Recurva conjuncta, 2013

Sluys, Ronald, Solà, Eduard, Gritzalis, Konstantinos, Vila-Farré, Miquel, Mateos, Eduardo & Riutort, Marta, 2013, Integrative delineation of species of Mediterranean freshwater planarians (Platyhelminthes: Tricladida: Dugesiidae), Zoological Journal of the Linnean Society 169 (3), pp. 523-547 : 542-543

RECURVA CONJUNCTA SLUYS SP. NOV.

( FIG. 17 )

Material examined: Holotype: ZMA V.Pl. 7123.1, near Agios Georgios , Kefalonia, Greece, 38°6′0.72″N, 20°44′55.50″E, 26 April 2009, coll. R. Sluys , sagittal sections of the anterior, prepharyngeal end of the animal on six slides; V.Pl. 7123.1, ibid., sagittal sections of the posterior end (including the pharynx) of the same animal on six slides.

Etymology: The specific epithet is derived from the Latin adjective coniunctu s, connected, and alludes to the genito-intestinal connection present in this species.

Diagnosis: Animals slender, with rotund head. Dorsal testes, distributed throughout the body length. Vasa deferentia narrow when penetrating the ventro-lateral side of the penis bulb, subsequently expanding again and opening into the mid-lateral section of the intrabulbar seminal vesicle. Asymmetrical penis papilla, with an oblique, ventro-posterior orientation. Ejaculatory duct opening at the anteroventral side of the penis papilla. Common oviduct surrounded by a coat of circular muscle. Copulatory bursa communicating with a branch of the intestine. Bursal canal surrounded by a layer of circular muscle.

Ecology and distribution: The species is known only from its type locality, where it was found under stones in an almost dry, muddy stream flowing beneath a concrete bridge.

Description: In the field the two specimens collected (one immature) were identified as Schmidtea -like animals, i.e. with a rounded head. The animals were very slender, the holotype specimen measuring up to 2 cm in length when fully stretched and moving. Dorsal surface pigmented, ventral surface pale (as deduced from examination of the sections). Each eye cup houses numerous retinal cells.

The pharynx measures about 1/9th of the body length, its root being situated about half-way along the body length. The mouth opening is located at the posterior end of the pharyngeal cavity.

The testes are situated dorsally, extending from directly behind the brain into the posterior end of the body. The vasa deferentia, which are expanded to spermiducal vesicles, narrow considerably when they penetrate the ventro-lateral side of the penis bulb. Once within the bulb, the ducts expand again in diameter and, subsequently, open into the mid-lateral section of the intrabulbar seminal vesicle. The latter is lined with a nucleated epithelium and surrounded by a rather thick coat of interwoven muscles.

The ejaculatory duct arises from the dorsal section of the seminal vesicle and immediately thereafter

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sharply curves postero-ventrally to continue its more or less central course through the penis papilla. However, at some point the ejaculatory duct makes another sharp, hooked bend towards the anteroventral surface of the body ( Fig. 17 ). This results in the situation that the duct opens at the anteroventral side of the penis papilla. The papilla has an oblique, ventro-posterior orientation and is covered with a nucleated epithelium. Because of the peculiar course of the ejaculatory duct, the distal section of the penis papilla is highly asymmetrical, with a short ventral lip and a bulky dorsal lip. In fact, the tip of the papilla is to some extent also curved towards the lateral side of the male atrium. Therefore, the opening of the ejaculatory duct is not only displaced towards the antero-ventral side of the penis papilla but also to a more lateral position. This lateral twist of the tip of the penis papilla may be due to a preservation artefact. The major portion of the ejaculatory duct is surrounded by a relatively thick layer of mostly circular muscle fibres.

The paired ovaries are situated directly behind the brain. Immediately posterior to the gonopore the oviducts turn medially and fuse to form a common oviduct, which opens at the postero-ventral section of the bursal canal. The common oviduct is surrounded by a coat of circular muscle.

The bursal canal arises as a broad duct from the mid-posterior wall of the atrium. This first, broad section of the canal runs more or less horizontally and receives the openings of the abundant shell glands, which open anteriorly to the opening of the common oviduct. This broad part of the bursal canal narrows considerably and, subsequently, curves forwards to continue its course immediately dorsally to the male atrium and the penis bulb. Half-way along its course the canal becomes even narrower before communicating with the copulatory bursa. The entire bursal canal is lined with a nucleated epithelium and is surrounded by a layer of circular muscle.

The copulatory bursa lies immediately anterior to the penis bulb, while its ventral part is connected with a branch of the intestine.

Figures

Figure 17. Recurva conjuncta Sluys sp. nov. ZMA V.Pl. 7123.1. Sagittal reconstruction of the copulatory apparatus.