The hunt for glass sponge larvae…with SCUBA

Last year, we found sperm and eggs in some of the glass sponges collected during our research cruise in the Strait of Georgia.  This is big news, since other than a single larvae noticed by Sally in 1995, no larvae have ever been found from Aphrocallistes vastus–even though this species, along with two others, forms the foundation of the extensive reefs found in the Strait of Georgia and Hecate Strait.  Sally and her two graduate students that are studying the sponge reefs, Rachel Brown and Amanda Kahn, planned a trip to scuba dive to some of the non-reef, but shallow, individuals of Aphrocallistes vastus to look for larvae and collect some sponges for Amanda’s studies on their growth (more on that in a later post).  Amanda and Rachel both became sick the week of the trip, however, so only Sally got to do the dive, while Amanda helped on the surface and in the lab afterwards and Rachel stayed in Edmonton to recover.

We flew out to Victoria on Friday night and the next morning met our dive charter folks, Jesse and Scott from Pinnacle Scuba Adventures, and headed to our dive site.  McCurdy Point is an area with conditions we’d expect sponges to like: it is near the sill of Saanich Inlet and situated at a point, so water flows quite strongly through there.  Amanda could not dive because she was recovering from an illness, but Sally, Scott the divemaster, and Parm, a local diver who generously took Amanda’s place so Sally would have a dive buddy, headed into the water down a mooring.

After descending below the pycnocline, visibility opened up from what looked to be about 10 feet to somewhere closer to 70 feet.  The three divers descended to 125 feet, where the first cloud sponges rested.  Sally carefully collected small pieces within which we can search for larvae.

While we didn’t see any larvae visible with the naked eye, we preserved pieces for electron and light microscopy to have a closer look later.  Preserving them correctly takes care and time, and we were able to set up a mini lab in the Marine Technology Centre in Sidney so we could give the fixations the attention they require.

Not all of the sponge pieces were fixed to search for larvae.  The small pieces of live sponge are being kept alive in an incubator in water brought up with them.  Amanda is incubating pieces of these sponges in a label that gets incorporated into newly synthesized DNA, with the aim of determining how, and how quickly, new tissue is laid down in glass sponges.  Glass sponges are syncytial, meaning each sponge has a common cell membrane with many nuclei within.  Amanda hypothesizes that because of their syncytial structure, the sponges require less energy to build themselves than other, cellular, sponges.