Cratera obsidiana Amaral, Boll & Leal-Zanchet,
Boll, Piter Kehoma, Amaral, Silvana Vargas Do & Leal-Zanchet, Ana Maria, 2019, Two new land planarian species (Platyhelminthes: Tricladida: Geoplanidae) from protected areas in southern Brazil, Zootaxa 4664 (4), pp. 535-550: 536-542
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|Cratera obsidiana Amaral, Boll & Leal-Zanchet|
Geoplana sp. 6 in Baptista, Oliveira & Leal-Zanchet 2010
Geoplana sp. 6 in Baptista & Leal-Zanchet 2010
Etymology: The specific name is a noun in apposition and refers to the bright glossy black color of the dorsum, resembling the volcanic rock obsidian.
Type material. Holotype: MZUSP PL.2158: leg. S. M. Oliveira, 10 September 2006, State Park of Turvo (27°00’ to 27°20’S, 53°40’ to 54°10’W), Derrubadas, state of Rio Grande do Sul, Brazil—anterior tip: transverse sections on 18 slides; anterior region at the level of the ovaries: sagittal sections on 30 slides; pre-pharyngeal region: transverse sections on 6 slides; pharynx: sagittal sections on 14 slides; copulatory apparatus: sagittal sections on 26 slides.GoogleMaps
Paratypes: Three specimens collected in the same locality as the holotype. MZU PL. 270: leg. C. Palacios, 17 November 2006 —copulatory apparatus: sagittal sections on 9 slides; MZU PL. 271: leg. S. M. Oliveira, 10 September 2006 —anterior tip: sagittal sections on 8 slides; anterior region at the level of the ovaries: sagittal sections on 49 slides; pre-pharyngeal region: transverse sections on 15 slides; pharynx: sagittal sections on 15 slides; copulatory apparatus: horizontal sections on 9 slides. MZU PL. 272: leg. M. B. Antunes, 17 November 2006 —anterior tip: preserved in clove oil; copulatory apparatus: sagittal sections on 11 slidesGoogleMaps .
Diagnosis: species of Cratera with dorsal color homogeneously black; pharynx cylindrical with dorsal insertion shifted posteriorly; prostatic vesicle extrabulbar with proximal portion T-shaped and slightly dorsally oriented.
Type-locality: State Park of Turvo, Derrubadas, state of Rio Grande do Sul, Brazil.
Distribution: known only from the type-locality.
Description. External features. Body elongate with parallel margins; anterior tip rounded and posterior tip pointed. While creeping, the largest specimen reached a length of 40 mm. After fixation, maximum length was 38 mm. Mouth and gonopore located at the posterior third of the body ( Table 1). In living specimens, dorsal surface homogeneously black ( Fig. 1View FIGURE 1); venter light gray. After fixation, dorsal color becomes light brown and the ventral surface remains light gray.
Eyes monolobate (with pigment cups of about 15–30 µm) ( Fig. 2View FIGURES 2–8), initially uniserial, surrounding the anterior tip ( Fig. 1View FIGURE 1). After that, the eyes become larger and surrounded by clear halos, spreading onto the dorsal surface, and may occupy the whole body width ( Fig. 1View FIGURE 1). Towards the posterior tip, the eyes remain dorsal but become less numerous.
Sensory organs, epidermis and body musculature. Sensory pits ( Fig. 2View FIGURES 2–8) as simple invaginations (20–30 µm deep) contour anterior tip and occur ventromarginally in one row on each side of the body in the cephalic region (about 7% of the body length).
The creeping sole occupies the whole body width ( Table 1). Three types of glands discharge through whole epidermis of pre-pharyngeal region: rhabditogen glands with xanthophil secretion (ventrally with smaller rhabdites) and cyanophil glands with amorphous secretion, besides scarce xanthophil glands with coarse granular secretion ( Figs. 3, 6View FIGURES 2–8). The glandular margin ( Figs. 3, 4View FIGURES 2–8) is conspicuous after the cephalic region (about 8% of the body length) and receives the openings of two types of glands: xanthophil cells with coarse granular secretion and cyanophil cells with amorphous secretions. Glands discharging through the anterior tip of the body are similar to those of the prepharyngeal region ( Fig. 3View FIGURES 2–8).
Cutaneous musculature with the usual three layers: circular, oblique and longitudinal layers, the latter with thick bundles ( Figs. 5, 6View FIGURES 2–8, Table 2). Cutaneous musculature thinner in the pre-pharyngeal region than in the cephalic region of the body, but gradually diminishing its thickness towards anterior tip. Ventral musculature with similar thickness or slightly thinner than dorsal musculature at the sagittal plane ( Table 2) between four and seven times thicker than the epidermis, becoming progressively thinner toward body margins. Mc:h 7–8% ( Table 2).
Mesenchymal musculature ( Fig. 4View FIGURES 2–8) well developed, with a similar arrangement to that described for other species of the genus. At the cephalic region, the mesenchymal musculature is less developed than in the pre-pharyngeal region.
Pharynx. The pharynx is cylindrical, about 6% of body length, with folded walls and dorsal insertion posteriorly shifted. The mouth is located in the median third of the pharyngeal pouch ( Fig. 7View FIGURES 2–8). Esophagus absent.
Reproductive organs. The testes are arranged in one irregular row on either side of the body, beneath the dorsal transverse mesenchymal muscles ( Figs. 4, 5View FIGURES 2–8). They begin in the anterior third of the body and extend to near the root of the pharynx. Sperm ducts dorsal to ovovitelline ducts in pre-pharyngeal region ( Fig. 6View FIGURES 2–8). Distally, sperm ducts—forming spermiducal vesicles—enter laterally into the proximal part of the prostatic vesicle ( Figs. 9, 10View FIGURES 9–10). Extrabulbar prostatic vesicle, tubular and unpaired, located near the common muscle coat. The proximal portion is laterally expanded (T-shaped) and slightly dorsally oriented ( Figs. 9–12View FIGURES 9–10View FIGURES 11–12); it is located at about the same distance from the ventral and dorsal epidermis. Its distal portion penetrates the common muscle coat, becoming sinuous, and continues inside the penis papilla as an ejaculatory duct. This duct is almost straight and opens through an expansion at the tip of the penis papilla ( Figs. 9View FIGURES 9–10, 11View FIGURES 11–12). The male atrium is almost unfolded and occupied by the conical, almost symmetric penis papilla, which has a dorsal fold. The dorsal wall of the male atrium receives the openings of abundant cyanophil glands ( Figs. 9–12View FIGURES 9–10View FIGURES 11–12). Histological aspects of the epithelium, musculature and secretions of the prostatic vesicle, penis papilla, ejaculatory duct and male atrium are similar to those of other species of Cratera .
Vitelline follicles, situated between intestinal branches, well-developed in all studied specimens ( Figs. 4, 6, 8View FIGURES 2–8). Ovaries ovoid, about twice longer than wide, measuring 0.3 mm in their antero-posterior axis. They are located dorsally to the ventral nerve plate at about the same transversal level as the anteriormost testes, in the anterior third of the body ( Table 1, Fig. 8View FIGURES 2–8). Ovovitelline ducts emerge dorsally from the median third of the ovaries and run posteriorly immediately above the nerve plate. Laterally to the female atrium, the ovovitelline ducts ascend dorsomedially and unite dorsally to the proximal third of the female canal to form the common glandular ovovitelline duct ( Figs. 9–11View FIGURES 9–10View FIGURES 11–12). The female genital duct is dorso-anteriorly curved ( Figs. 9–12View FIGURES 9–10View FIGURES 11–12). The female atrium is funnel-shaped, with small lateral folds, and has about half the length of the male atrium ( Table 1, Figs. 9–12View FIGURES 9–10View FIGURES 11–12). Histological aspects of the epithelium, musculature and secretions of the ovovitelline ducts and female canal and atrium are similar to those of other species of Cratera .
Gonopore canal vertical at the sagittal plane. Male and female atria with ample communication, without separating folds ( Figs. 9–12View FIGURES 9–10View FIGURES 11–12), showing well developed, continuous muscle coats with longitudinal, oblique and circular fibers ( Figs. 11, 12View FIGURES 11–12). The common muscle coat is thicker entally and along the dorsal wall of the male atrium, thinner around the female atrium.
Comparative discussion. The presence of an expanded ejaculatory cavity at the tip of the penis papilla and cyanophil glands discharging through the roof of the male atrium, as well as other characters, such as dorsal monolobated eyes, support the inclusion of Cratera obsidiana in the genus Cratera Carbayo et al., 2013 .
The new species shares similarities with eleven species of the genus, C. hina (Marcus, 1951) , C. crioula (E. M. Froehlich, 1955) , C. joia (Froehlich, 1956) , C. anamariae Carbayo, 2015 , C. ochra Rossi et al., 2015 , C. viridimaculata Negrete & Brusa, 2016 , C. cryptolineata Rossi & Leal-Zanchet, 2016 , C. nigrimarginata Rossi & Leal-Zanchet, 2016 , C. aureomaculata Rossi & Leal-Zanchet, 2016 , C. picuia Lago-Barcia & Carbayo, 2018 and C. arucuia Lago-Barcia & Carbayo, 2018 , showing eyes spreading over the dorsal surface and a cylindrical pharynx ( Froehlich 1954a, 1956b; Carbayo & Almeida 2015; Negrete & Brusa 2016; Rossi et al. 2016; Lago-Barcia & Carbayo 2018). It differs from these species, however, by the color pattern and details of the copulatory apparatus.
The color pattern of C. obsidiana , homogeneously black, differs from that of C. crioula and C. joia as they also have a black dorsum, but with a median light stripe ( Froehlich 1954b, 1956a). It also can be distinguished from C. ochra , which shows a dorsal yellow-ochre ground color and dispersed grayish or grayish-brown pigmentation constituting two broad dorsal bands ( Rossi et al. 2016). The new species also can be distinguished from C. nigrimarginata , which has a light-brownish dorsal color bordered by dark margins, and C. aureomaculata , which shows a yellowish dorsal ground color covered by brownish pigmentation in the cephalic region and blackish pigmentation constituting irregular flecks over the rest of the dorsum ( Rossi & Leal-Zanchet 2017). By having a homogeneously pigmented dorsum, C. obsidiana can be distinguished from species with striped dorsal surface, such as C. anamariae , C. viridimaculata and C. cryptolineata ( Carbayo & Almeida 2015; Negrete & Brusa 2016; Rossi & Leal-Zanchet 2017). The color pattern of C. hina , C. picuia and C. arucuia is distinguished from that of C. obsidiana by the presence of a light central band followed on each side by a wide dark band ( Lago-Barcia & Carbayo 2018).
Regarding the copulatory apparatus, C. obsidiana has a tubular prostatic vesicle with the proximal portion laterally expanded (T-shaped) similar to that of C. steffeni Rossi et al., 2014 and C. ochra ( Rossi et al. 2014, 2016). In all these three species, the prostatic vesicle is considered to be single, without forked portions, since it just shows a lateral expansion. However, C. obsidiana has the proximal portion of the prostatic vesicle slightly dorsally oriented, being such an anatomical feature recorded for the first time in the genus Cratera .
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