Threads from the Web of Life: Stories in Natural History

The Neon Flying Squid Vanish

11 The Neon Flying Squid Vanish THE first stars come out early over the Tasman Sea, with the last vestiges of sunset still pooled on the rim of the western horizon. No landforms rise in low silhouette behind that sharp skyline, no land-borne dusts and hazes dim these skies. So as the low swells flatten to a glassy mirror, the constellations are soon reflected in undiminished brilliance. And the light show is only just beginning. Even after darkness takes full effect, the points of starlight on the water continue to multiply, joined by points of cold fire rising from below. A powerful current wells up here, a surge deflected from the canyons and seamounts hidden in the darkness far beneath sea level. The trace minerals carried to the surface feed a flourishing population of microscopic dinoflagellate algae by day, and a menagerie of creatures large and small arises to prey upon them—and upon each other—by night. At high noon, daylight penetrates more than two hundred feet down through these waters. But as the afternoon wears on, the darkness reclaims the depths, moving up from underneath on pace to reach the shallows by dusk. The denizens of the deep have been rising with it, each in search of smaller prey. With the dominant visual hunters blinded by the darkness, the smaller predators gravitate to the upper layers where the algal plankton anchor the food chain. These rising opportunists include small fish in large schools— pilchards, lanternfish, larval fish of many types—and shoals of shrimp, copepods, and other animals smaller still, shaped by an environment alien to the world of light, with outsized eyes and translucent bodies. Many of them are bioluminescent; bioluminescence is the only light they ever see. They come from a 12 Threads from the Web of Life world of such crushing pressure that they would explode from their own internalized, counterbalancing pressures if transferred suddenly to the surface. But the transfer is not sudden. They have been rising at their own speed, equalizing their pressure for hours, following their age-old diurnal cycle. Despite their size, the microscopic creatures at the base of this food chain are not merely defenseless bait. When the surface -dwelling algae are disturbed, they create light—light in the middle of the night—and by so doing, these tiny firefly plankton expose their own predators. The phosphorescent algae emit an astonishing amount of light for their size. Even though they are too small to be seen by day, the light from an agitated individual is obvious in the dark, a floating electric-blue spark. These dinoflagellates brighten at the slightest pressure, most often from the turbulence of a passing wave. So when a great finback whale moves through the area, her spout billows into a brilliant geyser; its twinkling mist lingers in the air, and her dorsal fin spreads a luminous V across the surface in her wake. When a small shrimp seizes a phosphorescent alga, the attacker finds himself brightly lit. Even as the devoured alga is dying , even when it is ingested, its fading light shines out through the transparent body of the predator, advertising his position to his own enemies with a beacon from within. The last contribution of an algal victim may be to take one attacker with it, a sacrifice for the benefit of the greater algal community. The bane of the algal light is not limited to the smallest predators but extends on up the food chain. When the next-bigger fish shoulders the water out of the way while striking the self-lit crustacean, all the phosphorescent algae disturbed in its passing light up, spotlighting the fish itself. If it dashes away, startled by the light, the shoal of algae glows brighter the more vigorously it is pushed aside. The fish leaves a phosphorescent wake, a summons guiding the next bigger predator in the chain, a faster, sleeker fish, which will, through its own movement through the water, also have lost the concealment of darkness. THIS strange environment of glimmering patches of struggle has molded one creature to take maximal advantage of the resources there, while minimizing the risks. It is an animal sleek 14 Threads from the Web of Life and flattened on its leading edge, with tentacles trailing behind. It fills its hollow mantle with water and then squirts the water out through a steerable tube, moving itself...