The Equatorial Sweepswimmer

Order: Magnoglossiformes

Family: Pilosaglossidae

Genus: Pilosaglossos

A rare sight in the carpgrass prairies, the equatorial sweepswimmer is a sight to behold. Reaching a length of 7 metres and reaching a weight of around 2,850 kg (2.8 tons), this gigantic filter feeder is one of the more elusive pelagys, with most of its relatives found in cold, chilly waters up south or in the north, and are mostly found in coastal waters with vast, featureless plains of nutrient-rich substrate and only occasionally visit carpgrass prairies. Distinguishable for its large lower jaws, spine-like fins which are quite rigid and stiff and mottled brown colourations. Despite appearances, the sweepswimmer is not an aggressive predator and rarely shows any signs of aggression unless threatened, and is in fact quite the gentle giant, being a filter feeder with quite an unusual strategy of consuming prey: benthic filter-feeding.

All pelagys ancestrally possess three tongues, which aid in pushing food into the throat. Most derived pelagys have either lost their tongues or repurposed them (like the boney, jointed tongues of the harpooner clade), and the sweepswimmer is part of a relatively early radiation of pelagys which adapted two of their tongues to aid in feeding. Early sweepswimmer relatives use their tongues to capture prey and thus had adapted cartilaginous 'teeth' to facilitate the capture of said prey. Some eventually developed sieve-like cartilaginous processes for filter feeding, giving rise to the modern sweepswimmer clade. Their tongues, often retracted into the lower jaw unless they're feeding are long, thin and muscular have rows of combtooth-like cartilaginous setae at the ends which are used like sieves; the sweepswimmer drags it through the seafloor, filtering out mud and silt while capturing little invertebrates and straining them from the sand, collecting them and putting its tongue into its pharyngeal jaws, which have dozens of rows of small, hook-like teeth, which capture the tiny benthic creatures, which are then sucked into the throat with considerable force, and left to digest in the stomach. This method of feeding is quite efficient, but generates considerable wear and tear onto the rakers, which causes them to shed them every month or so, halting feeding in the process and relying on nutrient stores in order to regenerate, but they only take around a week to regenerate fully, in which they can continue feeding and replace the lost nutrients and energy spent regenerating the rakers.

Their benthic filter feeding style relies on sediments rich with nutrients, which are often found close to islands, making them strongly reliant on shallow waters and coasts, and are rarely seen swimming in deep water unless migrating or looking for benthos in deeper waters of the continental shelves, which they can be found feeding, but they can feed planktonically in the water column on occasion, by using their feathery rakers to sweep through massive shoals of plankton, but otherwise, they mostly live far away from pelagic environments and This reclusive behaviour makes them hard to find in carpgrass prairies, which they are only found during the mating season, where they seek the shallow waters in order for to raise their young.

Sweepswimmers find mates by using clicking sounds and low-frequency hums in order to find mates, composing deep melodies which they make with potential partners, with the males trying to mimic and match the tone of the female. If the females deem the male to be suitable as a partner, they will eventually mate and reproduce, laying four eggs on the ground and putting them in its jaws, 'eating' its eggs. However, it puts the eggs in its mouth not to eat, but to protect them, in a method called 'mouthbrooding', which the pelagys swallows the eggs into its mouth, keeping them safe from harm, with the only tradeoff being that the pelagys cannot eat, as any kind of substantial jaw movement such as chewing or biting will damage the eggs, but still protecting the eggs from external threat. Around a week before hatching, the sweepswimmer regurgitates its eggs and puts them on the seafloor, protecting them until hatching, where the sweepswimmer leaves them alone to grow on their own. The young start out life as small carnivores, with expanded guts and a rather unspecialised stomach, using the tongues to capture benthic invertebrates from out of the sand by quickly extending and pulling back their tongues into their pharyngeal jaws, which can suck in soft prey items. The juveniles stay carnivores until they reach roughly one-and-a-half years old, in which they start growing rakers on their tongues and slowly start to transition from a carnivorous diet to a planktinovorous diet, in which they start rapidly growing until they reach sexual maturity at around the age of eight.