Eutheama forrestensis, Bulnes, Veronica N. & Faubel, Anno, 2003

Bulnes, Veronica N. & Faubel, Anno, 2003, Eutheama forrestensis n. sp. (Acotylea, Polycladida, Plathelminthes) from Australia, Zootaxa 220, pp. 1-8 : 2-5

Eutheama forrestensis n. sp. ( Figs 1 ­3)

Type material: Holotype 4.0 µm sagittally sectioned specimen, mounted on 2 slides, V 13240 . Forrest Beach (18° 42´S; 146° 18´E), Ingham, QLD, Australia, leg. 26th Oct. 1997. Paratype 4.0 µm sagittally sectioned specimen, mounted on 3 slides, V13241 . Forrest Beach (18° 42´S; 146° 18´E), Ingham, QLD, Australia, leg. 26th Oct. 1997.

Additional material collected from Forrest Beach (18° 42´S; 146° 18´E), Ingham, QLD, Australia, leg. 26th Oct. 1997, 1 specimen in squash preparation; Picnic Bay (19° 10´S; 146° 50´E), Magnetic Island, QLD, Australia, leg. Nov. 1997, 2 specimens in squash preparation; Woodgate, (25° 00´S; 152° 50´E), Hervey Bay, QLD, Australia, leg. May 1998, 1 specimen in squeeze preparation.

Etymology. The specific epithet refers to the place of finding, Forrest Beach, Ingham, Australia.

Description. Living specimens are up to 5 mm long and 0.3 mm wide. The fixed specimen (holotype) is essentially shorter (1 mm) and, therefore, with compact appearance. The basic colour is whitish, almost translucent. The body is flattened; tentacles absent. The frontal end is truncated, the posterior one broadly pointed. Frontal eyes present; sexually mature specimens have 12 eyes but juveniles less; eyes are not distributed bilaterally. Four cerebral eyes present and located dorsal of the brain, the others are in the peripheral parenchyme beneath the dorsal body muscle wall forming two irregular rows. The brain is of crescentic outline and 0.2 µm long and 0.15 µm wide (m.h.).

The epidermis is densely packed with short dermal rhabdites, especially the dorsal one. The cilia cover the body entirely, but ventrally the cilia are longer than dorsally. The dorsal and ventral muscle layers of the body differ in size. The dorsal body muscle wall is formed by smooth layers consisting of outer circular and inner longitudinal muscle fibers. The ventral body wall is thicker than the dorsal one, with outer circular muscle fibers, intermitted transversal muscle fibers and inner longitudinal muscle fibers.

The ruffled pharynx lies in mid­body. The pharynx is 140 µm long, only 50 µm short and hangs from the roof of the pharyngeal cavity. The mouth lies ventrally and opens centrally in the pharyngeal cavity. The intestinal trunk extends forwards beyond the cerebral area, and backwards to the ovaries.

The testes ( Fig. 1 ) lie 0.9 mm caudal of the cerebral region. They form bilateral rows extending up to the level of the false seminal vesicles. Each row consists of about 24 testicular vesicles with 18 vesicles anterior and 6 vesicles posterior of the pharynx. Each the vasa deferentia form distally a false seminal vesicle with thin walls. The false seminal vesicles join to a common vas deferens lined with strong circular muscles. Distally the common vas deferens carries out a characteristic twist just before turning into the seminal vesicle.

The male copulatory apparatus ( Fig. 1 B, 2) oriented caudad, consists of a seminal vesicle and an interpolated prostatic vesicle housed in a tube­shaped penis sheath. The seminal vesicle enclosed into a strong muscular wall, is 86 µm long and 30 µm wide (m.h.). Distad the seminal vesicle turns into the prostatic vesicle via a short ejaculatory duct. The prostatic vesicle is enclosed into a strong muscular wall working as penis bulb. The penis bulb is pyriform, 70 µm long (m.h.), 50 µm (m.h.) wide and forms distally an unarmed penis papilla. The inner lining epithelium of the prostatic organ being transversely chambered, is of glandular nature. The glandular cells of which are extravesicular being concentrated proximally around the intervesicular ejaculatory duct ( Fig. 2 ). The penis bulb is housed within a tube­shaped penis sheath, 70 µm long and 60 µm wide (m.h.), and is covered with cilia inside and outside. Distally, the penis sheath is bordered with small papillae discharging fine granulated mucus. The cells of which are located at the base of the penis sheath. The male atrium is lined with a small epithelium. Cilia are absent. Distally, the male atrium joins with the female atrium forming a common genital atrium and gonopore.

The female apparatus oriented anteriad, lies caudal of the male copulatory organs ( Fig. 2 ). The ovary is located in the posterior part of the body and produces only few oogonia (2–3) successively. A walled oviduct leading the oogonia frontad, is not discernable. About 100 µm (m.h.) caudal of the gonopore the proximal female duct widens and forms one globular uterus vesicle. The uterus vesicle is walled by a small aciliated epithelium and give room to only one large oocyte (about 60 µm in diameter; m.h.). Massive cement glands are arranged in front of the uterus surrounding the vagina which is repeatedly branched. The vagina turns into the common genital atrium and communicates with the exterior through the common gonopore.

Figures

FIGURE 1. Eutheama forrestensis n. sp. A, Dorsal view in squash preparation. B, Dorsal view of the male copulatory system. b, brain; ca, common atrium; cg, cement glands; cvd, common vas deferens; e, eye; fsv, false seminal vesicle; i, intestine; o, oocyte; ov, ovary; pap, papillae; pb, penis bulb; ph, pharynx; po, prostatic organ; sv, seminal vesicle; t, testes.

FIGURE 2. Eutheama forrestensis n. sp. Sagittal view of the male and female reproductive organs. bmw, body muscular wall; ca, common atrium; cg, cement glands; cgp, common gonopore; fsv, false seminal vesicle; o, oocyte; pb, penis bulb; po, prostatic organ; ps, penis sheath; rh, rhabdites; sv, seminal vesicle; u, uterus; v, vagina.