Jenna had taken the job originally out of need but her feelings about it had transformed over time. Doctor Mboto had proved to be a very considerate and thoughtful employer who turned the possibly degrading and unpleasant job into a enjoyable experience.
She was a courier but a rather unusual courier as she transported living organisms inside of her body. Most were rather small and were ones that could live in an organ of a human host without harm to itself or the "host." Others, however, were quite large and required special care in their entry into a human host.
The Doc loved his profession. Both a Doctor of medical xenoparasitology and xenobiologist he loved the organisms he studied. Jenna would smile as he waxed fondly about some rather ugly alien parasite and he somehow had altered her view of them. She had come to see the beauty of the most bizarre and nasty creature.
He also greatly enjoyed working with courier hosts and not a few enjoyed his professionalism and passion in working with them. He didn't see the couriers as lessers but colleagues that assisted in the study of true parasites that attacked humans and organisms that found the body cavities of humans amenable for temporary residence during transport.
The old man had always believed that the natural entry of the organism into a courier was best, where possible. It was a standing joke that he probably enjoyed helping a creature enter someone more than sex. Jenna knew it wasn't a joke but also knew he never did it with anything but the utmost respect for her and the other couriers.
She sat smiling as the fond memory of some alien creature slowly worming into one of her openings ran through her mind. It was a job but the process, at times, could be very pleasant, even some of the more uncomfortable entries had their own pleasures.
The Doc came out, with his huge toothy grin and a particularly spunky attitude, indicating a particularly unusual organism that he needed her services for.
"Hello Jenna, how are you today?" he started as he grinned from ear to ear.
She had a wary smile at his obviously heightened state of excitement and responded, "Very well Doc, umm, I hear there is a job to be done."
"Ah yes, and one, I think, we will both enjoy. It is always a joy to have a courier who takes as much pleasure in the job as I do." he returned, as he lightly placed his hand on the shoulder of the petite young woman. He then turned her with gentle pressure indicating his obvious desire to get started.
Jenna, was only one hundred and sixty centimeters (5'2") tall with dark red hair and brown eyes. He skin was rather pale from her general lack of exposure to sun light due to her travels on long range interstellar transports. She bit her full, lower lip in anticipation of whatever was awaiting her as she turned with the pressure and they began walking down towards the lab.
Dr. Mboto was a fairly stout, and very black man from Zaire, Earth, not the planetary alliance. The fortunes of Africa had changed over the millennia and the University of Kinshasa where he had gotten his medical training was fairly prestigious. He had gone on to study at the Lonasek Xenobiological Research Institute and had been working with these unique organisms that could tolerate and even thrive inside an alien host, humans.
The Doc described the organism she would be transporting and her heart had begun to beat quite rapidly. Despite her experience she had not ever carried anything like it or anything quite so large that was able to enter a human on its own. It, at the same time, intrigued, aroused and scared the crap out of her.
They came into the lab and the Doctor pointed out the small tank the creature was in. The temperature gage indicated 38.2 degrees Celsius. All that could be seen of the organism was its breathing syphon sticking up thru the mud.
The reasons that humans were used for this, is that the conditions aboard interstellar transports were harsh. Humans were rather hardy organisms that keep their internal environment very stable and could be quite congenial to delicate organisms. This was particularly true of ones that potentially parasitized or could form symbiotic relationships with humans.
In this case the creature was a potential symbiote that could help a human deal with certain pathogens native to it's world. It needed further study and had to be moved to a research facility that worked with potential symbiotes. Before she agreed to carry it Jenna wished to see it, however.
"Umm Doc, can I have a look at it?" she said.
He smiled, nodded and said, "I understand but the ship is leaving tomorrow. I need to know immediately if you are willing to do this job. You need to get prepared and I'll get it cleaned and ready for entry. We need to have it inside of the host at least overnight to evaluate if its ok to proceed with the transport."
She nodded and went to the room where organisms were implanted. She first selected the vaginal insert she preferred on the special seat. First, it kept creatures out of the wrong opening. And second, with large organisms, masturbating on the insert would cause her anus to alternately relax and then constrict. Better this, than it simply spasming closed in response to entry and thus allowing the creature opportunity to more easily burrow into her rectum thru her anus.
Having attached the insert to the seat of the anal implantation mount she undressed and then sat down in a chair to wait for the Doc to come with the organism. She didn't have to wait long.
Dr. Mboto came in with the creature in a shallow bowl. Walking over to Jenna he sat next to her and showed her it.
It was about six inches (9.5 cm) long and 2 (3 cm) thick near it rounded back end. It had a pointed front end and was thus roughly tear shaped. The body was segmented with each one forming a slightly larger lump as they progressed to the tail end. Each annular ring forming each segment had a ridge of small nobs, about a dozen on each. Though its rear end was rounded, a slender tail extended from its center, it was the breathing tube she had seen in the tank.
She looked at it as it powerful body squirmed. At the same time she was very excited and somewhat terrified by the idea of it crawling into her and being inside of her. She stroked it and it immediately quested for the warm hand that had touched it as it grew increasingly uncomfortable in the cool air of the room.
She looked at the Doc and over the objections of her thumping heart and innate fear of something forcing it way into her anally she said, "Ok, let's do it."
He smiled widely and with his hand indicated she should get on the mount. She walked over and gripped the two handle bar grips and then settled down onto the insert.
The mount was very simple with its grips of the courier host to grab and the seat that cupped her mons and a slender insert that rode deep into her vagina. This left her anal bud exposed and ready for entry by the alien organism.
Jenna settled down and then rub her mons against the seat with its small ridge of soft knobs that sat directly in front of the vaginal insert and pressed against her clitoris stimulating it. As she contemplated the entry of the organism, her anus was already spasming open and close in anticipation.
She felt the Doc's finger frame her anus and stretch it to make her little anus gap slightly to help the creature find, and being it initial entry into, it. She then felt the lip of the bowl contact her between her anus and vaginal opening. As it was tipped up the creature slid against her anal region, and the liquid in it trickled down her labia and dripped off.
She had a screen that showed the view from a video camera directly above and behind her, trained on her anus. She groaned as she felt its body squirming against her rosebud. It had immediately began probing the flesh around her anus attracted to her heat. Then she gasped a little as she felt something wiggle directly into her slightly gaping anal opening.
Finding her anus and sensing the warmth and moisture immediately inside the animal aggressively began to force its way in. Her sphincter muscles briefly stayed relaxed until it began to stretch them and then firmly constricted, but it was already too late.
On finding the woman's orifice, the slender pointed head had wiggled quickly into the opening. The front inch of the creature had elongated and was already past her anus's natural defenses when they constricted to stop further penetration. Now it settled into slowly working its way into her rectum.
As she watched she became aroused and slowly pumped her pussy on the vaginal insert. Her anus slightly relaxed with each ride down the shaft and constricted when she lifted back up. The creature elongated like a worm as she constricted and contracted itself as she relaxed to pull a tiny bit more up her anus.
She tried hard prevent herself from automatically baring down to expel the invader but found that it seemingly smooth skin extended thousands of tiny barbs to prevent its being dislodged. It wasn't painful but the rough texture of these spines was intensely stimulating.
The Doc pulled the bowl away leaving the rest of it body to squirm against her anal region and genital lips. She watched in fascination as it squirmed but soon was lost in a haze of need as she continued to masturbate on the insert. She felt the body continue to slowly work its way into her.
The natural persistence of her anus at trying to keep this thing out was overmatched by it desire get into the warm, moist interior of her rectum. With each passing moment her muscles slowly stretched as the ever thickening body forced its way up her. The nobs on its ridged annular rings teased the tender flesh of her anus as one after another slowly passed into her body.
As she watched she realized that the last third of the creature's body, although, very active didn't elongate. It was beginning to approach her anus and she had never had anything that size enter her before. Yet the body had already stretched her quite a bit and need to only stretch a bit more to accommodate it.
Still her hole was wildly spasming as she watched despite her willing it to accept the creature's body. This turned her on even more as she moved to her first orgasm. As wild shuddering past thru her body her anus now relaxed and constricted intensely letting the creature get the first part of this back portion into her.
Her muscle contracted around the thick knobby body torturing her soft, sensitive flesh on it. The creature wiggled and squirmed undeterred by her anus's continued spasming. Now with the thickest part ringed by her anus the body began to pass with slightly greater speed into her rectum.
The video camera showed the fat body jerking around as it slowly slid in, it knobs teasing her. As it began to pass in her anus gaped and then slow began to close. Still the slender breathing tube extended from her distended opening that continued to twitch in response to the animal just inside of it.
Sometimes, the her anus would stretch as the tail end of the body surged slightly out as it elongated inside of her body. With a final orgasm she pulled off the vaginal insert and stood still feeling the creature squirming deep inside of her.
That night she slept uneasily as the creature continued to actively wiggle. Her anus had soon toned up and on the feeling of animal's fat knobby tail end sometimes pressing hard against her tight anal muscle awoke her.
She would lay in aroused discomfort as she felt the slender tube pulsating in her anus and wiggling between her buttocks as the body moved in the tight confines of her rectum. Compelled by the stimulation she would rub her clit and thrust a couple of fingers into her vagina and play with herself until she had a couple of hot, sweaty orgasms and she could sleep again.
In the morning she found herself tired and hungry. She could eat until she had delivered the organism to the distant lab, it would be a long week. On top of it she realized that her new rectal resident had no intension of calming down, she was going to be orgasming the whole trip.
On that thought she smiled and went to the Doc, for the final exam for the trip.