The Small World of Freshwater Gastrotrichs
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Chaetonotus (P. ) acanthocephalus

  • Order: CHAETONOTIDA Remane, 1925
    • Suborder: PAUCITUBULATINA d'Hondt, 1971
      • Family: CHAETONOTIDAE Gosse, 1864
        • Subfamily: CHAETONOTINAE Kisielewski, 1991
          • Genus: Chaetonotus Ehrenberg, 1830
            • Subgenus: Primochaetus
              • Species: acanthocephalus Vulkanov, 1937
(after (Vulkanov, 1937))
Length ( bottle-shaped, rotund ):
100 µm - 148 µm

28 µm - 30 µm

Width of the head ( five-lobed ):


Length of the furca:
16 µm - 20 µm

Adhessive tubes:
75% of furca

Pharyx ( cylindrical ):
37 µm - 40 µm

Diameter of the mouth ( around ):
6.5 - 8 µm

Dorsal scales:
5 rows of 15-18 transverse oval scales (5 x 10 µm) each, not touching; on head dorsally and laterally 5-7 characteristic spiny scales; small spines 6-7 µm; groups of large spines 8-22 µm.

Ventral scales:
Ventral intermediate field on head 3 touching plates; otherwise elliptical plates; in gut region sometimes 3 deer of smaller elliptical plates.

Bog waters, rare, very variable

very variable with respect to spine size - possibly a number of subspecies


A very rare and strange ventral hardy is the nearly rotund Chaetonotus (P.) acanthocephalus with its irregular spination and large, round scales:

Dorsal Ch. acanthocephalus: focus on the dorsal scale

Ventrally, the animal bears large cuticular plates on the head that change to round, short-spined scales toward the posterior end:

Ventral Ch. acanthocephalus: ventral

If the animal is macerated with glacial acetic acid, the scale shape typical for the subgenus Primochaetus becomes particularly clear:

macerated Ch. acanthocephalus: Macerated


(Vulkanov, 1937)