Dr. Rob Dillon, Coordinator





Wednesday, July 29, 2015

The Type Locality of Lymnaea emarginata


Editor’s Note.  This is the third installment of what I think will turn out to be a five-part series on the tangled species relationships of the American stagnicolines.  It’s not critical, but you might find it helpful to back up and read my essays of [22June15] and [14July15] before proceeding onward.

The next two North American stagnicoline lymnaeids to be called to the attention of science, after Lymnaeus catascopium, were L. emarginatus and L. elodes, both described by Thomas Say in 1821 [1, 2].  The figure below, clipped from Say’s “American Conchology”[3], compares the shell morphology of emarginatus (top row) to catascopium (bottom row).  Say wrote that emarginatus “is a somewhat larger, and considerably more ventricose species than L. catascopium, S., and the undulation of the columella is much more profound.”  Say gave the type locality of his emarginatus as “inhabits Lakes of Maine.”

So by great good fortune, in the spring of 2012 my wife won a pair of tickets on Southwest Airlines in a school raffle.  And she began to cast about for potential vacation spots during the first week of July, preferably someplace cool.  And she discovered that Southwest Airlines (if you can believe this) has service to Portland, Maine, from whence (she schemed) we might rent a car to Bar Harbor.  And just as simply as that, her husband had another field trip planned.  This one of a substantially different character than the expedition he detailed in his post of two weeks ago.

So we left our lovely B&B in Bar Harbor on the morning of 5July12, and by early afternoon I was collecting Lymnaea emarginata from Pushaw Lake, about 6-8 miles north of Bangor.  The snails were quite common on rocks in about two feet of water on the west shore of the lake.  It is well that freshwater malacology is not ordinarily so easy, lest everybody should do it.

I had actually done a bit of homework before setting off on this little errand, and so my choice of Pushaw Lake was not entirely arbitrary.  Our good friend Scott Martin reported emarginata populations from four counties in his (quite helpful) 1999 review, “Freshwater Snails (Mollusca: Gastropoda) of Maine [4].”  So I contacted Scott for his specific records, and among the many potential collection sites he forwarded to me was Pushaw Lake, from which Leroy Norton reported “Stagnicola oronoensis” in 1957.  Oronoensis is clearly a synonym of emarginata.

In retrospect, however, I wish I had done more homework than I did.  A closer reading of Scott’s 1999 review would have called my attention to a 1921 paper by O. O. Nylander [5] designating Mud Lake (in remote Aroostook County, 150 miles north of Bangor) as the type locality for Say’s Lymnaeus emarginatus, not Pushaw Lake.  Well, as the whole project turned out, it didn’t matter.

Rob at Pushaw Lake
And my efforts to collect a corresponding population of Lymnaea elodes were much more in keeping with my many years of personal experience in the matter of the pulmonate gastropod sampling.  Scott Martin actually listed six Maine counties for dark/skinny elodes-type stagnicoline populations, but his records were far more vague.  His best locality data were for a “Lymnaea palustris” population at the “Andrascoggin River above Rumford.”  And indeed, I found extensive, seasonal swamps along the right bank of the river in that area, absolutely primo habitat for mosquitos on July 5, but no sign of L. elodes.  The ANSP also holds a couple collections from the vicinity of Portland (Stroudwater and Westbrook) where I did no better.

Well, as the whole project turned out, it didn’t matter.  Oops, am I repeating myself in my old age?  This is a chord I have found myself striking with increasing frequency, as my perspective has matured, these latter years of my career.  What we do ain’t brain surgery, I often tell my students.  It’s just snails.

So I contacted Ms. Samantha Flowers [6] immediately upon my return to Charleston, and she was predictably pleased to hear about the bona fide emarginata population I had collected for her from a “Lake of Maine.”  She suggested that if I could ship the Pushaw emarginata to her alive at the University of Michigan Biological Field Station way up by Douglas Lake, she would be interested in attempting some breeding studies with dark/skinny populations of elodes and exilis from the Michigan area.  Which (of course) I was happy to do, out of my own pocket.

And with my July (2012) shipment to Samantha, I also included ethanol-preserved samples of four dark/skinny stagnicoline populations from NW Pennsylvania, which had been sent to me earlier that same the summer by Kip Brady and Andy Turner.  These were the “cryptic stagnicolines” I first mentioned in my essay of 10May12, and mentioned again last month.  Very mysterious, those populations…

…keep your eye on them!  And tune in next month, as we continue our quest to elucidate the tangled systematics of the enigmatic North American stagnicolines with “The type locality of Lymnaea elodes.”


Notes

[1]  Say, T. (1821)  Descriptions of Univalve Shells of the United States.  Journal of the Academy of Natural Sciences 2: 149 – 179.

[2] To be complete, it might be argued that Thomas Say described as many as five stagnicolines in the work cited above, including elongatus, reflexus, and desidiosus as well as emarginata and elodes.  Say realized that his nomen elongatus was preoccupied, and changed it to umbrosus himself in his "American Conchology" [3].  The identity of desidiosus as a stagnicoline (as opposed to a fossarine) is controversial – see the remarks of Baker (1911, pp 318 – 321).  I’m not sure what happened to reflexa.  The nomen was passed along by Baker (1911, 1928) as perfectly valid for dark, marsh-dwelling stagnicoline populations of very skinny shell morphology, but appears only as a “form” of elodes in Burch (1989).  I don’t know how it got so demoted.

[3] Say, T. (1830 – 1838ish) American Conchology; or, Descriptions of the Shells of North America.  New Harmony, Indiana, “Printed at the School Press.”

[4] Martin, S. M. (1999)  Freshwater Snails (Mollusca: Gastropoda) of Maine.  Northeastern Naturalist 6: 39 – 88.

[5] Nylander, O. O. (1921)  The type localities of Lymnaea emarginata Say and L. ampla Mighels.  Nautilus 34: 77-80.

[6] From this point to the conclusion of the essay, I am assuming that you are familiar with last month’s post,
  • Everything Changed When I Met Samantha [22June15]

Tuesday, July 14, 2015

The Type Locality of Lymnaea catascopium


Although not explicitly stated, it is traditional to assume that Thomas Say was referring to his home town of Philadelphia when he wrote, in 1817, “Inhabits the Delaware River and many other waters of the United States, in considerable numbers, and may be found plentifully, during the recess of the tide, about the small streams through which the marshy grounds are drained [1].”  Say was describing the habitat of the first “stagnicoline” lymnaeid, Lymnaea catascopium.  Standing on the Philadelphia waterfront in June of 2012, however, I found it nearly impossible to imagine how any self-respecting freshwater gastropod population of any description might ever have inhabited such a place.

Philadelphia 1702, from phillywatersheds.org
The Delaware is reliably fresh but quite tidal at Philadelphia, with a daily range of several feet.  So I gather that in the 18th and early 19th centuries, merchant ships anchored some distance offshore and transmitted their cargos over these "marshy grounds" at high tide by tender.  Then as the years advanced and the technology improved, the river must have been dredged and the fill material dumped directly onshore, creating more land, deepening the harbor, and allowing direct offloading of ships to finger-like cargo docks.  Whatever the historical scenario, however, by June of 2012 it was clear to this particular 21st-century malacologist that his efforts to sample a topotypic population of L. catascopium from the Delaware River must be re-directed upstream.

Philadelphia 1908, from phillywatersheds.org
The Academy of Natural Sciences holds one lot of L. catascopium collected by Charlie Wurtz from Pennypack Creek in 1948.  Pennypack Creek drains an entirely urban (actually, rather post-industrial) catchment inside the Philadelphia city limits, emptying into the Delaware just a few miles upstream from the docks.  And so it was to Pennypack Park that I set my GPS early in the morning of June 11, 2012.

I threw my kayak directly into the Delaware River and paddled upstream through the mouth of the creek into a zone of broad, intertidal mudflats decorated with a dense stand of arrowhead (Sagittaria).  The creek narrowed and deepened substantially as I paddled upstream, looking for the solid substrates I knew that populations of Lymnaea catascopium require.  Soon the air crackled with gunfire, as I passed alongside (perhaps “beneath” would be a better preposition) the Philadelphia Police Academy Firing Range.  After about a mile the creek had shallowed to the point I could get out and walk.

But I found no L. catascopium, nor indeed any habitat.  The steam bed was too muddy.  I found Littoridinops moderately common on floating debris, a few Physa acuta, N=1 Amnicola, and some beer-can limpets, but that was it.  So I paddled back downstream to the truck, loaded my kayak, and drove a couple miles upstream to the Verree Road Bridge.  Pennypack Creek was lovely at that point on a June afternoon, but flashy and low-nutrient, and simply not the kind of place one might expect L. catascopium.

Some nontrivial fraction of the early 19th century prosperity of Philadelphia was due to the network of canals communicating between the Delaware River and the interior of rapidly-expanding America.  In 1832 the Delaware Canal was completed to run 60 miles along the right (descending) bank of the river from Easton to the quaint old town of Bristol, PA, about 15 - 20 miles above Philadelphia.  And the Delaware and Raritan Canal was completed in 1834, connecting New Brunswick, NJ, to Bordentown, and climbing the left (descending) bank of the Delaware.  So on 12 June I checked the historic lock areas around Bristol, and also across the river at D & R Canal Lock #1, at Bordentown.  The latter spot was tough to access but afforded a pretty and diverse habitat with a disappointingly poor freshwater gastropod fauna.  The still-rather-strongly tidal environment is probably a factor.  Just a couple Physa acuta, and a Menetus or two, and I was gone.


The Delaware River passes through the fall zone at Washington Crossing, PA, famous primarily as the type locality of Physa ancillaria (Say, 1825).  Breeding results we published back in 2006 suggested that ancillaria is a fattish shell morph of Physa gyrina [2].  Most interestingly, some allozyme gels we ran in support of that research effort in 2005 returned evidence of low-frequency hybridization between P. gyrina and P. acuta at Washington Crossing – the only place (to this day) where the phenomenon has been documented.  You would think that at least a couple of the numerous historical markers one finds on both sides of the Delaware River at this point would feature such a remarkable finding.  But no.

Both Physa gyrina and P. acuta are common in the rocky pools at Washington Crossing, as they are upstream for several hundred miles.  The Delaware River is one of the few places where the two species are so richly sympatric, in my experience.  Also making an initial (or possibly final?) appearance at the fall line is Pleurocera virginica.  But no evidence of Lymnaea catascopium whatsoever.

The gastropod fauna continued to richen as I collected my way north upstream the next day.  The list lengthened to include Helisoma trivolvis, H. anceps, Gyraulus, Laevapex, both species of Ferrissia, Lyogyrus, and even (ultimately, way up north) Somatogyrus.  The most memorable snapshot from my June 13 field experience was the aquaviaduct at Tohickon Creek – a genuine marvel of 19th century engineering.  Here barges plying the Delaware Canal would have passed through a covered bridge (or trough, maybe a better noun) perpendicular to and 20 feet above the rocky creek below.  I passed through the Delaware Water Gap as the sun set on the third day of my efforts to collect L. catascopium from its type locality.

Tohickon Aqua-viaduct (PA DCNR)
I remember the morning of June 14, 2012 like it was yesterday.  The Delaware River at Milford Beach was low and clear.  Wading a bit over knee-deep on the left bank under some trees I pulled up a length of woody debris and attached thereupon I found N=2 pale lymnaeids about 10 mm shell length.  Juvenile catascopium!  The shell morphology reminded me of (slenderish) Lymnaea columella, which they might easily have been mistaken for, were they sitting on a lily pad in a pond rather than grazing on a stick two feet below the surface of a river.

I really needed a sample of at least 30 individuals to estimate allozyme frequencies.  So I redoubled my efforts in all similar habitats and substrates around Milford Beach over a period of about an hour.  But alas, no additional specimens came to light.  So I drove 25 miles upstream to Shohola Bridge, where two hours’ effort netted an additional N=5 juvenile catascopium.  Further upstream at Metamoras Boat Landing and Dillontown the river did not seem as rich, and I struck out.

Delaware Water Gap
So there I stood on the riverbank, as the sun set on June 14.  Five days and 1,375 miles on the odometer since I left Charleston had yielded the N=7 pale little lymnaeids crawling implacably about in the red, half-gallon thermos jug at my feet.  I’d be lying if I said I wasn’t disappointed.  But the AMS meeting was scheduled to start on Sunday (June 16) back down the river at Cherry Hill, and I still needed to find a population of Lymnaea elodes in the Delaware Valley someplace.  As I turned my pickup south, however, I felt good about at least one thing.  The Delaware River at Milford Beach, Pike County, PA is as close to topotypic for Lymnaea catascopium (Say 1817) as can humanly be located in the modern day.

If my efforts to collect a decent topotypic sample of L. catascopium were less than successful, however, my parallel efforts to find a matching population of L. elodes were an abject failure.  I had several leads.  In fact, the naturalist at Echo Hill Environmental Education Center near Lebanon, NJ, had sent me a sample of L. elodes for identification in December of 2010.  But I stomped all around in the wooded swamp where the specimens were collected, and couldn’t find so much as a shell.

I confess that I may not have been in the best of spirits at the AMS welcome mixer Sunday evening, when up walked our good friend Tom Duda, with a nice young lady in tow.  Tom introduced her as Ms. Samantha Flowers, a new graduate student at the University of Michigan [3].  And Samantha had chosen as her research project – if you can believe this – the evolutionary relationships among the stagnicoline lymnaeids.

Have you seen me?
She related to me, as the conversation unfolded, that she planned to use a variety of approaches, including molecular phylogenetics and geometric morphometrics, and sample as broad a range of catascopium, emarginata, elodes, and exilis populations as time and resources permitted.  I’m not crazy about gene trees, I thought to myself [4], but they do work with small sample sizes.  And what can I myself do with my crappy little sample of N=7 topotypic Lymnaea catescopium except go back up the Delaware again and try to find 23 more?

And such a nice young lady!  So bright, and so eager to learn!  In five minutes not only had I decided to give her my sample of topotypic L. catascopium, I had resolved to help her with the rest of her thesis in any way I could.

The next morning I transmitted my little sample of L. catascopium to Samantha, and told her she could keep my half-gallon thermos jug to carry them home in.  I also promised to her that I would continue to move forward on my original study design, and that I would try to send her additional samples as the summer progressed.  Looking back on it, I wasn’t entirely sure that she appreciated the potential for ecophenotypic plasticity in her chosen study organisms, or indeed that she actually understood the design of the study I (we?) were working on.

In fact, I was not entirely sure she understood the significance of the little sample of snails I handed her that morning.  Thomas Say’s (1817) nomen “Lymnaea catascopium” is the oldest available name for any of the North American stagnicolines.  Which means that regardless of all the other names invented by all the other malacologists to name all the other stagnicoline populations in all the other regions of the United States and Canada, any population matching those N=7 crappy little snails in that red jug must be Lymnaea catascopium by definition.  They were her control.  Every other sample she might acquire would be an experiment.

With the benefit of three years’ hindsight, I think that it was probably too early in Samantha’s professional career for her to take this all in.  But stay tuned!  Coming up next month - the type localities of L. elodes and L. emarginata.

Notes

[1] Lymnaea catascopium was one of a long list of species that Thomas Say described in the entry entitled, “Conchology,” which he contributed to Nicholson’s British Encyclopedia of Arts and SciencesNicholson’s Encyclopedia was published at Philadelphia in three editions: 1816, 1818, and 1819.  I gather that these works are very rare in libraries today.  And I also gather that the "1816 Edition" was actually published in 1817.  I myself only have access to W. G. Binny’s (1858) secondary reference entitled, “Complete Writings of Thomas Say on the Conchology of the United States.”  And Binny only reprints the third (1819) edition.  So that’s where I got the quote above.

[2] Dillon, R. T., and A. R. Wethington. (2006)   No-choice mating experiments among six nominal taxa of the subgenus Physella (Basommatophora: Physidae).  Heldia 6: 41 - 50.  [PDF]

[3] From this point onward in the present essay, I am assuming that you have read last month’s post,
  • Everything Changed When I Met Samantha [22June15]
[4] This is a long-running theme on the FWGNA blog, for example:
  • Gene Trees and Species Trees [15July08]