Scaridium longicaudum (O. F. Müller, 1786)

Most likely ID: n.a.


Synonym: n.a.


Sampling location: Simmelried


Phylogenetic tree: Scaridium longicaudum



  • length 360 – 423 µm,
  • body more or less cylindrical
  • foot long, tripartite, with two long toes
  • wheel organ oblique
  • on mastax a red-stained plate (no eyespot!)
  • resting egg about 70 – 80 µm long, hairy
Scaridium longicaudum

So far I have found Scaridium longicaudum exclusively in the Simmelried. There I could detect it in the floating plants in August 1998, in August 2005 and in June 2022. Thus, the species seems to be bound to the summer months, which agrees with the information from the literature (May to October). Specimens collect at the water surface in the samples. In my poulation, very large specimens were present, up to 430 µm in length (s. fig. 1), which corresponds to the maximum length attainable. Scaridium longicaudum has a conspicuous red spot at the apical area. This is not an eye spot, as in many other rotifers, but a red colored plate on the mastax (s. fig. 3). The species is very easy to identify by the long foot with paired, also long toes, which are pointed at the end. In the foot are many muscle fibers arranged, which allow a fast jumping movement as an escape reaction.


More images and information of Scaridium longicaudum: Michael Plewka-Freshwater life-Scaridium longicaudum


Fig. 1: Scaridium longicaudum. L = 430 µm. Lateral view from left of a slightly squashed specimen. Obj. 40 X.


Fig. 2 a-b: Scaridium longicaudum. L = 430 µm. Two focal planes of the body in lateral view from left. Obj. 60 X.


Fig. 3: Scaridium longicaudum. L = 430 µm. The body in detail. The mastax is covered with a red stained plate, which simulates an eye spot. Obj. 100 X.


Fig. 4: Scaridium longicaudum. L = 430 µm. Part of the foot with an complex arrangement of muscle fibers. Obj. 60 X.


Fig. 5: Scaridium longicaudum. Two focal planes of a resting egg. The surface is covered with hair-like protrusions. Obj. 60 X