Where are they?
Félix Mesnil (at right)was a prominent parasitologist - one of the three founders of the Société de Pathologie Exotique and its President from 1924 to 1928. Félix was born in 1868 in Omonville-la-Petite, a coastal town of the Cotentin, at the tip of the Cape de la Hague, a place that would prove significant later in life for the dsicovery of the Haplosporidia. Following his education in France and central Europe, Louis Pasteur admitted him as an agrégé demonstrator to the Institute rue Dutot. However, he would, each year, vacation at his house in the cove of
Saint-Martin (L'anse Saint Martin) and would busy himself with his fascination for the marine invertebrate fauna there. For more than thirty years, Mesnil made contributions not only to protistan parasite biology, but also to the taxonomy and systematics of polychaetes and molluscs of the Normandy coast. Though perhaps at first the attentiveness of his brother-in-law, Maurice Caullery, may have been a distraction, this eventually gave over to an affectionate and productive collaboration between the two.
In 1898, these two brothers-in-law found the first haplosporidans. A group of protists entirely new to science and so unique from anything else seen before or since that they deserved their own phylum. With Caullery, the noted marine worm biologist, as the first author, it is reasonable to conclude that he had stumbled across these strange organisms while routinely examining a polychaete (Scoloplos armiger). Even without the aid of scanning electron microscopy, their drawings of the tiny spores remain detailed and useful a century or more later, and their frustration is palpable in reading the published work. In many hundreds of worms examined they found precious few of this Haplosporidium scolopli. For Caullery and Mesnil, this discovery was probably little more than yet-another curiosity in their summers together pouring over critters... they had no idea how important it would prove to be some 60 years later and well into the next millenium. Mesnil's career would soon turn to malaria, African sleeping sickness, kala azar (leishmaniasis) and the demands of international recognition.
In 1996, and then on the centennial (1998) of the first discovery of haplosporidians, Eugene Burreson and Mark Siddall returned to L'anse Saint Martin. Their goal was to rediscover H. scolopli and Urosporidium fuliginosum at the same locality that Caullery and Mesnil had first found them. Notwithstanding two intensive expeditions, and the commensurate demise of thousands of polychaetes, no sign of these parasites remain there. It is possible that these parasites are now extinct - the region has been heavily influenced by the effects of WW-II as well as a massive plutonium generating station on the Cap. However, in light of the low prevalence seen by Caullery and Mesnil, it may well be that L'anse Saint Martin is only at the perifery of the range for these parasites. Minchinia chitonis described originally from Britain, for example, has a much higher prevalence at St. Malo in Brittany.
It is now well understood that haplosporidians have a global distribution. Most of these parasites are in marine invertebrates, but there are freshwater taxa as well. So far, taxa are known from the Atlantic coast of North America, the Carribean, European coastlines, Japan, Korea, California, Australia, and the Mediterraean. None are yet described from South America or Africa, but we are reasonably sure time will prove ootherwise.