Dendrocoelum spatiosum 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 : 5-10

Genus Dendrocoelum Örsted, 1844

Dendrocoelum spatiosum Vila-Farré & Sluys , sp. nov. ( Table 1 , Figs. 3 , 4 A–B, 5A–B, 6A–B)

Material examined. HOLOTYPE. ZMA V.Pl. 6864.5, River Palancia, Sot D'En Ferrer, Castellón, Spain, 19 April 2005, sagittal sections on six slides.

PARATYPES. ZMA V.Pl. 6864.1, ibid., sagittal sections on seven slides; V.Pl. 6864.2 ibid., horizontal sections on four slides; V.Pl. 6864.3, ibid., sagittal sections on five slides; V.Pl. 6864.4, ibid., sagittal sections on six slides.

Other material. ZMA V.Pl. 6865.1, River Palancia, Sot D'En Ferrer, Castellón, Spain, 24 April 2004, sagittal sections on six slides; V.Pl. 6866.1, River Palancia, Sot D'En Ferrer, Castellón, Spain, horizontal sections on four slides; V.Pl. 6866.2, ibid., horizontal sections on three slides; V.Pl. 6866.3, ibid., transverse sections on three slides; V.Pl. 6866.4, ibid., transverse sections on five slides; V.Pl. 6866.5, ibid., transverse sections on three slides; V.Pl. 6866.6, ibid., sagittal sections on four slides.

Etymology. The epithet is derived from the Latin adjective spatiosus, spacious, and alludes to the considerably widened bursal canal of the species.

Ecology. The species has been collected on several occasions (but not on all sampling visits) from a shady area at a branch of the river Palancia. This area is covered by a dense layer of vegetation from the gallery forest. The species is apparently absent from the main course of the river. This suggests that it is an inhabitant of the phreatic waters that eventually occurs in surface waters.

Diagnosis. Dendrocoelum spatiosum sp. nov. can be distinguished anatomically from its congeners by the presence of a V-shaped ventral extension of the bursal canal immediately anterior to the penis bulb, a widening of the bursal canal in a horizontal direction, a large adenodactyl with a voluminous bulb and a large free papilla that is located to the right of the penis papilla.

Description. Living, sexually mature specimens were 8–12 mm long and 1 mm wide in an elongated state. Preserved specimens measured up to a maximum of 6.9 mm. The unpigmented, flattened body presents a truncated anterior end with rounded lateral margins ( Fig. 4 A). The adhesive organ is reduced to a very small protuberance in the middle of the anterior margin. The lateral body margins run almost parallel and diverge only slightly behind the anterior end, while at the posterior level of the copulatory apparatus they converge to form a pointed tail. The two small eyes (eye cup diameter 35 µm in sections) are far removed from the frontal margin and lie close together at a distance of 1/5th to 1/6th of the width of the head.

The cylindrical, horizontally oriented pharynx is inserted at about the middle of the body and measures about 1/6th (in sections) to 1/7th (in preserved whole mount) of the body length. The outer epithelium of the pharynx is underlain by a layer of longitudinal muscles, followed by a thick layer of circular muscles. The inner epithelium is underlain by an intermingled layer of circular and longitudinal fibres, the latter being more scarce. The mouth is situated in the posterior portion of the pharyngeal pocket, close to the hind wall of the pharyngeal pouch. In specimen V.Pl. 6864.1 (approximate body length 5 mm, measured from sections) the mouth is situated 2.9 mm from the tip of the body and 0.62 mm from the gonopore. The anterior ramus of the intestine ends a certain distance behind the eyes. The posterior gut trunks meet in the posterior end of the body.

Numerous ventral testes are irregularly distributed on either side of the body. The oval-shaped follicles occupy approximately one-third of the dorsoventral diameter of the body and extend from a short distance behind the ovaries into the posterior end of the body. At the posterior end of the pharyngeal pouch the vasa deferentia widen to form large, irregularly sac-shaped spermiducal vesicles, lined with a tall, vacuolated epithelium. These spermiducal vesicles occupy approximately two-thirds of the dorsoventral diameter of the body. The two vasa deferentia separately penetrate the lateral surface of the penis bulb and open separately into the irregularly-shaped intrabulbar cavity. The ejaculatory duct runs centrally through the penis papilla. The wide lumen of the ejaculatory duct is lined with very tall epithelium and is surrounded by a thin layer of circular muscles, followed by abundant longitudinal muscle fibres.

The penis bulb is formed by intermingled circular and longitudinal muscle fibres that are especially abundant around the seminal vesicle ( Fig. 4 B). The penis papilla is covered with tall, nucleated epithelium, which is underlain with a subepithelial layer of circular muscles ( Fig. 5 A). The male atrium is covered with circular muscle fibres, followed by longitudinal fibres. In V.Pl. 6866.1, the gonopore lies at the level of the base of the adenodactyl ( Fig. 5 B).

The ovaries occupy about half of the dorsoventral diameter of the body. They are located at about 1/6th of the distance between the brain and the root of the pharynx. The oviducts arise from the anterolateral side of the ovaries. Posterior to the penis papilla the ducts fuse to form a long common oviduct, which opens into the common atrium ( Fig. 6 A). The distal section of the oviducts and part of the common oviduct receive the openings of abundant shell glands. The vitellaria extend from anterior to the ovaries into the posterior end of the body.

From its point of communication with the common atrium, the bursal canal curves over the male atrium and widens considerably in a horizontal direction, to reach its maximum width at the level of the base of the penis papilla ( Fig. 6 B). At this point, the canal is lined with a flat, nucleated epithelium that is underlain by a thin layer of circular muscle fibres, bound by a thin layer of longitudinal fibres, many of which are oriented perpendicularly to the canal’s epithelium ( Fig. 6 B). In addition, the canal also widens considerably in a dorsoventral direction. A large, V-shaped ventral extension of the canal is present immediately anterior to the penis bulb in all specimens ( Fig. 4 B). Then, the bursal canal narrows considerably before it opens into a large copulatory bursa.

A large adenodactyl is located to the right of the penis papilla and the common atrium. This adenodactyl consists of a voluminous bulb, which is located within the mesenchyma, and a free papilla. The papilla measures about two-thirds of the total length of the adenodactyl. The bulb is formed by abundant intermingled circular and longitudinal muscle fibres. The duct that runs through the adenodactyl receives the openings of glands. This duct is very wide within the bulb but narrows considerably before opening at the tip of the papilla. In specimens V.Pl. 6864.5 and V.Pl. 6866.1 the papilla points into the posterior part of the bursal canal ( Figs. 5 B, 6B).

Springs of the River Pamisos in Aghios Pelopon- Greece 22.02479302 37.16894333 Ph. graeca Floros nese

indicate that data for Argos is approximate

Discussion. Many members of the genus Dendrocoelum are anophthalmous, cave-dwelling species with a very small distribution range. However, some members, such as D. lacteum , have a wide range. No less than eight subgenera have been described for this genus: Dendrocoelides De Beauchamp, 1919 , Apodendrocoelum De Beauchamp, 1931 , Bolbodendrocoelum De Beauchamp, 1932 , Polycladodes Steinmann, 1910 , Neodendrocoelum Stankoviċ & Komárek, 1927 , Palaeodendrocoelum Codreanu, 1949 , Eudendrocoelum Komárek, 1925 , and Dendrocoelum (cf. Gourbault, 1972). Polycladodes presents a characteristic arrangement of the pharyngeal musculature, which is different from that found in D. spatiosum . In recent literature, Polycladodes was treated as a full genus (cf. Sluys & Kawakatsu, 2006). The penis papilla in Apodendrocoelum is small and the common atrium is surrounded by a thick zone of intermingled circular and longitudinal muscles. Bolbodendrocoelum is characterized by a very large penis bulb. The adenodactyl in Neodendrocoelum is very large, as is the penis papilla, in general. However, Neodendrocoelum is poorly differentiated from Dendrocoelides ( Kenk, 1978) . The subgenus Eudendrocoelum is poorly differentiated from the subgenus Dendrocoelum , which is characterized by the presence of a flagellum in the penis papilla ( Gourbault, 1972). In view of the uncertain taxonomic status of several of these subgenera, we do not assign D. spatiosum to any of these taxa.

The most characteristic trait of D. spatiosum is the anatomy of the bursal canal. Therefore, in the discussion below we do not include species with bursal canals that are anatomically very different from that of D. spatiosum . The species D. spatiosum stands apart from other members of the genus Dendrocoelum s. l., due to the anatomy of its genital apparatus. The penis papilla in D. boettgeri An Der Lan, 1955 and D. puteale Kenk, 1930 is absent or reduced, whereas it is well developed in D. spatiosum . D. sphaerophallus ( De Beauchamp, 1929) has a spherical penis papilla and the testes are mainly dorsal, whereas in D. spatiosum the testes are mainly ventral and the penis papilla is different.

D. infernale (Steinmann, 1907) , D. romanodanubiale (Codreanu, 1949) , D. subterraneum Komárek, 1918 and D. tubuliferum De Beauchamp, 1919 all have a flagellum in the penis papilla, whereas such a structure is absent in D. spatiosum .

D. agile De Beauchamp, 1932 is characterized by an extremely large penis bulb, which is smaller in D. spatiosum .

In D. barbei De Beauchamp, 1956 , D. beauchampi Del Papa, 1952 , D. bohemicum Komárek & Kunst, 1956 , D. cavaticum (Fries, 1874) , D. debeauchampianum Codreanu & Balcesco, 1967 , D. hankoi (Gelei, 1927) , D. kenki De Beauchamp, 1937 , D. longipenis Komárek, 1916 , D. racovitzai De Beauchamp, 1949 , and D. regnardi ( De Beauchamp, 1919) the penis is larger than or similar in size to the adenodactyl. In contrast, the penis is smaller than the adenodactyl in D. spatiosum .

D. findeneggi (Reisinger, 1971) has a ventral adhesive zone that is absent from D. spatiosum . In the following species, the testes are dorsal or dorsal and ventral, in contrast to D. spatiosum : D. atriostrictum Codreanu & Balcesco, 1967 ; D. banaticum Codreanu & Balcesco, 1967 ; D. clujanum Codreanu, 1943 ; D. coiffaiti De Beauchamp, 1956 ; D. italicum Vialli, 1937 ; D. stenophallus Codreanu & Balcesco, 1967 ; and D. tismanae Codreanu & Balcesco, 1967 .

The descriptions of D. alexandrinae Codreanu & Balcesco, 1970 and D. geticum Codreanu & Balcesco 1970 are incomplete. However, the shape of the bursal canal in D. alexandrinae and D. geticum is apparently very different from that in D. spatiosum . D. alexandrinae possesses an adhesive organ, which is absent from D. spatiosum . In addition, all the species discussed, except D. romanodanubiale and D. longipenis , are blind, whereas D. spatiosum has two eyes.

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 4. Dendrocoelum spatiosum (A – B) specimens from Sot d’En Farré, (A) living animal, (B) holotype V. Pl. 6864.5, sagittal section of the copulatory apparatus (anterior to the right).

FIGURE 5. Dendrocoelum spatiosum (A – B), holotype V. Pl. 6864.5, sagittal reconstructions of the copulatory apparatus (anterior to the right).

FIGURE 6. Dendrocoelum spatiosum (A – B), V. Pl. 6866.1, horizontal reconstructions of the copulatory apparatus (anterior to the right).

Tables

TABLE 1. List of localities with new species of freshwater planarians in the Iberian Peninsula and Greece. Latitude and longitude are expressed in decimal degrees (Datum European, 1979). Latitude and longitude for “ Canal of Argos, near Argos and Néa Kíos ” are approximations.

Locality	Province	Country	Longitude	Latitude	Species
Palancia river, Sot d'En Ferrer	Castelló	Spain	-0.41168603	39.81017865	Dendrocoelum spatiosum
River Bidasoa, Narbarte	Navarra	Spain	-1.62582062	43.13468314	D. inexspectatum
Fuente de Don Pedro, Loja	Granada	Spain	-4.13251329	37.17608394	Ph. flamenca
Spring in Carneros	León	Spain	-6.04720451	42.47569839	Ph. asymmetrica
River Miño in Ourense city	Ourense	Spain	-7.85127713	42.35488054	Ph. gallaeciae
River Miño after Belesar dam	Lugo	Spain	-7.7086738	42.6293069	Ph. gallaeciae
Spring near Basturs ("Font Barona?")	Lleida	Spain	0.99903461	42.13747772	Ph. pyrenaica , dark form
Font de la Figuereta, Pobla de Segur	Lleida	Spain	1.02867744	42.27187649	Ph. pyrenaica , dark form
Font de la O (spring), Aramunt	Lleida	Spain	0.98297243	42.20031304	Ph. pyrenaica , transparent form
Canal of Argos, near Argos and Néa Kíos	Pelopon- nese	Greece	22.74521827	37.62510898	Ph. hellenica