Major taxonomic kingdoms

Complex, multi-celled life on Eurus is grouped into five main kingdoms, as opposed to the three kingdoms of the eukaryotes of Earth. Of course, there are many divergent lineages that don’t fit into these, much like Earth’s protists, but these are the largest groupings.  

Erythroplasta

These organisms are similar to the plants of Earth, engaging in carbon dioxide photosynthesis and releasing oxygen into the atmosphere. They also use atmospheric ammonia as a source of nitrogen for protein production. This process releases hydrogen, contributing to the small amount of hydrogen present in the planet’s atmosphere, although it is eventually released out into space. They tend to use carotenoids as their photosynthetic pigment, rather than chlorophyll, giving them colours ranging between yellow, orange, and red.

Erythroplasts are more abundant near the equator where conditions are more stable throughout the year, although the taller species don’t grow as well during the windy season.

Cyanotriches

Cyanotrichs constitute another plant-like kingdom, with many distinctions that set them apart from erythroplasts. Their cells tend to be long and fibrous, and in addition to photosynthesis, they also engage in chemosynthesis. These plants are more fungus-like than erythroplasts, with many species acting as detrivores feeding off decaying matter. Some detrivores have even lost their ability to photosynthesise, becoming even more fungus-like.

Most species grow during the windy season when the seas retreat, growing on the dried-up sea beds and feeding off of the ample nutrients that are left behind. Since, near the equator, the sun is close to the horizon during this time of year, there is much less light available, so they’d be unable to sustain themselves on photosynthesis alone. This is where their ability to chemosynthesise and feed off of decaying matter give them an edge. They have various means of obtaining chemical energy, including the oxidation of atmospheric hydrogen, ammonia, and methane, as well as carbon dioxide reduction.

Because they grow close to the equator at a time of year when the sun is perpetually setting, most of the light available to them is red and orange. To absorb light from this part of the spectrum, they use the photosynthetic pigment phycocyanin, giving them their blue colouration.

Oxytrophia

These organisms engage in oxygen respiration, using oxygen to oxidise carbohydrates as a source of energy, similar to the animals of Earth. Some lineages are capable of movement, although more primitive groups aren’t. However, unlike Earth animals, oxytrophians with a nervous system have nerves that carry biogenic light rather than electric signals, with their nerves acting as optical fibres.

Methanotrophia

Methanotrophians mainly obtain energy by oxidising atmospheric methane, although they also oxidise hydrogen and ammonia. They tend to grow on the winter-side of the planet during the windy season, using chemical energy in the absence of light. They’re much rarer close to the equator.

Detrivora

Detrivorans feed off dead and decaying matter. They grow during the windy season close to the pole facing away from the suns, feeding off of the dead decaying organisms that grew during the still season and the summer. They are remarkable in their ability to withstand cold temperatures, lowering the freezing point of the water in their bodies by incorporating ammonia. During the summer, all detrivorans on the pole die, leaving behind dormant spores that will grow during the next winter.