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Schärer Group
Evolutionary Biology
Zoological Institute
University of Basel
Vesalgasse 1
CH-4051 Basel

Paraspadella gotoi, another transparent simultaneous hermaphrodite

a living Paraspadella gotoi, a chaetognath

Chaetognaths are another group of transparent simultaneous hermaphrodites which I evaluated for their suitability as a model system to study sex in hermaphrodites. For this I went to Japan for one month in autumn 1999, where I visited Dr. Taichiro Goto, at the Mie University in Tsu. Taichiro is one of the few people world-wide who currently cultures these enigmatic creatures in the lab. His main study species is the benthic chaetognath Paraspadella gotoi. The short stay did not allow me to make enough research for a publication on these creatures, but they will forever have a place in my heart. And I would also like to thank Taichiro for his amazing hospitality. I think I have never eaten so much good food in such a short time.
Chaetognaths are very enigmatic creatures, and taxonomists still are not sure where to place them. All chaetognaths are simultaneous hermaphrodites. Most species live in the plankton where they can become incredibly abundant. They are ferocious carnivores, and primarily eat copepods (and other chaetognaths). Planktonic creatures are not used to walls, though, which may be why most species can not be kept in he lab. The exception are a few species that migrate between the plankton and the sea floor, and especially the members of the Spadellidae, which are mostly benthic.
As I haven't really worked with chaetognaths for very long, I can only talk about other peoples' work. Here are a few of the reasons why chaetognaths are so interesting.
Germ Cell Development
Chaetognaths have a very interesting germ cell development. In the early embryo a germ granule forms that differentiates into four primary germ cells. These cells could be manipulated to manipulate the sex allocation of a worm (more on this).
Fertilization Biology
Chaetognaths also have a very intriguing fertilization system (more on this).
Mating Behaviour
The mating behaviour of these creatures is also absolutely stunning (more on this).
One final aspect of these worms is that they are just plain beautiful (see for yourself).

this page was last updated on Tuesday, December 22, 2015