Monday 28th June 2010

I am writing this just having complete the process  of the catch of the last dive of the cruise. That was a very busy day. We had two dives, almost one immediately after the other, exploring the cliffs, slopes and flat areas and collecting specimens.  As usual we collected the most common animals that will help us to identify them on the video transects.  One of our achievements is that we collected a fully intact specimen of an enteropneust (acorn worm), the first whole specimen that has been ever collected and preserved, thanks to Dave Edge!

Many benthic and benthopelagic animals leave trails of their activity on the seafloor  which often described by the german word «lebensspurren». Studying these trails is resembles a job a pathfinder. These trails can say many interesting things about life in the deep sea: what animals are living here, what are they doing and how they are feeding. For burrowing animals lebenspurren are the only evidence of their presence in the studied area.

Some lebensspurren are well known and recognizable. Echinoids leave long narrow trails by their long spines and feeding on organic matter in the sediment:

Echinoid trail

 Holothurians leave their faeces:

Holothurian faeces

Some fish also leave trails while staying on the seabed:

Fish trail

Echiurid or spoon worms are burrowing worms that put out of burrow their long proboscis looking for food. Their proboscis can stretch to one metre in length leaving amazing star –shaped trails on the seabed.

Echiuran burrow and feeding traces

The spiral trail of an acorn worm.

Spiral trace of an acorn worm

But sometime we observed something mysterious.

Mysterioud mound

These trails are very similar to «fairy rings» – enigmatic trails on the Porcupine Abyssal Plain in the North-East Atlantic. It represents a hill sometime almost a 1 m in diameter surrounding by large holes. After tens years of their observation it is still unknown what animal could make it.

On the South-East site we also find some enigmatic trails.

Mysterious trail

These trails could reach a few metres in length and resemble giant stitches.

There are many intriguing things at the deep sea that are waiting for being discovered and explained.

Tonya Rogacheva

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2 Responses to Monday 28th June 2010

  1. Will Hunter says:

    The mysterious fairy-ring trace is formed by an enteropneust. See Mauviel et al. 1987 Deep Sea Res. Part I. 34 (3). 329-335

    • All the enteropneusts collected on the cruise so far have shown no evidence of burrowing and appear to be surface feeders leaving a distinctive trace, often spiral. We did not collect any burrowing species of enteropneust although that does not mean to say they are not present at the Mid Atlantic Ridge.

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