The Small World of Freshwater Gastrotrichs
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Chaetonotus (H. ) italicus

  • Order: CHAETONOTIDA Remane, 1925
    • Suborder: PAUCITUBULATINA d'Hondt, 1971
      • Family: CHAETONOTIDAE Gosse, 1864
        • Subfamily: CHAETONOTINAE Kisielewski, 1991
          • Genus: Chaetonotus Ehrenberg, 1830
            • Subgenus: Hystricochaetonotus
              • Species: italicus Balsamo & Todaro, 1995
(after (Balsamo & Todaro, 1995))
Length ( bottle-shaped ):
91 µm - 110 µm

- 25 µm

Width of the head ( five-lobed ):
18 µm

- 13 µm

Length of the furca:
11 µm - 17 µm

Adhessive tubes:

Pharyx ( cylindrical ):
27 µm - 29 µm

Diameter of the mouth ( round ):

Dorsal scales:
13 rows of 13-14 three-lobed scales (6.5µm x 5µm) with simple spine (3µm - 10µm); typical scale group for Hystricochaetonotus without spines at the posterior end

Ventral scales:
ventral intermediate field with two rows of 20 rectangular scales each (1.2µm - 4µm); two keeled terminal plates (length 6.4µm - 6.8µm)


Similar species:
all Hystricochaetonotus; precise diagnosis required

Spines without secondary tip; unique scaling of the ventral intermediate field


The small gastrotrich Chaetonotus (H.) italicus, previously only known from Italy, is relatively common in the Sima bog.

Ch. italicus: dorsal

Many of the specimens found were in their post-parthenogenetic (hermaphroditic) phase and bore both a distinct, bipartite X-organ and rod-shaped spermatoids. The pronounced dumbbell-shaped pharynx is typical of the species:

Ch. italicus: t.s.

The ventral intermediate field is covered with two rows of rectangular scale plates, which become more indistinct in the neck area. Two keeled terminal plates form the end:

Ch. italicus: ventral

Although the scale spines do not have a secondary tip, the classification in the subgenus Hystricochaetonotus is clear due to the typical scale shape:

Ch. italicus: scale form


(Balsamo & Todara, 1995)