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Glass Marephasmatis (Amarungophasmatis vitrifer)
Creator: Primalpikachu
Ancestor: Rainbow Marephasmatis
Habitat: LadyM Ocean, Jujubee Ocean, and Mnid Ocean (midnight and abyssal zones)
Size: 4cm long
Support: porous silica exoskeleton
Diet: filter feeder, (planktivore and marine snow)
Respiration: passive (diffusion through skin)
Thermoregulation: ectotherm
Reproduction: Sexual (broadcast spawning two genders)

Splitting from its ancestor, the Glass Marephasmatis has taken up a sessile lifestyle in order to avoid predation in the open ocean. It has radial symmetry and consists of a vase like body anchored with a porous silica outer coat and a singular nematocyst lined tail that is used to capture food. In the dark depths of the abyssal zone, it creates shimmering light using the symbiotic crystal flora in its body.

When they are born, the young are free swimming and lack the tough silica coating the adults have. They use their tail and body to find an appropriate spot to settle and once they have found a suitable rock or hard surface, the young will attach the front part of its body to the surface with a glue like protein. Then, the vitreous exoskeleton will slowly develop around the organism, permanently anchoring it into place. This exoskeleton is not water tight however; it is covered in small pores that allow for the diffusion of materials both in and out of the organism.

The Glass Marephasmatis is primarily a filter feeder. The nematocyst lined tail is able to capture any food that happens to brush past it. Once the nematocyst fires, it injects a potent toxin and enzyme cocktail that instantly kills and begins to digest the prey. The prey is then absorbed directly into the body by the tail where the nutrients are distributed throughout the body.

They are found exclusively in the midnight and abyssal zones of the ocean where they seem as shimmering jewels on the dark rock faces. The close proximity of conspecifics makes it advantageous to breed via broadcast spawning.

This post has been edited by Primalpikachu: Sep 11 2022, 12:39 PM

Why does it eat through its tail instead of its mouth?

If I am reading the picture of the rainbow marephasmatis correctly, the mouth would now be the base of the glass marephasmatis. if not, that can easily be changed by me

This post has been edited by Primalpikachu: Sep 11 2022, 12:43 PM

The mouth is opposite the tail. Why did it evolve to stop using its mouth to eat and to use its tail instead?

Please trim the excess white space in the image.

If you don't want to re-draw it, it may be possible to overhaul it to feed through silt like a sea cucumber. This is a bigger change, but you could also adjust its habitat depth and make it full of photosynthetic symbionts, and so live like an upside-down jellyfish (Cassiopeia).

QUOTE (Disgustedorite @ Sep 11 2022, 03:56 PM)

The mouth is opposite the tail. Why did it evolve to stop using its mouth to eat and to use its tail instead?

In order to escape predation in the open ocean, the glass marephasmatis used its mouth as an anchoring point to affix itself to a hard surface. Despite the loss of its mouth it is still able to feed because of its basal physiology; thus, digested nutrients is easily able to diffuse into the body from the tail. The inverted position has the added benefit of protecting the main body from harm with the outward facing stinging tail.

If this seems too implausible, I can instead use the pores over the body to filter feed like a glass sponge which is what I partly based it on.

This post has been edited by Primalpikachu: Sep 11 2022, 01:11 PM

Is there precedent for this in a real-world animal? The tail is ectoderm while the digestive system is endoderm and I don't think they can just switch like that.

QUOTE (Disgustedorite @ Sep 11 2022, 04:52 PM)

Is there precedent for this in a real-world animal? The tail is ectoderm while the digestive system is endoderm and I don't think they can just switch like that.

I don't think there is unfortunately. do you think my pore idea might fare better in this case?

QUOTE (Disgustedorite @ Sep 11 2022, 04:52 PM)

Is there precedent for this in a real-world animal? The tail is ectoderm while the digestive system is endoderm and I don't think they can just switch like that.

Sorry to kind of barge in (is it okay to do that in these circumstances anywho? If it isn’t I don’t repeat it again in the future), but, I do know quite a few internal parasites (a good example would probably be tapeworms) probably had to make the transition from using an actual mouth and stomach to absorbing nutrients through their skin.

On the other hand, this switch probably only works for said parasites because they’re literally sitting in a stew of nutrients, so unless this originates in extremely eutrophic waters or they have some manner of effectively releasing and concentrating the nutrients from their killed prey/captured detritus (perhaps a symbiotic decomposer?) I do doubt it’d work out like that.

This post has been edited by Oofle: Sep 11 2022, 04:06 PM

The nematocytes inject enzymes that effectively digest the prey/nutrients from the inside out. The nematocysts also holds the prey close to the tail, so the digested prey soup is quite concentrated at the site of absorption.

This seems like a really big jump though. Wouldn't it be easier to evolve to have nematocysts around the mouth?

There is a precedent other than parasites: hagfish. A hagfish can absorb nutrients through its skin. Admittedly, this surely becomes relevant only or largely while it's burrowing through a rotten carcass, which is a situation sort of similar to that of a tapeworm's.

One source says: "Most echinoderms can absorb dissolved food through exposed skin".

However, I am not sure how plausible it would be to implement in this organism. As a compromise, you could add both digestive processes conventional for the line and, as a minor ability, absorption of nutrients through the skin. If it lives in the open ocean, but not deep enough for nutrient-mixing layers, then the amount of food available would be limited. Therefore, it would have a sort of evolutionary incentive to evolve nutrient absorption through its skin to supplement its diet.

Any update on fixing/explaining this?

Graveyarding at creator's request