identifier	taxonID	type	CVterm	format	language	title	description	additionalInformationURL	UsageTerms	rights	Owner	contributor	creator	bibliographicCitation
35B9C03B44245392A6F69A46B4149A49.text	35B9C03B44245392A6F69A46B4149A49.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Dugesia aconcinna Chen & Dong 2025	<div><p>Dugesia aconcinna Chen &amp; Dong sp. nov.</p><p>Figs 1, 2, 7, 8, 9</p><p>Collection site, habitat, and reproduction.</p><p>On 4 January 2019, the specimens were collected from a stream in the Qingfeng village, Leizhou Peninsula (Figs 1, 7 A, B), which is a volcanic spring at an altitude of 56 m a. s. l.; air temperature was 22 ° C and water temperature was 19 ° C. With respect to the  D. aconcinna population, six mature worms and five asexual worms were collected in the field. After ~ 5 months under laboratory conditions, all of the immature worms sexualised, although none of the worms (sexual in the field and the sexualised ones in the laboratory) produced any cocoons.</p><p>Material examined.</p><p>Holotype • ZMHNU -TPYC 5, <a href="https://tb.plazi.org/GgServer/search?materialsCitation.longitude=110.16361&amp;materialsCitation.latitude=21.2425" title="Search Plazi for locations around (long 110.16361/lat 21.2425)">Qingfeng village</a> (21°14'33"N, 110°9'49"E), alt. 56 m a. s. l., Suixi County, Guangdong Province, China, 4 January 2019, coll. Z-M Dong, L Wang and J-Z Chen, sagittal sections on 14 slides  .  Paratypes • RMNH.VER.22250.1, ibid., sagittal sections on 11 slides •  RMNH.VER.22250.2, ibid., sagittal sections on 10 slides •  ZMHNU -TPYC 1 -3, 6, 7, 11, ibid., sagittal sections on 14, 29, 15, 5, 21, 14 slides •  ZMHNU -TPYC 9, ibid., horizontal sections on 23 slides •  ZMHNU -TPYC 8, ibid., transverse sections on 19 slides .</p><p>Diagnosis.</p><p>Dugesia aconcinna is characterised by the presence of the following features: live, mature animals rather small; asymmetrical openings of the oviducts into the common atrium; vasa deferentia separately opening into the posterior portion of the seminal vesicle; penis papilla of a very characteristic shape, with the part housing the connecting duct, diaphragm, and ejaculatory duct being a cylindrical structure with a blunt tip, while at its right-hand side sits a large penial fold that attaches to the base of the penis papilla; ejaculatory duct following a ventrally displaced course through the penis papilla, after which it opens at the tip of the papilla; presence of a duct between diaphragm and seminal vesicle.</p><p>Description.</p><p>Body of both asexual and sexual live specimens is quite small, with the sexual worms being only 6–9 mm in length and 1.0– 1.2 mm in width. The low-triangular head is provided with two blunt auricles and two eyes, which are placed in pigment-free spots. Each pigmented eyecup houses numerous photoreceptor cells. The dorsal surface is yellow-brown, with many brown pigment granules and pale blotches all over the dorsal surface; the ventral surface is paler than the dorsal body surface (Fig. 7 C).</p><p>Pharynx situated in the mid-region of the body, measuring ~ 1 / 6 of the body length. Mouth opening located at the posterior end of the pharyngeal pocket. Outer pharyngeal musculature is composed of a thin, subepithelial layer of longitudinal muscles, followed by a thin layer of circular muscles; no extra inner layer of longitudinal muscles was observed. The inner pharyngeal musculature consists of a thick, subepithelial layer of circular muscle, followed by a thin layer of longitudinal muscle.</p><p>In those specimens in which we were able to examine the ovaries, most of the gonads were not hyperplasic (specimens TPYC 3, 5, 7, 8, and RMNH.VER.22250.1), excepting specimens TPYC 6, and 11, and RMNH.VER.22250.2. In general, the oval ovaries are situated at 1 / 3–1 / 4 of the distance between the brain and the root of the pharynx, occupying ~ 1 / 4 of the dorso-ventral space. The oviducts arise from the dorsal wall of the ovaries, then turn to the ventral side and run in a caudal direction to the level of the genital pore. Subsequently, the left oviduct bends dorsally to open into the common atrium, while the right oviduct exhibits a much more pronounced curvature towards the dorsal body surface, after which it recurves in antero-ventral direction to open into the most ventral, proximal portion of the bursal canal, at the point where the latter communicates with the common atrium (Figs 8 A, 9 A). Thus, the right oviducal branch opens dorsally to the left one. The oviducts are lined with a columnar, infranucleated epithelium.</p><p>The sac-shaped copulatory bursa lies immediately behind the pharyngeal pocket and may occupy the entire dorso-ventral space or, at least, a considerable portion of it. The bursa is lined with a columnar, vacuolated epithelium with basal nuclei and is devoid of any surrounding musculature (Figs 8 B – D, F, 9). Near its communication with the postero-dorsal section of the bursa, the bursal canal is rather narrow and may occupy ~ 1 / 8 of the dorso-ventral space (Figs 8 F, 9 A). From thereon, the canal expands somewhat in diameter while it runs in a caudal direction to the left side of the male copulatory apparatus. At the level of the gonopore, the posterior section of the canal exhibits a rather abrupt, ventrally directed bend, after which it opens into the common atrium (Fig. 9 A). The bursal canal is lined with cylindrical, infranucleated, ciliated cells and is surrounded by a subepithelial layer of longitudinal muscles, followed by a layer of circular muscle; an extra outer layer of longitudinal musculature, forming the ectal reinforcement, extends from the copulatory bursa to the atrium. Erythrophil shell glands open into the vaginal region of the bursal canal, near the oviducal openings.</p><p>The numerous, well-developed testes are situated dorsally and provided with mature spermatozoa. On either side of the midline of the body, testicular follicles are arranged in eight or nine longitudinal zones and extend from the posterior level of the ovaries to almost the posterior end of the body.</p><p>At the level of the pharyngeal pocket, the vasa deferentia expand to form spermiducal vesicles, which are packed with mature spermatozoa (Fig. 9). Upon reaching the large penis bulb, the vasa deferentia turn dorso-medially and quickly decrease very much in diameter while penetrating the wall of the bulb. Subsequently, the sperm ducts open separately and symmetrically into the mid-posterior section of the seminal vesicle, near the point where it communicates with the connecting duct that leads to the diaphragm. The sperm ducts are lined with a nucleated epithelium and surrounded by a layer of circular muscle.</p><p>The voluminous, oval seminal vesicle is lined by a flat, nucleated epithelium and is surrounded by a layer of intermingled muscle fibres. The seminal vesicle occupies ~ 2 / 5 of the dorso-ventral space and is located in the ventral portion of the penis bulb, close to the ventral body surface (Figs 8 B – D, 9). Although the penis bulb is rather shallow, it is, nevertheless, a large structure, occupying almost the entire dorso-ventral space (Figs 8 B – D, 9). A relatively long and broad duct connects the seminal vesicle with a small diaphragm, the latter leading to the ejaculatory duct (Figs 8 C, D, 9). This interconnecting duct is lined by an infranucleated epithelium and is surrounded by a layer of intermingled muscle fibres. The small diaphragm is located at the level of the root of the penis papilla and receives the abundant secretion of erythrophil penis glands (Figs 8 C, D, 9). Both the connecting duct and the ejaculatory duct run a ventrally displaced course through the penis papilla, with the relatively broad ejaculatory duct opening at the tip of the papilla (Figs 8 D, F, 9). The ejaculatory duct is lined with a cuboidal, infranucleated epithelium and is devoid of any surrounding musculature.</p><p>The penis papilla has a very characteristic shape. The part that houses the connecting duct, diaphragm, and ejaculatory duct is a cylindrical structure with a blunt tip. This seems to be a rather symmetrical portion of the papilla but it should be noted that it concerns a lateral, left-hand part of the penis papilla. The right-hand part of the papilla develops a large penial fold (Figs 8 E, 9 B) that attaches to the base of the penis papilla. Penis papilla and penial fold are covered with a nucleated epithelium, which is underlain by a subepithelial layer of circular muscle, followed by a layer of longitudinal muscle fibres (Figs 8 B – F, 9).</p><p>The genital atrium is divided into a common atrium and male atrium. The common atrium communicates with a gonoduct, which leads to the ventral gonopore; the gonoduct is lined by a columnar epithelium and receives the openings of cement glands (Fig. 9).</p><p>Etymology.</p><p>The specific epithet is derived from the Latin adjective  aconcinna, asymmetrical, and alludes to the asymmetrical penial fold as well as the asymmetrical oviducal openings into the bursal canal.</p><p>Discussion.</p><p>A good number of  Dugesia species possesses so-called penial annexes in the form of penial folds, which sometimes were indicated by the term adenodactyl. However, the term adenodactyl should not be applied to these penial annexes (Stocchino et al. 2017). Penial folds are located at the base of the penial papilla and are usually covered by the musculature of the penis bulb; folds may be of the parenchymatic-muscular type or of the parenchymatic-musculo-glandular type (Stocchino et al. 2017). Furthermore, penial folds may be located at both the ventral and dorsal side of the penis papilla, albeit the ventral fold may be smaller than the dorsal one, or a single fold may be restricted to the dorsal, dorso-lateral, or lateral portion of the papilla. Such a single fold is present in ~ 20 species of  Dugesia . For the present comparative discussion, it suffices to concentrate on those species that exhibit a dorso-lateral or lateral penial fold more or less comparable to that of  D. aconcinna, viz.,  D. arcadia de Vries, 1988,  D. benazzii Lepori, 1951,  D. golanica Bromley &amp; Benazzi, 1991,  D. hoidi Dols-Serrate, Stocchino &amp; Riutort, 2024,  D. iranica Livanov, 1951,  D. libanica Bromley &amp; Benazzi, 1991,  D. mariae Stocchino, Dols-Serrate &amp; Riutort, 2023,  D. minotauros de Vries, 1984 . However, all of these species differ from  D. aconcinna in the absence of a connecting duct between the seminal vesicle and the diaphragm, perhaps excepting  D. izuensis Katô, 1943 (cf. Sluys et al. 1998: table II; Dols-Serrate et al. 2024). For  D. izuensis a diaphragm was not described but it is presumed that the abundant openings of eosinophilic penial glands approximately halfway into the ejaculatory duct (Kato 1950; Kawakatsu 1983) coincides with the location of the diaphragm, which is presumably very small. However, in other aspects  D. izuensis is rather different from  D. aconcinna . For example, in  D. izuensis the penis papilla is a massive and plump structure, whereas the papilla in  D. aconcinna is cylindrical. Other differences concern the penial fold. In  D. izuensis the fold has the shape of a conical papilla with the central part filled with cyanophilic secretion, in contrast to the flap-like fold of  D. aconcinna that lacks any secretions.</p><p>With respect to the shape and position of its penial fold,  D. aconcinna resembles  D. benazzii,  D. hoidi, and  D. mariae, all of which possess a flap-like penial fold that extends dorso-laterally of the penis papilla, which holds true also for  D. minotauros (de Vries 1984; Dols-Serrate et al. 2024). However, in all of these species the fold is situated on the left side of the penis papilla, in contrast to  D. aconcinna in which the fold extends over the right side of the papilla. But there are also other differences. In  D. benazzii and  D. hoidi, the two vasa deferentia follow highly asymmetrical trajectories before opening, equally asymmetrically, into the seminal vesicle. In contrast, in both  D. mariae and  D. aconcinna the sperm ducts follow symmetrical trajectories. In  D. iranica the penial fold sits also on the left side of the penis papilla, albeit it is not a flap-like fold, but a conical structure of variable size, which sometimes may be as large as the penis papilla; it is of the musculo-glandular type. All of this is different from the situation in  D. aconcinna . Similarly to  D. aconcinna,  D. libanica possesses also a relatively long, cylindrical penis papilla with a blunt tip, with at its right-hand side a well-developed penial fold. In contrast to  D. aconcinna, the fold of  D. libanica is not flap-like but consists of a pear-shaped papilla, located dorsally to the right of the penis papilla, that may reach a length of ~ 3 / 4 of the penial papilla (Bromley and Benazzii 1991). Notably, none of above-mentioned species belongs to the same clade as  D. aconcinna . Although, these species ( D. adunca,  D. ancoraria,  D. bengalensis, and  D. notogaea) are closely related molecularly, they can be easily distinguished from  D. aconcinna by anatomical features.</p></div>	https://treatment.plazi.org/id/35B9C03B44245392A6F69A46B4149A49	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Pensoft via Plazi	Wang, Lei;Chang, Yi-Fang;Sun, Xin-Xin;Sluys, Ronald;Liu, De-Zeng;Dong, Zi-Mei;Chen, Guang-Wen	Wang, Lei, Chang, Yi-Fang, Sun, Xin-Xin, Sluys, Ronald, Liu, De-Zeng, Dong, Zi-Mei, Chen, Guang-Wen (2025): Two new species of freshwater planarian from Hainan Island and Leizhou Peninsula, southern China (Platyhelminthes, Tricladida, Dugesiidae). ZooKeys 1233: 289-313, DOI: 10.3897/zookeys.1233.142976
6A0099F70FD45834BE0B3762F9816AF2.text	6A0099F70FD45834BE0B3762F9816AF2.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Dugesia saccata Chen & Dong 2025	<div><p>Dugesia saccata Chen &amp; Dong sp. nov.</p><p>Figs 1, 2, 3, 4, 5, 6</p><p>Collection site, habitat, and reproduction.</p><p>On 24 February 2018, specimens were collected from a freshwater stream in the Yingge Mountains, Hainan Island (Figs 1, 3 A), which is located within a national Nature Reserve at an altitude of 430 m a. s. l.; air temperature was 24 ° C and water temperature was 21 ° C. In the population of  D. saccata, all worms were asexual at collection in the field, and under laboratory conditions were fissiparous. During a period of ~ 4 months, each of the ten specimens sexualised; in the first month only two sexualised individuals were found, while at the end of the fourth month ten sexual animals were present. After 18 months of culturing, sexualised worms produced&gt; 10 cocoons. The spherical cocoons (1.3 mm in diameter) were dark brownish and provided with a stalk. Thus far, none of the cocoons hatched, most likely infertile. During laboratory culturing, the sexualised worms sometimes lost their copulatory apparatus and, subsequently, returned to the asexual mode of reproduction.</p><p>Material examined.</p><p>Holotype • ZMHNU -YZCB 1, <a href="https://tb.plazi.org/GgServer/search?materialsCitation.longitude=109.645&amp;materialsCitation.latitude=18.768333" title="Search Plazi for locations around (long 109.645/lat 18.768333)">Yongzhong village</a> (18°46'6"N, 109°38'42"E), alt. 430 m a. s. l., Wuzhishan City, Hainan Province, China, 24 February 2018, coll. G-W Chen, D-Z Dong and co-workers, sagittal sections on 28 slides  .  Paratypes • RMNH.VER.22249.1, ibid., sagittal sections on 12 slides •  RMNH.VER.22249.2, ibid., sagittal sections on 20 slides •  ZMHNU -YZCB 2, 3, 6, ibid., sagittal sections on 19, 18, and 26 slides, respectively •  ZMHNU -YZCB 5, ibid., horizontal sections on 16 slides •  ZMHNU -YZCB 8, ibid., transverse sections on 35 slides .</p><p>Diagnosis.</p><p>Dugesia saccata is characterised by the presence of the following features: symmetrical openings of the oviducts into the most proximal section of the bursal canal, near the point where the latter communicates with the atrium; a sac-shaped expansion at the knee-shaped bend of bursal canal; vasa deferentia opening symmetrically into posterior portion of the seminal vesicle; ventrally displaced ejaculatory duct with subterminal opening; a duct between diaphragm and seminal vesicle; mixoploid karyotype, with diploid chromosome portraits of 2 n = 2 x = 14, and triploid complements of 2 n = 3 x = 21, with all chromosomes being metacentric.</p><p>Karyology.</p><p>Seven intact specimens were randomly selected to prepare metaphase plates. In a total of 157 metaphase plates that were examined, 42 plates exhibited diploid chromosome complements of 2 n = 2 x = 14, while in 104 plates chromosome complements were triploid with 2 n = 3 x = 21 chromosomes; chromosome complements on the remaining 11 plates could not be determined, due to either lack of well dispersed chromosomes or over-dispersed sets of chromosomes. All seven specimens exhibited mixoploid chromosome complements, with all chromosomes being metacentric. Karyotype parameters, including relative length, arm ratio, and centromeric index, are given in Table 2. Chromosomal plates and an idiogram are shown in Fig. 4.</p><p>Morphology.</p><p>In sexualised living specimens, the body measured 14–22 mm in length and 1.3–1.6 mm in width. Triangular head provided with two blunt auricles and two eyes, which are placed in pigment-free spots. Each pigmented eyecup houses numerous photoreceptor cells. The dorsal surface is taupe, the ventral surface is paler in colour than the dorsal one (Fig. 3 C).</p><p>Pharynx situated at the mid-region of the body, measuring ~ 1 / 5 of the body length. Mouth opening located at posterior end of the pharyngeal pocket. The outer pharyngeal musculature is composed of a subepithelial layer of longitudinal muscles, followed by a layer of circular muscles. The inner pharyngeal musculature consists of a thick subepithelial layer of circular muscles, followed by a thin layer of longitudinal muscles.</p><p>The hyperplasic ovaries are located at 1 / 3–1 / 5 of the distance between the brain and the root of the pharynx, occupying ~ 1 / 2 of the dorso-ventral space, with several scattered masses. The oviducts arise from the dorsal wall of the ovaries, then turn to the ventral side and run in a caudal direction to the level of the genital pore, after which they curve dorso-medially to open separately and symmetrically into the bursal canal, near the point where the latter communicates with the atrium (Fig. 5 A). Cyanophil shell glands discharge their secretion into the vaginal region of the bursal canal, at the level of the oviducal openings.</p><p>The small, dorsally located testes are poorly developed and provided with only a few mature spermatozoa. As a consequence, we found spermatozoa to be present in the vasa deferentia only in specimens YZCB 3, 5, 6, and 8, as well as in RMNH.VER.22249.2. Testicular follicles are arranged on either side of the midline of the body in four or five longitudinal zones, extending from the posterior level of the ovaries to almost the posterior end of the body.</p><p>At the level of the penis bulb, the sperm ducts curve towards the dorsal body surface, then penetrate the ventral wall of the penis bulb to open separately into the seminal vesicle. The precise approach of the ducts to the seminal vesicle differs somewhat between specimens. In the holotype one sperm duct exhibits a short dorso-ventral recurvature before opening into the proximal section of the duct that leads from the seminal vesicle to the diaphragm; the other duct opens at the same position but has a much more direct approach (Fig. 6). In paratype YZCB- 6 there is an even more distinctly asymmetrical approach of the sperm ducts, with one duct having a dorsal approach, after a well-developed dorso-ventral recurvature, opening in the antero-lateral portion of the seminal vesicle, again close to the duct leading to the diaphragm. The other sperm duct does not show the recurvature and opens directly into the proximal section of the connecting duct between seminal vesicle and diaphragm. In contrast, in paratype YZCB- 8 both ducts exhibit a well-developed recurvature before symmetrically opening into the latero-dorsal portions of the seminal vesicle, close to the point where the connecting duct opens into the seminal vesicle (Fig. 5 B).</p><p>The sperm ducts are lined with nucleated cells and surrounded by a layer of circular muscles. The oval-shaped, rather large seminal vesicle is lined by a flat, nucleated epithelium and is surrounded by a layer of irregularly crosswise arranged muscle fibres. The postero-ventral section of the seminal vesicle gives rise to a duct that is lined by an infranucleated epithelium, which is underlain by a subepithelial layer of intermingled muscle fibres and via a small diaphragm opens into the ejaculatory duct (Figs 5 D, 6). The small diaphragm is located at approximately the root of the penis papilla and receives the abundant secretion of erythrophil penis glands (Fig. 5 D). The ejaculatory duct, which is lined with a cuboidal, infranucleated epithelium, is devoid of any discernible musculature and follows a ventrally displaced course through the penis papilla, opening subterminally at its tip (Figs 5 D, 6). Cyanophil penis glands discharge abundant secretion into the central and distal portion of the ejaculatory duct.</p><p>Because of the ventrally displaced course of the ejaculatory duct, the penis papilla is asymmetrical, with its dorsal lip being considerably larger than the ventral one (Figs 5 D, 6). The cylindrical penis papilla has an oblique, ventro-caudal orientation and is covered by a nucleated epithelium, which is underlain by a subepithelial layer of circular muscle, followed by a layer of longitudinal muscle fibres (Figs 5 D, 6).</p><p>The copulatory bursa is a large sac-shaped structure that may occupy the entire dorso-ventral space (paratype YZCB- 6), while in other specimens it extends well over the central longitudinal axis of the body but does not fully occupy the dorso-ventral space (e. g., holotype YZCB- 1; Fig. 6). The bursa is lined by a vacuolated epithelium with basal nuclei and is almost devoid of any surrounding musculature. The bursal canal arises from the postero-dorsal wall of the bursa, after which it runs in a caudal direction to the left side of the male copulatory apparatus (Figs 5 C, 6 A). The rather broad bursal canal occupies ~ 1 / 4 of the dorso-ventral space. At the level of the gonopore it decreases somewhat in diameter, whereafter it gives rise to a saccate posterior extension (Figs 5 C, 6). The antero-ventral, knee-shaped bend in the bursal canal arises from the ventral wall of the saccate portion and communicates with the common atrium (Figs 5 C, 6).</p><p>The bursal canal is lined with a ciliated epithelium with basal nuclei. Particularly the dorsal wall of the canal may be thrown into several folds. It is noteworthy that the ventral wall of the bursal canal is lined with cylindrical cells, whereas the dorsal wall is composed of cuboidal or even flat cells; the saccate expansion is also lined with a low epithelium. The bursal canal is surrounded by a subepithelial layer of longitudinal muscles, followed by a layer of circular muscle that is particularly well developed on the ventral wall of the canal; an extra outer layer of longitudinal musculature, forming the ectal reinforcement, extends from the atrium to 2 / 3 on the bursal canal.</p><p>The common atrium communicates with a gonoduct, which is lined by a columnar epithelium and receives the openings of erythrophil cement glands (Fig. 6).</p><p>Etymology.</p><p>The specific epithet is derived from the Latin noun saccus, bag, and alludes to the sac-shaped expansion at the knee-shaped bend of the bursal canal.</p><p>Discussion.</p><p>There is one character that immediately sets  D. saccata apart from all of its known congeners, the sac-shaped expansion on the posterior section of the bursal canal, near the knee-shaped bend of the canal. This is slightly reminiscent of a situation in  Dugesia aethiopica Stocchino, Corso, Manconi &amp; Pala, 2002, in which the posterior section of the bursal canal, immediately before receiving the separate openings of the oviducts, is expanded in lateral direction and gives rise to several large folds (Sluys 2007). However, this is merely a superficial resemblance to the situation in  D. saccata, and these two species also differ in many other features. For example,  D. aethiopica shows a horizontal approach of the bursal canal to the atrium, which represents a rare feature among species of  Dugesia and is also absent in  D. saccata . In  Dugesia arabica Harrath &amp; Sluys, 2013 the bursal canal is considerably expanded as well as highly folded in the region of the oviducal openings (Harrath et al. 2013). However, this situation differs from that in  D. saccata in that the expansion sits near the oviducal openings, whereas in  D. saccata the sac-shaped expansion occurs dorsally, or entally to the openings of the oviducts into the bursal canal. Another difference between these two species concerns the presence of a duct between seminal vesicle and diaphragm in  D. saccata and absence of such a duct in  D. arabica .</p><p>Two characteristic features of  D. saccata may be found also in other species of  Dugesia, a ventrally displaced ejaculatory duct with subterminal opening and the presence of a duct between the seminal vesicle and the diaphragm. Besides  D. saccata, these two character states are also expressed, among others, in the three Chinese species  D. majuscula,  D. umbonata Song &amp; Wang, 2020, and  D. verrucula Chen &amp; Dong, 2021 (Song et al. 2020; Wang et al. 2021 a, b). However, in contrast to  D. saccata, in both  D. majuscula and  D. umbonata the ejaculatory duct has a subterminal dorsal opening at the tip of the penis papilla, while  D. verrucula exhibits a permanent dorsal bump near the root of the penis papilla, which is absent in  D. saccata . Another difference concerns the presence of a large muscularised hump on the dorsal surface of the bursal canal of  D. umbonata, which is absent in  D. saccata . Although these three species ( D. umbonata,  D. verrucula, and  D. saccata) belong to the same clade, they are molecularly well-differentiated. On the other hand, while  D. saccata,  D. pendula,  D. tumida, and  D. majuscula belong to the same small clade, they are anatomically well differentiated.</p><p>In  Dugesia species, the basic chromosome number concerns three types, 7, 8, and 9. Previous studies have shown that in China number 8 is the most frequent type, while 7 is much rarer (Wang et al. 2024). In that respect, it is noteworthy that the basic chromosome number in  D. saccata is n = 7, which is shared only with  D. pendula,  D. hepta Pala, Casu, &amp; Vacca, 1981,  D. batuensis Ball, 1970, and  D. ryukyuensis Kawakatsu, 1976 (Kawakatsu et al. 1976; Pala et al. 1981; Khang et al. 2017; Wang et al. 2024). However,  D. pendula exhibits an aneuploid plus mixoploid karyotype, with diploid (2 n = 2 x = 14 + 0-1 B-chromosome) and triploid (2 n = 3 x = 21 + 0-1 B-chromosome) sets, while  D. batuensis exhibits six metacentric chromosomes and one subtelocentric chromosome, and  D. ryukyuensis shows six metacentric chromosomes and one submetacentric chromosome, which is the case also in  D. hepta . In contrast,  D. saccata exhibits a mixoploid karyotype with diploid (2 n = 2 x = 14) and triploid (2 n = 3 x = 21) sets, with all chromosomes being metacentric, thus contrasting with the chromosome complements of the other species.</p><p>In fact,  D. saccata produced infertile cocoons and only showed asexual reproduction by means of fission, which corresponds with its poorly developed or hyperplasic ovaries and the triploid chromosome complement. It has been established that in such abnormal ovaries the oocytes are anomalous, thus preventing regular oogenesis (Harrath et al. 2014).</p></div>	https://treatment.plazi.org/id/6A0099F70FD45834BE0B3762F9816AF2	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Pensoft via Plazi	Wang, Lei;Chang, Yi-Fang;Sun, Xin-Xin;Sluys, Ronald;Liu, De-Zeng;Dong, Zi-Mei;Chen, Guang-Wen	Wang, Lei, Chang, Yi-Fang, Sun, Xin-Xin, Sluys, Ronald, Liu, De-Zeng, Dong, Zi-Mei, Chen, Guang-Wen (2025): Two new species of freshwater planarian from Hainan Island and Leizhou Peninsula, southern China (Platyhelminthes, Tricladida, Dugesiidae). ZooKeys 1233: 289-313, DOI: 10.3897/zookeys.1233.142976
