Addition to the known diversity of Chinese freshwater planarians: integrative description of a new species of Dugesia Girard, 1850 (Platyhelminthes, Tricladida, Dugesiidae) Author Liu, Yi Shenzhen Key Laboratory of Marine Bioresource and Eco-environmental Science, College of Life Sciences and Oceanography, Shenzhen University, Shenzhen, Guangdong, China Author Song, Xiao-Yu Shenzhen Key Laboratory of Marine Bioresource and Eco-environmental Science, College of Life Sciences and Oceanography, Shenzhen University, Shenzhen, Guangdong, China & School of Urban Planning and Design, Shenzhen Graduate School, Peking University, Shenzhen, China Author Sun, Zhong-Yin Shenzhen Key Laboratory of Marine Bioresource and Eco-environmental Science, College of Life Sciences and Oceanography, Shenzhen University, Shenzhen, Guangdong, China Author Li, Wei-Xuan https://orcid.org/0000-0001-8853-3589 State Key Laboratory of Protein and Plant Gene Research, Center for Bioinformatics, School of Life Sciences, Peking University, Beijing, China Author Sluys, Ronald https://orcid.org/0000-0002-9776-3471 Naturalis Biodiversity Center, P. O. Box 9517, Leiden, 2300 RA, Netherlands Author Li, Shuang-Fei Shenzhen Key Laboratory of Marine Bioresource and Eco-environmental Science, College of Life Sciences and Oceanography, Shenzhen University, Shenzhen, Guangdong, China sfli@szu.edu.cn Author Wang, An-Tai Shenzhen Key Laboratory of Marine Bioresource and Eco-environmental Science, College of Life Sciences and Oceanography, Shenzhen University, Shenzhen, Guangdong, China text Zoosystematics and Evolution 2022 2022-06-29 98 2 233 243 http://dx.doi.org/10.3897/zse.98.83184 journal article http://dx.doi.org/10.3897/zse.98.83184 1860-0743-2-233 E8B38FE7A90443D28024EE0745E415C7 0F1D0E4082125DACB7D50B7767BFED31 Dugesia gemmulata Sun & Wang sp. nov. Material examined. Holotype : IZCAS PLA-0101, a rural streamlet in Qingzhen City , Guizhou , China , 26°33.83'N , 106°13.65'E , 3 February 2018 , coll. Zhong-Yin Sun , sagittal sections on 20 slides. Paratypes : IZCAS PLA-0102, ibid., sagittal sections on 30 slides; IZCAS PLA-0103, ibid., horizontal sections on 18 slides. Habitat. Specimens were collected from a rural streamlet ( 26°33.83'N , 106°13.65'E ) at an altitude of about 1,400 m above sea level (a.s.l.) in Qingzhen City, Guizhou, China (Fig. 1A ). The animals were collected from the underside of small pebbles in the riverbed (Fig. 1B, C ), which had a water depth of 20-50 cm. Water temperature was about 19.9 °C, while air temperature was about 21.8 °C. Diagnosis. Dugesia gemmulata is characterised by the following characters: ventral part of the most posterior section of the bursal canal, just anteriorly to its point of communication with the common atrium, provided with a voluminous, ellipsoidal muscular swelling; sac- or egg-shaped seminal vesicle situated near the ventral body surface in anterior portion of the penis bulb; postero-dorsal wall of seminal vesicle communicates with a narrow duct that first runs almost vertically but then shows a postero-dorsally directed loop before connecting with a small diaphragm; ejaculatory duct opening terminally or subterminally; penis papilla asymmetrical, with dorsal lip provided with a bump; oviducts opening asymmetrically into female copulatory apparatus, with the left oviduct opening into the common atrium and the right oviduct opening into the vaginal section of the bursal canal. Etymology. The specific epithet is derived from the Latin gemmula , small bud, and alludes to the muscular swelling on the ventral wall of the bursal canal. Description. Body size of live, sexualised specimens ranged from 16.12 to 22.75 mm in length and 1.93 to 2.87 mm in width ( n = 3; Fig. 3A, B ), while asexual specimens ranged from 5.12 to 8.31 mm in length and 0.91 to 1.32 mm in width ( n = 3). Sexualised and asexual individuals exhibited no differences in appearance, except for the body size. The following measurements are based on sexualised individuals. At a distance varying between 0.46 mm and 0.56 mm from the anterior body margin, two eyes are present in the middle of the low-triangular head, situated in pigment-free patches ( n = 3; Fig. 3C ). Each kidney-shaped eyecup contains numerous retinal cells. Unpigmented auricular grooves are marginally placed just posteriorly to the blunt auricles (Fig. 3C ). Figure 3. Dugesia gemmulata . A. Habitus of live, sexualised animal in dorsal view; B. Habitus of live, sexualised animal in ventral view; C. Anterior end, dorsal view; D. Anterior end, ventral view, showing ovaries. Dorsal body surface with a brown ground colour, overlain with scattered black pigmentation and provided with a thin, pale median line that runs from anterior to the eyes to the tail end (Fig. 3A-C ); ventral surface much paler than dorsal surface (Fig. 3D ). The cylindrical pharynx lies more or less in the middle of the body and measures about 1/7 of the total body length, i.e., about 2.07-2.77 mm in length and 0.16-0.32 mm in width ( n = 3; Fig. 3A ). The entire pharynx is covered with a nucleated epithelium (Fig. 4B ). The outer epithelium of the pharynx is underlain by 1-3 subepithelial layers of circular muscles, followed by a thin layer of longitudinal muscle fibres (Fig. 4B ). The inner pharynx epithelium, which is densely ciliated, is underlain by a thin subepithelial layer of longitudinal muscle fibres, followed by 3-5 layers of circular muscles (Fig. 4B ). The mouth opening is located at a distance of about 1/3-1/2 of the body length, as measured from the posterior body margin; the mouth is situated at the posterior end of the pharyngeal cavity ( n = 3; Fig. 3B ). Figure 4. Dugesia gemmulata , holotype PLA-0101, sagittal sections and reconstructions of the copulatory apparatus. A. Photomicrograph showing ovaries and the opening of the oviduct; B. Photomicrograph showing musculature of the pharynx; C. Photomicrograph showing copulatory bursa, seminal vesicle, interconnecting duct, penis glands, ejaculatory duct, penis papilla, male atrium and cement glands; D. Photomicrograph showing bursal canal and muscular swelling; E. Reconstruction male copulatory apparatus; F. Reconstruction female copulatory apparatus. Testes could not be discerned. The large, elongated penis bulb consists of intermingled longitudinal and circular muscle fibres. The vasa deferentia open asymmetrically into the seminal vesicle, with the right vas deferens opening into the mid-anterior portion of the seminal vesicle in specimen PLA-0101 and into the mid-dorsal portion in specimen PLA-0102, while the left vas deferens opens into the postero-dorsal part of the seminal vesicle in specimen PLA-0101 and into the postero-ventral part in specimen PLA-0102 (Figs 4E , 5C ). The sac- or egg-shaped seminal vesicle is situated near the ventral surface in the anterior portion of the penis bulb; it is lined with a nucleated epithelium and surrounded by 1-2 layers of longitudinal muscles (Figs 4C, E , 5A, C ). From the postero-dorsal wall of the seminal vesicle arises a narrow duct, lined with a glandular, nucleated epithelium and surrounded by 1-3 layers of circular muscle fibres, which first runs almost vertically but then shows a postero-dorsally directed loop before connecting with a small diaphragm (Figs 4C, E , 5A, C ). Figure 5. Dugesia gemmulata , paratype PLA-0102, sagittal sections and reconstructions of the copulatory apparatus. A. Photomicrograph showing copulatory bursa, seminal vesicle, diaphragm, penis glands, penis papilla, male atrium, common atrium, shell glands, cement glands and gonopore; B. Photomicrograph showing bursal canal and muscular swelling; C. Reconstruction male copulatory apparatus; D. Reconstruction female copulatory apparatus. The very small diaphragm is lined by a nucleated epithelium, which is underlain by 1-2 layers of circular muscle and is pierced by the openings of erythrophil penial glands (Figs 4C, E , 5A, C ). The diaphragm leads to a broad ejaculatory duct, which is lined by an infranucleated epithelium that is underlain with 1-3 layers of circular muscle fibres (Figs 4C, E , 5A, C ). The ejaculatory duct runs more or less centrally through the penis papilla and opens subterminally through the ventral wall of the penis papilla in specimens PLA-0101 and PLA-0103, while in specimen PLA-0102 the ejaculatory duct runs a ventrally displaced course and opens at the tip of the papilla (Figs 4C, E , 5A, C ). The penis papilla is asymmetrical, in that its dorsal lip is larger than the ventral one, while the former carries a bump (Figs 4C, E , 5A, C ). The papilla is covered by a thin, nucleated epithelium, which is underlain by a layer of longitudinal muscles, followed by 2-3 layers of circular muscles, the latter being thicker at the base of penis papilla (Figs 4C, E , 5A, C ). The ovaries are hyperplasic, with several scattered masses distributed in the body region directly posterior to the brain, filling up the entire dorso-ventral space (Fig. 4A ). The left oviduct arises from the mid-lateral section of the ovary, while the right duct arises from a more antero-lateral section of the ovary (Fig. 4A ). From the ovaries, the oviducts, which are lined with an infranucleated epithelium, run backwards and continue their course on either side of the pharyngeal pocket (Figs 4F , 5D ). Immediately posterior to the gonopore, the oviducts turn medially to open asymmetrically into the female copulatory apparatus, with the left oviduct opening into the common atrium and the right oviduct opening more dorsally into the vaginal section of the bursal canal (Figs 4E , 5C ). The large, irregularly egg-shaped copulatory bursa is situated immediately anterior to the penis bulb and is surrounded by a thin layer of intermingled longitudinal and circular muscle fibres (Figs 4C-F , 5 ). The bursal canal arises from the posterior surface of the copulatory bursa and runs caudally to the left of the copulatory apparatus, subsequently communicating with the dorsal portion of the common atrium (Figs 4E, F , 5C, D ). The bursal canal is lined by a nucleated, glandular epithelium, which is underlain by a subepithelial layer of longitudinal muscle fibres, followed by 2-5 layers of circular fibres. The coat of circular fibres on the ventral side of the bursal canal varies from 3-5 layers, while that on the dorsal side is thinner, being 2-3 layers thick. Furthermore, the ventral part of the most posterior section of the bursal canal, just anteriorly to its point of communication with the common atrium, carries a voluminous, ellipsoidal muscular swelling that measures about 348-481 μm in anterior-posterior direction ( n = 3; Figs 4D, F , 5B, D , 6 ). The swelling consists of irregular, nucleated mesenchymal cells and is surrounded by a coat of intermingled muscles; there are also muscle fibres traversing the swelling in all directions in a more loosely arranged, irregular and reticulated way (Figs 4D, F , 5B, D , 6 ). Figure 6. Dugesia gemmulata , paratype PLA-0103, horizontal sections. A, B. Photomicrographs showing the muscular swelling. The male atrium is lined by an epithelium consisting of nucleated, cylindrical cells and is surrounded by a subepithelial layer of circular muscles, followed by 1-2 layers of longitudinal muscles. The male atrium communicates with the common atrium via a pronounced constriction (Figs 4C-E , 5A, C, D ). The common atrium is lined with an infranucleated epithelium, which is underlain by 1-2 layers of circular muscle, followed by a layer of longitudinal muscle. The common atrium opens ventrally through the gonopore, which is located at 1/3-1/4 of the body length ( n = 3), as determined from the posterior body margin (Figs 4E, F , 5A, C, D ). Massive shell glands are distributed posteriorly to the common atrium and near the vaginal section of the bursal canal (Figs 4E , 5A, C ). Near its opening into the common atrium, the bursal canal receives the cyanophilic secretion of the shell glands (Figs 4E , 5A, C ). Erythrophilic cement glands open into the ventral portion of the common atrium and into the gonoduct (Figs 4C, E , 5A, C ).