Hey there Microcosmos community! Today I decided to give my folscope another go; this time with some marine samples I collected – well, how long ago was that now? Oh I guess about three weeks!
Grad school has been keeping me busy this semester, and my invertebrate sample jar from a field day in the Central California Coast rocky intertidal has been sitting (festering?) in my fridge for a few weeks now. At first I considered giving it the good old-fashioned flush, but I figured the scientific community might frown on that level of frivolity. Certainly there must be something good to see! …?

I popped out a glob of what was once a brackish water sponge. Originally orange in color and medium on the firm – to – gooey scale, this bad bird looked more like something out of a boiled booger soup than a spicule-laden filter feeder.
I was able to catch a few quick glimpses of spicules, but none clear enough for a good photo. You can see them on the left in the following video. My biggest trouble was trying to hold everything at once in just the right position. I think for my next post I’ll try out some FoldScope modifications, but more on that later.
https://microcosmos.foldscope.com/wp-content/uploads/2016/05/IMG_2436.m4v
Out of the corner of my scopey eye I started to catch glimpses of movement! You may have seen this in the previous shot. I focused in, and realized I had a plankton party on my hands! Cruising around visibly munching on the rotting organic material were thousands of microscopic plankton!
https://microcosmos.foldscope.com/wp-content/uploads/2016/05/IMG_2438.m4v
I wonder if these little buggeys came stock with the floor-model sponge. Is it possible that these organisms live symbiotically within the sponge to keep its ostia clear of obstruction? Could they be serving this function until the sponge dies, at which time they have a full-scale chow-down, aiding in its decomposition? Or is it possible that they are just the most suited organisms for a rotting-fridge saltwater habitat?
Further research led me to find that this is nothing new to science; sponges are some of the oldest organisms out there, and being the holey filter-feeders they are, are generally subject to the intake of a great number of parasites. Over evolutionary time-scales, however, those parasites turned symbionts in some cases. From cyanobacteria (blue-green algae) to zooxanthellae (more commonly known as coral symbionts), these buggers are actually common within and important to sponges! Turns out they serve the ecological function of providing nutrients to the host organism in exchange for a place to rest their unicellular heads(&bodies) (Vacelet, 1981).
The jury is still out as to which specific micronutrients are being shared in this symbiotic relationship, but advances in metagenomic research is aiding in the examination of this phenomenon. The general understanding is that symbionts assist in the conversion of nutrients to more bioavailable forms, much like the bacteria of the human gut (Colman, 2015).
Wow! As a marine science student I’ve learned about these small-scale nutrient transfer processes with regard to other organisms such as coral and anemones, but I had never thought to apply the logic to sponges! Feeling very thankful that I didn’t throw out my yucky sample… yet.
Signing off for now, thanks for reading!
References:
Colman A.S. 2015. Sponge symbionts and the marine P cycle. Proceedings of the National Academy of Sciences of the United States of America. 112(14):4191 – 4192.
Vacelet J. 1981. Algal-sponge symbioses in the coral reefs of New Caledonia: A morphological study. Proceedings of the Fourth Annual Coral Reef Symposium, Manila. 2:713 – 719.