The Plankton
The tiny phytoplankton of this age is mainly composed of specialized cyanobacteria and certain other photosynthesizing micro-organisms; this in turn is preyed upon by many tiny kinds of zooplankton, mainly composed of the larvae of various marine invertebrates. There are also larger members of the plankton, visible to the naked eye, that actively seek out other planktonic organisms as food.
After the various catastrophes that wiped out more typical kinds of zooplankton seen in our time, new varieties have evolved to fill the resulting gaps in the ecosystem. Some of these may seem unusual to our eyes, such as the Criggs, a kind of macroscopic, free-swimming rotifer, ubiquitous in the fertile currents of the open ocean.
The Lesser Crigg (genus Penicillops) is a rather typical member of the group, measuring no more than 3 millimetres long. As with its ancestors, the mouth opening culminates in a crown of filaments used to snag microscopic prey from the water, but here it has become larger, almost brush-like. Criggs such as this wriggle about in order to move through the water column, and usually occur in swarms that may number millions. The body terminates in a small gripping foot, typical of the group, which is most often used to occasionally cling to floating objects, or each other.
The Least Crigg (genus Nanocorona) is even smaller, only 1 millimeter long, but generally similar, using its brush-like crown of oral filaments to snag microscopic kinds of plankton from the water. Sometimes they may cling to each-other in large congregations, in order to drift passively in the current, but they are still able to swim freely.
The Snagger Crigg (genus Venatomastax) is the largest kind of crigg, at about half a centimeter long. Generally only occurring in small swarms or as singletons, it swims actively in search of smaller kinds of zooplankton which it seizes in its large trenchant mouthparts.
Comets are a very common kind of zooplankton, ranging in size from less than half a centimetre to as long as your pinkie finger, they row through the surface waters in large swarms. These creatures appear almost totally alien, but their earthly origin is fascinating, they are neotenous starfish. They maintain a body shape which has evolved from that of the swimming larvae of starfish, but these creatures reproduce and spend their entire life-cycle in this form. Comets have mouths ringed with stiff filaments that sweep the water for various microplankton, they have fringes of filaments on their swimming appendages that aid them in propulsion.
Greater Comets (genus Pelagaster), are among the bigger kinds of comet, reaching about 5 centimeters long. They form large swarms of many thousands, which drift and swim about in the water column, snatching smaller planktonic organisms. As with all comets, they have eyespots which allow them to navigate, evade and tell night from day.
Moustached Comets (genus Mustachiaster) are smaller comets that only reach about half a centimeter long. These tiny creatures drift in huge swarms of many millions, paddling furiously to navigate against the current, or towards sources of food. They feed mainly on smaller plankton, which they catch on their mucus-covered bristly mouthparts.
Winged Comets (genus Pteroaster) are mid-sized members of the group reaching about 1.5 centimetres long. Being more active swimmers than other comets, they have a streamlined shape and large appendages. Swimming about in large swarms of up to several million, they constantly catch smaller planktonic organisms with their bristly mouthparts. When comets spawn, they release their gametes en masse, which hatch into tinier, less developed versions of themselves, in fact these minute juveniles are common prey of adult comets.
Clambirds are a kind of noticeable zooplankton. These bivalves have deviated from the typical form of their ancestors. Their shells form a pair of streamlined flappers or wings that propel them though the water much like a bird would through the air, the tapered head, mouth and body are attached underneath. They filter the water much as a typical clam or mussel does, taking in water through its front orifice, and expelling it again after extracting food.
The Blue-eyed Clambird (Pterovalvia hyacintoluscus) is a fairly typical member of the group, with a width of only 4 centimetres across the shells. These clambirds swim about in loose shoals of up to 700 in the open ocean, constantly filtering the water for plankton as they go. They can put on a turn of speed by rapidly flapping their bivalved shells, but they are commonly preyed upon by larger filter feeders and predatory members of the zooplankton.
Fwirms are another larger member of the zooplankton, these are descendants of polycheate worms that have convergently evolved a fish-like shape. Some kinds are only a centimetre or two long, and feed on smaller kinds of plankton selectively, whilst the larger forms can be as long as your middle finger, and use mouths full of bristles to sweep up plankton. Some forms are voracious tiny hunters with raptorial mouthparts, which prey on other fwirms, comets and clambirds.
The Anchovy Fwirm (Vermichthys anchovetta) is one of the bigger planktonic fwirms, reaching about 10 centimetres long. They swim in large shoals of up to many thousand, using their facial bristles to sweep smaller plankton into their mouths. These shoaling fwirms form the basis of the diets of many other open ocean creatures, much as baitfish did in our time.
Wrill (Vermicaris minutus) are tiny fwirms no more than 2 centimeters long, which feed selectively on smaller plankton in the open ocean. Their shoals often number in the many millions of individuals, and larger filter-feeding creatures such as sea-blimps rely on these shoals as a main source of food.
Nipper Fwirms (Gnathovermicthys rapator) are tiny voracious predators that live in small loose shoals. Reaching about 7 centimeters long, they prey on many other types of larger plankton, including clambirds, fwirms and comets. They possess large raptorial mouthparts that allow them to catch prey even larger than themselves.