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

  • Order: CHAETONOTIDA Remane, 1925
    • Suborder: PAUCITUBULATINA d'Hondt, 1971
      • Family: CHAETONOTIDAE Gosse, 1864
        • Subfamily: CHAETONOTINAE Kisielewski, 1991
          • Genus: Chaetonotus Ehrenberg, 1830
            • Subgenus: Primochaetus
              • Species: acanthodes Stokes, 1887
(after (Stokes, 1887))
Length ( bottle-shaped ):
124 µm - 159 µm

35 µm - 40 µm

Width of the head ( weakly five-lobed ):


Length of the furca:
13 µm - 21 µm

Adhessive tubes:
75% of furca

Pharyx ( cylindrical, terminal swollen ):
31 µm - 39 µm

Diameter of the mouth ( round ):
8 µm

Dorsal scales:
10 rows of 20-25 strongly overlapping, rounded triangular scales (5 µm - 8.5 µm) with strongly convex margin (margin appears double) with short spines (7 µm); 7 - 12 simple girdle spines (6.5 µm - 16.5 µm) in alternating rows; scales behind spine girdle mostly without spines

Ventral scales:
4 elongated terminal plates with keel; 8-9 rows of small keel scales

Moor, on mud

Similar species:
well demarcated by spine belt and double scale edge

Spiked belt and double scale edge


A further representative of the subgenus Primochaetus is the small abdominal hardy Ch. (P.) acanthodes, which is notable for its distinct, spineless scales with a “double” anterior contour and a belt of long spines on the abdomen:

Ch. acanthodes: dorsal scales

Only in the lateral view one recognizes that the spiny belt covers the entire dorsal side of the animal:

Ch. acanthodes: side view

The ventral intermediate field is covered with approx. 8 rows of small, roundish keel scales. The rear end is formed by four rectangular, narrow keel plates:

Ch. acanthodes: ventral scales

In cross-section it becomes clear that the scales are strongly curved. This results in the “double contour” in the o0ical section. The animals I found have one or two teeth at the entrance to the pharynx:

Ch. acanthodes: Cross section


(Stokes, 1887)