r/worldbuilding • u/theMCATreturns • 13h ago
Lore Reproduction via "brooding pits."
An "imp" larva, pupa, adolescent, and adult.
A diagram of an imp polyp. And variously-sized colonies/brooding pits.
Soft-shelled imps.
Hard-shelled imps.
"Goblin brooding pits" are a fairly common staple of fantasy. I starting thinking about how such a pit would work. At least where the pit itself is a living part of the reproduction cycle. And not just like, a receptacle for broadcast spawning or eggs.
So, I came up with "imps," which are single species with dozens of different morphologically distinct "castes."
TLDR: they are insect-like humanoids. They have brooding pits made up of millions of barnacle-like polyps. Dead or dying imps are thrown into the pit and broken down. Their DNA "fertilizes" the polyps, and thousands of imp larva emerge a few days later. Depending on their biological sex, they develop into dramatically different creatures. Only four (out of thirteen) sexes are intelligent.
LIFE CYCLE:
- Polyps: the foundational "sex" of the imp species. They are monoploidal, having a single set of chromosomes. A single polyp more closely resembles a barnacle than a true coral polyp, which suggests that the species initially evolved from crustaceans. Each microscopic polyp is capable of reproducing asexually through binary division.
- They grow in clusters, eventually forming small pitcher-plant-like traps. The smallest of these pits can only fill with few millimeters of digestive fluid. And primarily prey on insects.
- As a pit grows larger, it changes the composition of the fluid to attract larger prey. After several decades of growth, it becomes voluminous enough to attract and digest a large animal. This includes prey animals. But also crucially, members of its own species.
- Brooding pit: once a polyp colony becomes sufficiently large, it enters a seasonal brooding period. The layer of polyps lining the inside of the feeding pit undergo a series of physiological changes. Essentially switching from "digestion mode" to "breeding mode."
- Critically, the pit's digestive fluid is drained and replaced with "brooding fluid." This fluid breaks down organic material as usual. But through a mysterious, anomalous process it preserves the integrity of "compatible DNA."
- The polyps composing the "brooding layer" present fertilizable germ-cells. Once fertilized, the polyps will begin gestating millions of imp embryos.
- The imp species does not reproduce sexually. Instead, "reproductive-aged" individuals are lured to a pit by the pheromone-rich brooding fluid. Once immersed in the fluid, the imp will quickly die and their body is broken down. The DNA in their corpse "fertilizes" the brooding layer of polyps.
- Fertilization:
- Depending on how "fertile" a season is, a pit can be filled with multiple different imps. The brooding period breaks down organic material, preserving strands of (relatively) complete genomes.
- A receptive polyp collects these strands of DNA. They need not come from a single donor. It could collect 25% of a complete chromosome from one strand. Another 33% from another, etc. It can link these disparate strands together into a novel combination.
- The polyp has an internal mechanism for "counting" how much DNA it has collected. Once it has (around) 100% of a complete donor genome, that genome is allowed to fertilize its oocyte. This process is not perfect, and the majority of the millions of fertilized oocytes do not develop into viable embryos.
- Some polyps are fertilized multiple times. This allows tri- and tetraploidal embryos to develop. Which are important parts of the imp caste system.
- Occasionally, DNA from prey animals gets mixed into the slurry. This almost always result in a nonviable embryo. But very occasionally foreign DNA is successfully integrated into an imp zygote. This horizontal transmission accounts for their chimeric appearance and rapid evolution. As well as a large number of vestigial traits.
- Hatching: the eggs hatch into microscopic larva. These larva are all roughly the same size. The nutrient rich slurry (from the fertilizing bodies) nourishes them until they grow large enough to leave the pit. Depending on the sex/caste, the larva range from tick to rat-sized when they finally crawl out.
- Sexes: Discounting polyps, there are 12 possible castes. Each caste is essentially a different animal entirely. Occupying non-competing ecological niches. That allows the species to colonize radically different environments. For example, a low-resource island may not be able to support a population of intelligent imps. But it could have a thriving population of small lice. There are four sex chromosomes: X, Y, Z, W.
- XY/XX: these are small, parasitic mites. They live as ectoparasites on a variety of animals. Though, they have a preference for their own species. That way, if a single imp fertilizes the brooding pit, their colony of mites increases the available genetic diversity.
- XW/XZ: Lice. Despite their name, they occupy a rodent-like niche. They are lobster-like creatures. Like all imps, once they reach a certain age they become attracted to the smell of the brooding pits and return for fertilization. Generally, the older you get the stronger this attraction is. As elderly individuals are more likely to have strong ecological fitness.
- XXY/XXX: these are triploidal organisms, with three sets of each chromosome. They are called "soft-shelled nymphs" because they resemble mammals, reptiles, or birds. A nymph does not undergo a transformative metamorphosis like their tetraploidal siblings. Instead, they simply grow larger over time. They take a variety of forms resembling ungulates, carnivorans, etc. depending on their population.
- XXW/XXZ: these are "hard-shelled nymphs." They resemble large arthropods, with leathery carapaces. Coconut crabs, large crickets, lobsters, etc.
- XXXY/XXXX: "soft-shelled imps." The tetraploidal castes are the only ones capable of speech and higher reasoning. As larva they resemble large leathery insects. Once they get to a certain size, the undergo metamorphosis and develop an internal skeleton. They emerge from this metamorphosis roughly the size of a human toddler. Soft-shells are the most human-like in appearance.
- XXXW/XXXZ: "hard-shelled imps." They resemble large (mostly bipedal) insect people. Despite their inhuman appearance, they are fully intelligent and capable of speech. Due to their size and durability, they typically occupy warrior-adjacent roles. But lack the stamina and speed of their gracile soft-shelled counterparts.
- Larva:
- Once an individual larva emerges from the brooding pit, they are on their own. They scavenge or hunt for food (depending on the individual). Mites, lice, and nymphs continue to grow through instar phases.
- These castes do not develop human-like intelligence and continue to live as animals in their natural habitat. Though, it is not unusual for adult imps to farm nymphs for food. This is not considered cannibalism.
- Metamorphosis:
- A tetraploidal imp will (once it gets to a certain size) undergo a metamorphosis. It comes out the other size bipedal and with a vague understanding of their genetic donor's language. This is critical, because "in the wild" there are rarely adults around to guide/teach the newly-sentient children.
- This transmission of memories is poorly understood even by imp scientists, but plays an important part of their culture. Because memories (or even personality traits) can pass on between generations, they have a much weaker fear of death. It is more-or-less similar to the human concept of reincarnation. But it occurs between multiple individuals and their hundreds of descendants. Not one-to-one. If a large pit was fertilized with dozens of adult imps, their descendants could expect to inherit some memories from each of them.
- If an imp's head is too damaged or removed, their memories will not pass on. This is sometimes done to "problem individuals" or criminals, in order to prevent their deviance from reoccurring in subsequent generations.
- Adolescence:
- Once an imp metamorphosizes, they emerge roughly the size of a human toddler. If a population center exists nearby, they will usually seek it out using their donor's memories.
- It's not unusual for an area to be completely devoid of adult imps. In which case adolescents congregate together and start civilization from scratch.
- There are multiple instances of natural disasters wiping out entire civilizations. Only for surviving polyp colonies to repopulate the area (with new imps) decades later.
- Modern society:
- "Wild imps" born in the wilderness generally live the same way they've been living for thousands of years. But in large population centers, each generation is cultivated as one would livestock.
- Recently dead or dying imps are thrown into massive brooding pits. Far larger than they would have been able to grow under their "natural" conditions. Unless an individual has a genetic defect, transmissible disease, or committed a disqualifying crime. An imp can reasonably expect to be thrown into a pit upon their death.
- Larva are allowed to live inside cultivated green spaces and collected by "keepers" once they metamorphosize. Individuality is not particularly cherished. "Mutants" and people who diverge from preconceived societal norms are treated harshly or outright culled.
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u/_TheOrangeNinja_ 10h ago edited 10h ago
OP i really hate to be the bearer of bad news but youve just independently arrived at trolls from homestuck, who are ALSO horned humanoid/insectoid alien people who reproduce in brooding pits via recombinant DNA from the entire collective species. youve even landed on a lot of the same cultural beats: they live in the brooding caverns until they pupate into a child form where they're selected by a caretaker (lusus) and taken to the surface to construct a home for themselves while they mature (adults have to leave the planet). its a super brutal society with a blood-based caste system, culling is the norm especially for mutants and culled grubs are often made into condiments for food
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u/Orangewolf99 9h ago
Eeeh, there are some major differences between OP's and Homestuck trolls.
For one, each troll has the same life cycle and they are sexually hermaphroditic. OP's do have sexual dimorphism even if it is vestigial and their genetic combinations creates diverse creatures.
Second, OP's breeding pit uses dead imps to fertilize. Homestuck trolls donate generic material without having to die (usually).
Third, trolls use a symbiotic relationship with an unrelated species (lusio) to raise their young. There's nothing stopping imps from adopting whatever crawls out of their breeding pits.
You can't just say "oh there's a breeding pit, so it must be homestuck".
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u/_TheOrangeNinja_ 9h ago
I gave a lot more reasons than that, and even then homestuck trolls also have what they believe to be vestigial sexual dimorphism
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u/Orangewolf99 9h ago
They don't have any sexual dimorphism, they just dress differently based on the culture of the lusus that raises them and what they are exposed to.
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u/_TheOrangeNinja_ 9h ago
No, there's repeated commentary in universe about how trolls display secondary sexual characteristics that fall on a bimodal distribution similar to humans despite not having any primary sexes
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u/Spaghettisnakes 1h ago
Very cool. I wonder about the soft-shelled imps losing their carapaces and gaining an internal skeleton during metamorphosis. Why would this have developed? Do soft-shelled nymphs, closely resembling non-arthropod species, have an internal or exoskeleton? The first explanation that comes to mind is that resembling humans might make it easier to manage relations between imp colonies and human settlements, but I'm curious what you had in mind.
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u/cthultystka 11h ago
Wow, such a cool concept! Two questions:
Since they reproduce via brooding pits, what's the point of having males and females?
How long do imps live on average? You said the older they get, the stronger the call of the brooding pits becomes, but if one were far away, or somehow able to resist their call, would they be able to live longer?