Third Rock from the Sea

For the first time in a week, it wasn't raining after I finished work - huzzah! I headed down to the shore in order to have a quick peek beneath a few rocks embedded in the gritty sand. First up, though, was this beast

A beached Blue Jellyfish Cyanea lamarckii

Not sure I've seen a jellyfish in February before, though Storm Erik certainly hit us hard here in Uig. For instance, it blew the side door clean off the hotel, tearing chunks out of the doorframe where the hinges had been attached (naturally, even though all of this happened quite close to my window, I slept right through it). Come daylight, we had a right giggle fitting an emergency replacement door in the strong winds, a three man job in fact, immediately followed by almost as much fun painting it up before the next band of rain hit (gotta love it when the wind blows the black paint off your brush and all across the adjacent white walls...)

Anyways...

By now, you all know (you DO all know, right?) that I'm undertaking my Challenge 2019 and, amongst other things, this year I'm focussing on beetles. I've already had a brief, unsuccessful search for one particular species so far this year. Would I have more success today? Here's the habitat

The larger rocks are partly submerged at high tide - note they're festooned with Channelled Wrack

Seems a daft kind of place to look for a terrestrial beetle, but would you believe there's an entire air-breathing ecosystem surviving beneath each of these rocks? Well, there is - incredibly

Halorates reprobus - male (L) and female (R) on the underside of an upturned rock

Strigamia maritima - an exclusively littoral species found beneath rocks on the beach

And, thankfully, the star of today's show - 

Aepus marinus - a 2.5mm killing machine! 

At high tide these creatures survive in naturally occurring air pockets beneath the rocks. I've found that large rocks with a generally flattened underside situated on coarse gritty sands are far and away the best places to check for Aepus marinus. If the beach gravel is too fine they don't occur. Likewise, you won't find them if the substrate is too stony or comprised of cobbles. The rock has to be bedded into just the right particle size of grit, presumably suitable air pockets won't form if the conditions aren't correct. If the whole thing gets swamped, they will be inundated with seawater and drown. I do suffer a degree of guilt every time I upheave a boulder, I know it won't fit back into place quite perfectly, have I doomed everything beneath to a salty death? Surely some must succumb anyway whenever a storm hits and dislodges boulders. It takes the phrase 'living on the edge' to extremes! 

Aepus marinus, along with the very similar Aepopsis robinii, are believed to hunt tiny springtails. Their eyes are reduced and they are flightless, neither being necessary to a lifestyle of chasing prey through the cracks and crevices of grit and across buried rock faces. For a long time I suspected that mites may form a large part of the diet of these tiny beetles, for there are always many more mites present on the underside of the rocks than springtails. But, thinking about it, I now suspect that the outer cuticle of a mite would prove too tough for such a tiny beetle. Food for thought. 

Just in case anybody out there is wondering how I fared during my first week of walking my way back to fitness, I totalled 32 miles. That's not including however far I potter around during the course of work hours, I'm on about proper sustained walks. 32 miles sounds a lot, but if you average it out, it's less than five miles per day. I'm going to start walking to the pier and back before work as well as after work. Plus a long walk at least once per week. Though I really do wish it would stop raining every time I head off into the distance!