Phagocata flamenca 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 : 12-15

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

( Table 1 , Figs. 3 , 8 A–D, 9A–B)

Material examined. HOLOTYPE. ZMA V.Pl. 6868.1, Fuente de Don Pedro, Loja, Granada, Spain, 20 April 2009, sagittal sections on five slides.

PARATYPES. V.Pl. 6868.2, ibid., sagittal sections on four slides; V.Pl. 6868.3, ibid., horizontal sections on three slides.

Etymology. The specific epithet alludes to the great resemblance of the animal’s undulated body margins to the ruffles of a flamenco dancer’s dress. Moreover, the specimens were collected from Andalucía, a region in which Flamenco is the traditional dance.

Ecology. A large number of individuals were found under small stones in the well of an artificial spring, which receives water from irrigation channels and has three spouts that flow continuously. The depth of the well was about 20 cm and the water conditions were as follows: temperature: 15ºC; conductivity 610 µs at 15ºC (502 µs at 25ºC).

Diagnosis. With respect to external features, Phagocata flamenca sp. nov. can be distinguished from its congeners by its exceptionally undulated body margin and by the characteristic and very wide shape of the frontal margin of the head during locomotion. Anatomically, the species is characterized by an ejaculatory duct that lacks a plug of cells and receives the opening of two types of glands, one that is cyanophilic and fine-grained, and one that is formed from coarse, erythrophilic granules.

Description. Completely extended living specimens are about 10.5 mm long and 3 mm wide; preserved animals measure up to 9 x 3.3 mm. The dorsal surface is brown ( Fig. 8 A) and a broad lateral margin of the body, which is about 0.4 mm wide, is unpigmented. In the middle of the body, at the pharynx level, the colour is pale brown due to a reduction of pigmentation.

The body margin is exceptionally undulated. The undulations are even more prominent when the animal retracts its body during locomotion or when specimens are preserved ( Fig. 8 B). There are about 8–12 wave-like curves or folds on each side, depending on the size of the animal. A narrow, pigmented line, consisting of 7–8 spots, surrounds each of the folds. The ventral surface is devoid of pigment.

A narrowing or “neck” is present at the level of the eyes and the tail is pointed. During locomotion, the frontal margin of the head shows a characteristic and very wide shape with a small protrusion in the midline, while the lateral edges of the margin are rounded. During the usual gliding motion, the head may also show lateral protrusions that are raised from the substrate and make twisting and turning movements, with the midline of the frontal margin being either sharply V-shaped or showing a shallow V-shaped depression ( Fig. 8 C).

The eyes are set in pigment-free patches (maximum eye-cup diameter 52–58 µm in specimen V.Pl. 6868.1 (in sections)), located far from the frontal margin. The number of retinal cells in each pigment cup could not be determined with certainty, but there are probably more than ten in specimen V.Pl. 6868.2.

The cilia of the nucleated epidermis are uniformly distributed on the ventral epidermis but not on the dorsal epidermis, which is formed by ciliated and non-ciliated cells.

The cylindrical pharynx is situated in the middle of the body and measures about 1/5th of the body length. 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 ( Fig. 8 D). The mouth is situated in the posterior portion of the pharyngeal pocket and opens to the exterior underneath the copulatory bursa ( Fig. 9 A, B). In specimen V.Pl. 6868.1, the mouth is situated 310 μm from the anterior end of the body and 510 μm from the gonopore.

There are two rows of large irregularly-shaped testes extending from the ovaries to the posterior end of the body, and the follicles occupy about two-thirds of the dorsoventral diameter. Although they are principally ventral, some follicles may extend dorsally to well beyond the midline, especially in the anterior part of the body.

In the proximity of the penis papilla, the vasa deferentia widen considerably, curve dorsally and, subsequently, recurve and narrow again before they penetrate the lateral wall of the penis bulb ( Fig. 9 A, B). Once they have penetrated the penis bulb, the vasa deferentia open separately into the ejaculatory duct. The ejaculatory duct runs centrally and opens at the rounded tip of the penis papilla. This duct is lined with thick, nucleated epithelium into which the two types of glands open. The first type of gland produces a pale, cyanophilic and fine-grained secretion that is discharged into the central section of the ejaculatory duct. The second kind of secretion is also produced by glands that lie outside of the penis papilla and is discharged into the distal section of the duct. This secretion is very abundant and consists of coarse, erythrophilic granules ( Fig. 9 A, B).

Abundant glandular secretion is present throughout the mesenchyme of the penis papilla. The penis papilla is covered with thin epithelium that is underlain by a layer of circular muscle fibres. The hemispherical penis bulb is formed mostly by longitudinal muscles, with only a few circular muscle layers. In specimen V.Pl. 6868.1, the dorsal section of the male atrium is lined with thick epithelium that is underlain by a thin layer of circular muscle fibres, followed by a thin layer of longitudinal fibres.

The paired, globular ovaries occupy about one-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 curve dorsally at the level of the penis papilla, where they unite to form a common oviduct. This opens into the posterodorsal section of the male atrium. Shell glands discharge into the common oviduct. The large, rounded copulatory bursa lies between the hind wall of the pharyngeal pocket and the copulatory apparatus. It is lined with tall, vacuolated cells, which have nuclei mainly in a basal position and vacuoles in the apices. The bursal canal curves dorsally to the male atrium ( Fig. 9 B). The lining epithelium of the wide bursal canal bears distinct cilia and consists of nucleated cells surrounded by a subepithelial layer of circular muscle fibres, followed by a thin layer of longitudinal muscle fibres.

Discussion. There is only one other species of freshwater planarian that has the same characteristic wave-like folds as Ph. flamenca on its body margin: Phagocata undulata (Stankoviċ, 1960) from Lake Ohrid. In Ph. undulata “The lateral margins of the body are thrown into almost regular, wave-like curves and folds...” and the body “... margin has a row of short conical papillae” ( Kenk, 1978). Although the body margin is also folded in Ph. flamenca , the conical papillae are absent. Regarding anatomical features, the vasa deferentia in Ph. undulata penetrate the weak penis bulb from a medial direction, the penis papilla is conical, and the penis bulb lacks any reticulated tissue. In contrast, the vasa deferentia in Ph. flamenca penetrate the penis bulb after a marked recurvature, the penis papilla is blunt, and the penis bulb presents a zone of reticulated tissue that is absent in Ph. undulata . Furthermore, the proximal part of the ejaculatory duct in Ph. undulata is filled by a plug of cells, which is absent in Ph. flamenca . The distal section of the ejaculatory duct of Ph. undulata is usually somewhat widened and lined with taller epithelium, in contrast to Ph. flamenca . In addition, the dorsal surface in Ph. undulata is covered with an epithelium that lacks cilia ( Kenk, 1978), which contrasts with the dorsally ciliated epidermis of Ph. flamenca .

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 8. Phagocata flamenca (A – D) specimens from “ Fuente de Don Pedro ” (Loja), (A) living animal, (B) preserved specimen, (C) freehand sketch of a live specimen in movement, (D) diagrammatic transverse section through the pharynx, showing the arrangement of the rows of longitudinal and circular muscles.

FIGURE 9. Phagocata flamenca. Holotype V. Pl. 6868.1, (A) sagittal section of the copulatory apparatus (anterior to the left), (B) sagittal reconstruction of the copulatory apparatus (anterior to the left).