Trocheta tunisiana, Ahmed, Raja Ben, Bielecki, Aleksander, Cichocka, Joanna M., Tekaya, Saïda, Gorzel, Małgorzata & Harrath, Abdul Halim, 2013

Ahmed, Raja Ben, Bielecki, Aleksander, Cichocka, Joanna M., Tekaya, Saïda, Gorzel, Małgorzata & Harrath, Abdul Halim, 2013, Erpobdellid leeches (Annelida, Clitellata, Hirudinida) from Tunisia: New records with the description of a new Trocheta species, Zootaxa 3681 (4), pp. 440-454 : 447-451

Trocheta tunisiana n. sp.

Holotype north-west Tunisia, spring Zaga in Béja (36°58’965” N, 9°5’693” E), December 2008, body length 50 mm, maximal width 5.2 mm, deposited in Muséum National d’Histoire Naturelle, Paris (catalogue number W245), preserved in ethanol 70%.

Paratypes the same locality, data, and depository as holotype, two mature specimens, body length 48 mm, maximal width 5 mm, preserved in ethanol 70%.

Other material examined Collected during the period extending from December 2007 to December 2009. Spring Oued El Madin (36°90’107” N, 9°16’501” E); stream Oued el Melih Ouechtéta (36°97’467” N, 09°01’214” E); spring Aïn Sobh Jendouba (36°57’173” N, 08°54’565” E); spring Touiaytia, Aïn Draham (36°74’456” N, 08°58’686” E).

Etymology. The specific epithet is derived from the name of the country from which the species was described.

Description of examined specimens. The largest preserved specimen measured 50 mm in length and 5.2 mm in width. The front of the body is broad and rounded compared to T. africana ; both anterior and posterior suckers are longitudinally elliptical and the posterior sucker is as wide as the widest part of the body. The head has four pairs of eyes. In the post-clitellar region, lateral keels are less prominent than in T. africana . The colour of living specimens is light brown. Dorsally, there are four longitudinal stripes ( Fig. 5a , b).The ventral surface is always somewhat lighter than the dorsum. Annulation is typical for the Trocheta species. The complete somite is divided into eight annuli, the first two of which are short, followed by three longer ones and another three short annuli ( Fig. 5 c). The gonopores are separated by two annuli, the prominent male pore is situated in XII b2/a2, whereas the inconspicuous female one is in furrow XII b5/c11. The pharynx lacks jaws whereas pseudognaths are present ( Fig 6 b).The digestive system is constructed typically for erpobdellid leeches. The testes are globular, numerous and form grape-like structures of testisacs. They begin at 1/3 of the distance between XVIII and XIX ganglion and reach close to the posterior sucker. The vas deferens ends at 1/3 of the distance between the ganglia XVIII and XIX. The sperm ducts form a loop ( Fig. 6a ). The atrium is located at the ganglia XII. The length of the male atrium is approximately 1/3 ns. It has relatively narrow cornua and a broad insertion in the atrial body, which is slender and narrow (significantly longer than wide) and slightly expanded. It is a little oblique in relation to the bursa and curves to the ventral side. The bursa is not big ( Fig. 4 m, n, o). The ovisacs are paired, elongated convoluted structures, showing anteriorly a 1.5 ns large ‘lateral’ loop and then lying mid-ventrally. They have 4 ns in length and they are arranged as loops, first they go posteriorly up to XVI ganglion and then turn back anteriorly up to the XII ganglion ( Fig. 6a ). Within the ovisacs of mature specimens, there are no visible oocytes observed which is probably due to the fact that the specimens were after reproduction.

The paper by Sket (1968 fig. 47–48) appeared to be very helpful in our interpretation of the reproductive system of T. tunisiana n. sp.

Remarks. The new taxon was assigned to the genus Trocheta based on the number and the subdivision of annuli per somite. In fact, our specimens possess a mid-body somite consisted of eight unequal annuli. Moreover, the ovisacs are long and may take 4ns, showing a large lateral loop in anterior part of ovisac course.

Trocheta tunisiana n. sp. can easily be distinguished from T. africana by its colour and size. The latter species is a relatively large leech that is mostly black in colour whereas T. tunisiana n. sp. is a medium-sized leech that is reddish brown in colour. Anatomically, the atrium in T. tunisiana n. sp. is smaller in size and different in shape than that of T. africana . The relative lengths of the ovisacs and sperm ducts are also different (Table 1). Moreover, the anterior sucker is more elongated in the new species than in T. africana ( Fig 6 b). The collection of specimens of T. africana and T. tunisiana n. sp. from the same region of Tunisia (northwest; Fig. 2 ) and during the same period (December) revealed that, although the specimens of both species were sexually mature, they were in different phases of the life cycle (respectively, before and after breeding).

Trocheta tunisiana n. sp. differs from T. subviridis Dutrochet 1817 , the type species of the genus, and from T. falkneri ( Nesemann and Neubert, 1996) by the distance between its gonopores (six to nine annuli in T. subviridis and four to five in T. falkneri ). It also differs from T. cylindrica Örley, 1886 (syn. T. bykowskii Gedroyċ, 1913 , see Košel 2004) by the varied colour of the body (grey and flesh coloured with lighter or darker brownish shade). Moreover, the integument of T. cylindrica is very transparent, making the internal structure well visible. Trocheta haskonis Grosser, 2000 is a giant leech compared with the T. tunisiana n. sp. having a body length up to 220 mm. In T. pseudodina Nesemann, 1990 the surface of the body is covered by papillae; similar to some species of the genus Dina in body coloration, there are also dark spots on dorsal side, which are arranged in transverse lines. On the basis of this comparison we conclude that T. tunisiana n. sp. represents a new species.

Ecology and distribution. Trocheta tunisiana n. sp. has been collected in smaller brooks and springs occurring in the mid and higher elevations (usually over 350 ASL). It is distributed in the northwest of Tunisia; we suggest that it should, probably, occur also in Algeria.

Figures

FIGURE 2. Distribution of erpobdellid leech species (Annelida, Clitellata, Hirudinida) in the North of Tunisia.

FIGURE 4. Ventral, dorsal and lateral views of male atria of mature specimens: a – c: E. testacea; d – f: D. punctata punctata; g – i: D. punctata maroccana; j – l: T. africana; m – o: T. tunisiana n. sp.

FIGURE 5. a: Dorsal view of T. tunisiana n. sp.; b: dorsal view of both T. tunisiana n. sp. (double arrow) and T. africana (arrow); c: annulation pattern in T. tunisiana n. sp. Scale bar: in a: scale bar = 6 mm; in b: scale bar = 8 mm; in c: scale bar = 10 mm.

FIGURE 6. a: Reproductive system of T. tunisiana n. sp.: atrium (at), ovisacs (o), preatrial loops (pr. l), sperm ducts (s), testisacs (t); b: anterior sucker of T. africana in the left (after Nesemann and Neubert, 1994) and T. tunisiana n. sp. in the right; arrows point to the pseudognathes; c: Schematic annulations type and gonopores of both Tunisian species of Trocheta.