt larvae are nektonic, swimming in the open water column where they feed on aquatic invertebrates such as daphnia.  This is, perhaps, the key reason why this species is so vulnerable to fish predation as they are very exposed to attack as a result of their open water lifestyle.

It often surprises people to know that ponds that dry out are often good for newts, but the drying out removes one of the most significant predators of the larvae, and as long as the pond lasts into August in some seasons some larvae will be able to metamorphose and get onto land before the water disappears..