by Piter Kehoma Boll
Today we have one more flatworm in our team. It is part of the most bizarre group of flatworms, the so-called Catenulida. Our fellow is called Catenula lemnae, which I adapted as the “duckweed chain flatworm”.
The duckweed chain flatworm is a very small animal, measuring about 0.1 mm in width and about two or three times this size in length. It is found worldwide in freshwater lakes and ponds and is likely a complex of species, but more detailed studies are needed to make it clear. As other catenulids, it lives close to the substract, being considered a benthic animal, and feeds on other smaller organisms, such as small invertebrates and algae. It is usually a dominant species in the community of benthic microanimals, such as microturbellarians, in places where it is found.
The word catenula, meaning “little chain” in Latin, was given to these animals because of their peculiar way of vegetative reproduction. The organism frequently divides transversally close to the posterior end, giving rise to new organisms that are genetically identical to the original one. However, the new animals often remain connected to each other for a long time before splitting, and as this asexual reproduction continues, it eventually turn them into a chain of connected individuals (called zooids). This chain swims elegantly using its cilia as if it were a single individual.
Most recent studies mentioning the duckeed chain flatworm are simply surveys of the species composition of a certain area or broad phylogenetic studies on the catenulids or flatworms in general. Little is known about the ecology, behavior and population structuring of this species, unfortunately.
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Braccini, J. A. L.; Leal-Zanchet, A. M. (2013) Turbellarian assemblages in freshwater lagoons in southern Brazil. Invertebrate Biology, 132(4): 305–314. https://dx.doi.org/10.1111/ivb.12032
Marcus, E. (1945) Sôbre Catenulida brasileiros. Boletim da Faculdade de Filosofia, Ciências e Letras da Universidade de São Paulo, série Zoologia, 10: 3–113.
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