Devil's Trumpet

This guest entry was written and illustrated by Troll Man 

After the marine mass extinction event at the end of the ice age, many invertebrate groups, in particular the fish-like snarks, have begun to dominate the seas after the disappearance of most vertebrate competitors, and now, in the warm hothouse oceans, flourish in vast numbers and diversity. However, snarks are not the only gastropods to rebound during the Late Ultimocene. 

Just beneath the waves, a strange creature drifts in the sunlit waters, shimmering fins billowing in the current, algae and anemone-like hydras encrusting its body. A partly unwound, spiralling shell, somewhat resembling those of heteromorphic ammonites of another world in a long ago age, betrays an ancestry to molluscs, and indeed its history began as one of many mundane aquatic snails that were transplanted upon Serina hundreds of millions of years ago. This is one of the last of the reef snails, a group that were incredibly successful and widespread for many millions of years throughout the planet’s history, but were largely decimated during the Mid Ultimocene due to a variety of ecological and environmental factors, such as the shrinking habitat from dropping sea levels and intense predation by molluscivorous marine molodonts, and eventually, the near-complete collapse of the oceanic biosphere.

However, a small number of reef snail species were capable of surviving this catastrophe, a few primitive deepwater forms barely more advanced than feather-tongues, those which retained limited mobility, even as adults, and relied less on symbiotic algae for nutrients. Allowing them to follow the movements of marine snow and organic detritus and flee from growing dead sea zones, clinging on in the deepwater environments now long unsuitable for development of their photosynthetic reefs. And enough of these eked out a living like this for just long enough to pull through to the light at the end of the tunnel, a world fresh and new, where they could begin to start the seeds anew.

Reef snails of the past were primarily sessile and colonial organisms that anchored themselves to rocky seabeds, tiny molluscs that formed great congregations that could grow immense over long periods. This strange descendant of the group abandons many of the group’s characteristics; not only does it live singly and free-floating, it is utterly gigantic for a member of the group. Most reef snails were only a few centimeters in size at best, often even less than that, but this, the Devil’s Trumpet, grows to colossal proportions by comparison; a well-grown adult female of exceptional age (which, for this species, can reach well into their seventies or eighties) can have a shell more than ten feet long unwound, and her feeding tentacles (extensions of the gastropod foot) can span nearly four meters across. However, the sexual dimorphism is also extreme; males have a much shorter shell and are dwarfed by the females, rarely reaching more than forty centimetres in length, and almost never forms any winding shape.

The huge, broad “fins” of the devil’s trumpet continue to host symbiotic micro-algae, despite its deepwater ancestors no longer living on photosynthesis, because they provided their hosts an additional function beyond energy gathering. The algae produces poisonous phycotoxins (similar to those which produce red tides) which saturate the gastropod’s flesh, rendering its host equally unpalatable. This was advantageous enough for the ancestral snails to retain the algae within them even in environments where they would not produce energy, although by now they have resumed their original function. The devil’s trumpets float only a few meters below the water, allowing the algae to produce carbohydrates which supply the molluscs with additional energy, but the mainstay of their diet is plankton, which is also captured utilizing these broad fins. These produce fine, invisible strands of web-like mucus, which flows in the water column, adhering to any particles and drifting microorganisms that touch it. Periodically, the devil’s trumpet sweeps a pair of smaller, finer, comb-like arms through this mucus coating to extract anything edible caught within it. They often catch far in excess than it can actually eat, and this attracts commensals, such as remora-like escardines, that hoover up the leftovers. This helps to keep its net usable for longer, as eventually it becomes clogged with enough particles that it is discarded, left to sink into the darker depths as marine snow.

Males are much smaller and more capable of actively swimming, with a more hydrodynamic shell, propelling themselves with two pairs of fins. Although blind, its sensory tentacles are able to hone into the scent and minute water disturbances created by the movement of tiny aquatic organisms, allowing it to have a more proactive method of filter-feeding, sifting through denser clouds of plankton. This greater mobility is also important for actually finding a mate, because females have far less control over their movements, so males must actively search for them. Due to the unpredictability of males discovering them, females are able to store sperm from males to use over multiple breeding cycles, but subsequent matings from other males introduce spermicidal secretions to kill off this competing sperm before introducing a new spermatophore. 

Offspring are relatively large and born ovoviviparously, the newborns are around four to five centimetres in length, and as is usual for gastropods, free-living immediately. Although most reef snails had planktonic young, only those with larger, well-developed young which were hardier against the anoxic water conditions. This meant smaller clutch sizes, but the huge size of the female offsets this, allowing her to release hundreds of young at once. The larger and older the female, the more young it can produce in a clutch at once, increasing the likelihood of reproductive success, thereby selecting for more “fit” females that have managed to survive for longer in the process. Young are frequent prey for numerous pelagic predators, but the adults have few due to their thickened shells and poisonous, distasteful flesh; most adults only die when washed ashore or end up battered by sea storms, but they can avoid the full brunt of these by releasing air from chambers in their shells, allowing them to sink to deeper water at will.