Holozooplankton are animals that live adrift in the ocean waves for their entire lives. The researchers who took part in the Census of Marine Zooplankton, a project of the Census of Marine Life, spent a decade surveying and photographing holozooplankton biodiversity around the world. Here is a sampling of what they found.
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Zooplankton Biodiversity
Transparent Sea Cucumber
Credit: Laurence Madin, Woods Hole Oceanographic Institution/CMarZ, Census of Marine LifeCensus of Marine Life researchers discovered this unusual transparent sea cucumber (Enypniastes sp.) in the Gulf of Mexico at 2,750 meters depth. It creeps forward on its tentacles pretty slowly, at around 2 centimeters per minute, while sweeping detritus-rich sediment into its mouth. It's so transparent that you can even see its digestive tract winding through its body! See more cool zooplankton discovered by the Census of Marine Life, or learn more about the deep sea.
Deep Sea Copepod
Credit: R. Hopcroft, University of Alaska - Fairbanks (www.cmarz.org)This copepod (Gaussia princeps) was collected deeper than 1000 meters in the Sargasso Sea by Census of Marine Zooplankton (CMarZ) researchers in April 2006, as part of the 10-year Census of Marine Life. However, specimens of this species have been collected in all the world's oceans at many depths: in the Caribbean, it has been found at depths as shallow as 25-50 meters!
G. princeps is a bioluminescent species, with both males and females producing blue light. Its light is bright enough that molecular biologists use the bioluminescent pigment as dye in the lab to help them visualize their experiments.
Reference: Suarez-Moralez, E. 2007. The mesopelagic copepod Gaussia princeps (Scott) (Calanoida: Metridinidae) from the Western Caribbean with notes on integumental pore patterns. Zootaxa 1621: 33–44. (PDF)
See more photos of cool zooplankton collected by the researchers in this zooplankton biodiversity slideshow.
The Squidworm - A New Species
Credit: L. Madin, Woods Hole Oceanographic Inst. (WHOI) (www.cmarz.org)In the Coral Triangle, a biodiverse area between Indonesia and the Philippines, scientists discovered this swimming polychaete (bristly worm), which they have dubbed the "squidworm." Using a remotely operated vehicle, the researchers with the Census of Marine Zooplankton (CMarZ), a project of the Census of Marine Life, dove 1.8 miles (2,800 meters) to first discover Teuthidodrilus samae in 2007. The squidworm is named such because of its 10 tentacle-like appendages on its head, which are each longer than its whole body. It uses these to collect particles and detritus falling through the water, often called "marine snow," for food. See more photos of cool zooplankton collected by the researchers in this zooplankton biodiversity slideshow.
Jellyfish, or Siphonophore Colony?
Credit: L. Madin, Woods Hole Oceanographic Institution (www.cmarz.org)This colony of Rosacea may look like a single jellyfish, but it is actually a large group of smaller siphonophores clustered and living together. In fact, the zooids (individual siphonophores living in the colony) cannot survive on their own. This specimen was photographed by the Census of Marine Zooplankton, a project of the Census of Marine Life, in the Sargasso Sea in April 2006.
A Rosacea colony's long tentacles extend a meter away from the main body and contract when disturbed by potential food items. The bead-like dots are stinging cells (nematocysts) that immobilize and kill their prey.
See more photos of cool zooplankton collected by the researchers in this zooplankton biodiversity slideshow, and learn more about jellyfish, comb jellies and other gelatinous ocean animals.
A Ctenophore Feeds
Credit: L. Madin, Woods Hole Oceanographic Inst. (WHOI) (www.cmarz.org)The comb jelly (ctenophore) Thalassocalyce inconstans is found in shallow to deep water in the Atlantic Ocean, Mediterranean Sea, and sometimes in warmer Pacific Ocean waters off the coast of California -- although this one was photographed in the Sargasso Sea by Census of Marine Zooplankton researchers.
T. inconstans has a very different feeding behavior than other ctenophores. Most ctenophores use muscles to suck in large volumes of water to capture prey. But T. inconstans has little muscle; instead, it waits until a euphausiid (small crustacean) or copepod accidentally swims inside its bell, where it sticks to the mucus-covered inner surface. Then the ctenophore closes its bell shut very fast -- in less than half of a second!
See more photos of cool zooplankton collected by the researchers in this zooplankton biodiversity slideshow.
Reference: Swift, HF, Hamner, WM, Robison, BH, Madin, LP. 2009. Feeding behavior of the ctenophore Thalassocalyce inconstans: revision of anatomy of the order Thalassocalycida. Marine Biology 156, 1049-1056. (PDF)
Close-up View of Salps
Credit: L. Madin, Woods Hole Oceanographic Inst. (WHOI) (www.cmarz.org)This close-up view of salps, which have aggregated together into a long chain, have brilliant red guts from eating red plankton. They were observed by researchers with the Census of Marine Zooplankton in the Sargasso Sea.
Salps are sac-like, tubular organisms that spend part of their life as individual oozoids (a single, short tube with one red gut), reproducing asexually, and then link up in the aggregate phase, forming long chains. Once attached, the chain of individual oozoids swims and feeds together, and if they run into another chain, will reproduce sexually.
See more photos of cool zooplankton collected by the researchers in this zooplankton biodiversity slideshow.
A Swimming Snail
Credit: R. Hopcroft, University of Alaska - Fairbanks (UAF) (www.cmarz.org)Sea butterflies (also called pteropods) are sea snails aptly named: they are shelled marine snails, each with a foot like a wing, that swim in the water column like butterflies. This one, Atlanta peronii, is very small: the biggest specimen on record was less than half an inch (11 millimeters) long! They are completely transparent, so you can see all their organs, and have shiny black eyes.
This A. peronii was observed in the Sargasso Sea by the Census of Marine Zooplankton.
See more photos of cool zooplankton collected by the researchers in this zooplankton biodiversity slideshow.
Amphipod: Salp Invader
Credit: R. Hopcroft, University of Alaska - Fairbanks (UAF) (www.cmarz.org)Can you spot the amphipod (Phronima atlantica) in the below photo? She's the transparent lobster-looking animal in the middle, surrounded by her own eggs -- inside a sac that once was the "barrel" of a salp. Mothers in the genus Phromina attack the barrel-shaped salps, hollowing out the inside of their sac body before laying their eggs inside. They use the barrel as an egg case to contain the eggs, and then hatched larva, so she can care for them in the open ocean.
This amphipod was photographed by researchers from the Census of Marine Zooplankton in the Sargasso Sea.
See more photos of cool zooplankton collected by the researchers in this zooplankton biodiversity slideshow.