Temnocephala mertoni, Volonterio, 2007

Volonterio, Odile, 2007, A new species of Temnocephala (Platyhelminthes, Temnocephalida) and a description of T. axenos from Uruguay, Journal of Natural History 41 (21 - 24), pp. 1245-1257 : 1247-1251

Temnocephala mertoni n. sp.

( Figures 1–5 )

Taxonomic summary

Etymology. The specific name honours Dr Hugo Merton for his contribution to the study of Neotropical temnocephalids.

Type specimens. Holotype: whole mount, deposited in the Helminthological Collection of the Laboratorio de Zoología de Invertebrados , Facultad de Ciencias (Universidad de la República), Montevideo, Uruguay (AP11567) . Paratypes: nine whole mounts and 10 mounts of the reproductive complex, deposited in the same Helminthological Collection (AP11568–AP11586).

Distribution. Type locality: Molles Stream, Route 8, Km 238 (33 ° 36 9 S, 54 ° 35 9 W, Departamento de Lavalleja, Uruguay). Other localities: Colorado Stream, Route 6, Km 35 (34 ° 41 9 S, 56 ° 04 9 W, Departamento de Canelones, Uruguay).

Type host. Aegla platensis Schmitt, 1942 . Deposited in the Invertebrate Collection of the Laboratorio de Zoología de Invertebrados , Facultad de Ciencias (Universidad de la República), Montevideo, Uruguay (BP11001–BP11010) .

Location on host. Ventral surface, coxa of chelae and locomotory legs, and base of antennae and eyes.

Diagnosis. Small temnocephalid; sucker small, peduncle oblique with respect to body surface; elongate excretory syncytia, wider in area surrounding excretory pore; two paranephrocytes; intestine with central constriction not pronounced, and inconspicuous septa; one asymmetrical sphincter in female portion of atrium; eggs with subapical, almost lateral, medium-sized ornamentation, and opercular plates oblique to longitudinal axis of egg; penial stylet about 140 mm long; straight, with distal portion of shaft sinuous; small introvert with about 10 rows of small, distal spines, and a discrete thickening in its wall.

Anatomical description

Temnocephalid of small size; body elliptic with maximum width at equatorial level ( Figure 1 ). Body without tentacles 1260.6 mm (1044.4–1481.5; 142.13; 11) long by 639.1 mm (503.7–733.3; 88.59; 11) wide. Epidermis with elongate excretory syncytia, extending from base of external tentacles to level of anterior portion of intestine ( Figure 2 ). Acetabulum subterminal, 170.4 mm (133.3–200.0; 24.12; 11) long by 185.9 mm (163.0– 214.8; 13.02; 11) wide. Peduncle generally oblique with respect to ventral body surface, with acetabulum directed backwards. Ratio of body length without tentacles to acetabulum length: 1:0.10–0.18 (1:0.14). Ratio of width of same organs: 1:0.26–0.37 (1:0.29). Acetabulum glands anterior to acetabulum, scattered between and posterior to posterior testes ( Figure 1 ). Haswell glands conspicuous, anterior to pharynx ( Figure 1 ). Pharynx 207.4 mm (155.6–244.4; 29.44; 11) long by 238.4 mm (192.6–274.1; 26.67; 11) wide. Intestine wider than long, with slight central constriction and inconspicuous septa ( Figures 1 , 2 ). Tentacular glands abundant, lateral to intestine ( Figure 1 ). Excretory vesicles small, lateral to pharynx; nephridiopores dorsal, situated in a slightly anterior position within the excretory syncytia, close to their internal border ( Figure 2 ). Two paranephrocytes posterior to posterior testes, or dorsal to their posterior portion ( Figure 1 ).

Ovary ovoid. Short oviduct, opens into ootype just behind seminal receptacle ( Figure 3 ). Abundant glandular cells surrounding ootype, with ducts opening into it ( Figure 3 ). Resorbens vesicle in space left by posterior constriction of intestine ( Figure 1 ); ovoid, with anterior side convex, with thin wall, and posterior side flattened and with thicker wall ( Figure 3 ). Ten per cent of the individuals with four small seminal receptacles. The others with an expansion of the wall of the ootype, 56.5 mm (29.0–126.8; 24.16; 15) long by 48.4 mm (27.2–103.3; 18.89; 15) wide, in the same position ( Figure 3 ). Metraterm 74.6 mm (58.0–92.4; 11.94; 15) long by 48.7 mm (38.0–59.8; 6.49; 15) maximum width; distal portion with an asymmetrical sphincter, 44.8 mm (36.2–56.2; 5.91; 15) diameter, 23.2 mm (14.5–29.0; 4.99; 15) maximum thickness, and 14.3 mm (7.2–19.9; 3.55; 15) minimum thickness ( Figure 3 ). Vitelline glands branched, surrounding intestine completely ( Figure 1 ). Eggs 504.5 mm (451.9–548.1; 30.64; 9) long by 237.9 mm (207.4–281.5; 19.75; 9) wide. Ornamentation subapical, almost lateral, of medium size ( Figure 4a ). Opercular plates of medium size, at a certain angle with respect to longitudinal axis of egg, giving an oblique plane of fracture of operculum ( Figure 4a, b ).

Testes slightly lobed; two posterolateral to intestine and two larger, posterior to same organ and more central ( Figure 1 ). Anterior and posterior testes of each side connected by short spermatic ducts. Vas efferens originate on inner portion of posterior testes; right long, left short, enter seminal vesicle adjacent to each other ( Figures 1 , 3 ). Seminal vesicle pearshaped, 130.3 mm (83.3–175.7; 26.00; 15) long by 78.6 mm (43.5–106.9; 21.29; 15) wide; wall 4.7 mm (3.6–5.4; 0.92; 15) thick. Contractile vesicle 108.3 mm (83.3–135.9; 15.41; 14) long by 82.4 mm (54.3–99.6; 13.54; 15) wide; wall 3.5 mm (1.8–5.4; 0.86; 14) thick. Prostatic glands external to contractile vesicle not conspicuous. Penial stylet straight but with distal portion of shaft sinuous in all specimens studied ( Figure 5 ); 138.0 mm (123.2– 157.6; 10.09; 15) long by 46.0 mm (38.0–56.2; 5.55; 15) wide. Introvert 27.2 mm (23.6– 30.8; 2.74; 15) long, 14.1 mm (12.7–16.3; 1.02; 15) maximum width, and 12.3 mm (10.9– 12.7; 0.75; 15) minimum width; with about 10 rows of spines; wall with thickening between proximal end and base of proximal spines ( Figure 5 ). Ratio of body length without tentacles to distance between gonopore and base of tentacles: 1:0.57–0.64 (1:0.61). Gonopore glands surrounding gonopore and ventral to intestine, with conspicuous ducts ( Figure 1 ).

Temnocephala axenos Monticelli, 1899

( Figures 6–10 )

Taxonomic summary

Material examined. Ten whole mounts and 10 mounts of the reproductive complex deposited in the Helminthological Collection of the Laboratorio de Zoología de Invertebrados, Facultad de Ciencias (Universidad de la República), Montevideo, Uruguay (AP11587–AP11606).

Host. Aegla platensis Schmitt, 1942 . Deposited in the Invertebrate Collection of the Laboratorio de Zoología de Invertebrados, Facultad de Ciencias (Universidad de la República), Montevideo, Uruguay (BP11002).

Location on host. Ventral surface, coxa of chelae and locomotory legs, and base of antennae and eyes.

Distribution. Route 8, Km 238 (33 ° 36 9 ’S, 56 ° 35 9 W, Departamento de Lavalleja, Uruguay);

Figures

Figure 1. Holotype of Temnocephala mertoni n. sp. in ventral view. Scale bar: 300 mm.

Figure 2. Excretory syncytia of Temnocephala mertoni n. sp.

Figure 3. Reproductive complex of Temnocephala mertoni n. sp., drawn from a dissected animal. Scale bar: 100 mm.

Figure 4. Eggs of Temnocephala mertoni n. sp. (a) Whole egg, showing ornamentation and opercular plates; (b) hatched egg, showing line of fracture of operculum. Scale bar: 200 mm.

Figure 5. Penial stylet of Temnocephala mertoni n. sp. drawn from a dissected animal. Scale bar: 50 mm.

Figure 6. Temnocephala axenos in ventral view. Scale bar: 300 mm.

Figure 7. Excretory syncytia of Temnocephala axenos.

Figure 8. Reproductive complex of Temnocephala axenos, drawn from a dissected animal. Scale bar: 100 mm.

Figure 9. Eggs of Temnocephala axenos. (a) Whole egg, showing ornamentation and opercular plates; (b) hatched egg, showing line of fracture of operculum. Scale bar: 200 mm.

Figure 10. Penial stylet of Temnocephala axenos drawn from a dissected animal. Scale bar: 50 mm.