Leptoplana mediterranea ( Bock, 1913 ) Gammoudi

Gammoudi, Mehrez & Tekaya, Saïda, 2017, Suborders Acotylea and Cotylea (Polycladida): Study on morphological, ecological and reproductive features of some representative species from Tunisian coasts (Mediterranean), Ecologica Montenegrina 10, pp. 58-70 : 60-61

Leptoplana mediterranea ( Bock, 1913) Gammoudi et al, 2012

Morphological features. The dorsal surface is dull in coloration, yellowish to brownish. Tentacular eyes and cerebral eyes form two dark clusters ( Fig. 1B ). Marginal eyes and tentacles are lacking. Pharynx is ruffled and opens in a mouth located almost in the half of ventral surface. A genital pit typical for the genus Leptoplana is located between the two genital pores. It is a kind of wall ventral depression. In histological sections, it appears as epidermal invagination devoid of muscle layers.

Reproductive features. The whole copulatory apparatus is located in the posterior part of body. Male copulatory apparatus is provided with interpolated tubular prostatic vesicle with a ventral diverticulum. This vesicle communicates with oval shaped seminal vesicle that receives a common sperm duct ( Fig. 3B ). The female apparatus is formed by a vagina that extends dorsally then caudally.

Developmental model. The development is of direct type and the juveniles possess twelve eyes distributed in two groups: four anterior pairs and two posterior pairs. The body is flattened dorsoventrally and completely ciliated ( Fig. 5A ).

Associated fauna. Specimens were found among tunicates Ciona intestinalis (Linnaeus, 1767) and cnidarians Anemonia sulcata (Pennant, 1777) .

Figures

Figure 1. Anterior dorsal region in A: Echinoplana celerrima. See the tentacular (te) and cerebral eyes (ce) forming two paramedian bands, scale bar: 0.5 mm. B: Letoplana mediterranea. See clusters of tentacular (te) and cerebral eyes (ce), scale bar: 0.5 mm. C: Discocelis tigrina. Note the presence of cerebral and tentacular eyes clusters, scale bar: 0.5 mm. D: Imogine mediterranea. Note the presence of two everted nuchal tentacles (arrows), scale bar: 0.5 mm. E: Yungia aurantiaca. See the two marginal tentacles (arrows) and cerebral eyes spots (arrowhead), scale bar: 1 mm. F: Thysanozoon brocchii. Dorsal faces provided with papillae and developed marginal tentacles (arrows), scale bar: 1 mm. G: Prostheceraeus moseleyi. Note the presence of marginal tentacles (arrows) and yellow marginal line, scale bar: mm. H: Prosthiostomum siphunculus. The cerebral eyes (ce) are not included in the semi circle formed by marginal eyes (me), scale bar: 1 mm.

Figure 3. Ovaries in polyclads A: Section through ovary of Echinoplana celerrima showing a ventral growing zone (grz) and a dorsal germinative zone (gmz), scale bar: 0.01 mm. B: Section through ovary of the cotylean Thysanozoon brocchii showing a ventral germinative zone (gmz) and a dorsal growing zone (grz), scale bar: 0.01 mm.

Figure 5. Hatched juveniles and larvae in polyclads A: A twelve eyed juvenile of Leptoplana mediterranea, scale bar: 0.05 mm B: Götte’s larva of Imogine mediterranea: lateral view, scale bar: 0.03 mm C: Müller’s larva of Prosthiostomum siphunculus: lateral view, scale bar: 0.03 mm D: Müller’s larva of Prosthiostomum siphunculus: apical view showing the three eyes (arrowheads), scale bar: 0.03 mm.