ANSWERS TO CORRESPONDENTS: How do deep-sea fish survive extreme pressure?

QUESTION: How do deep-sea fish survive extreme pressure?

Deep-sea fish survive extreme pressure through various biochemical, physiological and anatomical adaptations that allow them to thrive in environments where ­pressures can exceed 1,000 times that at sea level.

These fish typically lack gas-filled swim bladders, which are common in surface-dwelling fish for buoyancy control.

Instead, species such as the snailfish (e.g. Pseudoliparis swirei, found in the Mariana Trench) have a jelly-like body composition that is less compressible, allowing them to maintain buoyancy without gas bladders.

They often have high levels of a substance called trimethylamine N-oxide (TMAO). TMAO helps stabilise proteins, essential for energy production and muscle movement, under extreme pressure.

Studies on hadal snailfish suggest they have a lot of TMAO, as they live in very deep waters, and this helps them cope with increasing pressures.

Deep-sea fish like the anglerfish (Melanocetus johnsonii) exhibit skeletal and muscular adaptations.

Their bones are often soft and flexible, reducing the likelihood of fractures under pressure.

Finally, many deep-sea fish have unique cell membrane structures with specialised lipids.

These membranes maintain fluidity at high pressures, allowing normal cellular function.

Mr K. Andrew, Bangor, Gwynedd

QUESTION: What are some of the pros and cons of traditional rectangular bales of hay versus the much larger round ones?

Little rectangular square bales, the oldest type, are more convenient for small quantities and to moveby hand but are slower to make and transport.

Big bales come in both round and large rectangular packages; both have to be handled by machines because of their weight.

Round bales take up more storage space and do not fully utilise lorries and trailers, due to their shape.

Large square bales are more dense and stack easily, so they make the best use of transport and storage facilities.

Bales of damp grass can be wrapped in plastic to exclude air, thus preserving the grass as haylage for animal feed, especially when there is not enough sun to dry the grass for hay.

Richard Hudson, Hanley Swan, Worcs

A few decades ago, farm machinery changed and big balers became available. They can be used to make haylage — a cross between silage and hay that is suitable fodder for horses.

Some farmers still have the old machinery to make small bales, which are easy for one person to handle, usually weighing 40-56lb.

The main differences from a horse owner's point of view are cost and handling. A small bale will cost between £6 and £8.

To feed a large horse you will need about five a week (total cost £30-£40 a week), whereas a large bale costs £30-£45 and will feed a large horse for about three weeks (total cost £10-£15 a week).

But if you only have one horse, unless the haylage is very dry it will have gone 'off' after ten days and shouldn't be used. Ideally, three or more horses will eat a big bale before it has gone off.

The other consideration is the handling of large bales. It takes a lot of strength to move a large bale and get it in a place where it can be opened and used.

A tractor with a grabber on the front makes light work of it, but most horse owners don't have access to one.

Small-bale hay is the traditional wintertime feed for horses, but there are downsides both ways.

Hay may vary in quality and can be dusty, which makes horses cough; but a lot of haylage is too rich for horses if it includes cut ryegrass.

Unless the horses are working hard, they can put on too much weight if fed the suggested weight for their size.

Another downside to large bales of haylage is that, if the wrapping is punctured, the contents quickly become unusable, so careful handling is required.

A. Smith, Blackburn, Lancs

QUESTION: Did Robin Askwith tour a theatre version of Confessions Of A Window Cleaner?

Further to the earlier answer, I was at a performance of this at a theatre in Salisbury, Rhodesia, in the late 1970s.

The curtain went back and revealed a prop resembling the front of a house. In the top right-hand window stood a rather attractive young woman, naked from the waist up.

The shocked, conservative audience was silent. You could have heard a pin drop.

Rob Atkins, Tamworth, Staffordshire