Phagocata asymmetrica 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 : 15-17

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

( Table 1 , Figs. 3 , 10A–D)

Material examined. HOLOTYPE. ZMA V.Pl. 6869.1, Spring in Carneros, León, Spain, 20 April 2009, sagittal sections on three slides.

PARATYPES. V.Pl. 6869.2, ibid., sagittal sections on three slides; V.Pl. 6969.3, ibid., sagittal sections on two slides; V.Pl. 6869.4, ibid., sagittal sections on three slides; V.Pl. 6869.5, ibid., sagittal sections on three slides.

Etymology. The specific epithet is derived from the Greek word symmetria, symmetrical, and alludes to the asymmetrical course of the two vasa deferentia.

Diagnosis. Anatomically, Phagocata asymmetrica sp. nov. is characterized by (1) the asymmetrical course of the vasa deferentia, in which only one of the sperm ducts forms a loop before penetrating the penis bulb, (2) vasa deferentia openings into the intrabulbar cavity that are located on opposite sides, (3) an ejaculatory duct that receives two types of glandular secretion: the first a fine-grained, erythrophilic secretion; and the second an equally fine-grained, cyanophilic secretion.

Description. In its elongated state, living, sexually mature specimens measure up to 8 mm long and approximately 1 mm wide. The dorsal body surface presents a dark brown pigmentation (Fig. 10A), except for the margins, which can be hyaline in some specimens. The head is truncated, with slightly rounded lateral edges of the margin and a very small protrusion in the midline. After the level of the copulatory apparatus, the body tapers to a pointed tail. The eyes (eye cup diameter 38 µm in V.Pl. 6869.3 and 46 µm in V.Pl. 6869.2 (in sections)) are set in pigment-free patches, which are located far from the frontal margin and lie close together at a distance of 1/7th to 1/ 9th of the width of the head in living specimens.

The cylindrical pharynx is situated in the middle of the body and measures about 1/6th of the body length in specimen V.Pl. 6869.1. 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 very thick layer of circular muscles, followed by a layer of longitudinal muscle fibres. The mouth is situated in the posterior portion of the pharyngeal pocket and opens to the exterior underneath the copulatory bursa. In specimen V.Pl. 6869.1 (approximate body length 3.6 mm in sections), the mouth is situated 2.5 mm from the anterior end of the body and 480 µm from the gonopore.

There are two rows of oval-shaped testes that extend from the ovaries to the posterior end of the body and occupy about half of the dorsoventral diameter. Although the testes are mainly situated ventrally, some follicles may extend dorsally to well beyond the midline, especially in the anterior part of the body, where they can be numerous.

The vasa deferentia form very large spermiducal vesicles at the level of the pharynx. In the proximity of the penis papilla, one of the vasa deferentia curves dorsally, recurves and narrows before it penetrates the posterolateral wall of the penis bulb. The other vas deferens does not form a loop and enters the penis bulb through its base. Subsequently, it opens into the proximal, anterior section of a small, rounded intrabulbar cavity (10B). The openings of the vasa deferentia into this intrabulbar cavity are located on opposite sides. The wide and straight ejaculatory duct is lined with nucleated epithelium and surrounded by a thin layer of circular muscle fibres, followed by a layer of longitudinal fibres. The ejaculatory duct runs centrally through the penis papilla and receives two types of glandular secretions. The first is a fine-grained, erythrophilic secretion in its proximal section, which is produced by glands that lie in the penis bulb. The second secretion is fine-grained and cyanophilic. It is discharged into the distal section of the duct (Fig. 10C, D).

The epithelium of the penis papilla is underlain by a layer of circular muscle fibres, followed by a layer of longitudinal muscle fibres. The small penis bulb is mostly formed by longitudinal muscles and only a few circular muscle layers. The male atrium is lined with thick epithelium (especially in its dorsal part), surrounded by a layer of circular muscle fibres, followed by a layer of longitudinal fibres.

The ovaries are located a short distance behind the brain and occupy about one-third of the dorsoventral diameter of the body.

The oviducts run dorsally to the ventral nerve cords and curve dorsally at the level of the penis papilla, where they unite to form a common oviduct. The latter opens into the posterodorsal section of the male atrium. The distal section of the oviducts and the common oviduct receive the openings of abundant shell glands (Fig. 10B). The large sac-shaped copulatory bursa is lined with tall, vacuolated cells. The curved bursal canal runs dorsally to the male atrium. Near the posterior end of the male atrium, the canal curves ventrally to open into the common atrium. The lining epithelium of the wide bursal canal consists of nucleated cells surrounded by a subepithelial layer of circular muscle fibres, followed by a thin layer of longitudinal muscular fibres.

Discussion. The gross morphology of the copulatory apparatus of Ph. asymmetrica resembles that of a large number of species of the genus Phagocata s. s., which currently lacks any defining, apomorphic features to support its presumed monophyletic status (Sluys, 1995). Phagocata asymmetrica stands apart from its congeners, due to the different course of the vasa deferentia, in which only one sperm duct markedly loops before penetrating the penis bulb. However, in many species the course of the vasa deferentia has only been cursorily studied or not studied at all. Therefore, we will concentrate on other aspects of its morphology.

We only compare pigmented species, all of which possess eyes. There are six pigmented species in Europe: Ph. armeniaca (Komárek, 1916) , Ph. maculata (Stankoviċ, 1938) , Ph. ullala and Ph. woodworthi Hyman, 1937 . Phagocata armeniaca has a ventral diverticulum in its ejaculatory duct, whereas Ph. asymmetrica has no such structure. The testes in Ph. maculata extend throughout the entire dorsoventral diameter of the body, and the oviducts have accessory seminal vesicles. In contrast, the testes in Ph. asymmetrica are smaller and accessory seminal vesicles are absent. The ejaculatory duct in Ph. ullala follows an acentral course through the penis papilla, whereas it is central in Ph. asymmetrica . Phagocata woodworthi (introduced in Loch Ness from North America; cf. Reynoldson et al. 1981) is a polypharyngeal species, whereas Ph. asymmetrica is monopharyngeal.

There are twenty pigmented species outside Europe. Phagocata bulbosa Kenk, 1970 , Ph. gracilis (Haldeman, 1840) , Ph. kawakatsui Okugawa, 1956 , Ph. teshirogii Ichikawa & Kawakatsu, 1962 , and Ph. virilis Kenk, 1977 all have a very slender and elongated penis papilla, whereas that of Ph. asymmetrica is more cylindrical and considerably thicker.

In Ph. fawcetti Ball & Gourbault, 1975 , Ph. papillifera (Ijima & Kaburaki, 1916) , and Ph. suginoi Kawakatsu, 1974 the common oviduct is enlarged and always much bigger than in Ph. asymmetrica . The penis papilla is pointed in Ph. iwamai Ichikawa & Kawakatsu, 1962 , whereas it is blunt in Ph. asymmetrica .

Ph. sibirica (Zabusov, 1903) and Ph. vivida (Ijima & Kaburaki, 1916) have distinct auricles, which are absent in Ph. asymmetrica . Phagocata crenophila Carpenter, 1969 and Ph. fontinalis (Zabusov, 1903) have an asymmetrical penis papilla, whereas the penis papilla of Ph. asymmetrica is symmetrical. Phagocata miyadii Okugawa, 1939 has a small common vas deferens, whereas such a structure is absent in Ph. asymmetrica . In Ph. nordeni Kenk, 1977 the bursal canal is extremely wide, whereas in Ph. asymmetrica it is narrower. Phagocata uenoi Okugawa, 1939 has 4–8 eyes on each side of the head, contrasting with the two eyes (one on each side) of Ph. asymmetrica . Regarding anatomical features, the penis bulb in Ph. uenoi is very large, whereas it is much smaller in Ph. asymmetrica . In Ph. velata (Stringer, 1909) the testes are dorsal and the ejaculatory duct shows a ventral diverticulum. In contrast, the testes in Ph. asymmetrica are ventral and there is no ventral diverticulum. Phagocata vernalis Kenk, 1944 is a protandrous species with a large and pointed penis papilla, in contrast to Ph. asymmetrica . In Ph. tahoena Kawakatsu, 1968 the epithelium of the bursal canal is very tall and there is no intrabulbar cavity, whereas in Ph. asymmetrica the epithelium of the bursal canal is less tall and there is a small, rounded intrabulbar cavity. Differences between Ph. woodworthi and Ph. asymmetrica were detailed above.

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.