Syndesmis aonikenki, Brusa & Montes & Marcotegui & Martorelli, 2017

Brusa, Francisco, Montes, Martin M., Marcotegui, Paula & Martorelli, Sergio R., 2017, Two new species of Syndesmis (Platyhelminthes, Rhabdocoela, Umagillidae) from the sea urchin Pseudechinus magellanicus (Echinodermata, Echinoidea) in the Southwestern Atlantic Ocean, International Journal for Parasitology: Parasites and Wildlife 6 (2), pp. 54-58 : 56-57

3.2. Syndesmis aonikenki n. sp.

( Figs. 3 — 4 ).

3.2.1. Morphology

Worms 0.74 — 1.56 mm (1.11 ± 0.26, n = 8) long, 0.51 — 0.98 mm (0.75 ± 0.18, n = 8) maximum width at level of middle part of body. Mouth anteroventral, opening into a doliiform pharynx. Pharynx 87.5 — 130 M m (108.54 ± 15.46, n = 12) in diameter ( Figs. 3 and 4 ).

Paired testes on both sides of anterior body midline, slightly lobulated, extending from anterior region of pharynx overlapping vitellaria posteriorly ( Fig. 3 ). Ejaculatory duct close to midline, runs to the posterior body region, and coils posteriorly to the proximal stylet region ( Fig. 4B ); seminal vesicles not observed. Long penis stylet, beginning at funnel-like structure and projecting into male antrum, 105 — 220 M m (148.75 ± 50.22, n = 4) long. Male antrum opening into a common genital atrium. Genital pore at posterior tip of body ( Fig. 4A, C ).

Vitellaria branched, reaching the pharynx region and overlapping with testes, fan-like ( Fig. 4A ). Paired ovaries between vitellaria and filament glands, overlapping posterior vitellaria region. They are lobulated. The bodies of the filament glands are in the latero-posterior part of the body, reaching the posterior vitellaria region. The ducts of the filament glands meet before discharge in the last portion of the uterus.

Vitellaria and ovaries enter a large and wide seminal receptacle at its anterior portion. The lumen of the seminal receptacle narrows posteriorly to form the vagina and connect the common genital atrium ( Fig. 4C ). Without seminal bursa. Uterus ventrally, about 2/3 of the body length. Entry of uterus into common genital atrium ventral to entrances of male antrum and vagina. Filament glands occupying almost whole posterior third of body, almost lateral. Mature egg capsules ovoid, 90 — 125 M m (103.57 ± 12.89, n = 7) long, 57.5 — 100 M m (81.07 ± 16.94, n = 7) wide, brown in color, with a long filament on one pole ( Figs. 3 and 4A ). This filament is straight and thick and then has its distal region threaded ( Fig. 4A ) sometimes thickening at tip.

3.2.2. Etymology

This species is named in honor of the Aonikenk or Tehuelche who lived in the region where this species was found.

3.2.3. Study material

Eight whole mount specimens stained with Gill's Hematoxylin, three specimens cleared in polyvinyl-lactophenol and one specimen serially sectioned at 4- M m thick stained with Masson's trichrome method.

3.2.4. Specimens deposited

The studied specimens have been deposited at the Invertebrate Collection of the Museo de La Plata. Holotype MLP-He 7267, whole mount specimen stained with Gill's Hematoxylin. Paratype MLP-He 7269, whole mount specimen stained with Gill's Hematoxylin. MLP-He 7274, sagittal section specimen stained with Masson's trichrome method .

3.2.5. Localities Bahía Camarones (44 Ǫ 51, 2.09́S, 65 Ǫ 40, 52́W) .

3.2.6. Prevalence of infection 14% (5/36 urchins).

Figures

Fig. 3. Schematic reconstruction of Syndesmis aonikenki n. sp. in dorso-ventral view. Abbreviations:eg, egg; f, filament; fg, filament glands; ov, ovary; st, stylet; t, testes; vit, vitellaria.

Fig. 4. Syndesmis aonikenki n. sp. A, B, whole mount preparations. C, sagittal section of the body. Abbreviations: ed, ejaculatory duct; eg, egg; f, filament; fg, filament glands; i, intestine; ma, male atrium; ov, ovary; sr, seminal receptacle; st, stylet; u, uterus; va, vagina; vit, vitellaria.