I was casually checking the numbers for the Echinoblog over a July 4th weekend in 2009 and on the day just before a 3 day weekend I found there was a HUGE spike of hits (>600 in one day!) simultaneously and inexplicably searching for something that I narrowed down to a massive international search for the term "sea pig".
Reasons were offered: A new Facebook quiz app.
A video on Youtube. Who knows?
But if the PUBLIC wants to know what a SEA PIG is and I KNOW??? Then Frak it!! Its my duty to society to tell it WHAT a sea pig is!!! Who am I to deny the public's interest in sea pigs??
So, let's get to it!
What is a Sea Pig??
The "sea pig" is the common name (i.e. non-scientific name) for a species of sea cucumber (in the class Holothuroidea) that lives in the deepest abyssal depths of the world's oceans.
Specifically sea pigs belong to the
genus Scotoplanes, a genus of deep-sea sea cucumber which currently includes four species. Sometimes other genera of deep-sea sea-cucumbers are called "sea pigs", but historically, THIS is the one most people mean. Its not entirely clear if those four species are all distinct, but THAT is a discussion for another day...
The name
Scotoplanes has been around for a LONG time. The genus was discovered and described by H. Theel in 1882 as part of the famous HMS
Challenger expedition reports. Sea pigs are ELASIOPODID sea cucumbers, an order of sea cucumbers whose members are prominent in the deep-sea.
They are often characterized by having these little legs that come off the bottom surface such as what you see here (legs on side, mouth pointing outwards)
One species,
Scotoplanes globosa seems to be particularly widespread with a distribution that is WORLDWIDE. Yup. That's right you can find it in the Atlantic, the Pacific, in the Indian Ocean and of course..in the Southern Ocean (Antarctica).
Because waters in the Southern Ocean (Antarctica) are so cold, sea pigs can be found in shallower waters around the South Pole. Pictured here is one collected during
the recent expedition operated by the New Zealanders and held by NIWA scientist (and friend of the Echinoblog) Sadie Mills:
(Photo credit:
Richard O'Driscoll, NZ IPY-CAML)
How do Sea Pigs Live ???
Scotoplanes live in the ABYSS. That's not just a
little deep..that's the DEEPEST part of the ocean on the flat oceanic plains. Its not unusual for sea pigs to be collected from over 6000 meters!!! How deep is that? That's about 3.7 miles DOWN (by contrast the Grand Canyon at its deepest point is only about 1.1 miles deep). Some can be found shallower..but they live across a wide bathymetric range.
Scotoplanes don't just occur individually either. Collections and observations of these animals show that they often number in the
hundreds. Early trawling records have recorded some 300-600 specimens per trawl!!!
What do they do down there??
Very little is known about
Scotoplanes general biology, but we do know a thing or two about their nutriton.
Like a lot of other deep-sea sea cucumbers, Sea pigs are what's called
deposit or detrital feeders. That is, they feed on the fine nutritious scum and goo that falls to the bottom of the seafloor from the top of the ocean. They feed on them with the ring of tentacles that surrounds the mouth...
(This image from the Galathea 3 expedition site)
BUT contrary to some accounts that these are "slug like" or coarse dirt worms, deep-sea cukes like
Scotoplanes have evolved this feeding mode into a finely honed adaptation!!
For instance,
this study by Robert Miller et al. (2000) studied several deep-sea cuke species from the North Pacific, including
Scotoplanes globosa using isotope tracers.
S. globosa (and other species in the region) ingests only VERY fresh (and presumably very rich) food-rich sediments. This species (and others like it) feed on a thin veneer of food that had settled out of the water column the last 100 days. So they actually eat FRESH food.
(from Gage & Tyler 1991)
Other facts of interest??
1. According to
Dave Pawson, Smithsonian Curator of Echinoderms (and an expert in deep-sea sea cucumbers) you can also often see this species all oriented in a particular direction (such as above) facing into the current, where they are presumably rooting around, searching for better and fresher goo to eat
2. According to this
study summarized by the Monterey Bay Aquarium Research Institue and performed by marine biologist Henry Ruhl, the food that these beasts eat (which as a reminder- live at THOUSANDS of METERS depth) ARE directly influenced by what comes down from the SURFACE of the ocean!! Yes, what happens at the SURFACE affects animals that live THREE MILES down!!!
There is apparently a direct correlation between some species and rich food that falls to the ocean fall following certain oceanographic phenomenon such as El Nino.
So, for example, the population numbers of
S. globosa boomed after the rich nutritional particles descended folowing the 1997-1999
El Nino and La Nina periods. Ruhl also found
other relationships between abundance and size (summarized here).
Scotoplanes have parasites!!!
a. Small snails (genus Stilapex) that work their way into the body wall and suck on their juices!! So, what's weirder then sea pigs??? SEA PIG SNAIL PARASITES!!!!
(from the New Zealand R/V Tangaroa weekly log, photo cred-Stefano Schiaparelli, NZ IPY-CAML)
b. Crustacean parasites!! Good Grief!! It gets even worse then that!! Tiny tanaid crustaceans will also BORE little holes into the sea pig body wall and feed on the internal organs!!! Yikes!
FINALLY..one of the neatest things I found out about sea pigs???
They have become SO iconic that A Japanese toy company (Agatsuma) makes small toys (about 1 inch long) of them!!!
Whew!! So, any OTHER questions about sea pigs????
Dr. Alexander Ziegler at the Freie Universitaet Berlin was kind enough to make this very interesting website known to me.
Let's take a look!
The website includes crisp, still images, but also many 3D tomographic "slice" animations (formatted as Quicktime movies), some of them show cross-sections through the body wall and cut-aways illustrating internal structures such as the jaw .
You also get some pretty cool 3-D movies that show the critters in astonishing detail in full rotation like so:
But, go see some of these movies for yourself (click on the right side selections for 3D slices, etc.):
