Caprellids

Ok…if you want to find out what a Caprellid is without the family spin skip to the bottom.

One of the family’s big presents this year was a nice zoom dissecting microscope with a set of 50 metazoan and 50 plant biology classroom slides. Johann and Tammy have been going through a few prepared slides per session, but whenever he gets on the scopes at the university, he usually gets to look at bacteria through the epifluorescent scopes or all kinds of zooplankton through the dissecting scopes there, so it is not really the same looking at a dead, prepared slide, many of which are largely unrecognizable as being something once alive.

For one of my classes last week, we did a bivalve particle clearing rate experiment using some mussels (Mytilus edulis) gathered from the water just off campus. As I was separating out some of the mussels in the lab, I noticed a ~15mm character in a preying mantis pose — it looked almost like a walking stick doing a Karate kid final kick, a Caprellid amphipod. I separated the small mussel it was on from the rest of the bunch and put it aside in a beaker. After everything was cleaned up from the experiment, I took the mussel and amphipod home to Johann and Tammy.

When I got home, I set the beaker on the kitchen counter while I stripped off the book satchel, laptop, coat, etc… before I was done Johann was already staring closely at the two occupants of the beaker. By the time I had turned back around, he assaulted me with, “Cool! What is that?! That’s mytilus, but what is THAT?!”

He spent the next hour watching both the caprellid and the mussel, (Gotta love low heat light sources!), calling Tammy and me over to examine some detail he had noticed or watching for some new behavior he just witnessed. The caprellid mostly repeated a pretty set cycle: it did its characteristic pose and swayed its upper body through the water, then remained still for minutes at a time. It did occasionally maneuver to a new location with it’s inchworm style motion.

The mussel opened and closed periodically, which allowed Johann to observe the mantle skirt closely. It also began to cement its byssel threads to the beaker using its foot. Johann watched this both through the scope and with the naked eye. After an hour he had sketched both thoroughly and was done for the night. Tammy, Johann, and I decided we can’t tell exactly what species the caprellid was, though we suspect it is a male Caprella mutica, an invasive species known to be here in the Long Island Sound, specifically in the Mystic estuary.

I took the opportunity to see if I could hand hold the camera and get a decent shot through the scope, with and without one of the 15x occulars in place. While not as nice as having a dedicated imager like we have in the teaching lab, it is a decent result for hand held and a good starting point. I’m thinking about modifying a lens cap/body cap to help in alignment and holding the camera in place.

So what is a caprellid amphipod?

Caprellid amphipods (a.k.a. skeleton shrimp) are small marine crustaceans which have been found on diverse habitats from deep ocean hydrothermal vents to shallow estuarine waters. These small amphipods spend their entire life attached to some form of substrate — usually seaweeds, and encrusting or non-mobile invertebrates such as barnacles, bryozoans, and mussels. They are also often found on docks,ropes, and nets used in aquaculture. Using the last three pairs of appendages, they cling to seaweed, bivalves, or other substrate with their claws (gnathopods) spread wide as they bend side to side waving through the water.

“That’s a caprellid,” said Dr. Jon Moore. To demonstrate its behavior, he and Mercer Brugler invented the “Caprellid dance,” holding up both hands and waving them, while shifting hips from side to side. This made clear to everyone what kind of organism they were looking at.
“Oh yes, the caprellid!”

Log from the NOAA Mountains of the Sea exploration:
May 15 2004

Caprellids appear to be omnivorous opportunists, eating anything including diatoms, copepods, amphipods, and nematodes. In turn they are eaten by a variety of fish, thus they form a link between the single celled algae and predatory fish.

A Caprella mutica male (top) and female from Dr. Gail Ashton’s work at SAMS

Caprella mutica is a fairly recent invader to Long Island Sound. Originally from the shores of Japan and China, it was confirmed in Connecticut waters when it was found at the Mystic Yacht Yard in 2003. C. mutica has also successfully colonized most of Europe’s shores, the Pacific Northwest, and New Zealand. Part of its success stems from its tolerance for a wide range of temperatures (-1.8 to 30°C) and salinities (15 — 35+psu). (Ashton et al. 2007)

Ashton, G. V., Willis, K. J., Cook, E. J. & Burrows, M. (2007). Distribution of the introduced amphipod, Caprella mutica Schurin, 1935 (Amphipoda: Caprellida: Caprellidae) on the west coast of Scotland and a review of its global distribution. Hydrobiologia 590, 31-41
DOI 10.1007/s10750-007-0754-y

Kingdom: Animalia
Phylum: Arthropoda
subPhylum: Crustacea
Class: Malacostraca
Order: Amphipoda
Family: Caprellidea
Genus: Cabrella
species: Caprella mutica