Dugesia effusa, 2013

Sluys, Ronald, Solà, Eduard, Gritzalis, Konstantinos, Vila-Farré, Miquel, Mateos, Eduardo & Riutort, Marta, 2013, Integrative delineation of species of Mediterranean freshwater planarians (Platyhelminthes: Tricladida: Dugesiidae), Zoological Journal of the Linnean Society 169 (3), pp. 523-547 : 529-532

DUGESIA EFFUSA SLUYS SP. NOV. ( FIGS 3–5 )

Material examined: Holotype: ZMA V.Pl. 7114.1, river just before opening into the sea, Nagos , Chios, Greece, 38°33′32.31″N, 26°4′59.42″E, 30 April 2010, coll. M. Vila-Farré, sagittal sections on seven slides.

Paratypes: ZMA V.Pl. 7114.2, ibid., sagittal sections on six slides ; V.Pl. 7114.3 (RS 221-3), ibid., horizontal sections on three slides .

Other material: ZMA V. Pl. 7115.1, river, Nagos, Chios, Greece, 38°33′27.57″N, 26°4′51.61″E, 30 April 2010, coll . M. Vila-Farré , sagittal sections on five slides ; V. Pl. 7115.2, ibid., sagittal sections on five slides ; V. Pl. 7115.3, ibid., horizontal sections on three slides .

Etymology: The specific epithet is derived from the Latin adjective effusus, generous, abundant, and alludes to the highly glandularized penis papilla.

seminal vesicle; highly glandularized penis papilla; a bursal canal that widens considerably at its communication with the atrium; ectal reinforcement of the bursal canal confined to the vaginal region.

ph

1 mm

Diagnosis: Dugesia effusa is characterized by the combination of the following features: presence of a small, dorsal penial fold; central ejaculatory duct; short, valve-like diaphragm; large, intrabulbar Ecology and distribution: The species is known only from two sites in the same river, i.e. the type locality close to the opening into the sea and another site further upstream.

Description: Preserved specimens up to 9 × 2.25 mm, with low-triangular head with rounded auricles; tail obtusely pointed ( Fig. 3 ). Dorsal surface pale brown; ventral surface pale. Two eyes, situated in pigmentfree patches.

Pharynx situated in the mid-region of the body, measuring between one-quarter and one-sixth of the body length. Mouth opening located at the posterior end of the pharyngeal pocket.

The testes are located dorsally and extend from the level of the ovaries into the posterior end of the body. The vasa deferentia penetrate the ventro-lateral wall of the penis bulb and open into the seminal vesicle at a point very close to the diaphragm. The ovoid or

bc

vd

100 µm

pear-shaped seminal vesicle fills the major part of the penis bulb and is lined with a columnar, nucleated epithelium. Through a very narrow diaphragm this seminal vesicle opens into the funnel-shaped, proximal section of the ejaculatory duct ( Fig. 4 ). The short, stubby lips of the valve-like diaphragm, as well as the funnel-shaped section of the ejaculatory duct, receive the finely granular and dark red staining secretion of erythrophil penis glands. The broad ejaculatory duct follows a slightly ventrally displaced course through the penis papilla and opens at the blunt tip of the penis papilla, the actual opening being rather narrow. Along the major part of its length the lining epithelium of the ejaculatory duct is pierced by the numerous openings of abundant penis glands that produce an orange–brown secretion.

The plug-shaped penis papilla is lined with a nucleated epithelium and is provided with a subepithelial layer of circular muscles, followed by a layer of longitudinal muscles. A penial fold is located symmetrically at the dorsal base of the penis papilla; the fold is traversed by some longitudinal muscle fibres.

The ovaries are situated directly medially to the ventral nerve cords and are located at one-third to one-quarter of the distance between the brain and the root of the pharynx. The oviducts are lined with an infranucleated epithelium and are surrounded by a well-developed coat of circular muscles. The oviducts open separately into the ventral-most, widened section of the bursal canal, close to the point where the canal communicates with the atrium. Shell glands discharge their secretion into the bursal canal ventrally to the oviducal openings.

The bursal canal is lined with a nucleated, cuboidal-columnar epithelium. The diameter of the bursal canal increases considerably near its point of communication with the atrium. Notably the most ventral section of the canal, at the level of the oviducal openings, shows a widening into posterior direction ( Fig. 5 ). The bursal canal is overlain with a thin layer of circular muscles, the latter being particularly developed in the vaginal region. Ectal reinforcement in the form of outer longitudinal muscle fibres is present in the vaginal area and extends towards the point where the bursal canal bends forwards. The copulatory bursa is a voluminous sac-shaped structure that fills the entire dorsoventral space of the body. In several specimens remnants of a spermatophore are present in the bursa.

Discussion

A dorsal penial fold of similar size and location as in this species D. effusa is present also in D. sagitta (some specimens have only one, dorsal fold), D. malickyi , D. benazzii Lepori, 1951 , D. elegans and D. leporii Pala, Stocchino, Corso & Casu, 2000 . In D. elegans the openings of the vasa deferentia into the seminal vesicle are far removed from the diaphragm, contrasting with the location of the openings immediately anterior to the diaphragm in all other species mentioned. In addition, the penial fold of D. elegans is more developed and more strongly muscular than in D. effusa . (cf. De Vries, 1984).

Dugesia leporii differs from D. effusa in the presence of a pointed diaphragm and small intrabulbar seminal vesicle, and in the fact that its ectal reinforcement extends from the vaginal area far anterior along the bursal canal (cf. Pala et al., 2000). In contrast to D. effusa , D. benazzii is provided with a small intrabulbar seminal vesicle and a pointed diaphragm (cf. Lepori, 1951; De Vries, 1984).

The gross morphology of D. effusa is very similar to that of D. malickyi and D. sagitta . But D. malickyi differs from D. effusa in the presence of (1) a considerably bigger penial fold that also has a distinctly lateral position, and (2) a much narrower and distinctly ventrally displaced ejaculatory duct, the latter being devoid of the high glandularization that occurs in D. effusa . Such a highly glandular papilla, however, is also characteristic of D. sagitta (cf. De Vries, 1984) and also of D. improvisa Sluys & Solà sp. nov. The last-mentioned species lacks the penial fold as well as the widening of the bursal canal in the vaginal area, while its seminal vesicle is highly glandular, in contrast to the conditions in D. effusa .

The GMYC analysis supports D. effusa as a different species ( Fig. 2 , Table 1), clearly delimitating the specimens from Chios as entity 20. Furthermore, D. effusa is not close to D. sagitta in the phylogenetic tree of Solà et al. (2013). Nevertheless, D. effusa shares with D. sagitta the ‘V-shaped’ glandular zone that surrounds the ejaculatory duct (cf. De Vries, 1984: 106). In D. sagitta there are usually two penial folds, the ventral one being smaller than the dorsal one; the ventral fold may also be completely absent. However, in relation to the size of the penis papilla, the penial fold of D. sagitta is considerably bigger than that in D. effusa . Furthermore, the dorsal penial fold of D. sagitta is traversed by a cyanophilic secretion, which is discharged through its lining epithelium; such is not the case in D. effusa .

Figures

Figure 2. Result of the GMYC analysis. Threshold-delimiting speciation and coalescent processes plotted as a broken line. Numbers indicate molecular-based entities; labels correspond to species names. Entities in green show correspondence between the molecular species delimitation method and the morphologically identified species. In orange are shown groupings where there is conflict between morphological and molecular methods. In blue are shown the groupings for which only molecular data are available.

Figure 3. Dugesia effusa Sluys sp. nov. Dorsal view of preserved specimen.

Figures 4, 5. Dugesia effusa Sluys sp. nov. 4. ZMA V.Pl. 7114.2. Sagittal reconstruction of the copulatory apparatus. 5. ZMA V.Pl. 7114.1. Sagittal reconstruction of the copulatory apparatus.