Anokkostenostomum, Noreña & Damborenea & Brusa, 2005

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 : 50-54

ANOKKOSTENOSTOMUM GEN. NOV.

Anokkostenostomum anatirostrum (Marcus, 1945) comb. nov. ( Fig. 4A )

Stenostomum anatirostrum Marcus, 1945

Stenostomum bryophilum Luther, 1960

Description: Adult specimens 0.2–0.75 mm long. Chains with two zooids (0.5–1 mm) or six zooids (2.5 mm). Anterior end generally rounded, spatulate or sharply arched with ‘anatiform’ aspect. Constriction before the pharynx. Posterior end rounded. The intestine reaches the caudal body region. Epithelium with short uniform cilia and rigid sensory cilia scattered on the body surface, more numerous in the anterior region. Rhabdites regularly distributed in the adult specimens; but in immature individuals only visible in the ciliated pits. Lateral and broad ciliated pits. Colour in life whitish.

Anterior brain lobes formed by small independent masses (‘metamerics’). No light-refracting bodies.

Oral pore oval, frequently surrounded by radial or longitudinal muscular bundles. Pharynx 1.5–2 times longer than it is wide. Presence of conspicuous transverse muscular bundles. Elongated pharyngeal glands (type b) placed on both sides of the pharynx, grouped in clusters and opening into a simple duct. Immature individuals without pharyngeal glands. Presence of excretophores. Protonephridium slightly sinuous, nephridiopore terminal.

Distribution: São Paulo, Brazil ( Marcus, 1945b); Tvaerminne, Finland ( Luther, 1960); Sabakoekreek, Surinam ( Van der Land, 1970); Cheshire and Yorkshire, England; near Poznan, Poland, and south of Mombasa, Kenya ( Kolasa & Young, 1974a); France ( Lanfranchi & Papi, 1978); Fosso Contesora, Italy ( Kolasa, 1983); south-eastern New York State, USA ( Kolasa et al., 1987; Kolasa, 1991).

Anokkostenostomum corderoi (Marcus, 1945) comb. nov. ( Fig. 4B )

Stenostomum corderoi Marcus, 1945

Description: Solitary individuals, 0.4–0.8 mm long. Two-zooid chains (1.2 mm) to four-zooid chains (2 mm). Body cylindrical, anterior end blunt. Body widening at the level of the oral pore; post-buccal narrowing. Posterior end rounded. The intestine reaches the caudal body region. Small, dorso-lateral ciliated pits; occasionally with creases which make them appear larger. Ciliated epithelium with long semirigid sensory cilia, concentrated especially on the anterior body. The rhabdites are arranged in longitudinal grooves. Live specimens transparent.

Large brain ganglia. Anterior brain lobes separated into small independent masses (‘metamerics’). Posterior lobes with pharyngeal internal and external nerves. No light-refracting bodies.

Oral pore wide, V-shaped, extending to the middle of the pharynx. Pharynx very voluminous (1/3–1/2 of the body length), differentiated into oral (2/3 of its length) and oesophageal regions. A strong sphincter separating the oesophageal region from the intestine. Oral region of the pharynx with scattered large glands (type a) on the musculature. The pharynx is covered by a refringent membrane that broadens at the edges of the mouth. The inner pharyngeal membrane is folded in a zigzag manner in the posterior third of the pharynx (oesophageal region). Intestine with a numerous lateral excretophores, regularly arranged. Nephridiopore terminal .

Distribution: São Paulo, Brazil ( Marcus, 1945b); France ( de Beauchamp 1948).

Anokkostenostomum evelinae (Marcus, 1945) comb. nov. ( Fig. 4C )

Stenostomum evelinae Marcus, 1945

Description: Length of simple specimens, 1.2 mm. Two-zooid chains 2 mm long. Body compact, dorsoventrally flattened. Anterior end rounded. Short lateral ciliated pits placed near the apical end of the body. Posterior end gradually tapering. Ciliated epithelium with long sensory cilia, concentrated mainly in the anterior and posterior ends. Small rhabdites. Colour white, with yellow intestine in live specimens.

Short, compact brain ganglia. Solid anterior lobes and reduced posterior lobes. No light-refracting bodies.

Small oral pore, longer than it is wide, its posterior end widening. Presence of radial musculature. Large, wide pharynx. Well-developed circular and parietal pharyngeal musculature. Strong pharyngeal sphincter. Well-developed pharyngeal glands (type a) in the anterior region. Presence of a caecum dorsal to the pharynx. Lateral excretophores, irregularly arranged in the anterior region, and posteriorly regular. Nephridiopore terminal.

Distribution: São Paulo, Brazil ( Marcus, 1945b); near Paramaibo, Surinam ( Van der Land, 1970).

Anokkostenostomum membranosum ( Kepner & Carter, 1931) comb. nov. ( Fig. 4D )

Stenostomum membranosum Kepner & Carter, 1931

Description: Solitary individuals, 0.5 mm long. Twozooid chains. Fusiform body with tapering ends. The intestine reaches the caudal region of the body. Reduced lateral ciliated pits. No rhabdites. Homogeneous ciliated epithelium, without sensory cilia. Welldeveloped cilia in the ciliated pits. Specimens colourless in life.

Anterior brain lobes larger than the posterior lobes. No light-refracting bodies.

Oral pore axially elongated. Fibrous pharynx. Conspicuous lip sphincter. No pharyngeal glands. No excretophores. Nephridiopore terminal.

Distribution: Virginia, USA ( Kepner & Carter, 1931); São Paulo, Brazil ( Marcus, 1945b).

Anokkostenostomum pegephilum ( Nuttycombe & Waters, 1938) comb. nov. ( Fig. 5A )

Stenostomum pegephilum Nuttycombe & Waters, 1938

Description: Solitary specimens: 0.26 mm long. Chains with two zooids (0.8 mm) up to 5–6 zooids (2 mm). Slight ventral flattening. Anterior end narrowing abruptly. Apical zone blunt. Long ciliated pits. Intestine-lacking region at the posterior end. Conspicuous ciliated epithelium. Irregularly arranged sensory cilia, more abundant in the anterior end. Epidermis with small rhabdites. Colour in life whitish.

The anterior brain lobes form independent masses (‘metameric’). No light-refracting bodies.

Oral pore transverse. Pharynx short, with radial musculature and small rounded glands (type a), which open onto its entire surface. A muscular sphincter separating the pharynx from the intestine. Irregularly arranged excretophores. Conspicuous sinuous protonephridium. Nephridiopore terminal.

Distribution: Mountain Lake, Virginia, USA ( Nuttycombe & Waters, 1938); Tieté River, São Paulo, Brazil ( Marcus, 1945b); Germany, Poland ( Lanfranchi & Papi, 1978); Fosso Contesora, Italy ( Kolasa, 1983); south of New York State, USA ( Kolasa et al., 1987; Kolasa, 1991).

Anokkostenostomum pseudoacetabulum ( Nuttycombe & Waters, 1935) comb. nov. ( Fig. 5B )

Stenostomum stuhlmanni Böhmig, 1897

S. pseudoacetabulum Nuttycombe & Waters, 1935

Description: Adult individuals 0.75–2.5 mm long. Two- to eight-zooid chains. Anterior region elongated. Reduced lateral ciliated pits. Body cylindrical, with a constriction before the mouth and sometimes another constriction at the level of the pharyngeal sphincter. Body tapering caudally. Intestine-lacking region at the posterior end that becomes thinner, forming a typical dorsal appendage. The ciliated epidermis forms a regular cover, except at the posterior end where cilia are scarce. Longer sensory cilia in the posterior region. Epidermis with regular vacuoles and short rhabdites. Colour in life yellowish-white.

The anterior brain lobes differentiate into small independent masses (‘metameric’). No light-refracting bodies.

Oral pore and pharynx resemble a trematode acetabulum, appearing as a body projection in lateral view. The pharynx is posteriorly expanded and forms a cup onto the apical end of the intestine. The mouth and first third of the pharynx can be invaginated, proboscis-like. The pharyngeal glands are uniform (type a) in the whole pharynx. A sphincter between pharynx and intestine. No excretophores. Nephridiopore at the base of the caudal appendage.

Distribution: Georgia, USA ( Nuttycombe & Waters, 1935, 1938; Kolasa, 1991); São Paulo and Paraná State, Brazil ( Marcus, 1945b); near Paramaribo, Surinam ( Van Der Land, 1970); Konin Lakes, Poland ( Kolasa, 1977); Germany ( Lanfranchi & Papi, 1978); Los Talas, Berisso, Buenos Aires, Argentina, February 1999 and February 2000. This species has not been previously recorded in Argentina.

Anokkostenostomum saliens ( Kepner & Carter, 1931) comb. nov. ( Fig. 5C )

Stenostomum saltatum Kepner & Carter, 1931

S. saliens Kepner & Carter, 1931

Description: Solitary individuals 0.15–0.62 mm long. Two- (0.29 mm) or three- (0.54 mm) zooid chains. Anterior and posterior ends noticeably tapering. The intestine reaches the posterior end of body. Small, lateral ciliated pits. Dense ciliated epidermis, long cilia. Thin and rigid longer sensory cilia, irregularly arranged on the whole body. Uniform rhabdites. Yellowish-white colour in life.

Elongated anterior brain lobes, differentiated into small independent masses (‘metameric’); posterior ones voluminous. No light-refracting bodies.

Oral pore large. Two mobile projections at the posterior region of the oral pore. Pharynx somewhat longer than the mouth. Intestine with lobulated edges, ending near the posterior end. No pharyngeal glands. No excretophores. Nephridiopore ventral and terminal.

Distribution: Virginia ( Kepner & Carter, 1931; Nuttycombe & Waters, 1938) and Georgia ( Nuttycombe & Waters, 1938), USA; São Paulo, interior of São Paulo State and Paraná State, Brazil ( Marcus, 1945b); near Paramaribo and near Zanderij, Surinam ( Van Der Land, 1970); Poznan, Poland ( Kolasa, 1973); Los Talas, Berisso, Buenos Aires, Argentina, October 1998, February to March and June to September 1999. This species has not been previously recorded in Argentina.

Discussion: The length of the solitary individuals found by Kepner & Carter (1931) in the USA (0.62 mm) is slightly greater than that recorded for the South American specimens (0.15–0.4 mm).

Anokkostenostomum tuberculosum ( Nuttycombe & Waters, 1938) comb. nov. ( Fig. 5D )

Stenostomum tuberculosum Nuttycombe & Waters, 1938

Description: Chains with two zooids 0.72 mm long. Neither solitary individuals nor longer chains were observed. Anterior end blunt. A small, apparently tactile, tubercle in the ventral cephalic end is characteristic of this species. Small, antero-dorsal ciliated pits. Constriction posterior to the ciliated pits. Intestinelacking region at the posterior end. Densely ciliated ventral epithelium (long cilia). The cilia on the dorsal epithelium are inconspicuous. Semi-rigid sensory cilia irregularly arranged along body. Slender rhabdites. Live specimens yellowish-white, darker at the pharyngeal region because of the presence of glands and musculature. Anterior brain lobes divided into small independent masses (‘metameric’). No light-refracting bodies.

Oral pore V-shaped. Short muscular pharynx associated with elongated unicellular glands (type b), which open onto the whole length of the pharynx. Pharynx with refractory corpuscles. Anterior end of the intestine overlying the posterior part of the pharynx. Intestinal wall dentate. No excretophores. Nephridiopore terminal.

Distribution: Virginia and Georgia, USA ( Nuttycombe & Waters, 1938; Kolasa, 1991); São Paulo and interior of São Paulo State ( Marcus, 1945b), Brazil; margins of the Suriname River near Paramaribo, Surinam ( Van Der Land, 1970); Poznan, Poland ( Kolasa, 1973); Germany, Finland ( Lanfranchi & Papi, 1978); Los Talas, Berisso, Buenos Aires, Argentina, January and April 1999. This species has not been previously recorded in Argentina.

Discussion: Unlike the material found in Argentina, Marcus (1945b) describes chains of up to four zooids (1 mm) for Brazilian specimens. The South American specimens show refractory corpuscles in the pharynx. This feature was not mentioned by Nuttycombe & Waters (1938).

Anokkostenostomum ventronephrium (Nuttycombe, 1932) comb. nov. ( Fig. 5E )

Stenostomum ventronephrium Nuttycombe, 1932

Description: Single individuals, 0.5–0.8 mm long. Three-zooid chains, 2 mm long. Anterior end spatulate. Long lateral ciliated pits. Posterior end without an intestine-lacking region, ending bluntly, no tail. Body uniformly covered with cilia. Semi-rigid cilia, more abundant at both body ends. With epidermal rhabdites. With groups of 10–15 conspicuous rhabdites at the anterior body end. These rhabdites are produced at glands situated latero-dorsally to the pharynx, which have four tracts (two dorsal and two lateral) through which the rhabdites migrate. Whitish, reddish or colourless in life. Brain ganglia with well-developed transverse commissure. No light-refracting bodies.

Oral pore circular, surrounded by muscles. Long, wide, muscular and densely ciliated pharynx. Granular pharyngeal glands (type b), placed mainly ventrally and opening at mouth level. Dorsal wall of the intestine overlying the pharynx. No excretophores. The protonephridium runs dorsal to the pharynx, loops towards the left and continues ventrally or ventro-laterally to the intestine. Nephridiopore subterminal.

Distribution: Virginia, USA ( Nuttycombe, 1932b; Kolasa, 1991); Tieté River, São Paulo, Brazil ( Marcus, 1945a); Italy ( Kolasa, 1983).

Discussion: Differences between the South and North American specimens are: absence of tail and presence of rhabdite-forming glands in the South American specimens ( Nuttycombe, 1932b; Marcus, 1945a).

Figures

Figure 4. A, Anokkostenostomum anatirostrum. B, A. corderoi. C, A. eveline. D, A. membrenosum. Scale bars = 200 Mm.

Figure 5. A, Anokkostenostomum pegephilum. B, A. pseudoacetabulum. C, A. saliens. D, A. tuberculosum. E, A. ventronephrium. Scale bars = 100 Mm.