SpeciesDay - Unionidae

It's been a bit quieter around here than Kevin and I prefer, but now the finals are all done and I can finally say "I can has cheezburger wit dat?"

Seriously though, in the next month or so there will be some changes in this space... in the mean time:

Did you know there are 198 199 invertebrates listed under the Endangered Species Act?

Yep, inverts make up 34% of the 575 animals protected under ESA. But is this good or bad that inverts are underrepresented here??

Care to guess how many of those 198 199 are molluscs?
I'll give you a starting point - only two of the 198 199 invert species protected under ESA are cnidarians. Elkhorn Coral (Acropora palmata) and Staghorn Coral (Acropora cervicornis) are listed as Threatened. First correct answer, gets a small hand made tote bag free (allow 3-4 weeks for creation and delivery though!)

Today, May 15th is Endangered Species Day, and the the net was all atwitter with postings and tweets about endangered species. I just got done with the prototype for an outreach product that includes some of those endangered molluscs so I tweeted out the Shinyrayed Pocketbook (Lampsilis subangulata) a member of that marvelous group of freshwater mussels, the Unionidae.

If you recall from our earlier posting, this is the group of freshwater bivalves that has the habit of spitting its spawn into the face of an unsuspecting fish. The spawn are technically a form of larvae unique to these mussels called the glochidia and for some reason all my vertebrate loving friends seem to think that the whole "spewing spawn in your face" technique is rather disturbing. The young molluscs that are now in the face and mouth of the hapless fish attach to the its gills and encyst there. They feed on the blood in the gills until they are ready to drop to the sediments and metamorphose into a full adult form.

The shiney-rayed pocketbook is found in Alabama, Florida and Georgia, mainly in the Chattahoochie and Flint rivers. In its most recent review it was assessed as endangered with a recovery priority of 5 (high threat and low potential for recovery). The good news though is that from 2003 to 2007 the range of the Shiney-rayed Pocketbook did extend into more of the river than it had been in recent years.

The shiney-rayed pocketbook handles the details of reproduction and larval distribution a little differently than our last Unionoida. Our last fresh water mollusc, the Snuffbox, lures a fish in with it's mantle flaps which look like a small fish. When the fish attacks the lure, the snuffbox springs its trap, catching the logperch's head between it's valves. It then uses it's mantle to smother the fish for a few moments. When it releases the smothering hold on the fish a little, it also releases it's glochidia which is has been brooding in the shell. The fish gasps for water (air) and gets water and glochidia.

The shiney-ray takes another very interesting tack at larval distribution. Its females also brood the young until they reach the glochidia stage then release them to parasitise largemouth bass (Micropterus salmoides) and spotted bass (M. punctatus). The season for releasing glochidia will be begin in just a few weeks, late May through August.) The females, create a superconglutinate, a group of large packets (conglutiates) of glochidia attached to what appears to be a long transparent mucus rope.

The superconglutinate strongly resembles a small fish, which lures in larger predatory fish. When a larger fish attacks the superconglutinate the mass ruptures and glochidia are freed to attach to the gills of the fish. The glochidia parasitize a fish host until they are ready (able?) to metamorphose into juvenile mussels and settle to the substrate in sandy or muddy, slow moving regions. It is thought that the main purpose of the parasitic stage is not actually for nutrition and growth, but for transportation and distribution since the larvae would be unable to fight even a weak river flow to hold position or fight upstream, but attached to a fishes gills they can expand upstream or at least maintain position. This is borne out to some degree by recent expansion of L. subangulata up current in some locations.

Of course a video is highly warranted here, so courtesy of M.C. Barnhart, I give you the close cousin of L. subangulata showig off her superconglutinate. The orange-nacre mucket (Lampsilis perovalis, the species in the video, is one of only 2-3 other species known to create a superconglutinate.



References:

Roe, K., Hartfield, P., & Lydeard, C. (2001). Phylogeographic analysis of the threatened and endangered superconglutinate-producing mussels of the genus Lampsilis (Bivalvia: Unionidae) Molecular Ecology, 10 (9), 2225-2234 DOI: 10.1046/j.1365-294X.2001.01361.x

Bogan, A., & Roe, K. (2008). Freshwater bivalve (Unioniformes) diversity, systematics, and evolution: status and future directions Journal of the North American Benthological Society, 27 (2), 349-369 DOI: 10.1899/07-069.1

Barnhart, M., Haag, W., & Roston, W. (2008). Adaptations to host infection and larval parasitism in Unionoida Journal of the North American Benthological Society, 27 (2), 370-394 DOI: 10.1899/07-093.1