Phagocata graeca 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 : 27-28

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

( Table 1 , Figs. 16 , 17 A–B)

Material examined. HOLOTYPE. ZMA V.Pl. 6879.1, Springs of the River Pamisos in Aghios Floros, Peloponnese, Greece, 0 9 August 2008, sagittal sections on three slides.

PARATYPE. ZMA V.Pl. 6879.2, ibid., sagittal sections on two slides.

Etymology. The specific epithet is based on the Latin adjective Graecus meaning Greek.

Diagnosis. Phagocata graeca sp. nov. can be distinguished from its congeners by (1) oviducts that arise from the ventrolateral side of the ovaries, (2) vasa deferentia that form a loop before penetrating the penis bulb, (3) sections of the vasa deferentia within the penis bulb that are surrounded by a well-developed layer of circular muscle, (4) a rather long common oviduct.

Description. Preserved animals measure up to 4 x 1 mm. The dorsal and ventral surfaces are hyaline. The eyes (maximum eye cup diameter 48 µm, in sections) are located far from the frontal margin ( Fig. 16 ).

The cylindrical pharynx is situated in the middle of the body and measures about 1/6th of the body length. Under the outer epithelium of the pharynx is 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 in the posterior portion of the pharyngeal pocket. In specimen V.Pl. 6879.1, the mouth is situated 1.67 mm from the anterior end of the body and 0.5 mm from the gonopore. The total body length of this specimen is 2.8 mm.

There are two ventral rows of elongated to oval-shaped testes that extend from the ovaries to the posterior end of the body. The follicles occupy about two-thirds of the dorsoventral diameter of the body.

The vasa deferentia increase in diameter at the level of the pharynx, thus forming spermiducal vesicles. At the level of the penis papilla, the sperm ducts curve mediodorsally and, subsequently, recurve and narrow again before penetrating the posterior wall of the penis bulb. Once they have penetrated the penis bulb, the vasa deferentia open separately into the globular seminal vesicle ( Fig. 17 A, B). The ejaculatory duct runs centrally through the penis and opens at the rounded tip of the papilla. The lining epithelium of the ejaculatory duct receives the openings of erythrophilic glands, while its lumen is filled with a spermatophore ( Fig. 17 A, B). The latter consists of three sections. The first is a wide triangular part that fills the anterior part of the seminal vesicle. The second rod-like section of the spermatophore is located in the ejaculatory duct. The third section, situated in the atrium, is wider and irregularly shaped.

Reticulated mesenchymal tissue extends from the penis bulb to the base of the penis papilla. The elongated penis papilla is covered with an epithelium that is thicker on its dorsal section and is underlain by a thick layer of circular muscle fibres, followed by a layer of longitudinal fibres. The hemispherical penis bulb is formed by intermingled longitudinal and circular muscle fibres. In specimen V.Pl. 6879.1, the dorsal section of the male atrium is lined with a very thick epithelium, which is underlain by a thin layer of circular muscle fibres, followed by a thin layer of longitudinal fibres.

The paired, globular ovaries occupy about half of the dorsoventral diameter of the body and are located a short distance behind the brain. The oviducts run dorsally to the ventral nerve cords and are equipped with resorptive vesicles formed by the basal section of the vitellaria. The oviducts curve medio-dorsally at the level of the penis papilla and then unite to form a relatively long common oviduct. The latter opens into the posterodorsal section of the male atrium. The sac-shaped copulatory bursa lies between the hind wall of the pharyngeal pocket and the copulatory apparatus and is lined with tall, vacuolated cells. The bursal canal curves dorsally to the male atrium. The lining epithelium of the bursal canal consists of nucleated cells. The canal is surrounded by a layer of intermingled circular and longitudinal muscle fibres.

Discussion. The combination of external features and the gross morphology of the reproductive system shown by this species resembles only one of the currently known species of Phagocata , viz. Ph. albata Ichima & Kawakatsu, 1962 from North Hokkaido, Japan. However, few chararacters suggest that this species is different from Ph. graeca . The oviducts of the Japanese species arise from the dorsolateral surface of the ovaries, whereas they originate from the ventrolateral side in Ph. graeca . The vasa deferentia do not form a loop in Ph. albata and the common oviduct is rather short, in contrast with Ph. graeca . In addition, the sections of the vasa deferentia within the penis bulb are surrounded by a well-developed layer of circular muscle, which is presumably absent in Ph. albata , although this is not specifically mentioned by Ichima & Kawakatsu (1962). In our experience, these differences and the great geographic distance between sampling localities indicate that these are two different species.

Figures

FIGURE 16. Phagocata graeca, freehand sketch of a preserved specimen from springs of the River Pamisos in Agios Floros, Greece.

FIGURE 17. Phagocata graeca, (A – B), holotype, V. Pl. 6879.1, (A) sagittal section of the copulatory apparatus (anterior to the right), (B) sagittal reconstruction of the copulatory apparatus (anterior to the right).