Leptoplana tremellaris (Muller, 1774) Orsted 1843
Creators: name: Gammoudi, Mehrez
name: Garbouj, Myriam
name: Egger, Bernhard
name: Tekaya, Saïda
Publisher: name: Zenodo
Year: 2017
Subjects: Biodiversity
Taxonomy
Animalia
Platyhelminthes
Rhabditophora
Polycladida
Leptoplanidae
Leptoplana
Leptoplana tremellaris

description: Leptoplana tremellaris (Müller, 1774) Örsted 1843
(Fig. 2 b, Fig. 3 a–i)
We report this species for the first time from the Mediterranean sea, so we give its description below.
Habitat. 5 specimens were found under stones.
Locality. Errimel beach (36° 52' 25.87"N; 10° 39' 57.06" E).
Other localities in the world. The North Sea (Müller 1773; Bock 1913); Scotland (Fleming 1823); Belgium (van Beneden 1860); Saint Malo, France (Keferstein 1868); the Irish Sea (Gamble 1893a); the Isles of Scilly (Faubel & Warwick 2005); Atlantic Spanish coasts (Marquina et al. 2014b).
Description. The body is oval in shape. It measures 15 mm in length by 4 mm in width, the anterior end being broader than the posterior. Dorsal surface is beige (Fig. 2 b). Digestive ramifications could be easily seen. Tentacles are lacking. Two clusters of cerebral and tentacular eyes are present (Fig. 3 a,b). Ventral surface shows a ruffled pharynx located at the second third of body, two vasa deferentia filled with sperm and two uteri filled with eggs (Fig. 3 b,e). A genital pit is located between male and female gonopore and closer to the latter (Fig. 3 c). The epidermis is provided with several rhabdites (Fig. 3 d). The pharynx is provided with 12 pairs of lateral folds. The mouth is situated at the hind end of the third fifth of the body and in the third fourth of the pharyngeal cavity. Immediately behind the posterior end of the pharyngeal chamber lies the male copulatory apparatus. The male genital pore opens to a narrow extended male atrium and is provided with a diverticulum oriented dorsally (Fig. 3 f). The ejaculatory duct leads to a narrow tubular prostatic vesicle. The latter vesicle is of interpolated type and was observed to contain some eosinophilous secretions (Fig. 3 f,g,h). Its internal glandular lining is smooth and is connected to a seminal vesicle, usually filled with sperm (Fig. 3 g,h). Before entering the seminal vesicle, the tubular prostatic vesicle gives birth to a diverticle lying below the seminal vesicle (Fig. 3 g,h). A muscular tissue is separating the two organs. The female genital pore, situated behind the male one, leads to a short external vagina directed dorsally followed by a large median vagina oriented fronto-dorsally (Fig. 3 i). Before reaching the dorsal body wall, the vagina curves posteriorly to form an internal horizontal portion corresponding to the internal vagina. Anteriorly, this part does not exceed the level of projection of the female genital pore.
Remark. The genus Leptoplana Ehrenberg was thoroughly revised by Gammoudi et al. (2012b). The authors deduced and supported the idea that the unique representative of the genus Leptoplana in Mediterranean area is Leptoplana mediterranea (Bock 1913). This was confirmed by Marquina et al. (2014a).
Leptoplana mediterranea shows clear similarity with Leptoplana tremellaris. Externally both species are almost impossible to separate (Gammoudi et al. 2012b). The study of sections of specimens from Tunisia and sections of Leptoplana tremellaris from Scilly Islands (English channel) made by Faubel (1983) and also sections of specimens of L. mediterranea from Tunisia, allowed us to find some features distinguishing L. mediterranea from L. tremellaris. In L. mediterranea we found 1) The presence of a genital pit nearer to the male pore and not to the female one. 2) The seminal vesicle is of oval shape. 3) The ventral diverticulum of the prostatic vesicle presents a common dividing wall with the seminal vesicle. 4) The hatched juvenile is provided with twelve eyes.
In contrast, in L. tremellaris of Faubel (1983) and new material from Tunisia we found: 1) The genital pit is closer to the female pore than to the male one (Fig. 3 c). 2) The seminal vesicle is pear shaped (Fig. 3 g, h). 3) Muscle and mesenchyme are surrounding the prostatic vesicle (Fig. 3 g, h). 4) The hatched juvenile is provided with two pairs of eyes (Fig. 2 n,o).
Based in these data, we considered the similarity of our new specimens with those of Faubel and also the difference between our specimens and specimens of Leptoplana mediterranea to be substantial enough to determine Leptoplana tremellaris from Tunisian waters and thus to report this species for the first time from the Mediterranean sea, since L. tremellaris was considered to be missing in the Mediterranean by Gammoudi et al. (2012b).
description: Published as part of Gammoudi, Mehrez, Garbouj, Myriam, Egger, Bernhard & Tekaya, Saïda, 2017, Updated inventory and distribution of free-living flatworms from Tunisian waters, pp. 120-138 in Zootaxa 4263 (1) on pages 124-125, DOI: 10.11646/zootaxa.4263.1.5, http://zenodo.org/record/572567