At 555 words, here is my story.
Lieutenant Jess Sanderson leaned against the bulkhead wall clutching her weapon and raggedly gasping for breath. Far behind her, she heard the eerie drawn-out howl of the dogspider, its chitinous claws scrabbling for purchase on the smooth plascrete floor. Shuddering, she could see in her minds’ eye the drool surrounding its maw, gobbets of spittle breaking off to land smoking on the deck below its pincers.
Refusing to cower behind such paltry cover, she willed herself to get up, and sprint through the airlock. She sensed movement in the corner of her eye, but her course was set now, it was too late to turn back. Frantically spinning the handle, she made it out before it crashed shut again. For a moment she exulted, and drew a deep breath of unrecycled air - it always smelled better out in the colonies without the funk and stench of hydraulics and ship processes. Shaking her head to free herself from her dangerous tangential thinking, Lieutenant Sanderson applied herself to the task at hand - getting away. After all, that door wouldn’t hold back the dogspider forever.
Over there - the boundary fence of the settlement, and on the rise just behind it, some spongiform plant-like cover that was better than nothing. Lieutenant Jess Sanderson headed for it at full pelt, as the dogspider came bursting through the airlock with a resounding crash. Sniffing the air for her spoor, the dogspider’s muzzle swung slowly to bear on her position. A flurry of limbs and it returned its inexorable progress towards her. After diving behind the straggly plant, Jess realised it was futile to keep running... she would have to make a stand here and now. Standing up, she wound back her arm and threw her jitter-bang... a semi-autonomous weapons platform meant to distract and hopefully kill - but the latter was unlikely. Once released, it started to exude a range of sensoria - scents, flashes of light, temperature fluctuations, radiation, you name it - it did it. Once it identified the target, it sped away on an erratic course, until it was overhauled. Then the particle cannon would open up, but Lieutenant Sanderson didn’t hold much hope of its success against a fully grown dogspider.
Indeed, the beast closed upon it with a single minded devotion. Shrugging off the jitter-bang’s feeble assault, the dogspider swatted it with one fearsomely clawed appendage then wrenched it from the ground with its slavering jaws. It bit down a few times, causing a cacophony of rending metal, then once again turned to glare balefully at Lieutenant Sanderson. The dogspider cleared the low boundary fence in a single leap, contemptuously dropping the mangled remains of the jitter-bang at her feet. A low, menacing growl started, and Jess flung herself at the beast, dodging the rasping tongue with its acidic slime; the grasping claws trying to rake her flesh. She wrestled with the creature, hauling on the thick matted hair on its body, until a shout shattered her concentration: “Jessica Amanda Sanderson! Get out of that garden this instant! Back in the house, young lady, and finish your homework!”
“Aw mum, Spike and I are only playing! It’s not like we’ll hurt your stupid daisies!” sulking, Jessica stomped inside, leaving Spike wagging his tail and chewing on his red rubber ball in the sun.