Theama mediterranea Curini-Galletti, Campus & Delogu, 2008

Gammoudi, Mehrez, Tekaya, Saïda & Noreña, Carolina, 2009, Contribution to the knowledge of Acotylean Polyclads (Platyhelminthes, Polycladida) from Tunisian Coasts, Zootaxa 2195, pp. 43-60 : 53-55

Theama mediterranea Curini-Galletti, Campus & Delogu, 2008

( Figure 6 )

Diagnosis n. emend: Theama with few tentacular (2–4 per side) and cerebral eyes (2 per side). A pyriform penis bulb is provided with a long penis papilla and a sclerotized inner lining of the most distal portion of the ejaculatory duct. The penis bulb is surrounded by a tube-shaped penis sheath. A comparatively large uterus is present.

Distribution in Tunisia: Sandy beach at Bouficha (36°16 ' 48.36" N; 10°29 ' 36.98" E).

Other localities: Italy, Greece, Israel (see Curini-Galletti et al, 2008).

Material examined: 4 specimens were sagittally sectioned and mounted on 4 slides. The material examined was deposited in the Museo Nacional de Ciencias Naturales de Madrid ( Spain).

Description: Slender and elongate: living specimens measure up to 6 mm in length, and are 1,5 mm wide. Fixed specimens were about 2mm long and 0,4mm wide. Dorsal surface greyish. Without nuchal tentacles. Tentacular eyes in front and at each side of the brain, arranged in two groups. Cerebral eyes form two rows of 2 eyes ( Fig. 6 A). Eyes up to 10 μm in diameter. The mouth lies just in front of the middle of the pharyngeal cavity, which contains the ruffled, non-ciliated pharynx. The gut runs medially backwards to behind the male antrum and forwards to the cerebral area. Its lumen becomes remarkably wider dorsally to the pharynx and the male copulatory apparatus ( Fig. 6 E). Body entirely ciliated, with epidermal cells overlying a relatively thick basement membrane. Rhabdites are present on both ventral and dorsal surfaces of the body. Body musculature consists of external circular and internal longitudinal fibres, more developed ventrally than dorsally.

The sectioned specimens were immature in the female line, and only male structures could be observed.

Male copulatory apparatus: Testes are scattered throughout the dorsal parenchyma of the submarginal zones of the body, forming two rows on both sides. The paired vasa deferentia run posteriorly; each duct is slightly enlarged, forming false seminal vesicles ( Fig. 6 C), which fuse distally and join a true seminal vesicle, provided with a thick muscular wall. The ovoid seminal vesicle is relatively large and oriented obliquely ( Fig. 6 B). Its anterior end narrows to open into an interpolated spherical prostatic vesicle with radial folds, ( Fig. 6 B). The wall of the prostatic vesicle is very muscular and forms a penis bulb which is housed in a tube shaped penis–sheath, oriented horizontally ( Fig. 6 B). From the prostatic vesicle, the ejaculatory duct extends anteriorly to open into the conical penis papilla. The lining of the most distal portion of the ejaculatory duct is provided with a sclerotized sheath ( Fig. 6 D).

The tube shaped penis-sheath opens into an antrum masculinum which leads to the male pore, located ventrally

Remarks. The genus Theama and the family Theamatidae were created by Marcus (1949). The first species described was T. evelinae Marcus, 1949 . Sopott-Ehlers & Schmidt (1975) described T. occidua which differs mainly due to the absence of a stylet. Faubel (1983) considered the lack of a stylet in T. occidua of generic value and placed the species in a new genus Eutheama Faubel, 1983 . Bulnes & Faubel (2003) described a second species of the genus Eutheama from Australian waters: E. forrestensis . More recently, Curini-Galletti et al. (2008) described a new representative of Theamatidae ; T. mediterranea , and compared the different members of the genus Theama . Examining type material of T. occidua Sopott-Ehlers & Schmidt , c e: cerebral eyes, f s v: false seminal vesicle, i: intestine, mp: male pore, p b: penis bulb, p g: prostatic glands, pp: penis papilla, p v: prostatic vesicle, r f: radial folds, s v: seminal vesicle, t e: tentacular eyes, s s: sclerotized sheath.

1975 and T. evelinae Marcus, 1949 , the authors concluded that the stylet described by Marcus (1949) corresponds in reality to a sclerotized inner lining of the ejaculatory duct. The two genera Eutheama Faubel, 1983 and Theama Marcus, 1949 were thus synonymized in the oldest genus of both: Theama Marcus, 1949 .

Based on our Tunisian material, we confirm the presence of a sclerotized cylindrical sheath lining the most distal portion of the ejaculatory duct ( Fig. 6 D). Moreover, as sampling was done in the beginning of March 2008, and all specimens collected were immature in the female line, we confirm the presumption of Curini-Galletti et al (2008) regarding the annual life cycle of T. mediterranea .

Figures

FIGURE 6. Theama mediterranea: A: anterior view, B, C: male copulatory apparatus D: detail of the distal portion of the ejaculatory duct, E: sagittal reconstruction of male copulatory apparatus.