Baam

Baams (pronounced /beɪm/) are any of a wide group of giant arthropods that roam the living world of Plex. They are a diverse clade with several hundred identified species—and, given the dearth of biologists on Plex, possibly orders of magnitude more undescribed. Ranging in size from about a meter long to over five meters, baams are found on all parts of the world.

Description

Baams are hard-shelled creatures with compact, ovoid bodies, most but not all species ventrally flattened. They have thick exoskeletons, most brown or dull reddish but some brilliantly colored and patterned. Most baams have four pairs of jointed legs, though there are species with fewer. Many baams bear bristles on their bodies, technically known as setæ.

Though there are some traces of ancestral segmentation, all known baams are monomerosomatous, their segments fused into a single tagma. Still, the part on the front with the eyes (if any) and mouth is weakly divided from the rest of the body by a flexible seam and could be thought of as a head, though it's more technically called the gnathosoma. The rest of the baam's body is called the idiosoma, and in most cases makes up the vast majority of the organism; the gnathosoma is relatively small.

Most baams have three or five small eyes, though a few have one, two, our four, and many species are eyeless. Their mouths, like those of many arthropods, are filled with complex mouthparts, adapted for sucking, cutting, and/or piercing, depending on the baam species. Many baams have prominent "fangs", more technically called chelicerae, and some species also have large pedipalps, in some cases adapted into formidable pincers or claws.

Taxonomy

Though frequently erroneously referred to as giant insects, baams are actually arachnids— a fact that might be obvious to the more entomologically informed by the observation that unlike insects most baams have eight legs. More specifically, baams are placed in the order Trabes of the subclass Acari (and superorder Acariformes). The order Trabes is divided into seven families of baam, though most non-acarologically-inclined inhabitants of Plex may not be concerned with the differences. (The relationships between these families are not clear; some acarologists sort them into two to four superfamilies, but there is no consensus on that classification.)

Alticozidae

Swetches, as baams of the family Alticozidae are called, are relatively small baams, but are known for their remarkable saltativeness. Mechanisms in their legs allow them to extend very rapidly, allowing the swetch to make leaps several times its height. Most swetches are grazers or saprovores, though a few are ambush predators.

Boupestidae

The family Boupestidae comprises the thirns, baams known both for their bright colors and for their deadly venoms. Particularly feared are the spitting thirns, able to project venom tens of meters with alarming accuracy. Thirns are as toxic as they are venomous, their flesh impregnated with poisons, though techniques have been developed to neutralize those toxins, and some have come to consider (properly prepared) thirn flesh a delicacy.

Caetridae

Baams of the family Caetridae, called ligs, are perhaps the most archetypal, and when most people picture a baam what representamen they picture will be closest to a lig. Most ligs have two to four pairs of legs and an oval or aspidate body, with a tiny head (or rather a tiny gnathosoma) in front. Still, the family does include some more exotic species, such as the dragonbaam, a baam with a long "neck" like a snakefly.

Colobathrariidae

The stules of the family Colobathrariidae are dolichocnemic creatures that seem to pick their way delicately across the fleshscape on their long, spindly legs. Some stules are grazers that feed on the flora that grow on Plex's surface as well as on Plex's hair and small appendages, but others are predators, their front two legs adapted to spears with which they can transfix prey.

Ephelidae

The smallest of the baams, the cirns of the family Ephelidae are also the hardest-shelled, their thick carapaces almost impenetrable. They often have a lumpy or stony texture, and would easily be mistaken for rocks were it not that there are few if any actual rocks on Plex for them to be confused with.

Sarotidae

The members of the family Sarotidae, called splents, are known for the "brushes", or scopul&aelig, that line their appendages. They apparently use these brushes in filter-feeding; some splents sift through the hair and bristles growing on Plex's surface to get at the small creatures that hide within, while others are aquatic and use their scopulæ to capture tiny nekton.

Sterronygidae

Known as borrs, baams of the family Sterronygidae are most notable for their chelate pedipalps, which they use for grasping and cutting prey. Some species of borr have chelate cheliceræ as well, giving them two pairs of claws. Due to their claws, borrs are sometimes called "scorpion baams," though they're not related to scorpions (or at least, are no more closely related to scorpions than other baams are). Some borrs are aquatic, lurking in lakes and rivers, and thriving as well in bodies of blood or other body fluids as of water.

Anatomy

Like other arthropods, baams breathe through apertures called spiracles that open into a network of tubes called tracheæ, stabilized by thick ridges called tænidia. Due to the baam's size, its spiracles are more numerous than those of smaller arthropods, and its tracheal system more extensive and complex. While Euterran mites have only a pair of spiracles, baams have hundreds of spiracles in lines across their bodies, and their trachea contain many inflatable air sacs and divide into an intricate network of tiny tracheoles. Baams also have relatively large hearts compared to other acarines (especially considering that some of their much smaller relatives have no hearts at all), tubular in shape and running down their backs roughly where the spine would be in a vertebrate. This heart connects to a system of arteries that debouch into the baam's open circulatory system that bathes its tissues in ceruleanhæmolymph.

While baams possess exoskeletons like most arthropods, they do have internal skeletons of sorts as well. Supporting the internal structure of the baam is a construction called the endosternite, which in some baam species is relatively soft and flexible but in others is as hard as the outer layer of the exoskeleton. Perhaps to better support their large size, the endosternite of baams is much more elaborate and developed than that of their smaller arachnid relatives, in which the analogous structure serves mostly to anchor muscles.

Reproduction and development

Baams are diœcious organisms that reproduce through sexual procreation. In most species, the male and female baam are very similar in external appearance, though some species do exhibit varying degrees of sexual dimorphism, mostly in details of body shape and development though in some genera of lig the female is much larger than the male. Most baams copulate directly to transfer sperm, but others use their cheliceræ or other appendages. After mating, the female baam deposits (in most species) between ten to thirty spherical, transparent eggs.

Baams go through several stages in their development: a newly hatched larval baam is soft-bodied and has only six legs (or fewer, in some species); it then passes through three different nymphal stages before finally reaching its adult form. When it is necessary to distinguish them, the three nymphal forms are called, in chronological order, the protonymph, deutonymph, and tritonymph.