Biological Aspects

Biological Aspects
Blood color seems to have several biological consequences in addition to the social consequences of the caste system. Troll tears are apparently the same color as their blood, though more diluted in color. Trolls lower on the hemospectrum are more likely to have psychic powers, but are more psychically susceptible as a result. On the other hand, trolls higher on the hemospectrum seem to be more physically strong. Another obvious aspect is the different anatomy of land- and sea-dwelling trolls. The latter sport fin-like protrusions and organs that allow them to live underwater.

Equius remarks that Gamzee has the highest blood possible for a landdweller and is as such more prone to violence and murder than the rest of them. Equius also states that he dreads to think what he would be without the pacifying influence of his moirail, Nepeta. This implies that trolls gradually become more psychopathic/violent the higher they are on the hemospectrum. This would mostly be in line with the twelve trolls followed in Hivebent, as the trolls below Terezi on the spectrum are fairly "harmless", while from there onwards the trolls display some unnerving behaviour peaking in Eridan's outright genocidal tendencies. The only true exception seems to be Feferi, who, despite being at the very top of the hemospectrum, displays no negative tendencies, although she might only be suppressing them by force of will, since she was screaming while attacking an imp here. On a possibly related note, Aradia starts displaying more violent behaviour after entering her blue blood-fueled Soulbot.

In a dream bubble conversation Terezi has with Aranea, who was masquerading as Vriska at the time, it was implied that high-blooded trolls are tougher than low-blooded trolls and likelier to survive grievous injuries. In the same conversation, Aranea states that the trolls' violent behavior is a result of Doc Scratch's conditioning of their race, implying that the high-blooded trolls may not be as unstable as was previously thought.

A troll's lifespan is also tied to the hemospectrum with the lowest castes having lifespans similar to humans, with the lowest two being slightly shorter than humans with the lowest caste living for a dozen, or a couple dozen, sweeps (roughly 30 to 50 years in human terms). Starting at the greens, lifespan starts moving beyond a century and by the highest caste lifespans reach hundreds of millennia, potentially even millions. Mindfang, a cerulean blood, wrote in her journal that she expected to live for centuries and predicted the Summoner (Tavros' ancestor), who was destined to kill her, may very well not hatch for many sweeps, given the shorter lifespan granted by his lower position on the hemospectrum. Kankri stated inOpenbound that cerulean bloods with their centuries long lifespans could outlive hundreds of generations of burgundy, bronze, yellow and lime bloods, and dozens of generations of midbloods.

Some castes have uneven sex ratios. For example jadebloods are almost entirely female, the three blueblood castes (cerulean, indigo and purple) are mostly male, and fuchsia bloods have been consistently referred to as female (empress, heiress etc.).