Notoplanella estelae, Marquina, Daniel, Osca, David, Rodríguez, Jorge, Fernández-Despiau, Estrella & Noreña, Carolina, 2014

Marquina, Daniel, Osca, David, Rodríguez, Jorge, Fernández-Despiau, Estrella & Noreña, Carolina, 2014, State of knowledge of the Acotylea (Polycladida, Platyhelminthes) from the Mediterranean coasts of Spain: new records and new species, Zootaxa 3780 (1), pp. 108-134 : 111-116

Notoplanella estelae sp. nov.

Figs. 1 (2), 4, 5

Type locality. Lo Pagán, Mar Menor, 37°48’ N, 00°47’ W. Collected by SCUBA diving; from rocky substrate found between 0.2–1 metres deep; Fig. 1 (2).

Type material. Holotype: one mature specimen sagittally sectioned; MNCN 4.01/200 to MNCN 4.01/215 (15 slides). Paratype: one mature specimen sagittally sectioned; MNCN 4.01/216- MNCN 4.01/231 (16 slides). Leg. Angel Pérez-Ruzafa.

Material examined. Two mature ( MNCN 4.01/200 to MNCN 4.01/215 (15 slides) and MNCN 4.01/216- MNCN 4.01/231 (16 slides)) and two juvenile specimens sagittally sectioned. The material is deposited in the invertebrate collection of Museo Nacional de Ciencias Naturales de Madrid ( Spain). Collected by Angel Pérez- Ruzafa.

Etymology. The specific epithet is dedicated to Estela Barroso, girlfriend of the first author.

Diagnosis. Notoplanella with numerous dark spots on the dorsal surface, except on the median line. With nuchal tentacles. Tentacular and cerebral eyes present. A short duct links the seminal and the prostatic vesicles and shows a dilatation before the prostatic vesicle. Large penis papilla. Female system with a small Lang’s vesicle. Gonopores separated.

Description. Fixed specimen is 7 mm long by 2 mm wide. Body elongated, anteriorly truncated, lateral margins almost parallel, posteriorly slightly rounded. Ground colour pail, with numerous smaller and larger dark spots on the dorsal surface, except along above the pharynx and the genital region. Sometimes the smaller spots arranged in small interconnected groups. Marginal band free of spots ( Fig. 4 A). Small nuchal tentacles present. Tentacular eyes primarily at the bases and some inside the tentacles ( Figs. 4 B, 5A). The cerebral and pre-cerebral eyes form a single and elongated undifferentiated group; marginal or frontal eyes lacking. Tentacular eyes larger than cerebral ones. Bilobated brain with two symmetrical lobes ( Fig. 4 B). The pharynx occupies the middle third of the body, mouth opening at the medial region ( Fig. 4 C).

Testes and ovaries extend on both sides of the body; testes ventral and ovaries dorsal. Gonopores separated. Male copulatory apparatus, directed backwards, begins almost immediately behind the pharyngeal cavity. Deferent ducts become wider before entering ventrally, describing an arc, into the seminal vesicle ( Fig. 4 D). Seminal vesicle with thick muscular walls. Elliptic prostatic vesicle (65 µm in length and 40µm in width) interpolated, with a strong muscular envelope and inner epithelium folded, with eosinophilic secretion. Seminal and prostatic vesicle connected by a short narrow duct that widens at the end. Ejaculatory duct straight, with undifferentiated inner epithelium. Large and unarmed penis papilla, conical-shaped, housed in a non-ciliated atrium ( Fig. 5 B).

Female system with vestigial Lang’s vesicle. Oviducts lead together into an unpaired organ, anterior to the poorly developed Lang’s vesicle. The narrow proximal tract of the vagina runs forwards, turns backwards, then becomes wider and receives secretions from well developed cement glands. The external vagina is short and narrow, and runs straight down to the gonopore ( Figs. 4 D, 5C).

Discussion. The genus Notoplanella has the only species Notoplanella inarmata from South Africa Bock, 1931. With the discovering and description of N. estelae , the genus has currently increased to two species. The specimen captured in Mar Menor clearly belongs to the genus Notoplanella . It exhibits characteristics of the genus, such as an oval-shaped body, paired cerebral and tentacular eye clusters, a central pharynx, a true seminal vesicle connected by a narrow duct to a large elliptic and interpolated prostatic vesicle with strong muscle layers, an unarmed penis papilla, a weak muscular vagina and a common oviduct ( Bock 1931).

Notoplanella estelae sp. nov., in contrast to N. inarmata , possesses nuchal tentacles, located slightly behind the brain. The brain is bilobated in both species; however, in N. inarmata , the anterior end of the lobes is pointed and larger than the posterior end ( Bock 1931), while in N. estelae , the lobes are rounded in both extremes and the posterior end is larger than the anterior. Both species of the genus also have centrally-located pharynges, although in N. inarmata , the oral pore opens at the posterior end of the pharynx, while in N. estelae , it opens at the centre.

The main differences in the reproductive system largely correspond to the male complex. The characteristic duct between the seminal and prostatic vesicles is much shorter in N. estelae and enlarges before entering the prostatic vesicle. In addition, the prostatic vesicle is smaller and the penis papilla is much larger in N. estelae than in N. inarmata . The only difference in the female system between these two species is the presence of a vestigial Lang’s vesicle in N. estelae .

In the description of N. inarmata, Bock (1931) asserts that the opening of the oviducts suggests its ancestor had a Lang's vesicle and, furthermore, that the structure of the proximal portion of the vagina can only be explained owing do this character. Thus, the presence of a vestigial Lang’s vesicle in N. estelae is compatible with belonging to the genus Notoplanella .

The presence of nuchal tentacles and a vestigial Lang’s vesicle in N. estelae requires the addition of those characters to the genus’ diagnosis. Therefore, the genus diagnosis is now as follows:

Diagnosis ( Bock 1931) emended: Cryptocelidae with oblong-oval body shape, with or without tentacles. Paired cerebral and tentacular eye clusters present. Pharynx central. True seminal vesicle connected to the prostatic vesicle by a narrow duct. Interpolated large prostatic vesicle, elliptic, with numerous secretory ducts. Unarmed penis papilla. Weak muscular vagina, with or without a vestigial Lang’s vesicle, with the common oviduct clearly differentiated.

Figures

FIGURE 1. Distribution map of examined specimens. General views of A the eastern coast of the Iberian Peninsula, B Mar Menor (Murcia). Numbers: Notoplanella inarmata (1), Notoplanella estelae sp. nov. (2), Trigonoporus cephalophtalmus (3), Leptoplana mediterranea (4), Planocera graffi (5), Imogine mediterranea (6), Imogine stellae sp. nov. (7), Stylochus neapolitanus (8), Stylochus pilidium (9).

FIGURE 4. Notoplanella estelae sp. nov. A Habitus; B dorsal view of the anterior region; C sagittal reconstruction of the whole animal (anterior to the left); D sagittal reconstruction of male and female genital systems (anterior to the left). Abbreviations: b, brain; ce, cerebral eyes; cg, cement glands; com. ov, common oviduct; ed, ejaculatory duct; ev, external vagina; fp, female pore; i, intestine; Lv, Lang’s vesicle; m, mouth; mp, male pore; o, ovary; ov, oviduct; ph, pharynx; pp, penis papilla; pv, prostatic vesicle; sv, seminal vesicle; t, tentacle; te, tentacular eyes; ts, testes; vd, vas deferens. Scale bars: A 2 mm, B 500 µm, C 1 mm, D 200 µm.

FIGURE 5. Histological sections of Notoplanella estelae sp. nov. A Tentacle region and eyes (anterior to the left); B male copulatory complex (anterior to the right); C female reproductive system (anterior to the right). Abbreviations: cg, cement glands; com. ov, common oviduct; ev, external vagina; fp, female pore; mp, male pore; pp, penis papilla; pv, prostatic vesicle; t, tentacle; te, tentacular eyes; sv, seminal vesicle. Scale bars: A 100 µm, B, C 200 µm.