Jetguppies

This guest entry was written and illustrated by Troll Man. 

In the hundreds of millions of years since life was first transplanted upon this world, its seas have seen much change. Great undersea forests of algae, floating mats of jellyfish, reefs of sessile gastropods, and groves of marine bamboo; countless landscapes of life coming and going. In over two-hundred million years, many animal lineages have taken the plunge into the ocean, a fact which has never been true more than now, as the continental shelf becomes all but uninhabitable, encouraging all walks of life to make a claim at the richness of the cool shallow seas. But long before any of this, ray-finned fish continue to dominate the marine ecosystems ever since the first livebearers adapted to stand the salinity of the seas over two-hundred and sixty million years ago. While the days of truly gargantuan fishes and near-complete monopolistic hold over niches of this environment are long gone, new innovations continue to be honed and developed. And among the most radical changes of fish in this twilight epoch are those which have evolved a new method of locomotion.

A highly aberrant group of predaceous ray-finned fish which has spread rapidly throughout the Mid Ultimocene, with species known from seas pole-to-pole, from a few centimetres in length to some of the largest fish in the water. Members of this group are highly distinguishable by their reduced fins and highly modified gills, both inherited from an ancestral species originating in the Pangeacene, the turbo eel. Gradually, as many of descendants abandoned the slow, benthic existence of the turbo eel, these were further refined in its descendants over millions of years; the dorsal fin has been lost in all living species, as have the pelvis fins in some more advanced species, as the body has becoming increasingly specialized for high-speed jet propulsion. However, in most modern species, a jointed, fin-like protrusion has evolved from the flanges of the upper jaw as many species retained to a fast-moving pelagic lifestyle that demanded greater stability while moving.

The enlargement of the gill chambers have allowed jetguppies not only a modified form of swimming independent of fins, they have the secondary benefit of allowing more enriched oxygenation with a far greater surface area; in some species, the inner surface of the “gill-lung” is heavily vascularized for increased oxygen diffusion. This is a very useful adaptation for the jetguppies because utilization of high-speed jetting is more energy-consuming (particularly for larger species), and so increased oxygen intake helps fuel this energy use. Additionally, this form of locomotion is less effective in flowing habitats, largely restricting them from freshwater environments, not that this has hampered the group’s overall success in the seas. From humble origins they proliferated as fast-swimming pelagic carnivores, and now count among hundreds of species; while fish may no longer rule the seas of this world uncontested as they once did hundreds of millions of years ago, the jetguppies are certainly a very formidable caste of the marine food-web during the twilight era of the cooling world. 

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Estuarine Fly-Dancer (Byrrosaltator platyodon): While most of the remaining fins in jetguppies have mostly lost use as locomotory organs, they retain uses in other ways, such as through steering and stabilization, and in the fly-dancers, as elaborate display structures. The fly-dancers are a genus which have evolved long, flowing back fins of spectacular colours and patterns purely for courtship display, for they are thin and delicate, and females lack them. Males must maintain the health and fullness of their fins to impress potential mates, which recognize them as an honest judge of physical health; tattered or discoloured fins are detrimental to males hoping to pass on their genes, since they’re judged as signs of sickness, sub ordinance to other males, or poor living conditions (tearing of the fins is not a lethal handicap, however, for they will regrow, under healthy conditions, over time).

The ritual is not merely a male’s physical figure, for females expect the males to put on a show for them to best demonstrate their fitness and strength. What this might be varies from species to species; in some species this may be a race where males must keep up with a speeding female to test their endurance, or it could involve males leaping high out of the water to judge how high out of the water they can get. The estuarine fly-fisher creates and maintains large bowers dug out of the sand and decorated with shells and stones which the males use as their “stages” for their performances. The appearance of their bowers is just as important to the females as the appearance of the male himself. Fortunately, the collection of shells is none too difficult, for the diet of the estuarine fly-dancer is comprised mostly of hard-shelled molluscs, predominantly mid-sized bivalves and snails. Therefore, the female’s inspection of a male’s shell collection has more than superficial value; it’s a good gauge of how well he’s been feeding and his success as a hunter. Defending these shells from other males is also a constant challenge, since there are no better trinkets than those already picked out and treasured by another.

The bowers of male fly-dancers are easily visible from above as shell-filled, sandy pockmarks in the great fields of flowing sea bamboo in the coastal shallows, helping females easily locate them. Keeping the growth of this rapidly growing and spreading vegetation from invading its display arena is just another part of bower maintenance. These are evenly spaced apart, usually at least a few metres from the space of another male, as males are extraordinarily territorial and can rip each others’ fins to tatters in aggressive disputes. The fin-like jaw flanges have a razor’s edge which males use to cut at each other with like the spurs of a rooster (females also possess these, but for defence against predators). Males are twice the size of the females, reaching roughly twenty centimetres in length, and more heavily built for combat between one another. The size difference also allows the two sexes to niche partition, with males able to crack open much larger snails and bivalves than females can. Females tend to roam far and wide while foraging, while males inevitably must stay within a set home range; females will settle within the territory for several weeks between mating and birth, and then leaving immediately after that, leaving care of the young to the male. The presence of young in a male’s territory makes them more appealing to other females, ironically during the period where he is most disinterested in finding a mate, and now must fend off females who will try and kill his young and bring him back into season.

King Torpacuda (Halimperator horrifer): The largest species of jetguppy, and an archetype of the subgrouping, the fast-swimming torpacudas, the dominant predatory fish of the Mid Ultimocene. An adult king torpacuda can reach almost four metres in body length and up to five-hundred kilograms in weight, relying predominantly on marine birds and molodonts, such as sealumps and dolfinches, as prey to sustain its mass and active hunting style. Among the predators beneath the sea, it is only outmatched in individual strength by the daydreamers, which, in the days before they had evolved into sophonts, they once rivalled in the food chain. Around three to four million years ago, the species could reach more than twice as large, and were considered by early societies of ocean-going gravediggers as the demon of the deep. Tales spread far and wide of the monster fish with teeth longer than one’s arm capable of sinking boats and swallowing sailors as fast as the eye could blink. Over millennia, larger and more aggressive torpacudas were culled, and nowadays such attacks are nigh unheard of, as torpacudas concentrate their range far away from the settled greens and now harbour an instinctive aversion to such regions.

The torpacudas are primarily ambush predators that quickly run down any prey; capable of reaching a maximum speed of nearly forty kilometres an hour, there is no animal beneath the sea capable of outpacing them at full charge, as they reach close to the absolute limit of underwater speed, if not at the limit itself. However, due to its mass, it tires easily, operating mostly in short bursts of only a few seconds. Huge, spike-like teeth up to seven inches long make short work of anything captured by its jaws, which are savaged beyond recognition by powerful shakes of its head. The high-speed impact of the massive fish may sometimes be enough to shear prey in two, and almost instantly kills anything it directly strikes by the force alone causing massive internal injuries; use of its teeth for killing is almost always unnecessary. It is a highly effective marine predator, with more than half of hunts ending in a successful kill, but this is out of necessity. Its speed and acceleration are unmatched among any other large marine animals (excluding other torpacudas), but jet propulsion is energy intensive and for an animal that once reached over a ton to attain such speeds requires a very high metabolism. To maintain this requires them to eat a lot, and the torpacuda can’t afford to fail more than a few times before it becomes increasingly difficult to keep up its energy.

Fortunately, the seas of this world have never been more bountiful, and its preference for fat-rich red meat is easily sated by all manner of tribbetheres and birds which have returned to the sea over millions of years. As most of its prey swims much more slowly than the torpacuda, it hardly ever reaches top speeds, and can easily pick outpace young molodonts, porplets, and sealumps, which occur year-round due to the equatorial position of the receding oceans. In a single feeding, a king torpacuda may consume two-fifths of its body weight in meat if it can, with an extendable jaw allowing it to swallow large prey items whole. In the rare circumstances where the torpacuda is unable to successfully capture prey in enough hunts, it may attempt to beg another recently fed torpacuda to regurgitate a portion of its meal as a form of reciprocal altruism to help tide them over. Although generally solitary predators, the species has a mutual understanding of the price of failure, with the unspoken investment that in their own time of need that they return the offering.

Poison Smogfish (Foliopinna limalingua): The smogfish are a subgrouping of jetguppies which have not forgotten the original purpose of their enlarged gills, but have expanded upon this. A series of glands within the gill sacs just behind the operculum can release a cloud of foul-tasting ink that is ejected as the fish swims, immediately blinding any predator in pursuit. The exact composition of this ink varies from species to species; some eject a black cloud that quickly mixes with the water, obscuring the vision of anything pursuing, nocturnal species may use a bioluminescent spray to distract predators, some release a viscous slime that expands in the water and quickly adheres to whatever it lands on. The poison smogfish is a species which has the most aggressive form of ink; it consumes several species of sea jellies and incorporates their cnidocytes into its ink sacs, ejecting a cloud of paralytic neurotoxin which hold concentrated quantities of the venomous cells of the jellies. A direct hit is enough to kill an animal several times larger than the smogfish, and so it has few predators, aside from the few smart and fast enough to incapacitate the smogfish before it can fire its venomous ink. To avoid unnecessarily wasting this defence, it will inflate fleshy lobes along its gill chambers and flush them bright orange as a warning display.

Although it feeds on jellyfish to obtain its toxins, these are poor in actual nutrient and are not a regular part of its diet, which mostly consists of smaller fish. The poison smogfish is normally a well-camouflaged ambush predator, hiding amongst the strands of billowing kelp-like macro-algae. Its long, ragged fins, with fleshy extensions of its skin, and its irregularly banded green and white hide makes it nearly impossible to pick out from its leafy surroundings. Only its long, lure-like tongue is easily distinguishable, its tip modified to resemble a small snark; like an anglerfish, it allows its prey to come to it, as they literally swim into its open mouth following the allure of seemingly easy food. The species is largely sedentary, normally only migrating from their hunting positions when males seek out females to mate with and adolescent fish seeking to claim their own territories. Opposite to the very well camouflaged adults, juvenile smogfish are very brightly coloured and highly visible, making it easier for the parent to keep track of them and employing Batesian mimicry.

Eclipse Sunseeker (Monstrupraedator myrmecophaga): While nearly all members of the jetguppy group are known for their speed and agility, the sunseekers literally take this to new heights, becoming another in a long line of ray-finned fish which have developed gliding abilities. Rather unusually, because the pectoral fins have been lost (and subsequently replaced by jointed jaw flanges), it is the posterior fins which have developed into lift-propelled structures, and they spring from the water horizontally. In optimal conditions, given a good swim-up and in excellent wind conditions, they may reach distances of over one-hundred metres without touching the water, with enough maneuverability to curve and swoop in this duration; a considerable distance for a relatively large fish, which reach between sixty and seventy centimetres in length.

This species has a particular dietary specialization marking it as unique amongst the jetguppies, and in fact, amongst marine animals in general; the eclipse sunseeker is an aquatic myrmecophage, and adapted to hunt one of the most feared creatures of the oceans: the sea shoggoths. This is no simple task, for momentary contact with the horde ensures death through ten-thousand biting, stinging insects invading every orifice, and requiring far different tools than ripping claws and a lashing tongue common in terrestrial ant-eaters. The sunseeker, as a prerequisite, has some resistance to the venom of the shoggoths and the nerve-endings in its face are deadened to resist the inevitable occasional stings, but it cannot survive a direct defensive attack, so the eclipse sunseeker has evolved by absolute necessity to be very fast and efficient. Small shoals of the jetguppies attack in a coordinated fashion, spreading out across the superorganism, and with rapid bursts of speed engulf chunks of tendrils and protruding fringes of the writhing mass, darting back out a safe distance with mouthfuls of ants before the colony can react to this attack. Attacking in number from all sides helps to disorient the colonial intelligence of the gestalt mass, slowing down a cohesive defensive reaction and drastically reducing the effectiveness of any possible reaction. A well-coordinated and successful hunt can consume many thousands of ants, but as sunseekers usually only consume members of sterile worker castes from colonies millions strong, these rarely make a big impact on the colony’s overall health, should the colony not be suffering from some prior affliction beforehand.

A set of thick, mortar-like pharyngeal teeth immediately begins grinding ants to a paste in the mouth before they have a chance to sting, neutralizing the prey and making it safe for consumption. Such a trait likely first evolved to crush hard-shelled marine invertebrates such as crustaceans, bivalves, or marine snails (which eclipse sunseekers consume on occasion), but secondarily adapted to another wildly differing food source that became available. Being one of the few true predators of the shoggoths, the eclipse sunseeker is, in a sense, able to obtain the impregnability of its prey, taking on the toxins of its meal into its own flesh, rendering it unpalatable to most other animals. The art of shoggoth hunting is not a purely instinct one, and must be honed from adolescence.

Eclipse sunseekers breed monogamously, producing around two to four young which are carried in the gill chambers by parents for the first two to three weeks of life, nourished by a fat-rich secretion on the inner lining. Young sunseekers follow and observe adults as they hunt shoggoths, at first simply snapping up the ants which get scattered into the water by the attacks of the adults, but gradually growing bold enough to attempt strikes of their own. Adults have few predators, but young sunseekers often meet a grisly fate honing their skill at shoggoth-hunting; killed by their intended quarry. However, those number which mature into an experienced ant-eater effectively become apex predators with a continuously reliable food supply, for virtually no other animal would dare regularly attack what they hunt.

Snaggletooth Sunseeker (Laminaceps limadamator): One of the dominant groups of marine invertebrate since the very first days of Serina have been the gastropods, evolved from humble snails, these have invaded the seas in multiple events in their countless billions. More than a few marine predators have become snail-eating specialists, such as the molodont durophagodonts with jaws and teeth built to crush the shells of benthic snails, and the jetguppies are no exception. However, the snaggletooth hunts not normal sea snails or slugs but the fish-like snarks, which are far removed from any standard gastropod body form or behaviour. In particular, the species preys upon the bottom-dwelling spikerays, snarks which defend themselves through a venomous spine which can reach around to spike potential predators from any direction.

The snaggletooth has evolved highly distinctive protrusions from the top and bottom jaw, which are essential hunting organs for their toxic, benthic prey. They are laterally flattened and the front of both are covered in taste-sensitive nodules which they use to detect their camouflaged prey hiding on or just under the sand. The snaggletooth swims on its side like a flatfish, with one eye to the seabed and one eyeing the surface; preferences on which side sees up and which down seems to vary between individuals. The snaggletooth hunts in pairs, one swimming horizontally and one vertically to catch anything that tries to quickly swim away. Once the snaggletooth has confirmed its prey, it acts within a span of a few milliseconds, using these protrusions to pin the body of its prey to the ground, preventing it from escaping or firing its venomous spines. With the prey safely immobilized, the second sunseeker can move forward and slice through their soft bodies with the thin, blade-like teeth, well-adapted for cutting finely through boneless mollusc flesh.

Normally monogamous, they congregate in some numbers in time with the breeding cycle of certain shimmershiner species, as the movement of tens of thousands of snarks together to spawn and reproduce proves an irresistible feast for the jetguppies. Shimmershiners are larger than most snark species which they prey on and, living in tightly-knit shoals, are much more well-defended; hunting in groups is the only way in which the sunseekers can reliably hunt this type of prey. The snaggletooths focus on the newly born young, which swim awkwardly in the first few days of life, and being birthed in such numbers, the adults are bound to leave a few out of their sight for enough time to catch some. This species is responsible for a significant portion of infant mortalities in all shimmershiner species, since few other predators follow the shimmershiners to the more desolate, barren waters where they spawn. During this period, the snaggletooths themselves breed, as the abundance of prey in one place attracts many of the jetguppies together in one place and enough nutrition to spare for reproduction.

Hooktooth Butcherjaw (Gladiomentum maculatus): This is one species of a subgroup of the torpacudas which has returned to the bottom-feeding ancestor of the jetguppies. The butcherjaws are descriptively termed, for their lower jaw has extended into a greatly elongated point studded with outward-pointing teeth which can flick in and out at will like a switchblade. The use of this jagged knife-like jaw varies somewhat between species, but the hooktooth butcherjaw follows the most standard purpose; it rakes the hooked teeth through the sediment to snag up soft-bodied bottom-dwelling organisms, like fish and gastropods. The first line of investigation is by sight, honing into any particular movement or hint of an abnormal texture on the seabed. Sensitive pores on the skin of the jaw are able to determine if there is prey in the sand below in a fraction of a second, and just as quickly the butcherjaw pins the animal down with a flick of its head, where they are stuck through by the curved, serrated teeth on the edge of its chin.

Despite the fearsome appearance of this feeding instrument, this is not much use as a defensive weapon, with the butcherjaws preferring to flee rather than fight. True to their torpacuda heritage, they are extraordinarily fast when they need to be, able to outpace any other animal under the sea, with the exception of other torpacudas. Adults are mostly solitary, but juvenile butcherjaws live in shoals; the distinctive saw-like chin of the butcherjaws is small initially, and grows continuously with age (although growth plateaus around fifteen years old), adding another tooth every few months. Adults range around five to six feet in length (not including the extendable jaw) and live as bottom-feeders, but juveniles up to four feet in length and are more active pelagic hunters. Similar to most other torpacudas, the butcherjaw is independent from birth and has little in the way of parental care. Young school together in shallower depths, while adults forage in deeper waters, limiting the chances the two age groups will compete or that the adults will prey on the juveniles. The species ages slowly, generally not reaching sexual maturity until around a decade of life; they have prominent striped colouration that breaks up into the speckled patterns of the adults over time.

Ballistic Strikefish (Veloichthyovenator reductus): The great kelp forests of the Ultimocene seas are one of nature’s greatest marvels, underwater jungles stretching for untold miles upon miles across the shallow depths, turning the seas green. On the seafloor below, sheltered beneath the thick fronds are a rich ecosystem of creatures hiding underneath the sand. But the trophic levels are not quite as separated as it may seem, as many a swimming fish may briefly discover when they are suddenly grasped and pulled into a dugout lair for consumption from below. For the seafloor is pockmarked by fishers eyeing their quarries above.

An elongated tunnelling predator, the strikefish is part of a subgroup of extremely fast and slenderly built jetguppies, built for incredibly rapid and streamlined pursuit of prey. Some include barracuda-like pelagic species, cookie-cutter shark-like flesh grazers which quickly carve chunks from much larger marine animals, and eel-like species winding through narrow crags and tunnels in search of burrowing prey. The ballistic strikefish is something of an angler, hiding vertically in a narrow burrow within the sand with large binocular eyes to observe potential prey swimming above. Its banded green body is a well-established camouflaging colouration that hides it admits the algae-covered rocks and phytoplankton-stained waters. However, unlike many benthic predators, the ballistic strikefish lives up to its name and is a much more proactive ambush hunter.

When suitable prey swims within twenty or thirty feet above the strikefish’s burrow, the predator will literally rocket out like a bullet from a gun at blinding speed, snatching the animal with pin-like teeth and then, just as quickly, retreating back into its lair via a unique adaptation not known in any other jetguppy species; the ballistic strikefish has evolved a secondary anterior valve on its “gill-lung” which allows it to jet backwards just as quickly as it does forward. It starting sucking in water from the posterior valve and forcing them through the anterior valve, reversing the flow of water to jet tail-first. The spines of its fins are even able to pivot to the opposite end to reduce drag swimming backwards. Quick as a flash, the strikefish shoots in and out to snatch its prey, exposing itself to minimal risk from larger predators. Although not strictly social, many strikefish often create burrows in close conjunction with one another and it is not uncommon for a passing shoal of fish to suddenly be bombarded from below by dozens of strikefish simultaneously. The ability to swim backwards also allows them to navigate their narrow burrows without always needing to pivot and turn their bodies.

Bobble-Eyed Smogfish (Opthalmocaulis volatosor): In this great age of the sea, aquatic life on a scale not matched in hundreds of millions of years swells beneath the waves. So many shoals of baitfish tens of thousands of strong provide an endless feast for so many piscivorous carnivores; it is no wonder so many avian lineages have taken to life on the water, for there is plenty to be found here where there is only freezing wastes on land. However, there is no true free meal here, for an unusual fish specializes in hunting the fish-eaters. Often shadowing the movements of the largely helpless baitfish are a much larger variety of predatory jetguppies, easily recognizable by their bulging eyes, set on pivotable turrets. These are usually not a danger to the smaller fish, but are in fact their protectors, even if not for purely altruistic reasons. This is a species of jetguppy which has evolved to specialize primarily on capturing flying prey.

When the flocks of flying fish-eaters descend upon the shimmering shoals, the smogfish are ready. Facing their tail end just above the ocean’s surface, they use their modified gill organs to fire a powerful and precise spray of seawater, knocking the prey right out of the air and into the water, where they are quickly snatched up by the waiting jetguppy. This is a very sophisticated hunting weapon despite the unwieldiness of its appearance, since the smogfish has to fire backwards. Its strange bulging eyes are an adaptation for this, as they can swivel to look behind it without needing to curve its body. Its gills stretch all the way to the end of its body (the smogfish itself reaching five to six feet long), creating a very elongated chamber that maximizes power and accuracy; their shots can shoot the water up to fifty feet (although it begins to lose accuracy around thirty feet). They rarely need to shoot so far, as they wait for their prey to enter a dive and get as close as possible before firing.

The force of the blast alone is usually enough to knock the unfortunate tribbats or seabirds into the sea, but to help ensure the prey cannot escape once downed, the water is mixed with a sticky and oily secretion produced in the posterior end of the gill chambers (derived from the defensive ink used by other smogfish) which mats up the feathers or fur of their prey, preventing them from taking off again. This also assists with aim, as it means that even if the prey isn’t hit strongly enough to knock them down, the spray of the shot sticks to their bodies and may down them anyway. Since there is a limited stock of this secretion, it’s generally saved only for larger prey that has a greater chance of weathering the shot or recovering more quickly; it may occasionally also try and use it to down a number of prey individuals in one shot. The smogfish tend to hunt in pairs or small groups and trail common types of shoaling prey species fish to maximize encounters with their own favoured prey. To strike a relatively small, fast-moving animal out of the air from behind takes considerable skill and is honed from years of practice. Parental care is extensive and young are fed on regurgitated meats as they learn from experience to accurately and consistently capture their own prey. Juveniles will practice their skills on the surface-flitting saltflies, dragonfly-like marine insects that swarm low over the water’s surface.

Adults will usually share in a kill, with each fish taking turns ripping a carcass to chunks by pulling it apart as a group with pin-like teeth, encouraging group cooperation. Hunting itself is usually accomplished in turns; one group acting as the shooters and another as the retrievers to snatch up the victim as soon as it hits the water. Marine sparrowgulls, tribbfishers, and piscivorous seraphs represent the majority of targeted species, but larger packs of smogfish occasionally go after much larger fare. Shadowskimmers represent the largest possible prey species for the jetguppies; full-grown skimmers are nearly impossible to tackle in all but a perfectly synchronized group effort, requiring spray at multiple points on both wings at once to down the mightiest bird of the skies, but such a feast is certainly a prize worth trying for.

Southern Torpacuda (Carptorodon acanthocephalus): As the Ultimocene ice age rages onward, the ice sheets have advanced to almost entirely blanket the continent of Serinaustra, stretching out beyond the coast, where they shear and collapse into the ocean as they crust is buffeted by the currents. Along the edge of the continental shelf of the southern continent, a ichthyic predator is the bane of the marine molodonts and pretenguins which nest on the coastal icebergs and glaciers. The southern torpacuda is a hunter well-adapted to the frigid waters, a bruiser with spike-like teeth built for cutting through the blubbery, fat-rich hides of its polar prey. Competing only with the packs of smaller predaceous dolfinches, the torpacuda is otherwise an apex predator of the south polar waters, reaching over eight feet in length and up to nine-hundred pounds.

Due to the frigid waters in which they inhabit, southern torpacudas age slowly and spend much of their life in a period of low metabolic activity to conserve energy. This allows them to go many weeks in between meals, allowing them to eat much less than competing dolfinches. In preparation for a hunt, the torpacuda shivers its body and begins pumping blood vigorously into its body muscles to quickly raise its body temperature, which can rise more than fifteen degrees warmer within ninety minutes. The window of success before it cools off is relatively short, but torpacudas are supreme hunters; nothing in the ocean is faster than them underwater. During the few hour period of activity between long lulls of metabolic rest, they can become frenzied in their behaviour as nearly every animal in the sea becomes potential prey. Adults prefer the larger, blubber-rich molodonts, which can sate them for longer periods in a single meal, but with such a short hunting period they are not picky and will prey on anything that moves, from small flying seabirds resting on the water’s surface up to the enormous rakewhales, several times more massive than them.

Even pretenguins and molodonts which escape onto ice floes are not necessarily safe from the water-bound predator. Bony knobs on its reinforced head allow the torpacuda to ram and push, or even break apart small icebergs to force prey into the water or isolate them far from shore. Small groups of torpacudas may work together to push or tilt larger floes, or take turns circling around the floes to prevent any prey from escaping. Hunting of rakewhales and larger baleen birds also occurs in incidentally occurring groups, with individuals taking turns ramming or carving out mouthfuls of blubbery flesh until the animal dies of blood loss. In a single feeding session, the torpacuda can consume nearly a third of its body weight, allowing it to go another three months before needing to hunt again.

As the ocean recedes and glaciers push more outward, the range of the southern torpacuda has been driven ever more equatorial (making its name somewhat artifactual), putting it in increasing competition with other torpacuda species. In warmer waters, they are able to remain active and hunting more often due to not having to warm up its metabolism and with a greater abundance of prey, and now it consumes far in excess which it requires to survive, resulting in a recent population explosion that has placed greater turmoil in temperate waters, including increased competition with native torpacuda species. This effect is one which is occurring globally, as life is forced into ever smaller areas, intensifying competition to unsustainable levels. The southern torpacuda may now benefit from this climate change, but its success will not be long term.

Celestial Sunseeker (Legiodevorator geminoforma): Jetguppies, by large, are intelligent and usually social animals, both of which often lend to their success as marine predators. The celestial sunseeker is one species which has taken its behavioural complexity to greater heights. The sunseekers live in shoals, ranging from a few dozen to over two-hundred strong, with members of the group separated into two differing castes of breeding and non-breeding. The breeding caste is slimmer, with narrower gill chambers, while the non-breeding caste is wider and fatter, with broad gill chambers; the determination of castes occurs neither by age nor by sex, and adults of either male or female can be of the non-breeding caste, otherwise known as “brooders”. Sunseekers are one group of jetguppies which brood their young in their enlarged gill chambers, and in this species, this task is allocated to a small number of specialized shoal members to alleviate stress of parental care on every breeding adults.

The brooder caste exist as either siblings or the firstborn of the breeding pairs (although the presence of sufficient brooders in the shoal suppresses the creation of more), and although they don’t breed, by existing to assist in raising of their close family’s offspring or siblings, and so even if they don’t pass on their own genes, they help pass on the genes very close to their own. This strategy of kin selection in reproduction is the backbone of eusocial organisms, and the celestial sunseekers have a primitive form of eusociality, although the differentiation of caste members is simplistic. Perhaps in millions of years further, a caste system revolving around a single reproducing female with soldiers and workers may develop from the system which exists today, should the species continue thriving. Non-brooding adults benefit from being able to forage freely and breed continuously without long periods of necessary care of their offspring (widespread among jetguppies), while brooding adults don’t need to worry about hunting for themselves, since they’re fed by the other adults.

The enlarged gill chambers of the brooders compromises their ability to push water through it quickly, but provides much greater volume to hold groups of young, up to eight in each branchial chamber, the entrances of which are marked with a red stripe, making them easy to navigate for young fish. When bloated with young, their presence prompts the secretion of a nutritious slime which the fish within subsist on for the first several weeks of life after birth. Being fed by other adults allows the brooders to gain as much fat as possible without using it, keeping their collective young well-fed on the nutrient secretions, which the brooders’ body fat is converted into. The ratio of brooders to foragers in a shoal generally average between one in seven to one in ten, usually depending on the richness of food in the region. 

Shoals may range from a few dozen to hundreds strong, moving nomadically like an underwater column of army ants, if army ants were also marine piranhas. They hunt in a coordinated fashion, splitting up into smaller groups to cover greater area, sharing any prey they capture, and working together to tear apart larger animals. Although relatively small in size, reaching around fifteen to twenty centimetres in length, they can take down prey several times larger than themselves, working as a group to bite chunks out with blade-like interlocking teeth. They are indiscriminate foragers, feeding on small crustaceans, other fish, eargills, marine gastropods, and anything else they can catch. Carrion is a particular favourite, and the entire shoal will rapidly gorge themselves on any waterlogged carcass or offal, and if allowed to, may consume so much at once they get too heavy to get airborne.

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Due to their jet propulsion-based method of locomotion, the jetguppies are inherently at a disadvantage compared to other fish and snarks in flowing freshwater environments, limiting them to the ocean. However, there is one unique species which has managed to escape the sea, and not in the way that one might expect, as it has in fact escaped the ocean onto land. This is a process which is not uncommon, as many species of ray-finned fish have developed into amphibious species on Earth, with the ability to breathe air and locomote out of the water, such as mudskippers, the walking catfish, climbing perch, and the snakeheads. This process has also occurred on Serina several times, most evidently with the tribbets and eelsnakes, two clades which have progressed further and become fully terrestrial, bearing little resemblance to their original ichthyoid ancestors after many millions of years. By comparison, the jetguppies have barely dipped their toes out of the water, but the method of which they have done so is truly peculiar thanks to their derived anatomy.

With no pectoral fins with which to pull themselves along, they instead use massively elongated extensions of their jawbones, which already functioned as stabilizers replacing the pectoral fins in pelagic jetguppy species, to haul themselves across land very crudely. These are far more robustly built and hooked at the ends to accommodate this method of movement. The pelvic fins are broad and flattened to act as stabilizers, while the body shape is roughly triangular in cross-section and widening at the base, rather than the laterally flattened most common in jetguppies. Gradual movements are accomplished via this jaw pushing, somewhat seal-like, while faster leaps are by pushes of its long and muscular tail, as with most amphibious fish. These are particularly large amphibious fish (not counting the far more terrestrially adapted eelsnakes and tribbets, which obviously get far bigger), reaching between seventy and one-hundred centimetres in length and up to twenty-five pounds as adults, it does not venture very far from the shore during its terranautic journeys, for it does not have the ability to flee for any reasonable distance from land-based predators, although its size and aggression keep some potential threats at bay.

The false eelsnake, named for its loose resemblance to the completely unrelated Serinan fish group (but is in fact a sister taxon to the torpacudas), gets some of the oxygen by absorption through the tissue lining in its mouth, but its primary method of staying on land for long periods is very unconventional. Jetguppies, as wholly marine fish, did not develop any sort of lung-like organ for processing oxygenated air. Instead, the large fleshy gill sacs, used underwater for the jet propulsion which gives the group its name, has been modified to now store seawater, like reverse scuba tanks, allowing it to gradually receive oxygenated water over the course of several hours, greatly prolonging the time limit before it needs to return to the sea (as they never journey far from the coast, their skin can be kept damp rather easily by the continuous sea mist or by rolling on the damp ground, although they can also retreat into burrows in the sand or rock crevices on sunnier days). Being large allows them to store and carry around a good amount of water, and with the sphincter-like openings sealed shut, the larger adults can carry up to five cups of water at once.

Underwater, they are reasonably effective swimmers, although primarily benthic, consuming bottom-dwelling animals like crustaceans, molluscs, eargills, and smaller fish. The teeth in the primary jaws are slightly hooked and spike-like for snatching and pining prey, while the teeth in the pharyngeal jaws are bulbous and blunt for crushing the hard shells of its primary prey. On land too, its prey consists mostly of crustaceans, which it hunts mostly by ambush, but it is large enough to kill and consume seabirds and tribbfishers that wander too close, although this is less common due to these being faster and usually able to fly. A clumsy chase may ensue as it pursues slow-moving crabs, isopods, and even smaller false eelsnakes by pouncing repeatedly off its tail. In areas where they coexist, false eelsnakes may attempt to prey on pretenguin chicks on the outskirts of breeding colonies, or scavenge the carcasses of dead chicks. Few coastal animals can reliably predate an adult false eelsnake, so they are mainly threatened underwater or, where populations occur on the mainland, by inland hunters venturing down to the shoreline opportunistically. Swimming, they can eject a powerful stream of water from its gills to rapidly propel itself like other jetguppies, but on land it can do the same thing, except now the water is ejected into the face of the attacker to startle and disorient it for a few seconds, giving it a small window to escape into the sea. If it is too far from water to flee, the jetguppy gapes its mouth and expands its jaw extensions, exposing bright blue and purple skin and membranes in an aggressive threat display, leaping and swaying about to exaggerate the appearance of ferocity. Although primarily a bluff, it can still give a nasty bite or painful swing of its tail as a final resort. The bulk of the species' population occurs primarily on offshore islets lacking in larger terrestrial carnivores, where they can technically function as apex predators.

False eelsnakes are territorial animals, staking out plots of coastline and defending them against rivals with its colourful threat displays. By comparing the size and vibrancy of its jaw membranes, they can come away from such encounters non-violently, but evenly matched individuals may begin biting and stabbing at one another with the hook-like protruding teeth at the tip of its lower jaw. These are mostly used to help the jetguppies to pull itself up inclines and outcroppings on land, and pulling snails and bivalves off of rocks, but serve a secondary function like spurs for fights between members of its species. The species is cannibalistic, with larger animals eating smaller individuals if the size difference is large enough, but the fact juveniles are primarily aquatic, while the adults spend most of their time on land or in tide pools. Young are much more normal-looking fish (by jetguppy standards), with much shorter jaw extensions and proportionately larger fins, making them more effective swimmers, but far less capable of terrestrial locomotion, limiting them only to hopping on their tail at first. Independent from birth, they spend the first few months of their lives living under rocks and crags in deeper water further from shore as sculpin or goby-like fish, rarely, if ever venturing on land for the first year.