Mussel of the

Page last updated
30 December 2011

Mussel of the Month

The 2011 Mussels of the Month.

December 2011

Acuticosta chinensisAcuticosta chinensis (Unionidae, Indotropical)

The December 2011 Mussel of the Month is Acuticosta chinensis. Acuticosta is a genus of six species from the Yangtze River in China.

The last Mussel of the Month of the year is Acuticosta chinensis. This species has been included in phylogenetic analyses of Chinese freshwater mussels, and as such its phylogenetic position is well understood: Unionidae, Unioninae, Unionini.

We don't have much to say about it. It is a good looking shell, and we will leave it at that.

November 2011

Oxynaia jourdyiOxynaia jourdyi (Unionidae, Indotropical)

The November 2011 Mussel of the Month is Oxynaia jourdyi. Oxynaia is a genus of five species ranging from Indochina west to Burma.

Oxynaia is a genus of freshwater mussel that recently came on to our radar. We had received specimens of O. pugio that the folks at the California Academy of Natural Sciences collected in Burma, and we applied those in a phylogenetic analysis of tropical mussel lineages. That work has recently been published (Whelan et al., 2011), and the November Mussel of the Month is a good opportunity to discuss those results.

For the last long while, we had regarded the genus Oxynaia as part of a large poorly understood assemblage of incertae sedis Indotropical mussels (Graf & Cummings, 2006). Click here to see the classification that we used to apply on this web site. The reason those taxa were treated as of unknown phylogenetic position was simply because most genera had not been analyzed in any phylogenetic study. The available taxonomy dated from Modell (1942, 1964) and Starobogatov (1970). Those studies pre-dated widespread application of cladistic methods and were irreconcilably divergent in their hypothesized classifications. All we could say was that those mussels belong to the Unionidae.

Our recent analysis (Whelan et al., 2011) had much broader tropical taxon sampling than any previous study, and as a result we discovered a heretofore neglected clade, the Parreysiinae. The Parreysiinae includes not only Indian genera like Parreysia, but also African genera like Coelatura and genera like Oxynaia that extend east through Indochina. So far, we have only used molecular characters to resolve the Parreysiinae, but we are currently working to include morphological characters in a larger study of tropical freshwater mussels of the family Unionidae.

In the meantime, we have updated the preferred classification on this site.

October 2011

Lampsilis virescensLampsilis virescens (Unionidae, Nearctic)

The October 2011 Mussel of the Month is Lampsilis virescens. Lampsilis is a genus of 24 species in eastern North America.

It is well known that freshwater mussels in general are imperiled in North America and elsewhere. the USA, the US Fish & Wildlife Service reports 71 species as endangered. One of these is Lampsilis virescens, known to those that can't read italics as the Alabama Lampmussel. The species has always been restricted to the interior basin in Alabama and Tennessee (Williams et al., 2008), but now it is only known from two tributaries of the Tennessee River.

Of course, we have already covered Lampsilis in our monthly exploration of unionoid diversity, but this is a special month for the genus. Our friends at the Alabama Aquatic Biodiversity Center have been raising L. virescens (among other state and federally endangered species) in captivity, and they are set to release a batch of vigorous juveniles into the wild. The hope is that stocking these freshwater mussels will replenish dwindling populations. Click here to see a pdf of their press release. We wish them — the mussels and the Alabama Aquatic Biodiversity Center — the best of luck!

Click here to see the latest news on the release of Lampsilis virescens.

September 2011

Unionetta fabaginaUnionetta fabagina (Unionidae, Indotropical)

The September 2011 Mussel of the Month is Unionetta fabagina. Unionetta is a genus of only two species in the Mekong River of southeastern Asia.

Unionetta is one of those genera about which we know almost nothing. A Google Scholar search reveals that the only publication in the last 10 years that cites this mussel is our own global species checklist (Graf & Cummings, 2007). Since things are busy with the beginning of the Fall semester, we will take the opportunity to keep this month's entry short.

August 2011

Friersonia iridellaFriersonia iridella (Unionidae, Neotropical)

The August 2011 Mussel of the Month is Friersonia iridella. Friersonia is a monotypic genus known only from southern Mexico.

Friersonia is a neat little mussel. We have made a bit of a study of Mesoamerican freshwater mussels, and this is one we run into a lot in collections.

What makes this freshwater mussel so interesting is its unique anatomy. There is no doubt that this animal is a lampsiline -- at least in Ortmann's mind, and that is good enough for us. The marsupium, that part of the outer demibranchs where larvae are brooded, is broadly similar to that seen in genera like Lampsilis. However, instead of being limited to the posterior part of the demibranch, it extends over the whole ventral margin.

So, here we have a shell that looks like it might fit nicely in Lampsilis or Villosa or one of those genera, but the reproductive anatomy is quite distinctive. We wish we knew what this meant. Is Friersonia some relictual lampsiline, the bearer of some ancient otherwise extinct morphology? Or, does F. iridella represent some highly modified off-shoot with a specialized marsupium?

July 2011

Fossula fossiculiferaFossula fossiculifera (Mycetopodidae, Neotropical)

The July 2011 Mussel of the Month is Fossula fossiculifera. Fossula is a monotypic genus from tropical South America.

Fossula fossiculifera is one of those Neotropical mycetopodids that is emblematic of the lack of phylogenetic data available for tropical freshwater mussels. The family Mycetopodidae (as it is currently understood) is endemic to South America and sister to the Iridinidae of Africa (as far as we know). These caveats are necessary because no really robust test of mycetopodid relationships has ever been published. I few taxa have been analyzed here and there (reviewed in Graf & Cummings, 2007), but none of them are F. fossiculifera.

So, we are left with a dated traditional arrangement that was concocted in the 1940s by Modell (1942) and Lange de Morretes (1949). This classification, dividing the Mycetopodidae into 4 subfamilies, was endorsed by Parodiz & Bonetto (1963) and is maintained by Bieler et al. (2010). The four subfamilies — Mycetopodinae, Anodontitinae, Leilinae and Monocondylaeinae — are for the most part restricted to only one or two genera each. However, the Monocondylaeinae is has six genera: Monocondylaea, Tamsiella, Haasica, Iheringella, Diplodontites and Fossula. However, this is all a house of cards. We look forward to seeing it knocked down and replaced with a system with more explanatory power.

June 2011

Ctenodesma scheibeneriCtenodesma scheibeneri (Unionidae, Indotropical)

The June 2011 Mussel of the Month is Ctenodesma scheibeneri. Ctenodesma is a genus of two species endemic to the island of Borneo.

There is little to say about Ctenodesma, other than that the genus is reported to be endemic to Borneo (e.g., Haas, 1969). However, the only primary literature we know of from the last 40 years that mentions Ctenodesma reports it from Sumatra (Marwoto, 1987).

May 2011

Obovaria unicolorObovaria unicolor (Unionidae, Neotropical)

The May 2011 Mussel of the Month is Obovaria unicolor. Obovaria is a genus of 6 species found in eastern North America.

A few interesting things could be said about Obovaria unicolor, the freshwater mussel known by those that tolerate common names as the Alabama hickorynut. For example, it is endemic to the Mobile Basin, and it is of conservation concern in the state of Alabama.

But what drew us to choose this species as the MotM is the fact that it was originally described from Tuscaloosa, Alabama — home of the University of Alabama. Tuscaloosa is in our thoughts right now, and it is worth noting the early malacological contributions of the Druid City. Isaac Lea, renowned Philadelphia freshwater mussel describer, had a few contacts in Alabama with whom he traded material. The particular specimen shown here was collected in Tuscaloosa and sent north by a Dr. Budd.

April 2011

Chambardia wissmanniChambardia wissmanni (Iridinidae, Afrotropicall)

The April 2011 Mussel of the Month is Chambardia wissmanni. Chambardia is represented by 11 species in the Afrotropics. The genus is known from most major basins on the continent.

This is a hot time for Central African freshwater mussels, especially Chambardia wissmanni. Two major publications concerned with mussel conservation just became available, and we heard through the grapevine about some successful collecting in the Congo Basin. As strong supporters of both mussel research and conservation, we are pleased to have the opportunity to ride on the coat-tails of others.

The IUCN recently published the report for the Red List assessments of freshwater organisms in Central Africa. The mollusk chapter (Graf et al., 2011) was written by DLG in collaboration with Jørgensen, Van Damme, and Kristensen. And, just today, the Pan-African assessment for freshwater organisms arrived in our mailbox. DLG also contributed to the mollusk chapter in that publication (Seddon et al., 2011). Hopefully, an electronic version will be available shortly from the IUCN Freshwater Biodiversity Unit.

Finally, we've heard from David Gillikin of Union College in Schenectady that he had a successful collecting expedition to the Oubangui River in search of wily freshwater mussels. Gillikin and Steven Bouillon (Katholieke Universiteit Leuven) managed to score quite a haul of Chambardia wissmanni. Whoo!

March 2011

Sinanodonta woodianaSinanodonta woodiana (Unionidae, Palearctic-Indotropical)

The March 2011 Mussel of the Month is Sinanodonta woodiana. The genus Sinaodonta is native to eastern Asia, but one of the two species has been widely introduced.

Over the last thirty years, there has been significant research on the ecological impacts of exotic bivalves (reviewed in Cummings & Graf, 2009 for North America). This concern has been focused on venerid bivalves of the families Dreissenidae and Corbiculidae. However, freshwater mussels can be invasive as well — for example, Sinanodonta woodiana.

Whereas the stereotype of most freshwater mussels is that their ranges are shrinking, S. woodiana is expanding beyond its already broad distribution in temperate and tropical eastern Asia. This mussel was introduced widely as part of the fish trade, carried along during their parasitic phase. Watters (1997) not only documents several primary introductions — e.g., from Siberia (Amur) to Hungary, from China (Yangtze) to Romania, and from Taiwan to Indonesia, Costa Rica, and Hispanola — but also subsequent dispersal from secondary sources. For example, infected Hungarian fishes were imported to France. Mienis (2008) has continued to document spread of Sinanodonta woodiana.

The primary ichthyo-culprits are various species of carp (common, grass, silver, etc.), tilapias, and mosquitofish (Watters, 1997). Some of these exotic carp species are widespread in the United States (and annoying), and given the hardiness of this particular mussel, it is possible that it will spread widely here as well. It is unclear how annoying it will be.

As of 2010, Sinanodonta woodiana was reported in New Jersey. It begins...

February 2011

Uniomerus columbensisUniomerus columbensis (Unionidae, Nearctic)

The February 2011 Mussel of the Month is Uniomerus columbensis. Uniomerus is a genus of four species that is widespread in the Interior and eastern coastal basins of North America.

Like so many freshwater mussel genera, one of the claims to fame of Uniomerus is the extent to which the taxonomy is unsettled and purely utilitarian. For example, despite the amount of research on southeastern USA freshwater mussels, Uniomerus columbensis was elevated from synonymy in 2008 to cover the species found in the Apalachicola system (Williams et al., 2008).

Another interesting feature of (at least some) species of Uniomerus is their ability to withstand extreme dessication. According to Holland (1991), "U. tetralasmus were extremely tolerant of prolonged emersion, with a single individual surviving 699 days at 15° C and 100% RH."

This all contributes to our growing conviction that there is much fruitful systematic research waiting to occur in North America in general and the Gulf coastal basins in particular.

January 2011

Lamprotula gottscheiLamprotula gottschei (Unionidae, Indotropical)

The January 2011 Mussel of the Month is Lamprotula gottschei. Lamprotula is a genus of around 20 species that ranges from tropical Asia north to Korea and Japan.

Lamprotula is emblematic of why the species of the Unionidae need to be revised. The genus was originally introduced by Simpson (1900) as a subgenus of Quadrula: shells with bumps on them, but from SE Asia rather than North America. That classification persisted for 100 years (Haas, 1969), and we listed 26 species in the genus Lamprotula (Graf & Cummings, 2007).

However, at the time, we were unaware of research that had been done in China that demonstrated that "Lamprotula" had species with both hooked and non-hooked type glochidia (Wu, 1998; Zhou et al., 2007). Not only was Lamprotula s.l. polyphyletic, but the species belonged to two different major clades! Today, we use the name Aculamprotula for the 5 species known to have hooked-type glochidia (subfamily Unioninae), and Lamprotula s.s. is retained for the rest of the species.

An analogous split took place with Inversidens and Inversiunio, and we suspect that it will occur again as the species of eastern Asia continue to be evaluated using modern methods.


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