The Breakdown of "Bifurcus"

Bi translates to "two" while furca means fork, relaying to the two dark lines that are on either side of the median strip on the organism.

Domain: Eukarya
    Kingdom: Animalia
        Phylum: Platyhelminthes
            Class: Turbellaria
                Order: Polycladia
                    Family: Pseudocerotidae
                        Genus: Pseudoceros
Species: Pseudoceros bifurcus

Figure 1. Pseudoceros bifurcus image by Nataliya Bondarenko

Classification Clarification

Eukarya includes all organisms with eukaryotic cells, or cells that have organelles, such as mitochondria. A large amount of organisms in this domain are seen very regularily. Members of this domain are either unicellular (like some yeasts), multicellular (for instance, animals), or colonial (some protists that undergo cell division by mitosis).
Its kingdom, Animalia, hosts a wide variety of different animals. These animals have a lot of differences and similarities, including:

  • Developing from embryos
  • Having an internal cavity (where they digest their ingested food)
  • Being motile
  • Reproducing sexually with haploid egg and sperm
  • Being organized into tissues from cells (with the exception of sponges)
Fig. 2. Pseudoceros bifurcus image by Alain-Benoît Rassat

They are placed in the phylum Platyhelminthes along with organisms like Taenia solium because of their soft bodies. They share this phylum with about 25,000 other species of worms, including tapeworms. In Greek, the prefix platy means "flat" and helminthes means "worms." Only the Turbellarians are non-parasitic worms in this phylum, which means they are seen as free living. There are about 3,000 Turbellarians species known to man, such as this tiger flatworm (pictured to the right), and as far as scientists are concerned, the other three classes of Platyhelminthes derived from the Turbellarians. Amoung the 12 different orders within this class, our flatworm falls within amongst the other Polycladidas. The origin of this word means "many branches," which pertains to their branched digestive systems. The organisms in this order are often very colorful and vibrant, but there are also some that contain less pigment. The Polyclads are distinguished by having an eversible pharynx and a complicated set of sexual organs (for more about how Pseudoceros bicurus reproduces, please click here). The Pseudocerotidae family is distinguished by their prominent tentacles and oval-shaped bodies. Within Pseudocerotidae, there are many genera; this marine flatworm in particular belongs to Pseudoceros, which was discovered 1884.

Fig. 4. Phylogenic tree of the phylum Platyhelminthes, from evodevojournal.

The Platyhelminthes phylum is broken down in the tree in fig.1. Pseudoceros bifurcus belongs in the Polycladida order. It shares a most common recent ancestor with the orders Lecithoepitheliata and Macrostomorpha. What sets Polycladida apart from the other groups is that the organisms within it are able to produce larvae. The Catenulida, Macrostomorpha and Polycladida are all apart of a group called Archoophora and the other orders are grouped into a group called Nephora.

Fig. 5. Phylogenetic tree created by Dr. Litvaitis, M. K. with some alterations by us.

This phylogenetic tree maps the relationships between the organisms in the Pseudocerotideae family. Our organism falls into the category Pseudocero bifurcus, with the red square around it. The other species most related to our organism is the Pseudoceros bicolor, the two-colored flatworm, because they share the closes common ancestor. The second closest related species to our organism is the Pseudoceros paralaticlavus, otherwise known as the goldrim flatworm.

Continue to learn about this flatworm's habitat

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