Planaria torva Muller 1776
Creators: name: Diez, Yander L.
name: Schmidt-Rhaesa, Andreas
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Platyhelminthes
Tricladida
Planariidae
Planaria
Planaria torva

description: Planaria torva (Müller, 1773) Müller, 1776
Fig. 13
Known distribution.
Species broadly distributed in West Europe (United Kingdom, Ireland, Belgium, Finland, Sweden, Denmark, Germany, Greece, France, and Italy) (Arndt 1926; Luther 1961; Ronneberger 1975; Ball and Reynoldson 1981; Müller and Faubel 1993; Martin and Brunke 2012), East Europe (Estonia, Latvia, Littauen, Ukraine, Poland, and Czech Republic) (Luther 1961; Pinchuk 1979), and Russia (Grimm 1877; Luther 1961).
Material.
Six specimens studied alive and preserved in absolute ethanol for future molecular analyses; one collected in Wandse river, submerged vegetation with organic matter, 0.1 m deep; one in Planten un Blomen park, submerged litter, 0.3 m deep; and four in Kirchwerder-Fünfhausen, submerged vegetation and litter in an irrigation channel, 0.1–0.2 m deep.
Remarks.
Live adult specimens measuring 0.5–1.5 cm, dark pigmented, with a pair of anterior eyes (Fig. 13 A – C: e). Squeezed specimens show the pharynx and atrial organs. The pharynx (Fig. 13 C, D: ph) is located in the second body half and the mouth opens anterior to the male copulatory organ (Fig. 13 A, C, D: mco). The seminal ducts form false seminal vesicles (Fig. 13 A, C, D: fsv) beside the anterior part of the pharynx. The male copulatory organ receives medially, independently, both seminal ducts, which evacuate the sperm in a single proximal seminal vesicle. Distally, the bulb forms a muscular penial papilla. One adenodactyl (Fig. 13 C, D: ad) opens into the common atrium, at the right side of the male bulb; it is oriented backwards. The adenodactyl is distally bent and the central lumen makes it look hollow. The single observed structure of the female system was the bursa (Fig. 13 D: b), located to the right side of the male organ.
Planaria torva is a species widely distributed throughout West Europe, and it is frequently mentioned in taxonomic literature on triclads in the region. However, accurate identification of this species can be challenging without a detailed examination of internal morphology. The taxonomic history of P. torva has been contentious, with several studies mistakenly associating it with species of Dugesia (Ball et al. 1969). In light of these issues, we based the identification of our specimens on descriptions provided by Luther (1961) and Ball et al. (1969). The presence of an adenodactyl serves as a key distinguishing feature between our studied specimens of P. torva and species of Dugesia (Luther 1961). Furthermore, the overall structure of the atrial organs in our specimens, particularly the male bulb and the adenodactyl, unequivocally supports their classification within P. torva. For a more comprehensive comparison of this species with related congeners, refer to Ball et al. (1969).
description: Published as part of Diez, Yander L. & Schmidt-Rhaesa, Andreas, 2024, Little neighbours in Hamburg: free-living aquatic flatworms (Platyhelminthes), pp. 279-310 in Evolutionary Systematics 8 (2) on pages 279-310, DOI: 10.3897/evolsyst.8.139468