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TWiP 61 letters

Ian writes:

Dear TWiPers,

I just finished listening to the superb Twip #56 and I am thrilled because I am a huge fish nerd. In fact I spent much of my youth catching and chasing fish on the same lovely New Jersey barrier island mentioned in that episode. In my enthusiasm, I wanted to write in with a few thoughts.

The first is nit-picking, but the gar discussed around the 13:00 minute mark is more likely a specimen of Atlantic Needlefish, Strongylura marina, than a member of the “true gar” family Lepisosteidae. Like members of Lepisosteidae, needlefish have elongated, tubular body plans, and are sometimes referred to in common usage as gar. Needlefish often spend time at the surface, but do not gulp air in the cool way fish such as the Florida Gar do. This mix-up might explain Dickson’s surprise at hearing about gar so far north.

As an aside, I might add that I have heard that --if presented with a fly small enough to fit in their diminutive mouth--needlefish make for wonderful sport fish. I myself have caught a needlefish on Barnegat Bay, although not in the manner one might think. I spend my free time sailing a catamaran around the bay. On one windy day I had the rude surprise of a large needlefish jumping out of the water and landing in my boat! My crew and I were as shocked as the fish! It was a memorable experience; particularly because, like many angry fish, the needlefish displayed a heightened, more vibrant coloration than I usually get to see. The fish was promptly returned to the water and I was left relieved that I hadn’t been added to the list of people who have been impaled by needlefish (

In the spirit of “This Week in Fish” I would like to suggest “The Founding Fish” by John McPhee as a pick of the week. The book is a wonderful examination of everything Shad, written by a wonderfully gifted writer. I’m picking it because Twip #56 included a question about shad’s tastiness. As the book points out, the species name of the American Shad, Alosa sapidissima translates to “most delicious”. I am salivating just thinking about a meal of baked shad, perhaps with a side of Atlantic blue crab, whose species name also derives from sapidus the Latin word for savory.

As always, much thanks for all the work that goes into the TWiX podcasts. I am about to leave on a road trip across the US in order to start grad school for biology, and I am looking forward to having tales of viruses, microbes, and parasites keep me company along the way.



Howell writes:

Dear Professors,

First of all, thank you for producing such fascinating podcasts! I got interested in parasites when I read Carl Zimmer's book - I've just discovered TWiP, through Professor Racaniello's course on Coursera, and I intend to try and listen to them all!

I've just got one question so far: is the cover photo for the page of Trichinella?


Andy writes:

Dr. Despommier,

I enjoy your show although parasites are not related in any way to what I do for a living.

You have mentioned the death of the S. A. Andrée's Arctic Balloon Expedition of 1897 crew in a couple of TWIPs including in episode 60 and how they probably died of Trichinosis from eating polar bear.'s_Arctic_Balloon_Expedition_of_1897

I was fascinated by this and repeated it a couple of times to friends, but when I was looking for details I came across this entry in Wikipedia which says this theory was "discredited in 2010." The cited links are in Swedish and one appears to be broken at this time. The other one is very brief but using google translate it says they think it was polar bears instead. Obviously anyone can put whatever they want on the internet, but I wonder what your thoughts are on this?


Tommy writes:

Dear Vincent and Dickson,

Just a note about something that Dickson mentioned in TWiP 60, I am sure Dickson realised that he simply misspoke after it went on air, but the digenean responsible for the "Barber Pole Effect" - Leucochloridium paradoxum - is not a schistosome but belongs to the Leucochloriidae family which is on an entirely different branch of the digenean/fluke tree to the schistomes.

There are many different species of Leucochloridium and they come in different colours. For example Leucochloridium paradoxum have green bands or red-brown bands on its sporocyst brood sac (the structure which invades the tentacles of the infected snail) whereas Leucochloridium millsi has yellow or orange-yellow bands. A good paper on this topic can be found below.

Kagan, I. G. (1951). Aspects in the life history of Neoleucochloridium problematicum (Magath, 1920) new comb. and Leucochloridium cyanocittae McIntosh, 1932 (Trematoda: Brachylaemidae). Transactions of the American Microscopical Society, 70(4), 281-318.

Additionally, there is some indication that the behaviour of the snail is altered, as noted by Carl Wesenberg-Lund in this paper below.

Wesenburg-Lund, C. (1931). Contributions to the development of the Trematoda Digenea. I. The biology of  Leucochloridium paradoxum. Memoires de l'Academie Royale des Sciences et des Lettres de Danemark, Copenhague, section des sciences 4, 90-142.

It was cited in Janice Moore's 2002 book "Parasites and the behaviour of animals". Wesenburg-Lund noted that "It seems as if the infested snail seek the light; they are very often see balancing on the borders of the leaves, or sitting on the underside of the leaves with only the antenna infested with the Leucochloridium protruding from the border
of the leaves..."

Now compare this with the behaviour of most terrestrial snails which prefer more damp and secluded surrounding. Such altered behaviour would expose the snail (and it brightly coloured parasite) to predation by the potential bird host.

As a side note, here is a link to a cartoon I drew about Leucochloridium a few years ago
It contains a pop culture reference, which might not be obvious to everyone, though most people below a certain age would immediately recognise it. For the listener who cannot see the imagine, it is a reference to the 2003 song "Milkshake" by Kelis.

Keep up the good work Vincent and Dickson, I look forward to more parasite tales from you in the future.

Robin writes:

Toxoplasmic humans

'Tain't just mice that have adverse behavioural outcomes with Toxoplasma.

Should humans attacked or killed by big cats be checked for Toxoplasmosis?

Suzanne writes:

Thank you for the Bt and mosquito info. I had a feeling there had to be a catch. Since there's always plenty of other water that isn't treated I expect Bt wouldn't become completely useless but it's good to know it's not a wonder fix, either. Ah, well.


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