Dugesia bursagrossa Harrath & Sluys 2025, sp. nov.
Creators: name: Harrath, Abdel Halim
name: Mansour, Lamjed
name: Sluys, Ronald
name: Aldahmich, Waleed
name: Riutort, Marta
name: Alwasel, Saleh
Publisher: name: Zenodo
Year: 2025
Subjects: Biodiversity
Taxonomy
Animalia
Platyhelminthes
Tricladida
Dugesiidae
Dugesia
Dugesia bursagrossa

description: Dugesia bursagrossa Harrath & Sluys, sp. nov.
Material examined. Holotype: RMNH.VER.21535.1, Ain Dhiba, Abha province, Saudi Arabia (18°16’44.4”N 42°23’18.6”E), 16 th August 2020, coll. Waleed Aldahmash and Abdel Halim Harrath, sagittal sections on 42 slides. Paratypes: RMNH.VER.21535.2, ibid., sagittal sections on 44 slides; RMNH.VER.21535.3, ibid., horizontal sections on 42 slides, RMNH.VER.21535.4, ibid., sagittal sections on 61 slides; RMNH.VER.21535.5, ibid., horizontal sections on 27 slides.
Etymology. The specific epithet is based on the Latin noun bursa, alluding to the copulatory bursa in planarians, and the Latin adjective grossus, big, thick; thus, the name refers to the very large copulatory bursa in the new species.
Diagnosis. Dugesia bursagrossa is characterized by the following anatomical features:dorsal testes; symmetrical and highly glandular, barrel-shaped penis papilla; vasa deferentia opening separately into the antero-dorsal portion of a small intrabulbar seminal vesicle; ejaculatory duct opening subterminally through the ventral side of the penis papilla; muscular penis bulb composed of intermingled longitudinal and circular muscles; two ovaries positioned ventrally at approximately one-third of the distance between the brain and the root of the pharynx; oviducts opening separately and at different levels into the vaginal portion of the bursal canal; shell glands opening into the proximal, vaginal portion of the bursal canal; very large copulatory bursa, occupying almost the entire ample space between the posterior wall of the pharyngeal pocket and the penis bulb; bursal canal lined with a nucleated epithelium and covered by subepithelial layers of longitudinal muscles, followed by layers of circular muscles; mixoploid karyotype, with diploid complements of 2n = 18 and triploid complements of 3n = 27 + 1B chromosomes, with all chromosomes being metacentric.
Morphological description. Live animals measuring up to 20 mm in length and 3 mm in width. Low triangular head provided with two blunt auricles and two eyes set in pigment-free patches (Fig. 4A). Dorsal surface pigmented light brown, while the ventral surface is paler. The pharynx is situated in the middle of the body and measures about 1/6 of the body length (Fig. 4A, B). It is covered with an epithelium, which is underlain by a subepithelial layer of longitudinal muscle followed by layers of circular muscles. The inner pharynx epithelium is underlain by subepithelial layers of circular muscles, followed by a layer of longitudinal muscle (Fig. 4B, C–D)
The numerous testes are located dorsally, extending from the posterior level of the ovaries into the posterior part of the body (Fig. 5A); the follicles show various stages of spermatogenesis (Fig. 5B). On either side of the body, a large sperm duct or vas deferens runs ventrally towards the posterior end of the body. At the level of the penis papilla, the sperm ducts turn dorso-medially and then narrow before individually, but symmetrically, opening into the intrabulbar seminal vesicle (Fig. 5C–F). This elongated seminal vesicle is lined with a columnar and nucleated epithelium and is surrounded by a well-developed coat of intermingled muscles. A small diaphragm is situated at the distal, posterior portion of the seminal vesicle and opens into the ejaculatory duct (Fig. 5D). The latter is lined with a columnar and nucleated epithelium, but any surrounding musculature was not observed. From its point of origin near the diaphragm, the ejaculatory duct at first follows a central course through the penis papilla for a short distance, but then turns towards the ventral side of the papilla where it opens subterminally to the exterior (Figs 5E, 6A, 7).
The highly glandular, more or less barrel-shaped penis papilla is situated within the male atrium, which communicates with a small common atrium via a constriction (Fig. 6B). The papilla is covered by a columnar, nucleated epithelium (Fig. 6A), under which lies a layer of circular muscles along most of its extent. Numerous ducts from abundant erythrophilic bulbar and extra-bulbar glands traverse a wide zone within the penis papilla, eventually releasing their secretions into the posterior section of the ejaculatory duct (Fig. 6A, B). Additionally, some other penial glands are located in the parenchymal region of the penis papilla and discharge their secretions mainly through the epithelium near the tip of the papilla.
The ovaries are situated ventrally, immediately above the nerve cords at approximately one-third of the distance between the brain and the root of the pharynx and about 120 μm behind the eyes (Fig. 6C); the gonads show various stages of normal oogenesis (Fig. 6D, E). The oviducts run dorsally to the ventral nerve cords until arriving shortly posterior to the gonopore, where they turn dorso-medially to open separately into the vaginal section of the bursal canal. The oviducal openings are asymmetrical in that the left oviduct opens into the ventral portion of the bursal canal, near its communication with the atrium, whereas the right oviduct opens much higher into the bursal canal. The shell glands discharge their secretion into this portion of the bursal canal.
From its vaginal region, the bursal canal curves forwards, meanwhile diminishing in diameter. The canal is lined with a nucleated epithelium composed of cells of variable height, while it is coated with a subepithelial layer of longitudinal muscles, followed by a thick layer of circular muscles. At a level approximately at the anterior portion of the penis bulb, the bursal canal opens through the postero-dorsal wall of the copulatory bursa. This copulatory bursa is a very large and particularly elongated, sac-shaped structure that is located immediately anterior to the penis bulb and occupies almost the entire ample space between the posterior wall of the pharyngeal pocket and the penis bulb (Figs 6F, G, 7); a muscle layer around the copulatory bursa was not detected.
description: Published as part of Harrath, Abdel Halim, Mansour, Lamjed, Sluys, Ronald, Aldahmich, Waleed, Riutort, Marta & Alwasel, Saleh, 2025, The first Dugesia species (Platyhelminthes, Tricladida, Dugesiidae) documented for Saudi Arabia: an integrative description, pp. 113-127 in Zootaxa 5583 (1) on pages 118-122, DOI: 10.11646/zootaxa.5583.1.6, http://zenodo.org/record/14797933