Buddenbrockia plumatellae
Encyclopedia
Buddenbrokia plumatellae is a parasitic worm whose taxonomic placement long puzzled biologists. It is now classified as one of the only two myxozoa
ns of class
Malacosporea on the basis of both genetic and ultrastructural studies. It was the first multicellular myxozoan identified and its vermiform shape gave strong support to the theory that the enigmatic group belongs among the Bilateria
. Five years later, this was refuted by a study of fifty genes from this same "worm", which had rarely been even seen since its discovery in 1851. These 50 phylogenetic markers reveal that Buddenbrockia is closely related to jellyfish
and sea anemone
s, typical members of a major animal
group, the Radiata
. Because of the fast amino acid replacement rate of the nuclear proteins of Buddenbrockia, as compared to those of the remaining animals sampled in this study, only the use of a sophisticated tree-building approach (i.e., Bayesian inference
) allowed to recover its cnidarian evolutionary affinities.
One of the researchers talked about the problems encountered studying its morphology
: “It has no mouth, no gut, no brain and no nerve cord. It doesn’t have a left or right side or a top or bottom – we can’t even tell which end is the front!” Because the myxozoans are so different from their nearest relatives, he concluded that “the worm-like body shape evolved at least twice from two completely different kinds of animal.”
Myxozoa
The Myxozoa are a group of parasitic animals of aquatic environments. Over 1300 species have been described and many have a two-host lifecycle, involving a fish and an annelid worm or bryozoan. The average size of a Myxosporea spore usually ranges from 10 μm to 20 μm and Malacosporea up...
ns of class
Class (biology)
In biological classification, class is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, order, family, genus, and species, with class fitting between phylum and order...
Malacosporea on the basis of both genetic and ultrastructural studies. It was the first multicellular myxozoan identified and its vermiform shape gave strong support to the theory that the enigmatic group belongs among the Bilateria
Bilateria
The bilateria are all animals having a bilateral symmetry, i.e. they have a front and a back end, as well as an upside and downside. Radially symmetrical animals like jellyfish have a topside and downside, but no front and back...
. Five years later, this was refuted by a study of fifty genes from this same "worm", which had rarely been even seen since its discovery in 1851. These 50 phylogenetic markers reveal that Buddenbrockia is closely related to jellyfish
Jellyfish
Jellyfish are free-swimming members of the phylum Cnidaria. Medusa is another word for jellyfish, and refers to any free-swimming jellyfish stages in the phylum Cnidaria...
and sea anemone
Sea anemone
Sea anemones are a group of water-dwelling, predatory animals of the order Actiniaria; they are named after the anemone, a terrestrial flower. Sea anemones are classified in the phylum Cnidaria, class Anthozoa, subclass Zoantharia. Anthozoa often have large polyps that allow for digestion of larger...
s, typical members of a major animal
Animal
Animals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and...
group, the Radiata
Radiata
The Radiata are the radially symmetric animals of the Eumetazoa subkingdom. The term Radiata has had various meanings in the history of classification...
. Because of the fast amino acid replacement rate of the nuclear proteins of Buddenbrockia, as compared to those of the remaining animals sampled in this study, only the use of a sophisticated tree-building approach (i.e., Bayesian inference
Bayesian inference
In statistics, Bayesian inference is a method of statistical inference. It is often used in science and engineering to determine model parameters, make predictions about unknown variables, and to perform model selection...
) allowed to recover its cnidarian evolutionary affinities.
One of the researchers talked about the problems encountered studying its morphology
Morphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....
: “It has no mouth, no gut, no brain and no nerve cord. It doesn’t have a left or right side or a top or bottom – we can’t even tell which end is the front!” Because the myxozoans are so different from their nearest relatives, he concluded that “the worm-like body shape evolved at least twice from two completely different kinds of animal.”