I was just listening to a podcast about how sea sponges use the pores all over their body to “bring in food and release wastes” and I’m pretty sure that’s a scientific way of saying the holes in sponges are all just mouths and buttholes so does that mean that when I’m using a sponge in the shower I’m cleaning my body with mouths and buttholes? Someone get me a marine biologist. And a loofah. And maybe some bleach.  -The Bloggess

All around you are animals with a single hole serving as both a mouth and anus.  These mono-orifice animals have an incomplete digestive system.  In contrast, those animals blessed with two holes, a tubular digestive system with an in and out hole, possess a complete digestive system.

Sponges are a bit of a unique case as a loose conglomeration of cells in a body full of pores and channels.  None of this really resembles organs or a digestive system with digesting occurring within individual cells.  However, the Cnidarians, including jellyfish, anemones, and corals,  are all uni-aperture.  We can also add the Ctenophores, the comb jellies, into this lone door group of animals.

In the flatworms, the Platyhelminthes, its mixed bag of one, two, and even more bodily gateways.  Most flatworms have no anus, but some particularly long species do possess an anus. In rare cases, flatworms with very complex branch guts can have more than one anus.  By the way, the plural can be either anuses or ani.

Peeping at the underside of a starfish, you might have only noticed a giant mouth.  You may be thinking to yourself, “I’ve never seen another opening.  Do starfishes have an anus?”  Of course, this is one of the great questions of life.  Indeed,  most starfishes have a complete digestive system with the anus being a small opening on the top. However, there is a large order of starfish, the Paxillosida, that lack an anus.  The only other group of Echinoderms to lack an anus, and even an intestine, is the brittle stars.

A solitary black hole may also occur during specific phases of animals life cycle.  An incomplete digestive system is known in some insects including the sap-sucking aphid relatives, the Phylloxera, during their sexual phase.  Some larvae including those of some fish and proboscis worms can be anally deficient.  Certain lifestyles also can lead to solo agujero such as in parasitic species, like parasitic copepods.

It’s important to remember that all animals start development with one hole, the blastopore.  In the ventrally chosen, a second hole forms later.  So the question remains if some animals form only a single hole is it a mouth that used as anus or anus used as a mouth?  The proverbial digestive pore chicken and egg scenario.

As described in this excellent post, 

Blastopore formation is started by a protein called disheveled, which gets stuck at the top of the egg and then activates a specific set of genes. In the same location of jellyfish embryos, however, there are genes strikingly similar to the mouth genes of bilaterians. In the sea urchin, a bilaterian, these same mouth genes are also on the top of the embryo. However, disheveled has moved to the bottom. The blastopore forms at this new site of disheveled accumulation, rather than at the mouth. The mouth genes that remain on top still direct the formation of the mouth there. Martindale and Hejnol posit that moving disheveled from the top to the bottom of the embryo in some animals moved the location of blastopore, but that the mouth stayed put. In some bilaterians, like urchins and humans, the blastopore then became the anus. In this scenario all mouths are homologous to each other, whether the animal has one or two holes.

Evolution can be a truly wonderful thing and then sometimes it can produce an animal with a mouth that still uses its anus to feed.

The post A Tale of One Opening first appeared on Deep Sea News.

One of the most obscure invertebrates of all of the ocean is the Entoprocta. It doesn’t take a student of Latin to understand that it’s name means “anus inside”.  Sure, it’s unfortunate, and all the well-to-do invertebrate biologist prefer the name Kamptozoa, meaning “curved animals”, but I prefer Entoprocta for the same reason I prefer American muscle cars over European sports cars, pork BBQ to filet mignon, and Stove Top Stuffing to dried cranberry whole bread stuffing.  It’s the same reason you prefer to get your marine science news from DSN instead of, well, just about anywhere else.  Sometimes less refined is just easier to relate to.

Anyway, Entoprocts don’t get a lot of attention, which is strange because if you had anus in your name I’m pretty sure people would stop and take notice. These little goblet shaped animals typically occur along a colonial network of stolons where, if they have any sense of humor at all (and I like to think they do), they spend their time giggling about their name.  At the top of the goblet is a crown of tentacles with cilia that draw particles into their patiently waiting mouths.  However, both the mouth and the anus lie inside this crown, hence the crass name.

Of the 140 species of Entoprocts  the largest zooid is less than ¼ inch tall  (7 mm) and 3 of the largest zooids would still fit on a U.S. penny. Most of these species are also commensal on worms, sponges, and other invertebrates.  It’s unclear whether their buddies also giggle about their unfortunate name.  With few exceptions, most species are found in less than 50 meters of water.  Only one species occurs deeper than 700 m.  This colonial Ectoproct was found at 4130 meters.

But, wait!

A new species has been described by Anastasia Borisanova and collaborators in Russia that beats the record by more than 1000 meters.  Loxosomella profundorum, a completely new species, was found at 5222 meters in the Kamchatka Trench in the northwest Pacific Ocean. The profundorum is Latin for “deep sea”.  The total length of this species is 4 mm putting it at the larger side for Ectoproct zooids.  Unlike its relatives,  this rare endo anal critter is solitary.  Sad, really. I have to wonder if it’s the name. The deep sea is a pretty harsh place to live.

Borisanova, A., Chernyshev, A., Neretina, T., & Stupnikova, A. (2014). Description and phylogenetic position of the first abyssal solitary kamptozoan species from the Kuril-Kamchatka trench area: Loxosomella profundorum sp. Nov. (Kamptozoa: Loxosomatidae) Deep Sea Research Part II: Topical Studies in Oceanography DOI: 10.1016/j.dsr2.2014.07.016

The post A New Inside Anus Found Very Deep first appeared on Deep Sea News.

Why would you do this outside of ensuring a clean derriere?

Moving large volumes of water across the anus, like a biological bidet, might help with excretion, but it could also be used for respiration.  Think of all that surface area available to diffuse oxygen out of the water into the body!  Or the anus could even be used for feeding…

Wait, what?

In the words of a newly published study (honest to god this is the very first line of the paper),

“An animal is not expected to ingest food through its anus.”

In adult sea cucumbers the cloaca (a cavity already doing double duty for the release of excrement and genital products) rhythmically pumps huge amounts of water in and out. It is already known that this pumping brings oxygen rich water across a highly branched respiratory tree.  Thus the cloaca is now pulling a function trifecta.  But what about quadfecta?

William Jaeckle and Richard Strathmann placed Parastichopus californicus, a beast of sea cucumber lending to its common name the Giant California Sea Cucumber, in aquarium with a single celled algae labeled with a radioactive isotope of carbon.  At several time intervals Jaeckle and Strathmann looked inside the sea cucumbers to see where the radioactive carbon went.  They also repeated this with some larger iron-labeled molecules.

After some time the respiratory tree, that only receives outside water through the anus, was resplendent with iron and radioactive carbon.  In other words, food passed through the anus and was taken up the respiratory organs.  The highest concentrations were found in a unique organ called he rete mirabile that serves as a go-between for the respiratory tree and gut.

So, yes, sea cucumbers can eat through their anuses. The authors refer to this more scientifically as “bipolar feeding.” The authors do note that the amount of food taken in through the anus is likely to be small, given that the…ahem…exchange of water is only likely to be about ¼ to 4 cups of water an hour.

William. B. Jaeckle and Richard. R. Strathmann The anus as a second mouth: anal suspension feeding by an oral deposit-feeding sea cucumber Invertebrate Biology 132.  Article first published online: 29 JAN 2013 | DOI: 10.1111/ivb.12009

UPDATE: I see Echinoblog has beaten me to the punch on this one.

The post Butt munchers first appeared on Deep Sea News.