The sea plunges low enough to expose the grassy core of Cyrene Reef for just a few hours each month, and usually during periods of serenity between a squandered day and a wasted night. For mere minutes, the reef's living corals, along with the grey remains of their long-dead kin, lift their skeletal heads to soak in the air of a city drenched in the sweat of distant labour. Hemispheres of round, raised and polygonal cups rise from the floodplain as the water drains over the blades, puddles in the gashes of boat strikes, and reveals, at the edge of the slope, a constellation of arms on fire. A few polyps, too, seem desirous of movement beyond their stations in life, stretching ahead of their cloned peers with their toes at the tip of the teeth of their tiny towers, a blob above the rest, a column of non-resistance to the pull of the earth and the touch of a hand.
Brown weed, green fronds, orange tunics and porous chambers bedeck many of the outcrops that dot the closely cropped seagrass bed. Hirsute crabs and light-footed carideans forage on these mounds, which hide in their subdermal layers a maze of channels and caverns occupied by brittle stars, bristleworms, snapping shrimp and stomatopods. Another inhabitant of these rubbly heaps, a likely latecomer to the intertidal scene, is a spider from a contentious family more often encountered in houses, logpiles and trees. The local representative of the group, which ranges from South Africa to New Zealand, is a brown-grey creature whose habits drew the attention of Victorian arachnologists familiar with just one other aquatic arachnid, the diving bell spider of European ponds and wetland guides.
R.I. Pocock, in a 1902 account of the genus, remarked that Desis martensi had been collected from "holes bored in the coral rock by a species of Lithophaga" at "Buran Darat Reef near Blacku Mati Island" about half a mile from land at half-tide. He noted with some bemusement the spider's marine disposition, quoting a colleague who declared, "[The spider] was collected by [Dr. von Martens] on coral-reefs at Singapore...... The species is remarkable in that it has established itself in these reefs, which are only temporarily uncovered by the sea..... That the species discovered by Dr. E. von Martens and Dr. Johswick can really, like our indigenous Argyroneta aquatica Cl., live under water, is to me doubtful in the highest degree, for it is wanting in the outward visible signs of the breathing apparatus which corresponds to such submarine mode of life, and which has been anatomically demonstrated in Argyroneta aquatica..... I opine that these spiders, perhaps in former times, were floated in an accidental manner from the land to these reefs and now live in the holes of the coral-bank, within which they withdraw at the time of flood, and which they close against the entrance of the water with a thick web."
T.G. Workman, another associate cited by Pocock, found the spider to be "perfectly helpless when placed in a bottle of water, showing in every way it was not in its natural element." These observations, along with affinities between Australia and African species, and the then-presupposed absence of the genus from South Asian coastlines, fuelled Pocock's hypothesis that the biogeography of the genus is a legacy of a vast tract of land connecting the southern continents, which allowed the littorally restricted animals to ford an Antipodean ocean. Geologically, the man was on the right track, though his prehistoric bridge was soon to be buried by the notion of continental drift, and later, the unearthing of biological, fossil and tectonic evidence for a fragmented former supercontinent.
Reef spiders certainly lack secondary adaptations for aquatic respiration, but the arachnids have survived and spread as far as the Galapagos, Japan, Brazil and Polynesia with little more than a knack for finding airtight retreats and an appetite that can withstand prolonged fasts. Snail shells, rocky cavities and tubeworm casings serve as submersible houses for the spiders, which line the walls and entrances of their shelters with silk to stay dry in the dark. During periods of serenity between spring tides, Desis probably does little more than breathe easy and live light, enjoying a level of existence few higher beasts can tolerate and which could seal its fate should the seas rise up against those who burn their past and blow their future before the spiders can reach new footholds. Come low water, the hunters emerge to chase down small arthropods and court mates, if non-consensual grappling and insemination of females by the rather more robust males count as affair. Finesse could have been the casualty of lives constrained by maritime schedules in which only the boldest and biggest of suitors are able to pin down their partners before the reef sinks and strands the spiders on the surface of the sea, victims of an ill-spun palp romance.
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