Medusa heads litter the patch reefs of the southern shores, which exist only in the minds of meandering fishermen and maniacs who trample on the flats when the tide drains out and teenagers in tight pants swagger out of saintly power stations to spill their McBreakfasts onto freshly mopped floors and preserve the sanctity of indifferent youth. At Terumbu Bemban on a morning of dampened hormones, foragers caught flat-footed in shallow pools shed all semblance of dignity, paddling away from discovery into dark holes or scrambling over outcrops with the grace of a bathing ape.
Where the reef flat slopes into a crest that is first gentle and soon grim, the corals engage in a campaign of attrition to displace water with a matrix of calcite. Standing at the edge, it is possible to catch a glimpse of a city at war with itself, its inhabitants an assembly of builders who labour in place and conquer by clothing themselves in rising cascades of mineral strength. The colonies that grow on the plateau show their discomfort at straddling two worlds by staying low, flat and small. But it is here that the polyps swirl with only a thin slice of sea between them and terrestrial interlopers.
Corals in the family Poritidae vie with favids for dominance on the intertidal zone, being largely massive or submassive colonies with well-embedded corallites and the ability to brush off choking sediments by exuding a skin of slime. The boulder-like tribes have polyps that strain the naked eye and resemble nothing little more than green-grey rocks with odd edges and a surface of shallow pores. Anemone corals, on the other hand, form encrustations that seldom reveal their solid foundations, for the polyps refuse to retreat, even when partially exposed to the air, from an unremitting drive to capture the sun and chase off would-be neighbours.
Similar-looking clusters of long columns topped by avaricious tentacles occur in the same region of surf. But these discs bear a mere octet of arms and emerge not from a hard skeleton but a base of fleshy tissue that occupies the rubble of dead sclereactinians. Feathery pinnules line the appendages which, unlike the random undulations of gonioporids, maintain a regular cycle of movement. The 'pumping' appears too feeble and unrefined to be feeding actions, however, and as the family is said to lack a functional digestive tract, it has been suggested that the motions help the xenids circulate fluid through their tissues. Where they flourish, the colonies envelope the substrate with dense swashes of pale caramel that welcome a daily dose of enlightenment and suffer the risks of relying solely on the sun for sustenance in a sea of growing turbidity.
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