Black sea cucumbers lurk under almost every other rock at Pulau Tekukor, unbothered and uninhibited by a sea of polyps that cloak much of the northern shore with short columns and striking crowns. The holothurians paid no heed to sun or tide, probing from fading shadows or passing the time in shrinking pools and rising terraces. Those that chose unwisely must endure a few hours of mid-morning discomfort, but individuals that languish in schleppy hollows continue their routine of slow sweeps of their perimeters, using their fore ends as blunt hoovers armed with protrusible brushlets that swipe the silt and stuff food and filth alike into their mouths.
Reaching up to nearly two feet in length, Holothuria leucospilota is one of the larger local representatives of its class. The animals are absent from sand, scarce on seagrass beds and dense reefs but surprisingly abundant on sites with suitable anchorage in the form of large rocks and eroded ridges with areas of loose sediment in between. Tanjong Rimau off Sentosa's northwestern tip, Labrador Park, St John's Island, Pulau Jong, the northern rim of Cyrene Reef and Pulau Tekukor's broad flats are their strongholds in the southern straits, where they share dim niches with shy crabs, small gobies as well as light-footed shrimp that find rich pickings in the cucumber's feeding motions. The presence of Cuvierian tubules, which are quite readily extruded when collectors remove the animals from their retreats, probably deters piscine and portunid hunters, but fully grown individuals appear to face few threats other than overheated basins and coastal apocalypse. Populations in deeper waters are said to reproduce sexually, but intertidal colonies are reported to rely more on transverse fission to sustain their numbers, a preference that may boost their strength in amenable shores but hinder recruitment at fresh habitats.
Pulau Tekukor is also home to other sea cucumbers, but finding these echinoderms requires rather more effort. Rocks must be rolled over, rubble dislodged, hands scraped and eyes strained to expose a hidden community of sponges, bryozoans, ascidians and other, nameless, blobs, that thrive on a diet of currency, as well as the creatures that roam this underbelly of pores, tubes and tunics: porcelain crabs, cowries, brittle stars and worms, segmented and stranger still, which greet the light by racing for deeper cracks or writhing in place, mantles undone, arms in disarray and chaetae bristling with defensive suppositions.
The holothurians that haunt these submarine cliffs tend to be smaller than those that sift the sand or wedge themselves into reefs. Two were discovered during the Mega Marine Survey of Singapore's foray onto Pulau Tekukor one bright blue morning in June. One was dark with a purple shine, resembling a cucumariid known from northern flats. But few other clues to its identity were available in situ, for the specimen ceased all activity after it was found, refusing to extend its tentacles and barely maintaining a grip on the gravel as the tide swung back and battered a plain of ancient feuds.
The other find, a pale thing with numerous papillae and patches of darker pigments on its dorsal surface, is probably from a different family, as its tentacles, which emerged soon after it had secured a foothold on a handy rock, resemble those of Holothuria rather than the sticky trees of life that sprout from suspension-feeding groups. The animal was loathe to interrupt its brunch for existential struggles; palmate tips reached out to grab portions of deposit for intraoral processing a moment after it was placed on a boulder to be compared and contrasted with its fellow specimen. Only later, when relaxed in clove oil, with their anterior tubes outstretched and ambulatory ridges exposed, and their dermal ossicles are separated by a bath of bleach, will these holothurians permit inquiries of greater resolution than that possible during an hour or two in the field, where taxonomy is hampered by crude tools, tidal constraints and calculations that force one to choose between focused sampling and broad sweeps of a slope prone to sliding under the waves and slipping the minds of neighbours on richer banks.
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