Sea Bamboo and Aquatic Ants

Sea Bamboo

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The tropical climate of the Thermocene has been very beneficial to the bangroove forests - salt-tolerant, colonial bamboo trees which thrive along warm sea coasts. Formerly restricted to the shores of a small band of warm shallow waters near the equator, they now have a global distribution. Over the eons, some have become further adapted to life in the sea and lost their tether to the shore completely. The trunk-forming nature of their rhizomes has diminished for it is no longer necessary for the plant's survival, the rhizome reverting to a more primitive form which creeps along shallow sea beds and sends down roots to secure a hold in the sand or mud. From this tether numerous thin and flexible shoots are produced which grow upward toward the surface in thick tangles. The shoots grow indeterminately, eventually reaching lengths of a hundred feet or more, the upper portions forming a floating tangle of stems along the water's surface which provide extremely important refuge for many small aquatic animals including fish and crustaceans. The stalks are thin - sometimes no fatter than a pencil - but are highly bendable and difficult to snap outright even in the most turbulent conditions, for they are very low in the lignin which lends strength and rigidity to the stalks of most of its relatives.

These new sea-going bamboo are totally aquatic; they respire underwater, with long, strap-like but paper-thin leaves which absorb carbon dioxide directly out the water column and produce bubbles of pure oxygen in return. Though the majority of growth is now vegetative, sea bamboos still flower. Their flowers are small and not very conspicuous, being born near the stem at the junction where the leaf attaches to the stalk. They are self-fertile, able to produce seed without pollination from another plant - necessary since many colonies may be made up almost entirely of a single genetically identical individual - but are also pollinated by the currents which spread their genetic material across the sea, and to some extent the actions of small shrimp and copepods which feed on their pollen, inadvertently transferring some to other flower pannicles as they do so, almost like underwater honeybees. Like their shore-growing ancestors, aquatic bamboo shelter their large seeds singly in very long pods, sometimes weighing several pounds and growing as long as a baseball bat. These massive fruit, many times larger than the flowers that gave rise to them, take as long as a year to develop before being shed into the water and, like their ancestors, begin to sprout before they even leave the parent plant. They are buoyant enough to remain floating at sea for as long as a year, during which time the seedling is able to rely on the large store of energy in its pod and produce a dense tangle of roots which grow downwards into the water column. Eventually, with luck, the seedling will wash into shallow waters and be able to anchor itself to the seed bed with a rhizome. If it doesn't, however, this is little problem. The rhizome of the sea bamboo no longer serve much purpose except as an anchor and it is the stems which absorb most nourishment from the water column. Thus a seedling can survive and grow a dense colony of leafy stems and roots entirely suspended in open water, forming an isolated floating micro-habitat until it eventually washes into shallower waters and is able to gain a hold on the sea bed. Such small, entirely free-floating colonies are frequently seen hundreds of miles out to sea, where they again provide vital shelter to young fishes and small aquatic animals. Though most colonies eventually anchor when they wash into coastal environments, some may spend many years floating and become quite large, almost akin to a buoyant reef full of life in the otherwise seemingly barren pelagic zone.

Sea bamboo are not only important to the survival of small marine animals; many large marine animals feed upon their foliage, such as pelecanaries and gigaducks, and the plants' large seed pods are rich in sugar and fat, attracting many opportunistic animals that otherwise would be considered carnivores. Even porporants, obligate predators in the truest sense, may feed on these fruits when they are available, varying their diet in a way many predatory land animals will do on occasion but which, until very recently, simply wasn't an option for oceanic ones - that was, of course, until the evolution of the world's first truly aquatic fruit. Because sea bamboo gains no benefit from animals consuming its seeds, however, as some land-growing kin do, most attempt to deter predation by coating the edible flesh of the fruit with a thick, bitter-tasting peel.

Sea Ants

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A group of ants has followed the sea bamboo into the ocean. Descended from the mangrove ants which sheltered from the rising tides in hollow nodules produced by their host plants, they too are completely aquatic, though they have not lost the need for atmospheric oxygen like their host plants and still need air to breathe. They have solved this need to breathe in a most novel way, however, which can allow the insects to stay underwater for weeks at a time. Their thorax and abdomen are covered with a dense layer of "hair" - actually setae. The hair is used to trap a thin coat of air over the insect's body and around its spiracles which is able to serve as an external lung, absorbing dissolved oxygen from the water and dissipating waste gases. The ant is then able to forage for food underwater almost indefinitely without drowning. To rear their larvae, the ants chew and stitch together a bamboo leaf into a half-closed tent-like structure, open only from below, which they then fill with air carried from the surface in their hair. To release the air bubble the ants perform a dramatic, rapid shaking behavior and then must return to the surface in only a few seconds time or risk drowning. Though the ants normally spend their time crawling along submerged plant growth, they are capable of swimming in times of urgency such as these and propel themselves with kicks of their hind legs, which are flattened along their length into paddles.

above: a sea ant worker; art by Trollmans

Once a nest is established, the workers work reveal something about themselves which differentiates them from most other colonial ants; there is not a single queen in this colony, cared for by sterile workers. Rather every female worker is a sexually fertile queen in her own right, and their cooperation to rear their young is a function of convenience and mutual benefit - they are social, but not eusocial. After finishing the nest, the ants begin climbing out of the water onto whatever small patches of emergent vegetation they can reach floating along the water's surface. From there, they advertise their presence with pheromones and, with luck, soon draw in a male ant. The male of these species is very distinct from its mate; the female is large among ants, just about a centimeter in length, depending on species. Her mate, though, is exceptionally massive - sometimes almost three inches long, with very long dragonfly-like wings (the female is completely wingless), short and stubby legs, and very long, feathery antennae built just for the purpose of detecting the pheromones of females. After hatching he immediately climbs to a patch of bamboo emerging from the water, dries his wings, and takes to the air, landing then only to mate with all of the receptive females he comes across in his travels over the sea. Because he is such a powerful flyer and lives for several months, he may travel hundreds of miles before he finally exhausts himself and drop into the sea for the first and last time, ensuring that even the most isolated ant colonies remain genetically diverse. After mating, the females return to their sheltered nest underwater and deposit their eggs on the walls of the air-filled leaf chamber. When the larvae hatch, the females work together to feed them on whatever small prey they can catch, including fish fry, copepods, shrimp and small molluscs.

Both the male and female sea ant are predatory and have strong grasping arms lined with spines to catch prey and large mandibles designed to subdue it, with the female hunting small aquatic animals, sometimes heavier than herself, either on the bamboo foliage or even which she may chase for short distances in open water, propelled by frog kicks of her hind legs. The male hunts mainly on the wing, feeding mostly upon the adults of a distant relative known as the salt fly, which was one of the first insects which evolved to exploit the riches of the sea many millions of years before the sea ant. These small winged insects are technically ants as well, though their ancestry is dramatically different and their appearance much more like that of a gnat or small fly. No longer colonial at all, their larvae are entirely aquatic and develop in water like those of an Earth mosquito, breathing through a tube on their rear ends and sitting upside down in the water where they reach out and grab any passing organic particles they come across. The ancestors of the salt flies evolved in freshwater environments, like mosquitoes, but moved into the oceans around fifty million years ago and are now found globally, their larvae now forming a significant percentage of the plankton. Adult salt flies live for only a few days and do not feed, but thanks to the widespread tropical climate of the Thermocene have no set breeding season and thus some breeding adults can be found flying over the sea at any time of the year in many regions, ensuring a rich supply of food for hungry male sea ants who need to restore their energy reserves before getting back to business spreading their genes. Catching his prey in his short but sharp claws, he feeds on the wing.

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Meanwhile back the nest, the mated female ants will have now lain their eggs and will soon be carting prey back to the nest to feed the ravenous young. As many as fifty eggs may be lain in a large nest, though usually twenty is the norm. Of these the majority will hatch into females, and the small number of male larvae which are produced are immediately recognized by their mothers due to a difference in their scent. Initially they will feed them all, but as they grow will abandon all but the most vigorous and allow the others to starve, for reasons that will be clear later on. The chosen male, however, is then treated like royalty, given priority at meal times even over his sisters because he must grow far larger than they, who can get by on much smaller portions. The female larvae pupate and emerge as adult ants while their brother is still little more than a constantly hungry grub, which his mother and aunts continuously bring food to for many weeks until he outweighs them by more than twenty times and takes up almost all of the room in the nest, now demonstrating why the females must thin the herd to only the single most vigorous infant lest the nest be overcrowding and possibly be torn apart, drowning all of the young. To keep his diving bell oxygenated as he gets larger, the mothers and aunts as well as his mature sisters now must resume making trips to the surface for fresh air and take away bubbles of that which is saturated in carbon dioxide. Eventually, after several months, the giant baby forms a pupa and, not long after, emerges as an adult ant, which quickly crawls to the surface to dry off and let its wings harden. He takes off within a day, abandoning without a second glance the females which devoted every ounce of their energy to raising him, and is immediately able to hunt - and breed - on his own from then on. The females which raised him will now be so exhausted that they soon die, but his female siblings will go on now to either repair their natal nest or to construct a new one, and to start the cycle anew. Colonies of sea ants are thus much smaller than most other species, rarely more than fifty and often less, but are still formed by sisters - perhaps not all from the same mother and father, but raised together in the same nest by a group of females who also were raised together. If two groups of females come into contact they will fight vigorously, with one either retreating or being overtaken by the other. In the event one colony overtakes another, the winning ants will kill any eggs or female larvae in the losers' nest. However, if a colony produces a nest without any male larvae, they may start war with a neighboring group in an effort to steal theirs and bring it back to their own colony to raise, for though in doing so they will likely exhaust themselves, it seems that - just as in some human cultures - there is a strong drive to rear a son to carry on the family name - or in this case, the genes.

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Though many aquatic animals feed occasionally on sea ants, the small colony size of the oceanic species means that there have not evolved any animals adapted specifically to feed on a diet of ants out at sea, as occurs on land.