Wham bam thank you ma'am
'Twas crabby sex we had, at
St John's on the rocks.
There is a tendency for certain taxa to ditch a freewheeling existence for fixed habits. Barnacles, sea squirts, worm snails and tube worms have secondarily abandoned legwork to pursue a life of attachment, though their ontogeny betrays their affinities with motile kin. On land, there are fewer opportunities to stay put, for want of convenient nutrient streams, but one group of true bugs, the coccoids or scale insects, exhibit varying degrees of sessility in adulthood, having made the most of the specialised feeding apparatus of their order, which permits the stationary imbibing of plant sap from subcuticular vessels.
Male coccoids, which bear just one pair of wings and lack mouthparts, are recognisably insectan, but the females look nothing like their mates, or other members of their subphylum, for that matter. Mealybugs of both sexes, which cover themselves with sticky filaments and commonly infest houseplants and cash crops, retain the ability to stealthily creep up soft shoots. But the females of their cousins, the coccids, lose nearly all traces of segmentation at maturity, appearing as little more than lumpen tests that line midribs and scar the tender extremities of their victims. Turn them over and it is just possible to make out six minuscule limbs and piercing stylets on the ventral side of a waxy shell.
By the planks that run alongside Berlayar Creek, there are regular strands of Avicennia officinalis, which can be distinguished from the more common A. alba by its ovoid leaves and markedly larger flowers. As is typical of the genus, the buttery blooms emit a sickly sweet scent when sniffed. Many of the thinner branches and petioles of these trees harbour ample clusters of scale insects. A sooty coat stained parts of the foliage, the likely result of a mould that flourishes on the excess honeydew extruded by the coccids. The 'colonies' consist of individuals of varying sizes and are probably a species of Ceroplastes (perhaps rubens, which has been observed on all local species of Avicennia).
A destructive curiosity led me to dislodge a large specimen from a dense clump of tests. But instead of the expected base of a degenerate hexapod, the scale revealed in its hollow a larva that responded to its discovery with vigorous wriggles of its torso. The larva made no attempt to abandon its shelter, and produced copious strands of silk when placed on a fresh substrate (a useful impulse on a home subject to tidal shifts). In habit, the creature recalled the young of lacewings that don a coat of debris, but it lacked the nippy mandibles and predatory aspect of juvenile neuropterans, bearing instead a modest, strongly pigmented head and stout legs on fleshy segments. Once it had settled on a spot, the larva displayed no inclination to budge. It is likely that the insect, whatever its mature guise may be, is nocturnal, setting forth only after hours to forage under the cover of darkness and a handy suit of waxy armour procured by means no fair or nominally foul.
Serendipity often strikes in the final moments of our surveys of Singapore's surviving patch reefs. Having secured the unwitting and unwilling broodstock for a new generation of giant clams shortly before daybreak, there was ample time to explore the fringes of Terumbu Pempang Tengah for a glimpse of the apolyphal colonies that built this platform and still hem its slopes. Brahminy kites and pacific reef egrets were other early birds, rising long before the sun to circle the reef and plunge at fish in shallow pools.
The gap between night and light appears to catch many nocturnal animals by surprise; morays, worm-eels, carpet eel-blennies and other serpetine fishes probed the rubble for hidden prey and octopuses continued to hunt, their skin exhibiting deep hues of excitement as they hugged the apertures of promising crevices and unfurled their tentacles to snare small shelly fauna, even as the sky turned from a burnt-out black to a bloody blue and gave hazy form to columns of smoke that rose from a nearby refinery and merged in mid-air into a cloud of dire shades.
Given their dexterity and the strength of their arm suckers, octopuses make short work of clams and other bivalves that lack the means to resist a fatal pull. One mollusc that managed to elude its cephalopod kin but not hungrier eyes was a finger-size thing with elongated shells from which a wrinkly tube protruded. Spotted near the edge of the crest on coarse silt, the animal brought to mind a far larger cousin from cooler shores, which has found occasional favour among local gourmands. Hiatellids are absent from these waters, however, much as it would amuse some to unearth the rude end of a tropical geoduck.
One authority has suggested that the creature is among the 17 or so surf or trough clam species recorded in Singapore. Mactridae is a family of robust, burrowing bivalves with representatives worldwide, including two genera with members known as duck clams. But the proposed genus, Lutraria, lacks the squarish hind end of this specimen and a cursory trawl through at least four published references suggests that the clam is more likely a laternulid.
Also known as lantern clams, these shellfish have delicate, elongated valves that are pearly and incapable of opening fully. Four species occur locally, living in soft deposits on shallow flats where they filter feed, with their mud-strewn siphons inhaling from the water column. Young animals can burrow vigorously, but when dug out, the larger adults of one species were reported to exhibit no flight responses and proved inept at digging themselves out of their mess. Neither was the siphon, which is said to have tactile, photosensitive feelers, withdrawn from the posterior gape.
True to stereotype, our hapless individual, dislodged perhaps by some fossorial predator and unable or unwilling to save itself, languished by the surf until it was earmarked for immortality. This genus, too, has aroused anatine desires in the minds of demented malacologists, but the shape of our discombobulated clam does not quite match the 'beaky' profile of Laternula anatina. Two other species, L. truncata and L. spengleri, are the likelier candidates for the labelling of this ducky discovery on the shores of a reef in the middle of a well-dredged straits and on the furtive margins of a massive mega marine make-out.
The sandwiched child of a trio of small patch reefs due west of Pulau Hantu and the smokestacks of Bukom, Terumbu Pempang Tengah is separated from its landward sibling by a channel rife with wrecks. The reef sits atop a crest of rubble that gives way to a broken basin of soft and stony corals along the northern fringe, while the eastern slope is relatively sparse and pierced through the knee by a tongue of sand. Low, branched colonies of Montipora form a grey plain near the centre of the flat, which is otherwise dotted by puddles of crabs and isolated outcrops.
The coralline rock, over which polyps once grew, now serves as a foothold for more primitive animals: sponges in the guise of thick chalices, awkward branches, hispid globes and layers of porous tissue that encrust the surface with a solid splash of primary colours. Within these glass chambers and siliceous channels dwell brittle stars, sea cucumbers and snapping shrimp that sip and sup from streams of water powered by inner walls of flagella, organelles in a state of perpetual flux and whose bearers offer a glimpse at how free-swimming cells might have traded their independence for collective benefits. Modern poriferans continue to thrive in marine and a few freshwater habitats, and hold their own in a fitness landscape of more advanced metazoans. Few predators, too, have the stomach for spicules, save sea turtles and pomacanthids. A good number of dorid nudibranchs also specialise on sponges, using extra-oral secretions to dissolve their prey in-situ into a proteinous soup, which is imbibed along with defensive metabolites that line the spawn and skin of the slugs. It probably pays as well to declare the presence of noxious goods before a fatal bite and nudibranchs such as Glossodoris atromarginata refuse to be wallflowers, creeping over the reef with folds that leave little to the imagination and gills in a whorl of their own.
The bloated coenosarcs of soft corals, resembling ruffled omelettes, lobed discs or leathery folds, pepper parts of the flat that receive ample servings of planktonic currents. Stranded colonies collapsed into untidy flaps or limp digits, but some portions, trapped in shallow water, still throbbed with a profusion of autozooids, minute polyps with eight pinnate tentacles and the wisp of a column, that hide the firm but flexible matrix under a bed of feeding bodies. Also present, but in smaller numbers, were nephtheids in the shape of weedy shrubs lined with pale-stemmed florets, by which hovered tiny filefish in similar shades but nervous garb.
Growing alongside the octocorallians are the true reef builders, the scleractinians who capture fluid ions to carve shells of aragonite that rise over time as each polyp lays down fresh ridges to create room for itself, buds off to form a new branch or simply expands to occupy a greater share of the seafloor. Beneath this living veneer of tentacles and inflatable tissue is a base of columns and dividing walls that support the colonies as they grow in girth, height and complexity. The reef, for all its rigid layers and tiny towers, is a trove of ecological niches whose inhabitants survive by mastering its rhythms and making alliances that maintain a balance of power between those who feed among the corals and those who feed on them.
The hub of the flat is a field of porous boulders and branching corals in the genus Montipora; the latter, with their grey stems and bare tips, resemble a garden of brittle lichen kept low by the dry mow of spring tides. In slightly deeper parts, the plate-like base of another acroporid supports an unruly array of stout branches that terminate in broad, blunt fingers traced by vein-like ridges, between which sprout masses of tiny, brown polyps. Meandering ridges also characterise Pachyseris rugosa, but the corallites of this species are part of the superstructure, with finely toothed columellae that serve as partitions between lines of barely discernible polyps. Dull green with white trimmings, the colonies are somewhat plastic in expression but here, they grow as thick forts that assault the surrounding rubble with new walls of territory.
Turbinaria may also form plates that creep over the substrate, but the typical members of this genus build raised discs with often ruffled edges, which in some colonies develop into arborescent complexes with broad tiers and overlapping canopies. The largish polyps are widely spaced and emerge from a common anchorage, which cloaks the corallites and envelops the colony in a skin of gaudy colours. These assemblies of warm browns, blues and greens stand in contrast with the pinks and purples of Goniopora, whose exuberant polyps stretch out from a submassive skeleton to swirl with the tide and swing to the waves. The hemispherical colonies appear impossibly dense and individual columns probably undergo some degree of deflation before they can retract into their shelters. A few, however, produce modest polyps from boulder-like or encrusting colonies that recall their poritid cousins.
A motley assortment of other hard corals shatter the contours of the reef with angular bulges and irregular masses. Some colonies are little more than a dozen strong and face an uphill struggle to outpace their neighbours and engulf the surrounding rock. Others have gained purchase on favourable spots and use this headstart to nurse a convex battery of soldiers who launch sting operations on nearby settlers. But for all its belligerence, Galaxea remains a brittle star on a stage where armoured mounds, clad in dense cones, stiff honeycombs or a maze of solid brain waves, have the upper hand in withstanding the depredations of polyp-phagous animals and the battering of tropical storms.
There are also corals that refuse attachment in adulthood, severing ties with their juvenile stalks to rest on the seabed in apparently random aggregations. It's not entirely clear if the individuals get around on their own accord or ride convenient surges, but fungids are certainly able to shake off the threat of burial under loose sand and avoid the pains of coralline scrums. The compact, parasol-like species seem to prefer siltier lagoons, but Terumbu Pempang Tengah, located as it is by the slipstream of a dire straits, is dominated by elongated fungids that bristle with septal rays and fleshy bits.
Structurally similar to scleractinians but lacking hard parts, corallimorphs inhabit somewhat sheltered nooks of the reef, where they may obscure the rubble with a layer of coelenterate rugs. Each cluster usually consists of individuals of varying size, the likely result of fissile offshoots from a lone pioneer. Conventional wisdom suggests that the order subsists on the byproducts of inhouse zooxanthellae, but the animals, which are known to snare fish and sweep their borders for would-be trespassers, probably harbour a reservoir of survivalist tricks within their broad oral discs, which house sparse, or non-existent, rings of stubby tentacles.
We try our best to sidestep these biotic elements of the reef flat as we scour the scene for tridacnids and other tantalising members of the intertidal community, for these ephemeral playgrounds, little touched and hardly trampled, are wont to attract creatures that shy away from the fringes of walled islands and have long skirted mainland shores. Patches of sand between the growing outcrops pose a modicum of risk, but the stingrays that invade the shallows to root out shellfish seldom allow themselves to be cornered and maintain a wide berth from clumsy waders.
The main victims, as it were, of rubbery treads were zoanthids, whose seemingly discrete polyps are joined at the foot by invisible mats that permeate unconsolidated sediments. From these stolons rise short columns topped by tentacular rings of green or brown, which double over when disturbed to become limp blobs of coenosarc. This cnidarian horde, overlooked on account of its near ubiquity and tendency to overrun every tract of exposed silt, endures and probably shrugs off the subconscious brunt of visitors who favour the more fragile architects of the reef and plot against time and tide to restore, or at least record, a fraction of the life aquatic that once coursed these waters and fed the forefathers of this maritime city.
Out of water, and just out of reach. A yellow-spotted mudskipper stopped us in our tracks as it sat on the arch of a Rhizophora root by the boardwalk of Sungei Buloh Wetland Reserve, awaiting the departure of the sea and the chance to descend onto the silt to forage and defend choice cavities on the mangrove flat. Once thought to be juveniles of a larger fish, these medium-sized gobies are now regarded as a species in their own right, and add a new measure of intrigue to the intertidal circuit.
More at home in the air than the de-aerated waters of sheltered coasts, these oxudercines have a sturdy fin each in two respiratory boats: their gills share gas exchange duties with pharyngeal chambers and vascularised cuticles that fuel the fish and flush waste with amphibious efficiency. Primitive they may be compared to the labyrinths of gouramis and bettas, the ambient adaptations of mudskippers allow the gobies to leap, crawl and tail-vault through the swamp with enough speed to snap up flies and sidestep most terrestrial hunters. Life in the dry zone also frees the fish from aquatic predators, though it's debatable whether a plague of mosquitoes is preferable to the scourge of marine leeches. Still, the bloodsucker that sat on the face of this ragged individual was endured with little fuss, and the goby showed no sign of discomfort with both the minute pest as well as its moment of fame. Trapped between sea and soil in a region of high physiological stress, the mudskipper and most of its subfamily have learnt to handle a wide range of enviromental pressures without losing heart at their status as latecomers on a stage long occupied by rivals with legs.