Dakuth (pl. Dakutha, /dākʉθa/)

The ralkine bell is a gelatinous dome that connects to the crown of the magut shell and fully encases the dakuth body. The bell is formed from a colony of ralk; microscopic, vaguely starfish-shaped animals that interlock with each other into a lattice-like structure. They have the possibly unique trait of being fractal: each individual ralk is composed of a lattice of smaller ralk, that is made out of a lattice of tinier ralk. This likely contributes to its combined toughness and flexibility, but it's not yet fully known how. Possibly they are able to adjust the bell's density by loosening and tightening their connections with each other.  

Cilia Combs

In the planula and medusa growth stage, a part of the ralk(e) colony will incite the inner fractal colonies to extrude out as long chains, until reminiscent of a strand of hair and it's follicle. The rest of the colony will shift similar individuals close together and the extruded chains connect upon contact. The end result of are comb-like strips running vertically across the bell at even intervals. The continual activity of the ralk colony causes a wave-like motion in these combs and propels the dakuth forward.   Ralk(e) appear unable to absorb nutrients in this arrangement and will eventually die and ossify. This means they have to be continuously replaced for as long as the cilia comb is needed. Dead ralk are shuffled down to the magut crown, absobed into the dakuth's mesoglea, and repurposed into spicules.  

Bell Cavity

During the first three stages of growth, the ralkine bell's primary purpose is aiding in diving and orientation. The bell is lighter than the rest of the body, ensuring that the individuals can easily correct their horizontal positioning and by adjusting its gas mixture and pressure they can dive or rise.  

To avoid disorientation while swimming, planula and medusa typically propel forward in short bursts and try to avoid tilting their body more than 45°. Horizontal movement is done in s-shaped leaps, where the dakuth swims up at an angle and then slowly sink back to the correct depth.

— Notation by Dr. Tybulus Svilen

  Once the dakuth matures and transitions to primarily terrestrial living, it sacrifices most of its diving ability. The bell is repurposed into an aquarium or terrarium to cultivate a microcosm in, with the intent of it eventually becoming a fully self-sufficient holobiont. The gas and pressure alterations needed to dive and rise would damage or outright destroy the microcosm.

The magut forms a shell that encases the lower half of the dakuth and protects their organs. It's formed from a dense, jelly-like connective tissue closely resembling the mesohyl found in some sea sponges.  

Cobweb Skeleton

As a measure to ensure that the mesohyl retains its shape and integrity even in lower pressure environments, it can be supported by a so-called cobweb skeleton. This is made from ralk being sacrificed into spicules and migrated into the mesohyl. The spicules arrange into cobweb-like structures that act as support beams between the outer cell plates.  

Cell Plates

The outermost layer of the magut is hardened into thick, plate-like cells with the texture of coral stone, and is capable of withstanding an atmospheric pressure as high as 1.6k Atm. In drier environments a thin layer of transparent mucus keeps it sufficiently moist and safer from airborne contaminants.   Neuroaural Receptors
The cell plates close to the magut's crown is lined with rounded depressions filled with fine filaments. A cluster of nerve fibers connects each one with the circulatory system. The filaments are sensitive to vibrations and particles in the air and water, and will forward these to the nearest ganglia to be translated and interpreted.  

Ostia & Radial Canals

A number of tubular channels, called ostia, connects the dakuth's gastrovascular cavity with the external plate cells. These are intersected with several rounded chambers, called radial canals. The ostia and radial canals are primarily used for passive filter feeding, but also serves a role in reproduction in medusa and adult dakuth.   When used for filter feeding, half of the ostia are designated inlets and the other half outlets, with myocyte membranes by each opening aiding in controlling the speed of the water flow. The insides of the radial canals are covered with filaments to capture edible particles from the passing water and transport them down to the gastrovascular cavity.   Brood Chambers
During the medusa and adult growth stages the radial canals closest to the outer cell plates layers are repurposed into brood chambers, each with only a single unblocked ostia to allow its contents to be flushed out of the dakuth when needed.   Secondary Photoreceptors
In verds, the brood chambers and their ostia are fused together to a single wide cavity with an opening covered by a myocyte membrane. The haploid planula hatched in each of them are oriented so the sensory organ faces outward and will in time grow to fill the entire cavity and fuse with the canal wall. By remaining connected to the circulatory system, they receive nutrients and pass on their sensory information to the dakuth's ganglions.   Myocyte Membranes
Every opening between cell plates, and between the ostia and radial canals, is lined with a tough muscle tissue shaped as a circular mouth. Their primary function is to serve as valves for controlling the flow rate of liquid through the ostia and radial canals. Being both airtight and watertight, they are also used to close off the external openings into the magut when needed: the ostia, tentacles, proboscis, and manubrium can all be sealed into the magut shell for protection.

The body of the dakuth is vaguely heart-shaped, with a rounded bulb on top that becomes more pronounced with age. It's made from a thick, jelly-like connective tissue closely resembling the mesoglea found in certain cnidarians. It functions as a hydrostatic skeleton and protects the inner organs suspended in it. The magut shell and a thin rubbery epidermis keeps the mesoglea encased and helps preserve its shape.  

Ganglions

Orb-like knots of fine tissue serve as a combined heart, brain, and nerve center. The number and mass of ganglions found in a dakuth is proportional to their size and age. When subjected to an outward stimulus, nerve impulses are sent to and processed by the closest ganglion, allowing for improved reaction times. They are also able to operate individual appendages and other bodily functions independently, allowing several operations to be performed simultaneously.   Damaged or dysfunctional ganglions will normally undergo internal cannibalization and be replaced. This arrangement mean they have no vital organs and won't be disabled unless most if not all ganglions suffer considerable trauma. But it also means that their accumulated experiences is divided between these ganglions. Loss of a ganglion would incur an irreparable loss of the knowledge, skill, and memory stored in it.   Primary Cereganglia
During the later medusa stage, one ganglion will grow to two to three times the mass of brain cell tissue compared to the rest. This ganglion triggers the emergent sapience and will function as a central organizing hub for the dakuth's consciousness. It has a degree of control over the other ganglia, in that it can attempt to force or suppress instinctual responses to stimuli they're exposed to, or it can delegate a task or action to performed by them. After the action/task has been delegated, the ganglia is fully capable of performing it on its own with no further influence or concentration needed from the primary cereganglia.   Primary Photoreceptor
This is a specialized ganglion that forms at the top of the dakuth already in the planula stage. It only contains nerve tissue and develops several features found in the ocular organs of other species. Its primary function is to maintain correct orientation and absorb sunlight needed for their biological processes. Polyps and medusa also use it for spotting prey, while adults and verds use it to store radioactive energy and heat for later use in maintaining bodily functions and/or ideal conditions in their microcosm.   Dakuth strive to always keep the primary sensory organ facing the sea's surface or the sky. Failure to do so leads to dizziness and disorientation after just a few minutes. Prolonged misalignment worsen the symptoms, and the dakuth will eventually lose consciousness.   Rete Mirabile
Another specialized ganglion, composed of a complex of veins and chambers, is utilized as a countercurrent exchanger. Heat, ions, and gases can be exchanged between the vessel walls for the purpose of finetuning temperatures, gas mixes, and solutes before transporting them elsewhere. Some functions the rete mirabile assists with is controlling pressure and gas mixture within the bell cavity, regulating body temperature, and filtering toxins and contaminants from the circulatory system.  

Circulatory System

Connecting the gastrovascular cavity, ganglions, and other body tissues of both the dakuth, magut and ralk is a net-like tissue. This tissue is responsible for transporting oxygen, nutrients, and nerve signals around the body. It also collects waste byproducts and transport them back to the gastrovascular cavity.   Gastrovascular Cavity
At the bottom of the body is a large sac connected to the manubrium, ostia, and the circulatory system. It's divided into several folded chambers to aid with separating edible matter from inedible dito and various accumulated waste byproducts, that will be expelled either via the outlet ostia or via the manubrium. Once edible food matter has been properly separated they're broken down by digestive enzymes secreted through the chamber walls, and the resulting nutrients are transported out through the circulatory system.  

Appendages

Over the course of its growth into adulthood, dakuth will develop three types of appendages from the proto-tentacles left behind after it was separated from the brood chamber wall as a planula. These are the manubrium, tentacles, and the proboscis. When not in use they can be retracted into the magut shell and protected behind a myocyte membrane.   Manubrium
Poking out through an opening at the very bottom of the magut shell is a mobile appendage, loosely resembling a trunk, with two thick gripping prongs. This serves as a mouth and is used for ingesting food matter that is too large to be filtered into the gastrovascular cavity via the ostia, and as an outlet for expelling waste.   Tentacles
The planula proto-tentacles will form into the first set of three tentacles as a dakuth become ready to transition to the sessile polyp-stage, where they're used to anchor onto sea bed terrain such as reef corals or rock formations. They can develop one to two more sets of tentacles, that would be used longside the proboscis for snatching and holding onto prey, or for locomotion if they are forced to relocate. Medusa sometimes grow an additional set of tenacles, and at this stage their primary function is grappling and strangling prey.  

We've found no indication that genetics or environmental factors determine the number of tentacles a dakuth gain by the time they reach adulthood. It may very well be random.

— Notation by Dr. Tybulus Svilen

  Proboscis
During the polyp stage, a dakuth develops three proboscis that are circa four thirds of the length of their tentacles. Each end in a leaf-shaped pad with a droplet-shaped opening in the underside's center. It's ability to grip and manipulate is improved by dividing the pad's surface with grooves made from thin, cord-like tissue that act as quasi-joints and fastening points for a firmer, more muscle-like tissue.   The opening in the pad's underside connect to an extended manubrium, allowing the dakuth to ingest softer food matter directly by just holding onto it. When not feeding, the opening is protected by a myocyte membrane.

The neuroaural receptors of the magut act as a combined olfactory and aural sensory organ, where the fine filaments filling the depressions are very sensitive to the touch of fine particles or vibrations carried through their surrounding medium.   Dakutha lack the necessary organs to translate vibrations into sound as most hominin species experience them, but are able to better distinguish between different sources of vibrations. They're capable of granular detection of changes in ambient temperature and humidity shifts, and can use a planet's electromagnetic field to orient themselves.   Similarly, they lack the ability to scent or taste what they're ingesting, as they have no internal olfactory and gustatory organs.
 

Sub-adult dakutha only have the primary photoreceptor that act as a visual organ, but its only able to detect ambient light levels and tracking the direction of the surface/sky.   The secondary photoreceptors developed later in life similarly operate by detecting ambient light levels and map surrounding terrain based off of how light reflects on it. They can only discern colors in the ultraviolet spectrum, but aren't able to make out finer shapers and details.

Dakutha's sense of touch varies between their body parts. The magut has nearly no surface axons able to send nerve signals outside of the neuroaural receptors; few are able to feel their shell or legs.   The ralkine bell sits on the opposite end of the spectrum: if not prepared for it, even lightly applied pressure can result in mass death of the colony. This is considered agonizing, as the ralk colony will flood the primary cereganglia with warning signals and cause an overwhelming amount of pain.   Their proboscis and tentacles have several times more surface axons able to send nerve signals than most hominin species, but they are not as sensitive as the ralkine bell.

During the planula stage nutrition is gained passively by the magut filter feeding for plankton and depositing harvested food matter into a shared gastrovascular cavity, where digestion takes place and extracted nutrients are distributed through their circulatory system.

Once in the polyp stage and onward, they will extend their diet by actively foraging for edible plants, algae, fungi, and animals that happen to pass within reach and depositing directly into the gastrovascular cavity through the mandubrium. Developing proboscis and the tentacle spines allows the dakuth to more actively hunt for and process food. Once the mineralization of their primary tentacles into legs is finished, they will also begin to search for food on the ocean's surface and on land.

Once the dakuth has developed its symbiont microcosm, usually years after reaching adult form, they will switch from earlier modes of nutrition to rely primarily on saprophagy and chemoheterotrophy. The dakuth gathers detrius from their enclosed ecosystem and digests it in their gastrovascular cavity. After extracting nutrients from the detrius, the remaining basal components are added back and serve to remineralize the soil or sediment of their symbiont microcosm. Excess gases such as carbon dioxide, hydrogen sulfide, and ammonia created as a byproduct of this process or by the microcosms own ecological cycle, is caught and processed into nutrients through chemosynthesis by the ralk colony - access to sunlight makes this process more efficient, but is not required.   In the case their symbion microcosm, for one reason or another, is unable to provide enough nutrition to support the dakuth, they will supplement it with magut filter feeding and/or active foraging.