Microplana gadesensis, Vila-Farré, Miquel, Mateos, Eduardo, Sluys, Ronald & Romero, Rafael, 2008

Vila-Farré, Miquel, Mateos, Eduardo, Sluys, Ronald & Romero, Rafael, 2008, Terrestrial planarians (Platyhelminthes, Tricladida, Terricola) from the Iberian Peninsula: new records and description of three new species, Zootaxa 1739, pp. 1-20 : 11-13

Microplana gadesensis sp. nov.

Material: Holotype, CRBA 443, CRBA 444, Llano del Berral (lat. 36.75428, long. -5.45399; alt. aprox. 657 m) in the central part of the Sierra de Grazalema, Cádiz ( Spain), 5 December 2004, sagittal sections on 2 slides. This specimen was accidentally broken in two pieces while it was being embedded in paraffin. Paratype: CRBA 445, ibid., sagittal sections on 1 slide.

Diagnosis. Microplana gadesensis sp. nov. can be distinguished anatomically from its congeners by a muscular penis bulb provided with a very thick layer of circular muscle fibres, rounded bulbar lumen, large penis papilla provided with a wide ejaculatory duct, genito-intestinal duct that links the female genital duct to the gut, and absence of a copulatory bursa.

Ecology and distribution. The species is known only from the type locality.

Etymology. The specific epithet is based on the name of the region where the specimens were collected, Cádiz, named Gades in Latin, in southern Spain.

Description. When the animals were fixed in the field and later prepared for sectioning, they were considered to be morphologically similar to M. grazalemica , and therefore no particular attention was paid to their external features. It may be assumed that their external appearance did not differ much from that of M. grazalemica . From the sections of the holotype it could be determined that the animal was about 10 mm long.

The two small eyes (eye cup diameter 16 µm in sections) are located at a short distance in front of the brain ( Fig. 6 ) and are only clearly visible under observation through a dissecting microscope.

The subepidermical longitudinal fibres of the body musculature weak. In the ventral body region numerous strong parenchymal longitudinal fibres are present especially dorsally and ventrally of the ventral nerve cords. This ventral musculature becomes especially strong at the cephalic region, where it attaches at the epithelium of an invaginated area ( Fig. 6 ). This longitudinal musculature partially encloses the eyes.

The short pharynx is about one-twelfth of the total body length (0.3 mm), its root being located slightly posterior to the middle of the body. The outer epithelium is ciliated from the root to the tip of the pharynx. It is underlain by a thin layer of longitudinal muscles followed by a thin layer of circular muscles. The inner epithelium of the pharynx is underlain with a very thick outer layer of circular muscles, followed by a longitudinal muscles layer, the latter in some areas intermingled with the circular layer. In specimen CRBA445 the mouth is situated close to the posterior wall of the pharyngeal pouch at 2.5 cm from the tip of the body and 0.9 mm from the gonopore.

The number of elongated testes varies from four (CRBA445) to six (CRBA443-444) on either side of the body. The follicles occupy approximately one-fourth of the dorso-ventral diameter and are arranged in longitudinal rows, extending from some distance behind the ovaries to the root of the pharynx.

The penis bulb is provided with a rounded bulbar lumen, leading to a very wide ejaculatory duct that runs centrally through the penis papilla and gradually narrows before opening at the tip of the papilla ( Fig. 7 A). The bulbar lumen and the ejaculatory duct are lined with a nucleated epithelium. The bulbar lumen is surrounded by a thick layer of circular muscle fibres that extends on the proximal part of the penis papilla; this coat of circular muscle is highly developed on the ventral side of the seminal vesicle.

The large and elongated penis papilla is highly muscular; it is oriented parallel to the body surface. At the level of the penis bulb, the two vasa deferentia turn dorsally and open separately into the anterior portion of the bulbar lumen.

The penis papilla projects into the female genital atrium. The gonopore opens into the mid-ventral section of the atrium.

The small ovaries occupy one-fifth of the dorso-ventral diameter, lying on top of the ventral nerve cords. The ovaries are located at approximately one-sixth of the distance between the brain and the root of the pharynx. The oviducts arise from the ventral side of the ovaries. The rather narrow female genital duct is provided with distinct cilia and receives the openings of the oviducts at its posterior end. The duct is lined with nucleated epithelium that is underlain with a thick, subepithelial layer of circular muscles followed by a layer of longitudinal muscle fibres. The female genital duct of specimen CRBA445 receives the openings of the shell glands anteriorly to the openings of the oviducts. Secretion granules are present in the same area in the holotype, but not the glands itself. A long genito-intestinal duct arises from the distal end of the female genital duct ( Fig. 7 B) and immediately recurves to run approximately parallel to the dorsal wall of the atrium, subsequently communicating with the gut. The genito-intestinal duct is lined with a ciliated epithelium and is surrounded by a layer of circular muscles ( Figs. 8 A, B).

The wall of the elongated atrium is lined with a thin epithelium, provided with a thin circular muscular layer, surrounded by a thin longitudinal layer of muscles.

Discussion. Microplana gadesensis can be distinguished from the other known native European land planarians species by the anatomy of its copulatory apparatus.

Regarding the external features, similar body colouration is found in M. nana and M. grazalemica . However, M. nana and M. grazalemica lack a genito-intestinal duct and also the thick layer of circular muscle fibres around the bulbar lumen.

Among the known European species of Microplana a genito-intestinal duct has been reported also for M. humicola , M. pyrenaica , M. howesi (Scharff, 1900) , M. giustii Minelli, 1976 , M. henrici (Bendl, 1908) , M. attemsi (Bendl, 1909) , M. peneckei (Meixner, 1921) , M. scharffi (von Graff, 1899), M. monacensis ( Heinzel, 1929) , and M. terrestris . However, M. humicola presents a hyaline colouration ( Schneider, 1935), instead of the pigmented dorsal colouration pattern of M. gadesensis . With respect to anatomical features, M. humicola has two testes on either side of the body, while its penis papilla is vertically oriented, in contrast to the 4-6 testes and horizontally oriented penis papilla of M. gadesensis . M. pyrenaica and M. howesi are bigger species (up to 5 cm long) with a poorly developed penis papilla ( Minelli, 1977), in contrast to the large and well defined papilla of M. gadesensis . In M. giustii , the testes are present in a postpharyngeal position ( Minelli, 1976), contrasting with the prepharyngeal testes of M. gadesensis . M. henrici , M. attemsi , and M. peneckei show atrial folds ( Minelli, 1977), whereas atrial folds are absent in M. gadesensis . In M. scharffi the vasa deferentia fuse to a common vas deferens at the base of the penis papilla ( Ball & Reynoldson, 1981). In M. gadesensis the vasa deferentia open into the bulbar lumen, far anterior to the root of the penis papilla. With respect to external features, M. scharffi is a very long (maximum 90 mm) animal with a pale colouration, whereas M. gadesensis is shorter and with darker colouration. In M. monacensis ( Heinzel, 1929) and M. terrestris ( Minelli, 1977) a bursa is present, whereas such a structure is absent in M. gadesensis .

Figures

FIGURE 6. Microplana gadesensis. CRBA 443 - 444. Sagittal section through the head.

FIGURE 7. Microplana gadesensis. CRBA 443 - 444. A – B. Sagittal sections of the copulatory apparatus; anterior to the left.

FIGURE 8. Microplana gadesensis. CRBA 443 - 444. A. Sagittal reconstruction of the copulatory apparatus; anterior to the left. CRBA 445. B. Sagittal reconstruction of the copulatory apparatus; anterior to the left.