Fig. 1: Ptygura kostei on a Java moss (Taxiphyllum barbieri) filament. The somatic body is retracted, the characteristic nuchal fork can be seen with three of the four hooks of approximately equal size. Scale bar indicates 100 µm. |
The form group Ptygura furcillata–elsteri–kostei is characterized by the presence of a nuchal fork. Ptygura kostei was first described by Koste as a forma of the species Ptygura elsteri. Susana Beatriz José de Paggi redescribed it as a separate species in 1996 on the grounds that the four hooks on the nuchal fork are equal in size, while in P. elsteri they form unequal-sized pairs.
José de Paggi, Susana. (1996). Rotifera (Monogononta) diversity in subtropical waters of Argentina.
http://dx.doi.org/10.1051/limn/1996019. 32. 10.1051/limn/1996019.
Fig. 2: The three optical sections show the nuchal fork with its base rod (double arrowhead), the trophi (arrow) and the fully opened corona (double headed arrow). The focal planes are below = dorsal side of the rotifer (left image), in the middle of the body (middle image) and above = ventral (right image). Scale bar indicates 50 µm. |
Fig. 3: Fully expanded rotifer in lateral view in median optical section showing base rod and 3 of 4 hooks of the nuchal fork (double arrowhead), trophi (arrow) and fully opened corona. The inset above right shows the rotifer in ventral view with fully retracted somatic body, which allows an unimpeded view of the four hooks of the nuchal fork. Scale bar indicates 50 µm. |
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