The sand stirs with life even when the spring tide drains the bars of Cyrene Reef on a dawn fuelled by frail winds and flavoured salts. There is always the danger that rubber soles, stumbling from dinghy to damp bank, might meet spiny ends or crush the life out of soft creatures in brittle exoskeletons. Sea stars, sand dollars and the snails who hunt them in the dark occupy the shifting towers of a mound that at times probes deep into the seagrass meadow, cleaving the flat into a field of raised puddles.
Nearly every patch of bare grains between the seagrass is apt to harbour a menagerie of shells, soft bodies and squirming forms with little love for the shadows of low waters. For these magical hours also beckon terns, egrets and herons who seem to know the moon and its moments of opportunity. In the mid-year months, families of little terns arrive to dive after trapped fish, their recently fledged members in tow and testy at having to fend for themselves after a spell on drier dunes. On the fringes of the reef stalk reef egrets, white or slate-grey specialists of Indo-Pacific coasts who must vie with the region's human population for the fruit of the tropical sea.
Many fish unfortunate enough to enter submerged traps of steel wire laid by itinerant sampan men avail themselves to neither bird nor man. For soon after, or even long before their final spasms, their bodies would be nibbled at, ripped apart and shredded by the claws of a clean-up crew with a nose for trouble and the dexterity to reach through the mesh for (still) fresh pickings. Thalamita and Charybdis, two genera of portunid crabs, are among this gang of underwatertakers who'd scarcely refuse a break from their bland regime of corticated filaments.
The swimmers are not the only ones who feed off others' misfortunes. Moon crabs share the habitats and appetites of the portunids but lack the will, if not the wherewhital, to stage a feint with brandished arms before paddling off to safer grounds. They appear to realise that their comparative advantage lies in 'flee' not 'fight, and make full use of all eight flippers (the portunids have only two) to propel their roughly rounded carapaces away from scenes of questionable content. After this aquatic sprint, the crabs plough themselves into fine silt until little more than a pair of short-stalked eyes remain on the sand line.
Three species of matutids have been recorded locally. The two most commonly encountered ones have pale bodies with black spots and are reliably distinguished by the angle of a ridge on the outer side of their palm, which is parallel to the ventral margin in Ashtoret and oblique in Matuta. Like portunids, these genera borrow their names from Mediterranean deities and exhibit a certain convergence in two lateral spines that probably make them just a little harder to swallow. The third species, the strikingly patterned Matuta planipes, is a little less frequently seen, which may be the result of relative scarcity or a preference for deeper shoals. But all three favour sandy bottoms in the vicinity of seagrass beds, which provide in turn refuges and repositories of nourishment.
Matutids were once regarded as a subset of Calappidae, but these ties have been severed by carcinologists who saw enough apomorphies to raise the rank of moon crabs to a clade of their own. Though similarly fossorial, box crabs possess tapered ambulatory legs that are hidden under a broadly ovate or clypeiform carapace. The deep body, an aid to respiration when the animal is buried, is protected by an anterior shield of two robust chelae: one with a 'can-opener' tooth built for cutting and penetrating and the other with daintier fingers for gripping and picking. Gastropods with stubborn opercula or narrow apertures are the primary victims of this toolkit, but hermit crabs in secondhand shells also fall prey to calappids with a taste for anomura.
Like their erstwhile kin which dig into sand rather than snails, calappids have three local representatives. But the crabs' favoured substrate of littoral seabeds within reach of productive reefs, a habitat dismissed by both coastal planners and coral rescuers, has rendered them vulnerable to local extirpation. Their food items, likewise, have suffered from the ravages of floating dredgers as well as developers who crave the tranquility of an equatorial seafront. There is too much at stake, it seems, and too little time, after the labours of a life of leisure, to lose face and succumb to the shame of boxing in a pod of bottles and betting the future on present grains.
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