Tigersnail
Basic Information
Anatomy
The tigersnails’ anatomy is believed to be quite similar to the ancestor of its clade. The radula and esophagus are both still present, however the ctenidia are now located in a large, water-filled pouch (ctenidian coelom) that is separated from the esophagus by two valved tubes. Water flows into this pouch from one tube oriented towards the front of the esophagus, and it exits through another tube that empties out into the mouth itself. This system has allowed the organism to have a unidirectional current flowing along its ctenidia while protecting them from particles far more efficiently, overall improving its respiratory system dramatically. This pouch has also expanded in size quite significantly; so much so that it is now located majorly in the body tagma. Consequently, the tigersnail has lost its external gills entirely - all that is left of them are vestigial bumps along the underside of its body.
In terms of tagmatization, the tigersnail has begun to undergo a merging of the head and body tagmata to some degree, as the two now have an overlapping zone referred to as the intertagma. Within the intertagma rests the ctenidian coelom, as well as the entrance to the stomach and numerous muscles that enable the creature’s head to extend outwards or be retracted into the shell. While both the cranial and abdominal tagma remain distinct, this overlapping zone could be indicative of the early stages of tagma-reduction.
The posterior tagma has expanded significantly compared to its ancestors, and is now the largest tagma in terms of length - constant of almost half the creature’s entire length. This tagma is now mostly dedicated to shell production, however it also houses the gonads. The posterior anus has been relocated to the abdominal tagma, with the intestinal tract no longer entering the posterior at all. The rear-most four limbs have moved forward on the organism to keep them outside of the shell. The posterior anus opens up between the hind four limbs, allowing deposition of waste and mobility along the seafloor.
An additional advancement has been made in the form of a hard, bony structure on the surface of the head, which serves as a seal and protective carapace for when the head and body retract into the shell. This allows for the shell to be effectively sealed when the organism is threatened, as the shell itself lacks a valve seal or enough depth to offer such protection on its own.
The digestive gland of the organism has also undergone modifications to allow a significantly increased production of sillicytes - cells filled with citric acid that are specialized to transport silicates - to enable faster shell growth. Additionally, an increase in symbiotic microbes allows the tigersnail to utilize them as a means of performing the glyoxylate cycle - a process that allows the conversion of fats and fatty acids into carbohydrates - thus enabling it to avoid needing to break down proteins to create glucose to some extent.
Genetics and Reproduction
Tigershells are diploid simultaneous hermaphroditic organisms with a year-round mating season. Much like the tailshells, tigersnails are solitary organisms that mate whenever they encounter another member of their species. However, rather than engage in a wrestling match where the winner fertilizes the eggs of the loser, tigersnails fertilize both parties' eggs externally.
When two tigersnails encounter each other, each will lay their eggs into a small nest dug into the sediment. Eggs are laid from the abdominal anus into a clutch of about 10 eggs, which are then fertilized by the other party and buried into the sediment. After this, the mated organisms will abandon the eggs, and will refrain from mating for at least three local days. During this time, they will secrete pheromones into the water as a means of signaling to other members of their species that they are unable to mate. This serves a dual purpose of alerting other members of their species to their location (thus when they are able to mate again, potential mates will be close by), as well as ensuring that they are not approached while they replenish their gametes.
Growth Rate & Stages
Tigersnail eggs hatch after about fourteen local days, in which they will dig themselves out of the sediment. While they resemble miniature adults in many ways, their gametes are wholly underdeveloped, their posterior tagma is not elongated, and they lack an external shell. In order to survive during this phase of life, the tigersnail naiad remain nocturnal - relying on the cover of darkness to protect themselves. It is likely that they will mainly subsist off of retinalphyte sap and small bits of carrion that they can burrow themselves into. 80% of all naiadd born will die during this phase of life.
Should these organisms survive long enough to develop their shells (approximately 30 local days), they will have reached a size of about 6-8 cm in length. While they are still incapable of reproduction at this phase, they are identical to adults in all other ways. They will continue to grow for the rest of their lives, although their growth rate will slow significantly after around 1 local year. By this point, they have usually approached their adult size (though are usually a centimeter or two smaller) and their gametes are fully developed.
Ecology and Habitats
Tigershells evolved along the eastern coastlines of Kub-Shay, and have since radiated out from this location. Fossils can be found from the later portions of this phase all across the coastline of Kub-Shay and southern Artica. Occasionally fossils can be found around the coast of western Niylan, however such finds are incredibly rare - it is likely at this time that the tigersnails were just starting to adapt to the sulfur-rich waters around Niylan
Dietary Needs and Habits
Tigershells are omnivorous animals, and feed on a wide variety of organic material. Most commonly they can be found grazing on small retinalphytes and phytozoans, as well as drinking the sap from phytozoan plants; this is unlike the tailshells, who prefer the sap of retinalphytes. Unlike tailshells, however, tigersnails cannot rear up through the use of their posterior tagma - thus limiting them to small retinalphytes and phytozoans growing along the substrate.
Tigershells also require animal tissue as a fundamental part of their diet (it is their main source of protein) however they are not known to be predatory. Rather, tigersnails gain protein by consuming carrion they find while scavenging. When carrion is found, tigersnails are known to burrow into the carcass if it is large enough as a means of avoiding being forced away from the carcass by other scavengers. After burrowing into the corpse, they will slowly consume it from the inside out before moving on to find more plant matter to consume.
Additional Information
Perception and Sensory Capabilities
The tigersnail has undergone several minor advancements to its eye structure. While the opsin clusters are not present in kelyfoicthyans (due to gene AO15), the camera-type eyes have adapted to take on the roles that these opsin clusters take on in other cephaloptins. In particular, the optical nerves have segregated themselves to specialize in the transmission of specific types of visual stimuli. The uppermost nerve transmits information regarding light levels to a small nerve cluster located behind the eye, which analyses this information as a means of tracking the day-night cycle and seasons; this information is in turn submitted to the central brain for analysis and use. The lowermost portions of the optical nerves are dedicated to the transmission of visual stimuli regarding individual colors, which are analyzed by another nerve cluster at the base of the eye-stalk for analysis. The information is then submitted to the brain, allowing the tigersnail to carefully analyze visual stimuli in a highly comprehensive, efficient manner.
Symbiotic and Parasitic organisms
Tigershells rely on prokaryotic microbes and other microbial organisms to perform the glyoxylate cycle with fatty acids provided by the tigersnail. This process enables the tigersnail to be able to convert fats directly into carbohydrates and glucose without having to break down as much protein to sustain its glucose levels during times of starvation. This also allows the tigersnails to make better use of lipids consumed from carrion when opportunistically scavenging.
Genetic Ancestor(s)
Scientific Name
Portokalyfos portokali
Origin/Ancestry
Xenosegmenta
Lifespan
7 local years
Average Height
8 cm
Average Length
15 cm
Geographic Distribution
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