Chambered Siluro

The chambered siluro diverged from clawface siluros that continued their upward trajectory to the ocean surface. Their biggest change was developing a new means of buoyancy. The upper armor extensions now grow as full-fledged armor plates, which enclose two air-filled chambers that rest on their back. The chambered siluro can adjust these to move up and down in the water column, but they typically drift near the surface. The chambers supplement their gills too, with a high concentration of blood vessels on the back near the chambers where they can extract oxygen from the air within. They have a small opening at the front of the chambers to let air in, and a small exit at the back. This lets them pump air in and out to adjust buoyancy and to provide more oxygen when needed. The two chambers are separated by an internal septum but allow air to pass between them through a sphincter. The gills remain the same as before and are separate from the air chambers.

Indeed, the chambered siluro has adopted a much slower lifestyle. Their new chambers break their streamlining, making it cost more energy to swim frequently, though they are able to sink rapidly. Fortunately, they have little need for speed, and their size and armor protect them from much predation. They specialize in eating the relatively unsophisticated carpolantaians, which are easy enough to catch. This had been the favored food of young clawface siluros, so they merely retained this diet into adulthood. Being numerous but low in nutrition, they must eat them in great numbers.

Their body is somewhat shortened, and the tail is broader. Otherwise, the chambered siluro is similar in form and function to the clawface siluro. They have armor plates, which extend to form a pair of front fins and a single fin further back. Four tentacles extend around the mouth with shearing spikes for catching the prey and ripping it into digestible shreds. They have a pair of lens eyes. They are slightly less intelligent than their ancestor, as they no longer have the same need for problem-solving.

The male fertilizes the female's eggs by transferring sperm along his hind fin into an opening at the base of her hind fin; the partners use their front fins to clasp each other to mate. Afterward, she lays hundreds of eggs, which hatch into larvae of about six or seven millimeters in length, which live as benthic detritivores. Only a few larvae survive to adulthood, when they learn to swim and rise to the ocean surface.