Grenadier

Image by neptunecanada via Flickr

Grenadiers were first established during the 17th Century where particularly big, particularly strong soldiers were chosen to throw olden day grenades, which I guess were really heavy back then. Having gotten used to standing right at the front of the front line, lighting grenades and then waiting to throw them at just the right time such that the baddies on the other side couldn't just throw it right back, grenadiers became elite troops and leaders in battle even after the whole grenade thing became less important.

It's also a fish.
What's the connection?
I have absolutely NO idea.

Grenadiers, also known as Rattails, constitute an entire family of fish with some 400 species living at depths between 200 and 6,000 metres (660-20,000 ft) and attaining lengths between 10 cm and 1.5 metres. Most of them are bottom living fish and boy are they good at it! Not only can they be found across the marine world from pole to pole, but they also dominate this particular niche in the deep sea; it is thought that some 15% of all deep sea fish are Grenadiers. It seems that catfish haven't quite gotten to grips with the deep life the way Grenadiers have.

Image via Wikipedia

One of the first things you notice when you see a Grenadier are the gigantic eyes in a gigantic head. This could mean that they are easy about how deep underwater they want to be. Many Grenadiers can be found at a whole range of depths, from the pitch black of the Abyss to right around the Sunlight Zone where eyes are actually useful. In darkness, their lateral line becomes more important for sensing movement and vibrations in the water around them. They also have chemoreceptors on their head and lips and sensory barbels on their chin, sort of like catfish. On their underside is a photophore that can be shone in different directions. This might be used as a spotlight on the floor beneath, but it's situated near their anus which seems a bit back to front to me. In any case, with these sensors a Grenadier can hover around the sea bed in search of food, which is thought to be pretty much any bit of sea food they can find, including carrion. Some will even sift through the mud with their snout to find worms and such. Helpfully situated on the underside of the head is the less obviously gigantic mouth, which nevertheless rapaciously hungers for the taste of flesh.

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I haven't even mentioned the Rattail's ratty tail! From that big head the Grenadier tapers away to nothing. They don't have a tail fin at all, instead their anal fin runs all the way along to the end. It looks like quite an odd set-up but seems to suit them quite well and they aren't at all bad at swimming, even if they may also conserve energy by judicious use of idleness.

Image via Wikipedia

Some Grenadiers are solitary, others form schools. They retain a swim bladder, unlike many deep sea fish, but they also have strange muscles attached to them, unlike most fish in general. This may allow them to produce sounds from the swim bladder, perhaps for communication or courtship. Not much is known about what happens when a male and female get together. They do lay loads and loads of eggs, more than 100,000 of them, and they float upwards before hatching. The baby Grenadiers then start life, moving to deeper waters as they get older.

"One day, my son, all this pitch darkness and mud will be yours..."