Huh? What is going on? I knew these animals had been collected from an intertidal area with surfgrass, but they looked like caddisflies from streams!
Maddy had spotted these tiny crustaceans walking around in the most beautiful, perfectly cylindrical tubes. For scale, this tube was only ~5 mm long and ~1 mm in diameter.
Below are two more views. You can see the wonderful antennae, bright orange with clear tips. I eventually figured out that these are tube-dwelling amphipods.
The amphipods would sometimes start to emerge from the tube, revealing a little more of their elongated bodies, but they never left the tubes completely. The amphipods could reverse direction and emerge from the opposite end of their
tube, and Eric noticed that they could attach the tube to an object
(like a seagrass blade) with a strand of silk.
I was fascinated by the expertly crafted tubes. What were they made of? (Could it be material from surfgrass roots?) How did the amphipods make the tubes? The stripes on the tubes seemed so regular that it didn't seem like they were unprocessed bits of debris stuck together, but could they have been "woven" by the amphipod? And what happens when the amphipods need to molt to grow? How do males and females mate?
Here's a close-up of one of the tubes:
It's been a little bit of a windy road trying to identify which species of amphipod this is. Spending some time with the Light & Smith Manual, I wondered if they could be a species of Cerapus. However, I found a newer document online that makes it seem like there has been some taxonomic confusion in this group and they now might be considered an undescribed species of Notopoma. I'll need to consult with some experts, and we are eager to figure out more about the identity and biology of these amphipods, so stay tuned.
All these years looking at intertidal marine invertebrates, and I had no idea there were these amazing little tube-dwelling amphipods wandering around in surfgrass beds. I suppose that shouldn't be surprising, but it's so awesome when you realize that there's an endless amount to discover in our own backyards!
This amphipod is brought to you thanks to Maddy's sharp eyes and to Eric's skill with the microscope camera. I'm so thankful to have been introduced to such a cool critter!
Wow! Thanks for sharing! These are adorable! I'm not familiar with Notopoma, but they're part of a larger group of amphipods that are capable of producing silk (as you noted), which is typically used in the construction of their tubes. Most tube-dwelling amphipods will adhere bits of detritus (sometimes their own feces) to the silk of their tubes, but I've never seen one with such clear stripes! It looks like the silk was laid down in layers, and it's not unreasonable to think there might be some surfgrass material in there.
ReplyDeleteOther male amphipods in the family Ischyroceridae typically leave their tubes to search for females once they've reached their terminal molt. Like lots of other crustaceans, some species will stand guard over female tubes until the female has molted and is receptive to mating. What I'm not clear on is whether mating happens inside the tube or not; it seems like it might get a little cramped! Of course, if the amphipods are carrying their tubes around with them, their mating behavior might be totally different! Super cool.
Super cool. That tube looks like Notopoma. Need to see the specimens but they are not like the anything I have seen direcltty anndd hard to imagine that Notopoma was there when I was in the mid 70s and was checking our intertidal ischyrocerids.
ReplyDeleteWow! I observed/illustrated the very similar Cerapus tubularis from a plankton tow in South Carolina a number of years ago, for the book Zooplankton of the Atlantic and Gulf Coasts. Entrancing to watch!
ReplyDeleteMe too, I found it and posted it on Inaturalist, no one was able to identify it, but coming to this site I know a little more, mine was found at North Myrtle Beach, Summer of 2021
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