Reclaiming Fame: A query into the unsung glory of trematode taxonomy

The following post was written by University of Queensland parasitology student, Xena Brooks. She is currently competing in the Thinkable campaign for the 2016 QLD Women in STEM competition. You can help support her by going to the link and voting for her to win the people’s choice award. The proceeds from the prize, if she wins, will go towards her research.

It’s an appealing idea to set off to see the world and discover new things. It’s romantic to stare at the moon and speculate on the mysteries of the universe. It’s honourable to look out, hoping to discover something new. But, we (society at large) have not got the same feeling towards parasite studies. With a wealth of diversity yet to be discovered or understood, I wonder: why is trematode taxonomy so lacking in appeal?

The first family to be recognized was Diplostomidae by Poirier in 1886, which is formally written as Diplostomidae Poirier, 1886. Poirier’s discovery unleashed a surge of taxonomic activity so intense that by 1906, fourty families had been proposed. This excitement continued and by 1926, more than half of the existing families had been discovered. The rest of the 21^st century allowed those ‘adventurers’ in the field of marine parasite taxonomy to shine: between 1933 and 1971, Yamaguti proposed 182 genera, between 1925 and 1972, Manter proposed 62 genera, and Cribb, still active, has proposed 50 genera since 1985.

In 2011, Thomas Cribb and Rod Bray assessed the literature on each trematode family. These authors, both prolific researchers themselves, found that since 1926, there has been a steady decline in the rate of discovery of trematode families. The decline has been so steep that Cribb and Bray refer to the lack of scientists researching taxonomy as a “global crisis” (2011). The old guard is stepping back and the new wave is less populated and less funded.

A perfect example of the potential for discovery is in the Western Indian Ocean, which is arguably the least studied area in the tropics for trematode diversity. Despite having 2,000 fish species on record, we only know of 87 trematode species. The better-studied waters of Hawaii have half the fish diversity, but three times as many recorded trematode species. Of the Western Indian Ocean’s 87 samples, 70 were collected prior to 1980 (80%) and not much research is happening in the region today. It seems the heyday of parasite discovery is over, not for lack of undiscovered species, but for lack of effort.

Each day, species are disappearing and biologists and ecologists lament the biodiversity crises that industrialization and environmental abuse have brought about. As fish species disappear, untold trematode richness does as well and we will never know what lay in their little fish hearts. We cannot preserve what we don’t know exists.

Why is that the human quest for discovery has glossed over the oh-so-exciting field of marine parasite? Partially, it is because of political instability or lack of funding in developing areas; but it is also because parasite taxonomy lacks the appeal. It doesn’t seem relevant or modern to sift through fish guts looking for a small, most likely white, worm. So as an early career researcher in this area, am I wasting my time?

Luckily for me, the worms are already making themselves relevant. Take the tuna industry, for example:

In 1996, tuna mortality, attributed with tow conditions, nutrition and stocking densities, peaked at 7%. This caused a review of the husbandry practices and by 2002, mortality had been reduced to only 2% and South Australia breathed a sigh of relief. As ranchers sat back to enjoy the ~$600 per fish that came rolling in, the death toll steadily increased. By 2008, mortality was back up to 7%.

The culprits? A dynamic duo of ‘sea lice’ parasitic copepods (Caligus) and an aporocotylid blood fluke (Cardicola fosteri).

Two years later and the life cycle was cracked, with terebellid polychaetes proving to be the missing link. By moving cages further offshore and away from infected marine worms, the problem was solved and everyone involved was very pleased with themselves.

But, what if we didn’t need to call in the taxonomic super heroes? What if research was done preventatively rather than post-disastrously? As aquaculture expands, there will be so many unknowns. If we could invest in trematode studies now, perhaps aquaculture waste can be reduced before it even begins. Perhaps it is time for a renaissance of the old fashioned art of dissection, drawing, and describing the morphological traits, with a bit of molecular analysis thrown in for good measure.

If you would like to help my research, please click the link below and vote for my video. It is part of an initiative by the Queensland government to promote women in STEM and I would love to get some funding so I can afford the genetic component of my project.

http://www.thinkable.org/submission_entries/OxlvKmkn

Thank you so much, Xena Brooks.

Note: The image at the top of the page is of a transected heart taken from Siganus fuscescens that displays a parasitic infection inside of it.

Edited by Christopher Haggarty-Weir