Dale Fort Blog Number 27

21 02 2014

TARDIGRADESTardi

Unless you have a microscope you’re not likely to be very familiar with Tardigrades.  The likelihood is that you are sitting pretty close to very large numbers of them.  These remarkable animals dwell in their millions among the mosses and lichens that develop and grow in the cracks between paving stones, in gutters and on rocks and stones.

They were not discovered until 1773 when the German naturalist Goeze described them as kleiner wasseba.   This means “little water bear”.  They have 4-8 limbs, each of which ends in a little claw.

Cuudly bear with text

Tardigrade means “slow walking” and this is what they do.  Under a low-power microscope they resemble bumbling-gaited microscopic bears.

Tardigirl with text

Most of the 1000-odd species feed on plants, sucking the juice out them using a pair of piercing stylets that emerge from the mouth.  Some of them are predators using the same method to eat other animals like nematode worms (See Blog 1).  Some consume microscopic creatures whole and some are cannibals.

Most species have separate sexes.  The males fertilize the eggs through a gonopore or sometimes eggs are laid on the ground and fertilized there.  Some species have no known males and reproduce by parthenogenesis (virgin birth, no chaps involved).

The most astonishing thing about these creatures is their ability to survive extreme conditions.  They are found at the tops of the highest mountains, and at the bottom of the deepest seas. They are found deep underground, in hot springs and from the poles to the equator.

They survive extreme environments by virtue of their capacity to adopt a “resting” stage called a tun . In this state, they can survive temperatures near to absolute zero or as high as 150oC; levels of radiation  a thousand times stronger than any other known animal; lack of oxygen equivalent to the vacuum of space and a decade or so without any water.

tardi tun and active

It may not be possible to detect any signs of metabolism during this phase.  All they need is a drop of water and a few hours and they’ll be back to normal.  This might cause us to redefine what we mean by death because “no metabolic activity” isn’t a bad definition (although “nature’s way of telling you to slow down” is funnier in my opinion).  This ability is known as cryptobiosis (hidden life) and an understanding of it leads to wildly exciting possibilities for space travel and organ transplants.  It also might help to explain why we’ve found it so difficult to establish if there’s life on Mars.  What if something like a tardigrade existed for long periods as a resting stage and only showed signs of life every few 100 years or so?  You’d have to be lucky to catch it when it was detectable with one probe every 20 years.  We need to send a tardigrade specialist to Mars.  I know of only one (hello Clive) and I don’t think he wants to go.  Some people go so far as to suggest that the ancestors of our current species might have been early colonisers of the earth from elsewhere in the cosmos.  They’ve certainly been on earth for a very long time. fossil evidence dates back to at least the Cambrian Period (530 million years ago).

Behold with text

If they can survive the vacuum of space and if say a meteorite impact could blast them into space (and several hundred meteorites that have been found on Earth are known to be bits of Mars) then it could be that the loonies are in fact correct and aliens are indeed among us.  They might still be arriving.

Celebrate these remarkable animals by building one for yourself:

Build your own tardigrade

Designed by Jane Cutting, Placement Student at Dale Fort a long time ago.

Keep a look out for Blog 28 when Nunzilla may return…..

Advertisements




Dale Fort Blog Number 26

18 02 2014

This blog continues the history of Dale Fort from where we left it in Blog Number 16.

Nunzilla has left the building…..

The History of Dale Fort Part 7:

The Elizabethan Period

George Owen, the Elizabethan chronicler of Pembrokeshire refers to two blockhouses being located at the mouth of Milford Haven by 1546.  One of these, at Angle was described thus: A rounde turrett never yet finished (East Blockhouse).

East Blockhouse with label

The other structure in the parish of Dale was located at the site of the present day West Blockhouse and was described similarly as a round tower 20 feet in diameter with eight ports or loopes for great ordinance.   Substantial remains of this existed until the construction of the current West Blockhouse Fort in the 19th Century.

Picture1

Lewis’ Topographical Dictionary states that blockhouses were built here in the reign of Elizabeth.  Even though the artillery of the time could not cover the whole entrance to Milford Haven, the existence of two blockhouses opposite one another would have had the effect of diverting any attacking vessels into the path between them.  This would have enabled vessels defending the entrance to concentrate their fire.  The range of sixteenth century cannon would have reduced the safe entrance of Milford Haven to a gap of about half a mile.

In 1587 (the year before the Spanish Armada), Sir Thomas Perot and George Owen were put in command of 500 men and charged with repairing the town walls of Tenby.

Owens plaque in Nevern church copy

They also dug trenches to shelter musketeers at potential landing places around the Haven.  Owen also suggested a devious plan to outwit the enemy.  At that time there was a chapel on St.Ann’s Head.  Sailors used this building as a mark for finding the safe entrance to Milford haven.    Owen’s scheme was to confuse invading vessels by dismantling the chapel and rebuilding it out of position.  Approaching Spanish ships would use the relocated building as a mark and would crash into the rocks at the entrance.  The idea was not put into practice but the spirit of it has been used extensively elsewhere.  The Allies used mock-up tanks and landing craft at various places around the British coast to confuse the Germans before the Normandy landings.  Sandy Haven (near Dale) was equipped with decoy lights and burners to mimic Milford Docks and town.  Nightly, men would light the lights and fire up the burners to impersonate different types of bomb explosions and fires.  Watwick Point on the south side of Castle Beach Bay had a dummy battery.  This comprised two telegraph poles as guns, a two storey Battery Observation Post, and some tents.  A compliment of men marched about and shifted equipment around to make the whole thing look very realistic on an aerial reconnaissance photograph.

As a result of recommendations to the Queen’s Chief Councilor, William Cecil, in 1590 The Privy Council set aside funds for the supply of ordinance and ammunition to three new forts at Milford.  These were to be located at Dale Point, The Stack and Rat Island.  The Spanish Armada was defeated in 1588.  This actually had the effect of increasing unease about the prospect of a Spanish invasion of Britain.

Pedro Lopez addressing the Spanish Council of War in 1595 emphasized the vulnerability of Milford Haven.  He reckoned a Spanish force could take it and render it impregnable within two days.

In 1598, Owen drew up a list of places suitable for fortification around the Haven. New blockhouses had been begun at Dale and Angle but remained unfinished.  Throughout the 1590s there was intense fortification of the British coasts.  This was especially so on the south and west coasts were it was considered an attack was most likely.  One of the best-known British military engineers, Paul Ive wrote a treatise The Practice of Fortification and was busy building defensive structures on the Channel Islands and at Portsmouth.  Ive mentions Milford Haven specifically, where his thoughts on the adequacy of the defences were in conflict with local opinion.  George Owen, the Bishop of St.Davids, Alban Stepney and two Deputy Lieutenants Sir John Wogan and Francis Meyrick wrote collectively to the Lord Keeper, Sir John Pickering, Lord Burghley, the Earl of Essex, Lord Brockhurst and the Earl of Pembroke, stressing how weak and vulnerable Milford Haven was.  Referring to Ive’s report they said: What report he made of his opinion we know not, but sure we are that his abode about that service was very short and his survey was very speedily dispatched.

Read about tardigrades in the next blog…..