University of Basel
Macrostomum lignano: an introduction
Model systems drive progress in biology and thus progress in the notoriously understudied simultaneous hermaphrodites requires suitable model organisms. Ideally, such a model should allow for controlled laboratory experiments, easy determination of sex allocation and reproductive morphology. It should have a short generation time to allow for powerful breeding, selection and experimental evolution experiments. The free-living flatworm Macrostomum lignano (Plathyhelminthes: Rhabditophora: Macrostomida) unites all of these requirements and offers some other important advantages.
Macrostomum lignano is transparent, only about 1.5 mm in size, easy to keep in the laboratory, and has a generation time of only 18 days. Different species in the genus Macrostomum show striking variation in genital and sperm morphology. Moreover, Macrostomum lignano is a rapidly growing model system for developmental biology, which means that there are many powerful methods that have been established for it. These include immunocytochemistry, in situ hybridization, RNA interference (RNAi), transgenesis (GFP), and various genomic resources.
Macrostomum lignano is a new species
When we started to work with this species it was new to science (collected for the first time in 1995). We therefore described the species taxonomically (Ladurner et al. 2005b), and named it after the beach we collected it from.
Macrostomum lignano is transparent
the transparent nature of Macrostomum lignano allows for convenient observation
and quantification of internal structures, organs and processes
One of the major advantages of working with worms of the genus Macrostomum is that they are almost completely transparent, allowing non-invasive investigation and measurement of many internal structures, organs and processes, such as gonad size and sperm transfer.
Macrostomum lignano is easy to keep in the laboratory
its small size allows to keep many thousands of individuals of Macrostomum lignano at mimimal cost
(double-click on the movie to see a few worms in a petri dish
running away from a light source in the upper left corner)
Macrostomum lignano has a short generation time
the short, 18 day generation time makes Macrostomum lignano highly suitable for microevolutionary studies
Members of the genus Macrostomum lignano show interesting variation in genital morphology
copulatory organs of four different species in the genus Macrostomum to scale,
also note the different granular prostate gland secretions
Macrostomum lignano is allows powerful phenotyping methods
the testis of an adult M. lignano (double-click to see the movie)
the tail of an adult M. lignano containing the
seminal vesicle and the copulatory stylet
(double-click to see the movie)
a fluorescent contrast method that allows us to use a confocal laser scanning microscope
to obtain a computer tomography-like observation of internal structures on whole-mounted Macrostomum lignano
Macrostomum lignano is a developmental biology model organism
Macrostomum lignano is also an increasingly important model organism for the developmental biology of the lower Bilateria, and many essential research tools have been developed over the last years. There is a wealth of histological, electronmicroscopical and immunocytochemical methods that have been developed to study embryology, postembryonic development, differentiation of the gonads and the impressive regeneration ability.
Moveover, flatworms have a unique stem cell system, in which all differentiated cells appear to derive form totipotent stem cells. There are established methods to visualize these cells and to quantify their proliferation rate (see Ladurner et al. 2008 for a review). As these cells also produce the male and female germ cells, their proliferation rate is probably responsible for sex allocation adjustment, so my group is also interested in stem cell biology.