Thorny Tudeep
The Thorny Tudeep's most conspicuous difference from its ancestor is the shape of its crystals. As the crystals mature, they become slightly thinner, and project thorn-like sub-crystals from their sides, increasing the amount of infrared radiation it can absorb.
The Thorny Tudeep's metabolism is very similar to that of green sulfur bacteria. Unlike Earthly land plants, it uses sulfur (in the form of hydrogen sulfide) and carbon dioxide to make sugars, not water and carbon dioxide. Pure sulfur is a byproduct of its metabolism, and it excretes the sulfur as a fine powder outside microscopic pores on its shell. The Thorny Tudeep does not require oxygen, and so does well even in environments very low in oxygen. However, its growth is stunted in high-oxygen environments.
The Thorny Tudeep photosynthesizes using red (650-680 nanometers) and near-infrared light, and has become slightly more efficient than its ancestor at photosynthesizing in the dim light around the vents. It is also more tolerant of heat and acidity than its ancestor, and faster-growing, maturing at a time equivalent to 2 Earth years and 8 months. Unlike its ancestor, it has a broad, fleshy mantle of fungus-like tissue and much more horizontal roots, which are normally hidden under the silt. The mantle contains small levels of trehalose, a sweet-tasting energy-storing carbohydrate. It draws upon the stored energy in the mantle to regenerate from attack by predators, such as the Tudeep Sucker.
The interior of the Thorny Tudeep is filled with pulpy strings of chitin, and its flesh is full of grapefruit-esque mercaptans, making it smell somewhat like grapefruit. The Thorny Tudeep’s fungal flesh contains a unique chemical called "ganntunine", which disables the enzymes the Tudeep Sucker uses to defend itself against the Carpotestan Thermaparasitica. In effect, it weakens their immune systems. Strangely enough, it's possible for ganntunine to weaken smaller, weaker Tudeep Suckers' immune systems so much that the Carpotestan Thermaparasitica's close relative, Protopathogena infecta, can manage to become a mild, localized infection. Otherwise, P. infecta is very rapidly destroyed by the Tudeep Sucker.