Serina: Bowel-Lord Gutsucker

Snarks have diverged into countless different forms, ranging from burrowing worms only a few millimetres long, terrestrial forms waddling upon four tetrapod-like legs, up to vast pelagic hunters larger than a school bus. But perhaps what is most extreme in their ranks are not what they have advanced to, but what they can lose and still function, in an environment unlike that of other lineages. In this manner, the most unusual snarks would undoubtably be considered those of the endoparasitic variety, those which have taken up residence inside larger animals. These come in a surprising number of forms, as this adaptation has occurred more than once amongst snarks.

As a general rule, how large a parasite gets depends on the size of its host. On Earth, the largest tapeworms occur in the guts of whales, while the the biggest ever fleas plagued the hides of non-avian dinosaurs. Here, the rule works in the same terms, as the mega-skuorcs which roam Serinarcta are host to some truly gargantuan pests, inside and out. Their skin pulses with leech-like spikerays over a foot long, and botfly-like skewer larvae that grow larger than a fist, swarms of biting insects that could be mistaken as a flock of small birds. And their massive digestive tract, built for consuming vast quantities of vegetation, also writhes with intestinal parasites of repulsive scale. One of the very largest are the gutsuckers, creatures which resemble colossal nematodes, but are in fact a type of highly-degenerate snail, a breed of snark which have nearly lost all characteristics that define members of the group.

Gutsuckers originated, a bit surprisingly, as marine animals, simple detritivorous animals which thrived in the rich shallow seas feeding on bacteria, phytoplankton, and minute organic particles. Their transition to parasites originally began by accidental ingestion by herbivorous or filter-feeding dolfinches, and was subsequently carried inland by surf scooters, where it could then spread to land animals which drank tainted freshwater. The transition of a parasite from a fully aquatic host to a terrestrial one is obviously much quicker and more simple than for a full aquatic animal to become terrestrial, especially when both the original and new hosts are primarily herbivorous vertebrates. Primary hosts during the early hothouse were trunkos and thorngrazers, but as gantuans and skulossi grew larger and more common, they proved to be more suitable homes due to their larger sizes and proportionately larger digestive systems. Unlike either trunkos or thorngrazers, skuorcs have neither teeth or the cranial kinesis that allows them to chew, so food is swallowed in large chunks and digestion is primarily chemical, done by slow bacterial fermentation in a voluminous multi-chambered stomach and intestine. In total, their digestive tracts can stretch for several hundred feet, offering plenty of room for a veritable jungle of microfauna. The resulting nutritional chyme becomes a nigh-unending pre-digested feast for parasitic organisms that reside in its colon, allowing them to grow far larger than in these earlier hosts.

The gutsucker has lost its own digestive system due to it being redundant for its lifestyle; its pharynx has greatly expanded into a large branching structure with which it passively absorbs passing nutrients into its bloodstream, and waste products are secreted through the skin. Its mandibles no longer serve any purpose in either food consumption or defence, and now curve backwards to act as holdfasts which cling to the gut wall. Because the amount of food which arrives each day is so immense and so little work is required by the gutsuckers to obtain it, they can grow enormous. The largest species, the bowel-lord gutsucker, can reach a monstrous eleven feet in length and up to fifteen pounds in weight for an adult female. Females are much larger than males, and also drastically differ in body shape. Males are much shorter and flatter, and retain small sensory tentacles. This is because females grow large to continuously produce large quantities of larva, while males merely need to find a female, curl themselves around her, and provide her with sperm, which are much less energy-intensive to produce. The female's right spiracle is much higher up than the left one to line up with the male's reproductive spiracle. Even the male's feeding tentacles are tiny compared to the female, because he actually gets most of his nutrients by parasitizing her, latching onto her back and siphoning up a portion of her blood.

Because they grow so large, only a relative number of them can take host inside a single skuorc at one time before it begins threatening the survival of their host. As a result, gutsuckers are territorial, and males will vigorously defend their females against other females which anchor themselves too close or rival males that attempt to usurp his place, tearing at them with hooked spines over his body (the females, once attached, do little other than feed and produce offspring). Once mature and with a male attached, females reproduce continuously until death; like all snarks, the gutsuckers give live birth, producing litters of tiny, maggot-like larvae about the size of a rice grain. These make their way to the cloaca, where they are deposited in dung and, depending on the species, either wait until they are washed into a nearby water source or cling to vegetation, waiting to be ingested. Some species have a secondary host in the form of the dungaroos, which naturally feed on gantuan faeces, and need to be ingested by this other skuorc species as well to complete their life-cycle. Young are born with simple eyespots and pigmented skin, as they will attempt to climb to light to increase the chance of being ingested by grazing animals, but these are both lost as they metamorphose into their adult form in the gut.