Photo 2812592, (c) Roberto R. Calderón, some rights reserved (CC BY-NC), uploaded by Roberto R. Calderón

Attribution © Roberto R. Calderón
some rights reserved
Uploaded by aguilita aguilita
Source iNaturalist
Associated observations

Photos / Sounds

What

Giant Floater (Pyganodon grandis)

Observer

aguilita

Date

September 10, 2014

Description


@invertzoo @pliffgrieff

Texas Heelsplitter (Potamilus amphichaenus)

10 September 2014

Resubmitting ID: This native large species of freshwater mussel is called Texas Heelsplitter (Potamilus amphichaenus) and occurs most densely in this northern Texas area of the state and is part of the Trinity River water basin per the distribution map presented by the Texas Parks and Wildlife Department (TPWD) and said map can be accessed here: https://tpwd.texas.gov/huntwild/wild/wildlife_diversity/nongame/mussels/media/p_amphichaenus.pdf

With the information provided by Susan J. Hewitt which led us to the TPWD site, we were able to narrow down the fact that only four varieties of freshwater mussels occur in Denton County and its immediate area all of which are related to the Trinity River water basin. These four included in the order of the frequency of their occurrence in the field per the TPWD studies were (see: https://tpwd.texas.gov/huntwild/wild/wildlife_diversity/nongame/mussels/maps.phtml) :

  1. Texas Heelsplitter (Potamilus amphichaenus) (frequency 11-15)
  2. Texas Pigtoe (Fusconaia askewi) (frequency 1-5)
  3. Sandbank Pocketbook (Lampsilis satura) (frequency 1-5)
  4. Louisiana Pigtoe (Pleurobema riddellii) (frequency 1)

We were able to find once we had the name of this freshwater mussel species a Texas freshwater mussel online digital collection at the University of North Texas Digital Library. It’s called the Joseph Britton Freshwater Mussel Collection which provides detailed descriptions and measurements of the species in its collection including digitized dorsal and ventral images which can then be zoomed to access in detail the specifics of the specimen in question. We began our search with the Texas Heelsplitter and believe we found a match especially since this is the most widespread freshwater mussel in this portion of the Trinity River water basin, which is the same region where we made our own observation. You can access the online image of one such Texas Heelsplitter within the UNT Digital Library’s Jopseh Britton Freshwater Mussel Collection here: http://digital.library.unt.edu/explore/collections/JOSEPH/browse/?q=Texas+Heelsplitter&t=fulltext

We ask that you look at Potamilus amphichaenus, Specimen #615, as exemplary of the many other examples provided in the Britton Collection for this species (it’s the one at the top of the page that opens when you click on the link). The characteristics presented match those we found in our own photographic and field observation of the species at the North Lakes Park in Denton, Texas. These are large freshwater mussels and depending on the particular specimen examined in this digital collection one can see that their size ranges from 4-6 inches (100-120 mm), which matches our own observation in the field that these were/are large freshwater mussels. So we have concluded and hope you agree that the species in our iNaturalist observation is none other than Texas Heelsplitter (Potamilus amphichaenus).

The other three species that we examined at the Britton Collection, Texas Pigtoe, Sandbank Pocketbook and Louisiana Pigtoe, did not share the elliptical shape that Texas Heelsplitter exhibits. They are more oval in shape. Texas Pigtoe measured only 60-100 mm. And while Sandbank Pocketbook does attain the length of 100-120 mm that Texas Heelsplitter does, it again shares a more oval rather than elliptical shape as noted. And the Louisiana Pigtoe is very oval in shape and does not grow beyond 60 mm, which makes it too small to fit the much larger size attained by Texas Heelsplitter of 100-120 mm.

In reading the TPWD online study site for Texas freshwater mussels we learned that freshwater mussels across the country (Texas included) are disappearing and they are among the most endangered of species because of challenges presented to their habitats from varied sources including the introduction of competing non-native species.

We wouldn’t have gotten this far in identifying Texas Heelsplitter without the generous assistance in solving this mystery of Susan J. Hewitt and Phil Liff-Grieff and so our many thanks to both colleagues for taking the time to respond to our initial query. This ID belongs to them as much as to our own research into the question. Thanks!

Postscript: I checked and no one has observed a Texas Heelsplitter on iNat to date. If approved, our ID would be the first.

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* Disregard the following ID which was the one we originally presented.

Eastern Elliptio (Elliptio complanata)

10 September 2014: We think this might be a native freshwater mussel that’s found in a wide ranging region of the eastern half of the United States. If we have our ID correct, and even if we don’t (we’d appreciate your correcting us and we thank you in advance for your assistance if so), these were large mussels measuring somewhere in the vicinity of four to five inches. It looked as if there was some predator that was fond of this particular spot at one of the two lakes at the North Lakes Park in Denton, Texas. The remains of at least four different such mussels were observed at this spot and the photographic evidence presented in this observation reflects the shell remains of several individuals. Similar such spots around the perimeter of the lake’s edge could be identified. Clearly, these mussels provide a food source for some of the multi-legged mammals and/or marsupials that generally tend to feed at night or in the early morning hours when Human activity at the park is reduced or non-existent. We think the identification is that of Eastern Elliptio (Elliptio complanata) based mostly in our observing similar posts made to iNaturalist recently by other North Texas-based iNatters and following up with our own research as per the sources cited below. Alas, we may be totally incorrect in our assessment given those range maps. Your assistance in confirming and/or correcting this IDentification is greatly appreciated. North Lakes Park is administered by the City of Denton, Texas.

Sources:

“Eastern elliptio (Elliptio complanata),” Maryland Department of Natural Resources, PDF information sheet on this species, July 2010, 1pp., photographs, description, range map, accessed 12.25.15, http://dnr2.maryland.gov/streams/Documents/elliptioComplanata.pdf

“Elliptio complanata, Eastern Elliptio,” NatureServe Explorer: An Online Encyclopedia of Life, description, range maps, resource links, accessed 12.25.15, http://explorer.natureserve.org/servlet/NatureServe?searchName=Elliptio+complanata

Lellis, William A., Barbara St. John White, Jeffrey C. Cole, Connie S. Johnson, Julie L. Devers, Ellen van Snik Gray, and Heather S. Galbraith (2013) Newly Documented Host Fishes for the Eastern Elliptio Mussel Elliptio complanata. Journal of Fish and Wildlife Management: June 2013, Vol. 4, No. 1, pp. 75-85. Accessed 12.25.15, http://www.fwspubs.org/doi/pdf/10.3996/102012-JFWM-094

Sizes