Dugesia hepta Pala, Casu and Vacca, 1981

Stocchino, G. A., Corso, G., Manconi, R., Casu, S. & Pala, M., 2005, Endemic freshwater planarians of Sardinia: Redescription of Dugesia hepta (Platyhelminthes, Tricladida) with a comparison of the Mediterranean species of the genus, Journal of Natural History 39 (22), pp. 1947-1960 : 1949-1957

publication ID	https://doi.org/ 10.1080/00222930500060025
persistent identifier	https://treatment.plazi.org/id/9B71BD4D-FFAE-FFDA-33AE-FDE865022793
treatment provided by	Felipe
scientific name	Dugesia hepta Pala, Casu and Vacca, 1981
status

Treatment

( Figures 1–7 View Figure 1 View Figure 2 View Figure 3 View Figure 4 View Figure 5 View Figure 6 View Figure 7 )

Type material and all specimens, both living and preserved, are at present deposited in the collection of Prof. Maria Pala at the Dipartimento di Zoologia e Antropologia Biologica of the University of Sassari (DIZAB).

Type material

Neotype: DIZAB Pla 3.1, one set of sagittal sections on 88 slides, Rio Sorgenti San Martino (40 ° 419N, 8 ° 409E), 18 May 2000, G. A. Stocchino, leg.

Other material examined

DIZAB Pla 3.2, one set of sagittal sections on 68 slides ; DIZAB Pla 3.3–5, three sets of transverse sections on 108 slides, 135 slides, 44 slides ; DIZAB Pla 3.6, one set of frontal sections on 24 slides (same location as for neotype), 18 May 2000 , G. A. Stocchino, leg.

DIZAB Pla 3.7, one set of sagittal sections on 99 slides ; DIZAB Pla 3.8, one set of transverse sections on 119 slides ; DIZAB Pla 3.9, one set of frontal sections on 47 slides, Rio dei Molini (40 ° 419N, 8 ° 389E), 20 June 2001 , G. A. Stocchino, leg.

Comparative material

Slides of Dugesia biblica , D. etrusca , D. leporii , and D. sicula were examined. For the other species, the comparative analysis refers to data from the original descriptions (see Table I; Benazzi 1946; Lepori 1947, 1948a, 1948b, 1951; Benazzi and Banchetti 1972; Pala et al. 1981, 2000; De Vries and Benazzi 1983; De Vries 1984, 1986, 1988).

Diagnosis

Dugesia hepta is characterized by the peculiar dorsal course of the ejaculatory duct and its opening located laterally on the right with respect to the penis papilla apex; asymmetrical penis papilla with a ventro - lateral penial fold; openings of shell glands localized below the vaginal area of the bursal canal. The species is distinguishable from other dugesiid species by peculiar macroscopic body traits such as an abruptly pointed tail, the less obvious evident retro-cephalic narrowing (‘‘neck’’) and the presence, on the surface, of two dorsally situated longitudinal dark brown stripes extending over the whole body length.

Distribution

Dugesia hepta is known from 22 sites in the north-western part of Sardinia. The range of the species is restricted to four hydrographic basins ( Figure 1A–D View Figure 1 ): (A) Rio Mannu di Portotorres basin: 1, Rio Sorgenti San Martino; 2, Rio Montes; 3, Rio s’Iscia; 4, Rio dei Molini; 5, Rio Murroni; 6, Rio Bunnari; 7, Rio Mascari; 8, Rio Badu ‘e se; 9, Rio Logulentu; (B) River Silis basin: 10, River Silis; 11, Rio San Lorenzo; 12, Rio Furrinchesu; (C) River Coghinas basin: 13, Rio Mannu di Pattada; 14, Rio di Oschiri; 15, Rio Buttule; 16, Rio Mannu di Ozieri; 17, Rio Ilde; 18, Rio Santa Lucia; 19, Rio Badde Dianesu; (D) River Temo basin: 20, River Temo; 21, Rio Mulinu; 22, Rio Maggiolsi.

Habitat

Dugesia hepta lives in shallow, clear, running waters on substrates ranging from pebbles, cobbles and boulders to timber and aquatic vegetation. The water level shows notable fluctuations around the year with a temperature of 15–20 ° C and pH 7–8. Almost all populations were found in small tributaries, except for site 10 in the main course of the River Silis ( Figure 1 View Figure 1 ). Large numbers of cocoons were found exclusively during spring. D. hepta was found in macrozoobenthic communities composed mainly by other planarians and amphipods, but also by gastropods, benthic insects, and leeches. When associated with other planarians, D. hepta was coexistent with D. sicula in the River Silis, D. benazzii (diploidic and polyploidic biotype) in the Rio Mannu di Portotorres, River Coghinas, River Temo and River Silis, and Schmidtea polychroa View in CoL (biotype A) in the River Silis and Rio Mannu di Portotorres ( Vacca et al. 1988, 1993).

Description

All specimens studied showed the peculiar chromosomal number, n 57; 2 n 514.

External features. Measured specimens are about 14–17 mm long and 3–4 mm wide. Two eyes are present in the middle of the head. Auricular grooves lack pigment. Five sensory fossae are present on each side of the anterior margin of the head.

Characters D. hepta D. elegans D. etrusca

. S subtentaculata gonocephala ilvana leporii liguriensis malickyi minotauros sagitta sicula

. . . . . . . . .

D D D D D D D D D S. + + 2 2 + 2 + + + + + 2 + + + + + + + 2 2 2 + + 2 + 2 2 2 2 2 + 2 2 2 2 2 2 2 + 2 + + +? + + + + + 2 +? + + + + + 2 + + + + + + 2 + + + + + + + + + + + + 2 + 2 2 2 2 2 + 2 2 2 2 2 2 2 2 2 2 2 2 + 2 + 2 + 2 + 2 + + 2 + + + + + + 2 + 2 2 2 2 + 2 + 2 + 2 2 + 2 2 2 2 2 2 + 2 + + + 2 2 2 2 2 + 2 2 2 + + 2 2 2 2 2 + 2 + 2 + + + + + 2 + + + 2 2 + + + + + 2 + 2 + + 2 2 2 + 2 2 + 2 2 2 + 2 + + 2 + 2 2 2 2 + + + 2 2 + 2 + + + 2 + 2 2 + 2 + 2 + 2 2 2 2 2 + 2 2 2 2 2 2 2 2 2 2 2 2 + 2 + 2 2 + 2 2 + + + 2 + + + 2 + + + + 2 2 2 2 + 2 2 2 2 2 2 + 2 2 2 2 2 2 2 2 + + 2 2 2 2 + 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 + 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 + 2 2 2 2 2 2 2 2 2 2 2 + 2 2 2 2 2 2 2 + + + + 2 + + + + + + + 2 + 2 + + 2 + + 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 + 2 2 2 2 2 2 2 + 2 + 2 2 + 2

Width is almost constant along the entire body from the retro-cephalic area to the tail, which makes the retro-cephalic narrowing (‘‘neck’’) less obvious than in other Dugesia species. The caudal area is abruptly pointed. Two longitudinal dark brown large stripes extending throughout the body length are clearly visible on the dorsal surface, one at each side of the pharynx with proximal portion behind the ovaries ( Figure 2 View Figure 2 ).

Colour is light brown dorsally with the exception of a colourless peripheral band (0.5 mm in width), the ventral surface is paler and bears oral and genital pore openings.

Internal features. Inner and outer pharyngeal musculature is bilayered. The ventrally located, paired ovaries in the retro-cephalic region are in contact with the enlarged part of the oviduct (seminal receptacle) in their dorso-lateral area. Oviducts curve toward the ventral area running caudally up to the vaginal area of the bursal canal where they open separately and symmetrically.

The copulatory apparatus with the bursa copulatrix and its canal, the penis, the atrium, the vasa deferentia, and the oviducts, were drawn at the same scale and represented as sagittal and frontal reconstruction ( Figures 3 View Figure 3 , 4 View Figure 4 ). The bursa copulatrix, sac-like in shape, laterally compressed and elongated in the antero-posterior direction, occupies more or less the dorsal half of the body. It is surrounded by a thin longitudinal muscle layer and lined with high secretory cells with basal nuclei ( Figure 5A View Figure 5 ). The bursal canal runs to the left of the copulatory apparatus and opens dorsally in the atrium. Its wall consists of an infranucleate secretory epithelium with cylindrical, ciliated cells. The lumen epithelium is surrounded by a thin inner layer of longitudinal muscles and a thick outer circular one ( Figure 5B View Figure 5 ).

Ripe testes, numerous and well developed, begin at the level of the ovaries. Vitellaria are located in between the testes. The penis, ¡630 Mm long, is formed by the penis bulb and the penis papilla. The large and highly muscular penis bulb, rich in secreting glands, contains a large eccentric seminal vesicle ( Figure 6A, C View Figure 6 ). This vesicle is separated from the ejaculatory duct by a pointed diaphragm and receives the symmetrical openings of the vasa deferentia in its terminal tract ( Figures 5C View Figure 5 , 6A View Figure 6 ). At the level of the bursa copulatrix, the vasa deferentia form numerous false seminal vesicles ( Figures 3 View Figure 3 , 4 View Figure 4 , 5A View Figure 5 ).

The penis papilla is cone-shaped, has the same length as the bulb and protrudes in the atrium ( Figure 5C View Figure 5 ). The papilla is lined by an infranucleate epithelium below which extends the circular muscular layer.

A penial fold is localized ventro-laterally in the area of transition between the penis bulb and penis papilla. Histologically it consists of parenchymatic glandular tissue surrounded by a well-developed muscular sheet, which in some places penetrates in the parenchyma ( Figures 5C View Figure 5 , 6A, B View Figure 6 ).

The ejaculatory duct is situated dorsally and opens laterally on the right side with respect to the penis papilla apex ( Figures 5C View Figure 5 , 7A, B View Figure 7 ). This condition makes the penis papilla asymmetrical, with the ventral part greater than the dorsal one. Several glands open along the entire course of the ejaculatory duct ( Figure 7C View Figure 7 ). In all studied specimens collected during spring the ejaculatory duct is filled with spermatophores, sometimes protruding in the atrium ( Figures 5D View Figure 5 , 7B, D View Figure 7 ).

The atrium is undivided and opens ventrally by a gonopore ( Figure 5C View Figure 5 ). The atrial cavity, lined by a simple folded epithelium of variable height ( Figures 5C View Figure 5 , 7B, D, E View Figure 7 ), receives the secretion of shell and cement glands. The former are few and open just ventrally of the vaginal area of the bursal canal ( Figure 7D View Figure 7 ), whereas the latter are more abundant and open near the gonopore ( Figures 3 View Figure 3 , 7F View Figure 7 ).