Phagocata pyrenaica Vila-Farré & Sluys, 2011

Vila-Farré, Miquel, Sluys, Ronald, Almagro, Ío, Handberg-Thorsager, Mette & Romero, Rafael, 2011, Freshwater planarians (Platyhelminthes, Tricladida) from the Iberian Peninsula and Greece: diversity and notes on ecology, Zootaxa 2779, pp. 1-38 : 20-23

Phagocata pyrenaica Vila-Farré & Sluys , sp. nov.

( Table 1 , Figs. 3 , 12 A–B, 13A–B)

Material examined. HOLOTYPE. ZMA V.Pl. 6873.2, Font de la O, Aramunt, Lleida, Spain, 11 September 2001, sagittal sections on three slides.

PARATYPES. ZMA V.Pl. 6873.1, ibid., sagittal sections on three slides; V.Pl. 6873.3, sagittal sections on three slides.

Other material. ZMA V.Pl. 6874.1, Font de la O, Aramunt, Lleida, Spain, 20 February 2002, sagittal sections on three slides; V.Pl. 6874.2, ibid., sagittal sections on two slides; V.Pl. 6874., ibid., sagittal sections on two slides; V.Pl. 6874.4, ibid., sagittal sections on two slides; V.Pl. 6875.1, Font Barona, Basturs, Lleida, Spain, 31 March 2007, sagittal sections on two slides; V.Pl. 6875.2, ibid., sagittal sections on three slides; V.Pl. 6876.1, Font Barona, Basturs, Lleida, Spain, 19 July 2009, sagittal sections on three slides; V.Pl. 6876.2, ibid., sagittal sections on two slides; V.Pl. 6876.3, ibid., sagittal sections on three slides; V.Pl. 6877.1, Font de la Figuereta, Pobla de Segur, Lleida, Spain, 24 March 2003, sagittal sections on two slides; V.Pl. 6877.2, ibid., sagittal sections on three slides.

Additional material. Ph. ullala (holotype) V.Pl.859.1, Ebro Delta, March 1993, sagittal sections on two slides.

Etymology. The specific epithet is derived from the Latin word pyrenaicus, of the Pyrenees, in reference to the mountain range from which the specimens were collected.

Diagnosis. With respect to external features, Phagocata pyrenaica can be distinguished from its congeners by its dorsal pigmentation, which is dark brown or absent, depending on the population. The species also differs from its congeners in the following anatomical features: (1) in the proximity of the penis bulb, the vasa deferentia recurve vertically and dorsally, then descend again towards the penis bulb; (2) the ejaculatory duct runs along the ventral wall of the penis papilla; (3) the ejaculatory duct receives the opening of the penis glands, which is most probably erythrophilic, in its distal section.

Description. In its elongated state, the living, sexually mature specimens were up to 8 mm long. Preserved specimens are up to 5.2 x 1.3 mm. In living specimens, the dorsal surface is pigmented dark brown or unpigmented, depending on the population ( Fig. 12 A, B). The frontal margin of the head shows a small protrusion, while the lateral edges of the margin are rounded. Live, active animals have a neck region at the level of the eyes. The hind end of the body is pointed.

The relatively small eyes (eye cup diameter between 40 and 50 µm but only 30 µm in V.Pl. 6873.3) are set in pigment-free patches located far from the frontal margin.

The root of the cylindrical pharynx is situated just after the middle of the body. The pharynx measures between 1/5th and 1/7th of the body length in transparent specimens and about 1/5th of the body length in the black specimen V.Pl. 6876.2. The outer epithelium of the pharynx is underlain by a layer of longitudinal muscle fibres, followed by a layer of circular muscles. The inner epithelium is underlain by a thick layer of circular muscles, followed by a layer of longitudinal muscle fibres. The mouth is situated underneath the copulatory bursa and is connected to the pharyngeal pouch through a canal of variable shape and diameter (100 µm long in V.Pl. 6873.2 and 115 µm in V.P l. 6876.2). In specimen V.Pl. 6874.1 (approximate body length 3.7 mm in sections) the mouth is situated 2.7 mm from the anterior end of the body and 460 µm from the gonopore.

The ventrally located, elongated testes extend from the ovaries to the posterior end of the body, occupying about one-half of the dorsoventral diameter of the body. The oval testes of the black specimens are bigger, and occupy about two-thirds of the dorsoventral diameter in specimen V.Pl. 6876.2. Although the testes are situated mainly ventrally some of them are located in a dorsal position. Some of the ventral follicles may extend dorsally to well beyond the midline of the body.

The vasa deferentia form spermiducal vesicles at the level of the pharynx. In the proximity of the penis bulb, the ducts recurve vertically and dorsally, ascend to the level of the bursal canal in some specimens (V.Pl. 6873.2, V.Pl. 6873.1), then descend again. Shortly after having penetrated the penis bulb the vasa deferentia fuse. The narrow proximal section of the ejaculatory duct runs obliquely towards the ventral surface before it widens and follows its course along the ventral wall of the penis papilla ( Fig. 13 A, B). The duct has a distinctly terminal opening at the tip of the penis papilla. The penis glands, which are most probably erythrophilic, open into the ejaculatory duct in its distal section. The dorsal section of the ejaculatory duct is lined with tall, nucleated epithelium (in specimens V.Pl. 6873.2 and V.Pl. 6876.2), which is underlain by a thick layer of circular fibres. The ventral section is lined with flat, nucleated epithelium, underlain with longitudinal fibres in V.Pl. 6873.2.

The elongated penis papilla has a horizontal orientation ( Fig. 13 A, B). The epithelium of the papilla is underlain by a layer of circular muscle fibres, which is thicker in the dorsal portion, followed by a layer of longitudinal muscle fibres. The weak penis bulb is formed mainly by longitudinal muscle fibres. The male atrium is surrounded by a layer of circular muscle fibres, followed by a layer of longitudinal fibres. The epithelium lining the dorsal section of the male atrium is considerably thicker than in the ventral part.

The ovaries are located a short distance behind the brain and occupy about half of the dorsoventral diameter of the body. The oviducts run from the ovaries backwards to the level of the atrium, where they bend dorsally and, subsequently, unite to form a relatively long common oviduct into which the shell glands open. This common oviduct opens through the posterior wall of the male atrium.

The oval-shaped copulatory bursa is lined with tall, vacuolated cells. The very wide bursal canal runs dorsally to the male atrium ( Fig. 13 A). Near the posterior end of the male atrium the canal curves ventrally to open into the common atrium. The lining epithelium of the bursal canal consists of nucleated cells, surrounded by a subepithelial layer of circular muscle fibres, followed by a layer of longitudinal muscle fibres. In specimen V.Pl. 6873.2, the copulatory bursa occupies almost the entire dorsoventral diameter of the body.

Discussion. Sluys et al. (1995) described two distant populations of Ph. ullala : one in the Ebro Delta (Ullals de Baltasar; holotype and paratypes), and the second in the Pyrenees. Although the specimens collected in the Ullals were fixed well, those from the Pyrenees were not, which resulted in the partial destruction of their tissues (Sluys et al. 1995). Consequently, some of their anatomical features could not be described properly (e.g. the insertion of the penis papilla, and the trajectory of the ejaculatory duct). Both populations were considered to belong to the same species, albeit with some hesitation. The new populations of Phagocata analysed in the present paper were collected in the vicinity of the sampling sites of the animals from the Pyrenees described by Sluys et al. (1995) and their colouration pattern is very similar to that of the specimens collected by these researchers. In addition, they share some common anatomical features, which suggests that the new animals and those collected by Sluys et al. (1995) belong to the same species, viz. Ph. pyrenaica . For example, the size of the eyes (49.5–65 µm in animals in Sluys et al. (1995) and 40–50 µm in the new material), the proportions of the pharynx, and the shape of the penis papilla are very similar. Furthermore, the penis glands open into the distal section of the penis papilla in both groups of specimens.

The only differences between the two populations from the Pyrenees are the meeting point of the vasa deferentia, which is located in the proximal section of the papilla of the animals in Sluys et al. (1995) and just after having penetrated the penis bulb in the new material.

The trajectory of the ejaculatory duct in the Pyrenean specimens was not described by Sluys et al. (1995), but their figures show that it is ventral in two animals and dorsal in a third specimen. In all the recently collected specimens, the ejaculatory duct follows a ventrally displaced course.

In addition, our reexamination of the type material of Ph. ullala deposited at the Zoological Museum Amsterdam (ZMA) uncovered a number of additional species-specific features that were not described by Sluys et al. (1995). First, the ejaculatory duct in all specimens except one (ZMA V.Pl. 860.3, which is immature) is acentral, an important characteristic that was not previously mentioned. After fusion of the vasa deferentia, the ejaculatory duct runs upwards and then curves downwards, following its course to the tip of the penis papilla. In other words, the ejaculatory duct shows a marked bend about half-way during its course through the penis papilla ( Fig. 13 C). Second, the vasa deferentia form marked loops before penetrating the penis bulb (except in the holotype). Third, the penis is inserted into the anteroventral section of the male atrium and, therefore, the papilla has a curious, oblique orientation. Furthermore, a layer of longitudinal muscle fibres is present directly below the layer of circular muscles, underneath the lining epithelium of the penis papilla. Sluys et al. (1995) stated that this layer was absent.

External and anatomical features differentiate Ph. pyrenaica from Ph. ullala . While Ph. ullala presents a brown pigmentation and a mid-dorsal stripe ( Fig. 12 C), this line is absent in animals from the Pyrenees, which are dark brown (almost black) or transparent. The pigment-free area around the pigment cup is usually much bigger in Ph. ullala than in Ph. pyrenaica . Regarding anatomical features, the ejaculatory duct of Ph. ullala follows a curved trajectory through the conical penis papilla, which is ventrally inserted, and does not receive the openings of any glands. However, the ejaculatory duct in Ph. pyrenaica runs a straight and ventrally displaced course and receives the openings of penis glands in its distal section.

Ph. pyrenaica can be distinguished from other members of the genus Phagocata by the anatomy of its copulatory aparatus. Only Ph. mesorchis (Livanov & Zabusova, 1940) is provided with a ventrally displaced ejaculatory duct that runs horizontally and opens at the tip of the penis papilla. However, the ejaculatory duct in Ph. mesorchis is short and has a seminal vesicle, whereas in Ph. pyrenaica the ejaculatory duct is long and there is no seminal vesicle.

Figures

FIGURE 3. Distributional records of twelve species of freshwater planarians in the Iberian Peninsula. Data from De Beauchamp, 1920; De Beauchamp, 1932; Baguñà et al. 1980, 81; Gourbault, 1981; Ribas, 1990; Sluys et al. 1995; Carranza & Giribet, 1997; unpublished records, this study.

FIGURE 12. (A – B) Phagocata pyrenaica, living animal, (A) specimen from a spring near Basturs, dark form, (B) specimen from Font de la O, transparent form, (C) Phagocata ullala, specimen from Ullas de Baltasar (Tarragona, northeastern Spain), living animal.

FIGURE 13. (A – B) Phagocata pyrenaica, holotype, V. Pl. 6873.2, (A) sagittal reconstruction of the copulatory apparatus (anterior to the right), (B) sagittal section of the copulatory apparatus (anterior to the right); (C) Phagocata ullala, V. Pl. 859.1, specimen from Ullas de Baltasar (Tarragona, northeastern Spain), sagittal section of the copulatory apparatus (anterior to the right).