Sunday, September 21, 2014

Loa loa - African Eye Worm

Wednesday, September 10, 2014

Loa loa - African Eye Worm

Author: Natalie Ameral

Photo Courtesy of workforce.calu.e


(Animal Diversity Web, 2014):
    Domain: Eukarota
        Kingdom: Animalia
    Phylum: Nematoda
    Class: Secernentea
        Order: Spirurida
        Family: Filariidea
        Genus: Loa
        Species: loa



Scientific and common name:

       Unfortunately, this nematode gets its name from the area in which it resides as a parasite in the human body: the eye. Shortly after the discovery of this nematode in 1770, in 1778 these worms were found in the eyes of slaves being transported via ship (Borg, 2007). Currently, this infestation of the eye is most commonly found on the Atlantic side of Africa, specifically surrounding the Gulf of Guinea (Borg, 2007).



Loa loa has found a fantastic niche for itself in the tropical rain forest and savanna biomes of coastal west Africa (Kelly-Hope, 2012). 

PLOS website - Hope-Kelly 2012

 The graph above is by far the best indicator of Loa loa distribution. The x axis represents the western, central, and eastern regions of the Congo river system in all the graphs. Elevation is measure in meters, NDVI is vegetation, precipitation is measured in millimeters, temperature in degrees Celsius, and humidity in specific humidity. Interestingly, different variable are more suitable for different locations. For example, a lower temperature is selected for in the east as opposed to a higher temperature in the center. This variation may make it easier for people to decide where to live and farm if Loa loa is a concern of theirs.     

Physical description and life cycle:

According to Borg (2007), worms range from 2 cm to 7 cm in length, females being longer than males. Comparatively, this is quite large for most nematodes. Borg also explains the life cycle of Loa loa. Most of the life processes take place in the human body host. Larva grow under the skin and once mature lay eggs. These eggs have been found in blood, urine, and spinal fluid. 

Interesting trivia:

Loa loa do not make it into the human blood stream on their own. The middle man of the infestation process is the mango fly (Borg, 2007). The larvae first make their journey into a human host via a bite made by the mango fly (Borg, 2007). This bite contains larvae that will use the host to grow and become adult worms (Borg, 2007). Once the adult worms lay their eggs, another Mango fly may come along, bite the human, and ingest these larvae (Borg 2007). The larvae are then deposited into another human via another bite (Born 2007). 

  • Myers, P., R. Espinosa, C. S. Parr, T. Jones, G. S. Hammond, and T. A. Dewey. 2014. The Animal Diversity Web (online). Accessed at
  • Borg L. 2007.
  • Kelly-Hope Louise A. et al. June 26, 2012. Loa loa Ecology in Central Africa: Role of the Congo River System. Public Library of Science.

Saturday, September 6, 2014

Panagrellus redivivus, the German Beer Mat Nematode


Author: Dr. Ellen Batchelder, Assistant Professor of Biology, Unity College, Unity, Maine

Figure 1: Panagrellus nematode carrying the same yeast they feed on.
(Tree of Life Web Project, 2002):
    Domain: Eukarota
        Kindom: Animalia
    Phylum: Nematoda
    Class: Chromadorea
        Order: Rhabditida
        Family: Panagrolaimidae
        Genus: Panagrellus
        Species: redivivus



Scientific and common name:

Nathan Cobb, the father of nematology in the US (Esser et al., 1989), is quoted in many sources for his reference to a species of nematode occurring in “… the felt mats on which Germans are accustomed to set their mugs of beer…” The nematode in question is known by the scientific binomial Panagrellus redivivus and more commonly as the beer mat nematode (Ferris, 2009) or the sour paste nematode (Stock and Nadler, 2006). In addition to German beer mats, it has also been isolated from rotten peaches and book binding paste (Ferris, 2009). 


Taxonomy and Ecology:

What is now the genus Panagrellus was first called Chaos by Carl Linnaeus, the scientist who developed the system of binomial naming (Ferris, 2009), and he originally included protists and fungi along with nematodes in that genus. Today, Panagrellus includes at least 13 known species of nematodes that feed on fermenting yeast (Ferris, 2009), (Hechler, 1971). They are free-living nematodes found in habitats where certain species of yeast grow well, including beer mats, insect frass, tree wound slime, soiled cider (vinegar), thermal springs, and book binding glue (in fact, in other types of paste made from wheat flour) (Stock and Nadler, 2006), (Ferris, 2009).
Species of Panagrellus have been found so far in nearly all corners of the world except Antarctica and Australia (Stock and Nadler, 2006).



Physical description and life cycle:

             Similar to many other nematodes, P. redivivus females are small (0.5 mm- 2 mm) with males

Figure 2: Panagrellus male tale with bifurcated spicule.
From: (Ferris, 2009) and (Hechler, 1971).
that are slightly smaller than females (Stock and Nadler, 2006), (Atchison, 2009).Once P. redivivus females reach maturity (~3 days), males mate with them via a curved tail with two long, split spicules (Stock and Nadler, 2006). Females do not lay eggs as some other nematode species do, but lay 10-40 live larvae every day or so for their three week lifetime (Atchison, 2009).

            Panagrellus nematodes do not have many distinguishing anatomical characteristics, but a relatively wide, long mouth and several sets of teeth in adults are consistent with their diet of yeast (Ferris, 2009).


Interesting trivia:

            Pangrellus redivivus are known to aquarists as microworms (Atchison, 2009). They contain a relatively large amount of protein and lipids and are grown and sold as food for newly-hatched fish, crustaceans, newts, and frogs (Atchison, 2009), (Ferris, 2009). They can be grown in a liquid culture and fed on media containing oatmeal or other cooked cereals (Atchison, 2009). The grains provide food for yeast which, in turn, provide food for the reproducing nematodes.

Figure 3: head of P. redivivus, showing hourglass shaped esophagus. Scale bar 100 μm.
Forum: Photography through the microscope. Topic: Internal young - sour paste nematode (Panagrellus redivivus) Author: Visikol


  • Atchison J. Microworms [Internet]. San Rafael(CA):The Bug Farm; [2009, cited 2014 Sept 5] . Available from:
  • Esser, R., Tarjan, A., and Perry, V. 1989. Jesse Roy Christie: The gentleman nematologist. Annu. Rev. Phytopathol. 27: 41-45.
  • Ferris, H. 2009. The beer mat nematode, Panagrellus redivivus: A study of the connectedness of scientific discovery. J. Nematode Morphol. Syst., 12 (1): 19-25.
  • Hechler, H. 1971. Taxonomic Notes on Four Species of Panagrellus Thorne (Nematoda: Cephalobidae) J. Nematol.3(3): 227–237.
  • Stock, S., and Nadler, N. 2006. Morphological and molecular characterization of Panagrellus spp. (Cephalobina: Panagrolaimidae): taxonomic status and phylogenetic relationships. Nematology, Vol. 8(6), 921-938.
  • Tree of Life Web Project. 2002. Animals. Metazoa. Version 01 January 2002 (temporary). in The Tree of Life Web Project,