Mussel of the

Page last updated
3 April 2019

Mussel of the Month

The 2019 Mussels of the Month, so far...

March 2019

UtterbackiaUtterbackia peggyae (Unionidae, Nearctic)

The March 2019 Mussel of the Month is Utterbackia peggyae. Utterbackia is a genus of three species from eastern North America.

Utterbackia imbecillis was the Mussel of the Month almost five years ago. There are still lots of genera we haven’t even gotten to yet, but we wanted to honor our friend Richard Johnson this month with a freshwater mussel that he named, so we chose U. peggyae. Richard has a birthday coming up, and we were recently reminded that he is probably the longest surviving member of the American Malacological Society/Union (Mikkelsen, 2010). Richard Johnson attended his first AMU meeting in his teens before World War II (Boss, 1998)!

During Richard Johnson’s career in the Mollusk Department at Harvard’s Museum of Comparative Zoology, he contributed to our knowledge of freshwater mussel systematics in important and lasting ways. He published type catalogues for many of the most important collections (e.g., Lamarck, Lea, MCZ, UMMZ, ANSP) and biographies of significant malacologists (e.g., Ortmann, Frierson, Call). He took on Elliptio and other genera on the Atlantic Slope, post-Pleistocene biogeography (Johnson, 1980), and a revision of Epioblasma. Richard also described new species, and he did so with memorable flair. There are the three he named for the women in his life, Haasodonta fannyae, Utterbackia peggyae, and Margaritifera marrianae. That is probably the most romantic thing we have ever heard of. He also named three more by mildly Latinizing concatenations of the names of his contemporary unio aficionados. Samuel L.H. Fuller, Pieter W. Kat, Carol B. Stein, David H. Stansbery, Artie L. Metcalf, Raymond W. Neck, and Dwight W. Taylor have been immortalized as Lampsilis fullerkati, Parvaspina steinstansana, and Potamilus metnecktayi. It should be remembered that much of this work was done before freshwater mussels attracted the attention they do today. Back in the day, Unionidae was just another obscure family of bivalves.

We also know Richard Johnson as a generous friend and mentor, serving on DLG’s M.Sc. thesis committee. Thank you, Mr. Johnson, for your contributions to freshwater malacology!

February 2019

MonodontinaMonodontina vondembuschiana (Unionidae, Indotropical)

The February 2019 Mussel of the Month is Monodontina vondembuschiana. Monodontina is a genus of four species from southeastern Asia, from Indochina to the Sunda Islands.

Monodontina vondembuschiana is the type species of the recently recognized genus, Monodontina. M. vondembuschiana has traditionally been classified as a Pseudodon (Zieritz et al., 2018), but that genus has been blown-up by the phylogenetic work of Bolotov et al. (2017).

In our global checklist (Graf & Cummings, 2007), we divided the almost two dozen species of Pseudodon among nine subgenera. There were only a handful genera that caused us to worry about subgenera back then — Alasmidonta, Arcidens, Lasmigona, Parreysia, Pseudodon, Prisodon, and Hyridella. These were generally taxa with many species and either some suggestion that they might be excessively lumped or just in need of clarification how the taxonomy we followed corresponded to other classifications. Some of those lumpings have been rectified, such as Prisodon sensu latu (= Prisodon sensu stricto and Triplodon), Parreysia s.l. (= Parreysia s.s., Leoparreysia, Indonaia, and Radiatula), and Pseudodon s.l.

The former species of Pseudodon s.l. are now split among Pseudodon s.s., Monodontina, and Bineurus based on the non-monophyly of the old genus (Bolotov et al., 2017). Either Pseudodon needed to be broken up or the species of Pilsbryoconcha had to be folded in. So, where there were two genera, we now have four. The phylogenetic relationships among the other six subgenera of Pseudodon have yet to be fully explored.

January 2019

GibbosulaGibbosula rochechouartii (Margaritiferidae, Indotropical)

The January 2019 Mussel of the Month is Gibbosula rochechouartii. Gibbosula is a genus of six species in southeast Asia, from Myanmar to China.

Gibbosula rochechouartii is a new genus for this freshwater mussel species. If you have been keeping track like we have, then a mussel species being reclassified from one genus to another won't blow your mind. Based on the data in the MUSSELpdb, each valid freshwater mussel species has, on average, been classified in more than 4 different genera (4.46 to be precise). Among the "champions"* in this regard is Ortmanniana ligamentina. Over the last couple hundred years, that species and its synonyms have been classified under 14 different genera (e.g., Unio, Obliquaria, Lampsilis, Nephronaias, Actinonaias, Ellipsaria, Venustaconcha, Ligumia) — and that number goes even higher if we consider subgenera.

The classification of G. rochechouartii had been pretty straight forward until very recently. It was originally described in Unio (like most freshwater mussels of the 19th century). Simpson (1914) classified it as Quadrula (Lamprotula), and then Haas (1969) moved it to Lamprotula.** And there it stayed for decades. "L." rochechouartii held its position even after Lamprotula was up-ended and split to move 7 species to Aculamprotula in a different subfamily because not all bumpy, thick-shelled Asian freshwater mussels necessarily belong to the same genus (Zhou et al., 2007; Pfeiffer et al., 2013).

But then last year, some fresh phylogenetic work by Huang et al. (2018) recovered our Mussel of the Month in the family Margaritiferidae, rather than Unionidae where it and the rest of Lamprotula (and Aculamprotula) had always been. Recent phylogenetic work had confirmed that all the Recent margaritiferids can be classified as Margaritifera (Graf & Cummings, 2007; Araujo et al., 2016; Bolotov et al., 2016), so our mussel became Margaritifera rochechouartii.

And then again last year, a more comprehensive analysis by Lopes-Lima, Bolotov et al. (2018) examined a wider array of taxa and data, and the classification of margaritiferids changed course. Not only did they advocate splitting the Recent Margaritiferidae back into multiple genera (as had been done by Smith, 2001 and almost everyone before), but we even have subfamilies now. "M." rochechouartii became Gibbosula rochechouartii in the subfamily Gibbosulinae. G. rochechouartii sat for more than 100 years in the genus (or subgenus) Lamprotula in the family Unionidae, and then WHAM, BAM, thank-you CLAM — two more different genera and a change in family.

Fortunately, the MUSSELpdb is available to help you keep score with freshwater bivalve taxonomy! As we have discussed in various posts over the last few months, freshwater mussel taxonomy has been changing at an almost unprecedented pace. This can be attributed to:

  • the increase in the availability of molecular sequences,
  • the increase in the number of people working on these questions, and
  • a greater willingness to make post hoc revisions based on phylogenetic tree topologies — every node on a cladogram apparently gets a name now.

The table summarizes the history of the taxonomic shifts described in this post.

* If confusion = winning.
** The MUSSELpdb currently holds no references to this species dating between 1914 and 1969. As we have recently noted, those years were slow ones for mussel taxonomy. There may be data out there, but we haven't captured it yet.

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