Nature continues to astound us: there are millions of undescribed species, and many of them defy even the most fertile imagination.
Have a look at the creature below (no, it’s not a plant), and guess what it is (I’ve left the title ambiguous).
It’s a sponge. And if that’s not weird enough, it’s a carnivorous sponge: it apparently eats copepods, small aquatic crustaceans.
As you may know, the vast majority of sponges are filter feeders, removing organic particles (bacteria and phytoplankton) from water by sucking it in, taking out the good stuff, and expelling the water. But in the deep sea, where organic material is scarce, some sponges have taken up the habit of eating animals. While this has been known for 17 years, beginning in 2000 and continuing through 2007, a series of deep-sea dives using remotely operated submarine vehicles have discovered these weird creatures living off the California coast at about 3300 m. down (that’s nearly two miles!).
The paper describing this new species, Chondrocladia lyra, was just published in Invertebrate Biology by Welton Lee et al. (reference and link to abstract below; full paper is below a paywall but I can send a pdf to those interested). The paper is long and (for those who don’t love sponges) rather tedious, but the finding is exciting: this thing preys on other animals (sponges are, of course animals themselves).
Fig. 2 from paper: In situ images of Chondrocladia lyra sp. nov. recorded by ROV’s Tiburon and Doc Ricketts. Dives are identified by the first initial of the ROV followed by the dive number (see Table 1). A. Digital still image of T891-A2 (holotype)showing three vanes. B. Video frame grab of T197-A6 (paratype) showing two vanes. C. Video frame grab from T1046showing four vanes. D. Video frame grab from D26 showing five vanes.
As I said, Chondrocladia lyra is not the first carnivorous sponge to be discovered. Below is a picture of Asbestopluma hypogea (great genus name!) capturing a crustacean. A. hypogea is a Hexactinellidid sponge (aka a “glass sponge”), which spikes tiny crustacea and then curls round them before consuming its prey through phagocytosis. It lives in underwater caves off Spain, Croatia, and France.
Surprisingly, Chondrocladia lyra is not closely related to Absbestopluma – it is a demospongid, a group that makes up 95% of sponges. According to this recent phylogeny, Hexactinellida and Demospongiae are more closely related to each other than either are to the third group of sponges, the Calcarea.
It’s not yet clear how the weird sponge at the top captures copepods, since its feeding hasn’t been described in the wild; partly digested copepods were found embedded in the bodies of collected (ergo dead) specimens. Prey may be captured by small filaments on the surface of the sponge and then transferred to the surface of the “branches,” where they are engulfed and then digested. It will be hard to see this since the specimens obviously can’t be kept in aquaria, and they lie too deep to be observed directly.
h/t: Matthew Cobb via NeuroDojo
Lee WL, Reiswig HM, Austin WC, Lundsten L. 2012. An extraordinary new carnivorous sponge, Chondrocladia lyra, in the new subgenus Symmetrocladia (Demospongiae, Cladorhizidae), from off of northern California, USA. Invertebrate Biology: in press. http://onlinelibrary.wiley.com/doi/10.1111/ivb.12001/abstract DOI: 10.1111/ivb.12001