26 May 2008


As explained in yesterday's post, I have written the introductory paragraphs for 2 North American land snail families to be included in a workbook being prepared for the terrestrial gastropods workshop during the upcoming AMS meeting in Carbondale, Illinois.

I posted what I had written for the Discidae in yesterday's post. Here is what I wrote for the Punctidae.

Punctum is a Holarctic genus. The North American Punctum species are among our smallest land snails. In fact, P. smithi, whose adult shell diameters barely reach ~1.2 mm, is one of the smallest land snails in the world. Punctum are primarily woodland snails that are widespread throughout North America. The range of P. conspectum extends to Alaska. Although Punctum specimens may, on occasion, be abundant in litter samples, because of their diminutive sizes, however, live Punctum are difficult to observe and study in the wild. Consequently, virtually nothing is known about the natural histories of individual species. The European P. pygmaeum is known to be able to reproduce without mating in captivity. The anatomies of most North American Punctum species have also not been studied.

Paralaoma caputspinulae (also known as P. servilis) is known from a few disjunct locations in western North America. It is probably a non-native species.
Any errors and significant omissions of information will be corrected before the final version goes in the workbook.

Punctum smithi was pictured in this post.


Chris Austin-Lane said...

Hey, I live in Maryland, and my daughter and I have been wondering what kind of snails we have gathered (and thence been breeding) from the Potomac. I had assumed that they were some native snail, but in searching for the kind of snail, I found about about a lot of invasive snails, so now I'm more curious. If I posted a few pictures of the snails, could I ask you to have a quick go at identifying them? We find them covering underwater plants and sandy bottoms in the section north of Great Falls. They are small, but I won't attempt to describe them with words.

Nice blog. I am glad that some of our fellow walkers on the tow path are so well informed.


PS I hope you enjoy the book by Dogen - I've been slogging through the Shobogenzo translated by Cross and Nishijima. It's very funny and inspriring once I figure out what the heck is going on (sort of like Ulysses).


Chris, I'll be glad to take a look at the pictures of your snails. But I may not be identify them, because I don't know much about freshwater snails. I work mostly with terrestrial snails.

Anonymous said...

Paralaoma servilis is indeed an alien in North America (and Europe, and South America, the Pacific islands, and no doubt elsewhere). It is native to New Zealand; Fred Brooks has published several papers documenting its presence there in the Pleistocene, well before humans started carrying it around with them. It is the second Kiwi snail (along with Potamopyrgus antipodarum) that is out to conquer the world.

Carl Christensen

Kevin Bonham said...

Paralaoma servilis/caputspinulae is also present through most of south-eastern Australia and treated as "native" here. But I have doubts about that. Certainly here in Tasmania the species (which is very common and widely recorded) has a distinctly "trashy" ecology and distribution. Unlike every other purported Tasmanian terrestrial native, it is extremely successful in suburban parks and gardens (including mine). When it occurs in bushland areas, it tends to occur in those that are disturbed, especially those close to farmland and/or settlement. In the larger Hobart area bushland reserves, it is common around the disturbed edges then more or less absent from the less disturbed interiors, more or less irrespective of habitat type.

There are not many records from less disturbed areas and it's possible that a small minority of those are actually as-yet-unrecognised natives that look similar (indeed the amount of "variation" is suspicious). Since separating out records of some other common punctid species that had been wrongly lumped under "caputspinulae", I've increasingly suspected that what's left over includes a large proportion of exotic stock. Of course what I've seen is also vaguely consistent with it being a disturbance-promoted "tramp" type of native species (and I get a few inverts that fit that bill in my backyard too!)

I would love to hear more about any other evidence of the species behaving like an exotic elsewhere, or about evidence of it being originally not just native to but endemic to NZ. Also, I'd be interested to hear how it responds to urbanisation in NZ.

Kevin Bonham

PS On the taxonomy, I know servilis is the earlier name, but has an established usage claim ever been investigated (and if not, would one have any chance to succeed?) Not that I am personally in any hurry to rescue "caputspinulae" from taxonomic oblivion; it's a very colourful name but I'm sick of the effort of typing it!

Anonymous said...

The most thorough discussion I've seen of the taxonomic history of P. servilis/caputspinulae is in Falkner, Ripken, & Falkner (2002), Mollusques Continentaux de France. Like a lot of widely transported species, it has picked up synonyms all over the world. My guess would be that it's not native to Australia and is in fact an NZ endemic, but since the known fossil record of tropical land snails is so scanty (and proving a negative is tough in any event) it's hard to say more than that it IS native to NZ.

Carl Christensen

Anonymous said...

Correction to my last: P. servilis may be native to Australia as well. See G. J. Price and G. E. Webb. 2006. Late Pleistocene sedimentology, taphonomy and megafauna extinction on the Darling Downs, southeastern Queensland. Australian Journal of Earth Sciences 53: 947-970, esp. Table 7 on p. 958 (as Paralaoma caputspinulae).

Carl Christensen

Kevin Bonham said...

Thanks very much for the references Carl. (I'm aware that the Falkner et al work is the source of the demonstration that servilis has priority, but haven't tracked it down yet.) I couldn't find any detail on the source of the land snail identifications in the Price and Webb paper so I'm treating that one with just a little degree of caution, given the long history of unrelated punctids being lumped under caputspinulae in Australia.

I came across Stanisic, J, R.A.D. Cameron, B.M. Pokryszko and J.C. Nekola. 2007. Forest snail faunas from S.E. Queensland and N.E. New South Wales (Australia): Patterns of local and regional richness and differentiation. Malacologia. 49:445-462. The authors indicate the beast in question as an introduced species in the Kempsey region in northern New South Wales (which is not too far from southeastern Queensland) but don't say why.

I shall investigate. :)

Kevin Bonham said...

Update on this mainly for the benefit of anyone who finds it via Google: I am now looking at the Tasmanian populations of "caputspinulae"-like specimens as comprising at least two species - one exotic (P. servilis), one native (P. hobarti (Cox 1868)). Somewhat more localities for the native species but higher average specimen numbers for the exotic, which is mostly present in urban gardens, coastal areas, farmland and other disturbed places and some mostly near-urban bushland.