Pollooks
Pollooks are simple-bodied, free-swimming parasites that resemble blends of lancets, leeches, and monogenean flatworms. The newborn larvae (400 micrometers-1.1 millimeters, depending on species) are free-living slow burrowers with nigh-embryonic sluglike bodies, which live on top of, within, or just below the surface of fine silt, eating microbes or decayed organic matter.
They use hooks, adapted from small fins to lodge in the nostrils, gills, and occasionally mouths of large (>10 cm) Carpozoans with iron-based blood, and feed using sticky feeding bulbs. All feed on blood to some extent, although some also consume mucus, epithelial cells, and host microbes, to varying extents.
Ancestry & Overview
The entire lineage developed from adjusting Glowlips' development backwards: rather than the young being small, transparent versions of the adults, the young are tinier, plumper, more embryo-like, and throwbacks to recent filter-feeding ancestors, while the adults hold onto bloodsucking habits, rather than developing into scavengers with fully-developed lips and Glow Detriti-holding adaptations. Like Glowlips larvae, the young hatch without fins, though they acquire them within a few days. The basal gill-specialists are the slowest to acquire fins.
Pollooks are split into three varieties: the basal variety, gill specialists, and then nostril specialists, and then mouth specialists. The earliest varieties fed only on Luceremundarians, but then expanded to the more fish-like Asterzoans. Classification is tricky, because occasionally species in one group can be found in the 'wrong' orifice, and a few oddball species revert to more basal feeding methods for the lineage. Further complicating matters, they will rarely hybridize to produce viable hybrids.
The gill specialists are, overall, the mildest, with the weakest acids and simplest hooks. Most nostril specialists absorb some nutrients from mucus, as well as blood. The mouth specialists are the smallest and slipperiest. They lodge themselves in crannies of the host’s mouth, even behind teeth, with their fierce hooks. Adults are thickly coated in a distasteful mucus that discourages hosts from removing them with their tongues.
Occurrence & Habitat
Pollooks exist in the greatest numbers and diversity in LadyM’s abyssal zone. As Pollooks tend to cluster around corpses, scavengers, especially Luceremundarian hosts, tend to host the greatest numbers and diversity of Pollooks.
Being soft-bodied, poor burrowers, Pollook larvae occur in the greatest densities in fine silt relatively rich in organic matter, and especially around rotting corpses. Especially rocky sea beds are almost devoid of Pollook larvae. Pollooks (and especially their larvae) have a knack for surviving in places with crushing pressure, cold temperatures, and low food and oxygen, so higher than normal Pollook larvae densities are a sign one has reached the abyssal zone.
The genus is well-adapted to the deep and its crushing pressures, darkness, cold, low food levels and low oxygen. If brought up to the lower reaches of the twilight zone, they will neither hunt nor breed. Furthermore, when out of their element, they are often eaten by the comparatively more abundant and active predators of the twilight zones. However, as they are attached inside the orifices of their hosts, should midnight zone-dwelling hosts migrate to the twilight zone, they will inevitably be brought along. In this way, the population has spread to Vailnoff Ocean.
If their hosts happen to only skim the lower reaches of the twilight zone for a few hours, their parasites almost always survive. However, if brought too far up, they will be suffer decompression damage, and, if it continues, they shall bloat, rupture, and die. Indeed, cleverer migratory hosts tend to go up to the twilight zone just to get rid of especially bad infestations.
Behavior
Larvae
The larvae are slow burrowers, and so move very little. They passively consume any microbes or organic matter that comes by.
Adults
Having little endurance and poor senses, adult and subadult Pollooks generally “ambush” potential hosts that get close to a Pollook-infested area. It swims in a trout-like manner into the orifices of hosts. As it gorges on blood, it becomes bloated, like a mosquito, into a rounder shape.
Senses & Bioluminescence
Larvae
Pollook larvae are blind, although they have a keen sense of smell. They cannot glow, and passively consume nutrients. They develop sight early on as they turn into subadults, and lights shortly after.
Adults
Pollooks’ nasal patches are very sensitive to smell; much of their “brains” are dedicated to processing smells. More derived species can even bulge the patch out slightly to increase surface area and ability to receive smells. This feature is more common in Vailnoff Ocean species, as (at time of development) the number and diversity of hosts is much more limited than in LadyM Ocean, strengthening the pressure to find hosts.
Its photoreceptors have developed folded areas that increase visual acuity, allowing it to detect flashes of bioluminesence. Still, its perception of detail is still very crude. Its eyes can still distinguish red, green, blue, and light blue.
Once it figures out the general location of a host and gets close enough, it uses a “flashlight” of red light to home in on it. As red wavelengths from the sun’s rays travels only a very short distance in water, and Glow Detritis don’t glow red, it is often useless for deep-water species to be sensitive to the color. Indeed, it penetrates so little that even Midnight Zone organisms which migrate to the Twilight Zone have little reason to pick up on it. Pollooks’ flashlights are therefore undetectable to most potential hosts.
Although they still carry Glow Detritis, like their ancestor, their lifestyles are so different from their ancestor's that the Glowlips never accumulate to such levels as to cause a detectable glow.
Physiology
Larvae
Where their habitats are some blend of very cold, very low in food, or low-oxygen, Pollook larvae are potentially slow-growing. High levels of fresh chemicals from Carpozoan hosts, whether dead or alive, accelerates their maturation, which is accelerated still further by Glow Detriti chemicals. Sometimes, when a corpse lands onto a patch of Pollook larvae, the Pollook larvae can mature into subadults just in time for a big potential host to show up and start scavenging.
Adults
Despite its somewhat sucker-like mouth, it attaches purely through hooks. These fin-derived hooks are generally not ossified, and only a few mouth Pollook species have minor, umbrella-strut-like spiny reinforcements in their hooks. Only small triangles remain of their fatty fins.
Pollooks have no proper mouth: they simply extrude their nasal patches into bulbs when feeding to maximize surface area. The acid it secretes is mild, by digestive standards: between 3-6.3 in pH. It's assisted by proteases, including a parallel to bromelain.
Adult Pollooks breed with the nearest other Pollook within their host. Gill specialists, whatever their exact ancestry, tend to use broadcast spawning. Mouth specialists often have extra-sticky mucus patches, where which fertilized eggs stick. When the eggs are close to hatching, the Pollook briefly dislodges itself, slips its tail out from the host's mouth, and sheds its mucus. This is almost always done while the host is sleeping or dormant, as the Pollook is otherwise easy to kill with a bite. Nostril specialists use a blend of either mode.
Ecology
Pollook larvae, being nigh-microscopic, digestible, and defenseless until they turn into subadults, are easily eaten by anything sifting through the top two centimeters of silt. Although they live in the most abundance around rotting corpses, they can occur even when there are no visible traces of organic matter left. In essence, Pollook larvae “upgrade” gradually-accumulated nutrients from microbes or detritus into somewhat more concentrated parcels, making them a useful food source for larger organisms.