Leptoplana tremellaris (Müller OF, 1773)

Gammoudi, Mehrez, Bulnes, Verónica N. & Kurt, Güley, 2022, The polyclad fauna (Platyhelminthes, Rhabditophora) of the Sinop Peninsula (Black Sea, Turkey) with a description of a new species of Cryptocelis Lang, 1884 Abstract, Mediterranean Marine Science (Hong Kong, China) 22 (1), pp. 141-156 : 153

Leptoplana tremellaris (Müller OF, 1773)

( Figs. 6C and 8D )

Material examined. Five specimens, 22.10.2013, station M1, 5 m deep. Two specimens, 12.05.2014, station M1, 5 m deep. One specimen sagittally sectioned (7 slides).

Description. Body broadly oval, tapering posteriorly. Preserved specimens between 10–22 mm long and 4–10 mm width. Colour pattern lost during fixation. Tentacles lacking, with cerebral and tentacular eyes ( Fig. 8D ). Genital pit present.

Digestive system. Ruffled pharynx arranged in the second third of body; mouth opens in posterior half of pharyngeal pocket. Intestinal ramifications anastomosing.

Reproductive system. Testes are located mainly in ventral parenchyma between digestive ramifications. The paired vasa deferentia run anteriorly, turning then posteriorly joining in a common vas deferens communicating with a pear-shaped seminal vesicle. The interpolated prostatic vesicle tubular, with a well-developed muscular wall. The prostatic diverticulum is arranged ventral to the seminal vesicle. Between the ventral wall of the seminal vesicle and the dorsal wall of the prostatic vesicle´s diverticulum, there is a layer of parenchymatic tissue. Unarmed cirrus present. Male and female gonopores are well separated, arranged in the last third of body. Genital sucker present.

Female gonopore 1 mm behind the genital sucker. The external vagina runs antero-dorsally, surrounded by numerous cement glands, then curves posteriorly where the paired oviduct opens separately. The distal uteri often filled with eggs, extending anteriorly, joining at level of the post cerebral region. Ovaries are located mainly in dorsal parenchyma.

Remarks. Our specimen of Leptoplana tremellaris agrees with the original description of O.F. Müller (1774).

Leptoplana tremellaris and L. mediterranea are externally very similar. Only a histological study of the internal anatomy and the embryonic data provide the specific level of evidence to support the identification of these two species. Specifically, the relation of the seminal vesicle to the prostatic diverticulum (Gammoudi et al., 2012). In L. tremellaris , there is a layer of parenchymatic tissue between the ventral muscular wall of the seminal vesicle and the dorsal muscular wall of the prostatic diverticulum. However, L. mediterranea displays no trace of muscular fibers between the seminal vesicle and the prostatic diverticulum. The ventral margin of the seminal vesicle is separated from the dorsal limit of the prostatic diverticulum by a common layer of cuboidal epithelial cells ( Gammoudi et al. 2012).

Figures

Fig. 6: Sagittal sections of the reproductive system of A, Echinoplana celerrima; B, Leptoplana mediterranea; C, Leptoplana tremellaris. Abbreviations to the figures: cb, cirrus bulb; cg, cement glands; cr, cirrus; ed, ejaculatory duct; mp, male gonopore; ph, pharynx; pv, prostatic vesicle; sv, seminal vesicle; vd, vas deferens. Scale bars: A: 500 µm; B: 200 µm; C: 500 µm.

Fig. 8: Pleioplana okusi. A, sagittal section of the prostatic vesicle; B, sagittal section of the ovary; C-D, sagittal section of the vagina and female atrium. The arrows point the sperm mass. Abbreviations to the figures: ch, tubular chamber of the prostatic vesicle; ed, ejaculatory duct; fg, female gonopore; o, ovary; pi, epidermal pigment; pp, penis papilla; pv, prostatic vesicle. Scale bars: A: 100 µm; B: 50 µm; C: 30 µm; D: 50 µm.