Oregon, bulimoides, or bust

Editor's Note – Exactly one year ago, on [13Feb24], I posted an essay in the columns of this blog asking the question, “What is Lymnaea bulimoides?”  And I concluded that essay, “Malacologists of America, we must do better.”  Here is my effort.

L. bulimoides Gahr Pond

Thomas Nuttall (1786 – 1859) was a man of distinction [1].  He was among the first naturalists to explore Arkansas, among the first to botanize California, and the author of the first field guide to the North American birds.  The breadth and depth of his experience with the natural history of temperate America was unequalled in his day, arguably since.  And of the 400,000 pioneers who travelled the Oregon Trail west from its opening in the early 1810s through its heyday in the 1840s – 1860s, Thomas Nuttall was one of the very, very few who ever came back east again.

And packed deep in the luggage he carried with him aboard the merchant brig Alert in 1836 [2], bound from Monterey to Boston with a cargo of cowhides, was the world’s first sample of crappy little amphibious lymnaeids that Isaac Lea [3] ultimately described as Lymnaea bulimoides [4].  And as my wife and I boarded Delta Flight 954 for Portland on the morning of July 31, 2024, in that one tiny distinction, I meant to join him.

 

Never has a freshwater gastropod subsequently so important been subsequently so widely misunderstood.  Lymnaea (Galba) bulimoides is the primary intermediate host of Fasciola hepatica – the livestock liver fluke – in the Pacific Northwest.

Fasciola is a digenetic trematode, which means that it has two hosts, a primary host, typically hooved livestock [5], and an intermediate host, typically a lymnaeid snail.  The worm infects the liver of its primary host, laying eggs which are defecated.  Those eggs hatch into swimming miracidium larvae which find a snail, burrow in, and develop into rediae, which in turn shed swimming cercaria larvae. 

 

In all of those details, Fasciola is no different from the better known fluke Schistosoma.  But unlike Schistosoma, the cercariae do not burrow into the skin of their primary hosts but rather encyst on grasses and vegetation.  And the cysts must be eaten by the primary host to complete the life cycle.

Life cycle of Fasciola [6]

So, from the standpoint of the fluke, the best environment would be a pasture cycling wet to dry, inhabited by an amphibious lymnaeid that might be exposed to swimming miracidia and shed swimming cercariae during the wet season, then drying so that the cysts might be grazed over by livestock.  Remember that.  That will be a key to understanding the remainder of this essay, and next month’s as well.

 

Liver flukes are a problem for the livestock industry [5] on six continents, and significant research efforts have been directed toward understanding the crappy little amphibious lymnaeids that host them worldwide for many years [7].  Except in the Pacific Northwest.  Where there is not a worker in the field today – not malacologist, nor parasitologist, nor veterinarian, nor guardian of the public health – who could identify a bona fide Lymnaea (Galba) bulimoides if it bit him on the boot toe.  Or at least, that was my hypothesis, as I boarded Delta Flight 954.

 

My library and museum research over several years previous had revealed to me what appeared to be repeated and systematic confusion between Lymnaea (Galba) bulimoides and Lymnaea (Galba) cubensis/viator, a similarly small, similarly amphibious, similarly susceptible lymnaeid much more widely distributed across The Americas, North and South [8].  That confusion seemed to have its origins in the late 19th century, redoubling in the early 20th, with the description of Lymnaea (Galba)  cockerelli, a third distinct biological species sometimes co-occurring with bulimoides in mixed populations [9].

 

I became convinced of a widespread, systematic, three-way confusion in early 2024 but had no evidence to support it, much less solve the problem.  To test that hypothesis, I needed a control, and none was to be had.  Thomas Nuttall’s original sample, surviving the perilous voyage around The Horn with their collector, was described by Isaac Lea as simply coming from “Hab. Oregon.”  In 1841, “Oregon” included all or part of five U.S. States, and much of British Columbia.

 

So, the first step out of the darkness, it seemed to me as I settled into my narrow seat early that July morning, would be to restrict the type locality of Lymnaea bulimoides to some more precise spot.  And then to sample and characterize the population of crappy little, amphibious lymnaeids inhabiting that spot as a standard, against which all other populations of lymnaeids might be compared.

The ideal type locality should be well-characterized, accessible, and protected.  Thus, folded in my shirt pocket that morning was a map of Oregon I had printed off line with a pin dropped on 44.5229, -123.3377, a drainage ditch by Bellfountain Road about 8 km SW of Corvallis where, as best I could figure, one Greg R. Foster had conducted the only decent studies of the biology of L. bulimoides ever published in the scientific literature, way back in 1969.  More about those studies [10] next month.

 

And there were other pins dropped on my map as well.  In addition to establishing a type locality, I very much wanted to find at least two additional populations of bona fide L. bulimoides to get some feel for intraspecific variation – one north of Corvallis, and one south.  For the former, I had researched online quite a few museum collections of apparently bona fide L. bulimoides in the Portland area, perhaps 70 miles north of Corvallis. And I had also marked the bowl of a rolling hayfield in a lovely and remote corner of Yamhill County about 40 miles north of Corvallis, locality courtesy of Ms. Courtney Hendrickson of Oregon State University, and the hero of our story, Mr. William (Bill) Gerth.

 

Bill is a senior faculty research assistant in the OSU Department of Fisheries, Wildlife, and Conservation Sciences in Corvallis, and a longtime friend of the FWGNA Project.  I could not name a cheerier or more enthusiastic colleague.  I had emailed Bill several days before flying off to Oregon, just to touch base, and he replied almost immediately with a gang of students and coworkers on the CC line all interested and eager to help.

 

And attached to his email was the jpeg that opened this essay, depicting a nice individual L. bulimoides collected by Ms. Hendrickson from a seasonal pond in a hayfield on the Gahr Farm property in Yamhill County. The itinerary I had outlined for myself and my lovely wife Shary, as we retrieved our luggage in the Portland airport and headed for the rental cars that hot July morning, was an ambitious one.

We drove north over the Columbia River that very afternoon, and into the state of Washington.  And my first noteworthy observation was made while still battling the urban sprawl of Vancouver: a population of very ordinary-looking Lymnaea (Galba) humilis inhabiting the muddy margins of a retention pond across Mill Plain Blvd from the Walmart (A).  I don’t suppose I was terribly surprised.  Those things are the Physa acuta of the Lymnaeidae.  But it was interesting to see our old friend humilis here in the Pacific Northwest, making cozy with the much more mysterious bulimoides I hoped to find, and the cubensis I rather hoped I would not.

 

The environment turned more propitious at Grass Valley Slough (B), but here we encountered the problem that would bedevil us for the remainder of our sojourn in the Pacific Northwest.  The slough was bone dry, baked hard as a rock.  I was most impressed by the dramatic accumulation of bleached Physa gyrina shells in the brittle mud at the culvert under Bybee Road, but finding no evidence of lymnaeid remains among them, neither shell nor meat, moved on.

 

Further north the topography evolved into rolling hills, the drainage improved, and scattered forest appeared.  And at point (C) I made an observation that forever changed my life [11].  Juga in a ditch.  This was a little roadside ditch, not three feet across, choked with grass, a place one would never expect to find a prosobranch gastropod of any sort back East, ever [12].  Yet Juga [14] does.  There simply is no substitute for field experience if one wants to understand the biology of a study organism, or indeed an entire Linnaean Family of study organisms, and I was once again reminded, harshly, that in the Pacific Northwest, I had none.

 At Battleground Lake (D) we reached the foothills of the Cascades, and finding the poorly drained fields and open pasturelands that best serve as habitat for the elusive L. bulimoides essentially gone, and the light failing, reversed our course for Portland, disappointed.  Tomorrow, I hoped, conditions might be more favorable.

Shary at Baker Cabin

The next morning we set our course east along the left bank of the Columbia River, swooping wide around the eastern suburbs of Portland toward the Willamette River valley to the south.  The freshwater gastropod fauna was gratifyingly diverse in the sloughs along the south bank of the big river (E), that of Kelly Creek (F) and several other sites in the Sandy and Clackamas River Valleys (G), rather less so [16].  My goodness, the day was turning hot.

 

All of the sites we visited that morning, and into the early afternoon, included some exposed mud bank, which would have been fine habitat for crappy little amphibious lymnaeids in The East but seemed devoid of molluscan life here in the environs of Portland.  We ran into the Oregon Trail at the historic Baker Cabin (H) and followed the trail down to its terminus at Oregon City (I).

 

Well, to be technical, Oregon City was the terminus of the Barlow Road section, a passage through The Cascades that did not open until 1846.  Thomas Nuttall pioneered the newly opening trail in 1834.  In those days the only route to Oregon was down the Columbia River, through the treacherous rapids at The Dalles.

 

My wife and I, on the other hand, opted to take I-205 and OR-18 south through the rich agricultural landscape of Yamhill County, now dry and brown in the August sun. The rotating sign in front of the bank was reading 103 degrees at 4:20 in the afternoon, when we passed through McMinnville on our way west toward Gahr Farm (J).

Bill’s colleague Courtney had thoughtfully alerted the landowner to expect visitors that afternoon and sent me a link to a map with a suggestion on a parking spot, as well as the precise coordinates [17] where she had collected N = 2 L. bulimoides in the spring of 2023, some 400 meters south through Farmer Gahr’s stubbly hayfield.  She added somewhat cryptically, however, “Just a heads up that the ponds can be a little tricky to find.”

 

My standard wardrobe for fieldwork is built on a foundation of hip boots over blue jeans, at least as much to protect my legs stomping though underbrush on my way to the creek as to protect my piggies upon arrival.  But the sun beat so mercilessly on Farmer Gahr’s fallow fields late that afternoon I changed into shorts and water shoes by  the desolate roadside, willing to pay the cost of few degrees of cooling in blood from my ankles.  And off I stomped toward an island of cattails flickering in the distance.

Alas, dry-rooted cattails were the only evidence that any pond had ever existed in the rolling hills of the Gahr Farm on August 1, 2024.  I staggered, dazed, from patch to patch, beating down through the willows to the Muddy Creek ditch, finding not puddle, nor pebble, nor polliwog.  The singleton bleached shell of Physa gyrina I ultimately recovered, in over an hour of pawing through brittle cane and cattail root, felt like a trophy.

Gahr Farm, 1Aug25

As I trudged back to our rental car, where my wife sweltered in the late afternoon sun [18], singleton Physa rattling dry in a vial in my chest pocket, I found myself meditating on the mantra, “Malacology in The West is different.”  And as the sun set on that exceptionally long, exceptionally hot day, southbound on OR-99W with Corvallis lit green on our GPS, a question crystallized.  Might any better fortune await me in Greg R. Foster’s ditch on the morrow?  Tune in next time.

Notes

 

[1] Most of the biographical information that opened this post came from:

• Nelson, John R. (2015) Thomas Nuttall: Pioneering Naturalist (1786 – 1859).  Bird Observer 43: Article 2.

[2] By remarkable coincidence, Richard Henry Dana was serving as an ordinary sailor on this very voyage, later to record the adventure in his famous memoir, “Two Years Before the Mast.”

 

[3] For a brief bio of “The Nestor of American Naturalists,” see:

• Isaac Lea Drives Me Nuts [5Nov19]

[4] Lea initially described Lymnaea bulimoides in brief Latinate form in 1841, with more complete English description in 1844:

• Lea, I (1841) On fresh water and land shells (continued).  Proceedings of the American Philosophical Society 2(17): 30 – 34.
• Lea, I. (1844/46) Continuation of Mr. Lea’s paper on fresh water and land shells.  Transactions of the American Philosophical Society 9(1): 1 – 31.

[5] Human cases of fascioliasis are becoming more common, according to the WHO website on neglected tropical diseases.  Transmission is apparently by ingestion of watercress or mint, although “encysted larvae may be found on other salad vegetables.”

 

[6] From the U.K. National Animal Disease Information Service [Nadis.org.uk]

 

[7] My sheaf of research papers on Galba worldwide fills an entire drawer of my filing cabinet.  For an opening into the vast literature, you might start with:

• The Lymnaeidae 2012: Fossarine Football [7Aug12]
• The American Galba and The French Connection [7June21]
• Exactly 3ish American Galba [6July21]
• What Lymnaea (Galba) schirazensis is not, might be, and most certainly is [3Aug21]

[8] For a review of the bulimoides/cubensis confusion, see:

• What is Lymnaea bulimoides? [13Feb24]

[9] For a review of the bulimoides/cockerelli confusion, see:

• Lymnaea (Galba) cockerelli, Number 15. [12Mar24]

[10] Greg R. Foster’s contributions:

• Foster, G.R. (1971)  Winter vagility of the aquatic snail Lymnaea (Galba) bulimoides Lea.  Basteria 35: 63 – 72.
• Foster, G.R. (1973) Soil type and habitat of the aquatic snail Lymnaea (Galba) bulimoides Lea during the dry season Basteria 37: 41 – 46.

[11] No, not really.  I’m straining to create some sort of drama out of parking by a weedy ditch in a rented Acura.  Work with me here.

 

[12] Well OK, the water was cool, and there was a little bit of current.  Melanoides populations can reach great densities in such ditches down in Florida [13].  But the point I’m trying to make is that pleurocerid gastropods do not live in such environments, under any circumstance, period.

 

[13] And Pomacea too, if you want to quibble.  Ditches are different in Florida.  See halfway through my essay:

• The Mystery Snail Color Genetics Project [6June23]

[14] I would have identified this population as Juga hemphilli, but opening the 2022 revision by Strong and colleagues [15] it appears that hemphilli has been synonymized under Juga plicifera.  I really need to dig into that paper.  Perhaps in a future post.

 

[15] Strong, Ellen E., J.T. Garner, P.D. Johnson, and N. V. Whelan (2022) A systematic revision of the genus Juga from fresh waters of the Pacific Northwest, USA (Cerithioidea, Semisulcospiridae).  European Journal of Taxonomy 848: 1 – 97.

 

[16] In the Columbia Slough Natural Area (E) I recorded Cipangopaludina chinensis, Physa acuta, Helisoma trivolvis, Lymnaea auricularia, and Gyraulus parvus.  At Kelly Ck (F) just Physa acuta.  At the Clackamas River (G) I recorded Juga plicifera, Fluminicola virens, and Physa acuta.

 

[17]  045.1666690, -123.3129760, to be quite precise.

 

[18] Throughout the day, my long-suffering wife had been chauffeuring me around NW Oregon like a poodle and patiently waiting for me in the car, reading a book, with the motor running and the AC on.  At some point during my lengthy explorations at the Gahr Farm, a public-spirited citizen stopped to warn her about the hazards of parking a car at idle over a grass stubblefield as dry as Farmer Gahr’s.  She cut the engine immediately, of course.  But was a bit on the cranky side when I eventually returned.