Stenostomum paraguayense ( Martin, 1908 ), Luther, 1908

Noreña, Carolina, Damborenea, Cristina & Brusa, Francisco, 2005, A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters, Zoological Journal of the Linnean Society 144 (1), pp. 37-58 : 47-49

Stenostomum paraguayense ( Martin, 1908)

Luther, 1908

( Fig. 3A )

Weldonia parayguensis Martin, 1908

Description: Solitary specimens up to 0.8 mm long. Chains with 2–3 zooids with different degrees of development. Oval body, blunt anterior end, with a constriction behind the mouth. Extended lateral ciliated pits. Posterior end with an intestine-lacking region, with two caudal finger-like extensions, a long ventral one and a short dorsal one. Homogeneous ciliated epithelium. Small rhabdites, scarce on a mid-dorsal line from the postoral constriction to the caudal extension. Colour in life light brown.

Anterior brain lobes deeply dentate. Three pairs of type 2 light-refracting bodies. The first two pairs are formed by one sphere and are placed subcutaneously over the sensory cells of the ciliated pits. The third pair is formed by two spheres, also superficial and associated with the posterior brain lobes.

Oral pore triangular. Pear-shaped pharynx. Pharyngeal glands (type a) arranged in the posterior half. A row of glandular cells in the ventral region of the pharynx (area of insertion for the musculature of the buccal lower lip). Fifteen to 25 cells with refringent granules form a ‘transverse’ row in the first third of the intestine. Nephridiopore opening between the caudal appendages.

Distribution: Paraguay ( Martin, 1908); São Paulo and interior of São Paulo State, Brazil ( Marcus, 1945b); Onverdacht, Surinam ( Van der Land, 1970); Los Talas, Berisso, Buenos Aires, Argentina, September 1998 to July 1999, December 1999 to February 2000. This species has not been previously recorded in Argentina.

Stored material: Four sagittally sectioned specimens in the CHMLP. No. 5305.

Discussion: This species was described by Martin (1908) as W. parayguensis . Because this material came from Paraguay (South America), the original spelling was corrected by Marcus (1945b) (article 32.5 in the ICZN, 2000).

S. paraguayense was placed in the genus Stenostomum by Luther (1908) and it was considered as a synonym of Stenostomum bicaudatum Kennel, 1889 by Nuttycombe & Waters (1938). This criterion was followed by Noreña-Janssen (1995). However, Marcus (1945b) and Van der Land (1970) recognize the validity of both species.

Marcus (1945b) mentions that the dorsal caudal appendage may be reduced or absent in some specimens.

Figures

Figure 3. A, Stenostomum paraguayense. B, S. rosulatum. C, S. simplex. D, S. tenuicauda. E, S. uronephrium. F, S. virginianum. Scale bars = 200 Mm.