Stenostomum tenuicauda Graff, 1911

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 : 49

Stenostomum tenuicauda Graff, 1911

( Fig. 3D )

Description: Chains of up to eight zooids up to 5 mm long. Body cylindrical, slightly flattened ventrally. Anterior end blunt. Deep dorso-lateral ciliated pits. Body constriction at the level of the oral pore. Elongated intestine-lacking region at the posterior end (up to one-third of the body length). Caudal portion ventrally adhesive. Long, thin and dense epithelial cilia. Presence of long semi-rigid sensory cilia. Rhabdites grouped in packets placed vertically to the epidermis. Colour in life white.

Anterior brain lobe deeply dentate. Internal brain lobes associated with posterior lobes ( Marcus, 1945a). A pair of type 1 light-refracting bodies formed by numerous spheres (about 50) included into a large vesicle and associated with the posterior ganglia.

Oral pore semi-lunar, surrounded by longitudinal pharyngeal muscles. Pharynx almost as wide as it is long, with little circular musculature. Presence of radial muscles between the pharynx and the body wall. Regularly arranged glands (type a) along the entire pharynx. Intestinal walls smooth. Excretophores irregularly arranged, not very conspicuous. Nephridiopore ventrally placed in the intestinelacking region (subterminal).

Distribution: New York and Massachusetts ( Graff, 1911), Virginia ( Nuttycombe, 1932a; Nuttycombe & Waters, 1938), North Carolina, South Carolina, Tennessee and Georgia ( Nuttycombe & Waters, 1938), USA; São Paulo, Brazil ( Marcus, 1945b); Russia ( Beklemichev, 1917, 1921; Nassonov, 1926); Finland ( Nassonov, 1924); temporary pond near Zapata Stream and Route 11, Buenos Aires, Argentina, November 1999. This species has not been previously recorded in Argentina.

Stored material: Four sagittally sectioned specimens in the CHMLP. No. 5306.

Discussion: S. tenuicauda was synonymized with S. leucops ( Luther, 1960) . However, the differences found not only in the material studied here, but also in the specimens described by Marcus, support the validity of at least the South American populations as a species distinct from S. leucops .

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.