DTherifters... Main Story by CABELL DAVIES PHD Photography by RUSS HOpcrOFT PHD There are more animals in the sea than on land…many times more. The dominant forces behind all life on earth are the tiny, minute beings that drift across the vast expanse of the ocean. EUCHAETA MARINA is a common shallow-water predatory copepod in he term “Plankton”, for VALDVIELLIA INSIGNIS is a deep-sea tropical waters. This female carries a microscopic, infinitesimal predatory copepod. It attacks prey with clutch of several dozen bright blue eggs. animals, first coined in 1887 by Victor Henson at the “Edward scissor-hands” like mouthparts Size 3-4 mm. University of Kiel, Germany, which are visible in this image. Her is derived from the Greek two large purple eggs are also visible. word “planktos,” meaning “drifter”. Most offspring of Size 11mm. marine animals in larvae form do not resemble their parents such as tarpon, bonefish, and eels. However there are some that are simply miniatures Most offspring of marine animals in larvae form do not resemble their parents such as tarpon, bonefish, and eels. However there are some that are simply miniatures of their parents like the octopus, squids and anemone. of their parents like the octopus, squids and anemone. Plankton has evolved an (Front page) ATLANTA PERONI is a extremely diverse range of body shapes and sizes in their attempt to adapt to heteropod, one of the pelagic snails. It the pelagic marine environment. Often swims by rowing the 2 lobes of its foot, wildly elaborated body forms of plankton while using its well-developed eyes to are reminiscent of creatures from George Lucas‘s Star Wars series. George must have search for other pelagic snails on which been deeply inspired by the ocean. it feeds. Size 1cm. 24 The DRIFteRS... OCEAN GEOGRAPHIC 5:3/2008 25 While the many familiar marine animals Copepods have evolved to be the fastest have larval stages, these species are not the animals on earth relative to body size. dominant members of the zooplankton. Using a high-speed video microscope, In fact, the vast majority of zooplankton copepods have been clocked at 500 body spend their entire lives as holoplankton lengths per second. By comparison, an and they are unfamiliar to the average folk. F-16 fighter jet flies at best 50 body lengths Important groups of holoplankton, are per second. In that perspective, the cheetah the copepods that are the most numerous cannot be the fastest animal on earth! If a animals on earth1, yet most of us have no copepod is transformed in ratio to the size The AMphipod PHRONEMA has clue of their existence. Copepods are small of a cheetah, in comparison, the cheetah Copepods thrive in crustaceans ranging in size as adults from would run at 70 miles per hour (112 hollowed out a zooplankter called a salp the world’s ocean about ½ mm up to 10 mm ( see picture km/h) at its top speed, and the copepod into which she will lay her eggs. She will and freshwater of Valdvielia and Euchaeta). Copepods would zoom past at 2,000 miles per hour then swim this living nursery around thrive in the world’s ocean and freshwater (3219 km/h) through water which is 800 environments, with environments, with an estimated global times denser than air. This mesmerizing until her babies are large enough to leave an estimated global population of one quintillion (1018). That’s feat is achieved by the copepods when home. Size up to 3 cm population of one a half-billion copepods for every person they transform their bodies from a typical 18 on earth! “T” feeding posture, with their antennules quintillion (10 ). spread wide (as illustrated in picture of That’s a half-billion Copepods are a primary sustenance for Valdvielia and Euchaeta), into a torpedo many larger plankton, adult fish, and shape with the antennules laying alongside copepods for every whales. As they are near the bottom of the the body while the swimming legs propel person on earth! food chain, evading predators is a necessity. the animal forward with blinding speed. 1 with the possible exception of roundworms The AMphipod MIMONECTES SPHAERICUS (formerly necto amphipod) is a commensal on deep-sea jellyfish and their kin. The large knife-like antennae indicate this is a male. Size 3 mm. Basin ciRCULation: It reflects the connection between the surface and deep water flow, in the global Ocean-conveyer belt that takes between 600 and 1600 years to complete. 26 The DRIFteRS... OCEAN GEOGRAPHIC 5:3/2008 27 PeLAGOBIA LONGICIRRATA is a pelagic Polychaete worm, from the deep Arctic Ocean; the orange color comes from oil drops stored in the body. Size 5 mm. This GReen poLYchaete WORM has left the seafloor to lay her clutch of pink eggs in the plankton. Size 4-5 mm. ALACIA VALDIVIAE is a deep- water Ostracod or clam- shrimp, a small crustacean protected by two clam-like shells. They are important scavengers in the deep-sea. Size 4-5 mm. 28 The DRIFteRS... OCEAN GEOGRAPHIC 5:3/2008 29 The sea-angeL CLIONE LIMACINA is a predatory pteropod, another shell-less pelagic snail that flies through the water with it’s tow wings, hunting for other snails to eat. Size up to 3 cm. There are many other groups of holoplankton with equally fascinating life histories and behaviors. An example includes the amphipods (Phronema and Necto amphipod), which are voracious predators of copepods. The amphipod Phronema with large compound eyes and scythe-like appendages is actually a crustacean that breeds it young inside a salp, CARINARIA LEMARCKI is another The amphipod Phronema with large species of heteropod (pelagic compound eyes and scythe-like snail), but unlike Atlanta it is no appendages is actually a crustacean longer able to fit inside its shell. that breeds it young inside a salp, The end of the snout is equipped a jelly like animal. with strong hook-like teeth used or extracts other snails from a jelly like animal. It t has to kill the salp their shells. Size 3-4 cm. first, and then move in and use its jellish body as nest to breed. Another interesting crustacean group is the Ostracods (Alacia valdiviae) which are active swimmers and have a clam-like shell for protection. Many of the deep-dwelling zooplankton, like that of Ostracods are red, which make them nearly invisible at depth as the red is readily absorbed by seawater. By contrast, species that live near the surface in tropical regions are often blue, matching the colour of the ocean’s surface. Marine worms called Polychaetes, (Green Ploy, Pelagobia longicirrata), equipped with rows of swimming appendages for rapid movement are also the copepods’ predators. 30 The DRIFteRS... OCEAN GEOGRAPHIC 5:3/2008 31 The sheLLed pteRopod DIACRIA TRISPINOSA feeds by secreting a bubble of mucus from its large fleshy wings. As it sinks from the weight of the shell, food gets stuck to the bubble, then both the bubble and the attached food are eaten. It then uses the wings to swim back to shallower water and start the process over again. Size up to 2 cm. The Pteropods are marine snails that have adapted to life in the ocean by using a “foot” to swim swiftly through the water column. Some pteropods have little or no shell and they are slug-like predators (Carinaria and Clione) of the shelled Pteropods (Limacina, Janthina, Diacria, and Atlanta). The pelagic nudibranch, Phylliroe atlantica, has a larval stage that burrows into a jellyfish, eats it from the inside out, and becomes a free-living adult. Larger plankton includes various kinds of shrimp, which feed on Phytoplankton (plants plankton) as well as on smaller zoo- plankton such as the Eusirus. Jellyfish, which can grow up be up to a meter in The pelagic nudibranch, Phylliroe JANTHINA UMBILICATA is a snail that atlantica, has a larval stage that lives in a unique habit within the ocean burrows into a jellyfish, eats it from called the neuston. It secretes a mat of the inside out, and becomes a free- sticky bubbles that keep it attached to living adult. the ocean’s surface, where it hunts for jellyfish that live in the same special diameter are considered planktonic since habitat. Size 6-7 mm. LIMACINA HELICINA is a shelled pelagic snail they drift with ocean currents, and there is a wide variety of these important predatory common in temperate through polar waters. species. Siphonophores (see picture of They are sometimes observed to gather Abyla duck siph and Hippodius) are colonial together into swarms. Size up to 1 cm. animals, related to jellyfish that include the deadly Portuguese Man of War (Physalia utriculus) commonly known as the blue bottles in Australia. 32 The DRIFteRS... OCEAN GEOGRAPHIC 5:3/2008 33 The diversity of zooplankton is enormous, comprising of species from all animal phylum. Zooplankton includes most of the nearly half-million non-insect animal The peLagic snaiL PHYLLIROE species on earth. In addition to its diversity, ATLANTICA begins life as a parasite the shear mass of zooplankton in the within jellyfish, but as it grows, it ocean is of colossal proportions; if all the zooplanktons were sieved from the sea becomes a predator on them. It and spread across the USA, Australia and swims using its flattened tail. Size up China, the resulting layer would be meters to 4 cm. deep and the vast majority will be copepods. These ocean drifters impact not only upon the yield of global fisheries but more importantly the global carbon and nitrogen cycles.