Fish Beware – A New Species of Parasite is Discovered

Drawing of  Lethacotyle vera.

Drawing of Lethacotyle vera.

The world is full of creepy crawlers; some are harmless bugs while others are blood sucking parasites. Adding to the list of parasites this month is one identified in a recent PLOS ONE article, Lethacotyle vera n. sp, a new species of fish parasite, found in the South Pacific. Lethacotyle vera is part of the class Polyopisthocotylean monogenean, which are tiny (less than 1-cm long), parasitic flatworms that live on fish gills.

For any type of ectoparasite (parasites that live outside their host’s body) staying attached to their host is an important ability. One of the most notable features of Polyopisthocotylea is their multiple sucking clamps that allow them to keep their position on the fish. These clamps are found on the haptor, a body part developed specifically for attaching. Some parasites in this group can have hundreds of clamps as part of their haptor. In fact, Polyopisthocotylea literally translates to ‘many sucker-cups at the rear’. Thank goodness they only like fish!

However, there is one rare species discovered 60 years ago, Lethacotyle fijiensis, that appears to be clamp-less. The only available specimen for study is the one shown in the picture below.

The only available specimen of L. fijiensis

The only available specimen of L. fijiensis.


This close up below shows you what L. fijiensis actually looks like. The clamp-less haptor is the oblong protrusion on the very left end.


Close up of L. fijiensis

Because only four specimens of L. fijiensis have ever been found, and because having clamps is a major distinguishing feature of monogeneans, many researchers have assumed that L. fijiensis was incorrectly identified as clamp-less, and that these specimens probably lost their clamps through mishandling of the specimens by people.

In an attempt to verify the true nature of L. fijiensis, the authors went in search of additional specimens in the Pacific, where it was originally discovered. While they were unable to find any, they instead unearthed a hereto-undiscovered close relative, which they named Lethacotyle vera (vera is Latin for true, meaning that the genus Lethacotyle, is indeed real).

Haptor and Hooks

As it turns out L. vera is also a monogenean without clamps. The main physical difference between L. vera and L. fjiensis is the length in the male reproductive organ. The authors noted that L. vera has flaps on its haptor that are covered in many ridges, as well as hooks. A drawing of the haptor with its ridges and hooks can be seen in part F in the image to the right.


The authors sequenced the DNA from two of the eighteen specimens. The extracted DNA showed that the genetic information in L. vera is unique from all other known monogeneans. Then, in an effort to determine why L. fijiensis and L. vera don’t have the typical clamps of their family, they compared the ratio of clamp-to-body surface area in 120 different monogenean species. They found that members of the monogenean family to which L. vera and L. fijiensis belong, protomicrocotylids, had consistently the smallest clamp-to-body ratio. Additionally, many other species of polyopisthocotylean monogeneans had lateral flaps with ridges on their haptors.

From this observation, the authors concluded that in the family protomicrocotylids, their clamps are in fact slowly disappearing, and that in the specific case of L. fijiensis, the clamps have completely disappeared. The authors suggest that flaps can also hold onto the host, and that this process is assisted by the ridges and hooks along the flaps.

The discovery of a new species is always exciting, and as the case of L. vera shows us, can lead to insights about the larger family of related organisms. Read more about new species at PLOS ONE, such as this orchid or this Indonesian owl.

Citation: Justine J-L, Rahmouni C, Gey D, Schoelinck C, Hoberg EP (2013) The Monogenean Which Lost Its Clamps. PLoS ONE 8(11): e79155. doi:10.1371/journal.pone.0079155

Image 1 Credit: doi:10.1371/journal.pone.0079155.g001

Image 2 Credit: doi:10.1371/journal.pone.0079155.g002

Image 3 Credit: doi:10.1371/journal.pone.0079155.g007

Extra! Extra! Research Making the News in September

As September draws to a close, let’s look back on some of the research that caught the media’s attention, published this month in PLOS ONE: orangutans communicated their travel plans, mice permanently lost their fear of cats, and hibernating lemurs taught us about sleep.


While orangutans aren’t yet hiring travel agents, researchers recently published findings on these great apes, who apparently love to chat about travel plans. Male Sumatran orangutans develop flanges, large cheek pads, thought to assist in the vocalization of ‘long calls.’  Dominant males produce these calls in a specific direction, for anywhere from eighty seconds to four minutes.

Researchers tracked the movement of the dominant males and fellow orangutans in their arboreal territory after each call and found that the flanged male will travel in the direction of his howl until he produces a new long call along a different route. Local females also use the direction of the long call to stay within range of their dominant male, traveling the same course.  To find out more, check out the following articles in Scientific American, The New York Times, and the San Francisco Chronicle.

The relationship between mice and cats has taken a surprising turn.  Prior research revealed that mice infected with the parasite Toxoplasma gondii lost their fear of cats. This month, the tale continues with a new study published in PLOS ONE. Researchers exposed three types of mice to cat urine: mice never infected with T. gondii, mice currently infected, and mice cleared of the parasite. The cleared mice exhibited no anxiety over the potential threat of a nearby cat.A_Cat_And_Mouse_Game

The researchers suggest that the loss of fear in the mice becomes hardwired and that some parasitic infections may leave a lasting impact. Learn more about this study by visiting Nature, BBC News, and the Smithsonian.

New research on the ridiculously cute fat-tailed dwarf lemurs, — the only known hibernating primates — received highlights in National Geographic, The LA Times, and NBC News.

Researchers studied captive and wild fat-tailed dwarf lemurs, and found that they sleep differently during hibernation than other hibernating mammals. For instance, ground squirrels experience non-REM sleep during moderate temperatures, whereas fat-tailed dwarf lemurs experience mostly REM sleep.

While we don’t know much about why humans and animals sleep, we suspect that temperature and metabolic rate are affected. Now, hibernation isn’t exactly sleep; instead, hibernation is when the body dramatically reduces temperature and metabolic rate to conserve energy. Since both hibernation and sleep relate to the regulation of body temperature and metabolic rate, hibernation research on this little primate could teach us about human sleep, and maybe one day, human hibernation.


Ingram WM, Goodrich LM, Robey EA, Eisen MB (2013) Mice Infected with Low-Virulence Strains of Toxoplasma gondii Lose Their Innate Aversion to Cat Urine, Even after Extensive Parasite Clearance. PLoS ONE 8(9): e75246. doi:10.1371/journal.pone.0075246

Krystal AD, Schopler B, Kobbe S, Williams C, Rakatondrainibe H, et al. (2013) The Relationship of Sleep with Temperature and Metabolic Rate in a Hibernating Primate. PLoS ONE 8(9): e69914. doi:10.1371/journal.pone.0069914

van Schaik CP, Damerius L, Isler K (2013) Wild Orangutan Males Plan and Communicate Their Travel Direction One Day in Advance. PLoS ONE 8(9): e74896. doi:10.1371/journal.pone.0074896


Figure 1 from “Flanged Male Orangutan” by Anita Ritenour

Figure 2 from “Cat + Mouse” by Denis Defreyne

Keywords: orangutan, Sumatra, flanges, long call, hibernation, sleep, fat-tailed dwarf lemur, REM, non-REM, Toxoplasma gondii, mice, fear, parasite, metabolic rate, temperature, hypothermia, homeostasis, Cheirogaleus medius, Madagascar, Pongo abelii, great apes.

Understanding the Science Behind the Marvel: Why is the Río Celeste so Blue?

Río _Celeste_Waterfall

Recently, PLOS ONE published the science behind the surprising coloration of the river in the photo above. The beautiful, cloudy cyan waters may look heavily photoshopped, but they’re quite real. This is the actual color of Río Celeste, one of Costa Rica’s more unusual natural wonders. While there are other known examples of waters in such striking hues, such as Japan’s Goshiki-numa lakes, the Río Celeste is the only known river whose color forms at the junction of two crystal-clear sources. And so the question asked for centuries is, what creates this sky-blue hue?

The photo below gives you a better idea of what happens when Quebrada Agria and Río Buenavista, the waterways that merge to form Río Celeste, meet. What you see here is called Teñidero, or ‘dye point’, where the transparent water suddenly turns to turquoise.


Río Celeste, similar to other examples of brilliantly colored waters, is located in a volcanic region. Hypotheses surrounding the origin of this milky blue hue include everything from thermal bacteria to the suspension of colorful minerals (such as copper) throughout the water.

Minerals suspended in water that do not dissolve are sometimes called colloidal particles, and are known for their ability to reflect and scatter light. Currently, these particles are one of the reasons for other examples of jewel-toned waters, such as Yu-gama Crater Lake in Japan. To see if they were also the cause of the sky-blue coloring in this case, researchers collected water and sediment samples from Río Celeste and the two rivers that merge to form it, and then tested the physical (size and distribution) and chemical (pH) properties of each.

The authors used a special separation technique, called ion exchange chromatography, to find out if colored metallic minerals such as copper, nickel, or cobalt were abundant enough to cause the Río Celeste’s turquoise coloration.

It turns out that there were only minute amounts of colored metals ores found in the samples—certainly not enough to cause a whole river to turn blue! However, what the researchers did find is that Río Buenavista has significant concentrations of silicon, as does Quebrada Agria, the latter of which additionally contains sulfate, chloride, and calcium.

Previous studies have shown that colloidal silica (silicon and oxygen) particles between 100- 450 nanometers (nm) in diameter could cause the blue coloration of the water because they reflect light in a particular way. In fact, if these particles are larger than 450 nm, they can create milky hues as well— the same colors and tones found in Río Celeste.

In the figure below parts a and b show a microscope image of the sediment found at the bottom of the Río Celeste; from this, researchers concluded that the pictured clusters were created by gradual buildup of smaller particles in the water. The spectrum below a and b indicates the makeup of this sediment is mostly aluminum, silicon and oxygen, with small amounts of sulfur and iron. Based on the light-scattering properties of colloidal silica, the authors hypothesized that the presence of aluminosilicate in the rivers could have a similar light scattering effect.


So where did these particles come from? It turns out Quebrada Agria’s waters contain aluminosilicate particles too small (< 10 nm) to have an effect. However, Río Buenavista contains aluminosilicates well distributed throughout, and while these are larger (184 nm), they are not concentrated enough to actually create a noticeable scattering of light.

They key to figuring out this puzzle was that, when testing the pH, researchers found that Quebrada Agria was fairly acidic (pH of 3.1, or about as acidic as an orange), and Río Buenavista was rather neutral with a pH of 6.8.

The researchers realized that when the acidic and neutral waters of the two rivers meet, their aluminosilicate particles clump together, resulting in enough particle concentration and size to scatter light and voilà  – the Río Celeste in all its turquoise glory!


Citation: Castellón E, Martínez M, Madrigal-Carballo S, Arias ML, Vargas WE, et al. (2013) Scattering of Light by Colloidal Aluminosilicate Particles Produces the Unusual Sky-Blue Color of Río Celeste (Tenorio Volcano Complex, Costa Rica). PLoS ONE 8(9): e75165. doi:10.1371/journal.pone.0075165

Images: Figure 1, 2 and 3 from the article.

Keywords: river, water, aluminosilicate, clay, light scattering, Mei scattering, Costa Rica, Río Celeste, Goshiki-numa lakes, Teñidero, Quebrada Agria, Río Buenavista, tourism, tourist sites, waterfall, lagoon, Yellowstone, thermal pools, colloidal particle, ion exchange chromatography, Yu-gama Crater Lake, thermal bacteria, silica