[Annelida] Hobsonia florida

Michael Reuscher via annelida%40net.bio.net (by Michael.Reuscher from gmx.net)
Wed Sep 19 07:27:49 EST 2007

Hello everybody,
I hope I can help you to solve the confusion about freshwater ampharetids.
There are, as I know, four small ampharetid genera occuring in fresh- and brackish water: Alkmaria, Hypania, Hypaniola and Hobsonia. Parhypania is a junior synonym of Hypania. For further information you could check the excellent homepage of Torleif Holthe: http://folk.ntnu.no/vmzothol/TERHP.htm
Hobsonia florida was originally desribed as subspecies Amphicteis gunneri floridus by Olga Hartman (1951). Later it gained species status as A. floridus. I think this was done by Zottoli. I dont have access to his thesis, but he published his results: Reproduction and larval development of the ampharetid polychaete Amphicteis floridus. Transactions of the American Microscopical Society 93: 78-89. He gives some differences between H. florida and A. gunneri: Hobsonia has 2 pairs of nephridia (instead of 4-5), the abdominal number is 22-28 (instead of 15), no anal cirri and no or small number of rudimentary notopodia.
The animals he examined were collected in "upper reaches of the Piscatiqua River, New Hampshire.
Banse gave this species even an own genus. He justified it with the very small number or lack of rudimentary notopodia, lack of paleae (the first pair of bristles look like paleae but if you watch carefully, they don`t seem to be), but especially with the inner anatomy (I`m not sure if that was about nephridia or the digestive track which seems to be distinct to the genus Amphicteis).
I haven`t heard of a Hypaniola florida Pettibone 1977, but in 1953 Pettibone described Hypaniola grayi which is a junior synonym of Hobsonia. florida (see also Holthe`s page).
For the distinction to other freshwater types:
Alkmaria and Hypania could`t be confused with Hobsonia, because they have 13 thoracic segments bearing uncini, while Hobsonia has 14.
Hypaniola has also 14 thoracic uncinigers, but it has no glandular ridges on the prostomium, while Hobsonia has these ridges.

best regards

Michael Reuscher

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