Paraba aurantia Marques & Leal-Zanchet, 2022

Marques, Alessandro Damasceno, Hartmann, Alef, Valiati, Victor Hugo & Leal-Zanchet, Ana Maria, 2022, Two new land planarian species (Platyhelminthes: Tricladida) from the Cerrado biome in southwestern Brazil, Zootaxa 5205 (4), pp. 301-330 : 305-313

Paraba aurantia Marques & Leal-Zanchet , sp. nov.

urn:lsid:zoobank.org:act:70C8C653-A1AE-441C-9038-CCD14343232A

Etymology: The specific name is a Latin adjective (aurantius) and refers to the orangish dorsal ground colour.

Type-material. Holotype: MZUSP PL. 2286: leg. J. Peres, 25 October 2019, Bodoquena (municipal leisure area of Bodoquena), state of Mato Grosso do Sul, Brazil —anterior tip: transverse sections on 10 slides; anterior region at the level of the ovaries: sagittal sections on six slides; pre-pharyngeal region: transverse sections on 11 slides; pharynx and copulatory apparatus: sagittal sections on 12 slides.

Paratypes: MZU PL. 00319: leg. A. Marques, 24 May 2019, Bodoquena (municipal leisure area of Bodoquena), state of Mato Grosso do Sul, Brazil —pre-pharyngeal region: transverse sections on six slides; copulatory apparatus: sagittal sections on five slides. MZU PL. 00320: leg. A. Marques, 27 May 2019, Bonito (National Park of Serra da Bodoquena), state of Mato Grosso do Sul, Brazil —anterior tip: transverse sections on two slides; anterior region at the level of the ovaries: sagittal sections on two slides; pre-pharyngeal region: transverse sections on four slides; pharynx and copulatory apparatus: sagittal sections on four slides .

Diagnosis. Species of Paraba showing dorsal surface orangish with a wide black median longitudinal band; eyes spreading onto the dorsal surface, including the cephalic region; glandular margin absent; pharynx cylindrical; oesophagus long; prostatic vesicle extrabulbar, tubular and twisted, consisting of two portions: proximal portion with short asymmetrical branches, and main distal portion unforked, C-shaped; female atrium oval-elongate and with ample lumen lined by a low epithelium with stratified appearance; male and female atria with ample communication.

Type-locality: Bonito, state of Mato Grosso do Sul, Brazil

Distribution: Known only from areas of semideciduous Forest from the municipalities of Bonito and Bodoquena, state of Mato Grosso do Sul, Brazil.

Description

External features. Body elongate with parallel margins, subcylindrical in cross-section; anterior end rounded and posterior end pointed ( Figs. 6–9 ). Maximum length reached 30 mm when creeping and 22 mm after fixation. Mouth at posterior half of body and gonopore at posterior third of body ( Table 1 ).

Alive, dorsum orangish covered by a wide black median band ( Figs. 6–7, 9 ), without reaching the body tips. Ventral surface pale-yellow with orangish body margins; small brownish spots contour the anterior tip ( Figs. 7–8 ). After fixation, dorsal colour fades ( Fig. 9 ); ventral colour remains.

Eyes, uniserially arranged and monolobate (with pigment cups 16–22 μm in diameter), surround the anterior tip. After that, these monolobate eyes remain along the body margins, whereas bilobate eyes (with pigment cups of 14–22 μm in diameter) spread onto almost the whole dorsal surface of the body, including the dorsal surface of the cephalic region of the body ( Figs. 10–12 ). Towards the posterior end, eyes gradually become slightly sparser. Clear halos surround the dorsal eyes in the holotype, being inconspicuous in paratype MZU PL. 00320.

Sensory organs, epidermis and body musculatures. Sensory pits ( Figs. 13–14 ), as simple invaginations (about 22–30 µm), contour anterior tip and occur ventromarginally in an irregular, single row in the first 3 mm of the body (approximately 13% of body length, in the paratype MZU PL. 00320). Creeping sole occupies the entire body width ( Table 2 ) in pre-pharyngeal region.

Three types of glands discharge through whole epidermis of pre-pharyngeal region ( Figs. 15–16 ): numerous rhabditogen glands with xanthophil secretion, xanthophil glands with finely granular secretion and cyanophil glands with amorphous secretion. Rhabditogen glands are scarce and show small rhabdites in the creeping sole. There is no glandular margin. Glands discharging through the anterior tip of the body are similar to those of the pre-pharyngeal region.

Cutaneous musculature with the usual three layers in Geoplaninae (circular, oblique and longitudinal), with longitudinal layer organized in thick discrete bundles ( Figs. 15–18 ). Musculature slightly thicker medially than laterally, becoming progressively thinner towards body margins. Ventral musculature with similar thickness as the dorsal musculature in the holotype and paratype MZU PL. 00319 and slightly thicker than the dorsal musculature in paratype MZU PL. 00320 ( Table 2 ). In cephalic region, cutaneous musculature similar to that of pre-pharyngeal region, gradually diminishing in thickness towards the anterior tip. Mc:h varying between, approximately, 8% and 9% ( Table 2 ).

Mesenchymal musculature ( Figs. 15–18 ) poorly developed, mainly composed of three layers: (1) dorsal subcutaneous decussate oblique muscles (about 6 fibres thick), located close to the cutaneous longitudinal muscle bundles; (2) supra-intestinal transverse muscles (about 8 fibres thick); and (3) sub-intestinal transverse muscles (about 6 fibres thick). In addition, there are scattered dorsoventral fibres and ventral subcutaneous oblique fibres. The mesenchymal musculature of the cephalic region ( Fig. 13 ) is slightly less developed than in the pre-pharyngeal region.

Pharynx. Pharynx cylindrical, about 7% of body length, with folded walls and dorsal insertion slightly displaced posteriorly with respect to the ventral insertion, located in the anterior third of the pharyngeal pouch ( Fig. 19 ). The pharynx occupies about 96% of the pharyngeal pouch. Mouth located in the median third of the pharyngeal pouch. Oesophagus long; oesophagus:pharynx ratio 25%.

Pharynx and pharyngeal lumen lined by ciliated, columnar epithelium with insunk nuclei. Pharyngeal glands constituted by three gland types: numerous xanthophil glands with coarse granules and cyanophil glands with fine granules, as well as less numerous erythrophil glands with coarse granules. Outer pharyngeal musculature (7–10 µm thick) comprised of a subepithelial layer of longitudinal fibres, followed by a circular layer. Inner pharyngeal musculature (12–50 µm thick) composed of a thick subepithelial layer with circular fibres, mixed with a few longitudinal. Both musculatures become thinner towards pharyngeal tip.

Reproductive organs. Testes arranged uniserially on either side of the body and located beneath the dorsal transverse mesenchymal muscles and between intestinal branches ( Figs. 15, 18 ). They arise slightly anterior to the ovaries, in the anterior third of the body, and extend to near the root of the pharynx ( Table 1 ). Sperm ducts dorso-lateral to ovovitelline ducts in the pre-pharyngeal region ( Figs. 15, 18 ). They form spermiducal vesicles laterally to the pharynx. Distally, spermiducal vesicles extend to the penis bulb, recurve anteriorly, being slightly asymmetrical as they approach and open into the proximal forked parts of the prostatic vesicle ( Figs. 20–21 , 23–24 ). Prostatic vesicle extrabulbar, tubular and twisted, consisting of two portions: proximal region with short, slightly asymmetrical branches, oriented obliquely and located ventrally to the main portion; main distal portion unforked and C-shaped ( Figs. 20–24 ). The main portion of the prostatic vesicle narrows before entering the common muscle coat and becomes slightly sinuous inside the penis bulb. Ejaculatory duct almost straight, opening at the tip of the penis papilla. Penis papilla of protrusible type conical and symmetrical, occupying almost the whole male atrium ( Figs. 20–23 ).

Sperm ducts lined with ciliated, cuboidal epithelium and coated with a thin muscularis (2–8 µm thick) constituted mainly by circular fibres. Prostatic vesicle lined with ciliated, columnar epithelium. Muscle coat of prostatic vesicle (22–37 µm thick) comprises longitudinal, circular and oblique intermingled fibres. Numerous glands with finely granular erythrophil secretions of two types, one with loosely arranged granules and the other with densely arranged granules, open into the prostatic vesicle. Ejaculatory duct lined with ciliated, columnar epithelium, receiving amorphous, slightly cyanophil secretion. This duct is coated mainly with circular muscle fibres (10–30 µm thick).

Penis papilla and male atrium lined with non-ciliated, cuboidal to columnar epithelium with abundant openings of erythrophil glands with coarsely granular secretion, besides cyanophil glands with finely granular secretion. In addition, xanthophil glands with coarsely granular secretion open through the lining epithelium of the penis papilla. Erythrophil glands scarcer in the male atrium walls. Muscularis of penis papilla and male atrium (5–15 µm thick) constituted of a subepithelial circular layer followed by a subjacent longitudinal layer.

Vitellaria well developed in the holotype, less developed in other specimens, situated between intestinal branches. Ovaries oval-elongate, approximately three times longer than wide, measuring 0.2–0.3 mm in the anteroposterior axis. They are located dorsal to the ventral nerve plate, in the anterior third of the body ( Table 2 ; Figs. 15, 17 ). Ovovitelline ducts emerge dorsally from the anterior end of the ovaries and run posteriorly immediately above the nerve plate ( Figs. 15, 17 ). Ascending portion of the ovovitelline ducts located laterally to the gonopore ( Figs. 20–21 ). Common glandular ovovitelline duct short (about 60 µm in length), located dorsally to the female atrium, entering the common muscle coat in a postflex posterior approach, to open into the ental portion of the female canal ( Figs. 20–22 , 25 ). The female genital duct is a dorso-anteriorly curved diverticulum of the female atrium ( Figs. 20–22 ). Female atrium oval-elongate, with ample lumen, narrowing laterally. Male and female atria show ample communication in the holotype, but folds protrude from the dorsal and ventral walls of these atria, partially separating them, in paratype MZU PL. 00320, which seems to be contracted ( Figs. 20–23 ). Female atrium almost as long as male atrium ( Table 1 ).

Ovovitelline ducts and common ovovitelline duct lined with ciliated, cuboidal epithelium, covered with intermingled circular and longitudinal muscle fibres. Shell glands with erythrophil secretion empty into the common glandular ovovitelline duct as well as into the distal section of the ovovitelline ducts ( Figs. 20–22 , 25–26 ). The female canal and the distal portion of the female atrium are lined by a ciliated epithelium with pseudostratified appearance, whereas the proximal portion of the female atrium is lined by an epithelium with stratified appearance ( Figs. 20–23 , 25–27 ), which is low (10–30 µm high). Three types of secretory cells open through the epithelium of the female atrium and canal: cyanophil glands with finely granular secretion, cyanophil glands with coarsely granular secretion and sparser erythrophil glands with finely granular secretion. Muscularis of the female canal (10–30 µm) thicker than that of the female atrium (10–27 µm), both of them comprised of a thin layer of circular fibres followed by a layer of interwoven circular and longitudinal fibres.

Gonoduct vertical at the sagittal plane ( Figs. 20–22 , 24, 26 ), lined with ciliated, columnar epithelium and coated with a subepithelial layer of circular fibres, followed by a layer of longitudinal fibres. Common muscle coat thin, with circular, longitudinal and oblique intermingled fibres.

Comparative discussion. Paraba aurantia Marques & Leal-Zanchet , sp. nov. shows the diagnostic characteristics of the genus, such as cylindrical pharynx, penis papilla protrusible and conical and female atrium lined with epithelium of multi-layered aspect ( Carbayo et al. 2013).

The new species has eyes spreading over the dorsum and a forked prostatic vesicle, a combination of characteristics that is found in four other species of this genus, namely Paraba caapora ( Froehlich, 1958) , P. gaucha ( Froehlich, 1959) , P. multicolor (Graff, 1899) and P. pankaru Amaral & Leal-Zanchet, 2019 ( Froehlich 1958; 1959; Negrete & Brusa 2017; Amaral et al. 2019). Thus, in the following comparative discussion, we discuss P. aurantia in relation to these four species.

With an orangish dorsum covered by a single and wide black median band, P. aurantia differs from P. caapora , which has a light-brown dorsum with dark patches ( Froehlich 1958). The new species also differs from P. gaucha and P. multicolor , which show various longitudinal stripes and/or bands, as well as from P. pankaru that has a black dorsum with a yellowish transverse band ( Froehlich 1959; Negrete & Brusa 2017; Amaral et al. 2019). In addition, P. aurantia has eyes spreading onto the dorsal surface of the body, including the cephalic region, a characteristic that is seldom found in Geoplaninae .

Regarding the copulatory apparatus, P. aurantia shows a tubular and twisted prostatic vesicle with a C-shaped distal portion and short, slightly asymmetrical proximal branches. Therefore, it can be differentiated from P. caapora , P. multicolor and P. gaucha , which have the distal portion of the prostatic vesicle almost straight ( Froehlich 1958, 1959; Negrete & Brusa 2017). Besides, the proximal portions are large and globular in P. caapora and P. multicolor , differing from the short branches in P. aurantia . In contrast, P. pankaru has a prostatic vesicle with a more twisted distal portion ( Amaral et al. 2019), showing an ampler lumen in comparison to P. aurantia . In addition, P. aurantia shows a female atrium with ample lumen, lined by a pseudostratified epithelium in its distal and median thirds and an epithelium with multi-layered appearance in the proximal portion of the atrium, which is lower than in other species of Paraba . In contrast, other species of this genus shows a female atrium with narrow lumen, which is lined by a tall epithelium with a multi-layered aspect in some species, such as P. multicolor and P. pankaru , at least in the proximal third or half of the female atrium, whereas most species show almost the entire atrium with this lining, narrowing the lumen of this atrium.

Figures

FIGURE 19. Paraba aurantia Marques & Leal-Zanchet, sp. nov., paratype MZU PL. 00320: microphotograph of a sagittal section of the pharynx. Anterior tip to the left.

FIGURES 6–9. Paraba aurantia Marques & Leal-Zanchet, sp. nov.: (6–7) photographs of the paratype MZU PL. 00320, in dorsal view, before fixation; (8) photograph of the anterior body region of the preserved paratype MZU PL. 00319 in ventral view; (9) photograph of the preserved holotype in dorsal view.Anterior tip to the left. Scale bars: (6–7) 5 mm; (8–9) 1 mm. The arrow indicates the ventral surface, which is partially visible in (7). The arrowheads indicate the brownish spots in the ventral surface in (8).

FIGURES 10–12. Paraba aurantia Marques & Leal-Zanchet, sp. nov.: (10–11) detail of the eye pattern in the cephalic region in paratypes MZU PL. 00320 (10) and MZU PL. 00319 (11); (12) eye pattern of the holotype. Anterior tip to the left.

FIGURES 13–18. Paraba aurantia Marques & Leal-Zanchet, sp. nov., paratype MZU PL. 00320, microphotographs of transverse sections: (13–14) cephalic region of body; (15–18) anterior region of body at the level of ovaries.

FIGURES 20–21. Paraba aurantia Marques & Leal-Zanchet, sp. nov., sagittal composite reconstructions of the copulatory apparatus of the holotype (20) and paratype MZU PL. 00320 (21). Anterior tip to the left.

FIGURES 22–23. Paraba aurantia Marques & Leal-Zanchet, sp. nov., microphotographs of the copulatory apparatus in sagittal sections: (22) holotype; (23) paratype MZU PL. 00320. Anterior tip to the left.

FIGURES 24–27. Paraba aurantia Marques & Leal-Zanchet, sp. nov., microphotographs of the copulatory apparatus in sagittal sections: (24–25) paratype MZU PL. 00320, details of the prostatic vesicle and female canal; (26–27) holotype, details of the female organs. Anterior tip to the left. The arrows indicate the epithelium with a multilayered aspect of the female atrium in (27).